CN108114724A - The preparation method of carbon monoxide water-gas shift low temperature catalyst - Google Patents

Abstract

The present invention discloses a kind of preparation method of carbon monoxide water-gas shift low temperature catalyst, belongs to catalysis technical field.This method particular content is：Precipitating reagent is added drop-wise to containing zinc salt and carrier γ Al₂O₃Solution in prepare zinc hydroxide suspension.Then precipitant solution and copper salt solution are added drop-wise to simultaneously in zinc hydroxide suspension, adjust the pH value of solution and are stirred continuously, using filtering, washing, dry, roasting, obtain Cu Zn/ γ Al₂O₃Catalyst；Cu contents are 20 40wt%, and copper zinc molar ratio is 1:1.Water gas shift reation is carried out in gas is typically reformed using catalyst prepared by this method, there is high activity and stability, show reactivity more higher than catalyst prepared by traditional co-precipitation method.

Description

Preparation method of carbon monoxide water vapor shift low temperature catalyst

Technical field:

The invention belongs to the technical field of catalysis, and in particular relates to a preparation method of a carbon monoxide water vapor shift low-temperature catalyst.

Background technique:

With the advancement of science and technology and the growth of world population, the problem of energy shortage has attracted more and more attention. At present, the demand for fossil energy is increasing day by day while the reserve is decreasing day by day. The development of new sustainable energy sources has become one of the most concerned issues in today's society. As a new type of energy, hydrogen energy has the advantages of cleanness and no pollution, high combustion calorific value, good thermal conductivity, and recyclable combustion products. Therefore, it has become the most likely new energy source to replace today's fossil energy in the future. Among them, hydrogen production by reforming compounds such as methanol and natural gas as a hydrogen source for fuel cells has always attracted the attention of researchers. However, the reformed gas usually contains 5%-20% CO, which will cause poisoning of the platinum electrode of the proton exchange membrane fuel cell, and then severely degrade the performance of the cell. Therefore, it is necessary to reduce the CO content in the reformed gas, for example by means of the water-steam shift reaction (CO+H ₂ O=CO ₂ +H ₂ ). The water vapor shift reaction produces the same volume of hydrogen as it removes CO. In addition, the water vapor shift reaction has been widely used in the synthesis of ammonia, synthesis of methanol, gasoline and the adjustment of the carbon-hydrogen ratio in the production of synthetic gasoline and in the city gas industry. Commercial shift catalysts are mainly classified into high temperature shift catalysts, low temperature shift catalysts and wide temperature shift catalysts. Low-temperature shift catalysts are generally copper-zinc catalysts. This type of catalyst has high reactivity, but has disadvantages such as poor thermal stability, poor selectivity, and easy contact with air. At present, catalysts are mainly prepared by co-precipitation method. Many factors in the preparation process will lead to low reproducibility of catalysts. For example, common factors include pH value, precipitant, precipitation temperature, aging time, etc. In view of the importance of the water vapor change reaction in industrial processes and the application prospect of purifying raw gas hydrogen on fuel cell electric vehicles, countries around the world have carried out extensive research mainly on the production process and preparation of catalysts in order to achieve high synthesis activity and stability. Catalyst with good performance and high reproducibility. Aiming at the shortcomings of existing catalysts, a Chinese patent (CN201510678685.X) synthesized a nanocomposite Cu/ZnAl ₂ O ₄ low-temperature water-gas shift catalyst with good low-temperature activity, heat resistance stability and long-term stability. It can be seen that the development of a water vapor shift low-temperature catalyst with high activity and good stability has become one of the keys for this type of catalyst to be suitable for a wider range of reaction systems.

Invention content:

The purpose of the present invention is to provide a method for preparing a nano Cu-Zn/γ-Al ₂ O ₃ low-temperature water vapor shift catalyst with good low-temperature activity and stability.

The preparation method of the carbon monoxide water vapor shift low-temperature catalyst provided by the present invention, the active components of the catalyst are Cu and Zn, the carrier is γ-Al ₂ O ₃ , the Cu content is 20-40wt%, and the copper-zinc molar ratio is 1:1 ; Precipitate is prepared by distribution precipitation method, and then through suction filtration, washing, drying and roasting, Cu-Zn/γ-Al ₂ O ₃ catalyst is obtained; the specific steps of the preparation method are as follows:

(1) Prepare a certain concentration of precipitant solution, add it dropwise to the solution containing zinc salt and carrier γ-Al ₂ O ₃ and keep stirring until the pH value is 9 to obtain a zinc hydroxide suspension. After the titration is completed, continue Stir for 40min;

(2) prepare a certain concentration of copper salt solution, slowly add dropwise the precipitant solution and the copper salt solution described in step (1) to the zinc hydroxide suspension obtained in step (1) simultaneously, continuously Stir and keep the pH value at 8. After the copper salt is added dropwise, continue to add the precipitant solution dropwise until the pH value is 9. Continue to stir the obtained suspension in a 60°C water bath for 2-4h, then suction filter, and use Wash with distilled water until the pH value is 7, and dry the solid in an oven at 80°C for 12-24 hours to obtain the precipitate precursor;

(3) Calcining the precipitate precursor at 400° C. for 2 h in an oxidative atmosphere to prepare the carbon monoxide water vapor shift low-temperature catalyst Cu—Zn/γ—Al ₂ O ₃ .

The copper salt is Cu(NO ₃ ) ₂ ·3H ₂ O, CuSO ₄ ·5H ₂ O or CuCl ₂ ·2H ₂ O, the concentration is 0.06-0.15mol/L; the zinc salt is Zn(NO ₃ ) ₂ ·6H ₂ O, ZnSO ₄ ·7H ₂ O or ZnCl ₂ , the concentration is 0.05～0.12mol/L; the precipitation agent is any one of ammonia water, sodium carbonate, sodium hydroxide, and sodium bicarbonate, the concentration is 0.4mol/L; the oxidizing atmosphere is any one of air, oxygen or a mixture of oxygen and nitrogen

The specific catalyst evaluation method used in the present invention is as follows: the evaluation device adopts a fixed-bed reactor; the raw material gas is 3% CO, 12% H ₂ O, and N ₂ balance. The loading amount of the catalyst is 0.06g; the reaction temperature is 150-300°C, and the space velocity is 30000mL/(g·h). The reaction is carried out under normal pressure, and the gas is detected online by a gas chromatograph after passing through the catalyst.

The present invention has the following technical characteristics:

1. The Cu-Zn/γ-Al ₂ O ₃ catalyst of the present invention has a nanocomposite structure, and the active components are CuO and ZnO.

2. Compared with the catalyst prepared by the traditional co-precipitation method, the Cu-Zn/γ-Al ₂ O ₃ catalyst of the present invention has good low-temperature activity and stability for the water vapor shift reaction, and has a good application prospect.

Description of drawings:

Figure 1 shows the catalytic activity of the Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the distribution precipitation method and the Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the co-precipitation method in the water vapor shift reaction of the present invention.

Figure 2 shows the stability of the Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the distribution precipitation method and the Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the co-precipitation method in the water vapor shift reaction of the present invention.

Detailed ways:

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

Example 1:

(1) Weigh 4.242g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 1.175g of Zn(NO ₃ ) ₂ ·6H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve, and then add 0.103g of industrial grade γ-Al ₂ O ₃ . Slowly add the Na ₂ CO ₃ solution dropwise to the Zn salt-containing solution at room temperature, and keep stirring until the end point is pH=9, then stop the dropwise addition to obtain a zinc hydroxide suspension. Continue to stir for 40 min after the dropwise addition.

(2) Weigh 0.947g Cu(NO ₃ ) ₂ ·3H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve. Slowly add the precipitating agent Na ₂ CO ₃ solution and the above-mentioned Cu salt solution into the zinc hydroxide suspension at the same time, keep stirring during the simultaneous dropping, and control the pH to about 8. After the copper salt is added dropwise, continue to add the precipitant Na ₂ CO ₃ solution dropwise until the pH is 9. The resulting suspension was continuously stirred in a water bath at 60°C for 2 h, then suction-filtered, and washed with distilled water until the pH was 7. The solid was dried in an oven at 80° C. for 12-24 hours to obtain the precipitate precursor. The precipitate precursor was calcined at 400° C. for 2 hours in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (SP) catalyst.

Example 2:

(1) Weigh 4.247g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 1.155g of ZnSO ₄ ·7H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve, and then add 0.105g of industrial grade γ-Al ₂ O ₃ . The Na ₂ CO ₃ solution was slowly added dropwise to the above Zn salt-containing solution at room temperature, and the stirring was continued until the end point was pH=9, and the dropwise addition was stopped to obtain a zinc hydroxide suspension. Continue to stir for 40 min after the dropwise addition.

(2) Weigh 0.945g of Cu(NO ₃ ) ₂ ·3H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve. Slowly add the precipitating agent Na ₂ CO ₃ solution and the above-mentioned Cu salt solution into the zinc hydroxide suspension at the same time, keep stirring during the simultaneous dropping, and control the pH to about 8. After the copper salt is added dropwise, continue to add the precipitant Na ₂ CO ₃ solution dropwise until the pH is 9. The resulting suspension was continuously stirred in a water bath at 60°C for 2 h, then suction-filtered, and washed with distilled water until the pH was 7. The solid was dried in an oven at 80° C. for 12-24 hours to obtain the precipitate precursor. The precipitate precursor was calcined at 400° C. for 2 hours in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (SP) catalyst.

Example 3:

(1) Weigh 4.243g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 0.688g of ZnCl ₂ ·2H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve, and then add 0.102g of industrial grade γ-Al ₂ O ₃ . The Na ₂ CO ₃ solution was slowly added dropwise to the above Zn salt-containing solution at room temperature, and the stirring was continued until the end point was pH=9, and the dropwise addition was stopped to obtain a zinc hydroxide suspension. Continue to stir for 40 min after the dropwise addition.

(2) Weigh 0.941g of Cu(NO ₃ ) ₂ ·3H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve. Slowly add the precipitating agent Na ₂ CO ₃ solution and the above-mentioned Cu salt solution into the zinc hydroxide suspension at the same time, keep stirring during the simultaneous dropping, and control the pH to about 8. After the copper salt is added dropwise, continue to add the precipitant Na ₂ CO ₃ solution dropwise until the pH is 9. The resulting suspension was continuously stirred in a water bath at 60°C for 2 h, then suction-filtered, and washed with distilled water until the pH was 7. The solid was dried in an oven at 80° C. for 12-24 hours to obtain the precipitate precursor. The precipitate precursor was calcined at 400° C. for 2 hours in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (SP) catalyst.

Example 4:

(1) Weigh 4.242g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 1.178g of Zn(NO ₃ ) ₂ ·6H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve, and then add 0.103g of industrial grade γ-Al ₂ O ₃ . The Na ₂ CO ₃ solution was slowly added dropwise to the above Zn salt-containing solution at room temperature, and the stirring was continued until the end point was pH=9, and the dropwise addition was stopped to obtain a zinc hydroxide suspension. Continue to stir for 40 min after the dropwise addition.

(2) Weigh 1.003g of CuSO ₄ ·3H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve. Slowly add the precipitating agent Na ₂ CO ₃ solution and the above-mentioned Cu salt solution into the zinc hydroxide suspension at the same time, keep stirring during the simultaneous dropping, and control the pH to about 8. After the copper salt is added dropwise, continue to add the precipitant Na ₂ CO ₃ solution dropwise until the pH is 9. The resulting suspension was continuously stirred in a water bath at 60°C for 2 h, then suction-filtered, and washed with distilled water until the pH was 7. The solid was dried in an oven at 80° C. for 12-24 hours to obtain the precipitate precursor. The precipitate precursor was calcined at 400° C. for 2 hours in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (SP) catalyst.

Example 5:

(1) Weigh 4.240g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 1.172g of Zn(NO ₃ ) ₂ ·6H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve, and then add 0.103g of industrial grade γ-Al ₂ O ₃ . The Na ₂ CO ₃ solution was slowly added dropwise to the above Zn salt-containing solution at room temperature, and the stirring was continued until the end point was pH=9, and the dropwise addition was stopped to obtain a zinc hydroxide suspension. Continue to stir for 40 min after the dropwise addition.

(2) Weigh 0.535g CuCl ₂ ·3H ₂ O into a 100ml beaker, add 50ml of distilled water to dissolve. Slowly add the precipitating agent Na ₂ CO ₃ solution and the above-mentioned Cu salt solution into the zinc hydroxide suspension at the same time, keep stirring during the simultaneous dropping, and control the pH to about 8. After the copper salt is added dropwise, continue to add the precipitant Na ₂ CO ₃ solution dropwise until the pH is 9. The resulting suspension was continuously stirred in a water bath at 60°C for 2 h, then suction-filtered, and washed with distilled water until the pH was 7. The solid was dried in an oven at 80° C. for 12-24 hours to obtain the precipitate precursor. The precipitate precursor was calcined at 400° C. for 2 hours in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (SP) catalyst.

Embodiment 6:

Weigh 4.244g Na ₂ CO ₃ into a 100ml volumetric flask, add distilled water, shake well and set volume, and use it as a precipitant for later use. Weigh 1.168g Zn(NO ₃ ) ₂ 6H ₂ O and 0.946g Cu(NO ₃ ) ₂ 3H ₂ O respectively into a 100ml beaker, add 50ml distilled water to dissolve, then add 0.106g industrial grade γ-Al ₂ O ₃ . After ultrasonic dispersion is uniform, Na ₂ CO ₃ solution is slowly added dropwise to the above-mentioned solution containing Cu salt and Zn salt at room temperature, and the dropwise addition is stopped when the end point is pH=9 while stirring continuously. After the titration is completed, heat and stir in a water bath at 60° C. for 4 h, then filter with suction and wash with distilled water until the pH is 7. The solid is dried in an oven at 80°C for 12-24h, and then calcined at 400°C for 2h in an air atmosphere to obtain a Cu-Zn/γ-Al ₂ O ₃ (CP) catalyst.

Embodiment 7:

The catalyst prepared above was sieved, and 0.06 g of the catalyst with a particle size of 20-40 mesh was weighed, and the water vapor shift reaction performance test was performed on a fixed-bed quartz tube reactor. The inner diameter of the quartz tube is 8mm, and the reaction gas space velocity is 30000mL/(g·h). The composition of the reaction gas by volume ratio is: 3% CO, 12% H ₂ O, 85% N ₂ . Before the reaction performance test, the sample was raised from room temperature to 400°C in an air atmosphere of 30ml/min and kept for 2h. Then switch to Ar atmosphere to cool the sample. Cool to below 150°C and then switch to reaction gas for reaction. During the reaction process, the temperature was programmed to increase from 150°C to 300°C at a rate of 1°C/min. During this period, Fuli 9790 gas chromatograph was used for online detection, TDX-01 column, and TCD detector. Catalyst performance test results are shown in Figure 1. The water vapor shift reaction activity of the Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the distributed precipitation method is significantly better than that of the catalyst prepared by the traditional co-precipitation method at low temperature. The reaction temperature was fixed at 220°C to carry out the stability test of the catalyst, see Figure 2. The Cu-Zn/γ-Al ₂ O ₃ catalyst prepared by the distributed precipitation method always maintained a CO conversion rate of 90% in the 50h stability test. The catalyst prepared by the traditional co-precipitation method has a CO conversion rate of about 46% at the beginning of the reaction, and then increases to about 60%, and can also maintain a stability close to 50h.

Claims (2)

1. a kind of preparation method of carbon monoxide water-gas shift low temperature catalyst, it is characterised in that the catalyst activity component is Cu, Zn, carrier are γ-Al₂O₃, Cu contents are 20-40wt%, and copper zinc molar ratio is 1:1；Precipitation is prepared by being distributed the precipitation method Using filtering, washing, dry, roasting, Cu-Zn/ γ-Al are made in object₂O₃Catalyst；The preparation method is as follows：

(1) certain density precipitant solution is prepared, is added dropwise to containing zinc salt and carrier γ-Al₂O₃Solution in and constantly Stirring to pH value is 9, obtains zinc hydroxide suspension, continues to stir 40min after the completion of titration；

(2) certain density copper salt solution is prepared, by step (1) precipitant solution and the copper salt solution while slowly It is added drop-wise in the zinc hydroxide suspension that step (1) obtains, it is 8 to be stirred continuously and keep pH value, when mantoquita is added dropwise After to continue to be added dropwise the precipitant solution to pH value be 9, obtained suspension continues to stir 2-4h in 60 DEG C of water-baths, then takes out Filter, it is 7 to be washed with distilled water to pH value, and solid dries 12-24h to get sediment presoma in 80 DEG C of baking ovens；

(3) the sediment presoma is calcined into 2h at 400 DEG C in oxidizing atmosphere, the carbon monoxide water-gas shift is made Low temperature catalyst Cu-Zn/ γ-Al₂O₃。

2. preparation method according to claim 1, it is characterised in that the mantoquita is Cu (NO₃)₂·3H₂O、CuSO₄· 5H₂O or CuCl₂·2H₂O, concentration are 0.06~0.15mol/L；The zinc salt is Zn (NO₃)₂·6H₂O、ZnSO₄·7H₂O or ZnCl₂, concentration is 0.05~0.12mol/L；The precipitating reagent is appointing in ammonium hydroxide, sodium carbonate, sodium hydroxide and sodium acid carbonate Meaning is a kind of, concentration 0.4mol/L；The oxidizing atmosphere is air, oxygen or any one of oxygen and nitrogen mixture.