Preparation method and application of CeO2 loaded CuO / ZnO / Al2O3 catalyst

Abstract

The invention provides a preparation method of a morphology-controllable CeO2-loaded CuO / ZnO / Al2O3 catalyst, which comprises the following steps: slowly dropwise adding a sodium hydroxide solution into a cerium salt solution while stirring to obtain a suspension; placing the suspension in a reaction kettle, performing hydrothermal treatment at different temperatures, drying, and roasting to obtain CeO2; and immersing the CeO2 powder into a solution containing a copper salt, a zinc salt and an aluminum salt, and then drying and roasting the obtained powder to obtain the CeO2 loaded CuO / ZnO / Al2O3 catalyst. The invention also provides an application of the catalyst, and the catalyst is applied to catalysis of alcohol reforming for hydrogen production.

Description

Technical Field

[0001] The invention belongs to the technical field of alcohol reforming hydrogen production, and specifically relates to a preparation method and application of a morphology-controllable CeO2-loaded CuO / ZnO / Al2O3 catalyst. Background Art

[0002] Alcohols play an important role in the field of real-time hydrogen production due to their simple molecular structure, high energy density, and mild conversion conditions. With the expansion of the scale of alcohol hydrogen production and the reduction of costs, alcohol hydrogen production has become the first choice for industrial hydrogen production. Copper-based catalysts represented by CuO / ZnO / Al2O3 have high H2 selectivity and have been widely used in alcohol hydrogen production, but their catalytic activity needs to be further improved. The carrier can stabilize the active sites of CuO / ZnO / Al2O3 catalysts, effectively reduce the effects of carbon deposition and sintering, and thus improve the catalytic activity and stability. CeO2 is an excellent catalyst carrier. Its unique oxygen storage and release capacity enables it to quickly consume or generate oxygen vacancies on the crystal surface under oxygen-deficient or oxygen-rich conditions. Studies have shown that the morphology of nanoscale CeO2 crystals significantly affects the performance of the catalyst, because different morphologies represent different exposed crystal faces, surface structures, and ion mobility. Therefore, using CeO2 with different morphologies as a carrier of CuO / ZnO / Al2O3 catalysts is expected to obtain copper-based catalysts with high catalytic activity. Summary of the invention

[0003] The first object of the present invention is to provide a morphology-controlled CeO2-loaded CuO / ZnO / Al2O3 catalyst having high catalytic activity and stability in the catalytic alcohol reforming hydrogen production reaction.

[0004] The second object of the present invention is to provide a method for preparing the CeO2-loaded CuO / ZnO / Al2O3 catalyst.

[0005] The third object of the present invention is to provide an application of the CeO2-loaded CuO / ZnO / Al2O3 catalyst.

[0006] To achieve the above purpose, the present invention adopts the following technical means: A method for preparing a morphology-controllable CeO2-loaded CuO / ZnO / Al2O3 catalyst, characterized in that it comprises the following steps: (1) under stirring conditions, adding a sodium hydroxide solution dropwise to a cerium salt solution to obtain a suspension, and subjecting the suspension to hydrothermal treatment, drying, and calcining to obtain CeO2 powder; In some embodiments, the hydrothermal treatment step is known to those skilled in the art to be placing the suspension in a reactor and performing hydrothermal treatment at different temperatures, cooling the suspension, centrifuging the suspension to obtain a precipitate, and washing the precipitate several times, drying the precipitate, and calcining the precipitate.

[0007] (2) The CeO2 powder is immersed in a solution containing copper salt, zinc salt and aluminum salt, and then the obtained powder is dried and calcined to obtain a CeO2-loaded CuO / ZnO / Al2O3 catalyst.

[0008] The cerium salt includes at least one of cerium nitrate, cerium chloride or cerium sulfate; The mass ratio of the cerium salt to sodium hydroxide is 1:10-20.

[0009] The hydrothermal temperature is 80-200°C and the hydrothermal time is 12-24h.

[0010] In some preferred embodiments, the hydrothermal temperature is 150-200°C and the hydrothermal time is 12-24h to obtain cubic CeO2.

[0011] In some preferred embodiments, the hydrothermal temperature is 80-120°C and the hydrothermal time is 12-24h to obtain nanorod-type CeO2.

[0012] In the step (1), the cerium salt solution and polyvinyl pyrrolidone may be mixed, followed by hydrothermal reaction, drying and calcination to obtain CeO2 powder; the mass ratio of the cerium salt to polyvinyl pyrrolidone is 1:0.2~0.6; the temperature of the hydrothermal reaction is 120~180°C, and the time of the hydrothermal reaction is 4~12h, thereby obtaining polyhedral CeO2.

[0013] In the step (1), the drying temperature is 60-120°C, the roasting temperature is 300-500°C, and the roasting time is 3-6h.

[0014] The copper salt in step (2) includes at least one of copper nitrate, copper chloride or copper sulfate; The zinc salt includes at least one of zinc nitrate, zinc chloride or zinc sulfate; The aluminum salt includes at least one of aluminum nitrate, aluminum chloride or aluminum sulfate; The molar ratio of the copper salt, zinc salt and aluminum salt is 3-5:1.2-2.5:0.5-1.5; The drying temperature is 80~100°C, the roasting temperature is 200~400°C, and the roasting time is 1~3h.

[0015] The present invention also provides an application of a morphology-controllable CeO2-loaded CuO / ZnO / Al2O3 catalyst, which is applied to catalyze the reforming of alcohols to produce hydrogen; the alcohols include one or more of methanol, ethanol and glycerol.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The catalyst provided by the present invention has fine and uniform particles, large specific surface area and pore volume, many oxygen vacancies and chemically adsorbed oxygen, good reduction performance, and strong methanol adsorption capacity.

[0017] 2. The catalyst provided by the present invention has high catalytic activity. After being applied to alcohol reforming to produce hydrogen, the conversion rate is greater than 90%, more preferably greater than 95%, and further preferably can reach 100%.

[0018] 3. The catalyst provided by the present invention has low carbon monoxide selectivity and high catalytic stability in catalytic alcohol reforming to produce hydrogen. After long-term continuous catalysis, the alcohol conversion rate remains stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The XRD patterns of the catalysts prepared in Example 1, Example 2 and Example 3 are shown.

[0020] Figure 2 TEM images of the catalysts prepared in Example 1, Example 2 and Example 3 are shown. Figure 2 (a) is a TEM image of the catalyst prepared in Example 1, Figure 2 (b) is a TEM image of the catalyst prepared in Example 2, Figure 2 (c) is the TEM image of the catalyst prepared in Example 3.

[0021] Figure 3 The EDS mapping images of the catalysts prepared in Example 1, Example 2 and Example 3 are shown. Figure 2 (a) is the EDS mapping diagram of the catalyst prepared in Example 1. Figure 2 (b) is the EDS mapping diagram of the catalyst prepared in Example 2. Figure 2 (c) is the EDS mapping image of the catalyst prepared in Example 3.

[0022] Figure 4 The H2-TPR curves of the catalysts prepared in Example 1, Example 2 and Example 3 are shown.

[0023] Figure 5 The CH3OH-TPD curves of the catalysts prepared in Example 1, Example 2 and Example 3 are shown.

[0024] Figure 6 Thermogravimetric curves of the catalysts prepared in Example 1, Example 2 and Example 3 are shown. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] Example 1 Cerium nitrate and sodium hydroxide with a mass ratio of 1:10 are dissolved in 30mL of deionized water to obtain cerium nitrate solution and sodium hydroxide solution, and then the sodium hydroxide solution is slowly added dropwise to the cerium nitrate solution under vigorous stirring to obtain a suspension. The suspension is placed in a reactor and hydrothermally heated at 180°C for 24h, centrifuged after cooling to obtain a precipitate, and washed several times. The precipitate is dried at 60°C and roasted at 300°C for 3h to obtain cubic CeO2. The cubic CeO2 powder is immersed in a solution of copper nitrate, zinc nitrate and aluminum nitrate in a molar ratio of 3:1.2:0.5, and then the obtained powder is dried at 80°C and roasted at 200°C for 1h to obtain a cubic CeO2 loaded CuO / ZnO / Al2O3 catalyst.

[0027] Example 2 Cerium sulfate and polyvinyl pyrrolidone in a mass ratio of 1:0.2 are dissolved in 30 mL of deionized water to obtain a uniform solution. The solution is placed in a reactor and hydrothermal at 160°C for 8 hours, centrifuged after cooling to obtain a precipitate, and washed several times. The precipitate is dried at 90°C and roasted at 400°C for 4 hours to obtain polyhedral CeO2. The polyhedral CeO2 powder is immersed in a solution of copper sulfate, zinc sulfate and aluminum sulfate in a molar ratio of 4:2:1, and then the obtained powder is dried at 90°C and roasted at 300°C for 2 hours to obtain a polyhedral CeO2-loaded CuO / ZnO / Al2O3 catalyst.

[0028] Example 3 Cerium chloride and sodium hydroxide with a mass ratio of 1:20 are dissolved in 30mL of deionized water to obtain a cerium chloride solution and a sodium hydroxide solution, and then the sodium hydroxide solution is slowly added dropwise to the cerium chloride solution under vigorous stirring to obtain a suspension. The suspension is placed in a reactor and hydrothermally heated at 100°C for 24h, centrifuged after cooling to obtain a precipitate, and washed several times. The precipitate is dried at 120°C and roasted at 500°C for 6h to obtain nanorod-type CeO2. The nanorod-type CeO2 powder is immersed in a solution of copper chloride, zinc chloride and aluminum chloride in a molar ratio of 5:2.5:1.5, and then the obtained powder is dried at 100°C and roasted at 400°C for 3h to obtain a nanorod-type CeO2-loaded CuO / ZnO / Al2O3 catalyst.

[0029] The performance test method of the CeO2-loaded CuO / ZnO / Al2O3 catalyst for catalytic alcohol reforming to produce hydrogen is as follows: The catalyst is evenly mixed with quartz particles and filled in the middle of the tubular reactor, and both ends of the reactor are sealed with threads. The tubular reactor is then placed in a tubular furnace controlled by a thermocouple. After the furnace temperature rises to the set temperature, an electronic injection pump is used to inject a mixed solution of alcohol and water with a molar ratio of 1:1.2 into the tubular reactor. The mixed gas of alcohol and water evaporated at the front end of the tubular reactor contacts and reacts with the catalyst to generate hydrogen-rich gas. Unreacted alcohol and water are collected by a condenser. A soap bubble flowmeter is used to measure the flow rate of the reformed gas, and a gas chromatograph is used to detect the composition of the reformed gas. Alcohol conversion rate X Alcohol and hydrogen production V H2 Calculated according to the following formula:

[0030] in, V out is the molar flow rate of reformed gas, φ CO , φ CO2 , φ H2 Represent the contents of carbon monoxide, carbon dioxide and hydrogen in the reformed gas, respectively. V Alcohol,in is the molar flow rate of alcohol injected into the microreactor.

[0031] The inventors conducted XRD tests on the catalysts prepared in Example 1, Example 2 and Example 3. The results are as follows: Figure 1 As shown. Figure 1It can be found that the diffraction peaks of CeO2 and CuO appear in the prepared catalyst. The grain size of CeO2 in the catalyst was calculated according to the Scherrer formula, and the results are shown in Table 1. It can be found from Table 1 that the grain size of the prepared catalyst is small.

[0032] Table 1 Crystal size of CeO2 in the catalyst catalyst <![CDATA[CeO2 grain size (nm)]]> Example 1 Example 2 Example 3 33.614.39.2 The inventors conducted TEM tests on the catalysts prepared in Example 1, Example 2 and Example 3. The results are as follows: Figure 2 As shown. Figure 2 It can be found that the catalysts prepared in Example 1, Example 2 and Example 3 are respectively in the form of a cube, a polyhedron and a nanorod, and the lattices of CeO2 and CuO can be observed.

[0033] The inventors conducted EDS mapping tests on the catalysts prepared in Example 1, Example 2 and Example 3. The results are as follows: Figure 3 As shown. Figure 3 It can be found that Cu, Zn and Al are highly dispersed on the surface of CeO2 grains.

[0034] The inventors tested the specific surface area and pore volume of the catalysts prepared in Example 1, Example 2 and Example 3, and the results are shown in Table 2. It can be found from Table 2 that the specific surface area and pore volume of the prepared catalysts are both large.

[0035] Table 2 Specific surface area and pore volume of catalysts catalyst <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Example 1 Example 2 Example 3 76.1587.9699.83 0.180.210.23 The inventors conducted H2-TPR tests on the catalysts prepared in Example 1, Example 2 and Example 3. The results are as follows: Figure 4 As shown. Figure 4 It can be found that the position of the reduction peak in the prepared catalyst is significantly lower than the reduction temperature of pure CuO (~320°C), indicating that the CeO2 support changes the electronic structure of the Cu species.

[0036] The inventors conducted CH3OH-TPD tests on the catalysts prepared in Example 1, Example 2 and Example 3. The results are as follows: Figure 5 As shown. Figure 5 It can be found that the prepared catalysts have strong adsorption capacity for methanol.

[0037] The inventors conducted XPS tests on the catalysts prepared in Example 1, Example 2 and Example 3, and calculated the contents of oxygen vacancies and adsorbed oxygen in the catalysts based on the XPS results, and the results are shown in Table 3. It can be found from Table 3 that the contents of oxygen vacancies and adsorbed oxygen in the prepared catalysts are both high.

[0038] Table 3 Oxygen vacancies and adsorbed oxygen contents in the catalysts catalyst Oxygen vacancies (%) Adsorbed oxygen (%) Example 1 Example 2 Example 3 17.7518.9819.51 45.3148.5452.08 The inventors applied the catalysts prepared in Example 1, Example 2 and Example 3 to methanol reforming to produce hydrogen, and tested the catalysts at 6.05 h. -1 The mass space velocity and methanol conversion at 280°C, hydrogen yield, carbon monoxide selectivity and catalytic stability were characterized, and the results are shown in Table 4. As can be seen from Table 4, the catalysts prepared in Example 1, Example 2, Example 3 and Example 4 have low CO selectivity and excellent catalytic activity and stability.

[0039] Table 4 Catalytic performance of methanol reforming to produce hydrogen catalyst Methanol conversion rate (%) <![CDATA[Hydrogen production rate (mol·h -1 ·g cat -1 )]]> CO selectivity (%) Stability (h) Example 1 Example 2 Example 3 96.998.4100 0.6510.6610.672 2.111.971.86 353740 The inventors conducted a thermogravimetric test on the catalyst after catalytic methanol reforming to produce hydrogen. The results are as follows: Figure 6 As shown. Figure 6 It can be found that the carbon deposition amount of the prepared catalysts is less than 10%.

[0040] The inventors applied the catalysts prepared in Example 1, Example 2 and Example 3 to ethanol reforming to produce hydrogen, and tested the catalysts at 6.05 h. -1 The mass space velocity and ethanol conversion at 520°C, hydrogen yield, carbon monoxide selectivity and catalytic stability were characterized, and the results are shown in Table 5. As can be seen from Table 5, the catalysts prepared in Example 1, Example 2 and Example 3 have low CO selectivity and excellent catalytic activity and stability.

[0041] Table 5 Catalytic performance of ethanol reforming to produce hydrogen catalyst Ethanol conversion rate (%) <![CDATA[Hydrogen production rate (mol·h -1 ·g cat -1 )]]> CO selectivity (%) Stability (h) Example 1 Example 2 Example 3 97.398.1100 1.3081.3181.344 3.643.293.02 252830 The inventors applied the catalysts prepared in Example 1, Example 2 and Example 3 to propylene glycol reforming to produce hydrogen, and tested the catalysts at 6.05 h. -1 The mass space velocity of 1.5 and 620° C. and the glycerol conversion, hydrogen yield, carbon monoxide selectivity and catalytic stability were characterized, and the results are shown in Table 6. As can be seen from Table 6, the catalysts prepared in Example 1, Example 2 and Example 3 have low CO selectivity and excellent catalytic activity and stability.

[0042] Table 6 Catalytic performance of propylene glycol reforming to produce hydrogen catalyst Glycerol conversion rate (%) <![CDATA[Hydrogen production rate (mol·h -1 ·g cat -1 )]]> CO selectivity (%) Stability (h) Example 1 Example 2 Example 3 98.399.2100 1.5261.5381.568 5.795.475.26 181922 Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst, characterized in that: The steps include: (1) under stirring conditions, adding a sodium hydroxide solution dropwise to a cerium salt solution to obtain a suspension, and subjecting the suspension to hydrothermal treatment, drying, and calcining to obtain CeO2 powder; (2) The CeO2 powder is immersed in a solution containing copper salt, zinc salt and aluminum salt, and then the obtained powder is dried and calcined to obtain a CeO2-loaded CuO / ZnO / Al2O3 catalyst.

2. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst according to claim 1, characterized in that: The cerium salt includes at least one of cerium nitrate, cerium chloride or cerium sulfate; The mass ratio of the cerium salt to sodium hydroxide is 1:10-20.

3. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 1, characterized in that: The hydrothermal temperature is 80-200°C and the hydrothermal time is 12-24h.

4. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 3, characterized in that: The hydrothermal temperature is 150-200°C and the hydrothermal time is 12-24h.

5. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 3, characterized in that: The hydrothermal temperature is 80-120°C and the hydrothermal time is 12-24h.

6. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 1, characterized in that: In the step (1), the cerium salt solution and polyvinyl pyrrolidone are mixed, followed by hydrothermal reaction, drying and calcination to obtain CeO2 powder; the mass ratio of the cerium salt to polyvinyl pyrrolidone is 1:0.2~0.6; the temperature of the hydrothermal reaction is 120~180°C, and the time of the hydrothermal reaction is 4~12h.

7. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst according to claim 6, characterized in that: In the step (1), the drying temperature is 60-120°C, the roasting temperature is 300-500°C, and the roasting time is 3-6h.

8. The method for preparing a CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 1, characterized in that: The copper salt in step (2) includes at least one of copper nitrate, copper chloride or copper sulfate; The zinc salt includes at least one of zinc nitrate, zinc chloride or zinc sulfate; The aluminum salt includes at least one of aluminum nitrate, aluminum chloride or aluminum sulfate; The molar ratio of the copper salt, zinc salt and aluminum salt is 3-5:1.2-2.5:0.5-1.5; The drying temperature is 80~100°C, the roasting temperature is 200~400°C, and the roasting time is 1~3h.

9. Use of the CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in any one of claims 1 to 8 in catalytic alcohol reforming to produce hydrogen.

10. The use of CeO2-loaded CuO / ZnO / Al2O3 catalyst as claimed in claim 9, characterized in that: The alcohols include one or more of methanol, ethanol and glycerol.

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