RU2652986C1 - Catalyst and process for producing a fraction of aromatic and aliphatic hydrocarbons from vegetable oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to heterogeneously catalytic transformations of organic compounds, namely to catalytic conversion of renewable raw materials – vegetable oils into the alkane-aromatic fraction of hydrocarbons C₃-C₁₁₊, which can be used to produce components of motor fuels. Catalyst for preparation of aromatic and aliphatic hydrocarbons from a vegetable oil is provided, having the following composition, wt%: Pd – 0.1–0.8, Ag – 0.2–1.6, Al₂O₃ – 20–40, zeolite MFI (silicate module 30) – the rest, as well as a method for producing aromatic and alkane hydrocarbons from vegetable oils in the presence of said catalyst in a hydrogen atmosphere at a pressure of 10–50 atm at a temperature of 280–400 °C and a space velocity of 0.4 to 24 h^-1, in which raw materials are sunflower oil, rapeseed oil, peanut oil, corn oil, castor oil, oils produced by special algae cultures, such as: Scenedesmus dimorphus, Spirogyra sp., Euglena gracilis, Prymnesium parvum, Porphyridium cruentum, Botryococcus braunii.

EFFECT: increase of the yield of the target products, ensure their high purity from the content of heteroatoms, significantly increase the productivity of the catalyst for the sum of the target products, reduce methane formation, lower the process temperature.

3 cl, 1 dwg, 4 tbl, 16 ex

Description

Currently, an active search is underway in the development of processes for producing motor fuels based on promising types of vegetable oils [1]. Such great interest shown in the processing of vegetable oils is dictated by the need for rational consumption of combustible natural deposits and a decrease in dependence on oil resources, as well as an increase in the environmental acceptability of the processes for obtaining fuels and their consumption in transport [2-5]. In addition to various crops, special algae crops can be used to obtain oils of plant origin, many times superior in productivity to production, which allows you to save sown areas. The literature describes methods for converting vegetable oils into aromatic fractions of hydrocarbons in the presence of zeolite-containing catalysts in a hydrogen environment [6-9]. The main attention of researchers is aimed at obtaining first-generation biodiesel, which is a methylate or ethylate of fatty acids contained in vegetable oils. The transesterification process most effectively proceeds in the presence of homogeneous catalysts, which leads to high costs for the separation of the catalyst from the mixture of products and its disposal [1]. Another significant drawback of this area is the problem of the disposal of significant quantities of the concomitant product - glycerol with impurities of esterifying agents (methanol, ethanol). The problem of isolating glycerol, which does not contain impurities of esterifying alcohols, can be solved using a three-stage technology, according to which the first stage is the saponification of oils with the formation of flooded glycerol and salts of the corresponding fatty acids, after which the acids are converted to the H form and subjected to hydrogenation [10].

The main disadvantage of this approach is the multi-stage process as a whole. In this regard, the most rational method is the direct hydrogenation of triglycerides of fatty acids (HFA). Two approaches can be distinguished in this approach: the preparation of normal alkanes (predominantly C ₁₇ -C ₁₈ ) using catalysts based on broad-porous supports [11, 12] and the production of an alkane-aromatic hydrocarbon fraction containing predominantly alkyl substituted benzene and C ₄ -C branched alkanes ₆ [13, 14]. [13] described a method for processing rapeseed oil at temperatures of 550-650 ° C in the presence of Al ₂ O ₃ and Al ₂ O ₃ / B ₂ O ₃ catalysts into a fraction of olefins and aromatics in helium containing olefins up to C ₁₉ . [14] described a method for processing vegetable oils into an alkane-aromatic fraction at temperatures of 380–430 ° C in the presence of individual H-ZSM-5 and H-ZSM-5 modified with zirconium sulfide. The yield of the target fuel fraction reaches 28 wt. %, the yield of gaseous products up to 40 wt. %

A known method of producing liquid fuel hydrocarbons by catalytic conversion of vegetable oils in the presence of catalysts - high silica zeolites ZSM-5 and ZSM-12 [15]. The raw materials used are corn, peanut, castor, tall oil and jojoba oil, which, unlike the others related to triglycerides of fatty acids, is an ester of fatty acids and monohydric higher alcohols. When using the HZSM-5 catalyst (ZSM-5 zeolite in hydrogen form), a temperature of 400 ° C, a castor oil feed rate of 2.5 g / g catalyst per hour and an additional hydrogen supply of 5 ml / min, fuel hydrocarbons were obtained with a yield of 78%, including benzene-toluene-xylene fraction (mixture of benzene, toluene, ethylbenzene and xylenes) with a yield of 48%, aromatic hydrocarbons C ₉ -C ₁₃ with a yield of 25%. When using other oils, the yield of liquid fuel hydrocarbons and the performance of the catalyst were significantly worse.

The disadvantage of this method is the low productivity of the catalyst.

A known method of producing aromatic hydrocarbons With ₆ -C ₁₀ high-temperature contacting of hydrocarbon materials and / or oxygen-containing compounds with a catalyst containing a zeolite with a structure of ZSM-5 or ZSM-11, modified by elements or compounds of elements I, II, IV, V, VI, VII and VIII groups in an amount of 0.05-5.0 wt. %, at a temperature of 280-460 ° C. The raw materials can be contacted with the catalyst in the presence of a hydrogen-containing gas [16].

However, when using vegetable oils containing acid triglycerides as a feedstock, carrying out the process in the range of the above temperatures leads to a rather low yield of the target products with extremely low catalyst productivity in terms of total hydrocarbons (g / g of catalyst per hour). In addition, aromatic hydrocarbons obtained in this process are contaminated with by-products - liquid non-aromatic compounds, which at a contact temperature below 470 ° C consist mainly of a mixture of complex fatty acids. The specified mixture of fatty acids, on the one hand, prevents the selective release of aromatic hydrocarbons, on the other hand, is an unused waste, which leads to serious environmental problems and, as a result, the underestimated demand of the known method in the processing of vegetable oils.

A known method of producing aromatic hydrocarbons by high-temperature contacting vegetable oils containing acid triglycerides with a catalyst containing high-silica zeolite having a ZSM-5 structure and a promoter in the form of an oxide or mixtures of transition metal oxides selected from oxides of zinc, chromium, iron, at a temperature in the catalyst bed 470-630 ° C. The process is carried out in the presence of hydrogen. In this case, hydrogen is used at a feed rate of 50-200 ml / g (100-150 ml / g) of catalyst per minute. Hydrogen is fed into the reactor in which it reaches the catalyst, and the catalyst is heated to predetermined temperatures, after which vegetable oil is fed into the reactor at a rate of 2-7 g / g of catalyst per hour [17].

Also known is a method of processing vegetable oils in the presence of a catalytic composition, which is two types of zeolites (Y-form and ZSM-5), modified with rare earth oxides in an amount of at least 1 wt. % The process temperature is 480-600 ° C [18].

The main disadvantage of the methods [17-18] is the increased temperature of the process.

A known method of converting vegetable oils into aromatic compounds by contact with catalytically active forms of gallium for use in petrochemistry and / or for components of fuel mixtures or additives to them [19]. Renewable oils with a high oxygen content, high H / C molar ratio, containing higher fatty acids or their esters, are subjected to heating and contact with the catalyst. The catalyst may be a gallium-filled catalyst on one or more zeolite-alumina matrix with a pore size containing 10 oxygen atoms, such as ZSM-5, ZSM-11, ZSM-23, MCM-70, SSZ-44, SSZ-58, SSZ-35, and ZSM-22. The production of aromatic compounds from renewable oils increases with a larger gallium to cation ratio, the preferred ratio Ga / Al lattice is about 1. Various renewable oils or “bio oils” can be used, but algae oil provides an extremely high yield of benzene, toluene, ethylbenzene and xylenes (VTEX) during conversion over a gallium-cationic catalyst at a pressure of about 1 atm. and a temperature of about 400 ° C. The VTEX content is 77% of the liquid product, thus.

The disadvantages of this method are the high content of benzene in the reaction products, which are prohibited for use in gasoline fuels in amounts of more than 1%, and the rapid deactivation of the catalyst.

Thus, the creation of a catalyst having stability over a long period of time, high selectivity and activity is an object of the present invention.

A heterometallic precursor {PdAg ₂ (OOCMe) ₄ (HOOCMe) ₄ } _n for the synthesis of catalysts was prepared according to the following procedure: a suspension of Pd ₃ (OOCMe) ₆ (400 mg, 1.78 mmol by Pd) and AgOOCMe (400 mg, 2.4 mmol) in 35 ml of glacial acetic acid was stirred at 90 ° C for 2 hours in a light-protected flask. The reaction mixture was cooled to ~ 50 ° C and filtered from a dark gray precipitate of unreacted and partially decomposed silver acetate. The mother liquor was allowed to stand for 12 hours in a dark, then filtered dark yellow crystalline precipitate {PdAg ₂ (OOCMe) ₄ (HOOCMe) _{4} n} (1) (277 mg). A further portion of AgOOCMe (300 mg, 1.8 mmol) was added to the mother liquor and boiled for another 2 hours. After cooling and filtration, a second portion 1 (201 mg) was obtained. Heating the mother liquor with a third portion of AgOOCMe (200 mg, 1.2 mmol) allows you to get an additional 176 mg 1. Evaporation of the last mother liquor twice gives the last portion 1 (50 mg). Total yield 1,704 mg (50% by Pd). Complex 1 is soluble in AcOH and water, does not dissolve in C ₆ H ₆ and dissolves with rapid decomposition in CHCl ₃ , CH ₃ CN, acetone and THF, decomposes during storage for several months, even in the dark. Elemental analysis: found (%): S. 24.03; H 3.48. PdAg ₂ C ₁₆ O ₁₆ H ₂₈ Calculated (%): C 24.07; H 3.53. IR spectrum (ATR, cm ^-1 ): 1684s, 1603w, 1521vs, 1399vs, br, 1368w, 1374w, 1273s, 1016m, 946w, 890m, 696s, 673w, 619m. The structure of the heterometallic complex is shown in FIG. one

The zeolite used to prepare the catalyst is a domestic analogue of the MFI type zeolite with a molar ratio of SiO ₂ / Al ₂ O ₃ = 30 (manufactured by Angarsk Plant of Catalysts and Organic Synthesis OJSC, contains not more than 0.04 wt.% Sodium oxide. The hydrogen form of the zeolite was obtained by double cation exchange of Na + for ammonium ions in a 1N solution of ammonium nitrate, followed by drying and calcination for 4 hours at 500 ° C.

The zeolite-containing catalyst granules were obtained by mixing the MFI zeolite with a binder - an alumina suspension (containing 30 wt.% Dry Al ₂ O ₃ manufactured by Industrial Catalysts CJSC, Ryazan) and subsequent molding of the extrudate granules. Next, the extrudates were dried in air, then in an oven and calcined at 500 ° C for 4 hours.

A heterometallic precursor was applied by the method of residual impregnation onto finished extrudates of a zeolite with a binder. The extrudates were impregnated with a predetermined amount of a heterometallic precursor solution for two hours at room temperature. Then the solution was evaporated, the granules were dried at a temperature of 100-110 ° C for 3-4 hours and calcined in a muffle furnace at 500 ° C for 4 hours. The content of active components in the finished catalysts was, wt. %: Pd - 0.1-0.8, Ag - 0.2-1.6, Al ₂ O ₃ - 20-40, MFI zeolite (silicate module 30) - the rest.

The synthesis of the alkane-aromatic fraction is carried out in a flow reactor with the recirculation of gaseous products with a stationary catalyst bed, which is used as a Pd-Ag / MFI / Al2O3 catalyst. The reactor is heated by a toroidal electric furnace, which is located outside the tubular reactor. The height of the toroidal furnace corresponds to the height of the reactor. Upon completion of the heating of the catalyst, the feed of the starting vegetable oils to the catalyst is started, the amount of which in the reactor is 20 cm ³ , with a space velocity of 0.4-24 h ^-1 in flow mode. The liquid products after the reactor are collected in cooled receivers (the first along the way has a temperature of 0 ° C, the second is 15 ° C), the gaseous products are collected in a gas tank and their composition is analyzed by gas chromatography. Gaseous products are light C ₁ -C ₅ hydrocarbons, hydrogen, carbon monoxide and oxide. The qualitative and quantitative composition of gaseous products is determined by gas chromatography, by absolute calibration. The composition of liquid products is determined by gas-liquid chromatography and chromatography-mass spectrometry. The presence of residual mono and polyglycerides of fatty acids, as well as free acids in the reaction products was carried out by IR spectroscopy.

The processed vegetable oil is selected from the range of: sunflower oil, rapeseed oil, peanut oil, corn oil, castor oil, oils produced by special crops of algae, such as: Scenedesmus dimorphus, Spirogyra sp., Euglena gracilis, Prymnesium parvum, Porphyridiumocentium cruentium braunii.

The following examples illustrate the invention, but do not limit it. Examples 1-3. From the data of table 1 it is seen that the contacting of vegetable oil with catalysts containing 0.1 wt. % Pd, 0.2 wt. % Ag, 30 wt. % Al ₂ O ₃ , zeolite MFI-the rest; 0.4 wt. % Pd, 0.8 wt. % Ag, 30 wt. % Al ₂ O ₃ , zeolite MFI - the rest; 0.8 wt. % Pd, 1.6 wt. % Ag, 30 wt. % Al ₂ O ₃ , zeolite MFI - the rest, leads to a complete conversion of the starting oil. Water is formed in stoichiometric amounts; the yield of carbon oxides does not exceed 0.1 wt. %, which indicates a high selectivity of the hydrogenation reaction of the carboxyl group of triglycerides of fatty acids of vegetable oils. Hydrocarbon cracking reactions leading to the formation of methane and ethane are largely suppressed, because the yield of these products does not exceed 0.5 wt. % An increase in the amount of supported components in the catalyst leads to an increase in the yield of C ₃ -C ₆ aliphatic hydrocarbons and a proportional decrease in the yield of aromatic compounds. Application of active components in an amount exceeding 0.8 wt. % Pd and 1.6 Mac. % Ag, is impractical because significantly increases the cost of the catalyst in the absence of improvement in its properties. The application of active components in an amount less than 0.1 wt. % Pd and 0.2 wt. % Ag also does not seem relevant, because complicates the analysis and control of the preparation of the catalyst (the amount of active components corresponds to the amounts of impurities in alumina and zeolite, of which the catalyst consists).

Examples 4-7

Table 2 presents data on the dependence of the yield of the conversion products of vegetable oil on temperature. The optimal temperature range is the interval of 280-400 ° C, which provides a 100% conversion of vegetable oil and high performance in the target components (alkanes C ₃ -C ₆ , aromatic hydrocarbons C ₇ -C ₁₂ ). An increase in temperature to 450 ° C leads to an intensification of the processes of cracking of the hydrocarbon chains of the substrate, which leads to a sharp increase in the yield of undesired methane and ethane to 36.5 and 27.3 wt. %, respectively. In addition, the processes of decarbonylation / decarboxylation are intensified, which leads to an increase in the yield of carbon oxides to 6.8 wt. % and, as a consequence, the loss of valuable carbon mass of the feedstock. Lowering the temperature to 250 ° C leads to a sharp decrease in the conversion of the starting vegetable oil to 13.4%, which is extremely undesirable, because significantly complicates the stage of separation of products. As a result of the conversion of vegetable oil at 250 ° C, 4.7 wt. % olefins that need to be hydrogenated to be used as fuel components. The yield of aromatic compounds was 6.5 wt. %

Examples 8-11.

Table 3 presents data on the dependence of the yield of the products of the conversion of vegetable oil on the pressure of hydrogen. A hydrogen pressure of 10-50 atm is most suitable for the conversion of vegetable oils in the presence of the catalysts in question, because provides high selectivity for the target products and high stability of the catalyst. An increase in hydrogen pressure from 50 to 60 atm leads to an insignificant (by 0.3 wt.%) Decrease in the yield of aromatic hydrocarbons and a proportional increase in the yield of aliphatic hydrocarbons C ₃ -C ₆ . Those. an increase in pressure by 10 atm does not lead to visible changes in the operation of the catalyst and, accordingly, the use of increased pressure is not advisable. It should be noted that at a hydrogen pressure of 50 atm, C3-C6 olefins are completely absent in the reaction products, which can polymerize under the process conditions on the surface of the catalyst, thereby leading to its deactivation, therefore, from the standpoint of the stability of the catalyst, a pressure of 50 atm is justified. A decrease in hydrogen pressure to 5 atm leads to an intensification of decarbonylation / decarboxylation processes, which is expressed in an increase in the yield of carbon oxides to 3.2 wt. % and, as a consequence, the loss of carbon mass of the original oil. The yield of C ₃ -C ₆ olefins also increases to 8.1 wt. %, which, as described above, can adversely affect the duration of the catalytic system. Within the optimum values of hydrogen pressure of 10–50 atm, a change in pressure has little effect on the yield of reaction products.

Examples 12-16.

Table 4 presents data on the dependence of the yield of conversion products of vegetable oil on the value of the volumetric feed rate (VHSV). From the data table. 4 you can see that in the range of space velocities of 0.4-24 h ^-1 there is a 100% conversion of vegetable oil, the composition of the products remains almost constant. An increase in the volumetric feed rate of the reagent from 0.4 to 24 h ^-1 leads to an increase in the yield of aliphatic C ₃ -C ₆ hydrocarbons by 2.6 wt. % and reduce the yield of aromatic hydrocarbons With ₃ -C ₁₂ 3 wt. % It should be noted that even at a minimum feed rate of 0.4 h ^-1, the benzene yield did not exceed 0.8 wt. %, which allows the use of the resulting products as additives to gasoline fuel without any additional process steps. An increase in the space velocity to 30 h ⁻¹ leads to a sharp drop in the conversion of the starting oil to 27.9%. In addition, there is an increase in the yield of C ₃ -C ₆ olefins to 12.8 wt. %, which can lead to rapid carbonization of the catalyst surface. Reducing the feed rate of vegetable oil below 0.4 h ^-1 does not seem appropriate, because significantly reduces system performance. Thus, the optimal values of the feed rate of vegetable oil were found, lying in the range 0.4-24 h ^-1 , providing an exhaustive value for the conversion of raw materials and maximum yields of the target reaction products.

Information sources

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Claims (3)

1. The catalyst for the production of aromatic and aliphatic hydrocarbons from vegetable oil, having the following composition, wt. %: Pd - 0.1-0.8, Ag - 0.2 -1.6, Al ₂ O ₃ - 20-40, MFI zeolite (silicate module 30) - the rest. 2. The method of producing aromatic and aliphatic hydrocarbons by converting vegetable oil, characterized in that the conversion of vegetable oil is carried out in the presence of a heterogeneous catalyst according to claim 1, at a temperature of 280-400 ° C and a volumetric feed rate of vegetable oil of 0.4-24 h ^{- 1} in a hydrogen medium at a pressure of 10-50 atm. 3. The method according to p. 2, characterized in that the vegetable oil is selected from the series: sunflower oil, rapeseed oil, peanut oil, corn oil, castor oil, oils produced by special crops of algae, such as: Scenedesmus dimorphus, Spirogyra sp., Euglena gracilis, Prymnesium parvum, Porphyridium cruentum, Botryococcus braunii.

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