RU2689416C1 - Method of hydroisalysing triglycerides of fatty acids in a mixture with oil fractions - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to a method for hydroforming preliminarily treated triglycerides of fatty acids (TFA) and straight-run diesel fraction at high temperature and pressure of hydrogen on sulphide catalysts MoS/AlOand NiMoS/AlOin two stages, at first of which hydrotreatment of straight-run diesel fraction is performed in presence of sulphide NiMoS/AlOcatalyst. Fatty acid triglycerides are pre-treated, including sequential re-esterification with methanol and isomerization to obtain methyl esters of fatty acids with a branched hydrocarbon residue, which at the second stage are mixed with a mixture of hydrocarbons, hydrogen and hydrogen sulphide obtained at the first stage and performing hydrodeoxygenation reaction in presence of sulphide catalyst MoS/AlO. Hydroskimming of the raw material is carried out at temperature 340 °C, hydrogen pressure of 4.0 MPa, volume flow rate of raw material is 1.1–1.25 h, total volume ratio hydrogen/raw material – 510–600 Nm/m.EFFECT: hydroskimming triglycerides of fatty acids and oil fractions to low-sulfur hydrocarbon fractions with lower pour point and limiting filterability temperature.1 cl, 4 ex, 1 tbl

Description

The invention relates to methods for co-hydrofining of fatty acid triglycerides and straight-run diesel fraction on sulfide catalysts in order to obtain low-sulfur hydrocarbon fractions.

In recent decades, one of the trends is the use of renewable resources for the production of environmentally friendly motor fuels, which is caused by a decrease in reserves and a deterioration in the quality of hydrocarbons and the need to reduce greenhouse gas emissions, mainly carbon dioxide. Hydrofining triglycerides of fatty acids (TFA) is one of the most promising approaches, as the result is a mixture of alkanes - a product that does not contain oxygen, is characterized by high cetane index and stability, is mixed with traditional diesel fuel in any proportions. This allows the use of existing infrastructure for its transportation and storage and does not require the adaptation of automobile engines. A wide range of non-edible vegetable oils (rapeseed, camelina, palm, etc.), waste edible oils, animal fats, tall oils, etc. can be used as raw materials. [J.K. Satyarthi, T. Chiranjeevi, D.T. Gokak, P.S. Viswanathan, An overview of vegetable oils / fats into the middle distillates, Catalysis Science & Technology, 3 (2013) 70-80; M. Al-Sabawi, J.W. Chen, Hydroprocessing of Biomass-Derived Chemicals: A Review, Energy & Fuels, 26 (2012) 5373-5399].

In industrial processes, traditional sulfide CoMo / Al ₂ O ₃ and NiMo / Al ₂ O ₃ hydrotreating catalysts are used to process triglycerides of fatty acids [D. Kubicka, V. Tukac, Hydrotreating of Triglyceride-Based Feedstocks in Refineries, Advances in Chemical Engineering, V. 42, 2013, Pages 141-194.]. The fatty acid triglycerides do not contain sulfur, therefore, to maintain the catalysts in the sulfide state, it is necessary to constantly add to the reaction mixture a sulfurizing agent, most often dimethyl disulfide [Kubicka, D., Horacek J., Deactivation of HDS catalysts in deoxygenation of vegetable oils // Applied Catalysis A 394 (2011) 9-17.].

Known methods of hydrofining TFA on sulfide catalysts in a mixture with petroleum distillates, as described in patents (EP 2428548, C10G 3/00, 03/14/12) and (US 9556387, C10G 49/04, 01/31/2017). When hydrofining of TFA in a mixture with oil fractions, hydrogen sulfide, which is obtained by desulfurization of crude oil, maintains the active component in the sulfide state. Combined processing of triglycerides in a mixture with oil fractions leads to an improvement in consumer properties of motor fuels: an increase in the cetane number, a decrease in density, nitrogen content and aromatic compounds.

It is well known that the reactions of hydrodeoxygenation of TFAs in the presence of traditional NiMo and CoMo catalysts proceed in two ways: by removing oxygen in the form of water or through splitting CO / CO ₂ molecules [Furimsky E., Hydroprocessing challenges in biofuels production // Catalysis Today, 217 ( 2013) 13-56]. This leads to a decrease in the yield of the liquid product, and the carbon oxides resulting from the reaction can be subjected to hydrogenation, which leads to an additional consumption of hydrogen. Removal of gases (carbon monoxide and methane) formed during the hydrodeoxygenation of triglycerides, requires additional costs for the introduction of technologies for purifying circulating hydrogen. Otherwise, the accumulation of methane and CO in the circulating gas will lead to a decrease in the partial pressure of hydrogen, the purity of which, as is well known, is one of the critical parameters for obtaining environmentally friendly motor fuels (<10 ppm of sulfur) from oil fractions [A. Stanislaus, A. Marafi, M.S. Rana. Ultra-low sulfur sulfuric diesel (ULSD) production. // Catalysis Today. - 2010. - V. 153. - P. 1-68].

It is known that the conversion of oxygen-containing compounds on the supported MoS ₂ / Al ₂ O ₃ catalyst proceeds along the route of direct hydrodeoxygenation with preservation of the number of carbon atoms, i.e. without the formation of carbon oxides [D. Kubicka, L. Kaluza, Deoxygenation of vegetable oils over sulfided catalysts, Mo and NiMo catalysts, Applied Catalysis A-General, 372 (2010) 199-208; IV Deliy, EN Vlasova, AL Nuzhdin, E.Yu. Gerasimov, GA Bukhtiyarova, Hydrodeoxygenation of Mo / Al ₂ O ₃ , CoMo / Al ₂ O ₃ and NiMo / Al ₂ O ₃ catalysts, RSC Adv., 4 (2014) 2242-2250]. Hydrodeoxygenation of TFA proceeds without the formation of carbon oxides in the presence of a MoS ₂ / Al ₂ O ₃ catalyst (US 8546626, B01J 21/02, 01.10.2013) or in the presence of a Ni-MoS ₂ / Al ₂ O ₃ catalyst with a controlled Ni / Mo ratio, in the range of 0-0.095, preferably in the range of 0-0.03 (US 8552235, SS07 1/24, 10/08/2013).

A method is described for hydrofining petroleum distillates together with TFA, designed to produce hydrocarbon fractions with a sulfur content of less than 10 ppm (mg / kg) using sulfide catalysts differing in the composition of the active component (US 2012/0216450, C10L 1/00, 08/30/2011). The method includes two stages: the first stage of hydrofining, in which a pre-prepared mixture of crude oil with TFA, together with hydrogen, passes through a catalyst that includes at least one element from group VI B (mainly Mo) and may include one element from group VIII (mainly Ni ) when the ratio of these elements is 0-0.095, on which selective, without the formation of carbon oxides, hydrodeoxygenation of TFA proceeds. In the second stage, the flow from the first stage passes through the NiMo / Al ₂ O ₃ hydrotreating catalyst (Ni / Mo-0.4), where the reactions of hydrodesulfurization, hydrodeazorization and hydrogenation of aromatic compounds take place. According to the invention, preferred for hydrofining is a mixture containing 70-99 wt. % petroleum distillates and 1-30 wt. % renewable raw materials, including animal and vegetable fats, as well as mixtures thereof; hydrodeoxygenation is recommended to be carried out at a temperature of 120-450 ° C (preferably 180-310 ° C), a pressure of 1-10 MPa (preferably 1-6 MPa), a space velocity of 0.1-10 h ^-1 (preferably 0.2-5 h ^-1 ), hydrogen / feedstock ratio 50-3000 Nm ³ / m ³ (preferably 150-1500 Nm ³ / m ³ ). Hydrotreating of the products obtained in the first stage is carried out in the presence of NiMo / Al ₂ O ₃ sulfide catalyst at a temperature of 250-450 ° C (preferably 300-400 ° C), a pressure of 0.5-30 MPa (preferably 1-25 MPa), space velocity of 0.1-20 h ^-1 (preferably 0.2-4 h ^-1 ), hydrogen / feed ratio 50-2000 Nm ³ / m ³ .

The disadvantage of the above method is the presence of a large amount of water in the hydrodeoxygenation products entering the hydrotreating stage, which can lead to irreversible deactivation and decrease the service life of the second stage catalysts as a result of prolonged contact with water vapor at elevated temperatures. In addition, hydrodeoxygenation of vegetable oils is accompanied by a significant consumption of hydrogen, which leads to a decrease in the partial pressure of hydrogen at the hydrotreating stage and a decrease in the activity of the NiMo / Al ₂ O ₃ catalyst in the hydrodesulfurization process. Another disadvantage of the proposed approach is the low Mo / Al ₂ O ₃ activity of the hydrodeoxygenation catalyst in the conversion reaction of sulfur compounds, especially at low temperatures of its operation, which can lead to a deficiency of hydrogen sulfide required to maintain the catalyst in the sulfide state, in the frontal layer of the hydrodeoxygenation catalyst to its gradual decontamination due to loss of sulfur. And, finally, during long-term operation, the frontal layer of the catalyst may gradually become contaminated with Ni and Fe compounds coming together with the raw material, which will lead to the formation of nickel and iron sulfides, which are active in decarbonylation and decarboxylation reactions, and increase the formation of carbon oxides.

The closest to the proposed technical solution is a patent (RU 2652991, C10L 1/00, 04.05.2018), which describes a method for hydrofining of petroleum distillates and TFA using layer-by-layer loading of catalysts and separate feeding of raw materials into the reactor (or reactors). Hydrogen and straight-run diesel fraction are fed to the first layer, where it is hydrotreated in the presence of a Ni-MoS ₂ / Al ₂ O ₃ sulfide catalyst prepared by any of the known methods; after that, the hydrotreated diesel fraction mixed with hydrogen and the resulting hydrogen sulfide enters the second layer (reactor) along with the flow of TFA, where selective hydrodeoxygenation of the plant raw material takes place in the presence of a MoS ₂ / Al ₂ O ₃ catalyst. With this approach, the hydrotreating catalyst is not exposed to water vapor and is operated under more favorable conditions (with a higher partial pressure of hydrogen and in the absence of water vapor). At the same time, hydrogen sulfide formed at the hydrotreating stage of the crude oil ensures that the MoS ₂ / Al ₂ O ₃ catalyst is maintained in the sulphide state. The proposed sequence of arrangement of the layers of hydrotreating catalysts and hydrodeoxygenation and the order of introduction of the raw material prevents the danger of increasing the selectivity of the conversion of TFA along the decarbonylation route in the presence of Ni, Fe sulfides accumulating in the frontal layer of the catalyst during its operation. The disadvantage of this method is to obtain a product with unsatisfactory low-temperature properties (pour point), since the products of the conversion of TFA when using this method are linear alkanes With ₁₆ -C ₂₂ (mainly C ₁₈ ). Poor low-temperature properties limit the use of the resulting hybrid fuel in regions with cold climates; to improve the low-temperature properties, it is necessary to additionally use the isomerization process of the obtained product.

The objective of this invention is to develop a more efficient method of hydrofining triglycerides of fatty acids in a mixture with petroleum fractions in low-sulfur hydrocarbon fractions.

The technical result - hydrofining triglycerides of fatty acids and petroleum fractions, namely, straight-run diesel fraction, in low-sulfur hydrocarbon fractions with lower pour point and limiting temperature filterability.

The problem is solved by the fact that raw materials based on TFA are pretreated, during which TFA is transformed into methyl esters of fatty acids with branched hydrocarbon residue; and then subjected to hydrofining using layer-by-layer loading of catalysts and separate feeding of raw materials into the reactor (or reactors). Hydrogen and straight-run diesel fraction are fed to the first layer, where it is hydrotreated in the presence of a Ni-MoS ₂ / Al ₂ O ₃ sulfide catalyst prepared by any of the known methods; after that, the hydrotreated diesel fraction in a mixture with hydrogen and the resulting hydrogen sulfide enters the second layer (reactor) containing the selective MoS ₂ / Al ₂ O ₃ catalyst, along with the flow of oxygen-containing feedstock, the ratio of the catalysts of the first and second layers may vary by 2 : 1-1: 2. Hydrofining of raw materials is carried out at a temperature of 340-380 ° C, a hydrogen pressure of 4.0-7.0 MPa, a flow rate of raw materials consumption of 1.0-1.5 h ^-1 , a total volume ratio of hydrogen / raw materials of 500-1000 Nm ³ / m ³ . Isomerization of unsaturated linear hydrocarbon residues in rapeseed oil or fatty acid esters in the presence of heterogeneous acid catalysts is a well-known process [DP Phan, E.Y. Lee, Catalytic Hydroisomerization Upgrading of Vegetable Oil-Based

Insulating Oil, Catalysts 8 (2018) 131; S.J. For example, it is possible to reagent. Reaume, N. Ellis, Bisciesel, Energies, 6 (2) 619-633]. The essence of the process lies in the fact that on the heterogeneous acid catalyst at the Bronsted acid sites, after the adsorption of the unsaturated hydrocarbon residue along the double bond, a carbocation is formed. Then there is a rearrangement of the molecule and the deprotonation of the branched carbocation with the formation of a branched hydrocarbon residue in the composition of the ether. The molecules of triglycerides of fatty acids are too large for the isomerization process, therefore the mixture of methyl esters obtained by transesterification of TFA in the composition of vegetable oils and animal fats is most often used as raw materials [RU 2394872, C10G 3/00, 20.07.2010]. At the hydrodeoxygenation stage, branched fatty acids in the ester composition are converted to branched hydrocarbons, which are characterized by a lower pour point than the corresponding linear alkanes.

A distinctive feature of the proposed method of hydrofining of TFA in a mixture with oil fractions is the use of a mixture of esters obtained by pretreatment of TFA and containing branched fatty acids as its oxygen-containing raw material.

Using the method described above for hydrofining of fatty acid triglycerides in a mixture with petroleum fractions will reduce the pour point of the resulting hybrid diesel fuel and avoid the need to carry out the process of isomerization of this product. In the proposed method, in contrast to the prototype, the products of the transformation of TFA are isoalkanes, whose pour point is 10-15 ° C lower compared with the corresponding n-alkanes.

In the prototype examples rapeseed oil was used as the oxygen-containing raw material. In the examples according to the invention, transesterification of rapeseed oil with methanol was carried out before use, followed by skeletal isomerization of the methyl esters obtained. The transesterification was carried out with the ratio of methanol: oil = 6: 1 at atmospheric pressure, a temperature of 60 ° C and in the presence of 0.6 wt. % NaOH (with respect to oil) as a catalyst. The excess methanol was removed on a rotary evaporator in vacuum at room temperature and the methyl esters of fatty acids from the catalyst were washed with an aqueous solution of 0.2 wt. % HCl, and then distilled water to neutral pH. Separation of the ether and aqueous phases was carried out on a separatory funnel. The resulting mixture of fatty acid methyl esters was dried for 12 hours at 40 ° C over zeolite pre-calcined at 400 ° C for 4 hours.

The isomerization reaction of fatty acid methyl esters was carried out in a stainless steel autoclave (“Autoclave Engineers”), USA) at a temperature of 260 ° C and a hydrogen pressure of 1.5 MPa in the presence of 4 wt.%. zeolite β (Angarsk Plant, Russia, characteristics: Si / Al = 25 ratio, specific surface area 580 m ² / g) for 6 hours at a stirring speed of 900 rpm. Next, the suspension of zeolite and fatty acid methyl esters was cooled to a temperature of 90 ° C, separated from the catalyst by centrifuging (CM-6M ELMI, Latvia) and placed in a cold, dry, dark place until analysis. Quantitative determination of specific compounds in the reaction mixture containing 10 wt. % fatty acid methyl esters in n-octane were performed using an Agilent 6890N chromatograph (Agilent Technologies), USA, equipped with a flame ionization detector and an HP-1MS quartz capillary chromatographic column (30 m × 0.32 mm × 1, 00 microns). The relative error in determining the content of the components of the reaction mixture by the chromatographic method does not exceed 0.5%. According to the results of gas chromatographic analysis, the isomerization selectivity of linear unsaturated fatty acid methyl esters was 85%.

- 134. Непромотированный катализатор Mo/Al₂O₃ готовили методом пропитки гранул алюмооксидного носителя водным раствором, содержащим рассчитанные количества оксида молибдена (VI), ортофосфорной Н₃РО₄ и лимонной кислоты С₆Н₈О₇×Н₂О. Для приготовления NiMo/Al₂O₃ катализатора в раствор предшественника активного компонента добавляли необходимое количество никеля (II) углекислого основного (водного) NiCO⋅Ni(OH)₂⋅Н₂О. Катализаторы использовали после сушки в потоке азота при комнатной температуре и в сушильном шкафу («Binder», Германия) при температуре (110±10)°С в течение 4-х ч. Содержание активных компонентов определяли после прокаливания в муфеле при температуре 550°С в течение 4-х ч, содержание активных компонентов в Mo/Al₂O₃ катализаторе составляет, мас. %: MoO₃ - 18,6; в NiMo/Al₂O₃, мас. %: MoO₃ - 18,1, NiO - 4,7.To illustrate the invention, sulfide hydrotreating catalysts (NiMo / Al ₂ O ₃ catalyst) and hydrodeoxygenation (MoS ₂ / Al ₂ O ₃ catalyst) described by the method prepared below were used. Granular alumina carrier was obtained by mixing powders of aluminum oxide and aluminum hydroxide, followed by molding through a laboratory syringe with a spinneret having a trefoil-shaped opening with a size of 1.2 ± 0.1 mm. The formed granules were dried at a temperature of (110 ± 10) ° C in a drying cabinet (Binder, Germany) for 12 hours. The dried carrier granules were calcined in a flow reactor in a stream of nitrogen at a temperature of (550 ± 10) ° С for 4- x h. The textural characteristics of the received carrier: S _beats , m ² / g - 235; pore volume, cm ³ / g - 0.79; average pore diameter

- 134. Non-promoted Mo / Al ₂ O ₃ catalyst was prepared by impregnating the granules of an alumina support with an aqueous solution containing calculated amounts of molybdenum oxide (VI), phosphoric H ₃ PO _4, and C ₆ H ₈ O ₇ × H ₂ O citric acid. For the preparation NiMo / Al ₂ O ₃ catalyst to the solution of the precursor of the active component was added the necessary amount of nickel (II) carbonate basic (water) NiCO⋅Ni (OH) ₂ ⋅H ₂ O. The catalysts were used after drying in a stream of nitrogen at room temperature and in a drying cabinet ("Binder", Germany) at a temperature (1 10 ± 10) ° C for 4 hours. The content of active components was determined after calcination in the muffle at a temperature of 550 ° C for 4 hours, the content of active components in the Mo / Al ₂ O ₃ catalyst is, wt. %: MoO ₃ - 18.6; NiMo / Al ₂ O ₃ , wt. %: MoO ₃ - 18.1, NiO - 4.7.

Hydrofining of straight-run diesel fraction with PM was performed on a 2-reactor pilot plant, the diameter of each reactor was 26 mm, and the length was 1300 mm. The raw materials were supplied using Gilson-305 liquid chromatographic pumps from tanks located on the scales, the consumption of raw materials was controlled by changing the mass. Hydrogen was dosed with automatic Bronkhorst dispensers, raw materials and hydrogen entered the reactor from top to bottom. Reactors are placed in tube furnaces with three independent heating zones, ensuring the presence of an isothermal zone in the central part of the reactor. Testing was performed using granules of trefoil catalysts with a diameter of 1.2 mm and a length of 4-6 mm. The required amount of catalyst granules (4–6 mm long) was loaded into the reactor, diluting it with fine particles of silicon carbide (fraction 0.1–0.25 mm) in a volume ratio of 1: 4. The first reactor was placed Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst (40 ml), and the second - MoS ₂ / Al ₂ O ₃ catalyst hydrodeoxygenation (20 mL). Straight-run diesel fraction together with hydrogen was fed to the first reactor, and oxygen-containing raw materials - to the second. Before conducting the experiments, sulfidation of catalysts with a straight-run diesel fraction (PDF), containing an additional 0.6 wt. % sulfur in the form of dimethyl disulfide (at a space velocity of 2 h ^-1 , the ratio of hydrogen / raw materials is 300, hydrogen pressure is 3.5 MPa) in several stages: at a temperature of 240 ° C for 8 h, at a temperature of 340 ° C for 6 h, the rate of increase in temperature between the stages was 25 ° C per hour. The tests of the catalysts were carried out under the conditions described in examples 1-4.

After the end of sulphidation, the catalyst was operated during the hydrotreatment of a straight-run diesel fraction for 3 days, after which the corresponding raw material was fed to the reactor. In the examples describing a method similar to the prototype, rapeseed oil was supplied to the second reactor in an amount that provides a proportion of PM / DF of 30/70. In the examples illustrating the invention, instead of rapeseed oil, a mixture was obtained that was obtained as a result of successive procedures for the transesterification of rapeseed oil to produce methyl esters and the skeletal isomerization of the methyl esters obtained.

The product of hydrofining a mixture of oil and oxygen-containing raw materials after the second reactor enters the separator, where the separation into liquid and gas phases occurs, the liquid phase is purged with nitrogen to remove the resulting hydrogen sulfide and ammonia. The resulting products are analyzed to determine the residual sulfur content, oxygen, density and pour point. The determination of trace amounts of sulfur is carried out using a sulfur analyzer ANTEK 9000NS sulfur / nitrogen in accordance with the methods of ASTM D 5762 and ASTM D 5453, respectively. The oxygen content was determined using a CHNSO Elemental Analyzer Vario EL Cube (Elementar Analysensysteme GmbH, Germany). Oxygenated compounds in hydrofining products were not detected within the sensitivity of the device. The low-temperature properties of the products obtained were characterized by the values of the pour point and the limiting filterability temperature. Determination of the pour point of the products was carried out on the apparatus TPZ-LAB-22, in accordance with the standard GOST 20287. The limiting filterability temperature was determined using an automatic device PTF-LAB-12 in accordance with GOST 22254-92 and ASTM D6371. Straight-run diesel fraction has the following characteristics: sulfur content - 1.03 wt. %, nitrogen content - 150 mg / kg, oxygen content - 680 mg / kg, density - 0.847 g / cm ³ . The total proportion of C ₁₈ acids (oleic, linoleic, linolenic and stearic) in the vegetable oil used in the work is 90.5 wt. %, oxygen content - 11.19 wt. % The selectivity of the reaction along the decarbonylation route, calculated from the analysis of carbon oxides in the gas phase as the ratio of the amount of carbon oxides formed to the theoretically possible amount, does not exceed 3% in all experiments.

The essence of the invention is illustrated by the following examples, reflecting the effect of pretreatment of TFA on the properties of the products of combined processing of oil and renewable raw materials.

Example 1 According to the prototype

In the example of the prior art two reactors connected in series, the first reactor was placed Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst (40 ml), and the second - MoS ₂ / Al ₂ O ₃ catalyst hydrodeoxygenation (20 ml); straight-run diesel fraction and hydrogen were fed to the first reactor, where hydrotreating reactions proceeded. The mixture of hydrocarbons, hydrogen and hydrogen sulfide formed from the first reactor was mixed with rapeseed oil before entering the second reactor. Raw materials were supplied in such an amount that the mass fraction of rapeseed oil in the raw material was 30 wt. %, and the volumetric rate is 1.1 h ^-1 . The ratio of hydrogen / raw materials, calculated on the total amount of diesel fraction and rapeseed oil, was 600 Nm ^{3 of} hydrogen / m ^{3 of} raw material, the hydrogen pressure was 4.0 MPa. To test the catalysts used straight-run diesel fraction and rapeseed oil.

Indicators of the process of hydrofining are shown in the table.

Example 2

In the example according to the invention, rapeseed oil was subjected to a treatment that included two stages: 1) - transesterification of rapeseed oil with methanol, 2) - isomerization of fatty acid methyl esters, and then subjected to hydrofining according to the method described in example 1.

The transesterification of rapeseed oil (Armaz, Russia, specification: refined, deodorized, GOST R 53457-2009) was carried out in a 500 ml conical flat-bottomed flask. To prepare the solution, 100 g of rapeseed oil, 20.62 g of methanol (JT Baker, Holland, specification: ultrapure for HPLC) and 6 g of NaOH (Reahim, Russia, specification: HCh, GOST 4328-77 ). The transesterification reaction was carried out at atmospheric pressure, a temperature of 60 ° C and a stirring speed of 100 rpm for 2 h. Then, to remove methanol, the mixture was placed in a round bottom flask of a rotary evaporator (“BUCHI”, Switzerland), in which x h in vacuum at room temperature was removed excess methanol. The washing of methyl esters of fatty acids from the catalyst was initially carried out with 50% by volume of an aqueous solution of 0.2 wt. % HCl, and then repeatedly distilled water to neutral pH. Separation of the ether and aqueous phases was carried out on a separatory funnel. The resulting mixture of fatty acid methyl esters was dried (Oven Binder, Germany) for 12 hours at 40 ° C above the zeolite, previously calcined at 400 ° C for 4 hours.

The isomerization of the prepared fatty acid methyl esters was carried out in a stainless steel autoclave (Autoclave Engineers, USA). 100 g of methyl esters of fatty acids and 4 g of zeolite β were loaded into an autoclave (Angarsk Plant, Russia, specific characteristics: Si / Al ratio = 25, specific surface area 580 m ² / g). Next, the reactor was purged with a stream of H ₂ for 10 minutes at a rate of 300 ml / min and the temperature was increased to 260 ° C and the hydrogen pressure to 1.5 MPa. The isomerization reaction was carried out for 6 hours at a stirring speed of 900 rpm. Next, the suspension of zeolite and fatty acid methyl esters was cooled to a temperature of 90 ° C and separated from the catalyst by centrifuging (CM-6M ELMI, Latvia) and placed in a cold, dry, dark place until analysis. Quantitative determination of specific compounds in the reaction mixture containing 10 wt. % fatty acid methyl esters in n-octane were performed using an Agilent 6890N chromatograph (Agilent Technologies, United States) equipped with a flame ionization detector and an HP-1MS quartz capillary chromatographic column (30 m × 0.32 mm × 1.00 um). The relative error in determining the content of the components of the reaction mixture by the chromatographic method does not exceed 0.5%. According to the results of gas chromatographic analysis, the isomerization selectivity of linear unsaturated fatty acid methyl esters was 85%.

The two reactors connected in series, the first reactor was placed Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst (40 ml), and the second - MoS ₂ / Al ₂ O ₃ catalyst hydrodeoxygenation (20 ml); straight-run diesel fraction and hydrogen were fed to the first reactor, where hydrotreating reactions proceeded. The mixture of hydrocarbons, hydrogen and hydrogen sulfide formed from the first reactor was mixed with the mixture of esters obtained as a result of sequential transesterification and isomerization of rapeseed oil, before entering the second reactor. Raw materials were supplied in such an amount that the mass fraction of oxygen-containing was 30 wt. %, and the volumetric rate of the raw material was equal to the volumetric rate used in the first example - 1.1 hour ^-1 . The ratio of hydrogen / raw materials, calculated on the total amount of diesel fraction and rapeseed oil, was 600 Nm ^{3 of} hydrogen / m ^{3 of} raw material, the hydrogen pressure was 4.0 MPa.

Indicators of the process of hydrofining are shown in the table.

Example 3

The method of example 2, characterized in that 20 ml of Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst was charged into the first reactor, and 40 ml of MoS ₂ / Al ₂ O ₃ hydrodeoxygenation catalyst was loaded into the second reactor; and hydrofining was carried out at a space velocity of 1.5 h ^-1 , hydrogen pressure — 7.0 MPa and hydrogen / raw materials ratio — 500 Nm ^{3 of} hydrogen / m ^{3 of} raw materials.

Indicators of the process of hydrofining are shown in the table.

Example 4

The method of example 3, characterized in that the hydrofining was carried out at a flow rate of 1.25 h ^-1 , a hydrogen pressure of 4.0 MPa and a hydrogen / feedstock ratio of 1000 Nm ^{3 of} hydrogen / m ^{3 of} raw materials.

Indicators of the hydrofining process are given in the table.

As can be seen from the presented examples, the use of a mixture of esters obtained by pretreatment of TFA and containing branched fatty acids in its composition allows obtaining hydrofining products with lower pour point and limiting filterability temperature, while the sulfur content in all examples does not exceed 10 mg / kg.

Thus, the proposed method allows to solve the problem of increasing the efficiency of the process of joint hydrofining of triglycerides of fatty acids and petroleum fractions into low-sulfur hydrocarbon fractions with lower pour point and limiting temperature of filterability.

Claims (2)

1. The method of hydrofining pretreated triglycerides of fatty acids (TFA) and straight-run diesel fraction at elevated temperature and hydrogen pressure on sulfide catalysts MoS ₂ / Al ₂ O ₃ and NiMoS ₂ / Al ₂ O ₃ in two stages, the first of which carry out hydrotreating Straight-run diesel fraction in the presence of sulfide NiMoS ₂ / Al ₂ O ₃ catalyst, characterized in that the fatty acid triglycerides are subjected to pretreatment, including sequential transesterification with methanol and isomerization to obtain methyl fatty acid ethers with branched hydrocarbon residue, which in the second stage are mixed with the mixture of hydrocarbons, hydrogen and hydrogen sulfide obtained in the first stage and carry out a hydrodeoxygenation reaction in the presence of a MoS ₂ / Al ₂ O ₃ sulphide catalyst. 2. The method according to p. 1, characterized in that the hydrotreatment of straight-run diesel fraction is carried out at a temperature of 340 ° C, a hydrogen pressure of 4.0 MPa, the flow rate of the raw material consumption is 1.1-1.25 h ^-1 , the total volume ratio of hydrogen / raw materials - 510-600 Nm ³ / m ³ .