Process for the preparation of platinum-based manganese-titania catalysts for the dehydrogenation of methylcyclohexane

Abstract

The application discloses a preparation method of a methylcyclohexane dehydrogenation catalyst Pt-based manganese-titania, and specifically comprises the following steps: step 1, preparing Mn-TiO2 powder; and step 2, preparing a Pt / Mn-TiO2 catalyst according to the product obtained in step 1. In the application, Mn is doped in the crystal lattice of TiO2 to form Mn-TiO2, and then Pt catalytic active centers are further introduced to improve catalytic activity, so that the hydrogenation / dehydrogenation dual-effect function can be realized, and the hydrogen purification rate is improved.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy storage technology and relates to a method for preparing a platinum-based manganese-titanium dioxide catalyst for methylcyclohexane dehydrogenation. Background Technology

[0002] Hydrogen, due to its high gravimetric energy density, low volumetric energy density, and flammability and explosiveness, can help facilitate the large-scale absorption of renewable energy, achieve large-scale peak shaving of the power grid, and enable cross-seasonal and cross-regional energy storage, thus accelerating the decarbonization of industries, buildings, and transportation. Therefore, finding efficient, low-cost, and scalable hydrogen storage methods has become crucial.

[0003] Methylcyclohexane possesses high hydrogen storage density: a mass hydrogen storage density of 6.1 wt% and a volumetric hydrogen storage density of 47 kg / m³. 3 This has gradually attracted widespread attention. Methylcyclohexane hydrogen storage is a reversible cyclic process. Since the hydrogenation process involves a decrease in Gibbs free energy with a very large absolute value, it is thermodynamically very favorable, meaning the hydrogenation process is very easy to carry out. However, the dehydrogenation process is a strongly endothermic reaction, making it more difficult to proceed and requiring a catalyst to lower the reaction barrier. Platinum (Pt) metal, due to its suitable number of d-orbital electrons, exhibits excellent catalytic activity for hydrogen production when supported on oxides. Titanium (Ti) oxides stand out among many oxides due to their large reserves, low price, non-toxicity, and environmental friendliness. Manganese (Mn) metal can increase its active centers and improve the Pt loading, significantly enhancing the catalytic effect on methylcyclohexane. Therefore, Pt / Mn-TiO2 supported catalysts have great application prospects in the field of hydrogen production. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a platinum-based manganese-titanium dioxide catalyst for the dehydrogenation of methylcyclohexane. The catalyst prepared by this method can achieve a dual function of hydrogenation / dehydrogenation, thereby improving the hydrogen purification rate.

[0005] The technical solution adopted in this invention is a method for preparing a platinum-based manganese-titanium dioxide catalyst for the dehydrogenation of methylcyclohexane, specifically including the following steps:

[0006] Step 1: Prepare Mn-TiO2 powder;

[0007] Step 2: Prepare a Pt / Mn-TiO2 catalyst based on the product obtained in Step 1.

[0008] The invention is further characterized by:

[0009] The specific process of step 1 is as follows:

[0010] Step 1.1: Take 0.88g-1.0g of terephthalic acid powder, 1.5mL-2mL of methanol solution and 10-13.5mL of N,N-dimethylformamide solution and put them into a beaker. Stir magnetically at 300rpm-450rpm for 30min-40min. Then add 0.525mL-1.05mL of tetrabutyl titanate and 0.005g-0.01g of potassium permanganate. Stir magnetically at 300rpm-450rpm for 30min-40min. Pour the mixture into a reaction vessel and react at 140℃-150℃ for 16h-20h to obtain a suspension.

[0011] Step 1.2: Centrifuge the suspension obtained in Step 1.1, then add excess methanol and let it stand for 12-15 hours. Then dry it overnight in an oven to obtain Mn-TiO2 powder.

[0012] In step 1.2, the suspension is centrifuged at a speed of 8500 rpm to 10000 rpm for a time of 15 min to 30 min.

[0013] The specific process of step 2 is as follows:

[0014] Take 1g to 1.5g of the Mn-TiO2 powder prepared in step 1 and disperse it in 10mL to 11.5mL of deionized water. Add 0.09g to 0.15g of platinum nitrate and rotate it in a closed shaker at 150rpm / min to 200rpm / min for 12h to 15h at 30℃ to 50℃. Then, dry it in an oven at 60℃ to 65℃ for 10h to 12h. After cooling to room temperature, reduce it by passing H2 through it in a tube furnace at 300℃ to 350℃ for 3h to 5h to finally obtain the Pt / Mn-TiO2 catalyst.

[0015] The process of Pt / Mn-TiO2 catalyzing the production of hydrogen from methylcyclohexane is as follows: 0.15 g to 0.2 g of Pt / Mn-TiO2 catalyst is stirred evenly with 1.5 g to 2 g of quartz sand and then placed in a catalytic fixed bed. The gasification furnace temperature is 130℃ to 135℃, the reaction furnace temperature is 370℃ to 380℃, the heating zone temperature is 135℃ to 140℃, the gas flow rate is 15 mL / min to 30 mL / min, the pressure is 0.3 MPa to 0.6 MPa, the methylcyclohexane injection rate is 0.03 mL / min to 0.05 mL / min, and the catalytic reaction temperature is 350℃ to 380℃.

[0016] The beneficial effects of this invention are that the preparation method of the platinum-based manganese-titanium dioxide catalyst for methylcyclohexane dehydrogenation of this invention involves doping Mn into the lattice of TiO2 to form Mn-TiO2, and further introducing Pt catalytic active centers to improve catalytic activity, thereby achieving a dual function of hydrogenation / dehydrogenation and improving the hydrogen purification rate. Attached Figure Description

[0017] Figure 1 The image shows the XRD pattern of Mn-TiO2 prepared by the preparation method of the platinum-based manganese-titanium dioxide catalyst of the present invention, which is TiO2.

[0018] Figure 2 This is a graph showing the catalytic performance of the Pt / Mn-TiO2 catalyst prepared in Example 1 of the preparation method of the platinum-based manganese-titanium dioxide catalyst for methylcyclohexane dehydrogenation of the present invention for methylcyclohexane dehydrogenation. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] The preparation method of the platinum-based manganese dioxide (Mn-TiO2) catalyst for methylcyclohexane dehydrogenation of the present invention specifically includes the following steps:

[0021] 1) Preparation of Mn-TiO2

[0022] Take 0.88g-1.0g of terephthalic acid powder, 1.5mL-2mL of methanol solution, and 10mL-13.5mL of N,N-dimethylformamide (DMF) solution and put them into a 20mL beaker. Stir magnetically at 300rpm-450rpm for 30min-40min at room temperature. Then add 0.525-1.05mL of tetrabutyl titanate and 0.005-0.01g of potassium permanganate. Stir magnetically at 300rpm-450rpm for 30min at room temperature. Pour the mixture into a 25mL reaction vessel and react at 140℃-150℃ for 16h-20h to obtain a suspension. The suspension was centrifuged at 8500 rpm to 10000 rpm for 15 to 30 minutes, and excess methanol was added. The suspension was then left to stand for 12 to 15 hours and then dried overnight in an oven at 80 to 85 degrees Celsius to obtain a pale yellow powder of Mn-TiO2.

[0023] 2) Mn-TiO2 loaded Pt

[0024] Take 1g to 1.5g of the prepared Mn-TiO2 powder and disperse it in 10mL to 11.5mL of deionized water. Add 0.09g to 0.15g of platinum nitrate (Pt content 18.02%). Rotate the mixture in a closed shaker at 150rpm / min to 200rpm / min for 12h to 15h at 30℃ to 50℃. Then, dry the mixture in an oven at 60℃ to 65℃ for 10h to 12h. After cooling to room temperature, reduce the mixture by passing H2 through it in a tube furnace at 300℃ to 350℃ for 3h to 5h to finally obtain the Pt / Mn-TiO2 catalyst.

[0025] 3) Performance of Pt / Mn-TiO2 catalyzing hydrogen production from methylcyclohexane

[0026] After mixing 0.15g–0.2g of Pt / Mn-TiO2 catalyst with 1.5g–2g of quartz sand, the mixture was placed in a high-pressure catalytic fixed bed. The gasifier temperature was 130℃–135℃, the reactor temperature was 370℃–380℃, the heating zone temperature was 135℃–140℃, the gas flow rate was 15–30mL / min, the pressure was 0.3–0.6MPa, the methylcyclohexane injection rate was 0.03–0.05mL / min, and the catalytic reaction temperature was 350–380℃.

[0027] Example 1

[0028] 1) Preparation of Mn-TiO2

[0029] 0.88 g of terephthalic acid powder, 1.5 mL of methanol solution, and 13.5 mL of LDM solution were placed in a 20 mL beaker and magnetically stirred at 300 rpm for 30 min at room temperature. Then, 0.525 mL of tetrabutyl titanate and 0.005 g of potassium permanganate were added, and the mixture was magnetically stirred at 300 rpm for 30 min at room temperature. The mixture was then poured into a 25 mL reaction vessel and reacted at 150 °C for 16 h to obtain a suspension. The suspension was centrifuged at 10,000 rpm for 15 min, and excess methanol was added. The mixture was then left to stand for 12 h and dried overnight at 80 °C to obtain a pale yellow Mn-TiO2 powder.

[0030] 2) Mn-TiO2 loaded Pt

[0031] 1 g of the prepared Mn-TiO2 substrate was dispersed in 10 mL of deionized water, and 0.09 g of platinum nitrate was added. The mixture was then thawed at 150 r / min for 12 h in a closed shaker at 30 °C. After drying in an oven at 60 °C for 12 h, the mixture was cooled to room temperature and then reduced by H2 in a tube furnace at 350 °C for 3 h to finally obtain the Pt / Mn-TiO2 catalyst.

[0032] 3) Performance of Pt / Mn-TiO2 catalyzing hydrogen production from methylcyclohexane

[0033] After mixing 0.15g of Pt / Mn-TiO2 catalyst with 1.5g of quartz sand, the mixture was placed in a high-pressure catalytic fixed bed. The gasifier temperature was 130℃, the reactor temperature was 380℃, the heating zone temperature was 135℃, the gas flow rate was 15mL / min, the pressure was 0.3MPa, the methylcyclohexane injection rate was 0.03mL / min, and the catalytic reaction temperature was 380℃.

[0034] Figure 1This is the XRD pattern of TiO2 and Mn-TiO2 prepared by the method of preparing platinum-based manganese-titanium dioxide for the dehydrogenation of methylcyclohexane of this invention, as described in Example 1. Figure 1 As can be seen, using the method of Example 1, manganese was successfully incorporated into the TiO2 lattice in the form of oxides.

[0035] Figure 2 This is a graph showing the catalytic performance of the Pt / Mn-TiO2 catalyst prepared in Example 1 of the preparation method of the platinum-based manganese-titanium dioxide catalyst for methylcyclohexane dehydrogenation of this invention for the dehydrogenation of methylcyclohexane. Figure 2 It can be seen that the catalyst prepared in Example 1 exhibits good catalytic stability in terms of hydrogen volume ratio during the 10-hour catalytic dehydrogenation reaction of methylcyclohexane. If methanol is not added in step 1 and the amount of DMF is too small, the lack of presolvent leads to poor centrifugation effect and uneven reaction of catalyst components, resulting in poor catalyst stability and low hydrogen conversion rate. If tetrabutyl titanate and potassium permanganate are used in excess in step 1, the hydrogen conversion rate will also decrease significantly. This is because excess tetrabutyl titanate and potassium permanganate prevent the three template solvents of terephthalic acid, methanol, and DMF from reacting efficiently, which is detrimental to the adsorption-desorption of the support during the methylcyclohexane catalysis process.

[0036] Example 2

[0037] 1) Preparation of Mn-TiO2

[0038] 1.0 g of terephthalic acid powder, 2 mL of methanol solution, and 10 mL of DMF solution were placed in a 20 mL beaker and magnetically stirred at 450 rpm for 40 min at room temperature. Then, 1.05 mL of tetrabutyl titanate and 0.01 g of potassium permanganate were added, and the mixture was magnetically stirred at 450 rpm for 40 min at room temperature. The mixture was then poured into a 25 mL reaction vessel and reacted at 140 °C for 20 h to obtain a suspension. The suspension was centrifuged at 8500 rpm for 30 min, and excess methanol was added. The mixture was then allowed to stand for 15 h and dried overnight at 85 °C to obtain a pale yellow powder of Mn-TiO2.

[0039] 2) Mn-TiO2 loaded Pt

[0040] 1.5g of the prepared Mn-TiO2 powder was dispersed in 11.5mL of deionized water, and 0.15g of platinum nitrate was added. The mixture was then thawed at 200r / min for 15h in a closed shaker at 50℃. After drying in an oven at 65℃ for 10h, the mixture was cooled to room temperature and then reduced by H2 in a tube furnace at 300℃ for 5h to finally obtain the Pt / Mn-TiO2 catalyst.

[0041] 3) Performance of Pt / Mn-TiO2 catalyzing hydrogen production from methylcyclohexane

[0042] After mixing 0.2g of Pt / Mn-TiO2 catalyst with 2g of quartz sand, the mixture was placed in a high-pressure catalytic fixed bed. The gasifier temperature was 135℃, the reactor temperature was 370℃, the heating zone temperature was 140℃, the gas flow rate was 30mL / min, the pressure was 0.6MPa, the methylcyclohexane injection rate was 0.05mL / min, and the catalytic reaction temperature was 350℃.

[0043] Example 3

[0044] 1) Preparation of Mn-TiO2

[0045] 0.98 g of terephthalic acid powder, 1.8 mL of methanol solution, and 12 mL of DMF solution were placed in a 20 mL beaker and magnetically stirred at 400 rpm for 35 min at room temperature. Then, 0.875 mL of tetrabutyl titanate and 0.008 g of potassium permanganate were added, and the mixture was magnetically stirred at 400 rpm for 35 min at room temperature. The mixture was then poured into a 25 mL reaction vessel and reacted at 145 °C for 18 h to obtain a suspension. The suspension was centrifuged at 9000 rpm for 25 min, and excess methanol was added. The mixture was then allowed to stand for 13 h and dried overnight at 82 °C to obtain a pale yellow Mn-TiO2 powder.

[0046] 2) Mn-TiO2 loaded Pt

[0047] 1.2g of the prepared Mn-TiO2 powder was dispersed in 11mL of deionized water, and 0.12g of platinum nitrate was added. The mixture was then thawed at 180r / min for 13h in a closed shaker at 40℃. After drying in an oven at 62℃ for 11h, the mixture was cooled to room temperature and then reduced by H2 in a tube furnace at 320℃ for 4h to finally obtain the Pt / Mn-TiO2 catalyst.

[0048] 3) Performance of Pt / Mn-TiO2 catalyzing hydrogen production from methylcyclohexane

[0049] After mixing 0.18g of Pt / Mn-TiO2 catalyst with 1.8g of quartz sand, the mixture was placed in a high-pressure catalytic fixed bed. The gasifier temperature was 132℃, the reactor temperature was 375℃, the heating zone temperature was 138℃, the gas flow rate was 20mL / min, the pressure was 0.5MPa, the methylcyclohexane injection rate was 0.04mL / min, and the catalytic reaction temperature was 370℃.

Claims

1. A method for preparing a platinum-based manganese-titanium dioxide catalyst for the dehydrogenation of methylcyclohexane, characterized in that: Specifically, the steps include the following: Step 1, preparing Mn-TiO2 powder; the specific process of step 1 is as follows: Step 1.1: Take 0.88g-1.0g of terephthalic acid powder, 1.5mL-2mL of methanol solution, and 10-13.5mL of N,N-dimethylformamide solution and put them into a beaker. Stir magnetically at 300rpm-450rpm for 30min-40min. Then add 0.525mL-1.05mL of tetrabutyl titanate and 0.005g-0.01g of potassium permanganate. Stir magnetically at 300rpm-450rpm for 30min-40min. Pour the mixture into a reaction vessel and react at 140℃-150℃ for 16h-20h to obtain a suspension. Step 1.2: Centrifuge the suspension obtained in Step 1.1, then add excess methanol and let it stand for 12-15 hours, then dry it overnight in an oven to obtain Mn-TiO2 powder; in Step 1.2, the centrifugation speed of the suspension is 8500 rpm to 10000 rpm, and the centrifugation time is 15 min to 30 min. Step 2: Prepare a Pt / Mn-TiO2 catalyst based on the product obtained in Step 1. The specific process of Step 2 is as follows: Disperse 1g-1.5g of the Mn-TiO2 powder prepared in Step 1 in 10mL-11.5mL of deionized water, add 0.09g-0.15g of platinum nitrate, and rotate in a closed shaker at 150rpm / min-200rpm / min for 12-15 hours at 30℃-50℃. Then, dry in an oven at 60℃-65℃ for 10-12 hours. After cooling to room temperature, reduce the catalyst by introducing H2 in a tube furnace at 300℃-350℃ for 3-5 hours to finally obtain the Pt / Mn-TiO2 catalyst. The process of producing hydrogen from methylcyclohexane using Pt / Mn-TiO2 catalyst is as follows: 0.15 g to 0.2 g of Pt / Mn-TiO2 catalyst is mixed with 1.5 g to 2 g of quartz sand and then placed in a catalytic fixed bed. The gasification furnace temperature is 130℃ to 135℃, the reaction furnace temperature is 370℃ to 380℃, the heating zone temperature is 135℃ to 140℃, the gas flow rate is 15 mL / min to 30 mL / min, the pressure is 0.3 MPa to 0.6 MPa, the methylcyclohexane injection rate is 0.03 mL / min to 0.05 mL / min, and the catalytic reaction temperature is 350℃ to 380℃.

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