PREPARATION METHOD OF DOPED ZnO CATALYST AND SYNTHESIS METHOD OF HIGHER ALCOHOL USING SAME

Abstract

The present disclosure provides a preparation method of a doped ZnO catalyst. The preparation method includes the following steps: mixing a precipitant and a first solvent to form a first solution having 1 mol/L to 5 mol/L of the precipitant by concentration; mixing one of a Cu salt or a Ga salt, a Zn salt, and a second solvent to form a second solution having Cu and Zn at a molar ratio of less than 0.05:1 and Ga and Zn at a molar ratio of less than 0.1:1; subjecting the first solution and the second solution to precipitation or hydrolysis at 50° C. to 90° C. to obtain a precipitate, and washing and drying the precipitate to obtain a precursor sample; and conducting calcination on the precursor sample at 300° C. to 500° C. for 3 h to 5 h to obtain a Cu-doped ZnO catalyst or a Ga-doped ZnO catalyst.

Claims

1. A preparation method of a doped ZnO catalyst, wherein the doped ZnO catalyst is used to synthesize a higher alcohol by hydrogenation of CO on a fixed bed; and the preparation method comprises the following steps: mixing a precipitant and a first solvent to form a first solution having 1 mol/L to 5 mol/L of the precipitant by concentration; mixing one of a Cu salt or a Ga salt, a Zn salt, and a second solvent to form a second solution having Cu and Zn at a molar ratio of less than 0.05:1 and Ga and Zn at a molar ratio of less than 0.1:1; subjecting the first solution and the second solution to precipitation or hydrolysis at 50° C. to 90° C. to obtain a precipitate, and washing and drying the precipitate to obtain a precursor sample; and conducting calcination on the precursor sample at 300° C. to 500° C. for 3 h to 5 h to obtain a Cu-doped ZnO catalyst or a Ga-doped ZnO catalyst.

2. The preparation method of a doped ZnO catalyst according to claim 1, wherein the precipitant is any one or a combination of two or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, ammonia water, ammonium carbonate, urea, and ammonium bicarbonate.

3. The preparation method of a doped ZnO catalyst according to claim 2, wherein the Cu salt is any one or a combination of two or more selected from the group consisting of copper nitrate, copper sulfate, copper chloride, and copper citrate; and the Ga salt is any one or a combination of two or more selected from the group consisting of gallium nitrate, gallium sulfate, gallium acetate, and gallium chloride.

4. The preparation method of a doped ZnO catalyst according to claim 3, wherein Cu and Zn have a molar ratio of (0.01-0.04):1, and Ga and Zn have a molar ratio of (0.01-0.1):1.

5. The preparation method of a doped ZnO catalyst according to claim 4, wherein the Zn salt is any one or a combination of two or more selected from the group consisting of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride.

6. The preparation method of a doped ZnO catalyst according to claim 5, wherein at least one of the first solvent and the second solvent comprises deionized water.

7. The preparation method of a doped ZnO catalyst according to claim 1, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

8. The preparation method of a doped ZnO catalyst according to claim 2, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

9. The preparation method of a doped ZnO catalyst according to claim 3, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

10. The preparation method of a doped ZnO catalyst according to claim 4, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

11. The preparation method of a doped ZnO catalyst according to claim 5, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

12. The preparation method of a doped ZnO catalyst according to claim 6, comprising the following steps: dissolving the precipitant in the first solvent, and stirring in a magnetic stirrer to form the first solution; and dissolving one of the Cu salt or the Ga salt, and the Zn salt in the second solvent, and stirring in the magnetic stirrer to form the second solution.

13. The preparation method of a doped ZnO catalyst according to claim 7, wherein the doped ZnO catalyst is prepared by co-precipitation or hydrothermal synthesis.

14. A synthesis method of a higher alcohol using a doped ZnO catalyst, wherein the doped ZnO catalyst is prepared by the preparation method according to claim 1; and the synthesis method of a higher alcohol using the doped ZnO catalyst by hydrogenation of CO on a fixed bed comprises the following steps: subjecting the doped ZnO catalyst to grinding, tabletting, crushing, and sieving, packing in the fixed bed while fixing in a position with a filler, conducting reduction on the doped ZnO catalyst, and conducting the hydrogenation of CO on the fixed bed at 4 MPa to 6 MPa and 200° C. to 400° C. with a gas hourly space velocity (GHSV) of 3,000 h.sup.−1 to 9,000 h.sup.−1 and a H.sub.2/CO of 1 to 2.

15. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 14, wherein the precipitant is any one or a combination of two or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, ammonia water, ammonium carbonate, urea, and ammonium bicarbonate.

16. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 15, wherein the Cu salt is any one or a combination of two or more selected from the group consisting of copper nitrate, copper sulfate, copper chloride, and copper citrate; and the Ga salt is any one or a combination of two or more selected from the group consisting of gallium nitrate, gallium sulfate, gallium acetate, and gallium chloride.

17. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 16, wherein Cu and Zn have a molar ratio of (0.01-0.04):1, and Ga and Zn have a molar ratio of (0.01-0.1):1.

18. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 17, wherein the Zn salt is any one or a combination of two or more selected from the group consisting of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride.

19. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 18, wherein at least one of the first solvent and the second solvent comprises deionized water.

20. The synthesis method of a higher alcohol using a doped ZnO catalyst according to claim 14, wherein the doped ZnO catalyst is reduced in a hydrogen atmosphere; and after a stable catalytic reaction, the doped ZnO catalyst has a CO conversion rate of 10% to 70%, and the higher alcohol accounts for greater than 40% of an obtained product.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solutions of the present disclosure are described in further detail below with reference to examples. The following description of the embodiments of the present disclosure with reference to the accompanying drawings is intended to explain the general conception of the present disclosure, but should not be construed as a limitation on the present disclosure.

[0021] In the background, the shortcomings of Cu-doped ZnO catalyst are discussed. One is that Cu has a doping amount of not less than 5 wt %, and its catalytic product is mainly methanol, while it is hoped that more higher alcohols can be obtained; two is that in order to obtain more higher alcohols, at least one Fischer-Tropsch element is generally used on the basis of a zinc-copper component.

[0022] In view of this, the present disclosure provides a preparation method of a doped ZnO catalyst, where the doped ZnO catalyst is used to synthesize a higher alcohol by hydrogenation of CO on a fixed bed; and the preparation method includes the following steps:

[0023] mixing a precipitant and a first solvent to form a first solution having 1 mol/L to 5 mol/L of the precipitant by concentration;

[0024] mixing one of a Cu salt or a Ga salt, a Zn salt, and a second solvent to form a second solution having Cu and Zn at a molar ratio of less than 0.05:1 and Ga and Zn at a molar ratio of less than 0.1:1;

[0025] subjecting the first solution and the second solution to precipitation or hydrolysis at 50° C. to 90° C. to obtain a precipitate, and washing and drying the precipitate to obtain a precursor sample; and

[0026] conducting calcination on the precursor sample at 300° C. to 500° C. for 3 h to 5 h to obtain a Cu-doped ZnO catalyst or a Ga-doped ZnO catalyst.

[0027] In an example, the precipitant is any one or a combination of two or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, ammonia water, ammonium carbonate, urea, and ammonium bicarbonate.

[0028] In another example, the Cu salt is any one or a combination of two or more selected from the group consisting of copper nitrate, copper sulfate, copper chloride, and copper citrate; or the Ga salt is any one or a combination of two or more selected from the group consisting of gallium nitrate, gallium sulfate, gallium acetate, and gallium chloride. Optionally, the Zn salt is any one or a combination of two or more selected from the group consisting of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride. At least one of the first solvent and the second solvent includes deionized water.

[0029] It should be understood that the precipitant, the Cu salt, the Ga salt, and the Zn salt only show some common examples and are not exhaustive examples.

[0030] In a further example, Cu and Zn have a molar ratio of (0.01-0.04):1 (such as 0.01:1, 0.02:1, 0.03:1, or 0.04:1), and Ga and Zn have a molar ratio of (0.01-0.1):1 (such as 0.01:1, 0.03:1, 0.05:1, 0.07:1, or 0.1:1).

[0031] In some examples, the precipitant is dissolved in the first solvent, and stirred, for example, in a magnetic stirrer, to form the first solution; and one of the Cu salt or the Ga salt, and the Zn salt are dissolved in the second solvent, and stirred in the magnetic stirrer to form the second solution.

[0032] It should be understood that the preparation method includes co-precipitation or hydrothermal synthesis, and of course any other known suitable method can also be used.

[0033] In addition, the present disclosure further provides a synthesis method of a higher alcohol using a doped ZnO catalyst, where the doped ZnO catalyst is prepared by the preparation method above; and the synthesis method of a higher alcohol using the doped ZnO catalyst by hydrogenation of CO on a fixed bed includes the following steps:

[0034] subjecting the doped ZnO catalyst to grinding, tabletting, crushing, and sieving, packing in the fixed bed while fixing in a position with a filler, conducting reduction in a hydrogen atmosphere on the doped ZnO catalyst, and conducting the hydrogenation of CO on the fixed bed at 4 MPa to 6 MPa and 200° C. to 400° C. (optionally 250° C. to 320° C.) with a GHSV of 3,000 h.sup.−1 to 9,000 h.sup.−1 (optionally 5,000 h.sup.−1 to 8,000 h.sup.−1) and a H.sub.2/CO of 1 to 2.

[0035] In some examples, after a stable catalytic reaction, the doped ZnO catalyst has a CO conversion rate of 10% to 70%, and the higher alcohol accounts for greater than 40% of an obtained product.

[0036] The following only shows a part of the examples of the present disclosure, which are only used for exemplary illustration; those skilled in the art can understand other feasible examples of the present disclosure, which will not be repeated herein.

Example 1

[0037] Zinc nitrate was dissolved in 200 mL of deionized water, and copper nitrate was added; and a resulting solution was subjected to magnetic stirring for 20 min to form a copper-zinc salt solution with n (Cu) and n (Zn) at a ratio of 0.01:1;

[0038] 1.6 M of sodium carbonate was dissolved in 200 mL of the deionized water, and subjected to magnetic stirring for 20 min; and a resulting solution was heated in a water bath to 20° C. to form a sodium carbonate solution;

[0039] the sodium carbonate solution and the copper-zinc salt solution were added dropwise to a reaction vessel (such as a three-necked flask) while maintaining a pH value of 6.5, and continuously stirred to form a uniform and stable precipitate at 65° C.; and the precipitate was aged (such as for 6 h), and then subjected to suction filtration and washing to obtain a treated precipitate;

[0040] the treated precipitate was dried at 100° C. overnight to obtain a precursor sample; and the precursor sample was subjected to calcination in a muffle furnace at 330° C. for 3 h to obtain a Cu-doped ZnO catalyst; and

[0041] the Cu-doped ZnO catalyst was subjected to grinding, tabletting, crushing, and sieving to obtain catalyst particles of 40 mesh to 60 mesh, and the Cu-doped ZnO catalyst particles were packed into a fixed bed reactor and fixed with a filler; the Cu-doped ZnO catalyst was reduced under a H.sub.2 atmosphere, and then reacted at 4 MPa and 300° C. with a GHSV of 6,000 h.sup.−1 and a H.sub.2/CO of 1 for activity evaluation. The reactivity evaluation results were shown in Table 1, and a proportion of the higher alcohol was a percentage of a C2+ alcohol in an alcohol product.

Example 2

[0042] Zinc nitrate was dissolved in 200 mL of deionized water, and copper nitrate was added; and a resulting solution was subjected to magnetic stirring for 20 min to form a copper-zinc salt solution with n (Cu) and n (Zn) at a ratio of 0.04:1;

[0043] 3 mol/L of urea was dissolved in 200 mL of the deionized water, and subjected to magnetic stirring for 20 min; and a resulting solution was heated in a water bath to 20° C. to form a urea solution;

[0044] the copper-zinc salt solution and the urea solution were mixed to form a uniform and stable solution, heated in water bath at 90° C. for 8 h, and subjected to suction filtration and washing to obtain a precipitate;

[0045] the treated precipitate was dried at 100° C. overnight to obtain a precursor sample; and the precursor sample was subjected to calcination in a muffle furnace at 330° C. for 3 h to obtain a Cu-doped ZnO catalyst; and

[0046] the Cu-doped ZnO catalyst was subjected to grinding, tabletting, crushing, and sieving to obtain catalyst particles of 40 mesh to 60 mesh, and the Cu-doped ZnO catalyst particles were packed into a fixed bed reactor and fixed with a filler; the Cu-doped ZnO catalyst was reduced under a H.sub.2 atmosphere, and then reacted at 4 MPa and 290° C. with a GHSV of 6,000 h.sup.−1 and a H.sub.2/CO of 2 for activity evaluation. The reactivity evaluation results were shown in Table 1, and a proportion of the higher alcohol was a percentage of a C2+ alcohol in an alcohol product.

Example 3

[0047] Zinc nitrate was dissolved in 200 mL of deionized water, and gallium nitrate was added; and a resulting solution was subjected to magnetic stirring for 20 min to form a gallium-zinc salt solution with n (Ga) and n (Zn) at a ratio of 0.01:1;

[0048] 1.6 M of sodium carbonate was dissolved in 200 mL of the deionized water, and subjected to magnetic stirring for 20 min; and a resulting solution was heated in a water bath to 20° C. to form a sodium carbonate solution;

[0049] the sodium carbonate solution and the gallium-zinc salt solution were added dropwise to a three-necked flask while maintaining a pH value of 6.5, and continuously stirred to form a uniform and stable precipitate; and the precipitate was aged (such as for 6 h), and then subjected to suction filtration and washing to obtain a treated precipitate;

[0050] the treated precipitate was dried at 100° C. overnight to obtain a precursor sample; and the precursor sample was subjected to calcination in a muffle furnace at 330° C. for 3 h to obtain a Ga-doped ZnO catalyst; and

[0051] the Ga-doped ZnO catalyst was subjected to grinding, tabletting, crushing, and sieving to obtain catalyst particles of 40 mesh to 60 mesh, and the Ga-doped ZnO catalyst particles were packed into a fixed bed reactor and fixed with a filler; the Ga-doped ZnO catalyst was reduced under a H.sub.2 atmosphere, and then reacted at 4 MPa and 280° C. with a GHSV of 6,000 h.sup.−1 and a H.sub.2/CO of 2 for activity evaluation. The reactivity evaluation results were shown in Table 1, and a proportion of the higher alcohol was a percentage of a C2+ alcohol in an alcohol product.

Example 4

[0052] Zinc nitrate was dissolved in 200 mL of deionized water, and gallium nitrate was added; and a resulting solution was subjected to magnetic stirring for 20 min to form a gallium-zinc salt solution with n (Ga) and n (Zn) at a ratio of 0.04:1;

[0053] 3 mol/L of urea was dissolved in 200 mL of the deionized water, and subjected to magnetic stirring for 20 min; and a resulting solution was heated in a water bath to 20° C. to form a urea solution;

[0054] the gallium-zinc salt solution and the urea solution were mixed to form a uniform and stable solution, heated in water bath at 90° C. for 8 h, and then subjected to suction filtration and washing to obtain a treated precipitate; the treated precipitate was dried at 100° C. overnight to obtain a precursor sample; and the precursor sample was subjected to calcination in a muffle furnace at 330° C. for 3 h to obtain a Ga-doped ZnO catalyst; and

[0055] the Ga-doped ZnO catalyst was subjected to grinding, tabletting, crushing, and sieving to obtain catalyst particles of 40 mesh to 60 mesh, and the Ga-doped ZnO catalyst particles were packed into a fixed bed reactor and fixed with a filler; the Ga-doped ZnO catalyst was reduced under a H.sub.2 atmosphere, and then reacted at 4 MPa and 300° C. with a GHSV of 8,000 h.sup.−1 and a H.sub.2/CO of 1 for activity evaluation. The reactivity evaluation results were shown in Table 1, and a proportion of the higher alcohol was a percentage of a C2+ alcohol in an alcohol product.

TABLE-US-00001 TABLE 1 Evaluation results of reactivity of catalysts in Examples 1 to 4 CO conversion Proportion of Example rate (%) higher alcohol (%) 1 62.84 46.08 2 18.06 69.89 3 15.75 65.78 4 16.23 55.31

[0056] In the examples of the present disclosure, at least one advantage described in the following aspects are achieved: the ZnO is used as a main component of the catalyst, and a small amount of copper or gallium is doped to enhance an interaction between the ZnO or the Cu or Ga;

[0057] the Cu-doped ZnO catalyst has an extremely low metal content (<0.05 mol), and the Ga-doped ZnO catalyst has a gallium content of less than 0.1 mol, without any additives and Fischer-Tropsch elements;

[0058] the Cu-doped ZnO catalyst or the Ga-doped ZnO catalyst exhibits a desirable activity and an excellent proportion of the higher alcohols in hydrogenation of CO; and

[0059] the Cu-doped ZnO catalyst or the Ga-doped ZnO catalyst is prepared by co-precipitation or hydrothermal synthesis.

[0060] Although some examples of the present general inventive concept have been shown and described, those of ordinary skill in the art will appreciate that changes may be made to these examples without departing from the principles and spirit of the present general inventive concept. The scope of the present disclosure is defined by the claims and their equivalents.