Highly heat-resistant copper-based carbon monoxide isothermal shift catalyst and preparation method thereof

Abstract

The present invention belongs to the field of catalyst technology, and specifically relates to a copper-based isothermal shift catalyst for the reaction of carbon monoxide with water vapor to generate carbon dioxide and hydrogen and a preparation method thereof. The catalyst weight percentage is composed of: 35-50% copper oxide, 25-40% zinc oxide, 5-15% aluminum oxide, 5-15% structural additive M oxide, M is one or more mixtures of Cr, Mg, Fe, Mn, and Zr, and N is one or more mixtures of Li, Na, K, Rb, La, and Ce. The catalyst is prepared by coprecipitation, and by adding other structural additives, the heat transfer performance of the catalyst is enhanced, and the heat resistance performance is significantly improved, the dispersion of the active component Cu is improved, and Cu is effectively inhibited from growing up under high temperature conditions, so that it is suitable for isothermal shift reaction processes with high CO content.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a copper-based isothermal conversion catalyst for the reaction of carbon monoxide with water vapor to generate carbon dioxide and hydrogen and a preparation method thereof. Background Art

[0002] CO and water vapor undergo a shift reaction on the catalyst to produce hydrogen required for the ammonia synthesis reaction, and produce CO2 as a by-product, which is used to produce ammonium carbonate or urea. The CO shift reaction is an important intermediate link in the ammonia synthesis process. The higher the CO conversion rate, the smaller the load of the subsequent purification process, which is of great significance for energy saving and consumption reduction.

[0003] The CO shift reaction is a typical gas-solid phase catalytic reaction. Since the structure of the adiabatic fixed bed is relatively simple, and the gas passes through the catalyst layer in a piston flow, there is little axial backmixing, and the gas conversion rate is high, adiabatic fixed bed reactors have been used for a long time in large-scale industrial production processes. However, in actual operation, a single-stage adiabatic reactor cannot achieve a very high efficiency, so a multi-stage adiabatic bed process is usually used, but there are disadvantages such as large steam and gas and high energy consumption. In addition, the reduction reaction before the catalyst is used releases a lot of heat, which poses a great hidden danger to the life of the catalyst. This shows that the adiabatic bed form has serious shortcomings.

[0004] The isothermal conversion process builds a heat exchanger in the reactor, and the granular catalyst exchanges heat with the cooling water pipe wall, and the

[0005] Remove reaction heat and keep the bed basically at a constant temperature, effectively solving a series of problems in operation.

[0006] In the past, many documents have detailed the development of CO shift catalysts and processes, but there are fewer discussions on the development of reactors, especially the new isothermal reactors that have been developed. Catalysts are the key to realizing advanced processes, and the selection of reactors has a great relationship with the best activity and life of catalysts. Only when the two are organically combined can energy saving and consumption reduction be achieved and the best process indicators be achieved.

[0007] So far, the market has adopted traditional low-temperature shift catalysts and isothermal reactors for use. The CO content in the raw gas of this process is as high as 60%-70%. The low-temperature shift catalyst has poor heat resistance, and the reaction hotspot temperature is lower than 290°C, which can be used normally. When the system is abnormal, the heat generated by the reaction cannot be effectively removed, and the reaction hotspot temperature may be higher than 300°C, or even 350°C. The performance of the low-temperature shift catalyst decreases rapidly and cannot meet production needs. It is urgent to develop a highly heat-resistant copper-based carbon monoxide isothermal shift catalyst to meet the requirements of the isothermal shift reaction process. Summary of the invention

[0008] The purpose of the present invention is to overcome the disadvantage that traditional copper-based low-temperature shift catalysts cannot withstand high temperatures above 300°C, and to provide a highly heat-resistant copper-based isothermal shift catalyst suitable for high CO content (>60 volume %) to meet the requirements of the isothermal shift reaction process.

[0009] The invention is characterized in that the catalyst composition introduces additives M and N on the basis of Cu, Zn and Al, M and Al play the role of dual carriers, enhance the heat transfer performance of the catalyst, N improves the dispersion of the active component Cu, effectively inhibits the growth of Cu under high temperature conditions, and is therefore suitable for isothermal shift reaction processes with high CO content.

[0010] The catalyst composition of the present invention comprises, by weight percentage: 30-50% copper oxide, 25-40% zinc oxide, 5-15% aluminum oxide, 5-15% additive M oxide, and 1-5% additive N oxide.

[0011] Generally, the structural additive M in the catalyst composition described in the present invention is one or a mixture of Cr, Mg, Fe, Mn and Zr.

[0012] In the catalyst composition described in the present invention, the structural auxiliary agent N is one or a mixture of Li, Na, K, Rb, La and Ce.

[0013] The catalyst of the present invention is prepared by a precipitation method, and the specific steps are as follows:

[0014] (1) dissolving the auxiliary agent M salt in deionized water; (2) adding the M salt solution to a solution containing copper nitrate and zinc nitrate and mixing them evenly; (3) adding an alkaline precipitant and deionized water to a reactor equipped with a stirring paddle and water bath heating and stirring them evenly; (4) adding the mixed solution of step (2) to the alkaline precipitant at a uniform speed for precipitation and aging; (5) the aged material is precipitated and washed, and the auxiliary agent N oxide and alumina powder are added to slurry for 0.3-0.5h; (6) the slurried material is filtered, dried, ground, granulated, roasted, and tableted to obtain a catalyst.

[0015] In the catalyst preparation method described in the present invention, the auxiliary agent M salt is one or a mixture of its corresponding nitrate, carbonate, and hydroxide.

[0016] In the step (1) of the catalyst preparation method of the present invention, the molar ratio of metal M to Cu in the additive M salt is 0.08-0.3.

[0017] In step (4) of the catalyst preparation method of the present invention, the speed of adding the mixed solution is 60-65 ml / min.

[0018] In step (4) of the catalyst preparation method of the present invention, the neutralization temperature is 65-70° C., and the end point pH value is 7.0-7.2.

[0019] In step (4) of the catalyst preparation method of the present invention, the aging temperature is 65-70° C. and the aging time is 0.3-0.5 h.

[0020] The molar ratio of metal N to Cu in the auxiliary oxide added in step (5) of the catalyst preparation method of the present invention is 0.01-0.08.

[0021] In step (6) of the catalyst preparation method of the present invention, the material calcination temperature is 400-500° C. and the calcination time is 3-5 h.

[0022] The effect of the present invention is that in the process of catalyst preparation, by adding other structural additives, the structure of the catalyst is improved, the heat transfer performance of the catalyst is enhanced, the dispersion of the active component Cu is improved, and the growth of Cu under high temperature conditions is effectively inhibited, so that it is suitable for the isothermal shift reaction process with high CO content. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific implementation modes.

[0024] Example 1

[0025] 400mL of 3.5mol / L copper nitrate solution, 220mL of 3.5mol / L zinc nitrate solution, and 120mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 70°C. 3.5L of 1mol / L sodium carbonate solution was put into a reactor with a stirring paddle and water bath heating. At a temperature of 70°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 60ml / min. The end point pH value was 7.0. Aged at 70°C for 0.5h with stirring. The aged material was washed by sedimentation for 5 times, and 5g of N oxide and 40g of alumina powder were added for slurrying for 0.3h. The slurried material was filtered, dried, ground, granulated, calcined at 500°C for 3h, and tableted to obtain catalyst sample S-1.

[0026] Example 2

[0027] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor equipped with a stirring paddle and water bath heating. 380mL of 3.5mol / L copper nitrate solution, 240mL of 3.5mol / L zinc nitrate solution and 130mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 68°C. At 68°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 65ml / min. The end point pH value was 7.1. Aged at 68°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 6g of N oxide and 45g of alumina powder were added for slurrying for 0.5h. The slurried material was filtered, dried, ground, granulated, calcined at 450°C for 4h, and tableted to obtain catalyst sample S-2.

[0028] Example 3

[0029] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor with a stirring paddle and water bath heating. 420mL of 3.5mol / L copper nitrate solution, 200mL of 3.5mol / L zinc nitrate solution and 140mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 65°C. At 65°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 62ml / min. The end point pH value was 7.2. Aged at 65°C for 0.3h with stirring. The aged material was washed by sedimentation for 5 times, and 5.5g of N oxide and 42g of alumina powder were added for slurrying for 0.4h. The slurried material was filtered, dried, ground, granulated, calcined at 450°C for 4h, and tableted to obtain catalyst sample S-3.

[0030] Example 4

[0031] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor with a stirring paddle and water bath heating. 410mL of 3.5mol / L copper nitrate solution, 210mL of 3.5mol / L zinc nitrate solution and 135mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 70°C. At 70°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 60ml / min. The end point pH value was 7.1. Aged at 70°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 5g of N oxide and 40g of alumina powder were added for slurrying for 0.3h. The slurried material was filtered, dried, ground, granulated, calcined at 450°C for 4h, and tableted to obtain catalyst sample S-4.

[0032] Example 5

[0033] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor equipped with a stirring paddle and water bath heating. 390mL of 3.5mol / L copper nitrate solution, 210mL of 3.5mol / L zinc nitrate solution and 130mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 67°C. At 67°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 60ml / min. The end point pH value was 7.0. Aged at 67°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 3.8g of N oxide and 43g of alumina powder were added for slurrying for 0.5h. The material after slurrying was filtered, dried, ground, granulated, roasted at 400°C for 5h, and tableted to obtain catalyst sample S-5.

[0034] Example 6

[0035] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor equipped with a stirring paddle and water bath heating. 380mL of 3.5mol / L copper nitrate solution, 230mL of 3.5mol / L zinc nitrate solution and 125mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 65°C. At 65°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 65ml / min. The end point pH value was 7.1. Aged at 65°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 3.5g of N oxide and 35g of alumina powder were added for slurrying for 0.4h. The slurried material was filtered, dried, ground, granulated, calcined at 430°C for 4.5h, and tableted to obtain catalyst sample S-6.

[0036] Example 7

[0037] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor with a stirring paddle and water bath heating. 425mL of 3.5mol / L copper nitrate solution, 215mL of 3.5mol / L zinc nitrate solution and 145mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 70°C. At 70°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 60ml / min. The end point pH value was 7.1. Aged at 70°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 4.5g of N oxide and 45g of alumina powder were added for slurrying for 0.4h. The slurried material was filtered, dried, ground, granulated, calcined at 460°C for 4.5h, and tableted to obtain catalyst sample S-7.

[0038] Example 8

[0039] 3.5L of 1mol / L sodium carbonate solution was prepared and put into a reactor equipped with a stirring paddle and water bath heating. 395mL of 3.5mol / L copper nitrate solution, 225mL of 3.5mol / L zinc nitrate solution and 135mL of 1.0mol / L auxiliary agent M salt mixture were prepared into 1.8L of mixed solution A at 68°C. At 68°C, the mixed solution A was added to the sodium carbonate solution at a uniform speed of 65ml / min. The end point pH value was 7.0. Aged at 68°C for 0.4h with stirring. The aged material was washed by sedimentation for 5 times, and 4g of N oxide and 40g of alumina powder were added for slurrying for 0.5h. The material after slurrying was filtered, dried, ground, granulated, calcined at 450°C for 4h, and tableted to obtain catalyst sample S-8.

[0040] Comparative Example 1

[0041] Prepared according to Example 1 of patent CN 101786000 A.

[0042] The copper and zinc solutions in the comparative example were precipitated with the sodium carbonate solution under the same precipitation conditions as the comparative example. During the precipitation process, an equal amount of Al(NO3)3 solution in the comparative example was added for co-precipitation. After aging and washing away impurity ions from the precipitated product, 40 g of monohydrated gallium oxide was added while stirring. After aging at 60°C for 0.5 h, the product was calcined at 400°C for 2 h, and finally graphite as a molding aid was added and pressed into tablets of φ5×4.5-5 mm to obtain comparative example D-1.

[0043] The relevant performance test results of the samples prepared in the eight embodiments of the present invention and the comparative examples are shown in Tables 1-3 below.

[0044] Catalyst performance test conditions:

[0045] Fixed bed reactor, catalyst loading 40ml, catalyst crushing particle size 0.85-2.0mm, raw gas composition (v / v%): CO 5%-15%, CO24%-10%, H2 35%-70%, CH45%-15%, steam-gas ratio (water vapor / dry gas molar ratio) 0.45, reaction pressure 3.0MPa, space velocity 2000h -1 , inlet temperature 220℃-260℃. The catalyst needs to be reduced before use, activation conditions: reducing atmosphere N2 / H2 mixed gas (N2 accounts for 5%, the rest is H2); reduction pressure: 0.4-0.5Mpa; reduction space velocity 1000h -1 ; The temperature was slowly raised to 230℃ and kept there for 2.0h (heating rate 1℃ / 3min).

[0046] CO conversion rate calculation formula:

[0047] E= ×100

[0048] Where: Φ1: CO volume fraction in the inlet gas (raw gas), %

[0049] Φ2: CO volume fraction in the outlet gas (product gas), %.

[0050] Table 1 Conversion rate data of samples prepared in Examples and Comparative Examples at different inlet temperatures of 220°C (%)

[0051]

[0052] Table 2 Conversion rate data of samples prepared in Examples and Comparative Examples at different inlet temperatures of 240°C (%)

[0053]

[0054] Table 3 Conversion rate data of samples prepared in Examples and Comparative Examples at different inlet temperatures of 270°C (%)

[0055]

[0056] It can be seen from the data in Tables 1 to 3 that the catalyst prepared by the present invention has excellent performance, especially as the inlet temperature increases, the hot spot temperature of the bed layer also increases continuously, and the catalyst prepared by the present invention decreases, but still maintains a good level (close to the value of the theoretical conversion rate), but the performance of the comparison sample decreases significantly. The comparison shows that the catalyst prepared by the present invention has a significant improvement in heat resistance and can withstand a temperature of up to 350°C.

[0057] The present invention and its implementation methods are described schematically above, and the description is not restrictive. Therefore, if a person skilled in the art is inspired by it and creatively designs similar solutions and embodiments to the technical solution without departing from the purpose of the invention, they should all fall within the scope of protection of the present invention.

Claims

1. Use of a catalyst in an isothermal shift reaction of carbon monoxide, characterized in that: Application conditions: raw gas composition volume percentage: CO 5%-15%, CO24%-10%, H2 65%-70% and CH45%-15%, steam-gas ratio, i.e. water vapor / dry gas molar ratio 0.45, reaction pressure 3.0MPa, space velocity 2000h -1 , inlet temperature 220℃-260℃, reaction temperature rise 70℃; The catalyst composition includes the following components in weight percentage: 30-50% copper oxide, 25-40% zinc oxide, 5-15% aluminum oxide, 5-15% additive M oxide, 1-5% additive N oxide, wherein: M is one or a mixture of Cr, Mg, Fe, Mn, Zr, and N is one or a mixture of Li, Na, K, Rb, La, and Ce; The preparation method of the catalyst comprises the following steps: 1) dissolving the auxiliary agent M salt in deionized water, wherein the molar ratio of metal M to Cu in the auxiliary agent M salt is 0.08-0.3; the auxiliary agent M salt is nitrate of M; 2) Add the additive M saline solution into the solution containing copper nitrate and zinc nitrate and mix well; 3) Add alkaline precipitant and deionized water into a reactor equipped with a stirring paddle and water bath heating, and stir evenly; 4) uniformly adding the mixed solution of step 2) into an alkaline precipitant for precipitation, and aging at 60-65° C. for 0.3-0.5 h; the mixed solution addition rate is 60-65 mL / min, the neutralization temperature is 65-70° C., and the end point pH value is 7.0-7.2; 5) The aged material is settled and washed, and the additive N oxide and alumina powder are added for slurrying for 0.3-0.5h; the molar ratio of metal N to Cu in the additive N oxide is 0.01-0.08; 6) After pulping, the material is filtered, dried, ground, granulated, calcined at 400-500° C. for 3-5 hours, and pressed into tablets to obtain the catalyst.

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