MXPA00008079A - Copper-containing materials - Google Patents

Abstract

Copper/alumina compositions for uses as e.g. catalysts are made by impregnating a porous transition alumina support with an aqueous solution of a copper ammine carbonate complex, draining off any excess of the impregnating solution, and then heating the impregnated support to a temperature above 80°C to decompose the complex thereby depositing a basic copper carbonate compound on the surfaces of the pores of the transition alumina support. After reduction, the composition have a high copper surface area, expressed per unit weight of copper in the composition.

Description

MATERIALS CONTAINING COPPER DESCRIPTION OF THE INVENTION This invention relates to copper-containing materials. Compositions containing copper, where some or all of the copper is in the form of elemental copper, or in the form of oxide, that is to say as cuprous and cuprous oxides, or in the form of other copper species, for example sulfides, carbonates Basic and similar, they are widely used in industrial processes as catalysts or sorbents. For example, compositions in which some or all of the copper is in the elemental form are frequently used as catalysts for reactions involving hydrogen. As examples, mention may be made of the change reaction wherein the carbon monoxide is reacted with steam to form carbon dioxide and hydrogen; the alcohol synthesis reactions wherein a mixture of hydrogen and carbon monoxide and / or carbon dioxide is reacted to form methanol or higher alcohols; the hydrogenation reactions; and hydr ogen es of esters. Compositions in which some or all of the copper is in the form of copper and elemental, copper oxides, copper hydroxide or basic cupric carbonate, can be used as sorbents for purification of gases and liquids to remove contaminants such as sulfur compounds. Compositions in which copper is in the form of copper sulfides can be used as sorbents for the removal of contaminants such as arsenic and mercury compounds from gases and liquids. For such applications it is generally desirable that the copper species be present in a highly dispersed cold so that the active species readily contacts the reagents or the material to be treated. The degree of dispersion of copper species can be assessed by determining the surface area exposed to copper (after reduction of copper species to elemental copper) per gram of copper. A high surface area of copper per gram of copper implies a high degree of dispersion. The copper surface area is determined readily by the decomposition method of nitrous oxide, for example as described by Evans et al in "Applied Catalysis", 7, (1983), pages 75-83 a particularly suitable technique is described in EP 0 202 824.

It is known that compositions having, with reduction, a high metal surface area per gram of metal can be made by impregnating a transition alumina support with amine carbonate solutions, followed by heating to decompose the carbonate. of amine. Thus, EP 0 092 878 describes the production of nickel on alumina compositions and WO 96 04 072 describes the production of analogous cobalt compositions. However, the degree of dispersion of a metal obtained by impregnation of a support, such as alumina, with a solution of a salt or metal complex, depends on the ease of decomposition of the complex or the solubility of the salt. If the salt is too soluble or the complex is too stable, agglomerates of the metal species are subject to formation rather than a thin layer of the decomposition products on the surfaces of the pores of the alumina support. Such agglomerates will give, with reduction to the metal, materials having a relatively low metal surface area. The nickel and cobalt amine carbonate complexes as used in the aforementioned EP 0 092 878 or WO 96 04 072 have a relatively low stability. In this way, they decompose very easily. It has been found that although the amine-ca-tertiary or cupric complexes are significantly different and are much more stable than the cobalt or nickel analogues, surprisingly copper materials of high surface area can be obtained by this route. While cobalt and nickel form hexa-amine complexes, copper forms tetr-amine complexes. The complex constants for ammoniacal copper, cobalt and nickel complexes are as follows: As the composition is heated to decompose the amine complex, the cobalt and nickel materials readily precipitate when only some of the ammonia has separated. On the other hand, when copper complexes are heated since they are much more stable, copper would be expected to remain more in the solution during the evaporation of water and ammonia and would be prone to unequal deposition in the places where the last of the water it will be removed, and therefore cause aggregates of the copper composition more than the desired thin coating on the pores of the alumina support. Indeed, in EP 0 259 911 it was proposed to make catalysts of 1 / a-1 metal by combining an ammoniacal solution of a salt such as a metal carbonate with an aqueous solution of an aluminum compound and heating the mixture to boiling, or near boiling to precipitate a mixed basic carbonate, metal, and aluminum. While this method gave compositions which, when reduced, have a high metal surface area per gram of metal when the metal is nickel, the metal surface area was only 1-20 m2 per gram of metal when the metal It was copper. Accordingly, the present invention provides a process for the manufacture of a composition comprising a copper compound supported on a porous transition alumina comprising impregnating a porous support of transition alumina with an aqueous solution of an amine-ca-rbone complex. cupric, draining any excess solution to impregnate, and then heating the impregnated support to a temperature above 80 ° C to decompose the complex by depositing a basic copper carbonate compound on the surfaces of the pores of the alumina support of Transition. The transition alumina may be the gamma-alumina group, for example an eta-alumina or chi-alumina. These materials can be formed by calcining aluminum hydroxides at 400-750 ° C and generally have a BET surface area in the range of 150-400 m2 / g. Alternatively, the transition alumina may be of the delta alumina group which includes the high temperature forms such as delta and teta-alumina which may be formed by heating an alumina of the gamma group at a temperature above about 800 ° C. The aluminas of the delta group generally have a BET surface area in the range of 50-150 ml / g. Transitional aluminas contain less than 0.5 mole of water per mole of A1203, the actual amount of water depends on the temperature at which they have been heated. The support should be porous, preferably having a pore volume of at least 0.2 ml / g, particularly in the range of 0.3 to 1 ml / g. The support may be in powder form, but is preferably in the form of shaped units, for example, approximate spheres, pellets, cylindrical tablets, agglomerates. The shaped units preferably have a minimum dimension of at least 1 mm, and preferably have maximum and minimum dimensions in the range of 1 to 15 mm, preferably 3 to 10 m. The maximum dimension is preferably not more than 3 times the minimum dimension. Where a powdered alumina is employed, the alumina preferably has a heavy average surface diameter in the range of 1 to 100 μm. [The term surface mean diameter D [3,2], otherwise called the Sauter mean diameter, is defined by M. Alderliesten in the publication "A Nomenclature for Mean Particle Diameters"; Anal. Proc., Vol 21, May 1984, pages 167-172, and it is calculated from the particle size analysis which can be conveniently carried out by laser diffraction for example using a Malvern Mastersizer]. Alternatively the support can be in the. shape of a monolith, for example a honeycomb. In the latter case the honeycomb may be formed from a ceramic or metal support with a coating of the transition alumina. The amount of the cupric ammonium complex employed is preferably such that the composition has an atomic ratio of copper to aluminum in the range of 0.025 to 0.5., which corresponds to a copper content, in a binary composition of copper / alumina species, (after reduction of the copper species to elemental copper), from about 3 to 40% by weight. The shaped units of the invention can be made by impregnating the support with an aqueous solution of a cupric amine complex and, after draining any excess solution to be impregnated, then heating the impregnated support to decompose the amine complex. cupric carbonate. It is sufficient to heat at temperatures above about 80 ° C to decompose the cupric amine-to-cup, with the evolution of ammonia and carbon dioxide, to give a basic cupric carbonate. Heating temperatures above about 200 ° C, particularly above about 250 ° C, will cause the basic cupric carbonate to decompose to give a kind of copper oxide. The basic copper carbonate species, or the copper oxide species, can be converted to other copper species such as elemental copper by reduction or to copper sulphide by sulfurizing with a suitable sulfur compound, for example hydrogen sulfide or a solution, of a sulfur or ammonium or alkali polysulfide as is known in the art. The amine-carbonate or cupric solution can be made by dissolving basic cupric carbonate in an aqueous solution of ammonium carbonate it contains. additional ammonium hydroxide. The relative amounts should be such that the pH of the solution is in the range of 7-12, preferably 8-11. The solution contains preferably 1-5, particularly 2-4, especially 1.5-2.5 moles of the copper complex per liter. While the concentration of copper increases, then generally the proportions of carbonate ions relative to that of hydroxide ions in the basic cupric carbonate feed must be increased. Where the transition alumina is in the form of configured units, the configured units can be given multiple impregnations of the ammonium solution to a cupric heat by heating between impregnations to effect the decomposition of the cupric amine or cupric. By this method, a thin layer of the hydrocarbonat is deposited or on the pore surfaces of the configured transition alumina units. On the other hand, where alumina is employed in powder form, the transition alumina powder may be in the form of sludge with the appropriate amount of an aqueous solution of the cupric amine-carbonate complex to give a product of the copper content wanted. The alumina carrying the deposited copper compound is then filtered from an aqueous medium and heated. The resulting product can then be formed into shaped units, for example in pellet form, if desired. If it is desired to have the copper species in the form of the oxide, "the product can be calcined at a temperature in the range of 200-500 ° C, particularly at ~ 250-4 ~ 50 ° C. In some cases where the oxide It is desired, since the configured transition alumina units are given multiple impregnations, it may be desirable to calcinate the impregnated material between impregnations.Where it is desired to have the copper in the form of an elemental metal, the dried impregnated supports can be directly reduced with a suitable reducing agent, for example hydrogen, preferably diluted with an inert gas, at a temperature in the range of 150-400 ° C, particularly 200-300 ° C. Alternatively the reduction can be carried out after the conversion of the hydrocarbon Copper deposited in a copper oxide by calcination The conversion of metallic copper, copper oxide or copper hydrocarbon to other copper species, for example sulfides, can be effected by copper. known procedures. Depending on the pore volume of the support, and the concentration of the impregnation solution used, it is possible to produce compositions containing a quantity of copper species that varies over a wide range. For example, compositions having a content of copper species in the range of 3 to 40% by weight, expressed as copper, based on the combined weights of transition alumina and copper species, can be produced. For the compositions that have an atomic ratio of copper to aluminum above approximately 0.09, which corresponds to a copper content, in a binary composition of copper species / at the end (after the reduction of copper species to elemental copper) ) of about 10% by weight, multiple impregnations may be required. In the reduction of copper species, for example by hydrogen at temperatures in the range of 150-250 ° C, compositions having a copper surface area above 40 2 per gram of copper can be obtained. Preferably the copper surface area is above 50 m2, particularly above 60 m2 per gram of copper. Certain compositions of a copper species in a transitional alumina support containing substantial amounts of the copper species and having, in the reduction of the copper species, a high surface area of copper per gram of copper are new. Thus the copper compositions obtained by impregnating gamma alumina powder with copper nitrate followed by drying and calcination are described by Robinson et al in "Applied Catalysis", 44, (1988), pages 165-177. Figure 5 of this publication indicates that the maximum copper surface area, per gram of unreduced catalyst, was about 9 m / g and was given by a composition containing about 8% by weight of copper (Cu atomic ratio). / At approximately 0.07). This corresponds to a copper surface area of approximately 112 m2 per gram of copper. However, at higher copper contents, the copper surface area decreases. Thus at a copper content of approximately 24% by weight (atomic ratio Cu / Al approximately 0.25) the surface area was approximately 3 m per gram of unreduced catalyst, i.e. a copper surface area of approximately 12.5. m2 per gram of copper. It is desirable to produce copper compositions having, with the reduction of the copper species, a high copper surface area per gram of copper, and at the same time having a substantial copper content. In "ACS Division of Fuel Chemistry", 29, No. 5, (1984), pages 178-188, Chinchen et al. Lists copper / alumina catalysts for the synthesis of methanol having copper contents of 20%, 40% and 60% having copper surface areas of 11.7, 19.9 and 12.7 m2 per gram of unreduced catalyst respectively, which corresponds to the copper surface areas of approximately 58.5 m2, 49.8 m2 and 21.2 m2 per gram of copper. The production method of these cob re / alumina catalysts is not mentioned, but since they are compared with conventional copper / zinc oxide / alumina catalysts, for methanol synthesis they were presumably done by copri-ip ip ion as is normal for the catalysts for methanol synthesis, and not impregnating a preformed support of transition alumina. The copper catalysts having a copper surface area of above 35 m2 per gram are described in US Pat. No. 5,302,569. These are prepared by the copying of copper, zinc and aluminum compounds as per example carbonates followed by calcination. The proportion of alumina in the catalyzed is calcined is relatively small, in the range of 2 to 50 parts by weight per 100 parts by weight of copper oxide in the calcined composition. The examples describe the production of compositions which have, in the reduction, copper surface areas in the range of 54 to 76 m2 per gram of copper. Copper catalysts that have greater copper surface area, above 70 m2 per gram of copper, are described in US Pat. No. 4,863,894. These catalysts were made by copri-tracting copper compounds with zinc and, optionally, aluminum compounds as basic carbonates. and then reducing the copper species to the elemental form without heating the basic carbonate composition to temperatures above 200 ° C. However, such a technique imposes difficulties in obtaining the catalyst in a suitable physical form. In this way the granulation of the basic carbonate composition causes low resistance products with the reduction, while the granulation after the reduction requires the granulation to be carried out in an inert atmosphere. The catalysts of this reference contain only a minor amount, if any, of alumina, but a significant amount of zinc and / or magnesium. In the present invention it is preferred that the compositions have substantial copper contents but also containing, after reduction, at least 60% by weight of alumina, and that they are preferably essentially free of zinc and magnesium compounds, and that they have , with the reduction of copper species, a copper surface area elevated per gram of copper. The compositions are preferably in the form of shaped units suitable for use as fixed bed or sorbent catalysts. Accordingly, the present invention additionally provides a composition comprising a copper species and a porous transition alumina, preferably in the form of support units having a minimum dimension of at least 1 mm, the composition having an atomic copper ratio to aluminum in the range of 0.14 to 0.5 and having, in the reduction of the copper species with hydrogen at 250 ° C, a copper surface area of at least 60 m2, preferably at least 80 2, per gram of copper . The composition preferably has a BET surface area above 80 m2 / g. Preferably the atomic ratio of copper to aluminum is at least 0.16. The products of the invention can be used as catalysts or absorbers. With the copper species in the reduced form, they are used as catalysts for reactions involving hydrogen. For such use in some cases it may be desirable to impregnate the product with a noble metal such as platinum, palladium or rhodium. With copper species in the form of hydroxide or carbon dioxide, they are used in the purification of gases and liquids for the elimination of sulfur compounds. With the copper species in the form of a sulfide, they are used as absorbents for the removal of impurities such as mercury and alkaloids from gas and liquid streams. The invention is illustrated in the following examples. Example 1 An impregnation solution was prepared by dissolving 250 g of ammonium carbonate in 600 ml of aqueous ammonium hydroxide (concentation 35%, specific gravity 0.88) and then slowly adding 244 g of basic cupric carbonate, (55% in weight of Cu, CuC03 / Cu (OH) 2 weight ratio 1.2) with stirring at room temperature until dissolved. The solution was then filtered. 200 g of gamma alumina extrudates (SA support) 3 mm long and 1.2 mm in diameter having a BET surface area (A) of 294 m / g, a pore volume (Vp as derived from the branch of desorption of the isotherm of nitrogen fisisorción to 0.98 of relative pressure) of 0.65 ml / g and an average pore diameter (4 vp / A) of 88 Á, in 400 ml of the impregnation solution at room temperature. The impregnated extrudates were then filtered from the excess solution and dried overnight at 120 ° C. This dry material was designated as product 1-A-1. 150 g of the product 1-A-1 were then immersed for 10 minutes in 300 ml of the solution to be impregnated and then the excess solution was removed by filtration. The reimpregnated material was dried overnight at 120 ° C to give the product l-A-2. 100 g of product l-A-2 were then immersed for 10 minutes in 200 ml of the impregnation solution and then the excess solution was removed by filtration. The reimpregnated material was dried overnight at 120 ° C to give the product l-A-3. Part of the product l-A-3 was calcined in air at 300 ° C for 2 hours to give the product l-A-3c.

Example 2 The procedure of Example 1 was repeated but using extrudates (support SB) of 3 mm in length, 1.2 mm in diameter of teta-alumina having a BET surface area of 111 m2 / g, 0.45 ml / g volume of pore and an average pore diameter (4 V / A) of 163 Á as the support. The products were designated as 2-B-1, 2-B-2, 2-B-3 and 2-B-3c. Example 3 The procedure of Example 2 was repeated but using a slightly less concentrated copper complex solution, thus 700 ml of ammonium hydroxide of 30% concentration was used in place of the 600 ml of 35% amino hydroxide. % concentration The dried material was also calcined at 300 ° C after each impregnation. The product, after three impregnations with calcination after each impregnation, was designated 3-B-3c. Example 4 The procedure of Example 1 was repeated using gamma-alumina extrudates (SC support) 3 mm long and 1.2 mm in diameter having a BET surface area of 248 m2 / g, a pore volume of 0.77 ml / g and an average pore diameter (4 V / A) of 120 Á as the support. The dry material, after two stages of impregnation, was designated 4-C-2. The dried and calcined material after the third impregnation was designated 4-C-3c.

E j emp lo 5 Example 4 was repeated but the support was given 4 impregnations with drying at 120 ° C after each impregnation. The uncalcined final material was designated co-or 5-C-4. Samples of some of the products were analyzed by XRF and the copper surface area of some of the products was determined by nitrous oxide or nitrous oxide. . The reduction of the samples was carried out before the determination of the copper surface area by heating the sample at a rate of 200 K / h in a stream of hydrogen diluted with argon (67% H2 / 33% Ar by volume at a temperature of 393 K (120 ° C) maintaining this temperature for 30 minutes, and then increasing the temperature at a rate of 100 K / h to the desired reduction temperature, and maintaining at that desired temperature for 1 h after reduction, the sample It was cooled to 90 ° C at which temperature the nitrous oxide or nitrous oxide was used using a mixture of nitrous oxide and argon (1% N20 / 99% Ar by volume). It was assumed that the latter was an absorption of Cu5 / Oa s was 2 and that the area occupied by a copper atom is 5.18 Á, that is to say a packing density of 73%, 1.46 x 1019 copper atoms of surface per m The results are shown in the table if gui ente.

The copper content is the content of the copper species of the unreduced catalyst, expressed as elemental copper.

E n emp lo 6 The uncalcined sample 5-C-4 was tested for its ability to absorb mercaptans from a gas stream. 30 ml of the unreduced material was charged to a 25 mm diameter reactor tube to form an absorbent bed. Methane, containing 20 ppm by volume of propyl mercaptan, was passed down through the bed at an atmospheric pressure of 25 ° C at a rate of 14 liters per hour, ie a space velocity of 467 h_1, and the effluent- was analyzed by sulfur-containing compounds. During a period of 450 hours, no sulfur compounds were detected in the effluent (detection limit 0.5 ppm in volume), indicating a total sulfur elimination. To accelerate the test, the content of the feed gas was increased to 100 ppm by volume and the continuous test. After 235 additional hours of running time, 6 ppm by volume of dip r or i 1 di s or 1 f or r was detected in the gas outlet stream.

After an additional 221 hours of testing, the dipropyl disulfide content had increased to 35 ppm by volume. In this stage, the feed is replaced by nitrogen at the same flow rate. During the subsequent 1054 hours the dipr opi 1 sulphur was gradually desorbed from the absorbent bed until the sulfur level in the effluent decreased to less than 2 ppm by volume. At no time was a propymetry detected while feeding either the propylmercaptan containing methane or nitrogen in the gas outlet stream. The absorbent bed was then discharged and analyzed for the total sulfur level. The upper 10 ml of the absorbent bed had an average sulfur content of 4.41% by weight, the average 10 ml had an average sulfur content of 3.12% by weight and the lower 10 ml had an average sulfur content of 0.99% by weight. This shows that in addition to absorbing propylmercaptan, the material was also effective to catalyze the dimerization of propylmercaptan.

E j emple 7 (comparative A nickel analogue containing approximately 14.5% by weight of nickel, from the 2-B-3 material was made by a similar route.) After calcination and reduction at 420 ° C, it had an area of nickel surface in the range of 150-160 m2 per gram of nickel The uncalcined material was tested as in Example 6 except that the content of me rc apt i lme rc ap ta was not 100 ppm by volume. Total sulfur removal was achieved for only 231 hours, and from then on, propylmercaptan and dipropyl disulfide were detected in the effluent at levels of 37 ppm in volume and 21 ppm in volume respectively, after a total run time of 330 hours , the system was purged with nitrogen, it took 189 hours to purge to desorb the sulfur compounds from the absorbent to give a sulfur content of the effluent below 2 ppm by volume.The analysis of the 10 ml portions of the absorbent gave an average content of sulfur 0.92% (upper), 0.87% (medium), and 0.83% (lower), all by weight. It is seen by comparison with Example 6, that the nickel analog was much less effective than the copper-containing material.

E j empl o 8 (comparative) To assess the effectiveness of a transitional alumina alone, the procedure of Example 6 was repeated using gamma alumina spheres of diameter in the range of 3.3 to 4.7 mm and having a surface area of 300 m2 / g and using methane containing 20 ppm by volume of propylmercaptan. After only 17 hours the effluent contained 10 ppm by volume of propyl mercaptan. The system was then purged with nitrogen for 24 hours. Analysis of the 10 ml portions of the absorbent gave average sulfur contents of 0.04% (upper), 0.03% (medium), and 0.03% (lower), all by weight, showing that the alumina was not effective as an absorbent for the propylmercaptan.

Claims (11)

1. Process for the manufacture of a composition comprising a copper compound supported on a transition alumina comprising impregnating a porous-transition alumina support with an aqueous solution of a cupric amine complex, draining any excess of the impregnation solution, and then heating the impregnated support to a temperature above 80 ° C to decompose the complex by depositing a basic cupric carbonate compound on the surfaces of the pores of the support of the transition mine in a form highly dispersed in such a way that if the copper compound is reduced to metallic copper, the composition will have a copper surface area above 40 m2 per gram of copper.

2. Process according to the claim 1, wherein the transition alumina is gamma or teta-alumina.

3. Process according to claim 1 or claim 2, wherein the transition alumina support is preformed into shaped units having a minimum dimension of at least 1 mm.

4. Process according to claim 3, wherein the transitional alumina units have maximum and minimum dimensions in the range of 1 to 1 mm.

5. Process according to any one of claims 1 to 4, wherein, after heating the impregnated support to decompose the cupric ammonia complex, the support is given one or more additional impregnations with the solution of the amine complex. na - carbo n to cupric.

6. Process according to any of claims 1 to 5, wherein the impregnated support is heated to a temperature above 250 ° C to decompose the basic cupric carbonate into copper oxide.

7. Process of. according to any of the rei indications 1 to 6, wherein, after heating the impregnated support to decompose the cupric amine-carbonate complex, the copper compound is reduced to elemental copper to give a composition having a surface area copper above 40 m2 per gram of copper.

8. . Process according to any of claims 1 to 7, wherein the amount of the amine-ca-rbonone or cupric complex employed is such that the atomic ratio of copper to aluminum is in the range of 0.025 to 0.5.

9. Composition comprising a kind of copper supported on a porous transition alumina, the composition has an atomic ratio of copper to aluminum in the range of 0.14 to 0.5 and it has, with the reduction of copper species with hydrogen at 250 ° C , a copper surface area of at least 60 m2 per gram of copper.

10. Units configured according to claim 9, characterized in that they have a BET surface area above 80 m / g.

11. Units configured according to claim 9 or claim 10, having an atomic ratio of copper to aluminum of at least 0.16.