RU2414964C1 - Catalyst for hydrogenating plant oil and fats, preparation method thereof and hydrogenation method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to catalysts, particularly used in hydrogenating plant oil and unsaturated fats and can be used in food, perfumery, pharmaceutical, petrochemical and oil-refining industry. Described is a catalyst which contains palladium in amount of 0.1-5.0 wt % and ruthenium in ratio Pd:Ru=1-100 in form of bimetallic particles with size 1-6 nm deposited on a carbon support. Described is a method of preparing the catalyst, involving preliminary combined hydrolysis of palladium (II) and ruthenium (III) chlorides at pH 5-10 and then bringing the precursor into contact with the carbon support and liquid-phase reduction. Described also is a method of hydrogenating triglycerides of plant oil and fats at temperature 80-200°C and pressure 2-15 atm using the catalyst described above.

EFFECT: high efficiency of the method of preparing the catalyst.

2 cl, 5 ex, 2 tbl

Description

The invention relates to the field of catalysts used, in particular, in the hydrogenation of vegetable oils and unsaturated fats, and can be used in the food, perfumery, pharmaceutical, petrochemical and oil refining industries.

Catalysts for the hydrogenation of vegetable oils based on transition metals Mo, W, Rh, Ir, Ru, Os, Ti, Re, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, Zn, Ga, etc. (JIGray and LF Russel, J. Am. Oil Chemists' Soc. 56 (1979) 36-44). The most widely used are Ni-containing catalysts, mainly Ni-Raney, but they are inferior in activity to catalysts based on noble metals (palladium, platinum, ruthenium), in the presence of which the necessary degree of hydrogenation of vegetable oils is achieved under milder conditions (at relatively low temperatures and H ₂ pressure) and lower catalyst loading (for example, the palladium catalyst loading is about 50 ppm, i.e., from 1/10 to 1/40 of Ni-Raney). Features and prospects for the use of noble metals in the hydrogenation of vegetable oils are presented in reviews (PNRylander (PNRylander, J. Am. Oil Chemists' Soc. 47 (1970) 482-486) and ESJang et al. (ESJang, MYJung, DBMin. Comprehensive reviews in food science and food safety 1 (2005) 22-30) .In them, it is noted, in particular, that in terms of activity in the hydrogenation of multiple C — C bonds of fatty acids, these metals are in the series Os, a no formation of trans isomers in partially hydrogenated products, which are undesirable for food use, is Pt <Ir <Ru ~ Rh <Pd. Highly characteristic for platinum catalysts a fraction of the products of the complete hydrogenation of fats. Be that as it may, the mild conditions for the use of catalysts based on these metals make it possible that even in the case of the most active of them, palladium, the yield of trans isomers is close to that characteristic of nickel catalysts. trans-isomers in the products of hydrogenation of vegetable oils on palladium catalysts can be achieved by controlled poisoning of the surface of metal particles with nitrogen-containing compounds (ammonia, organic amines, nitrogen-containing heterocycles) or transition metal ions (silver, tin, bismuth, molybdenum, etc.). Their required modification with respect to selectivity for trans isomers without loss of catalytic activity is achievable when another, less active, noble metal, usually platinum and ruthenium, is introduced into the catalyst. The latter, due to its cheapness and activity in the hydrogenation processes of multiple C – C bonds, may be of interest in terms of replacing some of the more expensive palladium in oil hydrogenation catalysts.

Noble metals are deposited in the form of nanoparticles on the surface of oxide carriers (SiO ₂ , Al ₂ O ₃ , aluminosilicates, TiO ₂ , etc.), insoluble salts (BaSO ₄ ), as well as porous carbon materials in an amount of 0.1-2 wt.%. The hydrogenation process with the participation of supported catalysts is carried out mainly in a batch mode using a catalyst suspended in oil in the temperature range of 80-250 ° C at atmospheric or elevated pressures by supplying hydrogen to the catalyst powder suspension, the fraction of which does not exceed 100 microns. The role of the substrate is not only to maintain a highly dispersed state of the active component, but also to modify its catalytic properties, which is due to both the metal-carrier interaction and the nature of the distribution of metal over the grain and in the pores of the carrier. The metal-carrier interaction effect has been studied rather poorly. It is usually masked by the influence of impurities or ions inherent in the structure of the support of the carrier, adsorbed on the surface of the metal particles and change their catalytic properties. The effects of the size of metal particles and their distribution over the grain and in the pores of the support are associated with the large sizes of triglycerides of fatty acids and the diffusion mode of the process of their hydrogenation. Thus, using the example of Pd / C catalysts, it was shown that, with a decrease in the size of palladium particles and the thickness of their crust distribution over the carbon support grain, the activity of the catalysts increases and their selectivity with respect to the cis isomers of partially hydrogenated products (B. Nohair, C. Especel, P .Marécot, C. Montassier, LCHoang, J. Barbier, CRChemie 7 (2004) 113; OASimakova, PASimonov, AVRomanenko, ILSimakova, React. Kinet. Catal. Lett. 95 (2008) 3-12). However, a combination of various manifestations of all these factors, apparently, can also lead to the fact that the catalytic properties of a set of randomly selected catalysts on various supports turn out to be independent of the nature of the support: for example, in the early studies, the absence of any advantages between palladium catalysts on carbon and alumina, with no details of the state of the metal on the carriers (A.E. Johnston, D. MacMillan, HJ Dutton and JCCowan, J. Am. Oil Chemists' Soc. 89 (1962) 273). At the same time, carbon materials, as carriers for such catalysts, attract attention due to their chemical resistance, wide variability of physicochemical properties, ability to stabilize noble metal nanoparticles with respect to sintering, and also because of the ease of metal extraction from spent catalysts.

Traditionally, the deposition of palladium on the supports is carried out using acidic solutions of palladium (II) chloride, which is able to firmly adsorb onto the surface of a number of supports, such as alumina and carbon materials. Thus, carbon carriers (CN) of graphite nature, which include Sibunit, soot, activated carbons, firmly adsorb up to 0.1 μmol H ₂ PdCl ₄ on 1 m ^{2 of} the carrier surface (PASimonov, VALikholobov, Catal. And Electrocatal. At Nanoparticle Surfaces (A Wieckowski, ERSavinova, CGVayenas, eds.), 2003, Marcel Dekker, New York, pp. 409-454). Thus, CNs with a surface of 300–500 m ² / g are capable of adsorbing up to 3-5 wt.% Metal from H ₂ PdCl ₄ solutions, which means that the catalysts obtained by contacting H ₂ PdCl ₄ with CNs are 0.1–2% Pd / C for the hydrogenation of fatty acids are classified as adsorption catalysts according to the classification of G.K. Boreskov according to the method of preparation (G.K. Boreskov, Heterogeneous catalysis, M .: Nauka, 1988). Palladium adsorbed from H ₂ PdCl ₄ solutions can be in the form of coarse metal crystallites (10-1000 nm) concentrated on the periphery of grains of CNs, as well as in the form of surface complexes of palladium chloride uniformly distributed over the grain of CNs. During subsequent recovery, the complex form of the adsorbed metal gives highly dispersed (1-3 nm) metal particles. With an increase in the adsorbed palladium content on the support, the fraction of the metal form decreases, while the complex form increases. However, none of these forms of adsorbed metal can fully satisfy the requirements that should be followed when designing Pd / C catalysts effective in the hydrogenation of fatty acids. The metal form, although it has a crustal distribution over the CN grain, is inactive due to the too coarse dispersion of its crystallites. The complex form, although it usually leads to highly dispersed metal particles, also gives low activity catalysts in the hydrogenation of fats due to the unsatisfactory distribution of metal over the CN grain (OA Simakova, PASimonov, AVRomanenko, ILSimakova, React. Kinet. Catal. Lett. 95 (2008) 3-12).

- будут способствовать формированию катализаторов Pd/C с состоянием активного компонента, удовлетворяющим требованиям, предъявляемым к высокоэффективным катализаторам гидрирования жирных кислот.A promising approach to the synthesis of palladium catalysts highly effective in the hydrogenation of vegetable oils deposited on CNs is a preliminary hydrolysis of H ₂ PdCl ₄ to contact with the support with the formation of polynuclear hydroxocomplexes of palladium (II) or PGA (O.A.Simakova, PASimonov, AVRomanenko , ILSimakova, React. Kinet. Catal. Lett. 95 (2008) 3-12), for which the adsorption capacity of CNs is ten times higher than the adsorption capacity for H ₂ PdCl ₄ (PASimonov, VALikholobov, Catal. And Electrocatal. At Nanoparticle Surfaces (A.Wieckowski, ERSavinova, CGVayenas, eds.), 2003, Marcel Dekker, New York, pp. 409-454). A number of unique properties of PGA are small size (1-3 nm), high sorption activity and low redox potential

- will contribute to the formation of Pd / C catalysts with the state of the active component that meets the requirements for highly effective catalysts for the hydrogenation of fatty acids.

Traditionally, the introduction of the second component in the prepared bimetallic catalyst is carried out either by co-impregnation of the support with metal complexes, or by adding to the already prepared monometallic sample. In both cases, the constancy of the chemical composition and particle structure of the active component of the final catalyst is not guaranteed due to differences in solubility and interaction of the applied precursors with the surface of the substrate, which can lead to segregation, as well as a mismatch in the nature of the distribution of both components in the pores of the carrier. In this regard, the joint hydrolysis of noble metal salts seems very promising because of their ability to adsorb on hydroxides and oxides of transition metals and form mixed hydroxocomplexes (S.I. Pechenyuk, Sorption-hydrolytic deposition of platinum metals on the surface of inorganic sorbents, L .: Nauka, 1991). This approach leads to a more uniform composition of the active component of a noble metal bimetallic catalyst (WO 2008/093243 (Int. Applicat. No PCT / IB2008 / 000754), Appl. Date 01/29/2008, Prior. Date 01/30/2007, Publ. Date 08/07/2008; Pat. RF 2146172).

The present invention provides a method for preparing a palladium-ruthenium catalyst supported on a carbon powder carrier effective in the process of partial hydrogenation of vegetable oils in a batch (cyclic) mode.

A known method (RU 2260037, C11C 3/12, 09/10/2005) for producing salomas by liquid-phase hydrogenation of vegetable oils with hydrogen in the presence of a palladium catalyst supported on a carbon carrier, nanocluster palladium is used as a palladium catalyst, nanocarbon cluster material is used, this process is carried out at a temperature of from 60 to 90 ° C.

This technical solution is taken as a prototype of the present invention.

The disadvantage of this method is the low speed of the process of hydrogenation of vegetable oils, obviously, due to the coarse particle size of palladium (up to 10 nm) and, probably, a wide distribution of the active component over the grain of the carrier, which reduces the productivity of the reactor equipment (reactors) in which the catalyst is used. In particular, on page 3 of the description of the invention (example 1) it is noted that the process is carried out for 6 hours. Traditionally, hydrogenation processes are carried out at significantly shorter times, see patent RU 2105050, С11С 3/12, 20/02/1998 (examples 1 and 2), where the hydrogenation time is 60 and 90 minutes, respectively.

Thus, the implementation of the hydrogenation process according to the prototype at temperatures of 60-90 ° C provides a low content of trans isomers in the hydrogenation products (30-32%) with a long process time (see table, page 4), which is 4-6 hours .

The present invention solves the problem of preparing a highly dispersed bimetallic catalyst for the hydrogenation of vegetable fats, ensuring the implementation of the process with high performance at a given quality of the resulting salomas (content of trans isomers and the value of the iodine number).

The problem is solved by the creation and application of a bimetallic catalyst deposited on the surface of a carbon carrier containing palladium in an amount of 0.1-5.0 wt.% And ruthenium in an atomic ratio of Pd: Ru = 1-100 in the form of bimetallic particles 1-6 nm in size.

As the carbon material, you can use mesoporous synthetic graphite-like material or composite porous materials based on pyrocarbon with a specific surface area of 10-500 m ² / g, with an average mesopore size in the range from 4 to 40 nm.

The problem is solved by a method for preparing a bimetallic catalyst for the hydrogenation of vegetable oils, which involves the preliminary synthesis of a metal precursor by the combined hydrolysis of palladium (II) and ruthenium (III) chlorides at a pH of 5-10, followed by contacting the precursor with a carbon carrier, i.e. subsequent adsorption of the obtained mixed polynuclear hydroxocomplexes of metals on a carbon powder carrier (fraction 50-250 μm), liquid-phase reduction, filtration, washing the catalyst with water and final drying. The synthesis of the precursor is carried out for 0.2-60 minutes at a temperature of 10-50 ° C.

The main variable parameters in the synthesis of such catalysts are: - pH (5-10), temperature (10-50 ° C) and aging time (0.2-60 min) of a solution of polynuclear hydroxocomplexes; - concentration and molar ratio of reagents (H ₂ PdCl ₄ , RuCl ₃ ) in solution during the formation of polynuclear hydroxocomplexes.

Distinctive features of the present invention in comparison with the prototype are:

1) a higher dispersion of the deposited metal (particle size 1-6 nm), leading to a higher activity of the catalyst,

2) a bimetallic composition of the active component of the catalyst.

The process of hydrogenation of vegetable oils using the above catalyst is carried out at a temperature of 80-200 ° C, a hydrogen pressure of 2 to 15 atm and a specific catalyst consumption of 0.05-0.2 g _ct / kg of vegetable oil.

The invention is illustrated by the following examples.

Example 1. In a glass reactor equipped with a jacket, with vigorous stirring, a suspension of 5 g (in terms of dry weight) of a powder of mesoporous synthetic carbon material brand "Sibunit" and 50 cm ^{3 of} water is prepared. The suspension is stirred for 20 minutes at room temperature, and then the temperature of the suspension (t) is adjusted to the desired value using a water thermostat. With a two-channel peristaltic pump, a solution of palladium (II) and ruthenium (III) chlorides in hydrochloric acid and a solution of sodium carbonate are brought to a suspension temperature in the reactor at the same time in a flowing mixing tank. The volumetric feed rates of the solutions are maintained so as to ensure the contact time of the solutions in the range of τ = 0.2-60 min. The ratio of the amounts of these reagents is such as to provide the required weight content of metals in the final catalyst (palladium 0.1-5.0 wt.% And ruthenium in the atomic ratio = 1-100), as well as the necessary acidity of the resulting mixture of solutions (pH 5-10 ) The mixture of solutions at the outlet of the mixing tank is discharged directly into the coal suspension in the reactor. At the end of the dosing of the reagents, the suspension is allowed to age with moderate stirring for 1 h, then the reactor is heated to 60 ° C, sodium formiate solution is added in a molar ratio of NaOOCH / (Pd + Ru) = 2 and left to mix for another 1 hour. At the end, the reactor is cooled, and the resulting catalyst is filtered off and washed with distilled water until the mother liquor with AgNO ₃ reacts negatively to the presence of chlorine ions, and then dried in a vacuum oven at 90 ° C.

Examples 2-5.

Similar to example 1.

Physico-chemical characteristics of the catalysts depending on the parameters of their synthesis are given in table 1. For comparison, data are given for sample No. 3 from the prototype (RU 2260037, C11C 3/12, 09/10/2005).

The catalyst tests are carried out in a 150 ml stainless steel autoclave, thermostatically controlled and equipped with an electromagnetic stirrer. A portion of the catalyst in an amount of 180 mg and refined sunflower vegetable oil in an amount of 18 g are placed in an autoclave. The process is carried out at a pressure of 9 atm and a temperature of 140 ° C for 30 minutes Then the catalyst is separated on a heated filter and the physicochemical parameters of the obtained salomas are analyzed (fatty acid composition according to GOST R5148399, the content of trans isomers according to GOST R55100-2003, iodine number according to the standard method) (Guide to research methods, technological control and accounting for production in the oil and fat industry, Leningrad, 1982, v.1, p.908). Before reuse, the catalyst is washed with a solvent. Re-use the catalyst up to 20 times.

The results averaged over 20 cycles are shown in Table 2.

table 2 Catalytic properties of catalysts in the hydrogenation of sunflower oil. For comparison, the data of sample No. 3 from the prototype (RU 2260037, C11C 3/12, 09/10/2005) Example T, ° C Process time, min The Iodine Number, J _2/100 The content of trans isomers,% Fatty acid composition,% from 16: 0 from 18: 0 from 18: 1 from 18: 2 one 140 thirty 72.8 28.6 6.1 5.3 47.8 40,2 3 140 fifty 65.9 32.1 6.5 20,0 69.6 3.3 5 160 twenty 69.0 30.3 7.0 17,2 72,4 2,8 Prototype
RU 2260037 90 240 74.5 32,4 6.6 17.0 67.0 8.1

Claims (4)

1. The catalyst for the hydrogenation of triglycerides of vegetable oils and fats, containing palladium in an amount of 0.1-5.0 wt.%, Deposited on a carbon carrier, characterized in that it contains palladium and additionally ruthenium in the atomic ratio Pd: Ru = 1-100 in the form of bimetallic particles 1-6 nm in size. 2. A method of preparing a catalyst for the hydrogenation of triglycerides of vegetable oils and fats according to claim 1, characterized in that the metal precursor is preliminarily synthesized by the joint hydrolysis of palladium (II) and ruthenium (III) chlorides at pH 5-10, followed by contacting the precursor with a carbon carrier , then carry out the phase of liquid phase recovery. 3. The method according to claim 2, characterized in that the synthesis of the precursor is carried out for 0.2-60 minutes at a temperature of 10-50 ° C. 4. The method of hydrogenation of triglycerides of vegetable oils and fats, characterized in that the process is carried out at a temperature of 80-200 ° C and a pressure of 2-15 atm using the catalyst according to claim 1 or prepared according to any one of claims 2 and 3.