A method for preparing a catalyst for dehydrogenation of an organic liquid

Abstract

The present invention is applicable to the field of organic liquid hydrogen storage technology and provides a method for preparing a catalyst for organic liquid dehydrogenation reactions. The specific steps include: preparing a dopamine solution containing a metal active component under air-tight conditions to obtain a catalyst precursor solution; pretreating a catalyst support; mixing the catalyst precursor solution and the pretreated catalyst support, exposing them to air, stirring and drying them thoroughly to obtain a catalyst precursor; and calcining the catalyst precursor to obtain a target catalyst. The target catalyst prepared by this method is applied to the catalytic dehydrogenation reaction of organic liquids, achieving excellent catalytic dehydrogenation performance, low production cost, high catalytic efficiency, and good stability.

Description

Technical Field

[0001] The invention belongs to the technical field of organic liquid hydrogen storage, and in particular relates to a method for preparing a catalyst for an organic liquid dehydrogenation reaction. Background Art

[0002] As a new energy source with high energy density, abundant sources, and virtually zero carbon emissions, hydrogen energy has broad application prospects. Therefore, its utilization is a key component in the transition from fossil fuels to clean energy. However, the fundamental issue currently hindering the large-scale commercial application of hydrogen energy is safe storage and transportation. Organic liquid hydrogen storage technology provides an effective solution to this problem.

[0003] Organic liquid hydrogen storage technology combines hydrogen with aromatic organic compounds through catalytic hydrogenation reactions to form saturated cyclic compounds with hydrogen bound to the molecules, thereby achieving the storage and transportation of hydrogen in liquid form at room temperature and pressure. The stored hydrogen is released through catalytic dehydrogenation reaction under the action of catalysts. The process is reversible, the reactants and products can be recycled, and the hydrogen storage capacity is relatively high (about 60-75kg H2 / m 3 , with a mass fraction of 6-8%) and is transported over long distances in the form of an organic liquid. Therefore, organic liquid hydrogen storage technology will play an important role in the safe storage and transportation of hydrogen energy.

[0004] Organic liquid hydrogen storage technology offers advantages in both storage density and ease of storage and transportation, but it also faces challenges in balancing catalyst efficiency and cost. The catalytic dehydrogenation process is both the core technology and a key challenge for organic liquid hydrogen storage.

[0005] Currently, noble metal catalysts, particularly supported Pt catalysts, are used as dehydrogenation catalysts in organic liquid hydrogen storage technology, particularly in the dibenzyltoluene / perhydrodibenzyltoluene system, due to their high dehydrogenation efficiency. However, noble metal catalysts are scarce and expensive, while cheaper non-noble metal catalysts have low dehydrogenation efficiency. Therefore, developing an efficient and stable dehydrogenation catalyst for organic liquid hydrogen storage media is key to the large-scale application of this technology. Summary of the Invention

[0006] The purpose of the embodiments of the present invention is to provide a method for preparing a catalyst for dehydrogenation of an organic liquid, aiming to solve the problems raised in the above background technology.

[0007] The embodiment of the present invention is achieved by a method for preparing a catalyst for dehydrogenation of an organic liquid, comprising the following steps:

[0008] Step 1: preparing a dopamine solution containing an active metal precursor in a certain proportion, wherein the pH of the solution is 8.5, and the solution preparation is carried out in an inert atmosphere;

[0009] Step 2: Prepare the catalyst carrier. The catalyst carrier needs to be fully dried before use, and the saturated water absorption capacity is measured;

[0010] Step 3: adding the dried catalyst support obtained in step 2 to the dopamine solution obtained in step 1, exposing the mixture to air and stirring thoroughly. After a period of reaction, the obtained solid is dried in a rotary evaporator to obtain a catalyst precursor.

[0011] Step 4: calcining the catalyst precursor obtained in step 3 to obtain the target catalyst.

[0012] A further technical solution is as follows: in step 1, the buffer used in the preparation process of the dopamine solution is a tris(hydroxymethyl)aminomethane buffer, the concentration of tris(hydroxymethyl)aminomethane is 0.1-1 mol / L, and the pH of the buffer is 8.5; the concentration of dopamine in the dopamine solution is 0.5-1.0 mol / L; the active metal precursor in the dopamine solution can be one or more water-soluble metal salts, or an acid (such as H2PtCl6, H2PdCl4), and its concentration is in the range of 1-5 mM.

[0013] In a further technical solution, the water-soluble metal salt is PtCl2, Pt(NO3)2, Cu(NO3)2 or Ni(NO3)2, etc.

[0014] According to a further technical solution, in step 2, the catalyst carrier may be a metal oxide (such as Al2O3, TiO2 and CeO2, etc.), a carbon material (such as carbon nanotubes and carbon nanofibers) and a molecular sieve (such as SBA-15 and ZSM-5, etc.).

[0015] According to a further technical solution, in step 3, the volume of the dopamine solution used is 1.2-2 times the saturated water absorption capacity of the catalyst support.

[0016] According to a further technical solution, in step 4, the catalyst precursor is calcined in air or an inert atmosphere at a temperature of 400-800° C. for 6-8 hours.

[0017] The present invention provides a method for preparing a catalyst for dehydrogenation of an organic liquid, which has the following beneficial effects:

[0018] (1) The active metal precursors are evenly anchored on the catalyst surface along with the polymerization of dopamine on the catalyst support surface, thereby avoiding uneven distribution caused by the migration of active components during the subsequent drying and calcination processes;

[0019] (2) The obtained catalyst has better catalytic activity and stability while reducing the Pt content. It has low production cost, high catalytic efficiency and good stability. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0022] An embodiment of the present invention provides a method for preparing a catalyst for an organic liquid dehydrogenation reaction, comprising the following steps:

[0023] Step 1: preparing a dopamine solution containing an active metal precursor in a certain proportion, wherein the pH of the solution is 8.5, and the solution preparation is carried out in an inert atmosphere;

[0024] Step 2: Prepare the catalyst carrier. The catalyst carrier needs to be fully dried before use, and the saturated water absorption capacity is measured;

[0025] Step 3: adding the dried catalyst support obtained in step 2 to the dopamine solution obtained in step 1, exposing the mixture to air and stirring thoroughly, and drying the obtained solid after a period of reaction to obtain a catalyst precursor;

[0026] Step 4: calcining the catalyst precursor obtained in step 3 to obtain the target catalyst.

[0027] As a preferred embodiment of the present invention, in step 1, the buffer used in the preparation of the dopamine solution is a tris(hydroxymethyl)aminomethane buffer, the concentration of tris(hydroxymethyl)aminomethane is 0.1-1 mol / L, and the pH of the buffer is 8.5; the concentration of dopamine in the dopamine solution is 0.5-1.0 mol / L; the active metal precursor in the dopamine solution can be one or more water-soluble metal salts, or an acid (such as H2PtCl6, H2PdCl4), and its concentration is in the range of 1-5 mM.

[0028] In an embodiment of the present invention, the water-soluble metal salt is PtCl2, Pt(NO3)2, Cu(NO3)2 or Ni(NO3)2, etc.

[0029] As a preferred embodiment of the present invention, in step 2, the catalyst carrier can be a metal oxide (such as Al2O3, TiO2 and CeO2, etc.), a carbon material (such as carbon nanotubes and carbon nanofibers) and a molecular sieve (such as SBA-15 and ZSM-5, etc.).

[0030] As a preferred embodiment of the present invention, in step 3, the volume of the dopamine solution used is 1.2-2 times the saturated water absorption capacity of the catalyst support.

[0031] As a preferred embodiment of the present invention, in step 4, the catalyst precursor is calcined in air or an inert atmosphere at a temperature of 400-800° C. for 6-8 hours.

[0032] The following provides a number of specific examples and comparative examples to verify the effectiveness of this method:

[0033] Example 1:

[0034] (1) Catalyst preparation:

[0035] Step 1: 45 mL of 0.5 mol / L Tris buffer (pH = 8.5) was measured and placed in a closed container. Nitrogen was then continuously introduced into the container. After 2 hours, 4.74 g of dopamine hydrochloride was added and stirred thoroughly. After the dopamine hydrochloride was completely dissolved, 5 mL of 73.5 mmol / L PtCl2 solution was added to prepare a catalyst precursor solution.

[0036] Step 2: Spherical alumina was selected as the catalyst carrier. 30 g of the alumina carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0037] Step 3: Mix the dried alumina support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water to finally obtain the target catalyst precursor.

[0038] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / Al 2 O 3 .

[0039] (2) Catalytic performance evaluation of catalyst:

[0040] The obtained catalyst 0.5% Pt / Al2O3 was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 The conversion rate of perhydrodibenzyltoluene was 90% and the selectivity was 98%.

[0041] Example 2:

[0042] (1) Catalyst preparation:

[0043] Step 1: 45 mL of 0.5 mol / L Tris buffer (pH = 8.5) was measured and placed in a closed container. Nitrogen was then continuously introduced into the container. After 2 hours, 4.74 g of dopamine hydrochloride was added and stirred thoroughly. After the dopamine hydrochloride was completely dissolved, 5 mL of 73.5 mmol / L PtCl2 solution was added to prepare a catalyst precursor solution.

[0044] Step 2: Spherical cerium oxide was selected as the catalyst carrier. 30 g of the cerium oxide carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 30 g.

[0045] Step 3: Mix the dried cerium oxide support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water to finally obtain the target catalyst precursor.

[0046] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / CeO 2 .

[0047] (2) Catalytic performance evaluation of catalyst:

[0048] The obtained catalyst 0.5% Pt / CeO2 was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 The conversion rate of perhydrodibenzyltoluene was 95% and the selectivity was 96%.

[0049] Example 3:

[0050] (1) Catalyst preparation:

[0051] Step 1: 45 mL of 0.5 mol / L Tris buffer (pH = 8.5) was measured and placed in a closed container. Nitrogen was then continuously introduced into the container. After 2 hours, 4.74 g of dopamine hydrochloride was added and stirred thoroughly. After the dopamine hydrochloride was completely dissolved, 5 mL of 73.5 mmol / L PtCl2 solution was added to prepare a catalyst precursor solution.

[0052] Step 2: Activated carbon was selected as the catalyst carrier. 30 g of the activated carbon carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0053] Step 3: Mix the dried activated carbon support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water, and finally obtain the target catalyst precursor.

[0054] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / C.

[0055] (2) Catalytic performance evaluation of catalyst:

[0056] The obtained catalyst 0.5% Pt / C was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 , conversion rate 88%, selectivity 95%.

[0057] Example 4:

[0058] (1) Catalyst preparation:

[0059] Step 1: Measure 45 mL of 0.5 mol / L tris (hydroxymethyl)aminomethane buffer (pH = 8.5) and place it in a closed container. Then, continuously introduce nitrogen into it. After 2 hours, add 4.74 g of dopamine hydrochloride and stir thoroughly. After the dopamine hydrochloride is completely dissolved, add 5 mL of 73.5 mmol / L PtCl2 solution. Finally, add 0.72 g of Cu(NO3)2 and dissolve it thoroughly to prepare a catalyst precursor solution.

[0060] Step 2: Spherical alumina was selected as the catalyst carrier. 30 g of the spherical alumina carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0061] Step 3: Mix the dried alumina support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water, and finally obtain the target catalyst precursor.

[0062] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt0.8% Cu / Al2O3.

[0063] 2) Catalytic performance evaluation of catalyst:

[0064] The obtained catalyst 0.5% Pt0.8% Cu / Al2O3 was used for the dehydrogenation of perhydrodibenzyltoluene at a reaction temperature of 300°C and a volume space velocity of 2.1 h -1 The conversion rate of perhydrodibenzyltoluene was 92% and the selectivity was 95%.

[0065] Comparative Example 1 (the difference between Comparative Example 1 and Example 1 is that dopamine was not used in the preparation of the catalyst):

[0066] (1) Catalyst preparation:

[0067] Step 1: 45 mL of 0.5 mol / L deionized water was placed in a container and 5 mL of a 73.5 mmol / L PtCl2 solution was added to prepare a catalyst precursor solution.

[0068] Step 2: Spherical alumina was selected as the catalyst carrier. 30 g of the alumina carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0069] Step 3: Mix the dried alumina support obtained in step 2 with the catalyst precursor solution prepared in step 1 and stir them thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water, and finally obtain the target catalyst precursor.

[0070] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / Al 2 O 3 .

[0071] (2) Catalytic performance evaluation of catalyst:

[0072] The obtained catalyst 0.5% Pt / Al2O3 was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 , the conversion rate of perhydrodibenzyltoluene is 70% and the selectivity is 85%.

[0073] Comparative Example 2 (the difference between Comparative Example 2 and Example 2 is that dopamine was not used in the preparation process of the catalyst):

[0074] (1) Catalyst preparation:

[0075] Step 1: 45 mL of deionized water was measured and placed in a container, and then 5 mL of a 73.5 mmol / L PtCl2 solution was added to prepare a catalyst precursor solution.

[0076] Step 2: Spherical cerium oxide was selected as the catalyst carrier. 30 g of the cerium oxide carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 30 g.

[0077] Step 3: Mix the dried cerium oxide support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water, and finally obtain the target catalyst precursor.

[0078] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / CeO 2 .

[0079] 2) Catalytic performance evaluation of catalyst:

[0080] The obtained catalyst 0.5% Pt / CeO2 was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 The conversion rate of perhydrodibenzyltoluene was 72% and the selectivity was 83%.

[0081] Comparative Example 3 (the difference between Comparative Example 3 and Example 3 is that dopamine was not used in the preparation process of the catalyst):

[0082] (1) Catalyst preparation:

[0083] Step 1: Measure 45 mL of deionized water and add 5 mL of a 73.5 mmol / L PtCl2 solution to prepare a catalyst precursor solution.

[0084] Step 2: Activated carbon was selected as the catalyst carrier. 30 g of the activated carbon carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0085] Step 3: Mix the dried activated carbon support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water, and finally obtain the target catalyst precursor.

[0086] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt / C.

[0087] (2) Catalytic performance evaluation of catalyst:

[0088] The obtained catalyst 0.5% Pt / C was used for the dehydrogenation reaction of perhydrodibenzyltoluene at a reaction temperature of 300 °C and a volume space velocity of 2.1 h -1 , conversion rate 65%, selectivity 80%.

[0089] Comparative Example 4 (the difference between Comparative Example 4 and Example 4 is that dopamine was not used in the preparation process of the catalyst):

[0090] (1) Catalyst preparation:

[0091] Step 1: Measure 45 mL of deionized water, add 5 mL of a 73.5 mmol / L PtCl2 solution, then add 0.72 g of Cu(NO3)2 and fully dissolve it to prepare a catalyst precursor solution.

[0092] Step 2: Spherical alumina was selected as the catalyst carrier. 30 g of the spherical alumina carrier was placed in a vacuum drying oven and dried thoroughly until the moisture was completely removed. The saturated water absorption was measured to be 35 g.

[0093] Step 3: Mix the dried alumina support obtained in step 2 with the catalyst precursor solution prepared in step 1, and expose the mixed system to the air and stir it thoroughly. After reacting for 2 hours, dry the mixed system to remove excess water to finally obtain the target catalyst precursor.

[0094] Step 4: calcining the catalyst precursor obtained in step 3 at 500° C. for 6 hours to obtain the target catalyst 0.5% Pt0.8% Cu / Al2O3.

[0095] (2) Catalytic performance evaluation of catalyst:

[0096] The obtained catalyst 0.5% Pt0.8% Cu / Al2O3 was used for the dehydrogenation of perhydrodibenzyltoluene at a reaction temperature of 300°C and a volume space velocity of 2.1 h -1 The conversion rate of perhydrodibenzyltoluene was 68% and the selectivity was 85%.

[0097] The experimental results of each embodiment and each comparative example are shown in the following table:

[0098] Table 1 Experimental results

[0099] Conversion rate (%) Selectivity (%) Example 1 90 98 Example 2 95 96 Example 3 88 95 Example 4 92 95 Comparative Example 1 70 85 Comparative Example 2 72 83 Comparative Example 3 65 80 Comparative Example 4 68 85

[0100] As can be seen from the table, a comparison between Examples 1-4 and Comparative Examples 1-4 shows that the catalytic performance of the monometallic and bimetallic supported catalysts obtained by the preparation method proposed in the present invention in the dehydrogenation reaction of perhydrodibenzyltoluene is better than that of the preparation method without using dopamine.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for dehydrogenation of an organic liquid, characterized in that: The following steps are involved: Step 1: preparing a dopamine solution containing an active metal precursor in a proportioned manner, wherein the pH of the solution is 8.5 and the solution preparation is carried out in an inert atmosphere; Step 2: Prepare the catalyst carrier. The catalyst carrier needs to be fully dried before use, and the saturated water absorption capacity is measured; Step 3: adding the dried catalyst support obtained in step 2 to the dopamine solution obtained in step 1, exposing the mixture to air and stirring thoroughly, drying the solid obtained after the reaction, and then obtaining a catalyst precursor; Step 4: calcining the catalyst precursor obtained in step 3 to obtain the target catalyst.

2. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 1, wherein: In step 1, the buffer used in the preparation of the dopamine solution is tris(hydroxymethyl)aminomethane buffer, the concentration of tris(hydroxymethyl)aminomethane is 0.1-1 mol / L, and the pH of the buffer is 8.5; the concentration of dopamine in the dopamine solution is 0.5-1.0 mol / L; the active metal precursor in the dopamine solution is one or more water-soluble metal salts or acids, and its concentration is in the range of 1-5 mM.

3. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 2, wherein: The metal water-soluble salt is PtCl2, Pt(NO3)2, Cu(NO3)2 or Ni(NO3)2.

4. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 2, wherein: The acid is H2PtCl6 or H2PdCl4.

5. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 1, wherein: In step 2, the catalyst carrier is a metal oxide, a carbon material or a molecular sieve.

6. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 5, wherein: The metal oxide is Al2O3, TiO2 or CeO2.

7. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 5, wherein: The carbon material is carbon nanotube or carbon nanofiber.

8. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 5, wherein: The molecular sieve is ZSM-5.

9. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 2, wherein: In step 3, the volume of the dopamine solution used is 1.2-2 times the saturated water absorption capacity of the catalyst support.

10. The method for preparing a catalyst for dehydrogenation of an organic liquid according to claim 1, wherein: In step 4, the catalyst precursor is calcined in air or an inert atmosphere at a temperature of 400-800° C. for 6-8 hours.