RU2316394C1 - Method of preparing mono- and bimetallic catalyst and processes involving oxygen and/or hydrogen - Google Patents

Abstract

FIELD: reduction-oxidation catalysts.

SUBSTANCE: invention relates to mono- and bimetallic palladium and platinum catalysts if carbon carriers that can be used in processes involving oxygen and/or hydrogen. A method for preparing catalyst is described comprising pretreatment of carbon carrier in 3-15 M nitric acid at temperature not exceeding 80°C, impregnation of resulting carrier by nitric acid solutions of chloride-free compounds of palladium and/or platinum or palladium and at least one group I metal, drying at temperature up to 105°C, decomposition at 150-350°C, and reduction in hydrogen flow at 110-350°C. Specified preparation conditions allow one to obtain fine particles of platinum group metals 1-10 nm in size localized in pores 2-20 nm in size, concentrations of deposited palladium and/or platinum being 3 to 50 wt % or palladium and/or platinum and silver 0.1 to 1.4 wt %. Catalyst is suitable for use in processes of oxidation of alcohols into aldehydes and carboxylic acids; hydrogenation of olefin, acetylene, and diene bonds in aliphatic and carbocyclic compounds; hydrogenation of nitro compounds into amines or intermediate compounds; disproportionation of abietic and other resin acids contained in colophony and similar natural- or artificial-origin mixtures.

EFFECT: augmented assortment of redox catalysts and optimized methods of preparation thereof.

8 cl, 1 tbl, 34 ex

Description

The invention relates to mono- and bimetallic palladium and platinum catalysts on carbon carriers and can be used in the chemical industry for carrying out processes involving oxygen and / or hydrogen.

In particular, the invention can be used in the chemical industry for the production of electrocatalysts, for example, for fuel cells, as well as for carrying out the oxidation of hydrocarbons, for example for the oxidation of aldehydes, primary and secondary alcohols. The invention can also be used in the chemical industry for hydrogenation, requiring the addition of hydrogen to one or more unsaturated groups or fragments in the molecule of an organic compound, for example, for the hydrogenation of aliphatic or carbocyclic olefin, polyene, acetylene or allen compounds, mono- or polycyclic aromatic compounds, imines, nitro and carbonyl compounds. The invention can also be used in the chemical industry for carrying out hydrogenation processes accompanied by the cleavage of one or more carbon bonds, carbon bonds with heteroatoms or bonds between heteroatoms, in particular for carrying out hydrodehalogenation, decarbonylation, decarboxylation, debenzylation, production of amines from nitro compounds or azo compounds. The invention can also be used in the chemical industry for carrying out processes of intra- and intermolecular redistribution of hydrogen, in particular for carrying out the processes of the disproportionation of resin acids in rosin and other natural mixtures.

The invention is particularly suitable for use in oxidation, selective hydrogenation and hydrogen transfer processes requiring high dispersion of platinum and palladium. The invention is even more suitable for use in oxidation processes and selective hydrogenation processes on highly dispersed catalysts with a high content of platinum and palladium in the catalyst or a high concentration of metal in the active layer of catalyst granules. The greatest advantage from the use of the invention can be obtained when carrying out high-temperature hydrogenation and hydrogen transfer processes, in which the use of other palladium catalysts is accompanied by intense sintering of palladium and gum formation, which reduce the life of the catalyst and degrade the quality of the product.

Known methods for the preparation of palladium and platinum catalysts on carbon carriers [A. Century. Catalyst Manufacture. Laboratory and Commercial preparations. N.Y .: Marcel Dekker, 1983; E. Auer, A. Freund, J. Pietsch, T. Tacke. Carbons as supports for industrial precious metal catalysts, Appl. Catal A: General 173 (1998) 259-271]. The starting compounds of palladium in the preparation of the catalyst are salts of this metal and inorganic or organic acids, organometallic compounds and complexes with organic ligands. The use of carboxylates, organometallic compounds and metal complexes of palladium and platinum has the disadvantage that in this case it is necessary to use non-aqueous solutions, which is economically disadvantageous; while metal-organic derivatives are sensitive to atmospheric oxygen, which leads to technological complications.

Typically, catalysts containing palladium or platinum on a carbon support are prepared from palladium or platinum chloride. The application of palladium chloride to carbon material from an acidic medium and the recovery immediately after such application or after drying gives low-activity catalysts and is an old practice. All other methods for preparing Pd / C catalysts from palladium chloride are based on the ability of these salts to hydrolyze in an alkaline medium due to the easy formation of metal oxide nuclei and differ only in the nature of the alkaline agent, the methods of its introduction (in advance, after or simultaneously with palladium), the ratio between alkali and palladium, the physical parameters of the hydrolysis process, as well as the characteristics of the carrier used [A.J. Berd. Active carbon as a carrier. - Ch. 5 in the book: Carriers and supported catalysts. Theory and Practice / Alvin B. Styles: Per. from English / Ed. A.A.Slinkina. - M .: Chemistry, 1991]. For example, a method for producing a catalyst for hydrogenating benzoic acid by impregnating a carbon support with an aqueous solution of palladium hydrochloric acid and sodium carbonate, reducing palladium with sodium formate, washing and drying, followed by impregnation with sodium carbonate solution and re-drying, for example, characterized in that porous pyrocarbon is used as a carrier consisting of hollow globules 50-500 nm in size with a BET specific surface area of 75-640 m ² / g and an average interplanar distance of 0.34-0.36 nm [SU 1270939, B01J 23/4 4, 07/20/97]; A method of producing a catalyst for hydrotreating terephthalic acid, characterized in that the carrier is pre-treated with gaseous hydrocarbons at 700-1200 ° C to an additional content of pyrolytic carbon of 3-50 wt.% [SU 1660282, B01J 37/03, 02/10/97]; A method of producing a catalyst for the hydrogenation of nitrobenzotrifluoride, characterized in that a carbon material with a surface of 120-660 m ² / g, a transition pore volume of 0.4-1.2 cm ³ / g, an abrasion resistance of 0.5- 0.1% / min, which is the soot hardened by pyrocarbon obtained by the pyrolysis of gaseous hydrocarbons [SU 1188964, B01J 37/02, 07.20.97]; a method of preparing a catalyst for the synthesis of 2,6-dimethylaniline, comprising pre-mixing an aqueous solution of palladium hydrochloric acid with a concentration of 0.025-0.5 mol / l with a solution of sodium carbonate with a concentration of 0.05-1.0 mol / l in a molar ratio of 1: (2- 3) applying the resulting mixture of solutions with pH = 6.8-8.5 on a carbon carrier in an amount of 10-100% of the pore volume, hydrogen reduction, washing and drying, characterized in that the mixture of solutions is dispersed in the presence of gaseous carbon dioxide and application is carried out by ropuskaniya resulting aerosol moving through the carrier layer, which is a matrix formed by the curved layers of carbon 10-1000 nm thick, a radius of curvature of 10-1000 nm, a true density of 1.8-2.1 g / cm ^3, the x-ray density of 2,11-2 , 24 g / cm ³ , the pore size distribution having a maximum in the region of 20-200 nm, and an additional maximum in the region of 1-20 nm; washing is carried out with distilled water in the presence of gaseous hydrogen and the process is carried out at a ratio of components providing a palladium content in the catalyst of 0.093-1.0 wt.% [SU 1713172, B01J 23/44, 09/27/95]. Known methods for the preparation of Pt / C catalysts can be divided into two groups: 1) liquid-phase or gas-phase reduction of supported H ₂ PtCl ₆ , 2) applying platinum from a colloidal solution obtained from platinum chloride in the presence of a reducing agent. The first method is applicable for carriers with a developed specific surface area, and the second - when using graphite or carbon black with a low specific surface area. For example, there is a method of preparing a catalyst for the oxidation of glucose phosphate to gluconic acid phosphate containing 5 wt.% Pt, comprising adsorption of 6.67% Pt (IV) platinum chloride on a Norit ROX granular carbon carrier for 3 days and reduction with formalin in alkaline medium (5M NaOH) at pH 12 [van Dam HE, Kieboom APG, van Bekkum H. Appl. Catal., 1987, v. 33 (2), 361-372]. A method for preparing a platinum catalyst on a carbon carrier for use as an electrode in fuel cells is claimed, which involves mixing an aqueous solution of platinum chloride with a concentration of 5 to 100 g / l and sodium dithionite with a concentration of 10 to 100 g / l in a ratio of 2: 1 up to 1: 5 at temperatures from 20 to 80 ° C, the addition of hydrogen peroxide before or after the addition of sodium dithionite, the adsorption of the obtained colloidal particles of platinum on carbon black [US 4136059, 01/23/1979]; claimed catalyst for the synthesis of hydroxylamine containing dispersed metal platinum on a carbon graphite-like carrier formed by flat carbon layers, characterized in that the catalyst contains a carrier with a true density of 1.8-2.1 g / cm ³ and a pore volume of 0.2-1 cm ³ / g, in which the carbon layers are packed in crystallites oriented in space in the form of faces of a polyhedron and have an interplanar distance d ₀₀₂ = 0.340-0.350 nm, the average crystallite size in the direction “a” L _a = 4-18 nm, the average size crystallite in the direction "c" L _c = 3.5-14 nm [RF 2065326, B01J 23/42, 1996.08.20]. A method of preparing this catalyst involves the deposition of platinum metal on graphite-like carbon. For this, a mixture of aqueous solutions of H ₂ PtCl ₆ (0.04 M), Na ₂ CO ₃ (1 M), NaOAc (1 M), Na ₂ S ₂ O ₄ (0.02 M) and CH _{2 is} added to the carrier suspension O (10% aqueous solution), the resulting mixture was kept under stirring for 3 hours at a temperature of 65 ° C. A catalyst was obtained with a platinum content of 0.5 wt.%.

The disadvantage of the preparation of catalysts using palladium or platinum chloride is the low dispersion of the metal in the resulting catalysts, the difficulty of varying the thickness of the active layer, the need for very precise adherence to the conditions of the hydrolysis process due to the sensitivity of this process to even small changes in conditions, and the need for a long washing of the catalyst from chloride ions and the disposal of large amounts of wastewater. In addition, it is known [US 3138560, 1967] that when sodium tetrachloropalladoate or palladium chloride is added to the carbon carriers, most of the palladium immediately precipitates as a shiny film of metallic palladium, and catalysts prepared in this way usually have low activity.

When describing methods for the preparation of Pd / C catalysts through alkaline hydrolysis, it is sometimes indicated that not only chloride but also other salts of palladium, in particular nitrate, can be used as the starting compound. It is known from the chemistry of palladium that the rapid hydrolysis of its chloride and the possibility of producing dispersed particles of oxide and then metal are due to the ease of formation of oxide phase nuclei in an alkaline medium due to the ability of chloride ions to coordinate to two palladium ions in the form of a bridging ligand, while palladium nitrate only slowly hydrolyzed under the same conditions. Therefore, obtaining in the same way and with the same characteristics of the catalyst from palladium nitrate is possible only with the introduction of additives of chlorides of other elements.

A catalyst is claimed [US 4791226, 12/13/1988] for the purification of terephthalic acid on active carbon with a specific surface area of ≥600 m ² / g, palladium content <0.3 wt.% And palladium crystallite size <3.5 nm; The method of preparation of this catalyst involves the deposition of a palladium salt, including nitrate, on a carbon carrier from an organic solvent and is based on the ability of the initial palladium compound to be reduced to metal under specified conditions upon contact with a carbon surface. The disadvantage of this catalyst and the method of its preparation is the low palladium content and the need to use organic solvents.

Recently, platinum nitrate is widely used as a chloride-free precursor of platinum in the preparation of catalysts for the purification of exhaust gases. Thus, a platinum rhodium catalyst for purifying automobile exhaust gases is known, a method for preparing this catalyst involves impregnation of a platinum and rhodium carrier with a cellular structure containing aluminum and cerium oxides with nitrates and calcining the sample at 500 ° C for 2 hours [D.Dou; D.J. Liu, W. B. Williamson, K. C. Kharas, H. J. Robota, Applied Catalysis B: Environmental 30 (2001), 11-24].

Closest to the claimed method is a method for producing a catalyst, comprising applying palladium on a granular carbon carrier, followed by drying, decomposition and recovery, characterized in that the application of palladium is carried out from an aqueous solution of palladium nitrate with a content of free nitric acid in a molar ratio to palladium (6: 1) - (1: 1), drying is carried out in a stream of air at 110-130 ° C, decomposition is carried out in a stream of inert gas at 200-300 ° C and reduction is carried out in hydrogen at 150-250 ° C, the initial components are taken in quantity the welds providing the palladium content in the finished catalyst is 1.5-2.5 wt.% [RF 2056939, B01 / J23 / 44, 03/27/96]. The disadvantage of this method is that it is designed for a catalyst with a palladium content, which is not optimal for most catalytic processes.

Oxidation processes using palladium and platinum catalysts are known, including the oxidation of aldehydes, primary and secondary alcohols, in addition, platinum and palladium catalysts on carbon black are used in electrocatalysis - in phosphoric acid fuel cells and in proton exchange membrane fuel cells, where hydrogen is oxidized at the anode or methane [RLAugustine. Heterogeneous Catalysis for the Synthetic Chemist.- NY: Marcel Dekker. 1996; E. Auer, A. Freund, J. Pietsch, T. Tacke, Appl. Catal. A: General 173 (1998) 259-271]. Hydrogenation processes are known using palladium and platinum catalysts on carbon supports, including hydrogenation with the addition of hydrogen in one or more bonds or hydrogenation with cleavage of one or more bonds in the molecule of olefin, diene, acetylene and other compounds with an unsaturated hydrocarbon fragment, aromatic mono- and polycyclic compounds, cyano-, nitro-, amino- and other nitrogen-containing compounds, chlorine-, bromine- and iodine-containing compounds, carbonyl, carboxyl and other compounds with unsaturated functional groups or having carbon bonds with heteroatoms [M. Freifelder. Practical Catalytic Hydrogenation. - NY: Wiley, 1971; PNRylander. Hydrogenation methods.- London: Academic Press, 1985; RLAugustine. Heterogeneous Catalysis for the Synthetic Chemist. - NY: Marcel Dekker, 1996]. Hydrogenation and disproportionation processes through intramolecular and intermolecular hydrogen transfer using palladium catalysts are also known [Heck RF Palladium Reagents in Organic Synthesis. London: Acad. Press, 1985], including the processes of disproportionation of mono- and polycyclic compounds containing olefin and diene fragments, for example, abietic and other resin acids contained in rosin [Fr. 1,425,589,1966; Yap. 61-4779, 1986 ;. Poland 57930, 1969]. A method for the disproportionation of rosin [RF 2055848, 03/10/96] is proposed by stepwise passing the rosin melt through a catalytic system including cocatalyst — cured dehydrated aluminum-containing additives in the amount of 3-10 wt.% Acid-activated bentonite type clay with a specific active surface of 50-70 m ² / g, calcined at 250-400 ° C, and the palladium catalyst is palladium carbon in a ratio of 3: 1; A method of obtaining a disproportionate rosin [RF 2059680, 05/10/96] by stepwise passing the rosin melt through a catalytic system comprising an aluminosilicate catalyst with a specific active surface of 50-70 m ² / g, cured with 1-5 wt.% aluminum-containing additive, calcined at 400- 450 ° C dehydrated clay of the bentonite type promoted with silicon dioxide with a specific active surface of 120-300 m ² / g in an amount of 1-5 wt.% Per clay, and palladium coal in a ratio of 3: 1; A method of disproportioning rosin and resin acids by heating them in the presence of a catalyst - palladium on a carbon support, characterized in that palladium on a carbon-carbon composite with an interplanar distance d _{002 of} 0.34-0.35 nm and microcrystallite size L _{a is} used as a catalyst 3.0-5.5 nm and L _c 3.0-6.8 nm [RF 2081143, C09F 1/04, 1997]; obtaining a lightly colored disproportionate rosin with a low content of unsaponifiables by dissolving rosin and carrying out the reaction in solution using a Pd / C catalyst at a temperature of <200 ° C [Tang Yaxian et al. Disproportionate rosin obtained during dissolution. - Linchan huaxue yu gongye (Chem. And Ind. Forest Prod.), 1996, 16, N4, pp. 1-7, RJChem. 1998, 6F2]. In industry, the process of disproportionation of rosin is carried out in a melt on a PU catalyst (palladium charcoal) with a palladium content of 1.8-2.0 wt.%.

A disadvantage of the known processes involving oxygen and hydrogen using palladium and platinum catalysts on carbon carriers is the low efficiency of the use of the expensive catalyst component and low selectivity due to the non-optimal content and state of palladium and platinum in the known Pd / C and Pt / C catalysts and is associated with the disadvantages of the known methods for producing such catalysts. A disadvantage of the known processes is also the complexity of the technology, the use of a solvent or harsh process conditions, which is associated with the need to reduce the disadvantages of the known Pd / C and Pt / C catalysts and methods for their preparation and makes the final product more expensive. A disadvantage of the known processes is the need to use a cocatalyst for the same purpose, which increases the number of stages in the preparation of the catalyst, complicates the production method, and increases the cost of the final product. A disadvantage of the known processes is also the difference in the catalysts used, due to the difference in the methods of compensating for the disadvantages of the known catalysts for different processes and leads to the production of catalysts in small batches and according to different technological schemes instead of a more economically efficient large-capacity production.

In a number of works, it is noted that the introduction of a second metal into the composition of the catalyst, for example, Group VIII metals, as well as Ag, Au, Cu, Sn, Bi, Pb, Ti, Zr, Hg, leads to an improvement in the catalytic efficiency of platinum or palladium. For example, in the oxidation reactions of alcohols, the introduction of tin or bismuth to a platinum or palladium catalyst significantly reduces the rate of deactivation of the catalyst. The introduction of the second metal also leads to an increase in catalytic activity and, in some cases, the selectivity of the oxidation reaction [R.L. Augustine. Heterogeneous Catalysis for the Synthetic Chemist. - NY: Marcel Dekker, 1996; pp.559-569].

In acetylene selective hydrogenation reactions, the addition of a second metal to the palladium catalyst, for example Ru, Ag, Au, Cu, Sn, Bi, Pb, Ti, Zr, Hg, leads to an increase in the selectivity of the process due to a decrease in catalytic activity and, consequently, better diffusion of reagents to active centers [RLAugustine. Heterogeneous Catalysis for the Synthetic Chemist. - NY: Marcel Dekker, 1996; pp. 387-401; E.A.Sales, R.C. Santos, S.B. de Olivera, L.B. de Olivera Santos. An. Assoc. Bras. Quim., 1997, N46 (2), pp. 65-73]. The inventive method of preparation allows to obtain bimetallic catalysts with high efficiency in processes involving oxygen and / or hydrogen and organic substrates.

Described [RF 2056939, B01J 23/44, 03/27/96] disproportionation of rosin on a catalyst containing 1.5-2.5 wt.% Palladium with particles of 2-8 nm in size and the active layer in the granule 10-50 microns thick and obtained thermal decomposition of palladium nitrate on a carbon carrier Sibunit, which is produced by applying pyrolytic carbon to technical soot and is a three-dimensional matrix formed by carbon layers 10-1000 nm thick, in which the graphite structure with azimuthal misorientation of graphite networks is preserved, so that the coher scattering has a size L _a , L _{c of} about 3.5 nm and the interplanar spacing is d ₀₀₂ 0.345-0.355 nm, with a radius of curvature of the layers 10-1000 nm, a true density of 1.80-2.1 g / cm ³ , x-ray density 2.112-2.236 g / cm ³ , pore volume 0.2-1.7 cm ³ / g, pore size distribution with a maximum in the region of 20-200 nm or two maxima in the region of 20-200 and 4-20 nm [US 4978649 12/18/1990; Yu.I. Yermakov et al. New carbon material for catalysts. - React. Kinet. Catal. Lett., 1987, v. 33, N2, pp. 435-440; EM Moroz et al. Structural and substructural parameters of carbon supports Sibunit and Altunit. - React. Kinet. Catal. Lett., 1992, v. 47, N2, pp. 311-317]. The use of such a catalyst allows the process to be carried out under less severe conditions, without solvent, cocatalyst or the introduction of promoters, and the resulting product corresponds to a grade A pine rosin of the highest quality category in terms of color intensity and acid number, with an abietic acid content that meets accepted standards (<5%) . A disadvantage of processes using such a catalyst is their limitation by intramolecular and intermolecular hydrogen redistribution in highly viscous substrates, and the use of a catalyst with a palladium content> 2 wt.% Does not provide an increase in productivity (i.e., the degree of use of the active component decreases), and the use of a catalyst with a palladium <1.5 wt.% Requires more time to achieve the same degree of conversion of abietic acids (reduced productivity).

The objective of the invention is to develop a high-tech method for producing a mono- or bimetallic palladium and / or platinum catalyst on a carbon carrier, highly effective for use in processes involving oxygen and / or hydrogen, including those carried out in highly viscous media and at high temperatures.

The problem is solved by obtaining a mono- or bimetallic palladium and / or platinum catalyst on a carbon support by impregnating a carbon support pretreated in an oxidizing medium with palladium and / or platinum or palladium compounds and at least one of Group I metals, the support being pretreated in nitric acid with a concentration of 3 to 15 M at a temperature not exceeding 80 ° C, an impregnating solution is prepared from nitric acid solutions of chloride-free compounds of palladium and / or platinum or pal adium and at least one of the metals of group I, their drying and decomposition are carried out in an inert gas stream at a temperature not exceeding 105 ° C and from 150 to 350 ° C, respectively, the reduction is carried out in a stream of hydrogen at 150-350 ° C, under other conditions of deposition, drying, decomposition, recovery, and the ratio of the starting components providing dispersed particles of platinum group metals with a size of 1-10 nm, localized in pores with a size of 2-20 nm, with a content of supported palladium and / or platinum from 3 to 50 wt.% Or palladium and / or platinum and sulfur ebra from 0.1 to 1.4%;

obtaining a mono- or bimetallic palladium and / or platinum catalyst on a carbon carrier, obtained by thermal decomposition of hydrocarbons on soot granules with subsequent oxidative activation or without it and representing a carbon material with a pore volume of 0.1-1.5 cm ³ / g, formed carbon layers with a thickness of 10-1000 nm with a radius of curvature of 10-1000 nm, a true helium density of 1.80-2.1 g / cm ³ , an X-ray density of 2.112-2.236 g / cm ³ and pore size distribution with maxima in region 3 -20 nm and 20-200 nm; or on a carbon support obtained by the decomposition of methane or ethylene at temperatures from 600 to 700 ° C on a catalyst containing metallic nickel and iron or copper supported on alumina with a specific adsorption surface of nitrogen from 105 to 260 m ² / g, mesopore surface from 95 to 240 m ² / g, micropore volume from 0.01 to 0.02 cm ³ / g, total pore volume from 0.31 to 0.4 cm ³ / g and an average pore diameter of from 6.2 to 17, 5 nm.

the use of such a catalyst in processes involving oxygen, for which it is known that they are accelerated in the presence of palladium and platinum catalysts, in particular, in the selective oxidation of aldehydes to carboxylic acids, primary alcohols to aldehydes or carboxyl alcohols, secondary alcohols to ketones;

the use of such a catalyst in processes involving hydrogen, for which it is known that they are accelerated in the presence of palladium and platinum catalysts, in particular, in the hydrogenation of organic compounds containing unsaturated С = С, С≡С, C = N, C≡N, N = O, C = O groups or aromatic, diene and other unsaturated fragments, for example, in the hydrogenation of olefinic bonds in aliphatic or carbocyclic compounds, the hydrogenation of acetylene and diene bonds in unsaturated aliphatic or carbocyclic hydrocarbons, in the village tive hydrogenation of acetylenic and diene compounds to monoenoic compounds in the mixtures of diene and acetylenic compounds with olefinic compounds, in particular in the selective hydrogenation of acetylene in the mixture thereof with ethylene or hydrogenating abietic and other resin acids contained in rosin and similar mixtures of natural or synthetic origin;

the use of such a catalyst in hydrogenation processes proceeding with the cleavage of one or more of the bonds C — C, C — O, CN, C-halogen, CS, or N — O present in the molecule of the starting compound, for example, in the hydrogenation of nitro compounds to amines or intermediates ;

the use of such a catalyst in processes of intra- and intermolecular hydrogen transfer, in particular in the disproportionation of abietic and other resin acids contained in rosin and similar mixtures of natural or artificial origin.

The advantages of the proposed method for the preparation of the catalyst over the known methods for producing mono- and bimetallic palladium and platinum catalysts on carbon carriers are achieved in that it provides the required characteristics of the catalyst. Moreover, the inventive method allows the use of aqueous solutions, but eliminates the contamination of the catalyst with chloride ions, without requiring rinsing, makes it possible to run the catalyst with different metal contents, active layer thickness and other characteristics within the limits specified for them according to the same technological scheme and with a relatively simple hardware design of the operating process, which, together, minimizes energy costs, the consumption of reagents used, the number and duration of nyh preparation steps and the volume of waste to be disposed of, thereby reducing the catalyst cost and ensuring the environmental cleanliness.

The advantages of the processes of oxidation, hydrogenation and hydrogen transfer with the participation of the inventive catalyst are provided by increased productivity, selectivity and catalyst life. The advantages of increased catalyst productivity are achieved in that the process can be carried out under less severe conditions, and / or with less loading of the catalyst, and / or by increasing the feed rate; the benefits of increased catalyst selectivity are achieved in that the yield of the target product is increased and its quality and the product can be used without further purification; The advantages of more stable operation of the catalyst are achieved in that the costs of the catalyst and its reloading are reduced, and the continuous process can be replaced with a batch process, conducting the process as needed for this product. Moreover, the use of a catalyst does not require changes in the hardware design of these processes and changes in other conditions for their implementation, but allows such changes to obtain additional benefits from the use of the inventive catalyst in comparison with processes using known catalysts. The use of a catalyst also makes it possible to refuse the introduction of promoters, but allows such an introduction into the catalyst or raw materials to obtain additional advantages.

The metal content, the size of its particles and the characteristics of the carrier are selected so as to provide the catalyst with the possibility of use in any processes involving oxygen and hydrogen. The optimal values of these parameters are determined for each specific process and its conditions. Catalysts with a metal content of up to 50 wt.% Can be used in the preparation of fuel cells. Catalysts with a metal content of up to 10 wt.% May be required for the oxidation and hydrogenation of substrates with particularly low reactivity and, if necessary, to obtain a large amount of product using small reactors. For use in most other processes, a catalyst with a metal content of ≤4 and even ≤1.5 wt.% Will have advantages, since with a decrease in the metal content it is easier to provide the required dispersion of the metal and the role of the diffusion factor is reduced, which increases the degree of utilization of the supported component. Catalysts with a metal content of about 0.2 wt.% May be required for processes that occur at high speed and for which there is a problem of a sharp decrease in selectivity when reaching a substrate conversion close to 100%. With a low metal content, the catalyst is more sensitive to poisoning by impurities in the carrier or feed, and in most cases it is advantageous to use catalysts with a metal content of ≥0.5 and even ≥1 wt.%.

The reduction in the particle size of palladium and platinum in the catalyst aims to increase the proportion of productively working metal atoms, which are atoms located on the surface of metal crystallites (atoms located in the bulk of crystallites are not accessible to organic compounds and the proportion of such atoms increases in proportion to the size of the particles). The upper limit in size (10 nm) is determined by the capabilities of the method of producing the catalyst at the stated metal content. The lower size limit (1 nm) is determined by the fact that smaller particles of palladium and platinum are not sufficiently strong bond with the surface of the carrier.

A strong bond with the carbon surface is necessary to impart sintering resistance to the particles during the catalytic process and is provided by the oxidative treatment of the support and the method of preparing the catalyst through thermal decomposition and reduction of palladium and / or platinum nitrate. Additional stabilization is provided by the carrier used - due to the localization of particles in its pores. The size of the pores that the carrier must contain is determined so that the metal particles remain accessible for the molecules of the organic compound and, at the same time, a significant stabilizing effect of the pores is achieved in comparison with the localization of metal particles on a smooth surface. It is optimal that the pore size is 2-4 times larger than the size of the metal particles, with the higher of these values (4) for small particles and the smallest (2) for large particles.

A certain change in the mass of the carrier during the preparation of the catalyst is caused by the oxidation of its surface under the action of nitric acid, as well as by reactions in the surface layer during interaction with palladium and / or platinum particles during the thermal decomposition of metal nitrate and subsequent reduction. The occurrence of such reactions to a limited extent provides palladium and platinum with a stronger bond with the carrier and gives the metal particles the required stability to sintering. The use of a carrier for which the change in mass exceeds the specified limits indicates the instability of the carrier to thermal, oxidative and reduction treatments and leads to a deterioration of the properties of the catalyst.

The carrier obtained by thermal decomposition of hydrocarbons on soot granules with subsequent oxidative activation or without it, as well as the carrier obtained by catalytic decomposition of methane or ethylene, satisfies these conditions in terms of porous structure and stability and, in addition, is characterized by a low content of impurities (ash less than 1- 2 wt.%) And high resistance to mechanical stress (abrasion resistance of 0.1-0.5% / min), which allows to further improve the properties of the catalyst.

Before use, the carbon carrier can be subjected to additional processing in order to improve its quality, for example, oxidative treatment with gaseous or liquid reagents to develop a functional surface coating, reduction treatment to remove surface functional groups, heat treatment to increase crystallinity, washing to remove impurities, hydrothermal treatment in the presence of suitable reagents to remove dusty carbon particles and fragile fragments carbon ntov with the outer surface of the granules, and other treatments. It has been found that the best catalysts are obtained if the support is pretreated with nitric acid.

The preparation of the catalyst includes the deposition of nitrates of palladium and / or platinum, palladium and silver on a carbon carrier, followed by drying, decomposition and reduction, since a positive effect is achieved by the combination of these methods.

The use of palladium and / or platinum nitrates as a starting compound is due to its advantages over other salts of palladium and platinum. Palladium and platinum nitrates have practically unlimited solubility in nitric acid solutions, which makes it possible to obtain a catalyst even with a limiting content of palladium and / or platinum by means of a single impregnation of the carrier with a solution. The possibility of a wide variation in the concentration of palladium and platinum nitrates in the solution also makes it easy to vary the metal content in the catalyst and the thickness of the active layer in the granules by varying the concentration and volume of the impregnating solution. Another advantage of palladium and platinum nitrates over other salts of palladium and platinum is that when water is removed from the carrier impregnated with a solution of palladium and / or platinum nitrate, the pores of the carrier are volumetricly filled with palladium and / or platinum salt and the particle size is solid salt is equal to the size of the pores in which the particles are localized. When decomposed to oxide, a natural decrease in particle volume occurs; a further decrease in the particle size of the deposited phase occurs when the oxide is reduced to metal. The desired ratio between the particle sizes of palladium and / or platinum and the pore size is determined by the ratio between the molar volumes of solid palladium and / or platinum nitrate and metallic palladium and / or platinum. Finally, during deposition, drying, and especially during thermal decomposition of palladium and / or platinum nitrates, due to the redox interaction between the carbon carrier and the deposited component, a bond forms between the metal atoms and the carbon surface, which ensures the resistance of metal particles to sintering at high temperature .

The application of palladium and / or platinum, palladium and silver is carried out from aqueous solutions, since in this case it is possible to create a sufficiently high concentration of palladium and / or platinum, palladium and silver in the solution, and the application process is the cheapest and easiest to process. The application is carried out by known methods, for example, by irrigation of a carrier placed in a rotating container until 5-100% of the internal pore volume of the carrier is filled with a solution. Typically, the impregnating solution contains free nitric acid, which is associated with the use of an excess of nitric acid in the preparation of the impregnating solution by treatment with nitric acid of metallic palladium and platinum hydroxide. The final concentration of nitric acid in the impregnating solution is selected depending on the required characteristics for the obtained catalyst, but such as to prevent the formation of hydrolysis products in the solution and uncontrolled (spontaneous) reduction of metal nitrates upon contact of the solution with the carbon surface with the formation of low-disperse crystallites. Bimetallic catalysts are prepared by joint or sequential application of metal precursors.

Preliminary drying of the sample with the applied compound of palladium and / or platinum, palladium and silver is carried out in order to fix small particles of a metal salt on the surface of the carrier and thereby provide easy control for subsequent thermal decomposition of this salt. In the presence of water, salt particles remain mobile, and during thermolysis, predominant growth of large particles of the formed metal oxide occurs, which causes a low dispersion of the catalyst. To accelerate the drying process, it should be carried out at an elevated temperature, at a temperature at the end of the process above the boiling point of water.

The decomposition of metal nitrate before reduction is necessary in order to exclude the formation of volatile hydride complexes of palladium and / or platinum ammonia. They are formed in the presence of hydrogen due to the reduction of the released nitrogen oxides and are autocatalytically decomposed on previously formed metal particles; as a result of the intensive growth of crystallites, there is a loss of metal dispersion and a decrease in catalyst productivity. To reduce the duration of the decomposition process, the catalyst is heated above 150 ° C; the upper temperature limit is due to the need to preserve the metal oxide in a sufficiently dispersed state.

The upper limit on the temperature of reduction of the catalyst is determined by the need to limit the sintering of the metal during recovery, the lower - the need to ensure the completeness of recovery. As a rule, the final reduction temperature should be not less than the temperature at which the catalyst will be used in the catalytic process.

Additional methods that contribute to giving the catalyst the required characteristics in terms of particle size of palladium and platinum, the degree of their interaction with the carbon surface, and distribution over the granule are well known to specialists working in the field of preparation of supported catalysts and, among other things, include varying the volume of the impregnating solution with respect to the volume pores of the carrier, varying the concentration of the initial salt in the solution and its acidity, the temperature of the solution and the impregnated carrier, the duration of the stage impregnation, the rate of temperature rise during drying, thermolysis and recovery, the flow rate displacing an inert gas during drying and thermolysis, as well as the variation of the recovery mode — by performing the recovery uniformly throughout the catalyst volume or layer by layer, when the recovery front moves from above or from the bottom of the column or alternately when using pure hydrogen or in a mixture with an inert gas, when recovering under static conditions or in a stream of hydrogen with different feed rates, and also when restoring component with varying degrees of thermal decomposition. Moreover, the specific values of the parameters declared as distinctive for each of the stages of the preparation of the catalyst, and other conditions for this stage depend on the conditions for the remaining stages.

The invention is illustrated by the following examples.

The following examples 1-34 characterize the catalyst, the method for its preparation and processes using it. The data from examples 1-14 are summarized in the table and show that the distinctive features of the proposed method provide the catalyst with the required characteristics for the content of palladium and / or platinum, palladium and silver, the size of the metal particles. Example 15 shows that when using a platinum chloride precursor, less dispersed catalysts are obtained, in addition, the use of a second metal chloride precursor in the preparation of bimetallic catalysts (example 16), as well as the preparation of carbon supported catalyst, in which the catalyst is exposed to solutions containing chloride ions (example 17), gives a catalyst with a substantially different state of palladium. Examples 18 and 19 show that the nitrate process for producing the catalyst provides the required stability of the palladium particles and the carrier. Example 20 is given for comparison and shows the specificity of the proposed method in that the decomposition of palladium nitrate on an oxide support gives a catalyst with a substantially different state of palladium. Example 21 describes an oxidation process using the inventive catalyst, and Examples 22-26 characterize the most typical hydrogenation and hydrogen transfer processes. In this case, examples 22-24 relate to rapidly occurring reactions in the gas phase, example 25 to a quick reaction in a three-phase system. Examples 26, 29, 30 respectively describe hydrogenolysis and disproportionation processes that require high temperature and for which the problem of productivity, selectivity, catalyst life and product quality is especially acute, and the benefits of using the inventive catalyst are most pronounced. Final Examples 27-34 characterize in more detail one of these high temperature processes. In this case, examples 27, 28 are given for the prototype, and examples 31 and 33 for comparison with a process that uses a catalyst obtained from palladium chloride and an industrial PU catalyst.

In examples 1-10, 16-18, the inventive catalyst was prepared on a Sibunit carbon carrier with a granule size of 1.5-3.2 mm, a specific surface for nitrogen adsorption of 410 m ² / g, bulk density of 0.57 kg / dm ³ , total the pore volume in terms of moisture capacity is 0.65 cm ³ / g, the predominant pore size is 3-15 nm, the ash content is 0.3 wt.%, the abrasion resistance is <0.1% / min. In examples 11, 12, the catalyst was prepared on carbon nanofibers obtained by the decomposition of methane at 625 ° C on a catalyst containing, wt.%: 65 Ni, 25 Cu and 10 Al ₂ O ₃ , with a specific surface area for nitrogen adsorption of 105 m ² / g , with a total pore volume in moisture capacity of 0.31 cm ³ / g and an average pore diameter of 11.9 nm, in examples 13-15, the catalyst was prepared on carbon nanofibers obtained by decomposition of methane at 625 ° C on a catalyst containing, wt.%: 65 Ni, 25 Cu and 10 Al ₂ O _3, a specific surface area by nitrogen adsorption of 260 m ² / g, a total pore volume of wetness 0.4 cm ³ / g and media they pore diameter of 6.2 nm.

The dispersion of palladium and / or platinum was determined by the chemisorption of CO by the pulsed method and the stoichiometry of CO / Pt, Pd adsorption equal to 1/1. The particle size of the metal D was calculated from the dispersion d by the formula: D (nm) = 108 / d (%); electron microscopy was used for verification. The pore size distribution data was obtained from nitrogen adsorption isotherms at 77 K.

Example 1. By dissolving metallic palladium in concentrated nitric acid with heating and subsequent dilution with distilled water to the required volume, a palladium nitrate solution is prepared with a palladium concentration of 160 g / l and a free nitric acid concentration of 210 g / l. 40 ml of the prepared solution is applied by conventional irrigation per 100 g of a granular carbon carrier, placed in a cylindrical container, rotated at a speed sufficient for high-quality mixing of the carrier. A sample coated with palladium nitrate is placed in a tubular reactor, a weak nitrogen flow is obtained (30 h ⁻¹ ), and an increase in temperature for 2 h to 105 ° C ensures the removal of water and nitric acid. After drying, the temperature is raised in 2 hours to 220 ° C and left at this temperature for another 1 hour. After the thermal decomposition of the applied palladium nitrate, the sample is cooled to 125 ° C and a mixture of nitrogen and hydrogen is supplied in a ratio of 4/1 with a volume velocity of 25 h ^-1 ; after 1 h, the inert gas supply is gradually stopped and the recovery in a stream of pure hydrogen continues with increasing temperature to 150 ° C. Upon completion of the reduction, the catalyst is cooled to room temperature, during the cooling process, hydrogen is displaced by nitrogen. Get a catalyst with a palladium content of 6.0 wt.%. About 1 g of the obtained catalyst is crushed in a mortar and examined for the dispersion of palladium by the chemisorption method, taking samples of 50 mg each; the results show that the dispersion of palladium is in the range of 44-48%, which corresponds to an average particle size of palladium 2.5-2.2 nm. One of the samples of the fragmented catalyst is examined using transmission electron microscopy; the results show that palladium particles have a uniform size distribution in the region of 1-5 nm, with a maximum at 2.8 nm.

Example 2. 2.5 ml of a solution of palladium nitrate with a palladium concentration of 80 g / l and a concentration of free nitric acid of 150 g / l is applied in a stream of air through a special nozzle that provides the solution in the form of an aerosol per 100 g of granular carbon carrier placed in closed rotating cylindrical container. After applying palladium, the sample is unloaded on a baking sheet, the baking sheet is placed over the heater and the sample is dried in a stream of argon at 40-60 ° C. Dried to constant mass, the sample is placed in a tubular reactor and thermal decomposition of palladium nitrate is carried out in a weak stream of argon (5 h ^-1 ), raising the temperature in 3 h to 215 ° C. The sample is cooled to 130 ° C and undiluted hydrogen is supplied from the top of the reactor with a space velocity of 5 h ⁻¹ until the rapid absorption of the reducing gas ceases, controlling the recovery process by the gas flow rate at the outlet of the reactor. At the end of the reduction, the temperature is raised to 170 ° C, held at this temperature for 1 h, the catalyst is cooled and hydrogen is displaced by argon. Get a catalyst with a palladium content of 0.2 wt.% And a dispersion of palladium 25-30% (particle size of palladium 4.3-3.6 nm).

Example 3. Adding with stirring an alkaline solution of sodium formate to a heated solution of palladium hydrochloric acid, a suspension of metallic black is obtained. Freshly precipitated palladium black is washed with distilled water until there is no reaction to chloride ions and dissolved in concentrated nitric acid, followed by dilution with water to obtain a palladium nitrate solution with a palladium concentration of 222 g / l and a free nitric acid concentration of 75 g / l. 50 ml of this solution is applied in small portions per 100 g of a stirred carrier, after which the sample with palladium nitrate applied is dried in a stream of nitrogen with a gradual increase in temperature to 105 ° C and then subjected to thermal decomposition in a stream of nitrogen (10 h ^-1 ), increasing the temperature for 2 hours to 200 ° C and absorbing the released nitrogen oxides by passing the gas mixture through an alkaline solution. Upon completion of the thermal decomposition of the applied palladium nitrate, the sample is cooled to 140 ° C, the inert gas supply is increased to 10 h ^-1 and hydrogen is added to the inert gas current with a gradual increase in the feed rate of the reducing gas to 10 h ^-1 . At the end of the recovery, the catalyst is treated sequentially in a stream of pure hydrogen at 160 ° C and in a stream of pure nitrogen, after which the catalyst is cooled. Get a catalyst with a palladium content of 9.9 wt.% And a dispersion of palladium 33-36% (particle size of palladium 3.3-3.0 nm).

Example 4. 31 ml of a solution of palladium nitrate with a concentration of palladium 135 g / l and a concentration of free nitric acid of 96 g / l is applied by conventional irrigation per 100 g of a rotationally stirred cylindrical container, the sample coated with palladium nitrate is placed in a tubular reactor and the sample is dried and thermal decomposition in a stream of nitrogen (10 h ^-1 ) with increasing temperature for 1 h ^-1 to 90 ° C and then for 1 h to 105 ° C and for 2 h to 190 ° C. After that, the catalyst is cooled to 125 ° C and a mixture of nitrogen and hydrogen in the ratio 1/1 at a volumetric feed rate of 25 h ^-1 . The recovery process is controlled by the change in the speed of the gas mixture at the outlet of the reactor and the temperature in the catalyst layers. Upon completion of rapid hydrogen uptake, the temperature is raised to 200 ° C. over 1 hour and the catalyst is cooled in a stream of nitrogen. Get a catalyst with a palladium content of 4 wt.% And a dispersion of palladium according to the results of chemisorption measurements of 41-48% (palladium particle size of 2.6-2.2 nm). 1 g of the resulting catalyst is additionally examined by x-ray; the results show that the X-ray diffraction pattern contains only reflections from the carrier, and the deposited palladium is X-ray amorphous (metal particle size <3 nm).

Examples 5-7. The catalyst is prepared in the same way as described in examples 1-4, by varying the volume of the impregnating solution (V _pp ), the concentration of palladium [Pd] and nitric acid [AK] in it, drying conditions, thermal decomposition and reduction. Distinctive features of the production conditions and the resulting catalysts are given in the table.

Example 8. 2.4 ml of a solution of palladium nitrate with a palladium concentration of 25 g / l and a concentration of free nitric acid of 67 g / l is applied by conventional irrigation to 24 g of a carrier stirred by rotation of a cylindrical container, a sample coated with palladium nitrate is placed in a tubular reactor and the sample is subjected drying and thermal decomposition in a helium stream (9 h ^-1 ) with increasing temperature for 0.5 h to 90 ° C and then for 1 h to 200 ° C. After that, the catalyst is cooled to 110 ° C and restored at a volumetric feed rate of 20 h ^-1 at 110 ° C for 1 h and at 150 ° C for 0.5 h. The recovery process is controlled by the change in the speed of the gas mixture at the outlet of the reactor and temperature in the catalyst beds. Get a catalyst with a palladium content of 0.24 wt.% And a dispersion of palladium according to the results of chemisorption measurements of 41-43% (particle size of palladium 2.6-2.5 nm).

Example 9. 2.4 ml of a solution of palladium nitrate with a concentration of palladium 25 g / l with a concentration of free nitric acid of 52 g / l and 2.4 ml of a solution of silver nitrate with a concentration of silver 25 g / l with a concentration of free nitric acid of 107 g / l is applied by conventional irrigation to 24 g of a carrier stirred by rotation of a cylindrical container, the sample with palladium nitrate deposited is placed in a tubular reactor and the sample is dried and thermally decomposed in a helium stream (17 h ^-1 ) at a temperature increase of 0.5 h to 90 ° C and then for 1 h to 200 ° C. After that, the catalyst is cooled to 110 ° C and restored at a volumetric feed rate of 19 h ^-1 at 110 ° C for 1 h and at 150 ° C for 0.5 h. The recovery process is controlled by the change in the speed of the gas mixture at the outlet of the reactor and temperature in the catalyst beds. Get a catalyst with a palladium content of 0.24 wt.% And 0.25 wt.% Silver with a dispersion of palladium according to the results of chemisorption measurements of 25-30% (particle size of palladium 4.3-3.6 nm).

Example 10. 9.4 ml of a prepared solution of palladium nitrate with a palladium concentration of 109 g / l and a concentration of free nitric acid of 157 g / l is applied by conventional irrigation to 24.6 g of a granular carbon carrier, placed in a cylindrical container, rotated with sufficient for good mixing carrier speed. A sample coated with palladium nitrate is placed in a tubular reactor, a helium current is obtained (16 h ⁻¹ ), and an increase in temperature for 0.5 h to 90 ° C ensures the removal of water and nitric acid. Upon completion of drying, the temperature is increased in 0.7 h to 200 ° C and left at this temperature for another 2 h. After the thermal decomposition of the applied palladium nitrate, the sample is cooled to 110 ° C and a mixture of hydrogen and helium is supplied in a ratio of 2/1 with volume a speed of 45 h ⁻¹ and the catalyst was reduced within 1 h. A catalyst was obtained with a palladium content of 4.0 wt% and a palladium dispersion of 38% (platinum particle size 3.0-2.7 nm).

Example. 11. By dissolving H ₂ [Pt (OH) ₆ ] in concentrated nitric acid with heating, a platinum nitrate solution is prepared with a platinum concentration of 228 g / L and a free nitric acid concentration of 1100 g / L. 5.1 ml of the prepared solution is applied by conventional irrigation per 10 g of a carbon carrier placed in a rotatable cylindrical container. The sample is subjected to processing in a helium stream (900 h ^-1 ) with stepwise heating: it is held at 90 ° C for 30 minutes, then heated to 200 ° C and maintained at this temperature for 1 hour. The sample is restored in a stream of hydrogen (3000 h ^-1 ) at 250 ° C for 1 h. A catalyst is obtained with a platinum content of 10 wt.% and a dispersion of platinum of 18% (particle size of platinum 6.3-5.9 nm).

Example 12 (for comparison with an oxidized carrier). By heating H ₂ [Pt (OH) ₆ ] in concentrated nitric acid, a solution of platinum nitrate is prepared with a platinum concentration of 228 g / L and a free nitric acid concentration of 1100 g / L. 5.1 ml of the prepared solution is applied by conventional irrigation per 10 g of carbon carrier, pre-treated in 15 N. HNO ₃ (1 g of support / 10 ml of HNO ₃ ) at room temperature for 2 hours and at 80 ° C for 2 hours and dried in air for 2 days. The sample is subjected to processing in a helium stream (300 h ^-1 ) with stepwise heating: it is held at 90 ° C for 30 minutes, then heated to 200 ° C and maintained at this temperature for 1 hour. The sample is restored in a stream of hydrogen (3000 h ^-1 ) at 250 ° C for 1 h. A catalyst is obtained with a platinum content of 10 wt.% and a dispersion of platinum of 33% (particle size of platinum 3.5-3.1 nm).

Example 13. By dissolving H ₂ [Pt (OH) ₆ ] in concentrated nitric acid, a solution of platinum with a concentration of platinum of 202 g / L and a concentration of free nitric acid of 1120 g / L is prepared by heating. 5.5 ml of the prepared solution is applied by conventional irrigation per 10 g of a carbon carrier placed in a rotatable cylindrical container. Before applying the active component, the carrier was washed from metal particles by boiling in a 2 M HCl solution, then in a large amount of hot water to pH ~ 5. The sample is processed in a helium stream (900 h ^-1 ) with stepwise heating: it is held at 90 ° C for 30 minutes, then heated to 250 ° C and maintained at this temperature for 1 hour. The sample is restored in a stream of hydrogen (3000 h ^-1 ) with stepwise heating: at 150 ° C for 1 h and at 250 ° C for 1 h. A catalyst is obtained with a platinum content of 10 wt.% and a dispersion of platinum of 46% (particle size of platinum 2.4-2.0 nm) .

Example 14. By dissolving H ₂ [Pt (OH) ₆ ] in concentrated nitric acid, a solution of platinum with a platinum concentration of 526 g / l and a free nitric acid concentration of 540 g / l is prepared by heating. 2.7 ml of the prepared solution is applied by irrigation to 5 g of the catalyst prepared according to example 13 and placed in a rotating cylindrical container. The sample is processed in a helium stream (900 h ^-1 ) with stepwise heating: it is held at 90 ° C for 30 minutes, then heated to 250 ° C and maintained at this temperature for 1 hour. The sample is restored in a stream of hydrogen (3000 h ^-1 ) at 150 ° C for 1 h and at 250 ° C for 1 h. A catalyst is obtained with a platinum content of 30 wt.% and a dispersion of platinum of 27%. The catalyst is examined using transmission electron microscopy; the results show that platinum particles have a uniform size distribution in the region of 2-5 nm, with a maximum at 3.7 nm.

Example 15 (for comparison with a chloride precursor). 200 ml of water are added to 10 g of the carbon support. To the resulting suspension of the carrier, 102 ml of a solution of H ₂ PtCl ₆ with a platinum concentration of 42 g / L are added with stirring. After 1 h, add 132 ml of NaOH solution with a concentration of 40 g / l and heat to 70 ° C. The suspension was kept at this temperature for 2 hours and 29.8 ml of a 10% sodium formate solution was added and held for another 1 hour. The catalyst was washed thoroughly with hot distilled water until a negative reaction for chloride ions was filtered off and dried at room temperature. A catalyst is obtained with a platinum content of 30 wt.% And a dispersion of platinum of 15% (average particle size of platinum 6.5-6.9 nm).

Example 16. 3.4 ml of a prepared solution of hexachloroplatinic acid with a concentration of platinum of 148 g / l is applied by conventional irrigation to 24.4 g of the catalyst prepared in example 10 and placed in a rotary container. The sample is placed in a tubular reactor, purged in a stream of helium (11 h ^-1 ) at 90 ° C for 0.7 hours

The catalyst is reduced in a stream of hydrogen (20 h ^-1 ) at 200 ° C for 1 h. A catalyst is obtained with a palladium content of 4.0 wt.% And platinum of 2.0 wt.% And a metal dispersion of 28% (particle size of platinum 3, 9-3.7 nm). According to electron microscopy, the number of large bulk particles increases compared to the monometallic catalyst prepared in Example 10. The results show that the use of platinum chloride precursor in the preparation of the bimetallic catalyst causes agglomeration of palladium particles even in a pre-reduced catalyst.

Example 17 (on the effect of chloride ions). The catalyst obtained from palladium nitrate in Example 4 and containing X-ray amorphous palladium (particle size <3 nm) with a dispersion d _{Pd of} 41-48% is impregnated with an aqueous NaCl solution with a molar ratio of NaCl / Pd = 4, which corresponds to the ratio between palladium and chloride -ions, if the catalyst was prepared by hydrolysis of palladium hydrochloric acid. After impregnation, the sample is heated to 90 ° C, washed for 2 days with water from chloride ions and restored again at 200 ° C. After such treatments, the dispersion of palladium in the d _Pd catalyst drops to 25-29%, and a reflection from large palladium particles with a size of more than 10 nm appears on the X-ray diffraction pattern (calculated by the half-width of the corresponding peak). The results show that treatment with solutions containing chloride ions causes agglomeration of palladium particles even in a previously reduced catalyst and with an initially strong bond of palladium particles to the surface of the carrier.

Example 18 (resistance to sintering). The catalyst obtained in example 6 and having an average dispersion of palladium 75% is subjected to additional processing in hydrogen at 200 ° C and then at 250 ° C. Processing at 200 ° C is accompanied by a slight decrease in the dispersion of palladium to 68%, and processing at 250 ° C to 59% (the average particle size of palladium varies from 1.45 nm to 1.6 and 1.8 nm).

Example 19 (on the stability of the media). 25.0 g of the carbon carrier Sibunit used in examples 1-7 are subjected to treatments under the conditions of example 6, in which a solution with the highest concentration of nitric acid but without palladium nitrate is used. Upon completion of all treatments, the mass of the carrier is 25.3 g (weight increase of 1.2% compared to the original).

Example 20 (for comparison with an oxide carrier). The catalyst is prepared as in Example 7 from the table, but silica gel with a specific surface area of 230 m ² / g and a pore volume of 1.0 cm ³ / g is used as a carrier. A catalyst is obtained with a palladium content of 1.4 wt.% And a dispersion of 8% (average particle size> 13 nm).

Example 21. 0.12 g of the catalyst obtained in the conditions of example 13 and 100 ml of an aqueous glucose solution containing 16 g of glucose are placed in a 250 ml reactor equipped with a thermometer, pH electrode, oxygen supply device and bubbler. The oxidation is carried out at atmospheric pressure, 50 ° C and the pH of the solution 10. The resulting acid is neutralized with a 10% NaOH solution. Samples were taken during the reaction, the solution was filtered, and then analyzed by ion chromatography. The conversion after 120 min of the reaction is 62%, the selectivity of 90% and the activity of 400 g of gluconic acid per g of Pt per hour.

Example 22. 5 g of the catalyst obtained in the conditions of example 5 from the table and containing 1 wt.% Palladium, placed in a cylindrical reactor, purged with an inert gas and without heating give a stream of hydrogen in a mixture with 1 vol.% Hexene-1. Chromatographic analysis of the gas mixture after leaving the reactor shows 99.9% conversion of the starting olefin, when it is converted by 93% to hexane and 7% to a mixture of cis and trans-hexenes with internal C = C bonds.

Example 23. 200 mg of the catalyst obtained in the conditions of example 8 and containing 0.24 wt.% Palladium, was placed in a reactor of a static circulation system with a volume of 0.7 l, restored in situ with hydrogen at 325 ° C for 0.5 h and purged the initial reaction mixture containing 1.4% acetylene, 67.7% ethylene, 11.8% hydrogen and 19.1% argon. The reaction is carried out at a temperature of 20 ° C, a pressure of 0.45 atm and a circulation speed of ~ 40 ml / sec. The change in concentration during the reaction is monitored chromatographically. Analysis of the mixture after 13 minutes shows that the catalyst provides> 99% acetylene conversion. The activity of the catalyst is 4.7 · 10 ^-3 mol / l min g Pd, selectivity 54%.

Example 24. The hydrogenation of acetylene on the catalyst obtained in example 9 and containing 0.24 wt.% Palladium and 0.25 wt.% Silver, is carried out at the same catalyst loading, the same feed and in the same reactor as in example 23 The activity of the catalyst was 1.1 · 10 ^-3 mol / l min g Pd, selectivity for acetylene 70%. Analysis of the mixture after 29 minutes shows that the catalyst provides> 99% acetylene conversion. Comparison with example 23 shows that the introduction of silver can increase the selectivity of hydrogenation of acetylene.

Example 25. 10 g of the catalyst obtained under the conditions of Example 7 from the table and containing 1.4 wt.% Palladium was placed in a cylindrical reactor, purged with an inert gas, reduced in hydrogen, and nitrobenzene was fed under controlled irrigation at 95 ° C in a stream of hydrogen. Chromatographic analysis of liquid products at the outlet of the reactor shows a complete conversion of nitrobenzene, with aniline selectivity> 98%.

Example 26. 1 g of the catalyst prepared according to example 7 from the table and containing 1.4 wt.% Palladium, is loaded into a tubular reactor. Purge the system with nitrogen, then with hydrogen. The control panel sets the temperature at 250 ° C and turns on the heating of the reactor. When the reactor reaches the set temperature, the supply of furfural begins at a rate of 0.086 cm ³ / min with a molar ratio of furfural and hydrogen of 1.0: 0.7. The duration of the experiment is 6 hours with gas chromatographic analysis of the products after 1 hour. For 6 hours of catalyst operation, the average furfural conversion is 64% with a relative furan yield of 69%.

Example 27 (prototype, example 1 in the description of the patent of the Russian Federation 2056939). 50 g of a granular carbon carrier is placed in a rotating drum, in which the free pore volume is 0.7 cm ³ / g, more than 95% of the pores have a size of less than 10 nm and the pore size distribution curve according to the adsorption data (Fig. 1a) contains sharp maximum at 4-5 nm. During the rotation of the drum, 22 ml of a palladium nitrate solution with a palladium concentration of 46.4 g / l and a free nitric acid concentration of 106 g / l are applied by irrigation (molar ratio Pd / nitric acid = 1: 3.8). A sample coated with palladium nitrate is placed in a tubular reactor and dried in a stream of air with increasing temperature for 1 h to 120 ° C and keeping at this temperature for another 2 hours. Replace the air with nitrogen and increase the temperature to 250 ° C. At this temperature, decomposition is carried out in a stream of nitrogen for 5 hours and cooled to 120 ° C. Replace the nitrogen with hydrogen and restore the catalyst at 150 ° C for 2 hours. Displace hydrogen at 120 ° C with nitrogen, cool the catalyst in a stream of nitrogen to 40 ° C. Get a catalyst with a palladium content of 2.0 wt.%. Moreover, 95% of palladium particles have a size of 2 to 8 nm (data from transmission electron microscopy). 1.5 g of the obtained catalyst is placed in a slowly rotating holder and kept under an inert atmosphere at 195-200 ° C for a certain time in the melt of gum pine rosin with an initial content of abietic acids of 53%. The catalyst provides a reduction in the content of abietic acid after 1 h to 16%, after 1.5 h to 10%, after 2 h to 5%.

Example 28 (prototype, example 12 in the description of the patent of the Russian Federation 2056939). 1.5 g of the catalyst was prepared in the holder, obtained as in Example 27, but with a palladium content of 1 wt.%, A palladium particle size of 2-8 nm and an active layer with a thickness of 20 μm, and rosin was disproportioned under the same conditions. The abietic acid content is 20% after 1 hour, 15% after 1.5 hours and 8% after 2 hours.

Example 29. The disproportionation of rosin is carried out under the same conditions, but with 1.5 g of the catalyst obtained in example 5 from the table and containing 1 wt.% Palladium. The abietic acid content after 1 h decreases to 15% and after 2 hours to 4.5%. Comparison with examples 27, 28 shows that the catalyst obtained by the present method and containing 1 wt.% Palladium, surpasses the productivity of the catalyst with the same palladium content obtained by the prototype, and provides a reduction in the content of abietic acid to the accepted norm at the same time as the catalysts obtained by the prototype and containing 2 times more palladium.

Example 30. The disproportionation of rosin is carried out under the same conditions, but when loading 1.5 g of the catalyst obtained in example 4 and containing 4 wt.% Palladium. The abietic acid content decreases to 9% after 1 hour, to 4% after 1.5 hours and to 3% after 2 hours. Comparison with example 29 shows that the inventive method allows to increase the productivity of the catalyst by increasing the palladium content.

Example 31 (for comparison with a catalyst obtained through hydrolysis of palladium chloride). The catalyst is prepared according to example 7 from the table, but at 210-220 ° C, after which the granular catalyst is separated, fresh rosin is added and the catalytic tests are repeated under the same conditions. Several such cycles are carried out with rosin replacement and each cycle lasting 2 hours. At the end of the first cycle, the residual abietic acid content is 1.5%, after the fifth 2.3%, after the 10th 2.5%. At the same time, the catalyst is prepared on the same support, but through the hydrolysis of palladium chloride with sodium carbonate under the conditions of Example 1 from [SU 1713172, 08.22.89], and it is tested according to the same procedure. At the end of the first cycle, the residual content of abietic acid is 0.0%, after the fifth 1%, after the 10th 2.5%. An example shows that the activity of the inventive catalyst in sequential cycles does not significantly decrease, while the catalyst obtained from palladium chloride rapidly loses activity.

Example 32. In an industrial reactor designed to disproportion of rosin, download 1.7 tons of catalyst containing 1.4 wt.% Palladium and obtained analogously to example 7 from the table, but in batches of 200 kg, and rosin is disproportionated at 175-185 ° With and the feed rate of 0.6 h ^-1 . In the first 1000 hours of operation, the catalyst provides rosin, which does not require additional vacuum distillation and has an acid number of 168-165 mg KOH / g with a residual abietic acid content of 0.1-1.3 wt.%.

Example 33 (for comparison with a process on an industrial catalyst). The rosin is disproportioned under industrial conditions on a PU catalyst with a palladium content of 1.8 wt.%, With the same catalyst loading, the same raw materials and in the same reactor as in Example 32. In this case, the disproportionation process corresponds to the required product quality. it is necessary to carry out at 230-260 ° C and the supply of rosin <0.2 h ^-1 ; the active time of the catalyst does not exceed 800 hours, with the acid number of the product decreasing by the end of this period from 160 to 153 mg KOH / g and the content of abietic acids increasing from 2 to 5%.

Example 34. The disproportionation process described in example 32 is continued for 3700 hours with a gradual increase in temperature by the end of this period to 215 ° C to ensure the residual content of abietic acids in the product at the same level; while the acid number remains at the level of 163-165 mg KOH / g rosin. After this time, the reactor is transferred to a cyclic mode of operation, with a periodic withdrawal from the "hot" circulation mode to the "cold" idle for a long time, sufficient to harden the rosin. After 12 such cycles and the total active time of 4466 h, the process of disproportionation with this catalyst requires the same temperature regime as when using a freshly loaded PU catalyst. The example provides further confirmation of the greater productivity, selectivity and stability of the inventive catalyst over the previously used catalyst and shows the possibility in this case of a batch process when the rosin is subjected to disproportionation as necessary.

As can be seen from the examples and tables, the present invention allows to obtain a catalyst in a high-tech way, characterized by high dispersion and resistance to sintering of palladium and / or platinum particles when the metal content varies over a sufficiently wide range, which provides the catalyst with increased productivity, selectivity and stability in oxidation processes, hydrogenation and hydrogen transfer, and the catalytic process - greater efficiency, thereby allowing the invention to find a wide application in the chemical industry.

room V _pp , ml Metal [metal], g / l [AK], g / l Drying conditions Thermal Decomposition Conditions Recovery Terms Me, wt.% D _{Pd, Pt} , nm one 40 Pd 160 210 N ₂ , 105 ° N ₂ , 220 °, 3 h H ₂ / He (1/4), H ₂ , 125-150 ° 6.0 2.5-2.2 2 2,5 Pd 80 150 Ar ₂ , 40-60 ° Ar, 215 °, 3 h H ₂ , 130-170 ° 0.2 4.3-3.6 3 fifty Pd 222 75 N ₂ , 105 ° N ₂ , 200 °, 2 h H ₂ / N ₂ (> 1/1), H ₂ , 140-160 ° 9.9 3.3-3.0 four 31 Pd 135 96 N ₂ , 90-105 ° N ₂ , 190 °, 2 h H ₂ / N ₂ (1/1), H _2, 125-200 ° 4.0 2.6-2.2 5 7 Pd 144 one hundred N ₂ , 90-105 ° N ₂ , 200 °, 3 h H ₂ / N ₂ , 125-200 ° one 3,5-3,3 6 twenty Pd 51 250 N ₂ , 90-105 ° N ₂ , 200 °, 3 h H ₂ , 125-150 ° one 1.6-1.3 7 twenty Pd 51 80 N ₂ , 90-105 ° N ₂ , 200 °, 3 h H ₂ / N ₂ , 125-200 ° 1.4 2.8-2.6 8 2,4 Pd 25 67 No, 90 ° Not, 200 °, 1 h H ₂ , 110-150 ° 0.24 2.6-2.5 9 2,4 Pd 25 67 No, 90 ° Not, 200 °, 1 h H ₂ , 110-150 ° 0.24 4.3-3.6 2,4 Ag 25 107 0.24 10 9,4 Pd 109 157 No, 90 ° Not, 200 ° C, 0.7 h H ₂ / Not (2/1), 110-150 ° 4.0 3.0-2.7 eleven 51 Pt 228 1100 No, 90 ° Not, 250 °, 1 h H ₂ , 250 ° 10 6.3-5.9 12* 51 Pt 228 1100 No, 90 ° Not, 250 °, 1 h H ₂ , 250 ° 10 3,5-3,1 13 55 Pt 202 1120 No, 90 ° Not, 250 °, 1 h H ₂ , 150-250 ° 10 2.4-2.0 fourteen 27 Pt 526 540 No, 90 ° Not, 250 °, 1 h H ₂ , 150-250 ° thirty 4.7-2.6 * the carrier is pretreated in 15 M HNO ₃ for 2 hours at 80 ° C

Claims (8)

1. A method of preparing a mono- or bimetallic catalyst for processes involving oxygen and / or hydrogen, comprising impregnating a carbon carrier with compounds of palladium and / or platinum or palladium and at least one of the metals of group I, characterized in that the carrier is pre-treated in nitric acid with a concentration of 3 to 15 M at a temperature not exceeding 80 ° C, an impregnating solution is prepared from nitric acid solutions of chloride-free compounds of palladium and / or platinum or palladium and at least one of the metals of I group PPs, their drying and decomposition is carried out in a stream of inert gas at a temperature not exceeding 105 ° C and from 150 to 350 ° C, respectively, the reduction is carried out in a stream of hydrogen at 110-350 ° C, under other conditions of deposition, drying, decomposition, recovery and the ratio of the starting components providing dispersed particles of platinum group metals of 1-10 nm in size, localized in pores of 2-20 nm in size, with the content of supported palladium and / or platinum from 3 to 50 wt.% or palladium and / or platinum and silver from 0.1 to 1.4 wt.%. 2. The method according to claim 1, characterized in that they use a carbon carrier obtained by thermal decomposition of hydrocarbons on soot granules with subsequent oxidative activation or without it and representing a carbon material with a pore volume of 0.2-1.7 cm / g, formed carbon layers with a thickness of 10-1000 nm with a radius of curvature of 10-1000 nm, a true helium density of 1.80-2.1 g / cm ³ , an X-ray density of 2.112-2.236 g / cm ³ and pore size distribution with maxima in region 3 -20 and 20-200 nm. 3. The method according to claim 1, characterized in that they use a carbon carrier obtained by the decomposition of methane or ethylene at temperatures from 600 to 700 ° C on a catalyst containing supported on aluminum oxide metal nickel and iron or nickel and copper and representing a carbon material with a specific surface for nitrogen adsorption from 105 to 260 m ² / g, mesopore surface from 95 to 240 m ² / g, micropore volume from 0.01 to 0.02 cm ³ / g, total pore volume from 0.31 to 0 , 4 cm ³ / g and an average pore diameter of from 6.2 to 17.5 nm. 4. Processes involving oxygen, hydrogen and organic compounds using a mono- or bimetallic catalyst prepared by impregnation of a carbon carrier, characterized in that they use a catalyst prepared according to any one of claims 1 to 3. 5. The process according to claim 4, characterized in that the process consists in the oxidation of alcohols to aldehydes and carboxylic acids. 6. The process according to claim 4, characterized in that the process consists in the hydrogenation of olefin, acetylene and diene bonds in aliphatic and carbocyclic compounds. 7. The process according to claim 4, characterized in that the process consists in the hydrogenation of nitro compounds to amines or intermediate compounds. 8. The process according to claim 4, characterized in that the process consists in the disproportionation of abietic and other resin acids contained in rosin and similar mixtures of natural or artificial origin.