RU2205171C1 - Liquid-phase process for production of long-chain hydrocarbons from co and h2 - Google Patents

Abstract

FIELD: petrochemical processes. SUBSTANCE: process involves use of fine spherical catalyst containing 91-98 wt % of cobalt or iron oxides and one or several cocatalysts selected from molybdenum, zirconium, potassium, and copper oxides in amounts 2 to 9 wt %. Process is carried out at 200-350 C, H₂/CO molar ratio (1-3):1, and hydrogen pressure 1-5 MPa. Catalyst is prepared by coprecipitation of main metal salts and one or several promoters initiated by adding 5- 10 wt % of viscous organic phase to aqueous solution. EFFECT: achieved viscous organic phase-assisted sphericity of catalyst to and enhanced process efficiency. 2 tbl, 1 dwg, 10 ex

Description

The invention relates to a method for producing long-chain C ₁₀ -C ₂₅ paraffins and chemical products from CO and H ₂ .

 The progress of the Fischer-Tropsch technology for the production of synthetic liquid fuels over the past decade has yielded significant results due to the solution of complex programs. The main directions in scientific research are the development of new catalytic systems, reactor designs and the improvement of process technological schemes.

 The special suitability of FT synthesis products as raw materials for the chemical industry has long been known. The first experiments on the synthesis in the liquid phase were carried out in 1930. In 1939-1942. experiments with iron catalysts were continued by Ruhrchemie. During the war by BASF and after the war by Bureau of Mines, Fuel Research Station also developed liquid-phase synthesis options. In 1955, a plant with a capacity of 250 thousand tons of hydrocarbons per year was designed by Koppers in India.

 The advantages of the fluidized catalyst bed in FT technology are being actively studied by Badgerlo and Schell-MDS. The first reactor was tested in the late 70s [1]. In 1990, the Slurry-bed reactor with a diameter of 1 m was developed. The modern Slurry-bed reactor (1993) was developed by Sasol. A reactor having a height of 22 m and a diameter of 5 m consists of a casing and cooling coils in which steam is formed. Syngas sparges from the bottom and rises through a layer of “slurry” phase, which consists of heavy liquid reaction products. The particles of the catalyst are distributed in it in a suspended state, ablation of the catalyst may be observed. The reactor has several advantages. Conditions corresponding to isothermal conditions are created (due to mixing), and the process temperature may be higher than in a reactor with a stationary catalyst bed [2]. It is possible to achieve higher product selectivities and conversion rates. The removal and addition of the catalyst can be carried out without difficulty, which allows the catalyst to be replaced from time to time without downtime. In the reactor, products are formed heavier than under similar conditions in a reactor with a stationary layer.

 As the liquid medium, the fraction of hydrocarbons obtained by Fischer-Tropsch synthesis with a sufficiently high boiling point is most suitable.

 In principle, any catalysts are applicable for FT synthesis in the liquid phase, but catalysts without a carrier have recently been preferred for the preparation of long chain paraffins.

Iron and cobalt are used as the base metal for FT synthesis catalysts; Under the influence of various reagents on freshly prepared catalysts, iron groups change the composition and structure of the catalyst, and phases that are really active in FT synthesis appear [3]. The industrial process "Sasol", developed in the late 80s, was carried out on an iron catalyst at 220-340 ^o C and a hydrogen pressure of 24-25 atm. At the same time, the hydrocarbon yield is 75-95%, of which about 60% are olefins. Cobalt catalysts are used at normal pressure, temperature 200-300 ^o With or moderate 5-30 atm and 180-250 ^o With [4].

 The first catalysts consisted of oxides; for example, only cobalt oxide, cobalt and chromium oxide, cobalt and zinc oxide. Thorium and magnesium have been found to increase activity. Modern cobalt catalysts consist of an oxide substrate (Si, Al, Ti, Zr, Mg, Si-Al, Ga, Ce, C, molecular sieves, zeolites). Promoters contribute to the recovery of Co, because the catalyst is poisoned due to the gradual oxidation or deposition of heavy hydrocarbons. Zr, V, Ti, Mg, Mn, Cr, Th, Ce, La, Ni, Fe, Mo, W, Nd, elements from Ia, IIa, and Ib subgroups increase activity and selectivity towards heavy hydrocarbons [5].

A known method of producing hydrocarbons from synthesis gas on a ruthenium catalyst (Ru / SiQi), silica gel is used as a carrier of ruthenium. The degree of carbon conversion is 9.3%, the selectivity for C ₃ -C ₁₀ hydrocarbons is 62.3%. The disadvantages include a low degree of conversion for CO and selectivity for the target products.

A known method for the synthesis of hydrocarbons on a catalyst, comprising Co, oxides of Mg, Zr on a carrier - kieselguhr with the following ratio of components: 100Co-6ZrO ₂ -10MgO. In the synthesis at atmospheric pressure, at T = 190-200 ^o C, the yield of liquid hydrocarbons of a heavy wide fraction is 130-190 g / nm ³ , the paraffin content is 10%. In the synthesis under pressure of 1.0 MPa on 100Co-6ZrO ₂ or TiO ₂ -10MgO-200 catalysts on kieselguhr, the main product is solid paraffin [6].

The catalyst, known from (A.S. USSR 599832), containing, wt.%: Co - 28.0-31.4; MoO _s - 1.1-3.0; ZrO ₂ 3.1-4.1; carrier synthetic amorphous aluminosilicate or a mixture of aluminosilicate with the addition of 7-20% zeolite - the rest. The catalyst does not allow in the FT process to obtain a significant amount of hydrocarbons with a boiling point in the range of 225-335 ^o C.

The process developed by BASF and Bureau of Mines is used as a prototype. The process is carried out using precipitated iron catalysts and synthesis gas of different compositions. The temperature of the process is 230-260 ^o C, the hydrogen pressure of 1 MPa provides the conversion of synthesis gas by 90%. The liquid product consists of 79% hydrocarbons with a boiling range of gasoline (50-190 ^o C) and 13% with a boiling range of the diesel fraction (220-320 ^o C). Disadvantages: loss of catalyst in the form of dust carried away by oil; plugging the slurry separator with the catalyst; a small amount (50%) of spherical catalyst particles [7].

The objective of the present invention is to develop the preparation of catalysts by the method of coprecipitation for the selective production of CO and H ₂ hydrocarbons With ₁₀ -C ₂₅ .

 The solution of this problem is achieved by the fact that the catalyst, including cobalt or iron, oxides of copper, potassium, zirconium, molybdenum, is precipitated by precipitants in an aqueous solution, into which 5-10% of the organic viscous phase is introduced.

The catalyst used in the synthesis gas conversion process is prepared by coprecipitation of water-soluble salts of the base metal — Co or Fe and cocatalysts — salts of Cu, Zr, Mo, K. The concentration of the base metal salt in the solution is 5–10%, and the urea is precipitated to pH ≤8. -9 and adjusting the pH to a highly alkaline 25% ammonia solution. The synthesis is carried out at T 60-80 ^o C. the resulting precipitate is filtered. The heat treatment of the catalyst is carried out at T = 95-120 ^o C for 4 hours in a muffle, the resulting mass is heated to 200 ^o C to convert hydroxides to oxides. The recovery of the catalyst is carried out at T = 200-500 ^o With in a stream of H ₂ or (H ₂ + CO), the volumetric feed rate of the reducing agent of 9-12 l / h

Example 1
An iron salt was taken as the main metal salt, and an additional 7.2 ml of 0.5 N was added to the solution. CON. In water heated to 60 ^o With successively with stirring, we introduce salts of Fe, Zr, Mo. Then we introduce 5-10% of the preheated viscous organic phase. Precipitation is carried out with urea to a pH of 8-9 and then adjusted to a pH of 10-11 with 25% ammonia solution. The simultaneous coprecipitation of all salts in the viscous phase occurs, the formation of a fine precipitate with particles of a spherical shape is achieved. The resulting suspension is filtered, washed with water. Then the catalyst is subjected to heat treatment.

The resulting catalyst has the composition: Fe ₂ O ₃ - 96 wt.%, ZrO ₂ - 1 wt.%, MoO ₃ - 1 wt.%, K ₂ O - 2 wt.%.

After carrying out the reduction of the catalyst in a hydrogen stream with a volumetric rate of hydrogen supply of 12 l / h, it is tested for activity in the Fischer-Tropsch synthesis process at a temperature of 200-350 ^o C, a molar ratio of H ₂ / CO equal to (1-3): 1, hydrogen pressure 1 MPa.

 Schematic diagram of the reactor is shown in the drawing.

The composition of the obtained products: C ₁ -C ₅ - 10.2 wt.%, C ₆ -C ₇ - 20.4 wt.%, C ₈ -C ₂₃ - 69.4 wt.%, Of which gaseous - 14.5 wt.%, liquid - 79.5 wt.%, solid - 6.0 wt.%.

 The process conditions and results are presented in table 1.

Example 2
The preparation of the catalyst is carried out analogously to example 1. In example 2, another organic viscous phase, glycerol, was used. The resulting catalyst contains, wt.%:
Fe ₂ O ₃ - 96
ZrO ₂ - 1
MoO ₃ - 1
K ₂ O - 2
The composition of the obtained products in FT synthesis: C ₁ -C ₅ - 10.0 wt.%, C ₆ -C ₇ - 20.0 wt.%, C ₈ -C ₂₃ - 70.0 wt.%, Of which gaseous - 13.0 wt.%, Liquid - 80.0 wt.%, Solid - 7.0 wt.%
The introduction of glycerol leads to a significant increase in the activity of the catalyst. Achieved greater than the prototype yield of liquid products and reduced gaseous output, however, glycerin is easily mixed with water and technologically there was a synthesis of the catalyst in cobalt-based paraffin.

 Data on the composition of the catalysts, activity and composition of liquid hydrocarbons are presented in table. 1.

Example 3-6
The cobalt salt was taken as the main metal salt. The composition of the catalysts varied. The process of preparation, recovery and study of the activity of the catalysts is analogous to example 1. Mo and Zr have a particular effect on the activity of the catalyst. Co-Zr catalyst operates at higher temperatures.

 The heat treatment, recovery and study of the activity of the catalysts is similar to example 1. Data on the composition of the catalysts, activity and composition of liquid hydrocarbons are presented in table. 2.

 According to SEM, all catalyst samples have associates of spherical particles with d = 0.1-0.05 mm in the organic phase (90%). Due to the density and sphericity, the ablation of the catalyst is reduced and the catalyst bed remains fixed. Variations in catalysts affect the yield of liquid products, although the total activity of cobalt catalysts is higher than that of iron ones.

Analysis of the table data shows that the inventive method allows to obtain hydrocarbons With ₁₀ -C ₂₅ from the synthesis gas in the liquid phase using a spherical, finely divided precipitated proposed catalyst, since the contact time of the synthesis gas with the catalyst to the specified conversion in the prototype is 16.2 s ( _XCO = 45% U = 250 h ^-1 , L = 6 m), while in the proposed method the specified conversion for cobalt catalyst is achieved in less time ( _XCO = 300 h ^-1 U = 300 h ^-1 , L = 5 m).

Sources of information
1. B. Jager, M.E. Dry, T. Shingles, Steynberg, "Experience with a new type of reactor of Fischer-Tropschs Sinthesis", Catalyst Letters, 7 (1990) 293-302 p.

 2. M. F. Post, A. Van't Hoog, J.K. Minderhound and S.T. Sie, ALChEJ. 35 (7), 1989, 225-274 p.

3. Kagan Yu.B., Loktev S.M. et al. Development of ideas about the mechanism of syntheses from CO and H ₂ on iron catalysts. Petrochemistry, 1988, v. 28.

4. Catalysis in C ₁ chemistry / Ed. V. Kaima, per. from English I.I. Moiseeva. L .: Chemistry, 1987.

 5. B. Jager, R. Espinoza, Catalysis Today 23 (1995) 17-28.

 6. Nefedov BK Synthesis of organic compounds based on carbon monoxide. M .: Nauka, 1978, pp. 8-10.

 7. Chemicals from coal / Ed. Yu. Falbe. M.: Chemistry, 1980, 640 p.

Claims (1)

A method for producing long-chain paraffin hydrocarbons from CO and H ₂ in the liquid phase in the presence of a catalyst, characterized in that the process uses a finely dispersed, spherical catalyst obtained by coprecipitation of salts of the base metal - cobalt or iron in an amount of 91-98 wt. % and one or more socialization - salts of molybdenum, zirconium, potassium, copper in an amount of 2-9 wt. %, while to obtain the above catalyst, 5-10 wt. % of the components of the viscous organic phase and the above process is carried out at a temperature of 200-350 ^o With a molar ratio of N ₂ / CO equal to 1-3: 1, a hydrogen pressure of 1-5 MPa.

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