RU2806584C1 - Method for hydroconversion of rapeseed oil - Google Patents

Abstract

FIELD: hydroconversion.

SUBSTANCE: method for hydroconversion of rapeseed oil by contacting it in a reactor with a catalyst - a micromesoporous composite obtained by hydrothermal-microwave synthesis, based on microporous MFI zeolite and a mesoporous second component, at elevated temperature and atmospheric pressure while simultaneously feeding hydrogen into the reactor to obtain a mixture of olefins C -C₄ and benzene-toluene-xylene fraction containing p-xylene. A composite based on microporous zeolite and a mesoporous second component - silicon carbide - MFI/SiC is used as a micromesoporous composite, and the porous structure of the composite is characterized by a volume of micropores equal to 0.14-0.18 cm³/g, and mesopores - 0.05-0.07 cm³/g, and the hydroconversion of rapeseed oil is carried out in a heated flow-type reactor, in which the catalyst is placed in its middle part, while the free volume of the reactor before and after the catalyst is filled with quartz chips, first the reactor with the placed catalyst is heated into it in a stream of hydrogen to a temperature of 430-470°C for an hour, then rapeseed oil is fed at a mass feed rate of 2.9-3.3 g/g cat. h.

EFFECT: increasing the yield of benzene-toluene-xylene fraction to 24 wt.%, increasing the yield of xylenes to 9 wt.%, increasing selectivity for p-xylene among isomers to 76 wt.%, reducing the hydroconversion temperature to 430-470°C, which simplifies the process as a whole, increasing the intensification of the process by increasing the feed rate of raw materials to 2.9-3.3 g/g cat. h.

1 cl., 4 ex, 2 tbl

Description

The invention relates to the field of chemical technology, namely to the catalytic processing of rapeseed oil by hydroconversion, producing benzene-toluene-xylene fraction, in particular p-xylene, which is a valuable intermediate product for petrochemicals for the synthesis of terephthalic acid and polyethylene terephthalate - the most produced polymer in the world in today, as well as obtaining a mixture of C ₂ -C ₄ olefins.

Currently, increasing attention is being paid to developing methods for producing valuable petrochemical intermediates that comply with the principles of green chemistry, such as the use of renewable raw materials and catalytic processes.

Such raw materials include, for example, vegetable oils, which contain triglycerides of fatty acids. The main acids that make up vegetable oils are palmitic, stearic, oleic, linoleic and linolenic.

Thus, there is a known method for the conversion of oleic acid into aromatic hydrocarbons of the BTX fraction (S. He, FGH Klein, TS Kramer, A. Chandel, Z. Tegudeer, A. Heeres, HJ Heeres. Catalytic conversion of free fatty acids to bio-based aromatics: a model investigation using oleic acid and a H-ZSM-5/Al ₂ O ₃ catalyst. // ACS Sustainable Chemistry and Engineering, 2021, V.9, PP. 1128-1141). The process is carried out at 550°C, atmospheric pressure, mass flow rate of oleic acid 1 h ^-1 . On the HZSM-5/Al ₂ O ₃ catalyst, the total yield of m- and p-xylenes did not exceed 5%.

The disadvantages of the method are the low total yield of m- and p-xylenes, as well as the lack of high-quality separation and identification of p-xylene, while p-xylene is the most popular of the isomers, as is known from the work of [Kim S., Ashpina O. Conjuncture of the world and Russian p-xylene market in 2005-2008 // The Chemical Journal (Russia). - 2006. - V. 03. - pp.38-43.], which is confirmed by the data presented in Table 1 below.

The search for renewable raw materials, the conversion of which would make it possible to obtain valuable petrochemical intermediates, including p-xylene, is a very urgent task.

In this vein, rapeseed oil is a promising raw material for the production of “green” BTX, including p-xylene, and C ₂ -C ₄ olefins, since

1) in rapeseed oil the oleic acid content reaches 60% [S.Z. Naji, ST. Thue, A. A. Abd. // State of the art of vegetable oil transformation into biofuels using catalytic cracking technology: Recent trends and future prospects];

2) rapeseed oil is the most produced in the Russian Federation. The production volume of rapeseed oil is about 800 thousand tons per year. (29 million tons per year in the world);

3) the production of BTX (including p-xylene) and C ₂ -C ₄ olefins from rapeseed oil corresponds to the concept of economic decarbonization, since the growth of biomass is achieved through the utilization of carbon dioxide.

Effective catalysts for the conversion of vegetable oils into BTX and olefins are high-silica zeolites, in particular, zeolites of the MFI structural type.

Thus, there is a known method for the hydroconversion of rapeseed oil to produce aromatic hydrocarbons (A.G. Dedov, A.S. Loktev, E.A. Isaeva, A.A. Karavaev, Yu.N. Kitashov, S.V. Markin, A. E. Baranchikov, V.K. Ivanov, I.I. Moiseev. Hydroconversion of rapeseed oil into hydrocarbons on micro-mesoporous materials MFI/MCM-41, synthesized by hydrothermal-microwave method. // Neftekhimiya, 2017, V. 57, No. 4 , pp.415-422). The process was carried out in a stream of hydrogen, at 500-600°C, atmospheric pressure, feed rate of raw materials 1-3.6 h ^-1 . On the MFI zeolite with a silica module of 40, the yield of xylenes did not exceed 15 wt.%, and on the MFI/MCM-41 composite - no more than 4 wt.%. It should be noted that the yields of p-xylene are not indicated, as are the other isomeric xylenes.

The closest to the claimed method (prototype) is the method of hydroconversion of rapeseed oil by contacting it in a reactor with MFI zeolite or micro-mesoporous composite MFI/MCM-41, obtained by hydrothermal-microwave synthesis, at a temperature of 496-600°C, atmospheric pressure with simultaneous feeding hydrogen into the reactor to produce a mixture of C ₂ -C ₄ olefins and a benzene-toluene-xylene fraction containing p-xylene (Isaeva, E.A. Production of hydrocarbons from renewable raw materials - fatty acid triglycerides - on zeolite catalysts of the MFI type: dissertation on Candidate of Chemical Sciences degree: 02.00.13, A.V. Topchiev Institute of Petrochemical Synthesis RAS, Moscow, 2017). When carrying out the hydroconversion of rapeseed oil in the presence of an unmodified catalyst of the MFI type structure at a temperature of 600°C, the yield of aromatic hydrocarbons was 29% wt, including benzene 7% wt, toluene 7% wt, xylenes 2% wt, C9+ aromatic hydrocarbons 13% wt, as stated on page 75 of the dissertation. The results of the conversion of rapeseed oil on the micro-mesoporous composite MFI/MCM-41 obtained by hydrothermal-microwave synthesis are presented in the same table. 34 on page 71, according to which at temperatures of 496 and 584°C the yield of the BTX fraction is 10% and 9% by weight, and the yield of xylenes is 4 and 3% by weight, respectively, at a feed rate per unit of catalyst equal to 1.8 g/ g cat. h. By increasing the feed rate of raw materials to 2.5 g/g cat. h. the yield of BTK fraction is reduced to 5%, the yield of xylenes is reduced to 2% wt.

The disadvantage of the known method is the low yield of the BTX fraction (5-10% wt), low yield of xylenes (2-4% wt). It is worth noting that the yield of p-xylene is not indicated and will be significantly lower than the total yield of xylenes. Another disadvantage is the high temperature of hydroconversion, which leads to high economic and energy costs.

Thus, it is relevant to develop a more effective method for hydroconversion of rapeseed oil from the point of view of obtaining p-xylene.

The objective of the present invention is to develop a more economical method for the hydroconversion of rapeseed oil, characterized by a high yield of the BTX fraction, a high yield of xylenes with high selectivity for p-xylene, as the most popular isomer among other isomeric xylenes.

The solution to the problem is achieved by the fact that in the method of hydroconversion of rapeseed oil by contacting it in a reactor with a catalyst - a micro-mesoporous composite obtained by hydrothermal-microwave synthesis, based on microporous MFI zeolite and a mesoporous second component at elevated temperature and atmospheric pressure while simultaneously feeding a hydrogen reactor to produce a mixture of C ₂ -C ₄ olefins and a benzene-toluene-xylene fraction containing p-xylene,

as a micro-mesoporous composite, a composite based on microporous zeolite and a mesoporous second component - silicon carbide - MFI/SiC is used, and the porous structure of the composite is characterized by a volume of micropores equal to 0.14-0.18 cm ³ /g and mesopores - 0.05- 0.07 cm ³ /g,

and the hydroconversion of rapeseed oil is carried out in a heated flow-type reactor, in which the catalyst is placed in its middle part, while the free volume of the reactor before and after the catalyst is filled with quartz chips, first the reactor with the catalyst placed in it is heated in a stream of hydrogen to a temperature of 430-470 ° C for an hour, and rapeseed oil is fed at a mass feed rate of 2.9-3.3 g/g cat. h.

During the conversion (hydroconversion) of rapeseed oil, the following reactions occur: deoxygenation of rapeseed oil with the formation of predominantly C ₁₆ -C ₁₈ hydrocarbons, cracking of C ₁₆ -C ₁₈ hydrocarbons with the formation of C ₂ -C ₄ olefins, cracking of C ₁₆ -C ₁₈ hydrocarbons followed by dehydrocyclization with the formation of aromatic hydrocarbons.

It is known to use as a catalyst for various processes of acid-base catalysis, in particular cracking, alkylation, isomerization, aromatization of alkanes and alcohols, a composite based on microporous zeolite and mesoporous silicon carbide - MFI/SiC, obtained by crystallization of a suspension consisting of tetraethylorthosilicate, water, tetrapropylammonium hydroxide, aluminum isopropoxide and silicon carbide in a molar ratio of tetraethylorthosilicate: water: tetrapropylammonium hydroxide: aluminum isopropoxide: silicon carbide equal to 1:35-39:0.11-0.16:0.013-0.015:0.5-0 ,7, under the influence of microwave radiation at a temperature of 190-200°C for 180-210 minutes with the formation of a crystallization product and sediment, separation of the latter, washing, drying and calcination to obtain the specified composite (see, RU 2725586 C1, cl. IPC S01B 39/04, S01B 39/38, S01B 33/26, B01J 29/40, B01J 29/89, B01J 29/70, B01J 20/32, B01J 20/18, B01J 27/224, B01J 35/04 , B01J 35/10, publ. 07/02/2020).

However, the use of the known composite in the production of olefins and BTC from rapeseed oil is unknown, where deoxygenation reactions (decarboxylation, decarbonylation and dehydration) of rapeseed oil occur with the formation of predominantly C ₁₆ -C ₁₈ hydrocarbons, which are then cracked to form C ₂ -C ₄ and olefins cracking followed by dehydrocyclization to form aromatic hydrocarbons.

The technical result that can be achieved using the proposed technical solution is:

- increasing the yield of the BTK fraction to 24% by weight;

- increasing the yield of xylenes to 9% by weight while increasing the selectivity for p-xylene among isomers to 76% by weight;

- reduction of the hydroconversion temperature to 430-470°C compared to 496-600°C in the prototype, which, as a consequence, reduces financial costs and simplifies the process as a whole;

- increasing the intensification of the process by increasing the feed rate of raw materials to 2.9-3.3 g/g cat. h.

The raw material used is unrefined rapeseed oil, which is produced at the Lebyazhsky vegetable oil plant. The fatty acid composition of rapeseed oil obtained from the Lebyazhy rapeseed oil plant is given in Table 2.

The catalyst used is obtained by hydrothermal-microwave synthesis, based on microporous MFI zeolite and mesoporous silicon carbide/SiC, similar to the method described in RF patent No. 2768153, class. IPC S07S 1/20, S07S 1/24, S07S 11/02, S07S 11/04, S07S 11/06, S07S 11/08, S07S 15/04, S07S 15/06, S07S 15/08, publ. 03.23.2022.

Prepare a mixture consisting of traethylorthosilicate, water, tetrapropylammonium hydroxide, aluminum isopropoxide and silicon carbide in the molar ratio tetraethylorthosilicate: water: tetrapropylammonium hydroxide: aluminum isopropoxide: silicon carbide equal to 1:35-39:0.11-0.16:0.013- 0.015:0.5-0.7 respectively. The resulting suspension is subjected to crystallization under the influence of microwave radiation at a temperature of 190-200°C for 180-210 minutes to form a crystallization product, after which the precipitate is separated from the crystallization product, which is washed, dried and calcined to obtain the target product.

The following are examples that illustrate the invention, but do not limit it.

Example 1

The catalyst is obtained according to the method described above. To do this, pour 59 ml of distilled water into a flat-bottomed flask with a magnetic stirrer. Then, with stirring, 0.26 g of aluminum isopropoxide, 11.3 ml of a 20% aqueous solution of tetrapropylammonium hydroxide, slowly - 19.8 ml of tetraethylorthosilicate and 2 g of silicon carbide are added. The molar ratio of the components in the mixture of tetraethylorthosilicate: water: tetrapropylammonium hydroxide: aluminum isopropoxide: silicon carbide is 1:37.1:0.127:0.014:0.562. Stirring is carried out until a homogeneous mixture is obtained.

Then this mixture is placed in a Teflon autoclave with a specified maximum pressure of 3.7 MPa and in a microwave installation Speed Wave Berghof - 4 (microwave power is 900 W, radiation frequency is 2.45 GHz) exposed to microwave radiation, providing a temperature of the reaction mass of 200 ° C, for 180 minutes.

The suspension formed in the autoclave is subjected to centrifugation in an ultracentrifuge at a rotation speed of 2000 rpm. Then the aliquot is drained, and the solid precipitate is washed at least 4 times with distilled water. After this, it is dried in a muffle furnace at a temperature of 190°C for 2 hours. In order to remove the template (organic structure-forming additives), the powder is calcined at 550°C for 6 hours to obtain the target product.

The resulting product is an MFI/SiC composite in proton form. The silica modulus of the MFI zeolite included in the catalyst is 136. The volume of micropores in the catalyst is 0.16 cm ³ /g, the volume of mesopores is 0.06 cm ³ /g.

The method of hydroconversion of rapeseed oil is carried out by contacting rapeseed oil with a catalyst placed in the middle part of a heated flow-type reactor, the free volume of which before and after the catalyst is filled with quartz chips, at a temperature of 450°C and a mass velocity of 3.1 g/g cat. h.

Contacting is carried out with additional supply of hydrogen to the reactor, the hydrogen supply rate is 3 l/h.

The fatty acid composition of rapeseed oil is given in Table 1.

The reaction products are analyzed by GLC.

The yield of BTK fraction is 24%, the yield of xylenes is 9%, the selectivity for p-xylene among isomers is 76%.

Example 2

The method of hydroconversion of rapeseed oil is carried out similarly to example 1 at a temperature of 470°C and a mass velocity of rapeseed oil of 3.3 g/g cat. h. Contacting is carried out with additional supply of hydrogen to the reactor, the hydrogen supply rate is 3 l/h.

Exposure to microwave radiation during catalyst preparation is carried out at a temperature of 190°C for 210 minutes.

The volume of micropores in the catalyst is 0.18 cm ³ /g, the volume of mesopores is 0.07 cm ³ /g.

The reaction products are analyzed by GLC.

The yield of BTK fraction is 20%, the yield of xylenes is 8%, the selectivity for p-xylene among isomers is 72%

Example 3

The method of hydroconversion of rapeseed oil is carried out similarly to example 1 at a temperature of 430°C and a mass rate of 2.9 g/g cat. h. Contacting is carried out with additional supply of hydrogen to the reactor, the hydrogen supply rate is 3 l/h.

Exposure to microwave radiation during catalyst preparation is carried out at a temperature of 190°C for 180 minutes.

The volume of micropores in the catalyst is 0.14 cm ³ /g, the volume of mesopores is 0.05 cm ³ /g.

The reaction products are analyzed by GLC.

The yield of BTK fraction is 22%, the yield of xylenes is 8%, the selectivity for p-xylene among isomers is 74%.

Example 4 (comparative)

The method for converting rapeseed oil is carried out similarly to example 1, but without supplying hydrogen to the reactor, at a temperature of 450°C. The reaction products are analyzed by GLC.

The yield of BTK fraction is 17%, the yield of xylenes is 7%, the selectivity for p-xylene among isomers is 56%.

Thus, carrying out the experiment without supplying hydrogen leads to a decrease in the selectivity for p-xylene and the yield of p-xylene.

This example shows that an increase in p-xylene selectivity and p-xylene yield is only achieved by using the MFI/SiC composite together and feeding hydrogen into the reactor under the required conditions.

The presence of a silicon carbide phase in the catalyst structure increases the thermal conductivity of the catalyst, and, as a result, can reduce the temperature gradient in the catalyst layer.

This also helps to increase the efficiency of this method of hydroconversion of rapeseed oil compared to the known method.

Carrying out the described method using a catalyst containing components for the synthesis of the catalyst in other concentrations and under other conditions within the stated range leads to similar results. The use of conditions and components in quantities beyond this range, as well as a catalyst with a different porous structure, does not lead to the desired results.

Thus, the described method makes it possible to increase the yield of the BTX fraction, the yield of xylenes, and the selectivity for p-xylene among isomers, due to the synergistic effect of the use of an MFI/SiC composite containing MFT zeolite and SiC specifically in the process of hydroconversion of rapeseed oil under the required conditions.

Claims (3)

A method for hydroconversion of rapeseed oil by contacting it in a reactor with a catalyst - a micromesoporous composite obtained by hydrothermal-microwave synthesis, based on microporous MFI zeolite and a mesoporous second component, at elevated temperature and atmospheric pressure while simultaneously feeding hydrogen into the reactor to obtain a mixture of C ₂ - olefins. C ₄ and benzene-toluene-xylene fraction containing p-xylene, characterized in that as a micromesoporous composite, a composite based on microporous zeolite and a mesoporous second component - silicon carbide - MFI/SiC is used, and the porous structure of the composite is characterized by a volume of micropores equal to 0.14-0.18 cm ³ /g, and mesopores - 0.05- 0.07 cm ³ /g, and the hydroconversion of rapeseed oil is carried out in a heated flow-type reactor, in which the catalyst is placed in its middle part, while the free volume of the reactor before and after the catalyst is filled with quartz chips, first the reactor with the catalyst placed in it is heated in a stream of hydrogen to a temperature of 430-470 ° C for an hour, then rapeseed oil is fed at a mass feed rate of 2.9-3.3 g/g cat. h.