Preparation method of low-copper methanol reforming hydrogen production catalyst

Abstract

The present invention discloses a method for preparing a low-copper methanol reforming hydrogen production catalyst, comprising the following steps: preparing a complex solution by deionized water, copper nitrate, citric acid, and 25% ammonia water; adding zinc-aluminum composite oxide powder to the complex solution by a double immersion method, ultrasonically treating, and calcining at 300-350°C for 2-4 hours to obtain a CuO / ZnO-Al2O3 composite oxide powder; and fully grinding and mixing the CuO / ZnO-Al2O3 composite oxide powder and graphite, followed by tableting to obtain a cylindrical catalyst. The invention reduces the CuO content in the methanol reforming hydrogen production catalyst to 5-10% while maintaining high low-temperature activity and thermal stability. When applied to methanol steam reforming hydrogen production, the catalyst reduces the CO content in the reformed tail gas compared to the traditional CuZnAl methanol steam reforming hydrogen production catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol reforming hydrogen production catalysts, and in particular to a method for preparing a low-copper methanol reforming hydrogen production catalyst. Background Art

[0002] The methanol steam reforming process for hydrogen production operates under relatively mild reaction conditions, primarily producing H₂, CO₂, and a small amount of CO. After purification steps such as pressure swing adsorption, the product can be converted into high-purity hydrogen, making it ideal for use in hydrogen fuel cells and considered one of the most promising hydrogen production technologies for use in hydrogen fuel cells. To reduce costs, copper-based catalysts are the most widely studied catalysts for methanol hydrogen production due to their high reactivity, high hydrogen selectivity, and low manufacturing cost.

[0003] For example, CN108654624A discloses a spinel catalyst for methanol-to-hydrogen production. The catalyst is composed of CuO, Al2O3, NiO, and graphite, with the mass fractions of CuO being 25.0%-45.0%, NiO being 0.5%-5%, Al2O3 being 51.5%-71.5%, and graphite being 2.0%-5.0%. The catalyst has a face-centered cubic spinel structure. While the aforementioned patent uses antioxidants to increase the shelf life of the catalyst and dispersants to improve the dispersion of the raw materials, the presence of a large amount of copper in the catalyst still raises the issue of high manufacturing costs, and the dispersant's functionality is limited.

[0004] At the same time, most existing copper-based catalysts contain 30-60% copper oxide. Excessively high copper content can lead to high CO levels in the reformed exhaust and poor high-temperature stability. Simply reducing the copper content in the catalyst would reduce the specific surface area of ​​the copper-zinc-aluminum catalyst and the specific surface area of ​​the active copper to a certain extent, leading to a decrease in catalyst activity. Therefore, how to reduce the copper content without affecting the catalyst activity has become a challenge in existing technologies. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a low-copper methanol reforming hydrogen production catalyst to solve the technical problems in the prior art that the copper oxide content is difficult to reduce and the dispersion is difficult to improve.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] The present invention provides a low-copper methanol reforming hydrogen production catalyst, the catalyst composition is: CuO / ZnO-Al2O3;

[0008] Calculated by mass percentage, the catalyst comprises the following components: 5-10% CuO, 65-70% ZnO, and 25-30% Al2O3.

[0009] The present invention also provides a method for preparing a low-copper methanol reforming hydrogen production catalyst, comprising the following steps:

[0010] A soluble salt corresponding to aluminum-zinc oxide is mixed with deionized water to obtain a mixed solution, and the mixed solution is added to an alkaline solution at a water bath temperature of 70-80°C for co-precipitation. The mixture is stirred thoroughly during the addition process, and the pH of the system is adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate. After aging for 2-4 hours, the precipitate is washed, filtered, and dried at 80-100°C to obtain a zinc-aluminum composite oxide powder.

[0011] Deionized water, copper nitrate, citric acid and 25% ammonia water were used to prepare a complexing solution;

[0012] The zinc-aluminum composite oxide powder is added to the complex solution by a double immersion method, and after sufficient stirring, ultrasonic treatment is performed, and the mixture is allowed to stand at room temperature for 10-12 hours, and then dried at 80-100° C., and finally calcined at a temperature of 300-350° C. for 2-4 hours to obtain a CuO / ZnO-Al2O3 composite oxide powder;

[0013] The CuO / ZnO-Al2O3 composite oxide powder and graphite are fully ground and mixed, and then pressed into tablets to obtain a cylindrical catalyst.

[0014] As a preferred embodiment of the present invention, the alkaline solution includes at least one of ammonium bicarbonate solution, sodium carbonate solution, ammonium carbonate solution and ammonia water.

[0015] As a preferred embodiment of the present invention, the concentration of the alkaline solution is 0.1-0.5 mol / L.

[0016] As a preferred embodiment of the present invention, the soluble salt is any one of nitrate, sulfate and chloride.

[0017] As a preferred solution of the present invention, the graphite accounts for 3-5% of the mass fraction of the CuO / ZnO-Al2O3 composite oxide powder.

[0018] As a preferred embodiment of the present invention, during the grinding process of the cylindrical catalyst, the particles are 3*3mm or 5*5mm, and the mechanical strength is greater than 100N.

[0019] The present invention also provides an application of a low-copper methanol reforming hydrogen production catalyst in a methanol steam reforming hydrogen production reaction.

[0020] As a preferred embodiment of the present invention, the low-copper methanol reforming hydrogen production catalyst is applied to methanol steam reforming hydrogen production, and the methanol steam reforming hydrogen production is carried out in a fixed bed or tubular reactor, including a reduction activation step and a hydrogen production reaction step:

[0021] The reduction activation step comprises: performing temperature-programmed reduction activation under normal pressure and H2 atmosphere, with an activation temperature of 220-250°C, a heating rate of 5-10°C / min, a constant temperature time of 1-2h, and a hydrogen flow rate of 30-60 mL·min -1 ;

[0022] After the reduction activation step, the hydrogen production reaction step is carried out, and the specific conditions are: the raw material is a mixture of water and methanol, the water-to-methanol molar ratio is 1.1-1.3, the liquid hourly space velocity is 0.5-2h-1, the temperature is 220-300°C, and the pressure is 0.1-2.0MPa.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] Compared with the traditional CuZnAl methanol steam reforming hydrogen production catalyst, the present invention has the advantages of low CuO content, good low temperature activity and strong thermal stability. The interaction between CuO and ZnO-Al2O3 composite carrier modulates the reduction performance of CuO. + It is beneficial to inhibit the reverse water gas shift reaction, thereby reducing the CO content of the reformed gas. The CO content in the reformed tail gas is low, and the obtained reformed gas can be directly used in high-temperature hydrogen fuel cells (CO<3%) or used in low-temperature hydrogen fuel cells (CO<10ppm) after purification;

[0025] In the preparation method of the present invention, a coprecipitation method is first used to prepare a ZnO-Al2O3 non-stoichiometric composite oxide powder. The doping of ZnO with Al2O3 promotes the generation of more oxygen vacancies and the formation of surface heterogeneous structural defects in ZnO. The wet chemical complex loading method of CuO is used to facilitate the dispersion and adsorption of copper ammonia complex ions on the surface of the composite oxide powder. The combination of these factors facilitates the dispersion of low-concentration CuO similar to single atoms and inhibits the thermal growth of copper atom grains, thereby enabling the catalyst to have the advantages of good low-temperature activity and strong thermal stability while having a low CuO content.

[0026] The invention has simple components, cheap and easily available raw materials, a simple and easy-to-operate preparation method, easy-to-control reaction conditions, good catalyst repeatability, and good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0028] Figure 1 The present invention provides a flow chart of a method for preparing a low-copper methanol reforming hydrogen production catalyst.

[0029] Figure 2 The present invention provides a graph showing the results of a 100-hour stability test of the 5Cu / 65Zn30Al catalyst in Example 1;

[0030] Figure 3 Provides a structural schematic diagram of a mixing device for the present invention;

[0031] In the figure: 1-first material box; 2-second material box; 3-third material box; 4-capillary tube; 5-mixing box; 6-connecting pipe; 7-motor. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The present invention provides a low-copper methanol reforming hydrogen production catalyst, which is composed of CuO / ZnO-Al2O3, wherein the CuO content is 5-10%, the ZnO content is 65-70%, and the Al2O3 content is 25-30%.

[0034] This low-copper methanol reforming hydrogen production catalyst is a catalyst in the methanol steam reforming hydrogen production reaction. This methanol steam reforming hydrogen production reaction is carried out in a fixed bed or tubular reactor, and is subjected to temperature-programmed reduction activation under normal pressure and H2 atmosphere. The activation temperature is 220-250℃, the heating rate is 5-10℃ / min, the constant temperature time is 1-2h, and the hydrogen flow rate is 30-60mL·min -1 After the reduction activation is completed, the hydrogen production reaction is carried out. The raw materials are a mixture of water and methanol, the water-to-methanol molar ratio is 1.1-1.3, and the liquid hourly space velocity of the hydrogen production reaction is 0.5-2h -1 , temperature is 220-300℃, and pressure is 0.1-2.0MPa.

[0035] Compared to conventional CuZnAl methanol steam reforming hydrogen production catalysts, the low-copper methanol reforming hydrogen production catalyst of this invention offers advantages such as low CuO content, low CO content in the reformed tail gas, excellent low-temperature activity, and strong thermal stability. When applied to the aforementioned methanol steam reforming hydrogen production reaction, the resulting reformed gas can be used directly in high-temperature hydrogen fuel cells (CO<3%) or, after purification, in low-temperature hydrogen fuel cells (CO<10ppm), demonstrating its high economic value.

[0036] like Figure 1 As shown, the present invention also provides a method for preparing the above-mentioned low-copper methanol reforming hydrogen production catalyst, comprising the following steps:

[0037] A soluble salt corresponding to aluminum zinc oxide is mixed with deionized water to obtain a mixed solution;

[0038] Adding the mixed solution to an alkaline solution at a water bath temperature of 70-80° C. for co-precipitation, maintaining sufficient stirring during the addition process, and adjusting the pH of the system to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate;

[0039] After aging the zinc-aluminum composite hydrated oxide precipitate for 2-4 hours, washing, filtering, and drying at 80-100° C. to obtain zinc-aluminum composite oxide powder;

[0040] Deionized water, copper nitrate, citric acid and 25% ammonia water were used to prepare a complexing solution;

[0041] The zinc-aluminum composite oxide powder is added to the complex solution by a double immersion method, and after sufficient stirring, ultrasonic treatment is performed, and the mixture is allowed to stand at room temperature for 10-12 hours, and then dried at 80-100° C., and finally calcined at a temperature of 300-350° C. for 2-4 hours to obtain a CuO / ZnO-Al2O3 composite oxide powder;

[0042] The CuO / ZnO-Al2O3 composite oxide powder and graphite are fully ground and mixed, and then pressed into tablets to obtain a cylindrical catalyst.

[0043] In the preparation of the complex solution, it is necessary to mix it thoroughly, but the shear force during conventional mixing should be avoided. Therefore, in the present invention, when preparing the complex solution, the specific method is as follows:

[0044] By utilizing the capillary effect, copper nitrate, citric acid and 25% ammonia water are mixed separately under the transport of capillaries, thereby reducing the shear force during mixing;

[0045] Copper nitrate, citric acid and 25% ammonia water are mixed inside the capillary tube and mixed in the tube by capillary force;

[0046] The mixed solution is then dispersed by mixing flow.

[0047] According to the above mixing method, a specific mixing device is provided below for implementation.

[0048] like Figure 3 As shown, the mixing device for preparing the complex solution includes:

[0049] The first material box 1 is used to hold copper nitrate;

[0050] The second material box 2 is used to hold citric acid;

[0051] The third material box 3 is used to hold ammonia water with a concentration of 25%;

[0052] A capillary tube 4 is provided on the top of the third material box 3, the two ends of the capillary tube 4 are respectively connected to the first material box 1 and the second material box 2, and the middle of the capillary tube 4 is connected to the third material box 3, wherein deionized water can be added by mixed flow after mixing;

[0053] The copper nitrate solution in the first material box 1 and the citric acid solution in the second material box 2 move along the two ends of the capillary 4 to the middle of the capillary 4 under the capillary effect of the capillary 4, mix in the middle of the capillary 4, and fall into the third material box 3 after contact.

[0054] Both ends of the capillary tube 4 are respectively inserted into the bottom of the inner wall of the first material box 1 and the second material box 2 , and the first material box 1 and the second material box 2 are at the same height and higher than the third material box 3 .

[0055] A layer of hydrophilic material is attached to the inner wall of the capillary 4 .

[0056] This method utilizes the capillary effect and fluid dynamics principles, specifically:

[0057] The working principle of capillary tube is based on the capillary phenomenon. Under the action of surface tension (surface tension) inside a small diameter pipe, the liquid will rise or fall along the pipe wall. However, in this method, the capillary tube 4 is used as a connection and transmission channel.

[0058] The principle of fluid dynamics is that when liquids flow through capillaries, they must overcome resistance (friction) and are driven by pressure differences. If there is a pressure difference between the liquid surfaces in two containers (such as a height difference or external pressure), the liquids will flow from the higher pressure end to the lower pressure end through the capillary tube, achieving mixing.

[0059] In this method, the heights of the first material box 1 and the second material box 2 are both higher than the height of the third material box 3, so that the liquid level in the third material box 3 is always lower than the liquid level in the first material box 1 and the second material box 2.

[0060] Because the inner wall of the capillary is smooth and the tube diameter is small, the friction is small, and the liquid inside the capillary is mainly affected by the surface tension of the liquid, so that the liquid forms a concave surface in the capillary tube with a small diameter, reducing friction with the tube wall, thereby reducing shear force.

[0061] At the same time, in the capillary, the liquid flow velocity gradient is unevenly distributed, with a fast flow velocity in the center and a slow flow velocity near the wall, forming a boundary layer (laminar fluid layer). This laminar flow reduces the friction and shear force of the wall.

[0062] From the above analysis, it can be seen that the shear force of the mixing device mentioned in this method is relatively small.

[0063] The copper nitrate solution and citric acid solution on both sides of the capillary 4 move toward the middle of the capillary 4 under the capillary effect, and finally meet in the middle of the capillary 4, and then fall into the inside of the third material box 3 due to gravity.

[0064] In order to improve the mixing efficiency, a plurality of capillaries 4 are provided, and the plurality of capillaries 4 are transported simultaneously.

[0065] In order to further improve the transport efficiency of the capillary 4, the first material box 1 and the second material box 2 may be sealed and then pressurized inside.

[0066] The two liquids are placed on both sides of the capillary tube 4, and the capillary action and gravity are used to allow the liquids to slowly penetrate, diffuse and mix.

[0067] A mixing box 5 is provided between the middle of the capillary tube 4 and the third material box 3. The mixing box 5 is spherical to facilitate mixing inside the mixing box 5.

[0068] A plurality of connecting pipes 6 are provided between the mixing box 5 and the third material box 3. The plurality of connecting pipes 6 are cross-arranged to form a mesh structure, so that the mixed liquid inside the mixing box 5 flows into the connecting pipes 6 of the mesh structure under the action of gravity. The mixed liquid is dispersed and mixed multiple times by the connecting pipes 6 of the mesh structure and then reaches the inside of the third material box 3.

[0069] The mixed copper nitrate solution and citric acid solution are sequentially dispersed and mixed through a plurality of connecting pipes 6 to further improve the mixing effect, while the shear force is small.

[0070] The bottom of the third material box 3 is connected to a motor 7, which drives the third material box 3 to rotate, so that the mixed solution as a whole is further mixed under the action of centrifugal force.

[0071] Preferably, the soluble salt is any one of nitrate, sulfate and chloride.

[0072] Preferably, the alkaline solution includes at least one of ammonium bicarbonate solution, sodium carbonate solution, ammonium carbonate solution and aqueous ammonia.

[0073] Preferably, the concentration of the alkaline solution is 0.1-0.5 mol / L.

[0074] Preferably, the graphite accounts for 3-5% of the mass fraction of the CuO / ZnO-Al2O3 composite oxide powder.

[0075] Preferably, during the grinding process of the cylindrical catalyst, the particles are 3*3mm or 5*5mm, and the mechanical strength is >100N.

[0076] In the preparation method of the present invention, a ZnO-Al2O3 non-stoichiometric composite oxide powder is first prepared by coprecipitation. The doping of ZnO with Al2O3 promotes the generation of more oxygen vacancies and the formation of surface heterogeneous structural defects in ZnO. CuO is loaded using a wet chemical complexation method, which facilitates the dispersion and adsorption of copper-ammonia complex ions on the surface of the composite oxide powder.

[0077] The combination of these factors is conducive to the dispersion of low-concentration CuO similar to single atoms and the inhibition of the thermal growth of copper atomic grains. The higher the CuO dispersion, the smaller the copper crystallites, the larger the active copper specific surface area, and the higher the activity, thereby improving the catalytic activity and high-temperature stability of the catalyst.

[0078] At the same time, the interaction between CuO and ZnO-Al2O3 composite supports modulates the reduction performance of CuO. + It is beneficial to inhibit the reverse water gas shift reaction, thereby reducing the CO content of the reformed gas. The obtained reformed gas can be directly used in high-temperature hydrogen fuel cells (CO<3%) or used in low-temperature hydrogen fuel cells (CO<10ppm) after purification.

[0079] The components of the present invention are simple, the raw materials are cheap and easily available, the preparation method is simple and easy to operate, the reaction conditions are easy to control, the catalyst has good reproducibility, and the obtained low-copper methanol reforming hydrogen production catalyst has the advantages of low CuO content, low CO content in the reformed tail gas, good low-temperature activity, strong thermal stability, etc., and has good industrial application prospects.

[0080] The following is further described by way of examples:

[0081] Example 1

[0082] (1) 62.04 g of aluminum nitrate and 151.33 g of zinc nitrate were dissolved in 200 mL of deionized water and stirred until a clear solution was obtained to obtain solution A; 42.4 g of sodium carbonate and 22.3 g of ammonium bicarbonate were dissolved in 200 mL of deionized water to obtain a mixed solution B of sodium carbonate and ammonium bicarbonate; mixed solution A was added to mixed solution C at a water bath temperature of 70-80°C for co-precipitation, with sufficient stirring being maintained during the addition process, and the pH was adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate, which was aged for 2 hours, washed, filtered, and dried at 100°C to obtain a zinc-aluminum composite oxide powder;

[0083] (2) 100 ml of complex solution was prepared by deionized water, 11.79 g of copper nitrate, 5.00 g of citric acid and 10 ml of 25% ammonia water, and added to the zinc-aluminum composite oxide powder prepared by (1) by double leaching method. After being fully stirred, the powder was ultrasonically treated and allowed to stand at room temperature for 10 h, dried at 100 ° C, and finally calcined at 350 ° C for 4 h to obtain CuO / ZnO-Al2O3 composite oxide powder;

[0084] (3) The prepared CuO-ZnO-Al2O3 composite oxide powder and graphite (accounting for 3-5% of the mass fraction of the composite oxide powder) were fully ground and mixed, and then tableted to obtain a cylindrical catalyst with particles of 3*3mm and a mechanical strength of >100N. The catalyst was labeled 5Cu / 65Zn30Al.

[0085] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0086] The evaluation results are: methanol conversion rate is 94%, and the CO content of the reformed gas is 0.3%.

[0087] like Figure 2 As shown, the results of the 100-hour stability test of the 5Cu / 65Zn30Al catalyst prepared in this embodiment show that the methanol conversion rate is basically maintained above 80% and the CO content is maintained below 0.5%.

[0088] Example 2

[0089] (1) 52.22 g of aluminum nitrate and 163.33 g of zinc nitrate were dissolved in 200 mL of deionized water and stirred until a clear solution was obtained to obtain solution A; 42.4 g of sodium carbonate and 22.3 g of ammonium bicarbonate were dissolved in 200 mL of deionized water to obtain a mixed solution B of sodium carbonate and ammonium bicarbonate; mixed solution A was added to mixed solution C at a water bath temperature of 70-80°C for co-precipitation, with sufficient stirring being maintained during the addition process, and the pH was adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate, which was aged for 2 hours, washed, filtered, and dried at 100°C to obtain a zinc-aluminum composite oxide powder;

[0090] Steps (2) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 70Zn25Al.

[0091] The 5Cu / 70Zn25Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0092] The evaluation results are: methanol conversion rate is 95%, and the CO content of the reformed gas is 0.3%.

[0093] Example 3

[0094] (1) 52.22 g of aluminum nitrate and 151.33 g of zinc nitrate were dissolved in 200 mL of deionized water and stirred until a clear solution was obtained to obtain solution A; 42.4 g of sodium carbonate and 22.3 g of ammonium bicarbonate were dissolved in 200 mL of deionized water to obtain a mixed solution B of sodium carbonate and ammonium bicarbonate; mixed solution A was added to mixed solution C at a water bath temperature of 70-80°C for co-precipitation, with sufficient stirring being maintained during the addition process, and the pH was adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate, which was aged for 2 hours, washed, filtered, and dried at 100°C to obtain a zinc-aluminum composite oxide powder;

[0095] (2) 100 ml of complex solution was prepared by adding deionized water, 23.61 g of copper nitrate, 10.00 g of citric acid and 20 ml of 25% ammonia water, and the zinc-aluminum composite oxide powder prepared in (1) was added by double leaching method. After being fully stirred, the powder was ultrasonically treated and allowed to stand at room temperature for 10 h, dried at 100 ° C, and finally calcined at 350 ° C for 4 h to obtain CuO / ZnO-Al2O3 composite oxide powder.

[0096] Step (3) is the same as in Example 1; the catalyst is marked as 10Cu / 65Zn25Al.

[0097] The 10Cu / 65Zn25Al catalyst prepared in this example was used for a fixed-bed methanol steam reforming hydrogen production reaction with an activation temperature of 250°C, a raw material water-to-methanol molar ratio of 1.2, a liquid hourly space velocity of 1h-1, a reaction pressure of 0.1 MPa, a reaction temperature of 250°C, and a reaction time of 8h.

[0098] The evaluation results are: methanol conversion rate is 96%, and the CO content of the reformed gas is 0.3%.

[0099] Example 4

[0100] (1) 52.22 g of aluminum nitrate and 151.33 g of zinc nitrate were dissolved in 200 mL of deionized water and stirred until a clear solution was obtained to obtain solution A; 42.4 g of sodium carbonate and 22.3 g of ammonium bicarbonate were dissolved in 200 mL of deionized water to obtain a mixed solution B of sodium carbonate and ammonium bicarbonate; mixed solution A was added to mixed solution C at a water bath temperature of 70-80°C for co-precipitation, with sufficient stirring being maintained during the addition process, and the pH was adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate, which was aged for 2 hours, washed, filtered, and dried at 100°C to obtain a zinc-aluminum composite oxide powder;

[0101] Steps (2) to (3) are the same as those in Example 3; the catalyst is labeled 10Cu / 70Zn20Al.

[0102] The 10Cu / 70Zn20Al catalyst prepared in this example was used for the fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0103] The evaluation results are: methanol conversion rate is 97% and the CO content of reformed gas is 0.3%.

[0104] Example 5

[0105] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0106] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 220℃, and the reaction time is 8h.

[0107] The evaluation results are: methanol conversion rate is 58%, and the CO content of the reformed gas is 0.1%.

[0108] Example 6

[0109] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0110] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 280℃, and the reaction time is 8h.

[0111] The evaluation results are: methanol conversion rate is 98%, and the CO content of reformed gas is 1.8%.

[0112] Example 7

[0113] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0114] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 0.5h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0115] The evaluation results are: methanol conversion rate is 100%, and the CO content of the reformed gas is 0.2%.

[0116] Example 8

[0117] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0118] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 2h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0119] The evaluation results are: methanol conversion rate is 65%, and the CO content of the reformed gas is 0.2%.

[0120] Example 9

[0121] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0122] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.5 MPa, the reaction temperature is 250°C, and the reaction time is 8 h.

[0123] The evaluation results are: methanol conversion rate is 90%, and the CO content of the reformed gas is 0.3%.

[0124] Example 10

[0125] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0126] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 1.0 MPa, the reaction temperature is 250°C, and the reaction time is 8 h.

[0127] The evaluation results are: methanol conversion rate is 85%, and the CO content of reformed gas is 0.5%.

[0128] Example 11

[0129] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0130] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.2, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 2.0 MPa, the reaction temperature is 250°C, and the reaction time is 8 h.

[0131] The evaluation results are: methanol conversion rate is 75%, and the CO content of the reformed gas is 0.6%.

[0132] Example 12

[0133] Steps (1) to (3) are the same as those in Example 1; the catalyst is labeled 5Cu / 65Zn30Al.

[0134] The 5Cu / 65Zn30Al catalyst prepared in this example was used for fixed-bed methanol steam reforming hydrogen production reaction. The activation temperature was 250°C, the raw material water-to-alcohol molar ratio was 1.1, and the liquid hourly space velocity was 1h -1 , the reaction pressure is 0.1Mpa, the reaction temperature is 250℃, and the reaction time is 8h.

[0135] The evaluation results are: methanol conversion rate is 95%, and the CO content of the reformed gas is 0.3%.

[0136] It can be seen from Examples 1 to 4 that, within the preferred formula and experimental conditions of the present invention, the preparation method of the present invention first adopts a coprecipitation method to prepare a ZnO-Al2O3 non-stoichiometric composite oxide powder, the doping of ZnO with Al2O3 can promote the generation of more oxygen vacancies in ZnO and the formation of surface heterogeneous structural defects, and the wet chemical complex loading method of CuO is beneficial to the dispersion and adsorption of copper ammonia complex ions on the surface of the composite oxide powder. The combination of these factors is beneficial to the single-atom dispersion of low-concentration CuO and the inhibition of the thermal growth of copper atom grains. When the copper content is reduced, the catalyst still has good low-temperature catalytic activity and high-temperature stability.

[0137] From Examples 1, 5 to 12, it can be seen that the catalyst obtained under the preferred formulation and experimental conditions of the present invention has a better reduction performance than the conventional CuZnAl methanol steam reforming hydrogen production catalyst in the methanol steam reforming hydrogen production reaction, in which the interaction between CuO and the ZnO-Al2O3 composite support modulates the reduction performance of CuO. + The presence of the catalyst is beneficial to inhibiting the reverse water-gas shift reaction, thereby reducing the CO content in the reformed gas in the product, and the CO content in the reformed tail gas is low.

[0138] Through the preparation method of the low-copper methanol reforming hydrogen production catalyst of this embodiment, the CuO content in the catalyst can be reduced, and the low-temperature activity and thermal stability can be improved. After being applied to methanol steam reforming hydrogen production, the CO content in the reformed exhaust gas is lower than that of the traditional CuZnAl methanol steam reforming hydrogen production catalyst.

[0139] The above embodiments are merely exemplary embodiments of the present application and are not intended to limit the scope of the present application. The scope of protection of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and scope of protection of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the scope of protection of the present application.

Claims

1. A method for preparing a low-copper methanol reforming hydrogen production catalyst, characterized in that: The steps include: A soluble salt corresponding to aluminum-zinc oxide is mixed with deionized water to obtain a mixed solution, and the mixed solution is added to an alkaline solution at a water bath temperature of 70-80°C for co-precipitation. The mixture is stirred thoroughly during the addition process, and the pH of the system is adjusted to 7.5-8.0 to obtain a zinc-aluminum composite hydrated oxide precipitate. After aging for 2-4 hours, the precipitate is washed, filtered, and dried at 80-100°C to obtain a zinc-aluminum composite oxide powder. Deionized water, copper nitrate, citric acid and 25% ammonia water were used to prepare a complexing solution; The zinc-aluminum composite oxide powder is added to the complex solution by a double immersion method, and after sufficient stirring, ultrasonic treatment is performed, and the mixture is allowed to stand at room temperature for 10-12 hours, and then dried at 80-100° C., and finally calcined at a temperature of 300-350° C. for 2-4 hours to obtain a CuO / ZnO-Al2O3 composite oxide powder; The CuO / ZnO-Al2O3 composite oxide powder and graphite are fully ground and mixed, and then pressed into tablets to obtain a cylindrical catalyst; The catalyst comprises the following components by mass percentage: 5-10% CuO, 65-70% ZnO, and 25-30% Al2O3; Among them, Al2O3 doping of ZnO promotes the generation of more oxygen vacancies and the formation of surface heterogeneous structural defects in ZnO, the dispersion and adsorption of copper ammonia complex ions on the surface of the zinc-aluminum composite oxide powder, the interaction between CuO and the ZnO-Al2O3 composite support to modulate the reduction performance of CuO, and the appropriate amount of Cu + The presence of ions is beneficial to inhibiting the reverse water vapor shift reaction.

2. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: The alkaline solution includes at least one of ammonium bicarbonate solution, sodium carbonate solution, ammonium carbonate solution and ammonia water.

3. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: The concentration of the alkaline solution is 0.1-0.5 mol / L.

4. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: The soluble salt is any one of nitrate, sulfate and chloride.

5. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: The graphite accounts for 3-5% of the mass fraction of the CuO / ZnO-Al2O3 composite oxide powder.

6. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: During the grinding process of the cylindrical catalyst, the particles are 3*3mm or 5*5mm, and the mechanical strength is greater than 100N.

7. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 1, characterized in that: The catalyst is used in methanol steam reforming hydrogen production reaction.

8. The method for preparing a low-copper methanol reforming hydrogen production catalyst according to claim 7, characterized in that: The catalyst is used for methanol steam reforming to produce hydrogen, and the methanol steam reforming to produce hydrogen is carried out in a fixed bed or tubular reactor, including a reduction activation step and a hydrogen production reaction step: The operating conditions used in the reduction activation step are: temperature-programmed reduction activation under normal pressure and H2 atmosphere, activation temperature of 220-250°C, heating rate of 5-10°C / min, constant temperature time of 1-2h, hydrogen flow rate of 30-60 mL·min -1 ; After the reduction activation step, the hydrogen production step is carried out, and the operating conditions used are: the raw material is a mixture of water and methanol, the water-to-methanol molar ratio is 1.1-1.3, and the liquid hourly space velocity is 0.5-2h -1 , temperature is 220-300℃, and pressure is 0.1-2.0MPa.

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