Preparation method and application of catalyst for directly preparing kerosene-rich component from synthesis gas

Abstract

The invention relates to the field of direct preparation of a kerosene-rich component catalyst from synthesis gas. A preparation method of a catalyst for directly preparing kerosene-rich components from synthesis gas comprises the following steps: firstly preparing an active M metal oxide, then preparing an N metal oxide auxiliary agent modified active M metal oxide, then preparing a C-layer coated N metal oxide auxiliary agent modified active M metal oxide, and finally adding an acid or alkali auxiliary agent to prepare the kerosene-rich component catalyst. And putting the active M metal oxide modified by the N metal oxide auxiliary agent wrapped by the C layer into an acid or alkali auxiliary agent aqueous solution, uniformly stirring, standing for 24-48 hours, and drying at 60-120 DEG C to obtain the catalyst for directly preparing the kerosene-rich component from the synthesis gas. The prepared catalyst has a core-shell structure, an acid or alkali auxiliary agent is located on a C shell layer, and good dispersity is kept.

Description

Technical Field

[0001] The invention relates to the field of catalyst for directly preparing kerosene-rich components from synthesis gas. Background Art

[0002] Under the background of dual carbon and the growing demand for aviation fuel, the preparation of green aviation kerosene from the synthesis gas obtained from biomass gasification has been favored by many researchers. At present, the foreign companies that have achieved the commercial production of aviation kerosene by CO hydrogenation using Fischer-Tropsch synthesis technology are mainly Shell of the Netherlands and Sasol of South Africa. However, both companies need to go through multiple steps of reaction to obtain aviation kerosene products, and the preparation process is relatively complicated. The difficulty of this technology lies in that the product distribution is determined by the chain growth factor α, which determines the C8~C 16 Theoretically, the maximum selectivity of components is only 41%. Traditional Fischer-Tropsch synthesis catalysts, especially cobalt-based catalysts, are generally used to produce C 19 + Mainly heavy hydrocarbons, middle distillates, especially C8~ C 16 The yield is low. This is mainly due to the single active site of the catalyst and the strong chain growth ability of CC coupling. The key to this technology is to develop a bifunctional catalyst to achieve direct generation of intermediate distillates from CO hydrogenation and improve the C8~C 16 Component selectivity. Therefore, the structural design of bifunctional catalysts is the core. Bifunctional catalysts have significant structural sensitivity. The particle size and dispersibility of the active phase, the type and amount of the co-catalyst, the acid strength of the carrier, and the diffusion effect of the carrier pore structure all have a significant impact on the reaction.

[0003] Traditional bifunctional catalysts use the shape selectivity of molecular sieves. Usually, active metal oxides are physically mixed with molecular sieves or a core-shell structure is constructed. By adjusting the distance between the two active sites, the intermediate fraction product can be obtained with high selectivity. However, carbon deposition on the surface or in the pores of the molecular sieve is inevitable during the reaction, leading to catalyst deactivation. And usually, the gasoline fraction C5~C 12 High, while C8~C 16 The components are relatively few, that is, the catalyst has a higher gasoline fraction selectivity, while the kerosene components are relatively few. Therefore, the present invention is significantly different from the traditional catalyst in that it does not utilize the shape selectivity effect of the molecular sieve, but changes the microscopic reaction environment of the metal active site, thereby changing the product selectivity of the catalyst, and this application has not been reported. Therefore, by regulating the reaction microenvironment of the catalyst active site, the synthesis gas is directly converted into an intermediate distillate oil rich in kerosene components and its timely desorption is promoted, and C8~C are synthesized with high selectivity. 18 Jet fuel components have important academic value and practical significance. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a catalyst for directly preparing a kerosene-rich middle distillate from synthesis gas and its application in directly preparing a kerosene-rich middle distillate from synthesis gas.

[0005] The technical solution adopted by the present invention is: a method for preparing a catalyst rich in kerosene components directly from synthesis gas, which is carried out according to the following steps: Step 1, preparation of active M metal oxide, adding M metal salt to ammonia solution, stirring continuously in a water bath at 60-80°C to uniformly mix to obtain a mixed solution with a pH of 9.0-11, continuing to stir the mixed solution for 2-6 hours, aging for 2-6 hours, filtering and washing, drying at 60-100°C for 12-24 hours, then heating to 300-500°C at a heating rate of 1-3°C / min, and then calcining at 300-500°C for 2-6 hours to obtain active M metal oxide; Step 2, preparation of active M metal oxide modified by N metal oxide additive, dissolving N metal nitrate in anhydrous ethanol, adding active M metal oxide, stirring evenly for 30-60 min, transferring the mixed solution into a rotary evaporator after stirring, gradually heating to 80-100 ° C for drying, transferring the dried product into a tubular furnace, heating to 300-500 ° C at a heating rate of 1-3 ° C / min under nitrogen protection, and then calcining at 300-500 ° C for 4-6 h to obtain active M metal oxide modified by N metal oxide additive; Step 3, preparation of active M metal oxide modified by N metal oxide additive wrapped in C layer, dissolving polyvinyl pyrrolidone (PVP) in anhydrous ethanol, then adding active M metal oxide modified by N metal oxide additive, stirring for 12-20h in a water bath at 50-60°C, centrifugally separating and washing the product, drying at 80-100°C, heating to 400-600°C at a heating rate of 1-3°C / min, and then calcining at 300-500°C for 3-5h to obtain active M metal oxide modified by N metal oxide additive wrapped in C layer, the mass ratio of N metal oxide to C layer wrapping is 5-10:0.1-2.0, wherein C layer wrapping is a substance wrapping N metal oxide and M metal oxide; Step 4: Add an acid or base additive, place the active M metal oxide modified by the N metal oxide additive wrapped in the C layer in an acid or base additive aqueous solution, stir evenly, let stand for 24 to 48 hours, and dry at 60 to 120 ° C to obtain a catalyst for directly preparing kerosene-rich components from synthesis gas.

[0006] In step 1, the M metal is cobalt or iron, and the M metal salt is nitrate, acetate or hydrochloride.

[0007] In step 1, the concentration of the ammonia solution is 25 wt%, and the M concentration is 0.1-0.5 mol / L in the mixed solution with a pH of 9.0-11. In step 2, the N metal is one or a mixture of zirconium, aluminum, manganese, and magnesium.

[0008] In step 2, after the active M metal oxide is added, in the active M metal oxide modified by the N metal oxide additive, the mass ratio of the N metal oxide additive to the M metal oxide is 1-2:4-19.

[0009] The concentration of the acid or alkali additive aqueous solution is 0.3-0.6 g / ml, and the mass ratio of the acid or alkali additive to the active M metal oxide modified by the N metal oxide additive wrapped in the C layer is 3:5-8.

[0010] The acid auxiliary agent is one of citric acid, boric acid, acetic acid, etc. or a mixture of two thereof; the alkali auxiliary agent is one of ammonia water, ethylenediamine, urea, triethylamine, etc. or a mixture of two thereof.

[0011] The invention discloses a catalyst for preparing a catalyst for directly preparing a kerosene-rich component from synthesis gas. The catalyst can be used for a fixed-bed Fischer-Tropsch synthesis reaction. The reaction conditions are as follows: reaction pressure 1.5-6 MPa, reaction temperature 150-320°C, GHSV=500-3000 h -1 , the molar ratio of H2 and CO is 1.5~3.

[0012] The catalyst for directly preparing the intermediate distillate oil rich in kerosene components from synthesis gas of the present invention is composed of active components, additives and carriers, and its weight percentage composition is: active metal oxide M: 20-95%, oxide additive N: 5-10%, middle C layer (C layer wrapping): 0.1-2.0%, acid or alkali additive: 2-15%. The active component grain size is 20-150 nm, the shell thickness is 2-5 nm, and the catalyst specific surface area is 10-100 m 2 / g, pore volume 0.5~2.5 cm 3 / g, the catalyst particle size is 20-200 nm. The acid or base additive is located in the C shell layer and maintains good dispersion.

[0013] Compared with the prior art, the present invention has the following advantages: The catalyst prepared by the present invention has a core-shell structure, the acid or base additive is located in the C shell layer, and maintains good dispersibility. It has the characteristics of small core metal particle size, adjustable shell thickness (changing the amount of polyvinyl pyrrolidone), large specific surface area and large pore volume.

[0014] The catalyst prepared by the present invention can synthesize middle distillate oil with high selectivity, and the CO conversion rate reaches 70-90%, and the mass content of the product is: CH4<5%, C2-C7<15%, C8-C 18 ≥ 70%, C 19 +<9 %, CO2<1 %. DETAILED DESCRIPTION Example 1

[0015] 1) Preparation of cobalt-based catalyst: Add concentrated ammonia solution (25 wt%) to 0.1 mol / L cobalt nitrate aqueous solution at 60 o The mixture was stirred continuously in a water bath at 60 °C to obtain a mixed solution with a pH of 9.0. The mixture was stirred continuously for 2 h at this temperature, aged for 2 h, filtered and washed, and then heated at 60 °C. o C for 12 h and then calcined at 300 °C for 2 h at a heating rate of 1 °C / min to obtain cobalt oxide.

[0016] 2) Weigh zirconium nitrate and dissolve it in 15 ml of anhydrous ethanol. Weigh 3 g of cobalt oxide and add it to the above solution and stir evenly for 30 min to make the mass fraction of zirconium oxide 5%. After stirring, transfer the mixed solution to a rotary evaporator and gradually heat it to 80 °C to dry the sample. Then transfer the dried sample to a tube furnace and introduce N2 (99.999%) at a flow rate of 30 ml / min and a heating rate of 1 °C / min. Calcinate at 350 °C for 4 h to obtain Zr-modified cobalt oxide.

[0017] 3) PVP was dissolved in 100 ml of anhydrous ethanol, 3 g of Zr-modified cobalt oxide was weighed and added to the PVP solution described above under ultrasonic conditions. Then, it was stirred for 12 h in a 50 °C water bath. Finally, the product was centrifuged and washed, and the sample was dried at 80 °C, and then calcined at 400 °C for 3 h under a nitrogen atmosphere at a heating rate of 1 °C / min to keep the C species content in the catalyst at 0.1%. Thus, a C-coated Zr-modified cobalt oxide sample was obtained.

[0018] 4) Dissolve 0.1 g of citric acid in 5 ml of H2O to form a solution, add 5 g of the above C-coated Zr-modified cobalt oxide sample, stir evenly, let stand for 24 h, and dry at 60 °C to obtain CAT-1.

[0019] It was applied to the Fischer-Tropsch synthesis reaction. Example 2

[0020] 1) Preparation of cobalt-based catalyst: Add concentrated aqueous ammonia (25 wt%) solution to 0.5 mol / L aqueous cobalt nitrate solution at 70o The mixture was continuously stirred in a water bath at 400 °C to obtain a mixed solution with a pH value of 9.0, which was continuously stirred for 2 h at this temperature, aged for 2 h, filtered and washed, dried at 60 °C for 12 h, and then calcined at 350 °C for 2 h at a heating rate of 1 °C / min to obtain cobalt oxide.

[0021] 2) Weigh manganese nitrate and dissolve it in 20 ml of anhydrous ethanol. Weigh 4 g of cobalt oxide and add it to the above solution and stir evenly for 30 min to make the mass fraction of manganese oxide 5%. After stirring, transfer the mixed solution to a rotary evaporator and gradually heat it to 80 °C to dry the sample. Then transfer the dried sample to a tube furnace and introduce N2 (99.999%) at a flow rate of 30 ml / min and a heating rate of 1 °C / min. Calcinate at 350 °C for 4 h to obtain Mn-modified cobalt oxide.

[0022] 3) PVP was dissolved in 100 ml of anhydrous ethanol, 3 g of Mn-modified cobalt oxide was weighed and added to the PVP solution described above under ultrasonic conditions. Then, it was stirred for 12 h in a 50 °C water bath. Finally, the product was centrifuged and washed, and the sample was dried at 80 °C, and then calcined at 400 °C for 3 h under a nitrogen atmosphere at a heating rate of 1 °C / min to keep the C species content in the catalyst at 2%. Thus, a C-coated Mn-modified cobalt oxide sample was obtained.

[0023] 4) Dissolve 0.35 g of boric acid in 10 ml of H2O to form a solution, add 7 g of the above C-coated Mn-modified cobalt oxide sample, stir evenly, let stand for 24 h, and dry at 60 °C to obtain CAT-2.

[0024] It was applied to the Fischer-Tropsch synthesis reaction. Example 3

[0025] 1) Preparation of iron-based catalyst: Add concentrated ammonia solution (25 wt%) to 0.2 mol / L ferric chloride solution at 60 o The mixture was stirred continuously in a water bath at 60 °C to obtain a mixed solution with a pH of 10.0. The mixture was stirred continuously for 2 h at this temperature, aged for 2 h, filtered and washed, and then heated at 60 °C. o C for 12 h and then calcined at 300 °C for 2 h at a heating rate of 1 °C / min to obtain iron oxide.

[0026] 2) Weigh aluminum nitrate and dissolve it in 15 ml of anhydrous ethanol. Weigh 3 g of cobalt oxide and add it to the above solution and stir evenly for 30 min, so that the mass fraction of aluminum oxide is 10%. After stirring, transfer the mixed solution to a rotary evaporator and gradually heat it to 80 °C to dry the sample. Then transfer the dried sample to a tube furnace and introduce N2 (99.999%) at a flow rate of 30 ml / min and a heating rate of 1 °C / min. Calcinate at 400 °C for 4 h to obtain aluminum-modified iron oxide.

[0027] 3) PVP was dissolved in 100 ml of anhydrous ethanol, 3 g of Al-modified iron oxide was weighed and added to the PVP solution described above under ultrasonic conditions. Then, it was stirred for 12 h in a 60 °C water bath. Finally, the product was centrifuged and washed, and the sample was dried at 80 °C, and then calcined at 400 °C for 3 h in a nitrogen atmosphere at a heating rate of 1 °C / min to keep the C species content in the catalyst at 0.5%. Thus, a C-coated Al-modified iron oxide sample was obtained.

[0028] 4) Dissolve 0.6 g of citric acid in 8 ml of H2O to form a solution, add 6 g of the above C-coated Zr-modified iron oxide sample, stir evenly, let stand for 24 h, and dry at 80 °C to obtain CAT-3.

[0029] It was applied to the Fischer-Tropsch synthesis reaction. Example 4

[0030] 1) Preparation of iron-based catalyst: Add concentrated ammonia solution (25 wt%) to 0.4 mol / L ferric nitrate aqueous solution at 60 o The mixture was stirred continuously in a water bath at 60 °C to obtain a mixed solution with a pH of 10.0. The mixture was stirred continuously for 2 h at this temperature, aged for 2 h, filtered and washed, and then heated at 60 °C. o C for 12 h and then calcined at 350 °C for 2 h at a heating rate of 2 °C / min to obtain iron oxide.

[0031] 2) Weigh manganese nitrate and dissolve it in 15 ml of anhydrous ethanol. Weigh 3 g of cobalt oxide and add it to the above solution and stir evenly for 30 min to make the mass fraction of manganese oxide 10%. After stirring, transfer the mixed solution to a rotary evaporator and gradually heat it to 80 °C to dry the sample. Then transfer the dried sample to a tube furnace and introduce N2 (99.999%) at a flow rate of 30 ml / min and a heating rate of 1 °C / min. Calcinate at 450 °C for 4 h to obtain manganese-modified iron oxide.

[0032] 3) PVP was dissolved in 100 ml of anhydrous ethanol, 5 g of manganese-modified iron oxide was weighed and added to the PVP solution described above under ultrasonic conditions. Then, it was stirred in a 60 °C water bath for 12 h. Finally, the product was centrifuged and washed, and the sample was dried at 80 °C, and then calcined at 400 °C for 3 h under a nitrogen atmosphere at a heating rate of 1 °C / min to keep the C species content in the catalyst at 1%. Thus, a C-coated manganese-modified iron oxide sample was obtained.

[0033] 4) Dissolve 3 g of ethylenediamine in 8 ml of H2O to form a solution, add 6 g of the above C-coated manganese-modified iron oxide sample, stir evenly, let stand for 24 h, and dry at 80 °C to obtain CAT-4.

[0034] It was applied to the Fischer-Tropsch synthesis reaction.

Claims

1. A method for preparing a catalyst for directly preparing a kerosene-rich component from synthesis gas, characterized in that: Follow the steps below Step 1, preparation of active M metal oxide, adding M metal salt to an ammonia solution, stirring continuously in a water bath at 60-80°C to uniformly mix to obtain a mixed solution with a pH of 9.0-11, continuing to stir the mixed solution for 2-6 hours, aging for 2-6 hours, filtering and washing, drying at 60-100°C for 12-24 hours, then heating to 300-500°C at a heating rate of 1-3°C / min, and then calcining at 300-500°C for 2-6 hours to obtain active M metal oxide; Step 2, preparation of active M metal oxide modified by N metal oxide additive, dissolving N metal nitrate in anhydrous ethanol, adding active M metal oxide, stirring evenly for 30-60 min, transferring the mixed solution into a rotary evaporator after stirring, gradually heating to 80-100 °C for drying, transferring the dried product into a tubular furnace, heating to 300-500 °C at a heating rate of 1-3 °C / min under nitrogen protection, and then calcining at 300-500 °C for 4-6 h to obtain active M metal oxide modified by N metal oxide additive; Step 3, preparation of active M metal oxide modified by N metal oxide additive wrapped in C layer, dissolving polyvinyl pyrrolidone in anhydrous ethanol, then adding active M metal oxide modified by N metal oxide additive, stirring for 12-20h in a water bath at 50-60°C, centrifuging and washing the product, drying at 80-100°C, heating to 400-600°C at a heating rate of 1-3°C / min, and then calcining at 300-500°C for 3-5h to obtain active M metal oxide modified by N metal oxide additive wrapped in C layer, the mass ratio of N metal oxide to C layer wrapping is 5-10:0.1-2.0, wherein C layer wrapping is a substance wrapping N metal oxide and M metal oxide; Step 4: Add an acid or base additive, place the active M metal oxide modified by the N metal oxide additive wrapped in the C layer in an acid or base additive aqueous solution, stir evenly, let stand for 24 to 48 hours, and dry at 60 to 120 ° C to obtain a catalyst for directly preparing kerosene-rich components from synthesis gas.

2. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 1, characterized in that: In step 1, the M metal is cobalt or iron, and the M metal salt is nitrate, acetate or hydrochloride.

3. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 1, characterized in that: In step 1, the concentration of the ammonia solution is 25 wt%, and in the mixed solution with a pH of 9.0-11, the M concentration is 0.1-0.5 mol / L.

4. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 1, characterized in that: In step 2, the N metal is one or a mixture of zirconium, aluminum, manganese and magnesium.

5. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 1, characterized in that: In step 2, after the active M metal oxide is added, in the active M metal oxide modified by the N metal oxide additive, the mass ratio of the N metal oxide additive to the M metal oxide is 1-2:4-19.

6. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 1, characterized in that: The concentration of the acid or alkali additive aqueous solution is 0.3-0.6 g / ml, and the mass ratio of the acid or alkali additive to the active M metal oxide modified by the N metal oxide additive wrapped in the C layer is 3:5-8.

7. The method for preparing a catalyst for directly converting synthesis gas into a kerosene-rich component according to claim 6, characterized in that: The acid auxiliary agent is one of citric acid, boric acid, acetic acid, etc. or a mixture of two thereof; the alkali auxiliary agent is one of ammonia water, ethylenediamine, urea, triethylamine, etc. or a mixture of two thereof.

8. An application of a catalyst prepared by the method for preparing a catalyst for directly preparing a kerosene-rich component from synthesis gas according to claim 1, characterized in that: The catalyst can be used for fixed bed Fischer-Tropsch synthesis reaction under the following reaction conditions: reaction pressure 1.5~6Mpa, reaction temperature 150~320℃, GHSV=500~3000 h -1 , the molar ratio of H2 and CO is 1.5~3.