RU2204546C1 - Process of production of hydrocarbons from carbon oxides and hydrogen - Google Patents

Abstract

FIELD: petrochemical processes. SUBSTANCE: synthesis gas is brought into contact with catalytic composition consisting of mixture composed of (i) iron-containing Fischer-Tropsch synthesis catalyst in oxidized or reduced form promoted by aluminum, silicon, magnesium, potassium, and calcium oxides, and (ii) acid component: crystalline aluminosilicate or silicoaluminophosphate. Process employs circulation of gas flow after reaction with volume ratio of amount of circulating gas to amount of initial synthesis gas is equal to 1-1000. Process is carried out at 220-400 C, pressure 10-100 atm, synthesis gas volume flow rate 100-5000 h^-1, molar ratio H₂/CO in initial synthesis gas 1-3, and volume content of CO₂ in gas flow at the inlet of reactor between 0.01 and 40%. EFFECT: increased selectivity and productivity of catalyst regarding liquid hydrocarbons. 7 cl, 1 tbl, 16 ex

Description

The invention relates to organic chemistry, namely to petrochemistry and, in particular, to a method for producing hydrocarbons from a mixture of CO, H ₂ and CO ₂ (hereinafter referred to as synthesis gas). As a catalyst, compositions of iron-containing Fischer-Tropsch synthesis catalysts with acidic components — crystalline aluminosilicates (zeolites) or silicoaluminophosphates of various structures — are used. The resulting hydrocarbon fractions can be used for practical purposes as gasoline and diesel fuel with a low content of benzene and aromatic hydrocarbons and, accordingly, a high content of aliphatic hydrocarbons from the structure, as well as raw materials for the production of basic components of motor oils.

A known method of producing C ₅₊ hydrocarbons from a gas containing H ₂ and CO by contacting the gas at a temperature of 180-250 ^o C, a pressure of 15-50 atmospheres and a volumetric ratio of H ₂ / CO equal to 1.1-1.8, s a catalyst containing cobalt and zirconium on a support selected from aluminosilicate or oxides of silicon, aluminum, titanium (RF patent 1833355, CL 07 07/104, 1993, [1]).

Another known method for producing a cobalt-zirconia catalyst on Al ₂ O for the synthesis _of C _{5 +} hydrocarbons from a gas containing H ₂ and CO, applied at a temperature of 150-350 ^o C and a pressure of 10-70 atmospheres and a volume ratio H ₂ / CO equal to 1.0-2.3 (RF patent 1836146, class B 01 J 37/04, 21/04, 23/74, 1993, [2]).

According to these methods, as a result of the conversion of a mixture of H ₂ and CO on cobalt-zirconium catalysts, C ₅₊ hydrocarbons are obtained with high selectivity from 68-85 wt.% [1] to 87-91 wt.% [2] and a productivity of 100-108 g / l cat / h The main disadvantages of the methods are the high cost of the catalyst and the low content of iso-paraffins in the reaction products.

Closest to the invention in its technical essence is a method of producing hydrocarbons from synthesis gas with a molar ratio of H ₂ / CO = 1.6, diluted with nitrogen to 50 vol.%, When it is contacted at a pressure of 30 atm and temperatures of 230-320 ^o C with binary catalytic systems based on Fischer-Tropsch synthesis catalysts (SFT) and ZSM-5 type zeolite (L. Vytnova, G. A. Kliger, E.I. Bogolepova et al., Neftekhimiya, 2001, v. 41, 3, pp. 201-208, [3]).

According to the prototype, the liquid products of the synthesis gas conversion are the gasoline fraction (C ₅ -C ₁₀ hydrocarbons), the diesel fraction (C ₁₀ -C ₂₀ hydrocarbons), C ₂₁₊ solid paraffins and reaction water containing oxygen-containing compounds. In this work (prototype) there are a number of significant drawbacks:
1) high methane formation from 17 to 40 wt.% Of the amount of hydrocarbons;
2) low selectivity and productivity of the catalyst for liquid (C ₅₊ ) hydrocarbons 37-50 wt.% And 34-98 g / l cat. / H, respectively;
3) low yield of liquid hydrocarbons to the supplied synthesis gas not exceeding 70 g / nm ³ CO + H ₂ ;
4) a small degree of useful use of the "carbon" of the initial synthesis gas, i.e., the amount of the transferred "carbon" CO to the "carbon" of liquid hydrocarbons is not more than 30 wt.% (The remaining 70 wt.% Of the "carbon" remain in unconverted СО, formed by-products in gaseous hydrocarbons and alcohols, and also pass into СО ₂ , which is a product harmful to the atmosphere):
5) low content of aromatic hydrocarbons in C ₅₊ hydrocarbons, not exceeding 5 wt%;
6) a high residual content of oxygen-containing compounds in the reaction water up to 7 wt.%.

 The present invention is to increase the selectivity and productivity of the catalyst for liquid hydrocarbons.

The problem is solved in that for the catalytic conversion of synthesis gas to hydrocarbon products, a mixture of an iron-containing Fischer-Tropsch synthesis catalyst in an oxidized or reduced form, promoted by oxides of aluminum, silicon, alkaline or alkaline earth metals, and an acid component of the type crystalline aluminosilicate ZSM-5, β or silicoaluminophosphate type SAPO-5, apply the circulation of the gas stream after the reactor with a volume ratio of the amount of circulating gas to is one synthesis gas equal to 1-1000, and the process is carried out at a pressure of 10-100 atm and a temperature of 220-400 ^o C, the volumetric feed rate of raw syngas 100-5000 h ^-1, molar ratio H ₂ / CO in the initial synthesis -gas equal to 1-3, and the volumetric content of CO ₂ in the gas stream at the inlet of the reactor is 0.01-40%.

Distinctive features of the invention are:
a) for the catalytic conversion of synthesis gas to hydrocarbon products, mixtures of iron-containing Fischer-Tropsch synthesis catalysts in oxidized or reduced form, promoted with oxides of aluminum, silicon, alkali or alkaline earth metals, with acid components - crystalline aluminosilicates of the ZSM-5 type, are used as catalysts β or silicoaluminophosphates of the SAPO-5 type in a weight ratio of iron-containing catalyst / acid component equal to 10-90 / 90-10;
b) in the process, circulation of the gas stream after the reactor is used with a volume ratio of the amount of circulating gas to the initial synthesis gas equal to 1-1000;
c) the process is carried out at a pressure of 10-100 atm, a temperature of 220-400 ^o C, a volumetric feed rate of the feed synthesis gas of 100-5000 h ^-1 , a molar ratio of H ₂ / CO in the feed synthesis gas of 1-3, and the volumetric content of CO ₂ in the gas stream at the inlet of the reactor is 0.01-40%;
g) the recovery of the Fischer-Tropsch synthesis catalyst is carried out in two versions - either as part of the catalyst composition with synthesis gas at a temperature of 220-400 ^o C, a pressure of 10-100 atm and a volumetric feed rate of synthesis gas of 100-5000 h ^-1 , or mixing with the acid component in a separate reactor at a temperature of 400-500 ^o C, a pressure of 50-100 atm and a space velocity of a circulating hydrogen-containing gas of 2000-30000 h ^-1 .

The choice of catalyst for the conversion of synthesis gas to hydrocarbon products is based on the fact that of all the Fischer-Tropsch synthesis catalysts, the most productive in the temperature range 220-400 ^o C are fused iron catalysts. The combination of fused iron catalysts with acidic components leads to intensification of the synthesis of hydrocarbons from H ₂ , CO, and CO ₂ due to faster reactions of conversion of intermediate products of Fischer-Tropsch synthesis (alcohols, olefins) on the acid component to the target hydrocarbon products. Fused iron catalysts (designated as ПЖК-1, 2, 3) differ from each other by the preparation method, the amount and composition of modifying additives. The acidic components of the catalyst composition differ from each other by the type of crystal structure and acidic characteristics, depending on the molar ratio of SiO ₂ / AlO ₃ in the acid component. The ratio between the PUFA and the acid component affects the selectivity and performance of the catalyst composition for liquid hydrocarbons.

The choice of conditions for the process of synthesis of gasoline and diesel fractions from a gas containing H ₂ , CO and CO ₂ is due to the following factors. Increased pressure is necessary for deeper conversion of synthesis gas. The lower limit of the temperature range (220 ^o C) is determined by the minimum activity of the catalyst, exceeding the upper limit of the temperature (400 ^o C) leads to rapid carbonization of the catalyst surface. The volumetric feed rate of the feed synthesis gas is determined by the activity of the catalyst used at a fixed pressure and temperature. The claimed value of the space velocity is the most optimal for gasoline and diesel fractions. The ratio between H ₂ and CO, as well as between CO and CO _2, is determined by the stoichiometry of chemical reactions of hydrocarbon synthesis. For example, for the formation of the “CH ₂ ” group of paraffin hydrocarbons per carbon atom, two hydrogen atoms are required, and the amount of bound “O” in the feedstock determines the hydrogen consumption during the formation of H ₂ O molecules. Based on theoretical assumptions, the experiments were carried out under conditions sufficient close to the stoichiometric ratio between "C", "O" and "H". The process of reducing the iron component of the catalyst is necessary for the formation of catalytic centers active in the synthesis of hydrocarbons from carbon oxides and hydrogen. Recovery conditions are determined experimentally. The found reduction conditions make it possible to achieve the performance of the hydrocarbon synthesis process given below.

An important role in achieving high selectivity and productivity of the catalytic composition for C ₅₊ hydrocarbons belongs to the circulation of the gas stream after separation of liquid products. Firstly, the constant removal of water and liquid hydrocarbons from the contacting gas prevents the poisoning of the surface of the iron catalyst with water vapor, significantly suppresses the formation of carbon dioxide, which is inactive in the Fischer-Tropsch reaction, and reduces the rate of cracking reactions of the resulting C ₅₊ hydrocarbons on the acid component. Secondly, during recycling, light olefins and oxygen-containing intermediate products (for example, dimethyl ether) are repeatedly contacted with the catalyst, turning into target products. Thirdly, the high linear velocities of the circulating gas flow in combination with the constant entrainment of excess heat from the catalysis zone have a positive effect on the temperature distribution in the reactor, and improve the processes of heat transfer and mass transfer.

Example 1 (prototype). Fractions of a fused iron catalyst containing about 5% promoters, previously reduced with hydrogen and granular synthetic zeolite type ZSM-5, are mixed in a mass ratio of 56 to 44 and loaded into a flow reactor. The experiment is carried out at a pressure of 30 atmospheres, a temperature of 280 ^o C and a volumetric flow rate of synthesis gas 2930 h ^-1 . The composition of the source, exhaust gases and liquid synthesis products was determined chromatographically. The conditions and main indicators of experience are shown in the table.

 The industrial applicability of the invention is illustrated in examples 2-16.

Example 2. In the reactor load 30 cm ³ fractions of 0.25-0.5 mm of fused iron catalyst ПЖК-1 and granular (30 wt.% Al ₂ О ₃ ) zeolite type ZSM-5 in a mass ratio of 50/50. The initial synthesis gas is fed into the reactor block for mixing with the gas circulating in the block. The reactor block consists of a heated reactor, a condenser refrigerator, high and low pressure separators, an intermediate collector of liquid products and an electromagnetic pump for gas circulation. Before synthesis, the catalyst is subjected to synthesis gas reduction under the following conditions: pressure 10 atm, temperature 350 ^o C, duration 24 hours; then the pressure rises to 30 atm and the restoration is continued at a temperature of 350 ^o C, the duration is 8 hours. After restoration, the catalyst is developed at a temperature of 300 ^o C for 20 hours. The process of hydrocarbon synthesis is carried out at a pressure of 30 atm and at a temperature in the catalyst layer of 300 ^o C. To prevent the accumulation of non-condensable products in the reactor block, a portion of the circulating gas is constantly discharged from the block after the high-pressure separator. Liquid products (condensed hydrocarbons, water fraction), gas discharged from the reactor block and gaseous hydrocarbons released during throttling are analyzed separately by gas chromatography. The conditions and main indicators of experience are shown in the table.

 Example 3. Similar to example 2. The conditions and basic indicators of experience are shown in the table.

Example 4. Similar to example 2. It is characterized in that the fused iron catalyst PZhK-2 is used as the SFT catalyst and the reduction is carried out with synthesis gas at a pressure of 30 atm, a temperature of 350 ^o C for 16 hours. The conditions and basic experimental parameters are shown in table.

Example 5 Similar to example 2. It is characterized in that the fused iron catalyst ПЖК-3 is used as the SFT catalyst, and the reduction is carried out with a hydrogen-containing gas in a separate reactor until it is mixed with the acid component at a pressure of 100 atm, a temperature of 400-500 ^o С and the space velocity hydrogen-containing gas 30,000 h ^-1 . It differs in that in the catalytic composition, the mass ratio of PZhK-Z / ZSM-5 is 33/67. The conditions and main indicators of experience are shown in the table.

 Examples 6-8. Similar to example 5. The conditions and basic indicators of the experiments are shown in the table.

 Example 9. Similar to example 5. It is characterized in that in the catalytic composition the mass ratio of PZhK-3 / ZSM-5 is 25/75. The conditions and main indicators of experience are shown in the table.

 Example 10. Similar to example 5. It is characterized in that in the catalytic composition the mass ratio of PZhK-3 / ZSM-5 is 15/85. The conditions and main indicators of experience are shown in the table.

Examples 11-12. Analogous to Example 5. characterized in that as the acid component used pelleted (30 wt.% Al ₂ O _z) type zeolite β (SiO ₂ / Al ₂ O ₃ = 75). and the mass ratio of PZhK-3 / β is 40/60. The conditions and main indicators of the experiments are shown in the table.

 Example 13. Similar to examples 10-11. It differs in that in the catalytic composition, the mass ratio of PUFA-3 / β is 70/30. The conditions and main indicators of experience are shown in the table.

Example 14. Similar to example 2. It is characterized in that the PZhK-1 catalyst is subjected to synthesis gas reduction under the following conditions: pressure 30 atm, temperature 260 ^o С, duration 10 h; then the temperature rises to 280 ^o С and the restoration is continued at this temperature for 4 hours. After restoration, the catalyst is developed at a temperature of 300 ^o С for 20 hours. It is also characterized in that granular (30 wt.% Al ₂ O is used as an acid component) _h ) silicoaluminophosphate type SAPO-5, and the mass ratio of ПЖК-3 / SАРО-5 is 30/70. The conditions and main indicators of experience are shown in the table.

Examples 15-16. Analogous to Example 5. characterized in that the reactor was charged with 20 cm ³ fractions 0.25-0.5 mm fused iron catalyst VLS-3 and 130 cm ³ of granulated (30 wt.% Al ₂ O _z) type zeolite β (SiO ₂ / Al ₂ O ₃ = 75) in the form of granules of size 3 • 4 mm. They also differ in that in the catalytic composition, the mass ratio of PUFA-3 / β is 45/55. The conditions and main indicators of the experiments are shown in the table.

As can be seen from the results presented in the table, the proposed method allows to obtain liquid (C ₅₊ ) hydrocarbons and has advantages over the prototype:
1) the yield of liquid hydrocarbons, based on the initial synthesis gas, is 1.5-2.6 times higher;
2) the selectivity for the formation of C ₅₊ hydrocarbons is 1.4-1.7 times higher;
3) methane formation is reduced by 1.6-4.1 times;
4) the performance of the catalyst composition in liquid hydrocarbons is 1.1-2.0 times higher;
5) the performance of a unit volume of iron-containing catalyst (PZhK) significantly exceed similar indicators calculated according to the experimental data of the prototype;
6) in all the examples of the proposed method, the degree of useful use of "carbon" synthesis gas is more than 2 times higher than that shown in the prototype:
7) the content of aromatic hydrocarbons in C ₅₊ hydrocarbons by the proposed method is significantly higher than in the prototype, which has a positive effect on the octane numbers of gasoline fractions extracted from liquid hydrocarbons

Claims (7)

1. A method of producing hydrocarbons from carbon oxides and hydrogen, comprising contacting the synthesis gas with a catalytic composition consisting of a mixture of an iron-containing Fischer-Tropsch synthesis catalyst and an acid component at elevated pressure and temperature and given recovery conditions of the iron-containing active component of the catalytic composition, characterized in that crystalline aluminosilicate or silicoaluminophosphate is used as the acid component, circulation of the gas stream after p actor by volume the amount of circulating gas to the starting synthesis gas equal to 1-1000, and the process is carried out at a pressure of 10-100 atm and a temperature of 220-400 ^o C, the volumetric feed rate of raw syngas 100-5000 h ^-1, molar the ratio of H ₂ / CO in the original sytse gas equal to 1-3, and the volumetric content of CO ₂ in the gas stream at the inlet to the reactor is 0.01-40%.  2. The method of producing hydrocarbons according to claim 1, characterized in that iron fused catalysts in oxidized or reduced form, promoted by oxides of aluminum, silicon, magnesium, potassium and calcium, are used as the iron-containing catalyst for the Fischer-Tropsch synthesis.  3. The method of producing hydrocarbons according to claim 1, characterized in that crystalline aluminosilicates with the structure ZSM-5, β are used as the acid component of the catalyst.  4. The method of producing hydrocarbons according to claim 1, characterized in that crystalline silicoaluminophosphates with the SAPO-5 structure are used as the acid component of the catalyst.  5. The method of producing hydrocarbons according to claim 1, characterized in that the catalytic composition contains 10-90 wt. % iron-containing Fischer-Tropsch synthesis catalyst and 10-90 wt. % acid component. 6. The method of producing hydrocarbons according to any one of paragraphs. 1-5, characterized in that the recovery of the Fischer-Tropsch synthesis catalyst is carried out in the composition of the catalytic composition with synthesis gas at a temperature of 220-400 ^o C, a pressure of 10-100 atm and a volumetric feed rate of synthesis gas of 100-5000 h ^-1 . 7. The method of producing hydrocarbons according to any one of paragraphs. 1-5, characterized in that the recovery of the Fischer-Tropsch synthesis catalyst is carried out before mixing with the acid component in a separate reactor at a temperature of 400-500 ^o C, a pressure of 50-100 atm and a volumetric flow rate of a hydrogen-containing gas of 2000-30000 h ^-1 .

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