RU2438776C1 - Palladinised nanotubes for hydrogenation of plant oil, preparation method thereof and method for liquid-phase hydrogenation - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to catalysts for hydrogenation of plant oil and fats. Described is a palladium catalyst which is deposited on a carbon support for liquid-phase hydrogenation of plant oil and fats, characterised by that the carbon support used is in form of carbon nanotubes with external diameter ëñ18 nm, wherein the specific surface area of catalytically active palladium on the surface of the carbon support is equal to 90-140 m2/g. The invention describes a method of preparing the described catalyst, involving deposition of palladium on the surface of the carbon support, characterised by that deposition is carried out via hydrolysis of chloride complexes of Pd (II) in the presence of sodium carbonate, followed by liquid-phase reduction with sodium formate to Pd (0), filtering, washing the catalyst with water and drying. The carbon support used is carbon nanotubes with external diameter ëñ18 nm. A catalyst with specific surface area of the catalytically active palladium deposited on the surface of the carbon support equal to 90-140 m2/g is obtained and the catalyst is used in the method for liquid-phase hydrogenation of plant oil and fats. ^ EFFECT: high activity of the catalyst and reduced formation of trans-isomers when producing hydrogenated fat for food purposes. ^ 5 cl, 3 tbl, 4 ex

Description

The invention relates to the field of catalysts, in particular for the hydrogenation of vegetable oils and fats, and can be used in the food, perfumery, 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). In this series, Ni-containing catalysts are most widely used. However, 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 temperature and H ₂ pressure) and lower catalyst loading. Features and prospects for the use of noble metals in the hydrogenation of vegetable oils are presented in the 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). They noted, in particular, that in terms of activity in the hydrogenation of multiple C — C bonds of fatty acids, these metals are arranged in a series: Pd>Rh> Pt >>Ir> Ru >> Os, and in the formation of trans isomers in partially hydrogenated products, which are undesirable for food use, - Pt <Ir <Ru ~ Rh <Pd. Platinum catalysts are also characterized by a high proportion of the products of the complete hydrogenation of fats.

The hydrogenation process involving such catalysts is carried out mainly in a batch mode using a suspended catalyst. The synthesis of salomas is carried out in the temperature range of 80-250 ° C at atmospheric or elevated pressures by supplying hydrogen to a suspension of the catalyst in oil. This regime imposes a number of additional requirements on the catalysts related to the peculiarity of their operation. The powder catalyst should be easily separated (filtered out) from the reaction products and have good reuse properties.

The present invention provides a method for preparing a palladium catalyst powder deposited on a carbon substrate, effective for processing vegetable oils in a batch (cyclic) mode.

The activity and selectivity of Pd-containing catalysts for the hydrogenation of vegetable oils, fats and fatty acids depend on many factors, such as the content of the metal or metals of group VIII in the catalyst, the type of substrate, the method by which metal or metals of group VIII were deposited on the substrate, and also from the distribution of metal or metals in the pores of the carrier.

A known catalyst (RU 2323046, B01J 37/02, 04/27/2008) for the processing of vegetable oils and distilled fatty acids, including crystallites of catalytically active palladium deposited on the surface of a carbon material, characterized in that mesoporous graphite-like material with a granule size is used as a carbon material 0.5-6.0 mm, with a specific surface area of 100-450 m ² / g, with an average mesopore size in the range from 4 to 40 nm, with a total pore volume of 0.2-0.6 cm ² / g and a fraction of mesopores in a total pore volume of at least 0.6, in which palladium crystallites They are distributed in the volume of the granules of the carbon material so that the distribution maximums of the active component are located at a distance from the outer surface of the granules corresponding to 1-30% of its radius, with the applied palladium content in the range from 0.5 to 2.0 wt.%.

The disadvantage of this catalyst is the large size of the granules (0.5-6.0 mm), which allows its use only in reactors with a fixed catalyst bed, and low productivity.

There is also known a 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. Palladium nanocluster is used as a palladium catalyst, nanocarbon cluster material is used as a carbon support, and the process is carried out at a temperature of 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 hydrogenation process of vegetable oils, which reduces the productivity of the equipment 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 examples 1 and 2 in patent RU 2105050, C11C 3/12, 02.20.1998, where the hydrogenation time is 60 and 90 minutes, respectively. Thus, the implementation of the hydrogenation process of the prototype at temperatures of 60-90 ° C provides a low content of hydrogenation products of trans-isomers (30-32%) with a long process time, which is 4-6 hours

The present invention solves the problem of preparing a catalyst for the hydrogenation of oils, ensuring the implementation of a process with high productivity 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 use of a catalyst comprising catalytically active palladium supported on a carbon support with a specific surface area of the supported metal of 90-140 m ² / g. As a carbon carrier, mesoporous synthetic graphite-like materials with a total pore volume of 0.3-1.8 cm ³ / g and an average pore size in the range from 10 to 23 nm, in particular carbon nanotubes (CNTs) with an external diameter of ≤18, can be used nm

The problem is solved by a method of preparing a catalyst for the processing of vegetable oils, which includes the deposition of palladium oxide on the surface of a mesoporous synthetic graphite-like carrier with a total pore volume of 0.3-1.8 cm ³ / g and an average pore size in the range from 10 to 23 nm by hydrolysis of chloride Pd (II) complexes in the presence of sodium carbonate, followed by liquid phase reduction with sodium formate to Pd (0), filtering, washing the catalyst with water and final drying. The specified method provides the synthesis of a highly dispersed catalyst with a specific surface area of the deposited metal of 90-140 m ² / g

The problem is also solved by the method of liquid-phase hydrogenation of vegetable oils and fats, which is carried out in the presence of the catalyst described above.

In such highly dispersed catalysts combining the dispersion of the active component on the surface of mesopores available for reagents, a high degree of utilization of the active component, palladium, is realized in the preparation of edible salomas.

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

1) a high surface (90-140 m ² / g) of catalytically active palladium in the surface layer of the carbon material;

2) the use of a mesoporous synthetic graphite-like material as a carrier with a total pore volume of 0.3-1.8 cm ³ / g and an average pore size in the range from 10 to 23 nm, including carbon nanotubes with an external diameter of ≤18 nm.

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 12 atm and a specific catalyst consumption of 0.05-0.4 g _ct / kg (in the description of the experiment 0.2 g / kg for 1 cycle ) vegetable oil.

The invention is illustrated by the following examples.

Example 1

4.95 g of SC3-2 carbon nanotubes (in terms of dry carrier) of a fractional composition of 70-100 microns are placed in a 100 cm ³ glass reactor equipped with a magnetic stirrer, 40 ml of distilled water are added, and stirred for 20 minutes. All subsequent operations are carried out with stirring the suspension in the reactor.

At room temperature, 9.4 ml of a solution of palladium hydrochloric acid (0.05 M) are metered into the reactor with a peristaltic pump.

To precipitate palladium on the surface of the carbon material, a solution of sodium carbonate (0.1 M) is introduced into the suspension. When dosing a solution of sodium carbonate, the acidity of the suspension is measured, which should not exceed pH 8. At the end of dosing the Na ₂ CO ₃ solution, the suspension is left to age with moderate stirring for 20 minutes, then the reactor is heated to 60 ° C, a 0.1 M solution is added sodium formate in a molar ratio of NaOOCH / Pd = 2 and allowed to stir for another 0.5 hours. Then the reactor is cooled and the resulting catalyst is filtered and washed with distilled water until the mother liquor reacts negatively with AgNO ₃ to the presence of chlorine ions, and then dried in a vacuum oven at 90 ° C.

The characteristics of the SC3-2 CNT and the catalyst based on it are given in Tables 1 and 2, respectively.

Testing of the catalyst is carried out in a thermostatically controlled 150 ml stainless steel autoclave equipped with a magnetic stirrer. For this, 10 mg of catalyst and 50 g of EFKO sunflower oil are introduced into the reactor. The system is purged with nitrogen, then the nitrogen is displaced with hydrogen. The process is carried out at a pressure of 9 atm and a temperature of 195 ° C. Then the catalyst is separated on a heated filter and the physicochemical parameters of the obtained salomas are analyzed: the fatty acid composition is determined according to GOST R5148399, the content of trans isomers is determined according to GOST R55100-2003, the iodine number is determined according to the standard method (Guidance on research methods, technological control and accounting for production in the oil and fat industry. - L., 1982, t.1, p.908). The hydrogenation process to obtain salomas with an iodine number of 72 is 8 minutes.

Example 2

The catalyst is prepared and tested according to example 1. At the same time, a SC4-1 CNT of a fractional composition of 70-100 μm is used as a carrier. The characteristics of the carrier and the catalyst based on it are shown in tables 1 and 2, respectively. The hydrogenation process to obtain salomas with an iodine number of 78 is 11 minutes.

Example 3

The catalyst is prepared and tested according to example 1. In this case, a SC4-1ox CNT with a fractional composition of 70-100 μm obtained by SC4-1 oxidation is used as a carrier. The characteristics of the carrier and the catalyst based on it are shown in tables 1 and 2, respectively. The hydrogenation process to obtain salomas with an iodine number of 77 is 21 minutes.

Example 4

The catalyst is prepared and tested according to example 1. At the same time, CNT “SC4-2” with a fractional composition of 70-100 μm is used as a carrier. The characteristics of the carrier and the catalyst based on it are shown in tables 1 and 2, respectively. The hydrogenation process to obtain salomas with an iodine number of 70 is 8 minutes.

The characteristics of the final products are shown in table 3.

Before reuse, the catalyst is washed with a solvent. Subsequently, it can be used at least 10 times.

For comparison, tables 1-3 show the data for the prototype (RU 2260037).

Table 1 Physicochemical Properties of Carbon Carriers Used to Prepare Pd / C Catalysts Example Texture characteristics of media ¹⁾ The outer average diameter of the CNT (d _cf ) ²⁾ Ash content Designation Specific Surface Area (S _BET ) The total pore volume (V _∑ ) Micropore Volume (V _mi ) The average pore size (D _cf ) No. - m ² / g cm ³ / g cm ³ / g nm nm wt.% one SC3-2 123 0.333 0,000 10.8 17.6 0.1 2 SC4-1 319 1,629 0,000 20,4 <10 0.1 3 SC4-1ox 341 1,803 0,000 21.1 17.0 0.1 four SC4-2 220 1,258 0,000 22.9 12.7 0.1 Prototype RU 2260037 Cluster Soot 120 ¹⁾ The parameters of the porous structure of coal were determined by adsorption of N ₂ at 77 K using an ASAP 2400 automatic volumetric setup (Micrometritics). Using the initial portion of the adsorption isotherm N ₂ in the region Р / Р ₀ = 0.05-0.2, we calculated the specific surface area by BET (S _BET ), and by the amount of adsorption N ₂ when Р / Р ₀ = 0.98, the total pore volume (V _∑ ) with diameter <110 nm. The volume of micropores (V _mi ) available for nitrogen at 77 K was determined by a comparative method (A.P. Karnaukhov et al., Pure Appl. Chem., V. 61. (1989) 1913-1920). The average pore diameter (D _cf ) was calculated by BET models as D _cf = 0.4 · V _∑ / S _BET . ²⁾ The outer average diameter of the CNTs (d _{cp /} ) was determined from their electron microscopic images.

table 2 Characteristics of Pd / C Catalysts Example Carrier Pd content Dispersion (D) ¹⁾ Surface pd No. designation wt.% CO / Pd m ² / g one SC3-2 1,0 0.27 129 2 SC4-1 1,0 0.28 133 3 SC4-1ox 1,0 0.19 91 four SC4-2 1,0 0.29 138 Prototype (RU 2260037 C1) Cluster Soot 0.4 ^{1) The} dispersion (D) of the obtained catalysts was determined by the pulsed method for the chemisorption of CO at 20 ° C. The value of D is calculated based on the stoichiometry of CO / Pd _s = 1: 1 (mol / mol).

Table 3 The fatty acid composition of salomas samples obtained during hydrogenation in the presence of catalysts of 1 wt.% Pd / C (fraction 70-100 μm). Experimental conditions: Т = 195 ° С, Рн ₂ = 9 atm, catalyst loading - 10 mg, EFKO sunflower oil - 50 g. Example Media number Reaction time Iodine number Sod. trans isomers Fatty Acid Composition min I ₂ g / 100 g % From 16: 0 From 18: 0 C 18: 1 From 18: 2 one SC3-2 8 71.88 30,4 4.67 16.39 73.97 4.97 2 SC4-1 eleven 78.31 31.7 6.12 10.25 75.88 7.75 3 SC4-lox 21 76.96 32.8 7.19 11.57 72.67 8.56 four SC4-2 8 70.37 30.5 6.63 14.65 75.28 3.44 Prototype (RU 2260037 C1) ¹⁾ Cluster Soot 240 74.5 32,4 6.6 17.0 67.0 8.1 ¹⁾ Experimental conditions for the prototype: T = 90 ° C, pH ₂ = 1 atm, catalyst loading - 500 mg, Sloboda sunflower oil - 60 g.

Claims (5)

1. The palladium catalyst deposited on a carbon carrier for liquid-phase hydrogenation of vegetable oils and fats, characterized in that it contains carbon nanotubes with an external diameter of ≤18 nm as a carbon carrier, while the specific surface area of the catalytically active palladium on the surface of the carbon carrier is 90 -140 m ² / g. 2. The catalyst according to claim 1, characterized in that the carbon nanotubes have a total pore volume of 0.3-1.8 cm ³ / g and an average pore size in the range from 10 to 23 nm. 3. A method of preparing a palladium catalyst for liquid-phase hydrogenation of vegetable oils and fats, including the deposition of palladium oxide on the surface of a carbon carrier, characterized in that the deposition is carried out by hydrolysis of chloride complexes Pd (II) in the presence of sodium carbonate, followed by liquid-phase reduction with sodium formate to Pd (0 ), by filtering, washing the catalyst with water and drying, carbon nanotubes with an external diameter of ≤18 nm are used as a carbon carrier, and a catalyst with separately deposited catalytically active surface of palladium on the carbon support surface of 90-140 m ² / g. 4. The method according to claim 3, characterized in that the carbon nanotubes have a total pore volume of 0.3-1.8 cm ³ / g and an average pore size in the range from 10 to 23 nm. 5. The method of liquid-phase hydrogenation of vegetable oils and fats, characterized in that it is carried out in the presence of a catalyst according to any one of claims 1 and 2 or prepared according to any one of claims 3 and 4.