MXPA99004691A - A process to prepare a catalyst - Google Patents

Abstract

A process for preparing a catalyst is disclosed. This catalyst is useful for the oxidation, in gas phase, of alkanes, to infused aldehydes or carboxylic acids

Description

A PROCESS TO PREPARE A CATALYST This invention relates to a process for preparing a catalyst. In particular, the invention relates to a process for preparing a catalyst, which is efficient in converting the alkanes into unsaturated aldehydes and carboxylic acids, to the catalyst prepared by the process, and to a process for preparing the unsaturated carboxylic aldehydes and acids with the use of the catalyst. Aldehydes and unsaturated carboxylic acids are important commercial chemicals. Of particular importance is (meth) acrylic acid. The highly reactive double bond and the acid function of (meth) acrylic acid, make it especially suitable as a monomer, which can be polymerized alone or with other monomers to produce commercially important polymers. These unsaturated acids are also useful as starting materials for esterification, to produce commercially important (meth) acrylate esters. Materials derived from (meth) acrylic acid or (meth) acrylic acid esters are useful as sheets and plastic parts, paints and other coatings, adhesives, fillers, sealants and detergents, as well as other applications. The production of the unsaturated carboxylic acids by the oxidation of an olefin is well known in the art Acrylic acid, for example, can be manufactured commercially by the oxidation, in the gas phase, of propylene. Unsaturated carboxylic acids can also be prepared by the oxidation of alkanes, for example, acrylic acid can be prepared by the oxidation of propane, which is particularly convenient, since alkanes generally cost less than olefins. For example, at the time of submitting this application, the costs of propylene are approximately three times higher than those of propane.An adequate process for the oxidation of alkanes to aldehydes or unsaturated carboxylic acids, which is commercially viable, has yet to be achieved. An impediment to the production of a commercially viable process for the catalytic oxidation of an alkane to an acid unsaturated carboxylic acid is the identification of a catalyst that has a conversion suitable and appropriate selectivity, thus providing a sufficient yield of a final unsaturated carboxylic acid product. U.S. Patent No. 5,380,933, discloses a method for preparing a catalyst useful in the gas phase oxidation of an alkane to an unsaturated carboxylic acid. In the method described, a catalyst is prepared by combining the ammonium meta-vanadate, telluric acid and ammonium para-molybdate to obtain a uniform aqueous solution. To this solution is added niobium oxalate and ammonium to obtain an aqueous paste. The water is removed from the aqueous paste to obtain a solid catalyst precursor. This solid catalyst precursor is molded into tablets, screened to a desired particle size and then calcined at 600 ° C under a stream of nitrogen to obtain the desired catalyst. The resulting catalyst is claimed to be effective in converting propane to acrylic acid. However, as shown here, the present inventor was unable to reproduce the claimed results using the method of preparation of the '933 patent. While not wishing to be bound by theory, it is believed that the poor performance of the The prior art method of the '933 patent results from the state of composition or phase segregation of the catalyst component elements, for example, in the aqueous paste between the solid and liquid phases and during the calcination between the gas and various phases solid. The present inventor has now discovered a process for preparing a catalyst for catalyzing an alkane in an unsaturated carboxylic acid or aldehyde, wherein phase segregation is minimized and improvements in selectivity, conversion and yield are achieved. In one aspect of the present invention, a process for preparing a catalyst is provided, this method includes: (A) mixing metal compounds, at least one of which is an oxygen-containing compound, and at least one solvent, to form a solution; (B) removing the solvent from the solution, to obtain a catalyst precursor; and (C) calcining this catalyst precursor at a temperature of 350 to 850 ° C, under an inert atmosphere, to form a catalyst having the formula: AaMmNnXx0oen that: 0.25 < a < 0.98, 0.003 < m < 0.5, 0. 003 < n < 0.5, 0.003 < x < 0.5, and o is dependent on the oxidation state of the other elements, and A is select from: Mo,, Fe, Nb, Ta, Zr, Ru, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected from Te, Bi, Sb, Se, and mixtures thereof; and X is selected from Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, Ce, and mixtures thereof. In a second aspect of the present invention, a process for preparing a catalyst is provided, which includes: (A) mixing metal compounds, at least one of which is an oxygen-containing compound, and water, to form an aqueous solution; (B) removing the water from the aqueous solution, to obtain a catalyst precursor; and () calcining the catalyst precursor at a temperature of 400 to 800 ° C, under an inert atmosphere, in which this inert atmosphere does not flow on the catalyst precursor, to form a catalyst, having the formula: AaMmNnXx0oen that: 0.35 < a < 0.97, 0.045 < m < 0.37, 0.020 < 'n < 0.27, 0.005 < x < 0.35, and o is dependent on the oxidation state of the other elements, and A is selected from: Mo, W, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected from Te, Bi, Sb, and their mixtures; and X is selected from Nb, Ta, Zr, and their mixtures.

In a third aspect, the present invention provides a catalyst, which includes a compound of the formula: AaMmNnXx0oen that: 0.25 < a < 0.98, 0.003 < m < 0.5, 0.003 < n < 0.5, 0.003 < x < 0.5, and o is dependent on the oxidation state of the other elements, and A is selected from: Mo, W, Fe, Nb, Ta, Zr, Ru, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected from Te, Bi, Sb, Se, and mixtures thereof; and X is selected from Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, Ce, and mixtures thereof; wherein the catalyst has a surface area of 2 to 10 m2 / g, as determined by the BET method. In additional aspects of the present invention, a catalyst prepared by the catalyst preparation processes of the present invention and the processes for preparing aldehydes or unsaturated carboxylic acids, including subjecting an alkane to catalytic oxidation, in the presence of a catalyst, prepared according to the process of the present invention.

Figure 1 illustrates a scanning electron micrograph (SEM) of the catalyst formed according to Example 1. Figure 2 shows that the catalyst calcined under air (Example 3) has larger crystals than the catalyst formed under argon. The calcined catalyst under the air has a smooth surface and is less porous than the catalyst formed under the argon. As used herein, the term "(meth) acrylic acid" is intended to include both methacrylic acid and acrylic acid within its scope. In a similar manner, the expression of "(meth) acrylates" is intended to include both methacrylates and acrylates within its scope. As used herein, the terminology of "alkane (C3-C8) "means a straight or branched chain alkane, having from 3 to 8 carbon atoms per molecule of alkane As used herein, the term" mixing "means that it includes within its scope, all the forms of mixtures, which include, but are not limited to, simple mixtures, as well as combinations, alloys, etc. For the purposes of this application, the "% conversion" is equal to (moles of alkane consumed / moles of alkane supplied) x 100; "% selectivity" is equal to (moles of the desired carboxylic acid or unsaturated aldehyde formed / moles of the alkane consumed) x 100; and "% yield" is equal to (moles of the desired carboxylic acid or unsaturated aldehyde formed / moles of alkane supplied) x (carbon number of the desired carboxylic acid or unsaturated aldehyde formed / carbon number of the alkane supplied) x 100. For For purposes of this application, "solution" means that more than 95 percent of the metal solid added to a solvent dissolves. It will be understood that the greater the amount of the metal solid is not - initially in solution, poorer will be the performance of the catalyst derived from it. As mentioned before, a process for preparing a catalyst is disclosed. In a first stage of the process, a "solution is formed by mixing metal compounds, at least one of which contains oxygen, and less a solvent, in appropriate amounts, to form the solution. Generally, metal compounds contain the elements: A, M, N, X and O. In one embodiment, A is selected from Mo, W, Fe, Nb, Ta, Zr, Ru and their mixtures; M is selected from V, Ce, Cr and their mixtures; N is selected from Te, Bi, Sb, Se and their mixtures; and X is selected from Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb., Bi, B, In, Ce and their mixtures. In a preferred embodiment, A is selected from Mo, and mixtures thereof; M is selected from V, Ce, Cr and their mixtures; N is selected from Te, Bi, Sb and their mixtures; and X is selected from Nb. Ta, Zr and their mixtures. In a more preferred embodiment, A is Mo, M is V, N is Te and X is Nb. Suitable solvents include water, alcohols include, but are not limited to, methanol, ethanol, propanol, and diols, etc., as well as other polar solvents known in the art. In general, water is preferred. Water is any water suitable for use in chemical synthesis, which includes, without limitation, distilled water and deionized water. The amount of water present is that amount sufficient to keep the elements substantially in solution for a period long, to avoid or minimize the segregation of the composition and / or phases, during the preparation stages. Therefore, the amount of water will vary according to the amounts and the solubility of the combined materials. However, as noted above, the amount of water must be sufficient to ensure that an aqueous solution is formed and not an aqueous paste at the time of mixing. Once the aqueous solution is formed, the water is removed by any suitable method, known in the art, to form a catalyst precursor. such methods include, without limitation, vacuum drying, freeze drying, spray drying, rotary evaporation and air drying. Vacuum drying is generally carried out at pressures ranging from 10 to 500 mm Hg. Freeze drying typically leads to the freezing of the solution, using, for example, liquid nitrogen, and drying the frozen solution under vacuum. Spray drying is generally carried out under an inert atmosphere, such as nitrogen or argon, with an inlet temperature ranging from 125 to 200 ° C and an outlet temperature ranging from 75 to 150 ° C. The Rotary evaporation is generally carried out at a bath temperature of 25 to 90 ° C and at a pressure of 10 to 760 mm Hg, preferably at a bath temperature of 40 to 90 ° C and a pressure of 10 to 350 mm Hg, more preferably 40 to 60 ° C and a pressure of 10 to 40 mm Hg. Air drying occurs at temperatures ranging from 25 to 90 ° C. Rotary evaporation or air drying are generally preferred. Once obtained, the catalyst precursor is calcined under an inert atmosphere. This inert atmosphere may be of any material that is substantially inert, ie does not react or interact with, the catalyst precursor. Suitable examples include, without limitation, nitrogen, argon, xenon, helium or mixtures thereof. Preferably, the inert atmosphere is argon or nitrogen, more preferably argon. This inert atmosphere may flow over the surface of the catalytic precursor or may not flow (a static environment). It is important to understand that by atmosphere that does not flow it is understood that the inert gas is not allowed to flow over the surface of the catalyst precursor. It is preferred that the inert atmosphere does not flow over the surface of the catalyst precursor. However, when the inert atmosphere does not flow over the surface of the catalyst precursor, the flow rate can vary over a wide range, for example, at a space velocity of 1 to 500 hr. "1 Calcination is typically done at a temperature of 350 to 850 ° C, preferably 400 to 700 ° C, more preferably from 500 to 640 ° C. Calcination is typically carried out for a suitable period of time to form the catalyst In one embodiment, calcination is carried out for 0.5 to 30 hours, preferably 1 to 25 hours and more preferably 1 at 15 o'clock With the calcination, a catalyst is formed, which has the formula: AaMmNnXx0oen that: A, M, B and X are as described above The molar ratios of a, m, n and x are typically: 0.25 <; a < 0.98, 0.003 < m < 0.5, 0.003 < n < 0.5, 0.003 < x < 0.5 The molar ratio of o, ie the amount of oxygen (O) present, is dependent on the oxidation state of the other elements in the catalyst. Without However, typically or it is from 3 to 4.7, based on the other elements present in the catalyst. Another aspect of the present invention relates to a catalyst for making an unsaturated aldehyde or a carboxylic acid from an alkane, prepared by the process of the present invention. The catalyst is prepared as described above. This catalyst can be used as a solid catalyst alone or can be used with a suitable support such as, without limitation, silica, alumina, titania, aluminosilicate, diatomaceous earth or zirconia. The configuration of the catalyst can be any suitable and will depend on the particular application of the catalyst. In a similar manner, the particle size of the catalyst can be any suitable particle size, depending on the particular use of the catalyst. A further aspect of the present invention relates to a process for preparing an unsaturated aldehyde and a carboxylic acid, including subjecting an alkane to a catalytic oxidation, in the presence of a catalyst prepared according to the present invention.

The starting materials are generally one or more alkane gases and at least one gas containing oxygen. It is preferred that the starting materials also include water vapor. Therefore, a gas of the starting material is supplied to the system, which includes a mixture of gases of at least one alkane and water vapor. At least one gas containing oxygen can be included in the mixture or be supplied separately. Likewise, a dilution gas, such as an inert gas, which includes, without limitation, nitrogen, argon, helium, water vapor or carbon dioxide, may also be included. The dilution gas can be used to dilute the starting material and / or adjust the space velocity, the partial pressure of the oxygen, and the partial pressure of the water vapor. Suitable molar ratios of the alkane / oxygen / dilution gas / water in the gas mixture of the starting material are known in the art, as is the charge ratio of the alkane / air / water vapor. For example, suitable regimens are described in U.A. Patent No. 5,380,933.

The starting material, the alkane, is generally any alkane suitable for the oxidation of gas phase in an unsaturated aldehyde or carboxylic acid. In general, the alkane is a C3 to C8 alkane, preferably propane, isobutane or n-butane, more preferably propane or isobutane, especially preferred, propane. Also, in another embodiment, the alkane may be a mixture of alkanes including C3 to C8 alkanes, as well as lower alkanes, such as methane and ethane. - This at least one gas containing oxygen used, can be pure oxygen gauze, a gas containing oxygen, such as air, a gas enriched with oxygen, or a mixture thereof. In a preferred embodiment, the starting material is a mixture of propane, air and water vapor gases. The mixture of starting gases is subjected to catalytic oxidation, in the presence of the catalyst of the present invention. The catalyst can be in a fluidized bed or fixed bed reactor. The reaction is generally conducted under atmospheric pressure, but can be conducted under elevated or reduced pressure. The reaction temperature is generally from 200 to 550 ° C, preferably from 300 to 480 ° C, more preferably from 350 to 440 ° C. The space velocity of the gas is generally from 100 to 10,000 hr "1, preferably from 300 to 6,000 hr" 1 and more preferably from 300 to 3,000 hr "1. Likewise, in the method of the present invention, it will be understood that form an unsaturated aldehyde For example, when propane is the starting alkane, acrolein can be formed, and when isobutane is the starting alkane, methacrolein can be formed The abbreviations used in this application are: ° C = Celsius degrees mm = millimeters Hg = mercury g = grams cm = centimeters mmoles = millimoles% = percent by weight ml / min = milliliters per minute N2 = nitrogen The following examples illustrate the process of the present invention. of the starting material used, if there is no segregation of the composition, or if there is no loss of certain elements during the preparation stages, all catalyst samples prepared as follows, must have an empirical formula from M? Vo.3Te0.23Nbo.? O-o.? 2On, where n is determined by the oxidation state of the other elements. Aqueous solutions or pastes containing the desired metal elements are prepared by heating the appropriate compounds in water, at a temperature ranging from 25 to 95 ° C. When necessary, aqueous solutions or pastes are cooled to temperatures ranging from 25 to 60 ° C. The water was then removed from the aqueous solutions or pastes by the appropriate drying method, at pressures ranging from 760 mm / Hg to 10 mm / Hg.

Example 1 Solution of the Catalytic Precursor, Dried by Rotary Evaporation and. Calcinada Baj or Argó. Fluid-free atmosphere In a flask, which contains 420 g of water, 25.7 g of ammonium heptamolybdate tetrahydrate (Aldrich Chemical Company), 5.1 g of ammonium metavanadate (Aldrich Chemical Company) and 7.7 g of telluric acid were dissolved ( Aldrich Chemical Company), under heating at 80 ° C. After cooling to 39 ° C, 114.6 g of an aqueous solution of niobium oxalate (Referencie Metals Company), containing 17.34 mmole of niobium, were mixed, get a solution The water in this solution was removed by means of a rotary evaporator, with a hot water bath at 50 ° C and 28 mm / Hg, to obtain 44 g of the precursor solid. 20 g of the solid of the catalyst precursor was calcined in a covered crucible, previously purged with argon, medium without flow, at 600 ° C, for 2 hours. The furnace had previously been heated to 200 ° C and remained so for one hour, then staggered at 600 ° C. During the calcination, the covered crucible was inside a covered deck, with a space velocity of Ar of 57 hr "1. Due to the covered crucible, the argon did not flow on the surface of the precursor, but rather served to ensure that the atmosphere outside the crucible remained argon, the atmosphere inside the crucible remained argon and the gases released from the catalyst.The catalyst, thus obtained, was pressed in a mold and then broke and sieved to 10-20 mesh size granules. 10 g of the granules were packed in a stainless steel U-tube reactor with an internal diameter of 1.1 cm for the gas phase propane oxidation.This oxidation was conducted at a temperature of the reactor bath (molten salt). ) of 390 ° C, a load ratio of propane / air / water vapor of 1/15/14, and a space velocity of 1,200 hr "1. The reactor effluent was condensed to separate the liquid phase (the damnable material) and the gas phase. was analyzed by gas chromatography ("GC") to determine the conversion of propane.The liquid phase was also analyzed by the GC for the performance of acrylic acid.The results are shown in Table 1. The catalyst was also analyzed by X-ray diffraction to determine its crystalline structure The results are shown in Table 5. The surface of the catalyst was also analyzed by scanning electron microscopy.The results are shown in Figure 1. This Figure 1 shows that the catalyst formed, according to Example 1, is very porous The surface area of BET was determined to be 5.23 m2 / g.

Example 2 Catalyzed Precursor Solution, Dried by Rotary Evaporation and Calcinated under an Atmosphere. Without Flow, of Ni trogen. 43 g of the catalyst precursor were prepared in the same manner as in Example 1. 21 g of the catalyst precursor solid was calcined in a covered crucible, pre-purged with nitrogen, with no flow environment, at 600 ° C, for 2 hours. hours. During the calcination, the crucible was placed inside a bucket covered with a nitrogen spatial velocity of 57 to 283 hr "1. The catalyst, thus obtained, was pressed in a mold and then broken and sieved into granules of a mesh. 10-20.12 g of the granules were packed in a stainless steel U-tube reactor, with internal diameter of 1.1 cm, for the oxidation of the gas phase propane. 390 ° C reactor, a propane / air / water vapor charge ratio of 1/15/16 and a space velocity of 1.565 hr-1. The effluent from the reactor was condensed to separate the liquid phase and the gas phase. The gas phase was analyzed by GC to determine the conversion of propane. The liquid phase was also analyzed by GC for the yield of acrylic acid. The results are shown in Table 1.

Example 3 Catalyst Precursor Solution, Rotary Evaporated and Calcinated Dried Under an Air Flow Atmosphere 20 g of the catalyst precursor of Example 1 was calcined under air at 600 ° C for 2 hours. The catalyst, thus obtained, was pressed into a mold and then broken and sieved into granules of a 10-20 mesh. 10 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.1 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / water vapor charge ratio of 1/15/13 and a space velocity of 1,200 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 1. The catalyst was also analyzed by X-ray diffraction to determine its crystalline structure, the results are shown in Table 5. The surface of the catalyst It was also analyzed by scanning electron microscopy. The results are shown in Figure 2. The surface area of BET was determined to be 0.87 m / g.

Example 4 Catalyst Precursor Solution, Air-dried and Calcinated Under an Argon Atmosphere, No Flow Following the same procedure as in Example 1, a solution containing Mo, V, Te and Nb was prepared. The solution was emptied into a container with a large flat bottom. The solution gelled and dried slowly under atmospheric pressure and at room temperature. A solid catalyst precursor was obtained and calcined in the same manner as in Example 1. 11 g of the granules, thus obtained, were packed in a stainless steel U-tube reactor, with an internal diameter of 1.1 cm, for the oxidation of propane gas phase. Oxidation was conducted with a reactor bath temperature of 391 ° C, a propane / air / water vapor charge ratio of 1/15/14 and a space velocity of 1,200 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane. The liquid phase was also analyzed by GC for the yield of acrylic acid. The results are shown in Table 1.

EXAMPLE 5 Aqueous Paste of the Catalyst Precursor, Dried by Rotary Evaporation and Calcinated Under an Argon Atmosphere, Without Flow In a beaker, containing 650 g of water, 158 g of ammonium heptamolybdate tetrahydrate, 31.4 g of metavanadate were dissolved. ammonium and 47.2 g of telluric acid under heating at 85 ° C. After cooling to 45 ° C, 814 g of an aqueous solution of niobium oxalate, containing 111 mmole of niobium, was added to the solution, resulting in 1.750 g of an aqueous paste.

A quarter of the aqueous paste was placed in a rotary evaporator with a hot water bath to remove the water (as in Example 1), which resulted in 67 g of the catalyst precursor solid. 25 g of the solid of the precursor was calcined in a medium without flow, inert, at 600 ° C, during 2 hours (as in Example 1). The catalyst, thus obtained, was pressed into a mold and then broke and sifted to granules with a mesh size of 10-20. Some of the granules (12.8 g) were packed in a stainless steel U-tube reactor with an internal diameter of 1.1 cm for the gas phase propane oxidation. This oxidation was conducted at a reactor bath temperature (molten salt) of 389 ° C, a propane / air / water vapor charge ratio of 1/15/16, and a space velocity of 1.286 hr "1. The effluent from the reactor was condensed to separate the liquid phase (the damnable material) and the gas phase.The gas phase was analyzed by gas chromatography ("GC") to determine the conversion of the propane. analyzed by GC for the performance of acrylic acid.The results are shown in Table 1. The catalyst and the catalyst precursor were analyzed by Plasma Atomic Emission Spectroscopy, Inductively Coupled ("ICP-AES") for Te, Mo, V and Nb) The results are shown in Tables 2 and 3. The catalyst was also analyzed by X-ray diffraction to determine the crystal structure. The results are shown in Table 5.

EXAMPLE 6 Aqueous Paste of the Catalyst Precursor, Dried by Rotary Evaporation and Calcinated Under a Ni-Tomogen Flow Atmosphere 25 g of the same solid of the catalyst precursor "of Example 5, were calcined in a quartz calcination flask with a spatial velocity of 780 hr nitrogen "at 600 ° C for 2 hours. The catalyst, thus obtained, was pressed into a mold and then broken and sieved into granules of a 10-20 mesh. 14 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.0 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 389 ° C, a propane / air / water vapor charge ratio of 1/15/15 and a space velocity of 1.241 hr "1. The reactor effluent" condensed to separate the liquid phase and the gas phase. The gas phase was analyzed by GC to determine the conversion of propane. The liquid phase was also analyzed by GC for the yield of acrylic acid. The results are shown in Table 1. The catalyst was analyzed in the Te content by ICP-AES.

Results are shown in table 2.

EXAMPLE 7 Aqueous Paste of the Catalyst Precursor, Dried by Freeze Drying and Calcinated Under Argon 290 g of the aqueous paste, prepared in the Example , were frozen, drop by drop, in a liquid nitrogen bath, then dried in vacuo, to obtain 43 g of a powdery solid. 27 g of the catalyst precursor solid was pressed into a mold and then broken and sieved into granules of a 10-20 mesh, then calcined in an argon-free environment at 600 ° C, for 2 hours. The catalyst, thus obtained, was sieved to a mesh size of 10-20 again to obtain a sample of granules. 15 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.0 cm, for the oxidation of the gas phase propane. Oxidation was conducted with a reactor bath temperature of 389 ° C, a propane / air / water vapor charge ratio of 1/15/16 and a space velocity of 1.286 hr "1. The reactor effluent was condensed To separate the liquid phase and the gas phase, the gas phase was analyzed by GC to determine the conversion of the gas phase. propane. The liquid phase was also analyzed by GC for the yield of acrylic acid. The results are shown in Table 1. The catalyst was also analyzed by x-ray diffraction to determine its crystalline structure. The results are shown in Table 5.

Example 8 Catalyst for Precipitation of Aqueous Paste, Precipitated Air-dried and Calcinated Under an Atmosphere, Without Flow, from Argon 575 g of the aqueous paste, prepared in Example 5, were filtered through a filter paper fixed, to separate the solid from the mother liquor. The solid was dried under atmospheric pressure at room temperature, which results in 24 g of the catalytic precursor. This catalytic precursor was calcined and prepared in the same manner as in Example 1. 12 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.1 cm, for the oxidation of propane from gas phase. Oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / water vapor charge ratio of 1/15/17 and a speed spatial of 1,333 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase.The gas phase was analyzed by GC to determine the propane conversion.The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 1. The catalyst was also analyzed by ICP-AES for the relative content of the metal.The results are shown in Table 3. The catalyst was analyzed by x-ray diffraction to determine Its crystalline structure The results are shown in Table 5.

E 9 Fluid Catalyst Mother of the Aqueous Paste, Mother liquor Dried by Rotary Evaporation and Calcinated under an Atmosphere, Without Flow, of Argon. The mother liquor of Example 8 was dried by rotary evaporation, in the same manner as in Example 1, yielding 62 g of the solid catalyst precursor. 20 g of the catalytic precursor was calcined and prepared in the same manner as in Example 1. 13 g were packed in a stainless steel U-tube reactor, with internal diameter of 1.1 cm, for the oxidation of gas phase propane. The oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / water vapor charge ratio of 1/15/17 and a space velocity of 1.333 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 1 The catalyst was analyzed by ICP-AES for the relative content of the metal.The results are shown in Table 3. The catalyst was also analyzed by x-ray diffraction to determine its crystalline structure.The results are shown in Table 5.

EXAMPLE 10 Solution of the Precursor Dried by Rotary Evaporation and Calcinated Under Argon ~ 61 g of the catalytic precursor were prepared in the same manner as in Example 1. 25 g of this solid was calcined under the same conditions of Example 1, supply 17.7 g of solid. This solid was pressed into a mold and then broken and sieved into granules of a 10-20 mesh. 14 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.0 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / steam-water charge ratio of 1/15/13 and a space velocity of 1.161 hr. "1 The reactor effluent was It condensed to separate the liquid phase and the gas phase.The gas phase was analyzed by GC to determine the conversion of propane.The liquid phase was also analyzed by GC for the yield of acrylic acid.The results are shown in Table 1 The catalyst was analyzed in the Te content by ICP-AES The results are shown in Table 2.

Example 11 Catalyst Precursor Solution, Dried by Rotary Evaporation and Calcinated Under an Argon Flow Atmosphere g of the catalyst precursor of Example 10 were calcined in a quartz calcination flask, with an argon space velocity of 540 hr "1, at 600 ° C for 2 hours, to supply 16.8 g of the solid. obtained was pressed in a mold and then broke and sieved to granules of a mesh of 10-20. 14 g of the granules were packed in a stainless steel U-tube reactor, with internal diameter of 1.1 cm, for the oxidation of gas phase propane Oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / water vapor ratio of 1/16/16 and a space velocity of 1.241 hr "1 . The effluent from the reactor was condensed to separate the liquid phase and the gas phase. The gas phase was analyzed by GC to determine the conversion of propane. The liquid phase was also analyzed by GC for the yield of acrylic acid. The results are shown in Table 1. The catalyst was analyzed in the Te content by ICP-AES. Results are shown in table 2.

Example 12 Catalyst Precursor Solution, Dried by Rotating and Calcinated Evaporation Under one atmosphere. Without Flow, Argon, With Tri-Turing After Calcination. g of the catalyst were prepared in the same manner as in the Example. The solid was ground to a fine powder in a mortar and then dispersed with 66 g of water to obtain an aqueous paste. Water, in this aqueous paste, it was removed by means of rotary evaporation to recover the solid, which was then calcined again under the same conditions to supply 19.4 g of the solid. This solid was pressed into a mold and then broken and sieved into granules of a 10-20 mesh. 13 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.1 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 390 ° C, a propane / air / water vapor charge ratio of 1/15/15.4 and a space velocity of 1,241 hr -1. The effluent from the reactor was condensed to separate the liquid phase and the gas phase. The gas phase was analyzed by GC to determine the conversion of propane. The liquid phase was also analyzed by GC for the performance of acrylic acid. The results are shown in Table 1.

Table 1 Pre-Drying Example Drying Calcination Conversion Selectivity Yield% 1 1 rotavap solution Ar without flow 69 55 38 2 rotavap solution N2 without flow 49 57 28 3 air rotavap solution 0 - 0 4 air solution Ar without flow 49 53 26 water paste rotavap Ar without flow 43 53 23 6 aqueous paste rotavap flow of N2 68 17 12 7 aqueous paste for Ar without flow 19 49 9 freezing 8 air precipitate Ar without flow 4 75 3 aqueous paste 9 rotavap mother liquor Ar without flow 3 33 1 aqueous paste 10 rotavap solution Ar without flow 59 48 28 11 solution rotavap flow of Ar 57 23 13 12 rotavap solution Ar without flow 71 59 52 conversion (%) = percent of propane converted selectivity (%) = selectivity of conversion of propane to acrylic acid in percent yield (%) = yield of acrylic acid in percent rotavap = rotary evaporation.

Comparison data of Table 1 Comparison of Preparation Variables Performance Ratio Example 1/3 inert, no flow / air 38/0 = infinity Example 1/5 solution / aqueous paste 38/23 = 165% Example 10/11 without flow / with flow 28/13 = 215% Example 5/7 rotavap / freeze drying 23/9 = 256% The data in Table 1 above, indicates that a prepared catalyst is much more effective in converting propane to acrylic acid, when it is calcined under an inert, non-flowable atmosphere, than when it is calcined under air (see Examples 1 and 3) . Also, the data indicates that a prepared catalyst is more effective in converting propane to acrylic acid when the catalyst is formed from a solution, rather than an aqueous paste (see Examples 1 and 5). The data in Table 1 also indicates that the catalyst prepared is more effective in converting propane to acrylic acid when the catalyst is calcined under an atmosphere without flow rather than a flow atmosphere (see Examples 10 and eleven) . Finally, the data in Table 1 indicate that a prepared catalyst is more effective in converting propane to acrylic acid, when the catalyst is initially dried by rotary evaporation, rather than by freeze drying (see Examples 5 and 7).

Table 2 Example% by weight of Te in the Catalyst 5 13 6 9.8 (75% of the theory) 13 Mo? Vao.3Teo.23Nb0.1104.5 10 13 11 10 The data in Table 2 show the loss of 23 to 25 weight percent of the Te in the catalyst, after calcination in a flow environment (see Examples 6 and 11), while in an environment without flow (Examples 5 and 10) the percentage by weight of Te is comparable to the calculated theoretical value. This indicates that the Catalyst is better formed in an environment without flow.

Particularly, the loss of catalyst Te is shown when a flow environment is used during calcination. Therefore, it is postulated that the loss of the substituting metal results in lower yields, shown in Table 1, for calcined catalysts in a flowing environment.

Table 3 The data in Table 3 show that the elements are not equally distributed between the aqueous phase and the solid phase of the aqueous paste, when the catalyst is prepared from an aqueous paste. These result in the final catalyst having a phase segregation of the composition, therefore, is a less effective catalyst.

EXAMPLE 13 Aqueous Paste of Catalyst Precursor, Freeze-dried and Calcined Under a Ni-Trogen Flow Atmosphere In a beaker containing 650 g of water, 158 g of ammonium heptamolybdate tetrahydrate, 31.4 g of ammonium metavanadate were dissolved. and 47.2 g of telluric acid, heating to 60 ° C. This solution was mixed with 360 g of an aqueous solution of niobium oxalate, which contains 111 mmoles of niobium, to form an aqueous paste in a water bath of 50-60 ° C. Some of this aqueous paste (831 f) was frozen in a liquid nitrogen bath, then dried under vacuum to obtain a solid precursor powder catalyst. A portion of this solid catalyst precursor was pressed into a mold and then broken and sieved into 10-20 mesh granules, then calcined in an "N2" atmosphere, with a space velocity of 180-300 hr. 1, at 600 ° C, for 2 hours The catalyst, thus obtained, was sieved to a mesh size of 10-20 again. to obtain a sample of granules. 20 g of the granules were packed in a stainless steel U-tube reactor, with an inner diameter of 1.1 cm, for the oxidation of gas phase propane. The oxidation was conducted with a reactor bath temperature of 385 ° C, a propane / air / water vapor charge ratio of 1/15/13 and a space velocity of 1,125 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 4. The catalyst was also analyzed by x-ray diffraction to determine the crystal structure, the results are shown in Table 5.

EXAMPLE 14 Aqueous Paste of the Catalyst Precursor, Dried by Heat Evaporation and Calcinated Under a Ni Tragen Flow Atmosphere 416 g of the aqueous paste of Example 13 was stirred in an open cover in the same water bath, until the dryness, to obtain a solid of the catalyst precursor. The catalyst precursor solid was pressed into a mold and then broken and sieved into granules of a 10-20 mesh, then calcined and prepared in the same manner as in Example 10. The catalyst thus obtained was sieved to a mesh size of 10-20 again, to obtain a sample of granules. 24 g of the granules were packed in a stainless steel U-tube reactor, with an inner diameter of 1.1 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 385 ° C, a propane / air / water vapor charge ratio of 1/15/12 and a space velocity of 1.286 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 4. The catalyst was also analyzed by x-ray diffraction to determine the crystal structure, the results are shown in Table 5.

EXAMPLE 15 Aqueous Paste of Catalyst Precursor, Spray Dried and Calcined Under a Ni-Trogen Flow Atmosphere In a beaker containing 162 g of water, 39.5 g of ammonium heptamolybdate tetrahydrate, 7.9 g of ammonium metavanadate were dissolved and 11.8 g of telluric acid, heating to 68 ° C. This solution was mixed with 180 g of an aqueous solution of niobium oxalate (Advanced Materials. Compay), which contains 53.6 mmoles of niobium, to form an aqueous paste. This aqueous paste was spray dried in a small laboratory dryer by spraying, with nitrogen as the carrier gas, an inlet temperature of 162 ° C and an outlet temperature of 100-110 ° C, to result in a solid precursor of the powdered catalyst. A portion of this solid precursor was pressed into a mold and then broken and sieved into granules of a 10-20 mesh, then calcined in the same manner as in Example 10, to obtain 222 g of the catalyst in granules. " 20 g of the granules were packed in a stainless steel U-tube reactor, with an internal diameter of 1.1 cm, for the oxidation of the phase propane Of gas. Oxidation was conducted with a reactor bath temperature of 385 ° C, a propane / air / water vapor charge ratio of 1/15/14 and a space velocity of 1.161 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 4. The catalyst was also analyzed by x-ray diffraction to determine the crystal structure, the results are shown in Table 5.

Example 16 slurry catalyst precursor, freeze dried and calcined under an atmosphere Flow Ni trógeno an aqueous slurry in the same manner as in Example 15. This slurry was frozen in a liquid nitrogen bath drop was prepared per drop, then dried under vacuum, to obtain a solid of the powdered catalyst precursor. A portion of this solid catalyst precursor was calcined in the same manner as in the Example 13, which resulted in catalyst granules. 19 g of the granules were packed in a stainless steel U-tube reactor, with an inner diameter of 1.1 cm, for the oxidation of gas phase propane. Oxidation was conducted with a reactor bath temperature of 384 ° C, a propane / air / water vapor charge ratio of 1/15/12 and a space velocity of 1.440 hr "1. The reactor effluent was condensed to separate the liquid phase and the gas phase The gas phase was analyzed by GC to determine the conversion of propane The liquid phase was also analyzed by GC for the yield of acrylic acid The results are shown in Table 4.

Table 4 Pre-Drying Example Drying Calcination Conversion Selectivity Performance 13 aqueous paste freezing flow of N2 13 25 3.3 14 aqueous paste evaporation flow of N2 1 0 by heat 15 aqueous paste spray flow of N2 51 1.6 0.8 16 aqueous paste flow freezing of N2 8 27 2.1 conversion (%) = converted propane percent selectivity (%) = selectivity of conversion of propane to acrylic acid in percent yield (%) = the yield of acrylic acid in percent Comparisons with the Data in Table 4 Comparison of Preparation Variables Performance Ratio Example 13/14 Freeze drying / evaporation by heat 3.3 / O - > infinity Example 16/15 freeze drying / spray drying 2.1 / 0.8 = 263% Table 5 Example 22.1 ° 28.2 ° 36.2 ° 45.2 ° 50.0 ° 1 X X X X X 3 0 0 0 0 or 5 X X X X X 7 X X X X X 8 X X 0 X or 9 X X 0 or X 13 X X X X X 14 X X X 0 X 15 X 0 0 X 0 It is known that the effective catalysts of this invention have x-ray diffraction crests at a diffraction angle of 2? of 22.1 °, 28.2 °, 36.2 °, 45.2 ° and 50. 0 °. The data in Table 5 above indicate that an effective catalyst is not formed when it is calcined under air, dried by heat evaporation or spray dried, or that originates from the precipitated phase or from the mother liquor phase of the pulp. watery The above examples demonstrate that the process of this invention is more effective in converting propane to acrylic acid than any known process.

Claims (16)

1. CLAIMS 1. A process for preparing a catalyst, this process comprises: (A) mixing metal compounds, at least one of which is an oxygen-containing compound, and at least one solvent, to form a solution; (B) removing the solvent from the solution, to obtain a catalyst precursor; and (C) calcining this catalyst precursor at a temperature of 350 to 850 ° C, under an inert atmosphere, to form a catalyst having the formula: AaMmNnXx0oen that: 0.25 < a < 0.98, 0.003 < m < 0.5, 0.003 < n < 0.5, 0.003 < x < 0.5, I is dependent on the oxidation state of the other elements, and A is selected from: Mo,, "Fe, Nb, Ta, Zr, Ru, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected from Te, Bi, Sb, Se, and mixtures thereof, and X is selected from Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, Ce, and their mixtures 2. The process, according to the claim 1, wherein the catalyst comprises: 0.35 < a < 0.87, 0.045 < m < 0.37, 0.020 < n < 0.27 and 0.005 < x < 0.35. 3. The process, according to claim 1, wherein the catalyst is calcined at a temperature of 400 ° C to 800 ° C. 4. The process, according to claim 1, wherein A is selected from Mo, W and their mixtures; M is selected from V, Ce, Cr and their mixtures; N is Te, Bi, Sb and their mixtures; and X is Nb, Ta, Zr and their mixtures. 5. The process, according to claim 1, wherein A is Mo, M is V, N is Te and X is Nb. 6. The process, according to the claim 1, in which the inert atmosphere comprises at least one of argon and nitrogen. The process, according to claim 1, wherein the inert atmosphere does not flow on the surface of the catalyst precursor. The process, according to claim 1, wherein the solvent is removed by a process selected from rotary evaporation, vacuum drying, air drying and freeze drying. 9. A process to prepare a catalyst, this process includes: (A) mixing metal compounds, at least one of which is an oxygen-containing compound, and water, to form an aqueous solution; (B) removing the water from the aqueous solution, to obtain a catalyst precursor; and (C) calcining the catalyst precursor at a temperature of 400 to 800 ° C, under an inert atmosphere, in which this inert atmosphere does not flow over the catalyst precursor, to form a catalyst, having the formula: AaMmNnXx0oen that: 0.35 < a < 0.97, 0.045 < m < 0.37, 0.020 < n < 0.27, 0.005 < x < 0.35, and o is dependent on the oxidation state of the other elements, and A is selected from: Mo, W, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected from Te, Bi, Sb, and their mixtures; and X is selected from Nb, Ta, Zr, and their mixtures. 10. A catalyst prepared according to the process of claim 1. 11. The catalyst according to claim 9, wherein said catalyst comprises: 0.35 < a < 0.87, 0.45 < m < 0.37, 0.020 < n < 0.27 and 0.005 < x < 0.35. 12. The catalyst according to claim 9, wherein A is Mo, M is V, N is Te and X is Nb. 13. A catalyst prepared according to the process of claim 9. 14. A process for preparing an unsaturated aldehyde or carboxylic acid, comprising subjecting an alkane to catalytic oxidation, in the presence of a catalyst, prepared by the process of claim 1. 15. A process for preparing an unsaturated aldehyde or carboxylic acid, comprising subjecting an alkane to a catalytic oxidation, in the presence of a catalyst, prepared by the process of claim 9. 16. A catalyst comprising a composed of the formula: AaMmNnXx0oen that: 0.25 < a < 0.98, 0.003 < m < 0.5, 0. 003 < n < 0.5, 0.003 < x < 0.5, and o is dependent on the oxidation state of the other elements, and A is selected from: Mo, W, Fe, Nb, Ta, Zr, Ru, and their mixtures; M is selected from: V, Ce, Cr, and their mixtures; N is selected of Te, Bi, Sb, Se, and their mixtures; and X is selected from Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, Ce, and mixtures thereof; wherein the catalyst has a surface area of 2 to 10 m2 / g, as determined by the BET method.