RU2592849C2 - Catalyst and method of producing aliphatic hydrocarbons from rapeseed oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical engineering, namely to method of producing alkanes and alkenes from renewable raw material, oils and fats of vegetable origin and more specifically relates to heterogeneous catalytic conversion of rapeseed oil to narrow fractions C₃ -C₁₉₊, which can be used for producing motor fuels and unsaturated monomers. Catalyst for producing aliphatic hydrocarbons from rapeseed oil contains Pt, Al₂O₃ and additionally Sn in following proportions, wt%: Pt - 0.1-1, Sn - 0.24-1.2, Al₂O₃ is rest. Method of converting rapeseed oil is carried out in presence of said heterogeneous catalyst at high temperature of 400-460 °C and rapeseed oil volume rate feed of 0.6-2.4 h^-1 in hydrogen medium at pressure of 40-50 atm. If necessary, catalyst is first treated with hydrogen at temperature of 100-500 °C before entry into contact with rapeseed oil.

EFFECT: higher selectivity of conversion of rapeseed oil into narrow alkane-olefin fractions C₃ -C₁₉₊, higher yield at high purity of produced fractions of aliphatic hydrocarbons and increased output of by-products while minimising number of process steps.

3 cl, 3 tbl, 18 ex

Description

The invention relates to the field of chemical technology, and in particular to a method for producing alkanes and olefins from renewable raw materials - oils and fats of plant origin, and more particularly relates to the field of heterogeneous-catalytic conversions of rapeseed oil into narrow fractions C ₃ -C ₄ and C ₁₈ , which can be used to produce motor fuels and unsaturated monomers.

As part of the development of alternative petroleum energy in the last decade, much attention has been paid to the analysis and development of effective approaches to obtaining important petrochemical products and fuel components based on renewable raw materials. The most important advantages expected during the implementation of this direction include the rational replacement of fossil natural deposits with renewable raw materials, an increase in the purity of final products, and a significant improvement in the ecology of technological production.

The most promising method for converting vegetable oils to fuel is direct hydrodeoxygenation of vegetable oils - a one-stage catalytic conversion of vegetable oil, leading to the formation of alkanes containing the same number of carbon atoms as the original fatty acid molecule (the so-called grindiesel). To date, grindiesel, obtained from vegetable oils by their deoxygenation, surpasses the first generation biodiesel, which is methyl esters of fatty acids, and diesel fuel, obtained from petroleum in basic fuel characteristics. Grindiesel has a high cetane number (75-90), has a low pour point and high oxidation stability [Wang H., Pham N.A., Rathbun W.E., Adams P.P. // Pat. W02013089871 A1. US 20130158890. 2013. UOP].

The main problem in the development of grindiesel technology is the limited availability of non-food sources of fatty acid triglycerides. As a result, the main requirements for the effectiveness of the technology of grindiesel are to achieve high selectivity in the reaction of hydrogenolysis of the carboxyl group, minimize carbon loss by decarboxylation (formation of carbon oxides) and cracking (formation of methane).

The processes for producing hydrocarbons with a high cetane number by hydrogenation of triglycerides are described in patents (US 5705722, C07C 1/00, 06/30/1994) and (EP 1396531, C07G 3/00, 09/06/2002). Cobalt-molybdenum or nickel-molybdenum-containing oxide catalysts supported on aluminum and silicon oxides are available. The processes are carried out at a pressure of 70-150 atm and a temperature of 370-450 ° C.

The disadvantage of the proposed methods is the high pressure of hydrogen and the solubility of Nickel and cobalt-containing catalysts in the products of hydrogenation of oils.

RF patent 2462445 describes a method for producing saturated hydrocarbons — components of diesel fuel from fatty acid esters — by reacting fatty acid triglycerides with hydrogen using a copper-containing catalyst. The method is characterized in that the catalyst is part of a PCM permeable composite material containing, in addition to catalytically active copper compounds, metallic copper as a reinforcing and heat-conducting component. The process is carried out at a temperature of 200-450 ° C and a pressure of 10-50 atm. Using this method provides a high degree of conversion of triglyceride of stearic acid TGSC with the formation of a mixture of saturated hydrocarbons with a boiling point in the region of 200-350 ° C (components of diesel fuel).

The disadvantages of the proposed method are the low yield (not more than 40 wt.%) Of fuel alkanes and a significant amount of heavy product - stearyl stearate.

Patent RU 2397199 C2 discloses a method for the selective production of hydrocarbons suitable for diesel fuel, which is characterized by a stage where the decarbonylation / decarboxylation reaction is carried out. The reaction is carried out by introducing a raw material obtained from renewable sources and containing C ₈ -C ₂₄ fatty acids, esters of C ₈ -C ₂₄ fatty acids, triglycerides of C ₈ -C ₂₄ fatty acids or metal salts of C ₈ -C ₂₄ fatty acids, and their combination, in the presence of solvents or without them, in contact with a catalyst containing from 0.5 to 20% of one or more metals of group VIII of the periodic system, for example platinum, palladium, iridium, ruthenium and rhodium, or from 2 to 55% nickel per carrier. The catalyst is treated with hydrogen at a temperature of 100-500 ° C before the reaction. The interaction of the feedstock with the catalyst is carried out at a temperature of 200-400 ° C and a pressure of from 0.1 to 15 MPa and hydrocarbons for diesel fuel are obtained, which can be subjected to isomerization.

The presented results according to the analogue are characterized by low efficiency (conversion, selectivity) of the proposed catalysts, as well as a high content of expensive active component (Pd) in them.

According to the method described in US Pat. No. 4,992,605, rapeseed oil is directly hydrogenated at high pressure of 8-15.2 MPa, at a temperature of 350-450 ° C and in the presence of catalysts containing nickel, cobalt and / or molybdenum. At high pressure, the carboxyl groups of fatty acid triglycerides (HFAs) undergo hydrogenation.

The disadvantages of this method include the additional consumption of hydrogen for hydrogenation of side reactions, its high pressure (more than 8 MPa), insufficiently high yield of fuel hydrocarbons.

Previously by the authors (M.V. Tsodikov, F.A. Yandieva, A.V. Chistyakov, M.A. Gubanov, Corresponding Member of the Russian Academy of Sciences A.E. Gekhman, Academician I.I. Moiseev "Direct High-Selective Conversion of Triglycerides of Fatty Acids in Components of Motor Fuels ”, REPORTS OF THE ACADEMY OF SCIENCES, 2012, Volume 447, No. 5, pp. 1-4), the possibility of direct catalytic conversion of rapeseed oil to the fraction of alkanes containing the same total amount or one less number of carbon atoms was demonstrated, which and a fatty acid fragment of the starting triglyceride. During this reaction, the carbon skeleton of the glycerol fragment or the carbon atoms of this group are partially converted to propane and partially embedded in one of the resulting alkanes. This condensation takes place in a hydrogen medium in the presence of a well-known industrial aluminum-platinum catalyst AP_64 (approximately 0.64 wt.% Pt on γ-Al2O3), which underwent a special treatment at the activation stage (with hydrogen at 450 ° C, then with ethanol for 40 h at 350 ° C under the conditions of reductive dehydration of the latter and finally again with hydrogen at 450 ° C. The degree of conversion of the starting oil is close to 100%. The yield of alkanes at 420 ° C and the volumetric feed rate of 0.6 h ^-1 is 90% by weight. alkanes and C ₁₇ C ₂₁ (43 wt.%). Gas shaped hydrocarbons C ₁ -C ₄ formed of 4.7 wt% and 47 wt% of alkanes C ₅ fractions -C ₁₆ Water Yield 6%, and high-molecular alkanes, C ₂₂₊ -... 0.3 wt% This catalyst.. and the method according to the totality of the features and the technical result are the closest to the declared and accepted by us as a prototype.

The disadvantages of the method include the additional consumption of hydrogen for the hydrogenation of side reactions, such as methanation and water-gas conversion reactions. The disadvantages of this method also include a high hydrogen pressure (more than 8 MPa) and a low yield of fuel hydrocarbons - 70-80 wt. %

The objective of the present invention is to increase the yields of the target narrow alkane-olefin fractions C3-C19 + with minimizing the loss of carbon mass on the formation of methane and carbon oxides.

To solve this problem, a catalyst for producing aliphatic hydrocarbons from rapeseed oil containing Pt and Al ₂ O ₃ , which additionally contains Sn at the following content of components, wt. %: Pt - 0.1-1, Sn - 0.24-1.2, Al ₂ O ₃ - the rest.

To solve this problem, a method for the conversion of rapeseed oil in the presence of the specified heterogeneous catalyst at an elevated temperature of 400-460 ° C and a space velocity of rapeseed oil of 0.6-2.4 h ^-1 in a hydrogen medium at a pressure of 40-50 atm is proposed.

If necessary, the catalyst is pre-treated with hydrogen at a temperature of 100-500 ° C before coming into contact with rapeseed oil.

Using the present method allows to increase the selectivity of the conversion of rapeseed oil into narrow C3-C19 + alkane-olefin fractions, to provide a high yield and high purity of the obtained fractions of aliphatic hydrocarbons, to reduce the yield of by-products and minimize the number of process steps.

The reagent used is rapeseed oil of CJSC Venevsky Creamery, which contains the following triglycerides of fatty acids (wt.%): Palmitoleic C ₁₅ H ₃₅ COOH (4.8 wt.%), Oleic C ₁₇ H ₃₃ COOH (93.3 wt.%), Gondoin C ₁₉ H ₃₇ COOH (1.8 wt.%), Eruca C ₂₁ H ₄₁ COOH (~ 0.1 wt.%).

The synthesis of aliphatic hydrocarbon fractions is carried out on a PID-Eng & Tech microcatalytic flow unit equipped with a reactor with a stationary catalyst layer (layer length 5 cm (d - 0.6 cm), spherical catalyst granules with a diameter of 2-3 mm), at a temperature of 400-480 ° C, a pressure of 50 atm (H ₂ ), the volumetric feed rate of rapeseed oil to the catalyst of 0.4-1.2 h ^-1 .

Heat treatment is carried out using 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 heat treatment of the catalyst, the temperature of the reactor is reduced to that required to obtain the alkane or alkane-olefin fraction, a pressure of 5 MPa (H ₂ ) is created, and the feed of the starting vegetable oil to the catalyst is started.

Liquid products after the reactor are collected in cooled receivers (the first along the way has a temperature of 0 ° C, the second - 15 ° C). The composition of liquid products is determined by gas-liquid chromatography and chromatography-mass spectrometry. Gaseous products are collected in a gas tank and analyze their composition by gas chromatography.

The invention is illustrated by the following examples.

Examples 1-5

In examples 1-5, the results of the conversion of rapeseed oil on a catalyst containing 0.4 wt. % Pt and 0.24 wt. % Sn, the rest is Al ₂ O ₃ (99.36 wt.%), With a volumetric feed rate of 1.2 h ^-1 , a hydrogen pressure (H ₂ ) of 5 MPa and various temperatures: 380, 400, 420, 460, 480 ° C.

The results of examples 1-5 are shown in table 1.

From the results of the experiments it follows that the temperature range of 400-460 ° C is optimal for the conversion of vegetable oil into fuel hydrocarbons. At this temperature, the highest yield of C ₃ -C ₁₉₊ alkanes is _achieved , equal to 95.5-96.1 wt. % With an increase in temperature to 480 ° C, intensification of cracking and decarboxylation / decarbonylation processes is observed, which leads to an increase in the yield of carbon oxides and methane-ethane fraction to 10.5 and 18.7 wt. % respectively.

An increase in the yield of undesired C1-C2 products reduces the efficiency of the process by increasing the loss of valuable carbon mass of the feedstock.

When the temperature drops to 380 ° C, a sharp drop in the degree of conversion of the starting oil from 100 to 10% is observed, while the selectivity of the formation of the target products has the same value as at optimal temperatures of 400-420 ° C.

A study of the conversion of rapeseed oil in the presence of catalysts of various compositions showed that the Al ₂ O ₃ support was not active in the described process, the oil conversion was 12 wt. % (Example 6). Monometallic catalyst containing 1.2 wt. Sn, the rest of Al ₂ O ₃ , exhibits strong cracking activity, which leads to a significant increase in the yield of the undesired methane-ethane fraction to 33.7 wt. % (Example 7). Example 8 shows that in the presence of a monometallic catalyst, 0.4 wt. % Pt, the rest is Al ₂ O ₃ , rapeseed oil with 100% conversion is converted to the C3-C19 + alkane fraction, the yield of which reaches 94.7 wt. % A disadvantage of the aluminoplatinum system is the high degree of decarboxylation of the feedstock, i.e. the yield of alkane C18 is 14.9 wt. %, and in the feedstock the content of oleic acid C18 is 94 wt. %, which indicates the loss of valuable carbon mass. Of the bimetallic systems, the most active and selective are catalysts containing Pt - 0.1-1, Sn - 0.24-1.2, Al ₂ O ₃ - the rest (examples 2, 9-13), providing the yield of target hydrocarbons C3- C19 + 95-99.9 wt. % It should be noted that in the presence of catalysts containing Pt - 0.1-1, Sn - 0.72-1.2, Al ₂ O _{3 the} rest, not only alkanes are formed, but also olefins, the yield of which reaches 25 wt. % (examples 9-13). Among the obtained olefins contains from 5 to 8 wt. % linear alpha olefins, which are a valuable product for various petrochemical products.

As can be seen from the table. 2, an increase in the platinum content in the catalyst above 1% wt. leads to a sharp decrease in the yield of target fractions.

In order to optimize the process, experiments were conducted on the influence of the volumetric feed rate on the process productivity values (examples 15-18).

It was found that in the range of volumetric feed rates of 0.6-2.4 h ^-1 there is a maximum system performance for the target products in excess of 99 wt. % With an increase in space velocity to 4.8 h ⁻¹ , a decrease in the conversion of the starting oil to 70% is observed with a selectivity of the process equivalent to Examples 16, 17.

The listed parameters allow converting vegetable oil into a fraction of fuel hydrocarbons in one step with a yield exceeding 99 wt. % The resulting products contain olefins, including linear alpha olefins that can be used as raw materials for a wide range of petrochemical processes.

Thus, in the proposed method, the optimal composition of the bicomponent catalyst and the process conditions were found under which almost the entire carbon mass of rapeseed oil is converted into alkane-olefin hydrocarbons of fractions C3-C19 +, usually with the predominant formation of two fractions C ₁₈ and C _{3 + 4} . Such an unusual selective conversion of fatty acid triglycerides (HFA) of rapeseed oil can occur when oxygen from the feedstock is used to form water. The observed lipid conversion is realized in the presence of a catalyst with a molar ratio of active components of Sn / Pt - 5. It can be assumed that, with the found ratio of active components, the cracking activity of platinum-containing centers is significantly reduced, while the activity in the recovery of oxygen-containing fragments of triglycerides of fatty acids that are converted into alkane-olefinic hydrocarbons.

Claims (3)

1. The catalyst for the production of aliphatic hydrocarbons from rapeseed oil containing Pt and Al ₂ O ₃ , characterized in that it additionally contains Sn at the following content of components, wt. %: Pt - 0.1-1, Sn - 0.24-1.2, Al ₂ O ₃ - the rest. 2. The method of converting rapeseed oil in the presence of a heterogeneous catalyst at elevated temperature, characterized in that the conversion of rapeseed oil is carried out in the presence of a catalyst according to claim 1 at a temperature of 400-460 ° C and a feed rate of rapeseed oil of 0.6-2.4 hours ^-1 in a hydrogen medium at a pressure of 40-50 atm. 3. The method according to p. 2, characterized in that the catalyst is pre-treated with hydrogen at a temperature of 100-500 ° C before coming into contact with rapeseed oil.