MX2014008251A - Hydrogenation catalysts with acidic sites comprising modified silica support. - Google Patents

Abstract

The present invention relates to catalysts. The catalysts are preferably used for converting acetic acid to ethanol. The catalyst comprises a precious metal and at least one active metal on a modified silica support. The catalyst has acidic sites on the surface and the balance favors Lewis acid sites.

Description

HYDROGENATION CATALYSTS WITH ACID SITES THAT UNDERSTAND MODIFIED SILICA SUPPORT CROSS REFERENCE TO RELATED REQUEST This application claims priority to the US Application. No. 13 / 595,365, filed on August 27, 2012, which claims priority to the US Provisional Application. No. 61 / 583,874, filed January 6, 2012. This application also claims priority to the US Application. No. 13 / 595,358, filed on August 27, 2012, which claims priority to the US Provisional Application. No. 61 / 583,922, filed January 6, 2012. This application additionally claims priority to the US Application. No. 13 / 595,340, filed on August 27, 2012, which also claims priority to the US Provisional Application. No. 61 / 583,874, filed January 6, 2012. The complete contents and disclosures of the foregoing applications are incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to hydrogenation catalysts having acid sites, and to processes for producing ethanol from raw material comprising a carboxylic acid and / or esters thereof in the presence of the inventive catalysts. In particular, The present invention relates to a hydrogenation catalyst having acid sites, wherein at least 70% of the acid sites are Lewis acid sites, measured by means of infrared Fourier transform pyridine chemisorbed (FTIR) spectroscopy.

BACKGROUND OF THE INVENTION Ethanol for industrial use is conventionally produced from petrochemical raw materials such as petroleum, natural gas or coal, from raw material intermediaries as synthesis gas or from starchy materials or cellulosic materials such as corn or sugarcane. Conventional methods for producing ethanol from petrochemical raw materials, as well as from cellulosic materials, include ethylene acid catalyzed hydration, methanol homologation, direct alcohol synthesis and Fischer-Tropsch synthesis. The instability in the prices of the petrochemical raw material contributes to fluctuations in the cost of conventionally produced ethanol, which makes the need for alternative sources of ethanol production greater when the prices of the raw material rise. The amylaceous materials, as well as the cellulosic material, are converted to ethanol by means of fermentation. However, fermentation is typically used for the production of ethanol for consumption, which is appropriate for fuels or for human consumption. In addition, the fermentation of starchy or cellulose materials competes with food sources and places limitations on the amount of ethanol that can be produced for industrial use.

The production of ethanol by means of the reduction of alkanoic acids and / or other compounds containing carbonyl groups has been studied extensively, and a variety of combinations of catalysts, supports, and operating conditions have been mentioned in the literature. The reduction of various carboxylic acids over metal oxides has been proposed by EP0175558 and U.S. Pat. No. 4,398,039. A summary of some of the efforts of the development of hydrogenation catalysts for the conversion of various carboxylic acids is given in Yokoyama, et al., "Carboxylic Acids and Derivatives" in: Fine Chemicals Through Heterogeneous Catalysis, 2001, 370-379.

U.S. Pat. No. 8,080,694 describes a process for hydrogenating alkanoic acids comprising passing a gas stream comprising hydrogen and an alkanoic acid in the vapor phase over a hydrogenation catalyst comprising: a metal of the platinum group selected from the group consisting of platinum, palladium, rhenium and mixtures thereof on a siliceous support; and a metal promoter selected from the group consisting of tin, rhenium and mixtures thereof, the siliceous support being promoted with a redox promoter selected from the group consisting of: W03; Mo03; Fe2O3 and Cr203.

U.S. Pat. No. 7,608,744 discloses a process for the selective production of ethanol by reaction in the vapor phase of acetic acid at a temperature of about 250 ° C on a hydrogenation catalyst composition either cobalt and palladium supported on graphite or cobalt and platinum supported on silica which selectively produces ethanol.

U.S. Pat. No. 6,495,730 describes a process for hydrogenating carboxylic acid using a catalyst comprising activated carbon to support the active metal species comprising ruthenium and tin. U.S. Pat. No. 6,204,417 describes another process for the preparation of aliphatic alcohols by means of the hydrogenation of aliphatic carboxylic acids or anhydrides or esters thereof or lactones in the presence of a catalyst comprising Pt and Re. No. 5,149,680 describes a process for the catalytic hydrogenation of carboxylic acids and their anhydrides to alcohols and / or esters in the presence of a catalyst containing a Group VIII metal such as palladium, a metal capable of alloying with the Group VIII metal, and at least one of the rhenium, tungsten or molybdenum metals. U.S. Pat. No. 4,777,303 discloses a process for the production of alcohols by hydrogenation of carboxylic acids in the presence of a catalyst comprising a first component that is molybdenum or tungsten and a second component that is a noble metal of Group VIII on a graphitized carbon of high surface area. U.S. Pat. No. 4,804,791 describes another process for the production of alcohols by means of the hydrogenation of carboxylic acids in the presence of a catalyst comprising a noble metal of Group VIII and rhenium. U.S. Pat. No. 4,517,391 describes preparing ethanol by hydrogenating acetic acid under super-atmospheric pressure and at elevated temperatures by means of a process using a catalyst containing predominantly cobalt.

Existing procedures suffer from a variety of problems that impede commercial viability including: (i) catalysts without required selectivity to ethanol; (ii) catalysts that are possibly prohibitively expensive and / or non-selective for the formation of ethanol and that produce undesirable byproducts; (iii) required operating temperatures and pressures that are excessive; (iv) insufficient life of the catalyst; and / or (v) activity required for both ethyl acetate and acetic acid with decreased formation of by-products.

BRIEF DESCRIPTION OF THE INVENTION In a first embodiment, the present invention is directed to a hydrogenation catalyst comprising a precious metal and at least one active metal on a modified silica support, wherein the catalyst has at least 70% Lewis acid sites based on the total number of acid sites measured by infrared Fourier transform pyridine chemisorbed (FTIR) spectroscopy, and wherein the modified silica support comprises: (i) a support material; and (ii) a modifier of support comprising a metal selected from the group consisting of tungsten, molybdenum, vanadium, niobium and tantalum. The catalyst can have at least 80% Lewis acid sites, based on the total number of acid sites, as measured by FTIR. The modified silica support can comprise cobalt tungstate. The precious metal can be selected from the group consisting of rhodium, rhenium, ruthenium, platinum, palladium, osmium, iridium and gold. The at least one active metal can be selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. The catalyst can be prepared by: (a) impregnating a support material with a first solution to form a first impregnated support, wherein the first solution comprises a precursor of the support modifier metal selected from the group consisting of tungsten, molybdenum, niobium, vanadium and tantalum; (b) calcining the first impregnated support to form a modified silica support; (c) impregnating the modified silica support with a second solution to form a second impregnated support, wherein the second solution comprises a precious metal precursor, and a precursor of at least one active metal; and (d) calcining the second impregnated support to form the catalyst. The first solution may further comprise a precursor of at least one active metal selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. the same. The precursor of at least one active metal in the first solution may be the same precursor of at least one active metal in the second solution. The support material may not have acidic acid sites before impregnated with the first solution. The modified silica support can have at least 50% Lewis acid sites, based on the total number of acid sites, measured by means of infrared Fourier transform pyridine chemisorbed spectroscopy, or at least 60%.

In a second embodiment, the present invention is directed to a process for producing ethanol, which comprises contacting a raw material comprising hydrogen and acetic acid and / or ethyl acetate in a reactor at elevated temperature in the presence of the catalyst of the claim 1, under effective conditions to form ethanol. The raw material can also comprise more than 5% by weight of ethyl acetate. The raw material may further comprise ethyl acetate in an amount greater than 0% by weight, wherein the conversion of acetic acid is greater than 20% and the conversion of ethyl acetate is greater than 5%. The selectivity of diethyl ether may be less than 1%, including the selectivity of acetic acid to diethyl ether and the selectivity of ethyl acetate to diethyl ether. The acetic acid can be formed from methanol and carbon monoxide, wherein each of the methanol, carbon monoxide and hydrogen for the hydrogenation step is derived from synthesis gas, and wherein the synthesis gas is derived from a carbon source selected from the group consisting of natural gas, oil, petroleum, coal, biomass, and combinations thereof.

In a third embodiment, the present invention is directed to a hydrogenation catalyst comprising a modified silica support, and n metals, wherein n is from 2 to 6, and the metals are selected from the group consisting of rhodium, rhenium, ruthenium , platinum, palladium, osmium, iridium, copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, tin, lanthanum, cerium, cobalt, manganese, and oxides thereof, in where the hydrogenation catalyst has at least 70% Lewis acid sites, based on the percentage of all acid sites, as measured by FTIR of chemisorbed pyridine. In some embodiments, n is 3. The modified silica support can comprise a silica support, a support modifier and at least one active metal. The support modifier can be selected from the group consisting of tungsten, molybdenum, niobium, vanadium and tantalum. The at least one active metal can be selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. The catalyst can be prepared by: (a) impregnating a support material with a first solution to form a first impregnated support, wherein the first solution comprises a precursor of a supporting modifier metal selected from the group consisting of tungsten, molybdenum, niobium , vanadium and tantalum; (b) calcining the first impregnated support to form a modified silica support; (c) impregnating the modified silica support with a second solution to form a second impregnated support, wherein the second solution it comprises a precursor of each of the at least one precious metal, and (d) calcining the second impregnated support to form the catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS The invention can be more fully understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying figures.

Figure 1 shows an FTIR spectrum according to an embodiment of the present invention.

Figure 2 shows an FTIR spectrum according to an embodiment of the present invention.

Figure 3 shows an FTIR spectrum according to an embodiment of the present invention.

Figure 4 shows an FTIR spectrum according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Catalyst composition The present invention is directed to catalyst compositions which are preferably suitable as hydrogenation catalysts, to processes for forming such catalysts and to chemical procedures that employ such catalysts. The catalyst may be suitable for catalyzing the hydrogenation of a carboxylic acid, for example, acetic acid and / or esters thereof, for example, ethyl acetate, to the corresponding alcohol, for example, ethanol. The catalysts preferably have a surface acidity where most of the acid sites are Lewis acid sites. The balance of Lewis acid sites with Bransted acid sites should favor Lewis acid and lead to fewer Brønsted acid sites. For purposes of the present invention, acid sites on the surface of the catalyst are determined by infrared spectroscopy, in particular, Fourier Transformed Infrared Spectroscopy (FTIR). Unless otherwise indicated by the context, the acidity of a surface or the number of acid sites thereon can be determined by the technique described in F. Delannay, Ed., "Characterization of Heterogeneous Catalysts"; Chapter III: Measurement of Acidity of Surfaces, p. 370-404; Marcel Dekker, Inc., N.Y. 1984. Ammonia or pyridine can be used as the base, and it is preferred to use pyridine to determine surface acidity. In one embodiment, at least 70% of the acid sites on the catalyst surface are Lewis acid sites, for example, at least 80% or at least 85%. In some embodiments, 100% of the acid sites may be Lewis acid sites. In other embodiments, the percentage of Lewis acid sites can vary from 56% to 100%, for example, from 66% to 100%.

Surprisingly and unexpectedly, the acid sites on the Catalyst, specifically Lewis acid sites, can be at least partially responsible for an increase in the conversion and selectivity to ethanol when a catalyst is used for the hydrogenation of a carboxylic acid and / or esters thereof. In particular, the Lewis acid sites may be useful to promote the conversion of ethyl acetate to ethanol. This is particularly advantageous when mixed feeds of acetic acid and ethyl acetate are introduced into the hydrogenation reactor. Without being limited by theory, it is believed that the increase of the Lewis acid sites in relation to the Bronsted acid sites reduces certain impurities such as diethyl ether. Diethyl ether is an impurity that needs to be removed from ethanol that increases the costs of purification. Diethyl ether is not easily converted to ethanol and reduces the productivity of the raw material.

The catalysts preferably comprise a modified silica support, for example, a modified silica support having acid sites. The support material, i.e., silica, generally has no acid sites. Acid sites can be introduced into the silica when a support modifier is added, as is further described herein. In some embodiments, the modified silica support has at least 50% Lewis acid sites, for example, at least 60%. In terms of ranges, the modified silica support may comprise from 50 to 80% of Lewis acid sites. When the support modifier is added to the silica, it is difficult to achieve the desired balance of Lewis acid sites with Bronsted acid sites. Additionally, because the modified silica support is not catalytically active for hydrogenation of acetic acid and / or ethyl acetate to ethanol, one or more active metals, including precious metals, need to be added. Depending on the active metal, this can change the balance of Lewis acid sites with Bronsted acid sites. Preferably, the active metals are added to favor a majority of Lewis acid sites on the surface of the catalyst. Active metals can i) increase the number of Lewis acid sites; ii) blocking or suppressing the availability of Bronsted acid sites by means of amphoteric materials such as tin oxides; iii) block or delete the total number of acid sites; or iv) combinations thereof. In particular it has been found that tin, as an active metal, is particularly useful for achieving a favorable balance of Lewis acid sites.

Support Modifiers To form the modified silica support, a support modifier and support material is added. A support modifier can adjust the acidity of the support material by forming a plurality of acidic sites on the surface of the support. These acid sites can be Lewis acid sites, Bronsted acid sites and combinations thereof. The relative balance of Lewis acid sites with Bronsted acid sites can vary on the modified silica support. Thus, in one embodiment, the support modifier can form more acid sites of Bronsted in relation to the Lewis acid sites. After the active metals are added, it is preferred that the catalyst comprises more Lewis acid sites relative to the Bronsted acid sites.

In one embodiment, a support modifier comprises a metal selected from the group consisting of tungsten, molybdenum, vanadium, niobium and tantalum. The metal for the support modifier may be an oxide thereof. In one embodiment, support modifiers are present in an amount of 0.1% by weight to 50% by weight, eg, from 0.2% by weight to 25% by weight, 0.5% by weight to 20% by weight, or from 1% by weight to 15% by weight, based on the total weight of the catalyst. When the support modifier comprises tungsten, molybdenum, and vanadium, the support modifier may be present in an amount of 0.1 to 40% by weight, for example 0.1 to 30% by weight or 0.1 to 20% by weight, with based on the total weight of the catalyst.

As indicated, the support modifier can adjust the acidity of the support. For example, acid sites, for example, Bronsted acid sites or Lewis acid sites, on the support material can be adjusted by means of the support modifier. The acidity of the support material can be adjusted by optimizing the surface acidity of the support material. The support material can also be adjusted by having the support modifier change the pKa of the support material. Unless otherwise indicated by the context, the acidity of a surface or the number of acid sites on it can be determined by the technique described in F. Delannay, Ed., "Characterization of Heterogeneous Catalysts"; Chapter III: Measurement of Acidity of Surfaces, p. 370-404; Marcel Dekker, Inc., N.Y. 1984, the entirety of which is hereby incorporated by reference.

In some embodiments, the support modifier may be an acid modifier that increases the acidity of the catalyst, forming acid sites on a support material that lacks acid sites, such as silica. Suitable acid support modifiers can be selected from the group consisting of: Group IVB metal oxides, Group VB metal oxides, Group VIB metal oxides, Group VIII metal oxides, Group VIII metal oxides, Oxides of aluminum, and mixtures thereof. In one embodiment, the support modifier comprises a metal selected from the group consisting of tungsten, molybdenum, vanadium, niobium and tantalum. In a preferred embodiment, the support modifier comprises a metal selected from the group consisting of tungsten, vanadium, and tantalum. Additionally, the support modifier preferably does not comprise phosphorus and is not made from a phosphorus-containing precursor.

In some embodiment, the acid modifier may also include those selected from the group consisting of WO3, M0O3, V2O5, V02, V2O3, Nb205, Ta205, and Bi203. The reduced oxides of tungsten or molybdenum oxides can also be used, as, for example, one or more of W20O58, W02, W490i19, W50C 48, W18049, Mo9026, Mo8023, ?? 5 ?? 4, ??? 70 7 , Mo4On, or Mo02. The tungsten oxide can be cubic tungsten oxide (H05WO3). In one embodiment, the use of said metal oxide support modifiers in combination with a precious metal and at least one active metal can result in catalysts having multifunctionality, and which may be suitable for converting a carboxylic acid, such as acetic acid, in one or more hydrogenation products, such as ethanol, under hydrogenation conditions.

In other embodiments, the acid support modifiers include those selected from the group consisting of Zr02, Nb205, Ta205, Al203, B203, P2O5, and Sb203. Acid support modifiers include those selected from the group consisting of Zr02, Nb205, Ta205, and AI2O3. In addition to the support modifier, the modified silica support can also comprise at least one active metal. The at least one active metal can be selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. In some embodiments, the at least one active metal can be cobalt and tin. The modified silica support can comprise from 0.5 to 20% by weight of cobalt, for example, from 1 to 15% by weight or from 1.5 to 10% by weight and from 0.5 to 20% by weight of tin, for example, from 1 to 15% by weight or 1.5 to 10% by weight.

In some embodiments, the acid support modifier comprises a mixed metal oxide comprising at least one of the active metals and an anion oxide of a metal of group IVB, VB, VIB, VIII, such as tungsten, molybdenum, vanadium, niobium or tantalum. The oxide anion, for example, may be in the form of a tungstate, molybdate, vanadate or niobate. Exemplary mixed metal oxides include cobalt tungstate, cobalt molybdate, cobalt vanadate, cobalt niobate and / or cobalt emicellu. In one embodiment, the catalyst does not comprise and is substantially free of tin tungstate. Catalysts containing said mixed metal support modifiers can provide the desired degree of multifunctionality in increased conversion, for example, increased ester conversion. The reduction in the Bronsted acid sites may also contribute to a decrease in the formation of by-products, and in particular the formation of diethyl ether.

In some embodiments, the modified silica support comprises at least one active metal, in addition to one or more acid modifiers. The modified silica support can, for example, comprise at least one active metal selected from copper, iron, cobalt, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium and manganese. For example, the support can comprise an active metal, preferably not a precious metal, and an acidic or basic support modifier. Preferably, the support modifier comprises a supporting modifier metal selected from the group consisting of tungsten, molybdenum, vanadium, niobium and tantalum. In this aspect, the final catalyst composition comprises a precious metal and at least one active metal arranged on the modified silica support. In a preferred embodiment, at least one of the active metals in the modified silica support is the same as at least one of the active metals disposed on the support material. For example, the catalyst may comprise a support material modified with cobalt, tin and tungsten (optionally as WÜ3, H0.5WO3, HWO4, and / or as cobalt tungstate). In this example, the catalyst further comprises a precious metal, for example, palladium, platinum or rhodium, and at least one active metal, for example, cobalt and / or tin, disposed on the modified silica support.

Without being limited by theory, it is believed that the presence of cobalt tungstate on the modified silica support or catalyst tends to decrease the Bronsted acid sites, as compared to a support modified only with tungsten oxide. When used on the modified silica support, the tin oxides further reduce the Bronsted acid sites due to the amphoteric properties.

Support Materials The catalysts of the present invention comprise a suitable support material, preferably a modified silica support. In one embodiment, the support material can be silica, including pyrogenic silica or high purity silica. Generally silica does not contain acidic sites and a support modifier is needed for acidic aggregate sites. In other modalities, the support material may be silica / alumina that may contain some acidic sites. In one embodiment the support material is substantially free of alkaline earth metals, such as magnesium and calcium. The support material is present in an amount of 25% by weight to 99% by weight, 30% by weight to 98% by weight or 35% by weight to 95% by weight based on the total weight of the catalyst.

In preferred embodiments, the support material comprises silica having a surface area of at least 50 m2 / g, for example, at least 100 m2 / g, or at least 150 m2 / g. In terms of ranges, the support material preferably has a surface area of 50 to 600 m2 / g. For purposes of the present specification, the surface area refers to the nitrogen surface area of BET, which means the surface area determined by means of ASTM D6556-04, the entirety of which is incorporated herein by reference.

The preferred support material also preferably has an average pore diameter of 5 to 100 nm, for example, 5 to 30 nm, 5 to 25 nm or 5 to 10 nm, determined by means of mercury intrusion porosimetry, and an average pore volume of 0.5 to 2.0 cm3 / g, for example, 0.7 to 1.5 cm3 / g or 0.8 to 1.3 cm3 / g, determined by means of mercury intrusion porosimetry.

The morphology of the support material, and hence the composition of the resulting catalyst, can vary widely. In some exemplary embodiments, the morphology of the support material and / or the catalyst composition may be pellets, extruded materials, spheres, sprinkle-dried microspheres, rings, pentanillos, trilobes, quadrilobes, multiple-lobed shapes, or flakes, although cylindrical pellets are preferred. Preferably, the support material has a morphology that allows a packing density of 0.1 to 1.0 g / cm 3, for example, 0.2 to 0.9 g / cm 3 or 0.3 to 0.8 g / cm 3. In terms of size, the support material preferably has an average particle size, which means the average diameter of the spherical particles or the longest average dimension for non-spherical particles, from 0.01 to 1.0 cm, for example, from 0.1 to 0.7 cm or 0.2 to 0.5 cm. Because the precious metal and the cobalt and / or tin which are disposed on the support generally have the form of very small metal particles (or metal oxide) or crystallites in relation to the size of the support, substantially these metals should not have no impact on the size of the general catalyst particles. Thus, the above particle sizes generally apply both to the size of the modified silica support and to the final catalyst particles, although the catalyst particles are preferably processed to form larger catalyst particles, eg, exempted to form pellets of catalyst.

Active metals The catalyst comprises one or more active metals on the modified silica support. Once the active metals are added to the modified silica support, most acid sites are acid sites of Lewis as discussed in the present. The active metals can be selected from the group consisting of rhodium, rhenium, ruthenium, platinum, palladium, osmium, iridium, nickel, titanium, zinc, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, tin, lanthanum, cerium, cobalt , manganese and oxides thereof. Preferably, there are combinations of at least two, or at least three of the active metals. The number of active metals can vary from 2 to 6, but additional active metals can also be included. In one embodiment, the active metals can be selected from the group consisting of rhodium, rhenium, ruthenium, platinum, palladium, osmium, iridium, nickel, titanium, zinc, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, tin, lanthanum. , cerium, cobalt, manganese and oxides thereof, provided that at least two of the two or more metals include platinum, palladium, molybdenum, tungsten, tin, cobalt and oxides thereof.

The total weight of all active metals, including the above-mentioned precious metal, present in the catalyst is preferably from 0.1 to 25% by weight, for example from 0.5 to 15% by weight, or from 1.0 to 10% by weight. In one embodiment, the catalyst may comprise cobalt in an amount of 0.5 to 20% by weight and tin in an amount of 0.5 to 20% by weight. The active metals, for purposes of the present invention, can be disposed on the modified silica support. For purposes of the present specification, unless otherwise indicated, the percentage by weight is based on the total weight of the catalyst including metal and support.

In one embodiment, the active metals can include at least one precious metal selected from the group consisting of rhodium, rhenium, ruthenium, platinum, palladium, osmium, iridium, gold and oxides or combinations thereof. In terms of ranges, the catalyst may comprise the precious metal in an amount of 0.05 to 10% by weight, for example, 0.1 to 5% by weight, or 0.1 to 3% by weight, based on the total weight of the catalyst . In certain embodiments, the metal loading of the precious metal may be less than the metal charges of the one or more active metals. When a precious metal is used, the other active metal or oxides thereof may be selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof.

Preferred bimetallic combinations (precious metal + active metal) for some exemplary catalyst compositions include platinum / tin, platinum / ruthenium, platinum / rhenium, platinum / nickel, palladium / ruthenium, palladium / rhenium, palladium / copper, palladium / nickel, gold / palladium, ruthenium / rhenium, ruthenium / iron, rhodium / iron, rhodium / nickel and rhodium / tin. In some embodiments, the catalyst comprises three metals in a support, for example, a precious metal and two active metals. Exemplary tertiary combinations may include palladium / rhenium / tin, palladium / rhenium / nickel, platinum / tin / palladium, platinum / tin / rhodium, platinum / tin / gold, platinum / tin / iridium, platinum / tin / copper, platinum / tin / chrome, platinum / tin / zinc, platinum / tin / nickel, rhodium / nickel / tin and rhodium / iron / tin.

In one embodiment, the catalyst comprises from 0.25 to 1.25% by weight of platinum and from 1 to 5% by weight of tin on a modified silica support. The support material comprises silica or silica-aluminum. The cobalt is arranged on the support material together with a support modifier. The modified silica support can comprise from 5 to 15% by weight of acid support modifiers, such as W03, V205 and / or Mo03. In one embodiment, the acid modifier may comprise cobalt tungstate, for example, in an amount of 0.1 to 20% by weight, or 5 to 15% by weight. At least 85% of the acid sites on the support are Lewis acid sites.

In another embodiment, the catalyst comprises from 0.25 to 2.5% by weight of platinum, and from 1 to 5% by weight of tin on a modified silica support. The support material comprises silica or silica-alumina. The cobalt and / or the tin are disposed on the support material together with a support modifier. The modified silica support can comprise from 5 to 15% by weight of acidic support modifiers, such as WO3, V205 and / or 0O3. In one embodiment, the acid modifier may comprise cobalt tungstate, for example, in an amount of 0.1 to 20% by weight, or 5 to 15% by weight. At least 85% of the acid sites on the support are Lewis acid sites.

Procedures for Making the Catalyst The present invention also relates to processes for the manufacture of the catalyst. In one embodiment, the support material is modified with one or more support modifiers and the resulting modified silica support is subsequently impregnated with a precious metal and at least one active metal to form the catalyst composition. It should be understood that the precursors can be used to add or impregnate the support material or the modified silica support. For example, the support material may be impregnated with a support modifier solution, for example, first solution, comprising a precursor to the support modifier and optionally one or more active metal precursors, such as cobalt and tin, to form the carrier support. modified silica After drying and calcining, the resulting modified silica support is impregnated with a second solution comprising the precious metal precursor and one or more active metal precursors, to form a second impregnated support, followed by drying and calcination to form the catalyst final.

The precursors are preferably composed of salts of the respective metals in the solution, which, when heated, are converted into elemental metal form or a metal oxide. In some embodiments, the cobalt and / or tin precursors are impregnated onto the support material simultaneously and / or sequentially with the precursor of the support modifier, and the cobalt and / or tin can interact with the metal support modified in a metal molecular after training to form one or more polymetallic crystalline species, such as cobalt tungstate. In other embodiments, the cobalt and / or tin will not interact with the support modifier metal precursor and are deposited separately on the support material, for example, as discrete metal nanoparticles or as a mixture of amorphous metal. Thus, the support material can be modified with one or more cobalt and / or tin precursors at the same time as it is modified with a supporting metal modifier, and the cobalt and / or tin may or may not interact with the supporting metal modifier to form one or more polymetallic crystalline species.

In some embodiments, the support modifier may be added as particles to the support material. For example, one or more support modifier precursors may be added to the support material by mixing the support modifier particles with the support material, preferably in water to form a slurry. When mixed, it is preferable for some support modifiers to use a powder material of the support modifiers. If a powder material is used, the support modifier can be granulated, crushed and sieved before being added to the support.

The support modifier can be added through a wet impregnation step using a support modifier precursor. Some exemplary carrier modifier precursors include oxides of alkali metals, alkaline earth metal oxides, metal oxides of Group IIB, metal oxides of Group IIIB, metal oxides of Group IVB, metal oxides of Group VB, metal oxides of Group VIB, metal oxides of Group VIIB, and / or metal oxides of Group VIII, as well as the preferably aqueous salts thereof.

Although the vast majority of metal oxides and polyoxyion salts are insoluble, or have a poorly defined or limited solution chemistry, the class of isopoly- and heteropolioxoions of the first transitional elements forms an important exception. These complexes can be represented by the general formulas: [MmOy] p "Isopolyaniones [XxMmOy] q "(x < m) Heteropolianiones wherein M is selected from tungsten, molybdenum, vanadium, niobium, tantalum and mixtures thereof, in their highest oxidation states (d °, d1). Such polyoxometalate anions form a structurally distinct class of complexes based predominantly, but not exclusively, on quasi-octahedrally-coordinated metal atoms. The elements that can function as the addition atoms, M, in heteropoly or isopolyanions can be limited to those with a favorable combination of ionic radium and charge and the ability to form dw-pTr M-O bonds. However, there is little restriction, in the hetero atom, X, which can be selected from virtually any element other than rare gases. See, for example, M.T. Pope, Heteropoly and Isopoly Oxometalates, Springer Verlag, Berlin, 1983, 180; Chapt. 38, Comprehensive Coordination Chemistry, Vol. 3, 1028-58, Pergamon Press, Oxford, 1987, the totalities of which are incorporated herein by reference.

Polyoxometalates (POM) and their corresponding heteropoly acids (HPA) have several advantages making them attractive economically and environmentally. First, HPAs have a very strong acidity approaching the super acid region, Bronsted acidity. In addition, they are efficient oxidants exhibiting rapidly reversible multielectron redox transformations under mild conditions. Solid HPA's also possess a discrete ionic structure comprising fairly mobile basic structural units, for example, heteropolyaniones and contracations (H +, H3O +, H5O2 +, etc.), unlike zeolites and metal oxides.

In view of the foregoing, in some embodiments, the support modifier precursor comprises a POM, which preferably comprises a metal selected from the group consisting of tungsten, molybdenum, niobium, vanadium and tantalum. In some modalities, the POM comprises a hetero-POM. A non-limiting list of suitable POMs includes phosphotungstic acid (H-PW12) (H3PW12O40 ·? 2?), Ammonium metatungstate (AMT) ((?? 4) 6? 2? 12? 4? ·? 2?) , heptamolybdate ammonium tetrahydrate, (AHM) ((?? 4) 6 ?? 7? 2? 4? 2?), silicotungstic acid hydrate (H-SiWi2) (H4SiW12O4o H2O), silicomolybdic acid (H-SiMoi2) (H4SiMoi2O4o * nH2O), and phosphomolybdic acid (H-Pmo-i2) (H3Pmoi2O4o, nH2O).

The use of support modifiers derived from POM in the catalyst compositions of the invention now surprisingly and unexpectedly have been shown to provide bi- or multi-functional catalyst functionality, which desirably results in conversions for acetic acid and by-product esters such as ethyl acetate, thereby making them convenient to catalyze the mixed feeds comprising, for example, acetic acid and ethyl acetate.

When the additionally modified silica support comprises at least one active metal, the first solution may comprise a precursor of at least one active metal selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten. , tin, lanthanum, cerium, cobalt, manganese and combinations thereof. In some embodiments, the at least one active metal in the first solution is the same precursor as the at least one active metal in the second solution.

The impregnation of the precious metal and the at least one active metal on the modified silica support can occur simultaneously (co-impregnation) or sequentially. In the simultaneous impregnation, the two or more metal precursors are mixed and added to the support, preferably modified silica support, together followed by drying and calcination to form the final composition of the catalyst. With simultaneous impregnation, it would be desirable to employ a dispersing agent, surfactant or solubilizing agent, for example, ammonium oxalate or an acid such as acetic acid or nitric acid, to facilitate dispersion or solubilization of the metal precursors in case the precursors are incompatible with the desired solvent, for example, water.

In sequential impregnation, the first metal precursor can be added to the modified silica support followed by drying and calcination, and the resulting material can then be impregnated with the remaining metal precursor, each followed by an additional drying step and a step of calcining to form the final catalyst composition. Additional metal precursors can be added in a similar way. Of course, if desired, combinations of sequential and simultaneous impregnation can be used.

In embodiments wherein the precious metal and the at least one active metal are applied to the catalyst in multiple sequential impregnation steps, it can be said that the catalyst comprises a plurality of "theoretical layers". For example, where a first metal is impregnated on a support followed by impregnation of a second metal, it can be said that the resulting catalyst has a first theoretical layer comprising the first metal and a second theoretical layer comprising the second metal. As discussed above, in some aspects, more than one cobalt and / or tin precursor can be co-impregnated onto the support in a single step, so that a theoretical layer can comprise more than one metal or metal oxide. In another aspect, the same metal precursor can be impregnated in multiple sequential steps of impregnation, resulting in the formation of multiple theoretical layers containing the same metal or oxide of metal. In this context, notwithstanding the use of the term "layers", it will be appreciated by those skilled in the art that multiple layers may or may not be formed on the catalyst support depending, for example, on the conditions used in catalyst formation, the amount of metal used in each step and the specific metals used.

The use of a solvent, such as water, glacial acetic acid, a strong acid such as hydrochloric acid, nitric acid or sulfuric acid, or an organic solvent, is preferred in the modification step of the support, for example, for the impregnation of a precursor of support modifier on the support material. The support modifier solution comprises the solvent, preferably water, a precursor of the support modifier and preferably one or more cobalt and / or tin precursors. The solution is stirred and combined with the support material using, for example, incipient moisture techniques wherein the precursor of the support modifier is added to a support material having the same pore volume as the volume of the solution. Impregnation occurs by adding, optionally drop by drop, a solution containing the precursors of either or both support modifier metals, cobalt and / or tin, to the dry support material. Then the capillary action carries the support modifier within the pores of the support material. The thus impregnated support may then be formed by drying, optionally under vacuum, which removes the solvents and any volatile components within the support mixture and the reservoir of the support modifier on and / or within. of the support material. Drying may occur, for example, at a temperature of 50 ° C to 300 ° C for a period of 1 to 24 hours. The dried support can optionally be calcined with ramp heating, for example, at a temperature of 300 ° C to 900 ° C for a period of time from 1 to 12 hours to form the final modified silica support. During heating and / or vacuum application, the metal (s) of the precursor (s) are preferably decomposed in their oxide or elemental form. In some cases, the termination of the solvent removal may not take place until the catalyst is put into use and / or calcined, for example, subjected to the high temperatures encountered during the operation. During the calcination step, or at least during the initial phase of the use of the catalyst, said compounds are converted into a catalytically active form of the metal or a catalytically active oxide thereof.

Once formed, the modified silica supports can be formed into particles having a desired size distribution, for example, to form particles having an average particle size in the range of 0.2 to 0.4 cm. The supports can be extruded, formed into pellets, into tablets, they can be compressed, crushed or sifted to the desired size distribution. Any of the known methods for forming the support materials in a desired size distribution can be employed. Alternatively, the support pellets can be used as the starting material used to make the modified silica support and, ultimately, the final catalyst.

In one embodiment, the catalyst of the present invention can be prepared with a bulk catalyst technique. Bulk catalysts can be formed by precipitating precursors of the support modifier, cobalt and / or tin metals. The precipitation can be controlled by changing the temperature, pressure and / or pH. In some embodiments, the preparation of bulk catalysts may utilize a binder. A support material can not be used in a bulk catalyst process. Once precipitated, the bulk catalyst can be formed by spray drying, pelletization, granulation, tablet pressing, beading, or peeling. Suitable bulk catalyst techniques such as those described in Krijn P. de Jong, ed., Synthesis of Solid Catalysts, Wiley, (2009), p. 308, the content and full description of which is incorporated herein by reference.

In one embodiment, the precious metal and the at least one active metal are impregnated on the support, preferably on any of the modified silica supports described above. A precursor of the precious metal is preferably used in the metal impregnation step, as a water-soluble compound or water-dispersible compound / complex that includes the precious metal of interest. Similarly, one or more cobalt and / or tin precursors may also be impregnated in the support, preferably modified silica support. Depending on the metal precursors used, the use of a solvent, such as water, glacial acetic acid, nitric acid or an organic solvent, can be preferred to solubilize the metal precursors.

In one embodiment, separate solutions of the metal precursors are formed, which are subsequently mixed before being impregnated onto the support material. For example, a first solution comprising a first metal precursor can be formed, and a second solution comprising a second metal precursor and optionally a third metal precursor can be formed. At least one of the optional first, second and third metal precursor is preferably a precious metal precursor, and the other or the others are preferably cobalt and / or tin precursors (which may or may not comprise precious metal precursors). Either or both solutions preferably comprise a solvent, such as water, glacial acetic acid, hydrochloric acid, nitric acid or an organic solvent.

In an exemplary embodiment, a first solution comprising a first metal halide is prepared. In some embodiments, the first metal halide comprises a tin halide, for example, a tin chloride such as tin (II) chloride and / or tin (IV) chloride. A second metal precursor, as a solid or as a separate solution, is combined with the first solution to form a combined solution. In some embodiments, the second metal precursor comprises a cobalt oxalate, acetate, halide or nitrate. A second solution is also prepared comprising a precious metal precursor, such as a halide of rhodium, rhenium, ruthenium, platinum or palladium. The second solution is combined with the combined solution to form a mixed metal precursor solution. The resulting mixed metal precursor solution can then be added to the modified silica support, followed by drying and calcination to form the final catalyst composition as described above. The resulting catalyst may or may not be washed after the final calcination step. Due to the difficulty in the solubilization of some precursors, it may be desirable to reduce the pH of the first and / or second solutions, for example by using an acid such as acetic acid, hydrochloric acid or nitric acid, for example, HN03 6 to 10 M .

In another aspect, a first solution comprising a first metal oxalate, such as a cobalt and / or tin oxalate, is prepared. In this embodiment, the first solution preferably additionally comprises an acid such as acetic acid, hydrochloric acid, phosphoric acid or nitric acid, for example, HN03 6 to 10 M. A second metal precursor, as a solid or as a separate solution, it is combined with the first solution to form a combined solution. The second metal precursor, if used, preferably comprises oxalate, acetate, halide or cobalt nitrate. A second solution comprising a precious metal oxalate, for example, a rhodium, rhenium, ruthenium, platinum or palladium oxalate is also formed and optionally further comprises an acid such as acetic acid, hydrochloric acid, phosphoric acid or nitric acid, Example, HNO3 6 to 10 M. The second solution is combined with the combined solution to form a mixed metal precursor solution. The solution of The resulting mixed metal precursor can then be added to the modified silica support, followed by drying and calcination to form the final catalyst composition as described above. The resulting catalyst may or may not be washed after the final calcination step.

In one embodiment, the impregnated modified silica support is dried at a temperature of 100 ° C to 140 ° C for 1 to 12 hours. If calcination is desired, it is preferable that the calcination temperature employed in this step be less than the calcination temperature employed in the formation of the modified silica support, discussed above. The second calcination step, for example, can be conducted at a temperature that is at least 50 ° C lower than that of the first calcination step. For example, the impregnated catalyst can be calcined at a temperature of 200 ° C to 500 ° C for a period of 1 to 12 hours.

In one embodiment, ammonium oxalate is used to solubilize at least one of the metal precursors, for example, a tin precursor, as described in U.S. Pat. No. 8,21 1, 821, the entirety of which is incorporated herein by reference. In this regard, a solution of the second metal precursor can be made in the presence of ammonium oxalate as the solubilizing agent, and the precious metal precursor can be added thereto, optionally as a solid or a separate solution. If used, the third metal precursor can be combined with the solution comprising the first precursor and the oxalate precursor of tin, or may be combined with the second metal precursor, optionally as a solid or a separate solution, before the addition of the first metal precursor. In other embodiments, an acid such as acetic acid, hydrochloric acid or nitric acid can be substituted with ammonium oxalate to facilitate the solubilization of tin oxalate. The resulting mixed metal precursor solution can then be added to the modified silica support followed by drying and calcination to form the final catalyst composition as described above.

The specific precursors used in the various embodiments of the invention may vary widely. Suitable metal precursors may include, for example, metal halides, solubilized metal hydroxides of amine, metal nitrates or metal oxalates. For example, suitable compounds for platinum precursors and palladium precursors include chloroplatinic acid, ammonium chloroplatinate, solubilized amine platinum hydroxide, platinum nitrate, tetraplatinum ammonium nitrate, platinum chloride, platinum oxalate, palladium nitrate. , tetra palladium ammonium nitrate, palladium chloride, palladium oxalate, palladium sodium chloride, sodium platinum chloride and platinum ammonium nitrate, Pt (NH3) (N04) 2. In general, both from the standpoint of economics and environmental aspects, aqueous solutions of soluble platinum and palladium compounds are preferable. In one embodiment, the precious metal precursor is not a metal halide and is substantially free of metal halides, while in others modalities, as described above, the precious metal precursor is a halide.

In another example, the cobalt and / or tin are co-impregnated with the tungsten precursor on the support material and can form an oxide mixed with W03, for example, cobalt tungstate, followed by drying and calcination. The resulting modified silica support can be impregnated, preferably in a single impregnation step or multiple impregnation steps, with one or more of precious metals, cobalt and / or tin followed by a second drying and calcination step. In this way, cobalt tungstate can be formed on the modified silica support. Again, the temperature of the second calcination step is preferably lower than the temperature of the first calcination step.

Use of the Catalyst for Hydrogenating Acetic Acid and Ethyl Acetate An advantage of the catalysts of the present invention is the stability or activity of the catalyst to produce ethanol. Therefore, it will be appreciated that the catalysts of the present invention are fully capable of being used in commercial scale industrial applications for the hydrogenation of acetic acid, particularly in the production of ethanol. In particular, it is possible to achieve a degree of stability such that the activity of the catalyst will have a rate of decrease in productivity that is less than 6% per 100 hours of catalyst use, example, less than 3% per 100 hours or less than 1.5% per 100 hours. Preferably, the rate of decline in productivity is determined once the catalyst has reached steady state conditions.

After completing the drying and calcination of the catalyst, the catalyst can be reduced to activate it. The reduction is carried out in the presence of a reducing gas, preferably hydrogen. The reducing gas optionally is continuously passed over the catalyst at an initial ambient temperature which increases up to 400 ° C. In one embodiment, the reduction is carried out after the catalyst has been charged into the reaction vessel where the hydrogenation will take place. The Lewis acid sites on the catalyst must be stable, so that they are not reduced under the hydrogenation conditions.

In one embodiment, the invention is a process for producing ethanol by hydrogenation of a feed stream comprising compounds selected from acetic acid, ethyl acetate and mixtures thereof in the presence of any of the catalysts described above. In some embodiments, the feed stream may comprise at least 5% by weight of ethyl acetate, for example, at least 10% by weight or at least 15% by weight. A particular preferred reaction is to make ethanol from acetic acid. The hydrogenation reaction can be represented as follows: HOAc + 2 H2? EtOH + H20 In some embodiments, the catalyst can be characterized as a bifunctional catalyst because it effectively catalyzes the hydrogenation of acetic acid to ethanol, as well as the conversion of ethyl acetate into one or more products, preferably ethanol.

The raw materials, acetic acid and hydrogen, fed to the reactor used in conjunction with the process of this invention can be derived from any suitable source including natural gas, petroleum, coal, biomass, etc. As examples, acetic acid can be produced by means of carbonylation of methanol, oxidation of acetaldehyde, oxidation of ethane, oxidative fermentation and anaerobic fermentation. Methods of methanol carbonylation suitable for the production of acetic acid are described in U.S. Pat. Nos. 7,208,624; 7.1 15.772; 7,005,541; 6,657,078; 6,627,770; 6,143,930; 5,599,976; 5,144,068; 5,026,908; 5,001, 259; and 4,994,608, the total disclosures of which are incorporated herein by reference. Optionally, the production of ethanol can be integrated with such methanol carbonylation processes.

Because oil and natural gas prices fluctuate by becoming more or less expensive, methods to produce acetic acid and intermediates such as methanol and carbon monoxide from other carbon sources have attracted increasing interest. In particular, when the oil is relatively expensive, it may be advantageous to produce acetic acid from synthesis gas ("syngas") which is derived from other available carbon sources. U.S. Pat. No. 6,232,352, the entirety of which is incorporated herein by reference, for example, teaches a method for adapting a methanol plant for the manufacture of acetic acid. When adapting a methanol plant, the large capital costs associated with the generation of CO for a new acetic acid plant are significantly reduced or eliminated to a large extent. All or part of the synthesis gas deviates from the methanol synthesis cycle and is supplied to a separating unit to recover the CO, which is then used to produce acetic acid. In a similar manner, the hydrogen for the hydrogenation step can be supplied with the synthesis gas.

In some embodiments, some or all of the raw materials for the acetic acid hydrogenation process described above may be partially or completely derived from the synthesis gas. For example, acetic acid can be formed from methanol and carbon monoxide, both of which can be derived from the synthesis gas. The synthesis gas can be formed by partial oxidation or steam reforming, and the carbon monoxide can be separated from the synthesis gas. Similarly, the hydrogen that is used in the hydrogenation step of acetic acid to form the crude ethanol product can be separated from the synthesis gas. The synthesis gas, in turn, can be derived from a variety of carbon sources. The carbon source, for example, can be selected from the group consisting of natural gas, oil, petroleum, coal, biomass and combinations thereof. Synthesis gas or hydrogen can also be obtained from bio-derived methane gas, such as bio-derived methane gas produced by landfills or agricultural waste.

Examples of biomass include, but are not limited to, agricultural waste, forestry products, turf, and other cellulosic material, extracted wood waste, softwood chips, hardwood chips, tree branches, stump, leaves, bark, sawdust , paper pulp out of specification, corn, corn fodder, wheat straw, rice straw, sugarcane bagasse, rod grass, miscanthus, animal manure, municipal waste, municipal wastewater, commercial waste, grape bagasse , almond shells, pecan shells, coconut shells, coffee grinding, grass granules, hay granules, wood granules, cardboard, paper, plastic, and cloth. Black liquor, which is an aqueous solution of lignin residues, calcination and inorganic chemical compounds, can also be used as a source of biomass. Synthesis gas derived from biomass has a detectable isotope content of 1 C compared to fossil fuels such as coal or natural gas.

In another embodiment, the acetic acid used in the hydrogenation step can be formed from the fermentation of biomass. The fermentation process preferably uses an acetogenic process or a homozygogenic microorganism to ferment sugars to acetic acid which produces little, if any, carbon dioxide as a by-product. The carbon efficiency for the fermentation process is preferably greater than 70%, greater than 80% or greater than 90% compared to the conventional yeast process, which typically has a carbon efficiency of approximately 67%. He The microorganism used in the fermentation process can be Clostridium formicoaceticum, Clostridium butyricum, Moorella thermoacetica, Thermoanaerobacter kivui, Lactobacillus delbrukii, Propionibacterium acidipropionici, Propionispera arboris, Anaerobiospirillum succinicproducens, Bacteriodes amylophilus and Bacteriodes ruminicola. Optionally, in this process, all or a portion of the unfermented residue of the biomass, for example, lignans, can be gasified to form hydrogen that can be used in the hydrogenation step of the present invention. Exemplary fermentation processes are described for forming acetic acid in U.S. Pat. No. 6,509,180, and in the US Publications. Nos. 2008/0193989 and 2009/0281354, all of which is incorporated herein by reference.

U.S. Pat. No. RE 35,377, also incorporated herein by reference, provides a method for the production of methanol by the conversion of carbonaceous materials such as petroleum, coal, natural gas and biomass materials. The process includes hydrogasification of solid and / or liquid carbonaceous materials to obtain a process gas, which is pyrolyzed vapor with additional natural gas to form synthesis gas. The synthesis gas is converted to methanol, which can be carbonylated in acetic acid. The method likewise produces hydrogen, which can be used in connection with this invention as noted above. U.S. Pat. No. 5,821, 1 1 1, which discloses a procedure for converting waste biomass through gasification in the synthesis gas and U.S. Pat. No. 6,685,754, which discloses a method for the production of a hydrogen-containing gas composition, as a synthesis gas including hydrogen and carbon monoxide, is incorporated herein by reference in its entirety.

The acetic acid fed into the hydrogenation reactor may also comprise other carboxylic acids and anhydrides, as well as aldehydes and / or ketones, such as acetaldehyde and acetone. Preferably, the feed stream comprises acetic acid and ethyl acetate. A suitable acetic acid feed stream comprises one or more compounds selected from the group consisting of acetic acid, acetic anhydride, acetaldehyde, ethyl acetate, diethyl acetal, diethyl ether, and mixtures thereof. These other compounds can also be hydrogenated in the methods of the present invention. In some embodiments, the presence of carboxylic acids, such as propanoic acid or its aldehyde, may be beneficial in the production of propanol. Water may also be present in the acetic acid feed.

Alternatively, the acetic acid in vapor form can be taken directly as the raw product from the vent vessel of a methanol carbonylation unit of the kind described in US Pat. No. 6,657,078, the entirety of which is incorporated herein by reference. The raw steam product, for example, can be fed directly into the hydrogenation reactor without the need to condense acetic acid and light ends or remove water, saving the costs of global processing.

The acetic acid can be vaporized at the reaction temperature, after which the vaporized acetic acid can be fed together with hydrogen in an undiluted state or diluted with a relatively inert carrier gas, such as nitrogen, argon, helium, carbon dioxide and the like. For the reactions carried out in the vapor phase, the temperature must be controlled in the system in such a way that it does not fall below the dew point of the acetic acid. In one embodiment, the acetic acid can be vaporized to the boiling point of acetic acid at the particular pressure, and then the vaporized acetic acid can be further heated to the inlet temperature of the reactor. In another embodiment, the acetic acid is mixed with other gases before vaporizing, followed by heating the mixed vapors to the inlet temperature of the reactor. Preferably, the acetic acid is transferred to the vapor state by passing hydrogen and / or recycle gas through the acetic acid at a temperature equal to or lower than 125 ° C, followed by heating the combined gas stream to the inlet temperature. of the reactor.

The reactor, in some embodiments, may include a variety of configurations using a fixed bed reactor or a fluidized bed reactor. In many embodiments of the present invention, an "adiabatic" reactor may be used; that is, there is little or no need for internal pipes through the reaction zone to add or remove heat. In other embodiments, a radial flow reactor or reactors can be used as the reactor, or a series of reactors can be employed with or without heat exchange, tempering, or introduction of additional feedstock. Alternatively, a shell and shell reactor provided with a heat transfer medium can be used. In many cases, the reaction zone may be housed in a single container or in a series of containers with heat exchangers therebetween.

In preferred embodiments, the catalyst is employed in a fixed-bed reactor, for example, in the form of a pipe or tube, wherein reagents, typically in vapor form, are passed over or through the catalyst. Other reactors, such as fluid bed or boiling reactors, can be used. In some cases, the hydrogenation catalysts can be used in conjunction with an inert material to regulate the pressure drop of the reactant stream through the catalyst bed and the contact time of the reactive compounds with the catalyst particles. In some embodiments, multiple catalyst beds are employed in the same reactor or in different reactors, for example, in series. For example, in one embodiment, a first catalyst functions in a first catalyst stage as a catalyst for the hydrogenation of a carboxylic acid, for example, acetic acid, to its corresponding alcohol, for example, ethanol and a second bifunctional catalyst is employed in the second step to convert unreacted acetic acid into ethanol as well as the conversion of by-product ester, for example, ethyl acetate, to additional products, preferably to ethanol. The catalysts of invention can be employed in either or both of the first and / or second stages of such reaction systems.

The hydrogenation in the reactor can be carried out in the liquid phase or in the vapor phase. Preferably, the reaction is carried out in the vapor phase under the following conditions. The reaction temperature can vary from 125 ° C to 350 ° C. The pressure can vary from 10 kPa to 3000 kPa, for example, from 50 kPa to 2500 kPa. The reagents can be fed to the reactor at a space velocity per hour of gas which can vary from 50 hr "1 to 50,000 hr".

Although the reaction consumes two moles of hydrogen per mole of acetic acid to produce one mole of ethanol, the actual molar ratio of hydrogen to acetic acid in the feed stream can vary from about 100: 1 to 1: 100, e.g. 50: 1 to 1: 50, from 20: 1 to 1: 2, or from 18: 1 to 2: 1. More preferably, the molar ratio of hydrogen to acetic acid is greater than 2: 1, for example, greater than 4: 1 or greater than 8: 1. For a mixed feed stream, the molar ratio of hydrogen to ethyl acetate may be greater than 5: 1, for example, greater than 10: 1 or greater than 15: 1.

The contact or residence time can also vary widely, depending on variables such as the amount of feed stream (acetic acid and / or ethyl acetate), catalyst, reactor, temperature and pressure. The common contact times range from a fraction of a second to more than several hours when a system is used. catalyst other than a fixed bed, with preferred contact times, at least for vapor phase reactions, from 0.1 to 100 seconds, for example, from 0.3 to 80 seconds or from 0.4 to 30 seconds.

In particular, by using the catalysts of the invention, the hydrogenation of acetic acid and / or ethyl acetate can achieve favorable conversion and favorable selectivity and productivity of ethanol in the reactor. For purposes of the present invention, the term "conversion" refers to the amount of acetic acid or ethyl acetate, whichever is specified, in the feed that is converted to a compound other than acetic acid or ethyl acetate, respectively. The conversion is expressed as a percentage based on acetic acid or ethyl acetate in the feed. The conversion of acetic acid can be at least 75%, more preferably at least 80%, at least 90%, at least 95% or at least 99%.

During the hydrogenation of acetic acid, ethyl acetate can be produced as a by-product. Without consuming any ethyl acetate from the mixed vapor phase reagents, the concentration of ethyl acetate in the crude product would be higher than the concentration of ethyl acetate in the feed stream. Some of the catalysts described herein are monofunctional in nature and are effective for converting acetic acid to ethanol, but not for the conversion of ethyl acetate. The use of monofunctional catalysts can result in the undesirable accumulation of ethyl acetate in the system, particularly for systems employing one or more recycle streams containing ethyl acetate to the reactor.

The preferred catalysts of the invention, however, are multifunctional in that they effectively catalyze the conversion of acetic acid to ethanol, as well as the conversion of an alkyl acetate, such as ethyl acetate, to one or more other products of the alkyl acetate. The multifunctional catalyst is preferably effective for the consumption of ethyl acetate at a sufficiently large rate to compensate at least the production rate of ethyl acetate, resulting in a non-net production of ethyl acetate. The use of such catalysts can result, for example, in an ethyl acetate conversion that is greater than 5%. In some embodiments, when the raw material comprises ethyl acetate in an amount greater than 0%, the conversion of ethyl acetate is greater than 5% and the conversion of acetic acid is greater than 20%.

In continuous processes, the ethyl acetate being added (eg, recycled) to the hydrogenation reactor and the ethyl acetate leaving the reactor in the crude product preferably approaches a certain level after the process reaches equilibrium. The use of a multifunctional catalyst that catalyzes the conversion of ethyl acetate, as well as acetic acid results in a lower amount of ethyl acetate added to the reactor and less ethyl acetate is produced with respect to the monofunctional catalysts. In preferred embodiments, the concentration of ethyl acetate in the mixed feed and crude product is less than 40 % by weight, less than 25% by weight or less than 15% by weight after the equilibrium was achieved. In preferred embodiments, the process forms a crude product comprising ethanol and ethyl acetate and the crude product has a steady state concentration of ethyl acetate of 0.1 to 40% by weight, eg, 0.1 to 20% by weight or from 0.1 to 15% by weight.

Although catalysts having high acetic acid conversions are desirable, such as at least 75%, in some embodiments a low conversion may be acceptable at high selectivity for ethanol. Of course, it is understood that in many cases, it is possible to compensate the conversion by suitable recycle streams or use of larger reactors, but it is more difficult to compensate for the low selectivity.

The selectivity is expressed as a mole percentage based on the converted acetic acid and / or ethyl acetate. It should be understood that each converted compound of acetic acid and / or ethyl acetate has an independent selectivity and that the selectivity is independent of the conversion. For example, if 60 mol% of the converted acetic acid is converted to ethanol, we refer to the selectivity of ethanol as 60%. For purposes of the present invention, the total selectivity is based on the combined converted acetic acid and ethyl acetate. Preferably, the total selectivity of ethanol is at least 60%, for example, at least 70%, or at least 80%, at least 85% or at least 88%. Preferred embodiments of the hydrogenation process also have low selectivity for undesirable products, such as methane, ethane, and carbon dioxide. The selectivity for these undesirable products is preferably less than 4%, for example, less than 2% or less than 1%. More preferably, these undesirable products are present in undetectable amounts. The formation of aléanos can be low, and ideally less than 2%, less than 1%, or less than 0.5% of the acetic acid passed over the catalyst is converted to alénes, which have little value except as fuels.

The term "productivity," as used herein, refers to the grams of a specified product, for example, ethanol, formed during hydrogenation based on the kilograms of the catalyst used per hour. The productivity can vary from 100 to 3000 grams of ethanol per kilogram of catalyst per hour.

In various embodiments of the present invention, the crude ethanol product produced by the reactor, before any further processing, such as purification and separation, will normally comprise unreacted acetic acid, ethanol and water. As described herein, the inventive catalysts result in low selectivity of acetic acid or ethyl acetate to diethyl ether. Exemplary composition intervals for the crude ethanol product are given in Table 1. The "others" identified in Table 1 may include, for example, esters, ethers, aldehydes, ketones, alkanes and carbon dioxide.

TABLE 1 Raw ethanol product compositions Conc. Conc. Conc. Conc.

Component (% by weight) (% by weight) (% by weight) (% by weight) Ethanol 5 to 72 15 to 72 15 to 70 25 to 65 Acetic Acid 0 to 90 0 to 50 0 to 35 0 to 15 Water 5 to 40 5 to 30 10 to 30 10 to 26 Ethyl Acetate 0 to 30 1 to 25 3 to 20 5 to 18 Acetaldehyde O at 10 0 to 3 0.1 to 3 0.2 to 2 Diethyl Ether 0 to 3 0 to 1 0 to 0.5 0 to 0.2 Other 0.1 to 10 0.1 to 6 0.1 to 4 - In one embodiment, the crude ethanol product may comprise acetic acid in an amount of less than 20% by weight, for example, less than 15% by weight, less than 10% by weight or less than 5% by weight. In terms of ranges, the concentration of acetic acid in Table 1 may vary from 0.1% by weight to 20% by weight, eg, from 0.1% by weight to 15% by weight, from 0.1% by weight to 10% by weight , or from 0.1% by weight to 5% by weight. In embodiments having low amounts of acetic acid, the conversion of acetic acid is preferably greater than 75%, for example, greater than 85% or greater than 90%. In addition, the selectivity of ethanol may also be preferably high and is greater than 75%, eg, more than 85% or more than 90%.

An ethanol product can be recovered from the crude product of ethanol produced by the reactor using the catalyst of the present invention can be recovered using several different techniques.

The ethanol product can be an industrial grade ethanol comprising from 75 to 96% by weight of ethanol, for example from 80 to 96% by weight. weight or 85 to 96% by weight of ethanol, based on the total weight of the ethanol product. The industrial grade ethanol may have a water concentration of less than 12% by weight of water, for example, less than 8% by weight or less than 3% by weight. In some embodiments, when more water separation is used, the ethanol product preferably contains ethanol in an amount greater than 96% by weight, eg, greater than 98% by weight or greater than 99.5% by weight. The ethanol product having more water separation preferably comprises less than 3% by weight of water, for example, less than 2% by weight or less than 0.5% by weight.

The finished ethanol composition produced by the embodiments of the present invention can be used in a variety of applications including fuels, solvents, chemical raw materials, pharmaceuticals, cleaners, sanitizers, transportation or hydrogen consumption. In fuel applications, the finished ethanol composition can be mixed with gasoline for motor vehicles such as automobiles, boats and small aircraft with piston engines. In non-combustible applications, the final ethanol composition can be used as a solvent for toiletries and cosmetic preparations, detergents, disinfectants, coatings, inks and pharmaceuticals. The final ethanol composition can also be used as a processing solvent in processes for manufacturing medical products, food preparations, dyes, photochemical compounds and latex processing.

The finished ethanol composition can also be used as a chemical raw material to make other chemical compounds such as vinegar, ethyl acrylate, ethyl acetate, ethylene, glycol ethers, ethylamines, ethylbenzene, aldehydes, butadiene and higher alcohols, especially butanol . In the production of ethyl acetate, the final ethanol composition can be esterified with acetic acid. In another application, the final ethanol composition can be dehydrated to produce ethylene. Any known dehydration catalyst, such as zeolite catalysts or phosphotungstic acid catalysts, can be used to dehydrate ethanol, as described in US Publications. Nos. 2010/0030002 and 2010/0030001 and WO2010146332, whose descriptions and complete contents are incorporated herein by reference.

The following examples describe the catalyst and the process of this invention.

EXAMPLES EXAMPLE 1 A silica support, modified with cobalt, tin and tungsten, was tested using pyridine as a probe molecule to study whether the acid sites were Lewis acid sites or Bronsted acid sites. The silica support was pre-treated with pyridine at 200 ° C for 6 hours, under vacuum.

Before being used to pre-treat the silica support, the pyridine liquid was pre-treated using a lyophilization process to remove any moisture. The pyridine adsorption test was conducted at room temperature, at approximately 21 ° C, for 15 hours. The silica support was then treated again at 120 ° C for 2.5 hours, under vacuum to remove any slightly adsorbed pyridine. The adsorption was measured using FTIR of chemisorbed pyridine. The FTIR spectra for this Example are shown in Figure 1. Heat post-treatment shows 78% of Lewis acid sites.

EXAMPLE 2 The example was prepared and tested as in Example 1, except that the silica support was modified with alumina, calcined and then impregnated with platinum and tin. The FTIR spectra for this Example are shown in Figure 2. The heat post-treatment shows 66% of Lewis acid sites.

EXAMPLE 3 The example was prepared and tested as in Example 1, except that the silica support was modified with tungsten oxide, calcined and then impregnated with platinum and tin. The FTIR spectra for this Examples are shown in Figure 3. The post-heat treatment shows 87% of Lewis acid sites.

EXAMPLE 4 The example was prepared and tested as in Example 1, except that the silica support was modified with cobalt, tin and tungsten, calcined and then impregnated with platinum and tin. The FTIR spectra for this Example are shown in Figure 4. Heat post-treatment shows 100% Lewis acid sites.

COMPARATIVE EXAMPLE A The example was prepared and tested as in Example 1, except that the silica support was not modified or impregnated with any metal.

COMPARATIVE EXAMPLE B The example was prepared and tested as in Example 1, except that the silica support was modified with calcium metasilicate, calcined and then impregnated with platinum and tin.

COMPARATIVE EXAMPLE C The example was prepared and tested as in Example 1, except that the silica support was modified with tungsten oxide.

The results of the FTIR spectrum analysis for the Examples 1-4 and Comparative Examples A-C are shown below.

TABLE 2 Analysis of acid sites Acid Sites Acid Sites by Lewis Bronsted Example 1 78% 22% Example 2 66% 34% Example 3 87% 13% Example 4 100% 0% Comparative Example - - TO Comparative Example - - B Comparative Example 46% 54% C The catalysts of Examples 2, 3 and 4 were fed to a test unit using one of the following run conditions.

The test unit consists of four independent tubular fixed bed reactor systems with common temperature, pressure and gas control and liquid feed. The reactors were made from 3/8 inch SS (316) and 12 1/8 inch (30.8 cm) long tubes. The vaporizers were made of SS 316 3/8 inch (0.95 cm) pipe and they were 12 3/8 inches (31.45 cm) long. The reactors, vaporizers and their respective effluent transfer lines were electrically heated (heat tape).

The reactor effluents were routed to cooled water condensers and knock out vessels. The condensed liquids were collected automatically and then manually drained from the knock out vessels as needed. The non-condensed gases were passed through a manual counterpressure regulator (BPR) and then washed through the water and vented to the extractor hood. For each example, 15 ml of catalyst (3 mm pellets) were charged to the reactor. Both the inlet and outlet of the reactor were filled with glass beads (3 mm) to form the fixed bed. The following operating conditions were used for the catalyst: T = 275 ° C, P = 300 psig (2068 kPag), [Feed] = 0.138 ml / min (pumping speed), and [H2] = 513 sccm, space velocity Gas Hour (GHSV) = 2246 hr "1. The blended feed comprised about 70% by weight of acetic acid and about 20% by weight of ethyl acetate, Other components included diethyl acetal, water, acetaldehyde and ethanol.

The crude product was analyzed by gas chromatography (Agilent GC Model 6850), equipped with a flame ionization detector. The amounts of diethyl ether and ethyl acetate are shown below in Table 3.

TABLE 3 Production of ethyl acetate and diethyl ether Ethyl Acetate Diethyl Ether (% by weight) (% by weight) Example 2 Example 3 27.32 0.14 Example 4 36.18 0.04 As can be seen in Table 3, the catalyst for the Examples 2-4 results in low selectivity of the mixed feed for diethyl ether.

Although the invention has been described in detail, modifications within the spirit and scope of the invention will be easily apparent to those skilled in the art. All publications and the references mentioned are incorporated here by reference. In addition, it is to be understood that aspects of the invention and portions of various modalities and various recited characteristics may be combined or exchanged in whole or in part. In the previous descriptions of the different modalities, those modalities that refer to another modality can appropriately be combined with other modalities as will be appreciated by a person skilled in the art. In addition, It will be appreciated by those skilled in the art that the foregoing description is to of example only and is not intended to limit the invention.

Claims (15)

1. NOVELTY OF THE INVENTION CLAIMS 1. - A hydrogenation catalyst comprising a precious metal and at least one active metal on a modified silica support, wherein the catalyst has at least 70% Lewis acid sites based on the total number of acid sites measured by means of of Fourier-transformed infrared spectroscopy of chemisorbed pyridine, and wherein the modified silica support comprises: (i) a support material; and (ii) a support modifier comprising a metal selected from the group consisting of tungsten, molybdenum, vanadium, niobium and tantalum. 2 - . 2 - The catalyst according to claim 1, further characterized in that the catalyst has at least 80% of Lewis acid sites, based on the total number of acid sites, measured by means of infrared Fourier transform pyridine chemisorbed spectroscopy . 3. - The catalyst according to any of the preceding claims, further characterized in that the catalyst has at least 85% of Lewis acid sites, based on the total number of acid sites, as measured by infrared Fourier transform pyridine spectroscopy chemisorbed. 4. - The catalyst according to any of the preceding claims, further characterized in that the support modifier is present from 0.1 to 50% by weight, based on the total weight of the catalyst. 5. - The catalyst according to any of the preceding claims, further characterized in that the modified silica support comprises cobalt tungstate. 6. - The catalyst according to any of the preceding claims, further characterized in that the precious metal is selected from the group consisting of rhodium, rhenium, ruthenium, platinum, palladium, osmium, iridium and gold. 7. The catalyst according to any of the preceding claims, further characterized in that the at least one active metal is selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. 8 -. 8 - The catalyst according to any of the preceding claims, further characterized in that the modified silica support comprises a support material and tungsten. 9. - The catalyst according to any of the preceding claims, further characterized in that the modified silica support additionally comprises cobalt and / or tin. 10. - The catalyst in accordance with any of the previous claims, further characterized in that the catalyst is prepared: (a) by impregnating a support material with a first solution to form a first impregnated support, wherein the first solution comprises a precursor of the support modifier metal selected from the group consisting of tungsten, molybdenum, niobium, vanadium, and tantalum; (b) calcining the first impregnated support to form a modified silica support; (c) impregnating the modified silica support with a second solution to form a second impregnated support, wherein the second solution comprises a precious metal precursor, and a precursor of at least one active metal; and (d) calcining the second impregnated support to form the catalyst. eleven . - The catalyst according to claim 10, further characterized in that the first solution additionally comprises a precursor of at least one active metal selected from the group consisting of copper, iron, vanadium, nickel, titanium, zinc, chromium, molybdenum, tungsten, tin, lanthanum, cerium, cobalt, manganese and combinations thereof. 12. The catalyst according to any of claims 10 to 11, further characterized in that the precursor of at least one active metal in the first solution is the same precursor of at least one active metal in the second solution. 13. - The catalyst according to any of claims 10 to 12, further characterized in that the support material has no acidic acid sites before being impregnated with the first solution. 14. The catalyst according to any of claims 10 to 13, further characterized in that the modified silica support has at least 50% Lewis acid sites, based on the total number of acid sites, measured by means of infrared spectroscopy Fourier transform of chemisorbed pyridine. 15. - The catalyst according to any of claims 10 to 14, further characterized in that the modified silica support has at least 60% Lewis acid sites, based on the total number of acid sites, measured by means of infrared spectroscopy Fourier transform of chemisorbed pyridine.