A method for producing natural gas by low-temperature alkylation of synthesis gas

Abstract

The present invention provides a method for synthesizing natural gas by low-temperature and high-efficiency alkylation of synthesis gas, at a temperature of 200-300°C, a pressure of 0.01-5.0 MPa, and a space velocity of 500-50000 mL / (h·g cat ), H 2 Under the reaction conditions of a molar ratio of / CO of 1.0 to 12.0, the synthesis gas is efficiently alkylated under the action of a cobalt-gallium-based catalyst. The cobalt-gallium-based catalyst is composed of active metals Co, Ga 2 O 3 and an auxiliary agent. In this method, synthesis gas can be efficiently converted to natural gas at a temperature below 250°C, and the selectivity of natural gas in the product can be controlled to be above 90%. By controlling appropriate conditions and raw material composition, synthesis gas can be completely converted, and the proportion of natural gas in hydrocarbon products can reach 90%. The present invention has opened up a new route for low-temperature and efficient conversion of synthesis gas to natural gas.

Description

Technical Field

[0001] The invention relates to a method for low-temperature and high-efficiency alkylation of synthesis gas, and in particular to a method for low-temperature and high-efficiency alkylation of synthesis gas over a cobalt-gallium-based catalyst to produce natural gas. Background Art

[0002] As environmental problems become increasingly serious, natural gas, as a clean, safe and efficient fossil energy, has received more and more attention. Its proportion in the global energy consumption structure has increased year by year, and the demand for natural gas has increased year by year. Although my country has increased its natural gas imports, it still cannot make up for the energy consumption gap caused by my country's rapid economic development. Using my country's relatively abundant coal, renewable energy, etc. to produce natural gas through the methanation reaction of syngas can not only make up for the shortage of natural gas resources in my country, but also has important strategic significance for achieving the diversification of oil and gas resources, energy security, energy conservation and emission reduction.

[0003] The alkylation reaction of syngas is an exothermic reaction in which the number of molecules is reduced. Low temperature and high pressure are conducive to the reaction. At present, the technology of preparing natural gas by alkylation of syngas in China has become mature. Most of the catalysts used are nickel-based catalysts, which are mostly operated under high temperature conditions, usually at 300-500°C. However, the high-temperature operation of methanation catalysts is prone to sintering of catalyst active metals and degradation of catalytic reaction performance. In addition, at temperatures below 290°C, nickel-based catalysts are prone to react with CO to form carbonyl nickel, which causes irreversible damage to the catalyst. For this reason, in order to further reduce the energy consumption of the process, the development of low-temperature non-nickel-based high-efficiency catalysts and their use in the process of preparing natural gas by alkylation of syngas has become one of the research directions in this field. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for producing natural gas by low-temperature and high-efficiency alkylation of synthesis gas in view of the high reaction temperature of the nickel-based catalyst for alkylation of synthesis gas in the prior art.

[0005] The present invention provides a method for preparing natural gas by low-temperature and high-efficiency alkylation of synthesis gas, specifically, the method comprises the following steps: taking synthesis gas as raw gas, carrying out alkylation reactions such as methanation under the action of a cobalt-gallium-based catalyst to generate natural gas; the cobalt-gallium-based catalyst is composed of at least an active metal Co and a metal oxide Ga2O3, wherein the mass content of each component is: the active metal Co content is 30-80%, the metal oxide Ga2O3 content is 10-60%, and the content of other components is 0-60%.

[0006] The synthesis gas is a raw gas containing carbon monoxide and hydrogen, wherein the molar ratio of H2 to CO is 1-12, optimized to be 2-6; the raw gas does not contain or may contain one or more of the impurity gases such as CO2, CH4, C2H6, N2, Ar, etc., and the impurity gas content does not exceed 50% of the volume of the raw gas.

[0007] The metal oxide Ga2O3 refers to Ga2O3 that interacts with the active metal Co, and even forms CoGa2O4 with a spinel structure.

[0008] The specific surface area of ​​the metal oxide Ga2O3 carrier is 10 to 200 m 2 / g, optimized to 15~150m 2 / g.

[0009] The cobalt-gallium-based catalyst additive includes one or more of La2O3, CeO2, and Fe2O3, preferably one or two of La2O3 and Fe2O3, and preferably Fe2O3.

[0010] The preparation of the cobalt-gallium-based catalyst can be carried out by the following steps: (1) according to the catalyst composition ratio, dissolving soluble Co(II) salt, Ga(III) salt and auxiliary salt in an organic solvent to prepare a salt solution, wherein the concentration of Co(II) in the salt solution is 0.02-2.0 mol / L, and the concentration of Ga(III) is 0.001-0.05 mol / L; the soluble Co(II) salt and auxiliary salt refer to salt compounds that can be dissolved in an organic solvent, preferably one of nitrate, acetate or Two or more; (2) preparing an organic solvent solution of oxalic acid, wherein the concentration of oxalic acid is 0.1 to 5 mol / L; (3) quickly pouring the salt solution of step (1) into the solution of step (2), stirring for 10 to 90 minutes to uniformly mix the solution, standing for 12 to 36 hours, centrifuging or filtering to separate the precipitated product, and washing with an organic solvent until the pH value of the washed solution is 6 to 8, and drying the washed precipitated product at 80 to 130° C. for 10 to 48 hours to obtain the desired cobalt-gallium-based catalyst.

[0011] The organic solvents used in the preparation process and the washing process may be the same or different, and may be one or more of ketones, alcohols, and ethers, preferably one or more of acetone, ethanol, and methanol.

[0012] The alkylation method for preparing natural gas from synthesis gas has a reaction temperature of 200-300°C (preferably 200-250°C), a reaction pressure of 0.01-5.0MPa (preferably 0.1-3.0MPa), and a raw gas space velocity of 500-50000mL / (h·g cat ) preferably 1000 to 5000 mL / (h·g cat )).

[0013] The alkylation method for preparing natural gas from synthesis gas can realize low-temperature and high-efficiency alkylation of synthesis gas to produce natural gas, the content of synthesis gas after alkylation in the gas after reaction does not exceed 5%, and the mass content of C1-C4 alkanes in natural gas is greater than 80%.

[0014] The reduction conditions of the cobalt-gallium-based catalyst before use are: normal pressure, H2 (600-3000mL / (h·g cat )), 200-400℃ reduction time 1-10h.

[0015] When the synthesis gas is methanated to produce natural gas, the catalyst performance is evaluated by the following method: the prepared multifunctional catalyst is installed in the constant temperature section of the fixed bed reactor, and then the catalyst is reduced at 200-400°C for 1-10 hours in a H2 atmosphere, with a H2 space velocity of 600-3000 mL / (h·g cat ). After the reduction is completed, the reaction temperature is adjusted and the reducing gas is cut into the reaction gas. The reaction products are introduced into the chromatogram in gaseous form for online analysis. Among them, CO, N2, CH4 and CO2 are detected by TCD, and hydrocarbons are detected by FID.

[0016] The present invention has the following characteristics:

[0017] (1) The catalyst used in the present invention has a simple preparation method, high mechanical strength, good stability, is suitable for application in different types of reactors, and is suitable for large-scale industrial production;

[0018] (2) The present invention can realize the low-temperature and high-efficiency alkylation reaction of synthesis gas, with a simple reaction device, a short process flow, low equipment investment and low energy consumption;

[0019] In the method, the synthesis gas conversion rate can achieve complete conversion when the temperature is lower than 250°C, and the natural gas selectivity in the product can reach more than 85%. The present invention has developed a new method for producing natural gas by low-temperature and efficient alkylation of synthesis gas. DETAILED DESCRIPTION

[0020] The technical details of the present invention are described in detail by the following examples. It should be noted that the examples are only used to further illustrate the technical features of the present invention, rather than to limit the present invention.

[0021] Example 1

[0022] Preparation of Co-Ga Catalyst and Its Catalytic Performance

[0023] First, 0.04 mol Co(NO3)2˙6H2O and 0.01 mol Ga(NO3)3 hydrate (molecular weight 276.78) were dissolved in 100 ml acetone. Then, 0.075 mol H2C2O4˙2H2O was dissolved in 150 ml acetone. Subsequently, the acetone solution of the mixed salt was quickly poured into the acetone solution of H2C2O4˙2H2O, stirred for 20 minutes until the solution was uniformly mixed, and allowed to stand for 24 hours. After standing, centrifugation was used, washed with anhydrous ethanol until pH = 7, and the precipitate was placed in an oven at 110°C for 24 hours for drying, and the tablet was taken out for use and marked as catalyst A.

[0024] 1.3 g of the catalyst A prepared above was weighed and loaded into a fixed bed reactor for methanation reaction. Reduction conditions: normal pressure, pure H2 (30 mL / min), 370°C reduction time 1 h. Reaction conditions: raw gas molar ratio H2 / CO = 2.0, temperature 200-250°C, pressure 4.0 MPa, space velocity 2400 mL / (h·g cat ), the performance of syngas methanation reaction was investigated, and the results are listed in Table 1.

[0025] Table 1 Synthesis gas alkylation reaction performance over catalyst A

[0026]

[0027]

[0028] Note: The oxygen-containing compounds in the table mainly include alcohol compounds with carbon numbers of 1 to 5; natural gas mainly includes hydrocarbon compounds with carbon numbers of 1 to 4. Unless otherwise specified, the oxygen-containing compounds and natural gas compositions in the following tables are the same as those here.

[0029] It can be seen from the results in Table 1 that within the temperature range investigated, Catalyst A exhibits excellent syngas alkylation reaction performance, with CO conversion maintained at over 80% and the selectivity of natural gas in the product hydrocarbons maintained at over 80%. With increasing reaction temperature, CO conversion increases, and the selectivity of natural gas in the product hydrocarbons decreases slightly. When the reaction temperature increases to 235°C, CO conversion increases to over 95%, and the selectivity of natural gas in the product hydrocarbons is maintained at 80%. It can be seen from the results that the optimal reaction temperature of Catalyst A is 235-250°C.

[0030] Example 2

[0031] Preparation of Co-Ga Catalyst and Its Catalytic Performance

[0032] First, 0.02 mol Co(NO3)2·6H2O and 0.02 mol Ga(NO3)3·xH2O were dissolved in 100 ml acetone. Then, 0.05 mol H2C2O4˙2H2O was dissolved in 150 ml acetone. Then, the acetone solution of the mixed salt was quickly poured into the acetone solution of H2C2O4˙2H2O, stirred for 30 min until the solution was uniformly mixed, and allowed to stand for 24 h. After standing, centrifugation was used, washed with anhydrous ethanol until pH = 7, and the precipitate was placed in a 140°C oven for drying for 14 h, and the pellet was taken out for use and marked as catalyst B.

[0033] 1.0 g of the catalyst B prepared above was weighed and loaded into a fixed bed reactor for methanation reaction. Reduction conditions: normal pressure, pure H2 (50 mL / min), 350°C reduction time 4 h. Reaction conditions: raw gas molar ratio H2 / CO = 3.0, temperature 200-250°C, pressure 3.0 MPa, space velocity 2400 mL / (h·g cat ), the performance of the syngas methanation reaction was investigated, and the results are listed in Table 2. It can be seen from Table 2 that within the temperature range investigated, Catalyst B exhibits excellent syngas alkylation reaction performance, CO conversion rate remains above 89%, and the selectivity of natural gas in the product hydrocarbons remains at 72%. As the reaction temperature increases, the CO conversion rate of the reaction on Catalyst B increases, and the natural gas selectivity first drops to the minimum at 210°C, and then gradually increases. At 250°C, the syngas can be completely converted, and the natural gas selectivity in the product can reach 86.3%, and methane accounts for 74.3% of its components. The optimal reaction temperature is 225-250°C.

[0034] Table 2 Synthesis gas alkylation performance over catalyst B

[0035]

[0036]

[0037] Example 3

[0038] The steps of catalyst preparation and evaluation were the same as those in Example 2, except that 0.01 mol Co(NO3)2·6H2O and 0.04 mol Ga(NO3)3·xH2O were used. The prepared catalyst was labeled as catalyst C. The catalyst evaluation conditions were: temperature: H2 / CO=3.0, 235°C, pressure 1.0-5.0 MPa, space velocity 1200 mL / (h·g cat ), the alkylation reaction performance results on catalyst C are listed in Table 3.

[0039] Table 3 Reaction performance of syngas alkylation to natural gas over catalyst C

[0040]

[0041] As can be seen from Table 3, within the pressure range investigated, Catalyst C exhibits excellent syngas alkylation reaction performance, with the CO conversion rate maintained at over 85%, and even completely converted; the selectivity of the natural gas fraction (C1-C4 hydrocarbons) in the product hydrocarbons maintained at over 80%, and even reaching over 90%. As the pressure increases, the reaction performance of Catalyst C increases, and the CO conversion rate increases. When the pressure increases to 2.0 MPa, the CO conversion rate can increase to 95%, and when it continues to increase to 4.0 MPa, the complete conversion of CO can be basically achieved. The selectivity of natural gas in the product hydrocarbons decreases slowly with increasing pressure, and the rate of decrease increases after 3.0 MPa. Taking all factors into consideration, the optimal pressure range is 2.0-4.0 MPa.

[0042] Example 4

[0043] The catalyst preparation steps are the same as those in Example 2, except that 0.01 mol Co(NO3)2·6H2O and 0.04 mol Ga(NO3)3·xH2O are replaced by 0.01 mol Co(CH3COO)2·4H2O and 0.04 mol Ga(CH3COO)3 to obtain a cobalt-gallium-based catalyst, which is labeled as catalyst D.

[0044] The catalyst evaluation conditions are as follows: temperature: H2 / CO=5.0, 230°C, pressure 1.0 MPa, space velocity 1200-6000 mL / (h·g cat ), the alkylation reaction performance results on catalyst D are listed in Table 4.

[0045] Table 4 Reaction performance of syngas alkylation to natural gas over catalyst D

[0046]

[0047] From the results in Table 4, it can be seen that within the investigated space velocity range, Catalyst D exhibits excellent performance in the alkylation reaction of synthesis gas. The CO conversion rate remains above 93%, and can even be completely converted; the selectivity of methane in the product hydrocarbons remains above 85%, and even reaches above 95%. With the increase of space velocity, the CO conversion rate and the selectivity of natural gas in the product hydrocarbons decrease slightly, but even if the space velocity is increased to 6000mL / (h·g cat ), CO conversion and natural gas selectivity remain at a high level, but the methane content in the natural gas component decreases. Taking all factors into consideration, the optimal space velocity range of catalyst D is 1200~4800mL / (h·g cat ).

[0048] Example 5

[0049] The catalyst preparation steps are the same as those in Example 2, except that 0.01 mol Co(NO3)2·6H2O and 0.04 mol Ga(NO3)3·xH2O are replaced by 0.01 mol Co(NO3)2·6H2O, 0.04 mol Ga(NO3)3·xH2O and 0.001 mol Fe(NO3)3·9H2O to obtain a cobalt-gallium catalyst containing an iron additive, which is marked as Catalyst E.

[0050] The catalyst evaluation conditions were: temperature: H2 / CO=4.0, 240°C, pressure 2.0 MPa, space velocity 3000 mL / (h·g cat ), the syngas alkylation reaction performance results on catalyst E are listed in Table 5.

[0051] Example 6

[0052] The catalyst preparation steps are the same as those in Example 2, except that 0.01 mol Co(NO3)2·6H2O and 0.04 mol Ga(NO3)3·xH2O are replaced by 0.01 mol Co(NO3)2·6H2O, 0.04 mol Ga(NO3)3·xH2O and 0.001 mol Ce(NO3)3·6H2O to obtain a cobalt-gallium catalyst containing a cerium additive, which is marked as Catalyst F.

[0053] The catalyst evaluation conditions were: temperature: H2 / CO=4.0, 240°C, pressure 2.0 MPa, space velocity 3000 mL / (h·g cat ), the synthesis gas alkylation reaction performance results on catalyst F are listed in Table 5.

[0054] Example 7

[0055] The catalyst preparation steps are the same as those in Example 2, except that 0.01 mol Co(NO3)2·6H2O and 0.04 mol Ga(NO3)3·xH2O are replaced by 0.01 mol Co(NO3)2·6H2O, 0.04 mol Ga(NO3)3·xH2O and 0.001 mol La(NO3)3·6H2O to obtain a cobalt-gallium catalyst containing a cerium additive, which is marked as Catalyst G.

[0056] The catalyst evaluation conditions were: temperature: H2 / CO=4.0, 240°C, pressure 2.0 MPa, space velocity 5000 mL / (h·g cat ), the synthesis gas alkylation reaction performance results on catalyst G are listed in Table 5.

[0057] Table 5 Reaction performance of syngas alkylation to natural gas over cobalt-gallium-based catalysts with different promoters

[0058]

[0059] From the results in Table 5, it can be seen that the cobalt-gallium catalyst with additives exhibits excellent syngas alkylation reaction performance, and the CO conversion rate and natural gas selectivity are improved. Among them, the iron additive has the best effect, which can reach 98.3% CO conversion rate and 95.8% natural gas selectivity in hydrocarbon products. Methane accounts for 79% of the natural gas composition.

[0060] Example 8

[0061] The catalyst preparation steps and reaction evaluation steps were the same as those in Example 2, except that the reaction evaluation conditions of "raw gas composition molar ratio H2 / CO=2" were adjusted to "raw gas composition molar ratio H2 / (CO+CO2)=4, and the molar ratios of CO2 / CO were 0, 1 / 4, and 2 / 3, respectively". The evaluation conditions for the synthesis gas alkylation reaction of catalyst B were: temperature 200°C, pressure 3.0 MPa, space velocity 2400 mL / (h·g cat ), the reaction evaluation results are listed in Table 6.

[0062] Table 6 Synthesis gas alkylation reaction performance over catalyst B

[0063]

[0064]

[0065] From the results in Table 6, it can be seen that catalyst B has excellent reaction performance for the conversion of synthesis gas containing carbon dioxide to natural gas, the CO conversion rate can be controlled at more than 90%, and the selectivity of natural gas in hydrocarbon products can be controlled at more than 75%. Within the scope of investigation, as the CO2 content in the synthesis gas increases, the CO conversion rate and the product natural gas selectivity increase. This shows that the presence of an appropriate amount of carbon dioxide (CO2 / CO=0.01-0.67) in the synthesis gas is conducive to the conversion of synthesis gas into natural gas.

[0066] Example 9

[0067] Using the catalyst evaluation conditions of Example 5, a 200-hour stability test was conducted on Catalyst E. The reaction results are listed in Table 7.

[0068] Table 5 Reaction stability of synthesis gas alkylation to natural gas over cobalt-gallium-based catalysts containing iron promoters

[0069]

[0070] As shown in Table 7, the cobalt-gallium catalyst E containing an iron additive not only exhibits a higher syngas alkylation performance, but also exhibits good catalytic stability. During the 200-hour stability test, the CO conversion rate is stable at 98%, the proportion of natural gas in hydrocarbon products is stable at more than 95%, and methane accounts for 79% of the natural gas fraction.

Claims

1. A method for producing natural gas by low temperature alkylation of synthesis gas, characterized in that: Using synthesis gas as raw gas, a methanation and alkylation reaction takes place under the action of a cobalt-gallium-based catalyst to generate natural gas; The cobalt-gallium-based catalyst is composed of at least active metal Co and metal oxide Ga2O3, wherein the mass content of each component is: active metal Co content is 30-80%, metal oxide Ga2O3 content is 10-60%, and other auxiliary component content is 0-60%; The additive of the cobalt-gallium-based catalyst is selected from one or more of La2O3, CeO2, and Fe2O3. The metal oxide Ga2O3 in the cobalt-gallium-based catalyst can interact with the active metal Co and even partially or completely form spinel-structured CoGa2O4; The preparation of the cobalt-gallium-based catalyst adopts the following steps: (1) according to the catalyst composition ratio, soluble Co(II) salt, Ga(III) salt, and salt with or without additives are dissolved in an organic solvent to prepare a salt solution of 100 ml, wherein the concentration of Co(II) in the salt solution is 0.02-2.0 mol / L; the soluble Co(II) salt, Ga(III) salt and additive salt refer to salt compounds that can be dissolved in an organic solvent; (2) 150 ml of an organic solvent solution of oxalic acid is prepared, wherein the concentration of oxalic acid is 0.1-5 mol / L; (3) the salt solution of step (1) is poured into the solution of step (2), stirred for 10-90 minutes, allowed to stand for 12-36 hours, centrifuged or filtered to separate the precipitated product, and washed with an organic solvent until the pH value of the washed solution is 6-8, and the washed precipitated product is dried at 80-130° C. for 10-48 hours to obtain the desired cobalt-gallium-based catalyst; The catalyst needs to be reduced before use. The reaction temperature is 200~300℃, the reaction pressure is 0.01~5.0 MPa, and the feed gas space velocity is 500~50000 mL / (h∙g cat ) ; The synthesis gas is a raw gas containing carbon monoxide and hydrogen, wherein the molar ratio of H2 to CO is 1-12, and the raw gas contains no or one or more of the impurity gases CO2, CH4, C2H6, N2, and Ar, and the impurity gas content does not exceed 50% of the volume of the raw gas.

2. The method according to claim 1, characterized in that: The cobalt-gallium-based catalyst is composed of at least active metal Co and metal oxide Ga2O3, wherein the mass content of each component is: active metal Co content is 50-80%, metal oxide Ga2O3 content is 15-45%, and other auxiliary component content is 0-40%; The molar ratio of H2 to CO in the synthesis gas is 2-6.

3. The method according to claim 1, characterized in that: The specific surface area of ​​Ga2O3 carrier is 10~200 m 2 / g.

4. The method according to claim 1, characterized in that: The auxiliary agent of the cobalt-gallium-based catalyst is selected from one or two of La2O3 and Fe2O3.

5. The method according to claim 1, characterized in that: The specific surface area of ​​Ga2O3 carrier is 15~150 m 2 / g, the additive of cobalt-gallium-based catalyst is Fe2O3.

6. The method according to claim 1, characterized in that: In step (1), the soluble Co(II) salt, Ga(III) salt and auxiliary salt refer to one or more of nitrates and acetates that are soluble in organic solvents; The organic solvents used in the preparation of the cobalt-gallium-based catalyst in the solution preparation and washing process may be the same or different, and may be one or more of ketones, alcohols, and ethers.

7. The method according to claim 1, characterized in that: The reaction temperature is 200-250℃, the reaction pressure is 0.1~3.0MPa, and the feed gas space velocity is 2000~10000 mL / (h∙g cat ).

8. The method according to any one of claims 1 to 7, characterized in that: The raw gas of the method can realize low-temperature alkylation of synthesis gas to produce natural gas, the volume content of the main components hydrogen and / or carbon monoxide in the synthesis gas after alkylation does not exceed 5% in the gas after the reaction, and the mass proportion of C1-C4 hydrocarbons in the natural gas hydrocarbon fraction in the hydrocarbon products is greater than 80%.

9. The method according to claim 1, characterized in that: The catalyst was reduced under the following conditions: atmospheric pressure, H2 gas velocity of 600-3000 mL / (h·g cat ), 200~400℃ reduction time 1~10h.

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