A catalyst for preparing low-carbon alcohols from synthesis gas and its preparation method and application

Abstract

The present invention belongs to the field of catalyst preparation, and in particular to a catalyst for preparing low-carbon alcohols from synthesis gas, and its preparation method and application. The catalyst includes an active component Zn, an aluminosilicate carrier and an auxiliary agent CuO, wherein the active component is a core-shell structure, the innermost is CuO, and the outer part is covered with a Cu-Zn alloy, and the content of ZnO, CuO and the carrier is calculated as 30%-40%, 10%-20%, and 40%-60% by catalyst mass percentage. The catalyst of the present invention can be applied to the reaction of preparing low-carbon alcohols from synthesis gas, has excellent activity, selectivity and stability, and is conducive to industrial application and promotion.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a catalyst for preparing low-carbon alcohols from synthesis gas, and a preparation method and application thereof. Background Art

[0002] As a basic chemical raw material, low-carbon alcohol is a bridge and link between coal chemical industry, natural gas chemical industry and petrochemical industry. It has great strategic significance for optimizing and adjusting the structure of my country's petrochemical industry, alleviating the contradiction between energy supply and demand, promoting the diversification and quality improvement of raw materials for chemical product production, and enhancing international market competitiveness.

[0003] At present, the most widely used catalyst for the synthesis of low-carbon alcohols in industry is Cu-ZnO-Al2O3 catalyst, in which Cu is the main catalytic active component, ZnO is the synergistic catalytic active component, and Al2O3 is used as a carrier to provide support for the active components of the catalyst. However, the Cu-ZnO-Al2O3 catalyst prepared by traditional process has a low melting point of active metal Cu, and its Tammann temperature and Hüttig temperature are very low. It is easy to sinter and deactivate when used at high temperature. To prevent the sintering of the catalyst, it is necessary to prevent and slow down the migration of active centers and Ostwald ripening, and to make the uniform and stable active center Cu be fully isolated and fixed as much as possible. In the traditional preparation process, the Cu-Zn interval catalyst is obtained by coprecipitating copper nitrate and zinc nitrate, but this preparation method makes the distribution of Cu and Zn uneven. If the two are arranged according to a certain structure and Zn is regularly covered on Cu, the uniform isolation of the active center of the catalyst can be achieved, and the problems of uneven distribution of active components and carriers, weak adhesion to carriers, and migration and agglomeration of active components can be solved, and the anti-sintering ability of the catalyst can be improved, its heat stability can be increased, and the service life of the catalyst can be extended. Summary of the invention

[0004] The purpose of the present invention is to provide a catalyst for preparing low-carbon alcohols from synthesis gas and a preparation method and application thereof.

[0005] The main feature of the present invention is that the core-shell structure is used to prepare the active components of the catalyst, with CuO as the core and the outer layer covered with Cu-Zn alloy, which limits the growth of copper grains and increases the contact surface of Cu-Zn, thereby improving the activity of the catalyst; in addition, using aluminosilicate as a carrier of the catalyst has a larger specific surface area than using alumina alone as a carrier, which is more conducive to the dispersion of the active components, thereby improving the activity and stability of the catalyst.

[0006] The present invention discloses a catalyst for preparing low-carbon alcohols from synthesis gas, a preparation method and an application thereof, which are achieved through the following technical scheme: the catalyst comprises an active component Zn, a carrier and an auxiliary agent CuO, wherein the active component is a core-shell structure, the innermost part is CuO, and the outer part is covered with a Cu-Zn alloy, and the contents of ZnO, CuO and the carrier are 30%-40%, 10%-20% and 40%-60% by mass percentage of the catalyst.

[0007] Generally, the catalyst support is aluminosilicate.

[0008] The molar ratio of Al2O3:SiO2 in the aluminosilicate is 4-1:1.

[0009] The preparation method of the catalyst described in the present invention is as follows: Cu(NO3)2 solution and alkaline precipitant are co-precipitated in parallel to form an inner core of the active component, and a mixed solution of Cu(NO3)2 and Zn(NO3)2 and an alkaline precipitant are continuously added in parallel to allow the Cu-Zn alloy to continue to grow on the core of CuO to obtain a catalyst precursor, and silica sol, aluminum nitrate, and alkaline precipitant solution are added to the catalyst precursor to finally obtain a catalyst for preparing low-carbon alcohols from synthesis gas.

[0010] A typical preparation method of the catalyst of the present invention comprises the following steps:

[0011] 1) Under stirring conditions, the Cu(NO3)2 solution and the alkaline precipitant are co-precipitated to form the core of the active component;

[0012] 2) Continue to add the mixed solution of Cu(NO3)2 and Zn(NO3)2 and the alkaline precipitant into the reactor in step 1) in parallel, so that the Cu-Zn alloy continues to grow on the core of CuO, and the end point pH is controlled between 6.5-7.5;

[0013] 3) mixing silica sol, aluminum nitrate and alkaline precipitant solution, and adding the mixture to the catalyst precursor in step 2) for aging;

[0014] 4) washing, filtering, drying, granulating, and calcining the product in step 3), and finally adding water and graphite to form tablets.

[0015] Generally, the alkaline precipitant is one of NaOH, KOH, Na2CO3, and K2CO3.

[0016] The precipitation temperature in step 1) and step 2) is 55-75°C.

[0017] The aging temperature in step 3) is 65-85° C., and the aging time is 20-60 min.

[0018] The calcination temperature in step 4) is 300° C.-400° C., and the calcination time is 1-2 hours.

[0019] The invention also relates to the application of the catalyst, which can be used for the reaction of preparing low-carbon alcohols from synthesis gas.

[0020] Beneficial effects:

[0021] (1) The present invention adopts a core-shell method to prepare the active components of the catalyst, first generating a CuO core and then covering the outside with a layer of Cu-Zn alloy to increase the contact area of ​​Cu-Zn, thereby improving the activity of the catalyst;

[0022] (2) The present invention uses aluminosilicate as a carrier, and mixes silica sol and aluminum nitrate under alkaline conditions for slurrying, which not only promotes the stability of the carrier, but also makes the active components more evenly dispersed;

[0023] (3) The technical method adopted by the present invention is simple, conducive to industrial application and promotion, and has important social and economic significance. DETAILED DESCRIPTION

[0024] The following examples are only used to further explain the content and effects of the present invention, rather than to limit the present invention. Example 1

[0025] According to the content of ZnO, CuO and carrier being 30%, 10% and 60% respectively, 70.15g zinc nitrate, 23.44g copper nitrate, 19.2g 40% silica sol and 218.46g aluminum nitrate were weighed, and the copper nitrate was prepared into 250ml solution, 125ml copper nitrate solution was taken and co-precipitated with 250ml 0.5mol / l NaOH alkaline solution at 60°C, and then the zinc nitrate was prepared into 750ml solution, and mixed with the remaining 125ml copper nitrate solution, and continued to co-precipitate with 0.5mol / l NaOH alkaline solution until the pH value was 7; aluminum nitrate was added with 10g NaOH powder to prepare 100ml solution, and silica sol was added under stirring and mixed and slurried for 20min; finally, the carrier colloid was added to the catalyst precursor and aged at 70°C for 40min; the product was poured out, washed, filtered, dried, granulated, and calcined at 350°C for 2h, and finally water and graphite were added to form tablets to obtain catalyst C1. Example 2

[0026] According to the content of ZnO, CuO and carrier being 40%, 20% and 40% respectively, 93.53g zinc nitrate, 46.89g copper nitrate, 16.5g 40% silica sol and 140.58g aluminum nitrate were weighed, and the copper nitrate was prepared into 500ml solution, and 250ml copper nitrate solution was taken and co-precipitated with 500ml 0.5mol / l KOH alkaline solution at 70°C, and then the zinc nitrate was prepared into 1000ml solution, and mixed with the remaining 250ml copper nitrate solution, and continued to co-precipitate with 0.5mol / l KOH alkaline solution until the pH value was 7.5; aluminum nitrate was added with 5g KOH powder to prepare 100ml solution, and silica sol was added under stirring and mixed and slurried for 20min; finally, the carrier colloid was added to the catalyst precursor and aged at 80°C for 30min; the product was poured out, washed, filtered, dried, granulated, and roasted at 360°C for 2h, and finally water and graphite were added to form tablets to obtain catalyst C2. Example 3

[0027] According to the content of ZnO, CuO and carrier being 30%, 20% and 50% respectively, 70.15g zinc nitrate, 46.89g copper nitrate, 20.63g 40% silica sol and 175.73g aluminum nitrate were weighed, and the copper nitrate was prepared into 500ml solution, 250ml copper nitrate solution was taken and co-precipitated with 250ml 0.5mol / l Na2CO3 alkaline solution at 75℃, and then the zinc nitrate was prepared into 750ml solution and mixed with the remaining 250ml copper nitrate. The solution was mixed and co-precipitated with 0.5 mol / l Na2CO3 alkaline solution to a pH of 6.5; aluminum nitrate was added to 8 g Na2CO3 powder to make a 100 ml solution, and silica sol was added under stirring and mixed for 20 min; finally, the carrier colloid was added to the catalyst precursor and aged at 85°C for 20 min; the product was poured out, washed, filtered, dried, granulated, and calcined at 300°C for 2 h, and finally water and graphite were added to form a sheet to obtain catalyst C3. Example 4

[0028] According to the content of ZnO, CuO and carrier being 40%, 10% and 50% respectively, 93.53g zinc nitrate, 23.44g copper nitrate, 20.63g 40% silica sol and 175.73g aluminum nitrate were weighed. Copper nitrate was prepared into 250ml solution. 125ml copper nitrate solution was taken and co-precipitated with 125ml 0.5mol / l K2CO3 alkaline solution at 55℃. Then zinc nitrate was prepared into 1000ml solution and mixed with the remaining 150ml nitrate. The mixture was mixed with an acid copper solution and then co-precipitated with a 0.5 mol / l K2CO3 alkaline solution to a pH of 7; aluminum nitrate was added to 8 g K2CO3 powder to make a 100 ml solution, and silica sol was added under stirring and mixed for 20 min; finally, the carrier colloid was added to the catalyst precursor and aged at 65 °C for 20 min; the product was poured out, washed, filtered, dried, granulated, and calcined at 400 °C for 1 h, and finally water and graphite were added to form a sheet to obtain catalyst C4. Example 5

[0029] According to the content of ZnO, CuO and carrier being 35%, 15% and 50% respectively, 81.84g zinc nitrate, 35.17g copper nitrate, 46.5g 40% silica sol and 132.06g aluminum nitrate were weighed, and the copper nitrate was prepared into 375ml solution, 187.5ml copper nitrate solution was taken and co-precipitated with 375ml 0.5mol / l NaOH alkaline solution at 60°C, and then the zinc nitrate was prepared into 865ml solution, and mixed with the remaining 187.5ml copper nitrate solution, and continued to co-precipitate with 0.5mol / l NaOH alkaline solution until the pH value was 7; aluminum nitrate was added with 5g NaOH powder to prepare 100ml solution, and silica sol was added under stirring and mixed and slurried for 20min; finally, the carrier colloid was added to the catalyst precursor and aged at 70°C for 60min; the product was poured out, washed, filtered, dried, granulated, and roasted at 320°C for 2h, and finally water and graphite were added to form tablets to obtain catalyst C5. Example 6

[0030] The catalyst was applied to the synthesis gas to methanol reaction, using a micro-fixed bed continuous flow reactor, with a catalyst loading of 2mL and a particle size of 16-40 mesh. The catalyst was reduced in a low hydrogen (H2:N2=5:95) atmosphere, with a programmed temperature increase (20℃ / h) for 10 hours, and the temperature was raised to 230℃. The reducing gas was switched to the raw gas for activity testing. The activity test conditions were a reaction pressure of 8.0MP and a space velocity of 10000h -1, temperature 230℃, synthesis gas composition: H2:CO:CO2:N2 = 65:14:4:17 (v / v), after the reaction is stable for 2h, the liquid in the liquid collector is emptied and the timing is started. The collector is cooled by circulating water. After 2.5h, the collector liquid (crude methanol) is collected, weighed, and chromatographically analyzed. The measurement result is the initial activity. After the catalyst is heat treated for 5 hours under synthesis gas atmosphere, normal pressure, and 400 °C, it is restored to the above activity evaluation conditions. The measured activity result is the heat-resistant activity. The comparison sample is a methanol catalyst purchased on the market.

[0031] Table 1 Activity evaluation results

[0032] .

[0033] It can be seen from Table 1 that when the catalyst of the present invention is used in the synthesis gas to methanol reaction, the initial activity and the activity after heat resistance are significantly higher than those of the catalyst sample prepared by the traditional process, and can meet the industrial production conditions. Example 7

[0034] The catalyst was applied to the reaction of synthesizing isobutanol from synthesis gas. The original catalyst particle size was loaded into a reactor with an inner diameter of 26 mm, with a loading volume of 50 ml, and the catalyst performance was evaluated. Before the reaction, the catalyst was reduced for 12 hours at 400°C, 0.2MPa, and a 5% hydrogen concentration nitrogen and hydrogen atmosphere, and then the pressure was increased and switched to synthesis gas for reaction. The reaction conditions were: pressure 8.0MPa, temperature 380°C, synthesis gas GHSV = 3800h -1 , H2 / CO=3:1.

[0035] Table 2 Activity evaluation results

[0036] .

[0037] It can be seen from Table 2 that the catalyst of the present invention has good activity and isobutanol selectivity when used in the reaction of preparing isobutanol from synthesis gas, which shows that the catalyst of the present invention can be well applied to the reaction of preparing low-carbon alcohols from synthesis gas.

Claims

1. A catalyst for preparing low-carbon alcohols from synthesis gas, characterized in that: The catalyst is used for the reaction of synthesizing low-carbon alcohols from synthesis gas; the catalyst comprises an active component and a carrier, wherein the active component is a core-shell structure, the innermost part is CuO, and the outer part is covered with a Cu-Zn alloy, and the content of ZnO, CuO, and the carrier is 30%-40%, 10%-20%, and 40%-60% by mass percentage of the catalyst; the carrier of the catalyst is aluminosilicate; The preparation method of the catalyst comprises the following steps: 1) Under stirring conditions, the Cu(NO3)2 solution and the alkaline precipitant are co-precipitated to form the core of the active component; 2) Continue to add the mixed solution of Cu(NO3)2 and Zn(NO3)2 and the alkaline precipitant into the reactor in step 1) in parallel, so that the Cu-Zn alloy continues to grow on the core of CuO, and the end point pH is controlled between 6.5-7.5; 3) mixing silica sol, aluminum nitrate and alkaline precipitant solution, and adding the mixture to the catalyst precursor in step 2) for aging; 4) washing, filtering, drying, granulating, and calcining the product in step 3), and finally adding water and graphite to form tablets, and finally reducing the product to obtain a catalyst for preparing low-carbon alcohols from synthesis gas.

2. The catalyst according to claim 1, characterized in that The molar ratio of Al2O3:SiO2 in the aluminosilicate is 4-1:

1.

3. The catalyst according to claim 1, characterized in that The alkaline precipitant is one of NaOH, KOH, Na2CO3, and K2CO3.

4. The catalyst according to claim 1, characterized in that The precipitation temperature in step 1) and step 2) is 55-75°C.

5. The catalyst according to claim 1, characterized in that The aging temperature in step 3) is 65-85°C, and the aging time is 20-60 minutes.

6. The catalyst according to claim 1, characterized in that The calcination temperature in step 4) is 300°C-400°C, and the calcination time is 1-2h.