A copper-based reverse phase catalyst for hydrogen production from methanol, and its preparation method and application

Abstract

The present invention relates to a copper-based reverse phase catalyst for hydrogen production from methanol and a preparation method and application thereof. The copper-based reverse phase catalyst comprises metal copper particles and oxides dispersed on their surfaces, wherein the metal copper particles are obtained from copper oxide prepared by a precipitation method; wherein the content of the oxide is 5 to 40 wt%, the oxide includes but is not limited to at least one of MgO, Al2O3, SiO2, K2O, CaO, MnO2, TiO2, Fe2O3, Co2O3, NiO, ZnO, Ga2O3, La2O3, CeO2, Y2O3 and ZrO2, and the oxide is loaded onto the surface of the copper oxide particles by an impregnation method. The metal catalyst provided by the present invention has a non-traditional supported reverse phase structure, that is, the oxide is dispersed on the surface of the metal copper particles, and has excellent catalytic activity when applied to the methanol process, and exhibits a higher conversion rate than traditional supported catalysts, is suitable for industrial production, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the field of methanol hydrogen production, and in particular to a copper-based reverse phase catalyst for methanol hydrogen production, and a preparation method and application thereof. Background Art

[0002] Today, as global energy consumption increases dramatically, environmental problems caused by the extensive use of fossil energy are becoming more and more serious, and it is urgent to find and develop clean energy. Among them, hydrogen is a secondary energy source that can effectively convert energy without emitting greenhouse gases and harmful substances. Therefore, hydrogen can be used as an ideal clean energy source, especially in fuel cell vehicles. At the same time, hydrogen is also an important chemical raw material. The development and utilization of hydrogen energy has become one of the main trends in current energy research and development. At present, hydrogen storage technology is the main difficulty restricting the development of hydrogen energy. The storage and transportation of traditional hydrogen cylinders are not only unsafe, but also costly, and it is difficult to supply a large amount of hydrogen demand. Based on this, organic hydrogen storage materials, as a new type of hydrogen storage container, can be used in fuel cell vehicles through in-situ hydrogen production. Among them, methanol has the advantages of low price, high hydrogen mass density, easy storage and transportation, and low reforming temperature. It is a hydrogen storage material with great application prospects. Nobel Prize winner George Andrew Olah also proposed the concept of "methanol economy". In summary, the use of methanol in situ hydrogen production as an energy source for fuel cell vehicles is highly feasible, and related research has received increasing attention from academia and industry. Studies have shown that methanol in situ hydrogen supply is generally carried out at a low temperature of 200~300 ℃, with a high hydrogen yield and a low yield of byproduct CO. At present, the main research and application is mainly based on supported copper-based catalysts. The structure of the catalyst uses ZnO, CeO2, ZrO2 and Al2O3 as carriers, and copper nanoparticles dispersed on the surface as active metals. The carrier is the main component of the catalyst, and a small part is active metal copper. Traditional supported copper-based catalysts are greatly affected by the properties of the carrier. The nanometer size and electronic structure of the copper particles dispersed on the surface are not the same, and the activity varies greatly. At present, the development and design of copper-based reverse catalysts for methanol are limited. The reverse catalyst uses copper oxide as the main component of the catalyst, and a small amount of oxide is dispersed on the surface of the copper oxide particles as a modification. Studies have shown that some oxides show better activity and stability in reverse copper-based catalysts. Therefore, there is an urgent need in this field to expand the design and optimization of the copper-based reverse phase catalyst structure while maintaining activity. Summary of the invention

[0003] The purpose of the present invention is to provide a copper-based reverse catalyst for hydrogen production from methanol and its preparation method and application in order to overcome the limitations of the above-mentioned existing preparation methods. The present application uses sodium citrate as a chelating agent and sodium hydroxide as a precipitant to prepare a CuO carrier, and loads the oxide to the CuO surface by an impregnation method to prepare a methanol hydrogen production catalyst. By uniformly dropping sodium hydroxide solution into a mixed solution of sodium citrate and copper nitrate, after precipitation aging, after suction filtration, drying, grinding, and calcination, a CuO carrier is obtained. Subsequently, a certain amount of CuO is added to a salt solution of the corresponding oxide, and after ultrasound, drying, grinding, and calcination, the final catalyst is obtained. By dispersing MO on the surface of the CuO carrier, a new catalyst structure is synthesized, which improves the activity of the original supported copper-based catalyst.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The copper-based reverse phase catalyst for methanol hydrogen production in the present invention is a supported copper-based catalyst of M / Cu composite oxide, wherein the content of M oxide in the M / Cu composite oxide is 5-40wt%. The preparation sequence and the content of M oxide in the present application are the key to achieving the technical effect. During the specific implementation, attention should be paid to the control of the nitrate precursor of M oxide dispersed on the CuO surface and the content of M oxide, otherwise an ideal catalyst structure is prepared and an ideal conversion rate is achieved.

[0006] Further preferably, the mass fraction of M oxide in the M / Cu composite oxide is 10-20wt%, and the optimal performance data can be obtained at this point value during specific implementation. Further, Cu in the M / Cu composite oxide is used as the main active component and carrier, M is a doped metal oxide, and the catalyst in the present application is an inverse structure of oxides dispersed on the surface of Cu particles. The inverse structure of the catalyst has an important influence on the structure-activity relationship of the overall catalyst.

[0007] The method for preparing a copper-based reverse phase catalyst for producing hydrogen from methanol in the present invention comprises the following steps:

[0008] S1: dissolving copper metal salt and citrate in an aqueous solution and mixing them to obtain solution A;

[0009] S2: adding sodium hydroxide aqueous solution to solution A, mixing evenly, stirring, and obtaining suspension B;

[0010] S3: Filter, wash and dry the suspension B to obtain solid C;

[0011] S4: Grind solid C into powder, and then calcine at 400-500 °C for 3-5 h to obtain solid D;

[0012] S5: dissolving the metal salt in the aqueous solution to obtain solution E;

[0013] S6: adding solid D to solution E, mixing evenly, sonicating, and drying to obtain solid F;

[0014] S7: Grind the solid F into powder, and then calcine it at 400-500°C for 3-5 h to obtain a finished catalyst.

[0015] Furthermore, the copper metal salt in S1 is nitrate, the citrate is sodium citrate, and the molar ratio of the citrate to the copper metal salt is 1:1.

[0016] Furthermore, the volume ratio of the added sodium hydroxide aqueous solution in S2 to the volume of solution A is 1:4, and the stirring time is 3 hours.

[0017] Furthermore, the metal salt in S5 is a nitrate of the corresponding oxide metal.

[0018] The application of the copper-based reverse phase catalyst in methanol in the present invention has the following specific reaction conditions: at a reaction temperature of 200-250° C. and a reaction pressure of normal pressure, the copper-based reverse phase catalyst is used to catalytically convert the reaction gas into hydrogen.

[0019] Furthermore, the reaction gas is a mixed gas consisting of methanol, water and an inert gas, and the molar ratio of methanol to water in the reaction gas is 1:1-10.

[0020] Furthermore, the copper-based reverse phase catalyst is activated with a reaction gas for 1 to 2 h before the reaction, and the activation temperature is 250 to 300 °C.

[0021] Compared with the prior art, the present invention has the following technical advantages:

[0022] The copper-based reverse catalyst synthesized in the present invention introduces a specific amount of magnesium (5-40wt%), which is dispersed on the surface of copper particles to form a specific reverse structure, so that the methanol conversion rate of the M / Cu catalyst is higher than the conversion rate when the traditional oxide is used as a carrier at the same temperature. The methanol conversion rate is increased by dozens of times, overcoming the bottleneck of the activity of the supported oxide in the existing catalytic system. The reverse structure of the specific oxide dispersed on the surface of the copper particles in the present invention greatly improves the activity of the supported oxide on the copper particles, breaking through the limitations of the traditional catalyst design and preparation structure.

[0023] The catalyst of the present invention is prepared by a precipitation method to complete the preparation of nano copper particles, and then the oxide is loaded on the surface of the copper particles by an impregnation method. The method is simple and has strong applicability. Under the conditions of specific oxides and loading amounts, the optimal microscopic configuration effect can be achieved. The overall synthesis steps are simple, the conditions are mild, and the controllability is strong, and it can be applied to large-scale industrial production. Implementation

[0024] Example 1

[0025] Sodium citrate was used as a chelating agent and sodium hydroxide as a precipitant to prepare a CuO carrier, and a methanol hydrogen production catalyst was prepared by loading MgO by an impregnation method. The CuO carrier was obtained by uniformly dropping sodium hydroxide solution into a mixed solution of sodium citrate and copper nitrate, precipitating and aging, filtering, drying, grinding, and calcining. Subsequently, a certain amount of CuO was added to a magnesium nitrate solution, and the final catalyst was obtained after ultrasonication, drying, grinding, and calcining. By dispersing MgO on the surface of the CuO carrier, a new catalyst structure was synthesized, which improved the activity of the original supported copper-based catalyst.

[0026] In this example, a 5MgO / Cu catalyst was prepared, and the mass content of MgO was 5 wt %.

[0027] Preparation process:

[0028] S1: Dissolve 4.832 g Cu(NO3)2·3H2O and 5.882 g sodium citrate dihydrate in 320 mL deionized water and stir them evenly by magnetic stirring;

[0029] S2: Add 160 mL of 1M sodium hydroxide solution to the solution obtained in step S1;

[0030] S3: The mixture obtained in step S2 is stirred and aged for 3 h;

[0031] S4: The mixture obtained in step S3 is filtered and washed with 5 L of water;

[0032] S5: Put the solid obtained in step S4 into an oven for 12 hours at a temperature set at 60°C;

[0033] S6: grinding the solid obtained in step S5 into powder, and calcining in a muffle furnace at 400-500° C. for 3-5 h;

[0034] S7: Take 1 g of the solid obtained in step S6, add it into a solution containing 0.3349 g of Mg(NO3)2·6H2O and stir evenly;

[0035] S8: The solid obtained in step S7 is ultrasonicated for 30 min, and then placed in an oven for 12 h, with the temperature set at 100°C;

[0036] S9: Grind the solid obtained in step S8 into powder, and calcine it in a muffle furnace at 400-500° C. for 3-5 hours to obtain a final product.

[0037] Testing process:

[0038] Catalyst evaluation process:

[0039] S1: The prepared catalyst is placed in a stainless steel tubular reactor. Methanol and aqueous solution enter the preheater through a micro-injection pump and are then brought into the reactor with inert gas N2. The outlet gas passes through a condenser and enters the online chromatographic analysis.

[0040] S2: Open the valve, introduce hydrogen, heat the reactor to 250°C~300°C, and activate for 1~2h.

[0041] S3: Adjust the reaction temperature and detect the gas phase product composition every 30 minutes under steady state.

[0042] The performance test of the catalyst in this experiment was carried out in a fixed bed reaction. The application process of the catalyst for methanol hydrogen production process was as follows: 50 mg of the catalyst was weighed, and a 50% hydrogen and nitrogen mixture was introduced at 30 mL / min at normal pressure and 300 ° C for 2 h before the catalyst performance test was carried out. The reaction temperature was 250 ° C, and the feed space velocity was 10.56 h -1 The reaction results are shown in Table 1.

[0043] Embodiment 2~6

[0044] The preparation process of the above embodiment is the same as that of embodiment 1, except that the MgO contents are 10wt%, 15wt%, 20wt%, 30wt% and 40wt% respectively.

[0045] The test results show that when the MgO content is 10wt%, the catalyst exhibits the best activity, and methanol is nearly fully converted under this test condition. As the MgO content increases, the activity decreases, indicating that there is an optimal content. The high activity of the catalyst makes it possible to use it in fuel cells.

[0046] Embodiments 7 to 21

[0047] The preparation process of the above embodiment is the same as that of Example 1, except that the oxide content is 10wt% and the oxides are Al2O3, SiO2, K2O, CaO, MnO2, TiO2, Fe2O3, Co2O3, NiO, ZnO, Ga2O3, La2O3, CeO2, Y2O3 and ZrO2.

[0048] Comparative Example 1

[0049] This comparative example is the preparation of 5Cu / MgO catalyst, and the MgO mass content is 95%

[0050] Preparation process:

[0051] S1: Add 1 g of commercial MgO to a solution containing 0.1901 g of Cu(NO3)2·3H2O and stir well;

[0052] S2: The slurry obtained in step S1 was ultrasonicated for 30 min, and then placed in an oven for 12 h at a temperature set at 100°C;

[0053] S3: Grind the solid obtained in step S2 into powder, and calcine it in a muffle furnace at 400-500° C. for 3-5 hours to obtain the final product.

[0054] Testing process:

[0055] The performance test of the catalyst in this experiment was carried out in a fixed bed reaction. The application process of the catalyst for methanol hydrogen production process was as follows: 50 mg of the catalyst was weighed, and a 50% hydrogen and nitrogen mixture was introduced at 30 mL / min at normal pressure and 300 ° C for 2 h before the catalyst performance test was carried out. The reaction temperature was 250 ° C, and the feed space velocity was 10.56 h -1 The reaction results are shown in Table 1.

[0056] Comparative Examples 2 to 6

[0057] The preparation process of the above comparative examples is the same as that of comparative example 1, except that the MgO contents are 90wt%, 85wt%, 80wt%, 70wt% and 60wt% respectively.

[0058] Comparative Examples 7 to 21

[0059] The preparation process of the above comparative example is the same as that of comparative example 1, except that the oxides are the oxides in the corresponding embodiments, and the mass content of the oxides is 90%.

[0060] The test results show that the traditional supported catalysts prepared with oxides as carriers, except for a few oxides such as MgO, Al2O3 and Ga2O3, all show poor methanol conversion rates. However, the reversed-phase catalysts with oxides dispersed on the surface of copper particles all show high methanol conversion rates, confirming the special role of the reversed-phase structure in methanol applications.

[0061] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

[0062]

Claims

1. Application of a copper-based reverse phase catalyst in hydrogen production by methanol steam reforming, characterized in that: The copper-based reverse phase catalyst is a MgO / Cu composite oxide, wherein MgO is dispersed on the surface of Cu particles; the methanol steam reforming hydrogen production reaction is carried out at a reaction temperature of 200 to 250° C., a reaction pressure of normal pressure, and a feed space velocity of 10.56 h -1 Under the conditions of , the reaction gas is converted into hydrogen, wherein the reaction gas is a mixed gas consisting of methanol, water and an inert gas; the preparation method of a copper-based reverse phase catalyst for hydrogen production by methanol steam reforming is characterized by comprising the following steps: S1: dissolving copper metal salt and citrate in an aqueous solution and mixing them to obtain solution A; S2: adding sodium hydroxide aqueous solution to solution A, mixing evenly, stirring, and obtaining suspension B; S3: Filter, wash and dry the suspension B to obtain solid C; S4: Grind the solid C into powder, and then calcine at 400-500° C. for 3-5 h to obtain a solid D; S5: dissolving the metal salt in the aqueous solution to obtain solution E; S6: adding solid D to solution E, mixing evenly, sonicating, and drying to obtain solid F; S7: Grind the solid F into powder, and then calcine at 400-500° C. for 3-5 hours to obtain a finished catalyst.

2. The use of a copper-based reverse phase catalyst in hydrogen production by methanol steam reforming according to claim 1, characterized in that: The mass fraction of MgO in the MgO / Cu is 5-40%.

3. The use of a copper-based reverse phase catalyst in hydrogen production by methanol steam reforming according to claim 1, characterized in that: The molar ratio of methanol to water in the reaction gas is 1:

1.

4. The use of a copper-based reverse phase catalyst in hydrogen production by methanol steam reforming according to claim 1, characterized in that: The copper-based reverse phase catalyst is activated with reaction gas for 1 to 2 hours before the reaction, and the activation temperature is 250 to 300°C.

5. According to claim 1, the use of a copper-based reverse phase catalyst in methanol steam reforming to produce hydrogen, wherein the copper metal salt in S1 is copper nitrate, the citrate is sodium citrate, and the molar ratio of the citrate to the copper metal salt is 1:

1.

6. According to claim 1, the use of a copper-based reverse phase catalyst in methanol steam reforming to produce hydrogen, the volume ratio of the added sodium hydroxide aqueous solution in S2 to the volume of solution A is 1:4, and the stirring time is 3 hours.

7. Use of a copper-based reverse phase catalyst in methanol steam reforming to produce hydrogen according to claim 1, wherein the metal salt in S5 is magnesium nitrate.

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