Electrically Heated Pt / CeO2 / Foam Monolithic Catalyst and Its Preparation Method and Methylcyclohexane Dehydrogenation Method

Abstract

This invention provides an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, its preparation method, and a method for dehydrogenating methylcyclohexane. The catalyst preparation method includes: mixing a CeO2 dispersion with a Pt precursor solution, followed by static aging, drying, and calcination to obtain a Pt-CeO2 composite; mixing the Pt-CeO2 composite with a solvent to obtain a slurry, coating it onto a metal foam, and then vacuum drying and reduction pretreatment to obtain the electrically internally heated Pt / CeO2 / Foam monolithic catalyst. The electrically internally heated Pt / CeO2 / Foam monolithic catalyst provided by this invention has a highly dispersed active component Pt, and the CeO2 surface has abundant and tunable oxygen defect structures. Pt and CeO2 exhibit strong interactions, and the geometric and electronic structures of Pt are tunable. Furthermore, as a monolithic catalyst, it possesses excellent electrical and thermal conductivity, as well as good mass and heat transfer performance.

Description

Technical Field

[0001] This invention relates to an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, its preparation method, and a method for dehydrogenating methylcyclohexane, belonging to the field of gas-solid phase catalysis technology. Background Technology

[0002] Hydrogen energy is clean, efficient, and has a high mass energy density (120 MJ). kg -1 Hydrogen has advantages such as high energy density, making it an important secondary energy source, energy carrier, and energy storage medium. Hydrogen production through green electricity, achieving electro-hydrogen conversion and storing energy in H2, can effectively balance the supply and demand of renewable energy. However, hydrogen energy has a low volumetric storage density and is prone to leakage and diffusion, posing safety hazards. Therefore, developing safe and efficient hydrogen energy storage and transportation technologies is crucial. Organic liquid hydrogen storage achieves hydrogen storage and release through reversible hydrogenation / dehydrogenation reactions of liquid organic matter. Organic hydrogen storage carriers are liquids at normal temperature and pressure, with physical properties similar to gasoline and diesel, effectively utilizing existing fossil fuel infrastructure. They offer advantages such as high mass hydrogen storage density, convenient and safe storage and transportation, and suitability for long-distance and large-scale transportation. Methylcyclohexane (MCH) is an ideal organic liquid hydrogen storage medium with a high mass hydrogen storage density (~6.1 wt%), excellent hydrogenation / dehydrogenation reversibility, high selectivity for target products, and low toxicity. However, its dehydrogenation process still faces challenges such as inefficient activation of CH bonds, high reaction temperatures, and poor heat and mass transfer in traditional catalytic processes, resulting in low reaction efficiency.

[0003] In recent years, significant progress has been made in both Joule thermal catalysis and methylcyclohexane (MCH) dehydrogenation research, laying a solid foundation for their integration. In the Joule thermal reaction field, several patents highlight its high efficiency, speed, and energy-saving characteristics: CN119793342A proposes using the catalyst directly as the Joule thermal heating element, achieving ammonia decomposition for hydrogen production within 1 second with a conversion rate exceeding 90% and an electrothermal efficiency higher than 90%, breaking through the bottleneck of slow heat transfer and high energy consumption in traditional externally heated reactors; CN119500167A has developed a structured catalyst capable of in-situ growth of LDH nanosheet arrays on NiCrAl alloys, possessing high conductivity, high specific surface area, and excellent thermal stability; and CN119470765A further establishes a quantitative evaluation method for non-thermal effects in electro-enhanced catalysis, providing a basis for regulating the Joule thermal catalysis process. Meanwhile, significant progress has been made in the optimization of Pt-based catalysts in the field of MCH dehydrogenation: CN118949980A enhances the anti-sintering ability of Pt / Al2O3 through Ga / Ce co-doping; CN118162160A utilizes sulfur to regulate the Pt coordination environment to suppress cracking side reactions; CN118026090A and CN117943079A respectively employ carbon fiber and spherical CeO2 supports to enhance Pt dispersion and electronic modulation; CN117899863A constructs a Pt / Mn-TiO2 bifunctional catalyst, balancing hydrogenation and dehydrogenation performance. However, existing MCH dehydrogenation technologies still generally rely on external heating, making it difficult to overcome the problems of heat transfer lag, large temperature gradient, and high energy consumption caused by strongly endothermic reactions (ΔH > +200 kJ / mol). Introducing Joule heating technology into the MCH dehydrogenation system can not only achieve instantaneous temperature rise, uniform temperature control, and high energy efficiency through its "internal heating" mechanism, but also generate heat directly through electrolysis of the catalyst body, significantly shortening the heat transfer path. However, the key to this successful coupling lies in developing functional materials that combine high catalytic activity, high conductivity, and structural stability—that is, catalytic materials that integrate Joule heating and catalytic function.

[0004] Against this backdrop, taking MCH dehydrogenation as a model reaction, and addressing its problems of high dehydrogenation temperature and low reaction efficiency, there is an urgent need to design novel reaction methods to enhance the dehydrogenation process, and to develop highly efficient catalysts that match the novel reaction methods to achieve efficient catalytic dehydrogenation.

[0005] Therefore, developing MCH dehydrogenation catalysts adapted for internal heating is a pressing issue. This will not only be an interdisciplinary innovation between materials design and reaction engineering, but also a core breakthrough for promoting the efficient hydrogen release of liquid organic hydrogen carriers, and will have significant strategic importance for driving the development of hydrogen energy storage and transportation systems towards compactness, intelligence, and low energy consumption. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, its preparation method, and a method for the dehydrogenation of methylcyclohexane. The active site structure of this catalyst can be matched and regulated to the electro- and thermal properties of the electrically internally heated catalysis.

[0007] To achieve the above objectives, the present invention provides a method for preparing an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, comprising the following steps: A dispersion of CeO2 is mixed with a Pt precursor solution, and after static aging, drying, and calcination, a Pt-CeO2 composite is obtained; wherein the mass ratio of the Pt precursor to CeO2 is (0.01-10):(1-10), preferably (0.01-1):(1-5). The Pt-CeO2 composite was mixed with a solvent to obtain a slurry, which was then coated onto metal foam. After vacuum drying and reduction pretreatment, the electrically heated Pt / CeO2 / Foam monolithic catalyst was obtained. The loading amount of the Pt-CeO2 composite on the foamed metal is (0.01-10):(1-100), preferably (0.01-1):(1-10). In this loading amount, the amount of Pt-CeO2 composite is based on its mass, and the amount of foamed metal is based on the mass of the metal in the foamed metal. For example, if foamed iron (Foam Fe, abbreviated as FF) is used, its mass is based on the mass of Fe in the foamed iron.

[0008] This invention, based on the crystal form regulation method of cerium dioxide and the properties of Pt loading, proposes a method for regulating the electronic properties of metallic Pt and the interface structure of CeO2 with different crystal forms. This method is then effectively matched with the electrothermal effects of the catalytic dehydrogenation reaction of methylcyclohexane, achieving a matching regulation method between the active site structure of the catalyst and the electrothermal properties of electrothermal catalysis. This not only provides a new method for improving catalytic reaction efficiency but also has significant implications for the research and manipulation of catalytic reactions and processes.

[0009] In the above preparation method, preferably, the foam metal includes one or more of the following: iron, cobalt, nickel, titanium, copper, aluminum, chromium, and alloys of any of the above metals.

[0010] In the above preparation method, preferably, the Pt precursor includes one or more of chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, sodium chloropalladium, platinum acetylacetonate, platinum chloride, and platinum nitrate.

[0011] In the above preparation method, preferably, the concentration of the Pt precursor solution is 0.01-0.1 mol / L.

[0012] In the above preparation method, preferably, the solvent used in preparing the slurry is anhydrous ethanol or the like.

[0013] In the above preparation method, preferably, during the preparation of the Pt-CeO2 composite, the calcination temperature is 300-600℃ and the time is 2-24 h.

[0014] In the above preparation method, preferably, the vacuum drying temperature is 40-80℃ during the preparation of the Pt-CeO2 composite.

[0015] In the above preparation method, preferably, during the preparation of the Pt-CeO2 composite, the reducing atmosphere of the reduction pretreatment is hydrogen, or a mixture of hydrogen and one of nitrogen, argon, or helium, and the temperature of the reduction pretreatment is 300-800℃, and the time is 1-48 h. When a mixture of hydrogen and one of nitrogen, argon, or helium is used, the volume content of hydrogen can be controlled to be 0.1 vol.%-99.9 vol.%, for example, 10 vol.%.

[0016] In the above preparation method, preferably, the CeO2 is prepared by the following steps: mixing a cerium source solution and an alkaline solution in a molar ratio of 1:(0.001-10), followed by crystallization, centrifugation, drying, and calcination to obtain CeO2 solid powder.

[0017] In the above preparation method, preferably, in the process of preparing CeO2 solid powder, the cerium source is selected from one or more combinations of cerium nitrate, cerium chloride, cerium sulfate, and cerium acetylacetone.

[0018] In the above preparation method, preferably, in the process of preparing CeO2 solid powder, the alkaline solution is selected from NaOH solution and Na3PO4 solution. More preferably, the concentration of NaOH solution is 1-20 mol / L and the concentration of Na3PO4 solution is 0.001-0.1 mol / L.

[0019] In the above preparation method, preferably, during the preparation of CeO2 solid powder, the calcination temperature is 300-600℃ and the time is 2-24 h.

[0020] In the above preparation method, preferably, the CeO2 is nanorod-shaped CeO2 (r-CeO2), nanocubic CeO2 (c-CeO2), or nanooctahedral CeO2 (o-CeO2), wherein: The r-CeO2 is prepared by the following steps: mixing cerium source solution and NaOH solution, crystallizing at 70-120℃ for 12-72 h, centrifuging, drying, and calcining at 300-600℃ for 2-24 h to obtain r-CeO2 solid powder; The c-CeO2 is prepared by the following steps: mixing cerium source solution and NaOH solution, crystallizing at 100-220℃ for 12-72 h, centrifuging, drying, and calcining at 300-600℃ for 2-24 h to obtain c-CeO2 solid powder; The o-CeO2 is prepared by the following steps: mixing cerium source solution and Na3PO4 solution, crystallizing at 100-220℃ for 6-72 h, centrifuging, drying, and calcining at 300-600℃ for 2-24 h to obtain o-CeO2 solid powder.

[0021] The present invention also provides an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, which is prepared by the above-described preparation method.

[0022] The present invention also provides a method for dehydrogenating methylcyclohexane, which uses the above-mentioned electrically heated Pt / CeO2 / Foam monolithic catalyst as a dehydrogenation catalyst and reacts it directly with a reaction gas containing methylcyclohexane to obtain hydrogen and toluene. The electrically heated Pt / CeO2 / Foam monolithic catalyst is energized.

[0023] In the above-described methylcyclohexane dehydrogenation method, preferably, part or all of the temperature required for the reaction is provided by an electrically heated Pt / CeO2 / Foam monolithic catalyst.

[0024] In the above-mentioned methylcyclohexane dehydrogenation method, preferably, the catalyst is energized in the following manner: the electrically heated Pt / CeO2 / Foam monolithic catalyst is connected to both ends of a power source by means of wires or the like, and a voltage is applied to the catalyst by the power source to form a circuit, thereby realizing the energization.

[0025] In the above-mentioned methylcyclohexane dehydrogenation method, preferably, the voltage applied is 0.1-10kV and the current is 0.001-1000A.

[0026] In the above-described methylcyclohexane dehydrogenation method, preferably, the volume concentration of methylcyclohexane in the reaction gas is 0.01%-100%, more preferably 20%-100%. When fed with a methylcyclohexane concentration of 100% in the reaction gas, the catalyst of the present invention also exhibits stability.

[0027] In the above-described method for dehydrogenating methylcyclohexane, preferably, the feed volumetric flow rate of methylcyclohexane is 1.2-6 mL / h.

[0028] In the above-described method for dehydrogenating methylcyclohexane, preferably, when the concentration of methylcyclohexane in the reaction gas is not 100%, the reaction gas also contains a carrier gas; more preferably, the carrier gas is selected from one or more combinations of nitrogen, argon, helium, and hydrogen; even more preferably, the volumetric flow rate of the carrier gas is 5-20 mL / min.

[0029] In the above-described methylcyclohexane dehydrogenation method, preferably, the volume hourly space velocity (VHSV) of the mixture of the carrier gas (such as nitrogen) and methylcyclohexane in the methylcyclohexane dehydrogenation reaction is 2000-10000 h⁻¹. -1 .

[0030] In the above-described method for dehydrogenating methylcyclohexane, preferably, the temperature of the methylcyclohexane dehydrogenation reaction is 200-400°C, more preferably 250-400°C. In some specific embodiments of the present invention, the temperature of the methylcyclohexane dehydrogenation reaction is 300°C.

[0031] In the above-described methylcyclohexane dehydrogenation method, preferably, the reaction pressure is atmospheric pressure.

[0032] The electrically internally heated Pt / CeO2 / Foam monolithic catalyst provided by this invention has a highly dispersed active component, Pt, and Pt exhibits strong interactions with CeO2. The CeO2 surface possesses abundant and tunable defect structures, while the geometric structure (Pt particle size) and electronic structure (Pt...) of Pt... + The charge density is also adjustable. Furthermore, the catalyst is monolithic, exhibiting excellent electrical and thermal conductivity, as well as superior mass and heat transfer properties. With the significant improvement in renewable energy power generation efficiency and the decrease in green electricity costs, the direct use of green electricity to drive chemical reactions is gaining increasing attention. The electro-internal heating catalytic technology combined with the monolithic catalyst provided by this invention can solve the mass and heat transfer problems in the dehydrogenation process, while simultaneously enhancing the reaction process, thereby significantly improving reaction performance.

[0033] In the dehydrogenation process of methylcyclohexane, the Joule heat generated on the Pt / CeO2 / Foam monolithic catalyst by energizing the catalyst is not only fast and the heat transfer is matched with the heat of reaction, which can enhance heat transfer, but also forms an electric field that affects the electronic structure of the active sites and can interact with the active site structure of the catalyst to improve the reaction performance. Attached Figure Description

[0034] Figure 1 (a) XRD spectra and (b) transmission infrared spectra of Pt / r-CeO2 / FF, Pt / c-CeO2 / FF and Pt / o-CeO2 / FF prepared in Examples 1-3.

[0035] Figure 2 HRTEM images of Pt / r-CeO2 / FF, Pt / c-CeO2 / FF and Pt / o-CeO2 / FF prepared in Examples 1-3.

[0036] Figure 3 The Ov and Ce of Pt / r-CeO2 / FF, Pt / c-CeO2 / FF and Pt / o-CeO2 / FF prepared in Examples 1-3 3+ The EPR spectrum.

[0037] Figure 4 The graph shows the temperature difference test results of different catalysts before and after MCH feed under the conventional thermal catalysis (CH) mode, with reaction temperatures of 250℃ and 300℃, as well as the relationship between the temperature difference and the conversion rate of methylcyclohexane (MCH) under the conventional thermal catalysis (CH) mode and the electric internal heating (IEH) mode. Detailed Implementation

[0038] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0039] Example 1

[0040] This embodiment provides an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, which is prepared through the following steps: (1) Dissolve 1.7g of cerium nitrate in 10mL of water; (2) Add 70 mL of 10 mol / L NaOH solution to the solution obtained in step (1) and stir for 60 min; (3) The solution obtained in step (2) was transferred to the reaction vessel, crystallized at 100°C for 24 h, cooled, centrifuged and washed until neutral, and dried at 80°C to obtain solid powder; (4) The solid powder obtained in step (3) was calcined in air at 500°C for 4 h and then cooled to obtain r-CeO2; (5) Wet 0.2 g of the r-CeO2 powder obtained in step (4) with water, and add 81 μL of a 20 mg concentration. mL -1 H2PtCl6 The mixture of 6H2O aqueous solution was homogeneous, allowed to stand for aging, and dried at 60℃ to obtain a solid powder. (6) The solid powder obtained in step (5) was calcined in air at 400°C for 4 h to obtain Pt / r-CeO2 powder; (7) The powder obtained in step (6) is dispersed in ethanol to obtain a slurry; (8) The slurry obtained in step (7) is coated onto foamed iron (foam pore size 20 ppi) at a coating amount of 10 mg / 100 mg (based on the mass of Pt / r-CeO2 powder and Fe in foamed iron), and dried under vacuum at 60 °C in a 50 mL H2 / N2 mixed gas with a hydrogen volume concentration of 10 vol%. min -1 In the process, Pt / r-CeO2 / FF was obtained by reduction pretreatment at 350℃ for 60 min.

[0041] The process of catalyzing the dehydrogenation of methylcyclohexane using the above-mentioned Pt / r-CeO2 / FF catalyst includes: The Pt / r-CeO2 / FF catalyst was placed in a quartz reaction tube and a hydrogen-nitrogen mixture with a total volume flow rate of 60 mL / min and a hydrogen volume concentration of 10% was introduced and pretreated at 400℃ for 1 h. Electric heating method: After pretreatment, the Pt / r-CeO2 / FF catalyst is placed in the reaction tube. Terminals are connected to the catalyst ends to form a circuit, and a voltage is applied to it to form a closed loop. Simultaneously, an infrared temperature measurement system is used to measure the temperature of the Pt / r-CeO2 / FF catalyst, and a temperature control system is used to control the reaction temperature. Specifically, the reaction temperature is set to 300℃, the loop is closed, and the voltage automatically increases to approximately 1V and the power increases to approximately 10W, so that the actual temperature value increases by approximately 10%. The temperature reaches the set value of 300℃ / min, and nitrogen gas is purged at 15mL / min for 30min. Then, nitrogen gas is introduced and the methylcyclohexane feed pump is turned on with a feed flow rate of 0.02mL / min and a methylcyclohexane feed volume concentration of 19%. Methylcyclohexane and nitrogen gas are premixed in the preheating furnace at a temperature of 120℃. After 2 hours of reaction, the performance data of the catalyst were measured as follows: the conversion rate of methylcyclohexane was 41%, the selectivity for toluene was 99%, and the hydrogen release rate was ~6643 mmol / g. Pt / min.

[0042] The above-described electrically heated reaction process was repeated at 250℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be ~940 mmol / g. Pt / min.

[0043] Traditional heating method: The dehydrogenation reaction of methylcyclohexane is carried out in a fixed-bed reaction tube. The Pt / r-CeO2 / FF catalyst is placed in the reaction tube, and the reaction furnace temperature is set to 300℃. The reaction is driven by heating the reaction tube in the reaction furnace. At the same time, nitrogen gas is purged at 15 mL / min for 30 min. Then, nitrogen gas is introduced and the methylcyclohexane feed pump is turned on. The feed flow rate is 0.02 mL / min and the volume concentration of methylcyclohexane feed is 19%. Methylcyclohexane and nitrogen are premixed in a preheating furnace at 120℃. After 2 hours of reaction, the performance data of the catalyst using the conventional heating method were as follows: methylcyclohexane conversion rate of 16%, toluene selectivity of 99%, and hydrogen release rate of ~2549 mmol / g. Pt / min.

[0044] The conventional heating reaction process was repeated at 250℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be ~374 mmol / g. Pt / min.

[0045] Example 2

[0046] This embodiment provides an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, which is prepared through the following steps: (1) is exactly the same as step (1) in Example 1; (2) is exactly the same as step (1) in Example 1; (3) The solution obtained in step (2) was transferred to a reaction vessel, crystallized at 180°C for 24 h, cooled, centrifuged and washed until neutral, and dried at 80°C to obtain solid powder; (4) The solid powder obtained in step (3) was calcined in air at 500°C for 4 h and then cooled to obtain c-CeO2; (5) Wet 0.2g of the c-CeO2 powder obtained in step (4) with water, and add 81 μL of a 20 mg concentration. mL -1 H2PtCl6 The mixture of 6H2O aqueous solution was homogeneous, allowed to stand for aging, and dried at 60℃ to obtain a solid powder. (6) The solid powder obtained in step (5) was calcined in air at 400°C for 4 h to obtain Pt / c-CeO2; (7) is exactly the same as step (1) in Example 1; (8) The slurry obtained in step (7) is coated onto (foam pore size 20 ppi) at a coating amount of 10 mg / 100 mg (based on the mass of Pt / c-CeO2 powder and Fe in foam iron), and dried under vacuum at 60 °C in a 50 mL H2 / N2 mixed gas with a hydrogen volume concentration of 10 vol%. min -1 In the process, Pt / c-CeO2 / FF was obtained by reduction pretreatment at 350℃ for 60 min.

[0047] The process of catalyzing the dehydrogenation of methylcyclohexane using the above-mentioned Pt / c-CeO2 / FF catalyst includes: The Pt / c-CeO2 / FF catalyst was placed in a quartz reaction tube and a hydrogen-nitrogen mixture with a total volume flow rate of 60 mL / min and a hydrogen volume concentration of 10% was introduced. The mixture was pretreated at 400℃ for 1 h. The thermal dehydrogenation reaction of methylcyclohexane was carried out using the same method as in Example 1, employing electric heating. After 2 hours of reaction, the catalyst performance data were measured as follows: methylcyclohexane conversion rate of 26%, toluene selectivity of 99%, and hydrogen release rate of ~4301 mmol / g. Pt / min.

[0048] In 250 The above electrically heated reaction process was repeated at ℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be ~502 mmol / g. Pt / min.

[0049] The dehydrogenation reaction of methylcyclohexane was carried out using the same conventional heating method as in Example 1. After 2 hours of reaction, the catalyst performance data were measured as follows: methylcyclohexane conversion rate of 14%, toluene selectivity of 99%, and hydrogen release rate of ~2198 mmol / g. Pt / min.

[0050] In 250 The conventional heating reaction process was repeated at ℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be ~279 mmol / g. Pt / min.

[0051] Example 3

[0052] This embodiment provides an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, which is prepared through the following steps: (1) Dissolve 0.9 g of cerium nitrate in 70 mL of water; (2) Add 10 mL of 0.005 mol / L Na3PO4 solution to the solution obtained in step (1) and stir for 60 min; (3) The solution obtained in step (2) was transferred to a reaction vessel, crystallized at 170°C for 10 h, cooled, centrifuged and washed until neutral, and dried at 80°C to obtain a solid powder; (4) The solid powder obtained in step (3) was calcined in air at 500°C for 4 h and then cooled to obtain o-CeO2; (5) Wet 0.2 g of the o-CeO2 powder obtained in step (4) with water, and add 81 μL of 20 mg concentration. mL -1 H2PtCl6 The mixture of 6H2O aqueous solution was homogeneous, allowed to stand for aging, and dried at 60℃ to obtain a solid powder. (6) The solid powder obtained in step (5) was calcined in air at 400°C for 4 h to obtain Pt / o-CeO2; (7) is exactly the same as step (1) in Example 1; (8) The slurry obtained in step (7) is coated onto (foam pore size 20 ppi) at a coating amount of 10 mg / 100 mg (based on the mass of Pt / o-CeO2 powder and Fe in foam iron), and dried under vacuum at 60 °C in a 50 mL H2 / N2 mixed gas with a hydrogen volume concentration of 10 vol%. min -1 In the process, Pt / o-CeO2 / FF was obtained by reduction pretreatment at 350℃ for 60 min.

[0053] The process of catalyzing the dehydrogenation of methylcyclohexane using the above-mentioned Pt / o-CeO2 / FF catalyst includes: The Pt / o-CeO2 / FF catalyst was placed in a quartz reaction tube and a hydrogen-nitrogen mixture with a total volume flow rate of 60 mL / min and a hydrogen volume concentration of 10% was introduced. The mixture was then pretreated at 400℃ for 1 h. The dehydrogenation reaction of methylcyclohexane was carried out using the same method as in Example 1, via electrothermal heating. After 2 hours of reaction, the performance data of the catalyst were measured as follows: methylcyclohexane conversion rate of 1.5%, toluene selectivity of 99%, and hydrogen release rate of ~246 mmol / g. Pt / min.

[0054] In 250 The above electrically heated reaction process was repeated at ℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be 19 mmol / g. Pt / min.

[0055] The dehydrogenation reaction of methylcyclohexane was carried out using the same conventional heating method as in Example 1. After 2 hours of reaction, the catalyst performance data were as follows: methylcyclohexane conversion rate of 1%, toluene selectivity of 99%, and hydrogen release rate of ~143 mmol / g. Pt / min.

[0056] In 250 The conventional heating process was repeated at ℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be 9 mmol / g. Pt / min.

[0057] Comparative Example 1

[0058] This comparative example provides an electrically heated Pt catalyst, which is prepared through the following steps: (1) Disperse 0.2 g SiO2 into 500 mL of deionized water, and slowly add 81 μL of 20 mg SiO2 solution while stirring. mL -1 H2PtCl6 The solid powder was obtained by stirring the 6H2O aqueous solution for 24 h, centrifuging and washing with deionized water, and drying at 60℃ for 12 h. (2) The solid powder obtained in step (1) was calcined at 400°C for 4 h in air atmosphere to obtain Pt / SiO2; (3) Disperse Pt / SiO2 powder (~10 mg) in ethanol to form a homogeneous mixture; uniformly load the above mixture onto foamed iron (foam pore size 20 ppi) with a coating amount of 10 mg / 100 mg (based on the mass of Pt / SiO2 powder and Fe in foamed iron), vacuum dry at 60 °C for 2 h, and then dry in a 50 mL H2 / N2 mixed gas with a hydrogen volume concentration of 10 vol%. min -1 In the process, Pt / SiO2 / FF was pretreated at 400℃ for 60 min to finally obtain Pt / SiO2 / FF.

[0059] The process of catalyzing the dehydrogenation reaction of methylcyclohexane using the above-mentioned Pt / SiO2 / FF catalyst includes: The Pt / SiO2 / FF catalyst was placed in a quartz reaction tube and a hydrogen-nitrogen mixture with a total volume flow rate of 60 mL / min and a hydrogen volume concentration of 10% was introduced. The mixture was pretreated at 400 °C for 1 h.

[0060] The dehydrogenation reaction of methylcyclohexane was carried out using the same method as in Example 1, via electrothermal heating. After 2 hours of reaction, the performance data of the catalyst were measured as follows: methylcyclohexane conversion rate of 2.5%, toluene selectivity of 99%, and hydrogen release rate of ~360 mmol / g.Pt / min.

[0061] The above reaction process was repeated at 250℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be 0 mmol / g. Pt / min.

[0062] The dehydrogenation reaction of methylcyclohexane was carried out using the same conventional heating method as in Example 1. After 2 hours of reaction, the catalyst performance data were measured as follows: methylcyclohexane conversion rate of 2%, toluene selectivity of 99%, and hydrogen release rate of ~288 mmol / g. Pt / min.

[0063] The conventional heating process was repeated at 250℃ (i.e., the reaction temperature was set to 250℃). After 2 hours of reaction, the hydrogen release rate was measured to be 0 mmol / g. Pt / min.

[0064] The performance data of the catalysts in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0065] Table 1.

[0066] As can be seen from the experimental data in Table 1, by using the electrically heated Pt / CeO2 / Foam monolithic catalyst provided in this invention for the dehydrogenation reaction of methylcyclohexane in an electrically heated mode, an extremely high hydrogen release rate can be obtained, which can be increased by more than 50% compared with the traditional heating mode. Among them, the hydrogen release rate of Pt / r-CeO2 / FF can reach 6000 mmol / g. Pt Its efficiency is above 1000 m / min, significantly higher than other catalysts. Moreover, its conversion rate of methylcyclohexane reaches 41%, which is also significantly higher than other catalysts.

[0067] Furthermore, the electrically heated Pt / CeO2 / Foam monolithic catalyst provided by this invention achieves a high hydrogen release rate at 250°C. The preferred Pt / CeO2 / Foam catalyst in Example 1 achieves a hydrogen release rate of 940 mmol / g at electrically heated 250°C. Pt / min, which is 2.51 times that of the same catalyst under conventional heating mode.

[0068] The crystal phase structures of the three Pt / CeO2 / Foam monolithic catalysts prepared in Examples 1-3 were characterized by XRD in this invention, and the monolithic catalysts were analyzed and characterized by FTIR. The (a) XRD spectra and (b) transmission infrared spectra of Pt / r-CeO2 / FF, Pt / c-CeO2 / FF, and Pt / o-CeO2 / FF are shown below. Figure 1As shown.

[0069] according to Figure 1 As shown in (a), the diffraction peaks of the three samples are similar, consistent with the CeO2 structure of fluorite (JCPDS No. 43-1002). Among them, 2θ has a series of characteristic peaks at ~28.5°, ~30.1°, ~47.5° and ~56.3°, which belong to the (111), (200), (220) and (311) crystal planes of CeO2, respectively. The high intensity and small half-width of the diffraction peaks indicate that the catalyst has good crystallinity. In addition to the characteristic peaks belonging to CeO2, all samples show three strong diffraction peaks at ~44.90°, ~65.40° and ~82.80° of 2θ, which belong to the (011), (020) and (121) crystal planes of Fe, respectively (JCPDS No. 06-0696). This is generated by the structural framework FF of the catalyst. Furthermore, no Pt diffraction peaks were observed in any of the samples, possibly due to low Pt content or crystallinity. Apart from the aforementioned characteristic peaks, no other information was observed. This indicates that no new crystal phase structure was formed during the preparation of the monolithic catalyst.

[0070] Depend on Figure 1 As shown in (b), all catalysts are at 3000 cm⁻¹ -1 up to 3500 cm -1 The absorption peaks within the range are attributed to the OH vibrations on the sample surface. At ~1627 cm⁻¹ -1 The absorption peak at ~1375 cm⁻¹ is attributed to the OH vibration of H₂O adsorbed on the catalyst surface; -1 The characteristic absorption peak at 500 cm⁻¹ may be related to the carbonate groups formed by the adsorption of CO₂ from the air by defects on the catalyst surface; -1 up to 1100 cm -1 The absorption bands within the range are attributed to the Ce-O groups on CeO2. All catalysts exhibit the characteristic structure of CeO2, consistent with the XRD characterization results.

[0071] The crystal structures of the three Pt / CeO2 / Foam prepared in Examples 1-3 were characterized by HRTEM. Figure 2 Image (a) is an HRTEM image of Pt / r-CeO2 / FF, showing clear lattice fringes, indicating high crystallinity of the catalyst. Two characteristic crystal planes are observed: the (110) plane with a lattice spacing of 0.19 nm and the (200) plane with a lattice spacing of 0.27 nm. Furthermore, the rod-like structure exhibits dark depressions and protrusions on its surface, indicating a rough surface and the presence of numerous high-surface-energy edge atomic structures. Figure 2(b) is an HRTEM image of Pt / c-CeO2 / FF, which only exposes the (200) crystal plane and has a lattice spacing of 0.27 nm. Figure 2 Image (c) shows an HRTEM image of Pt / o-CeO2 / FF, exposing only the (111) crystal plane with a lattice spacing of 0.31 nm. According to the reported CeO2 structural characteristics, r-CeO2 mainly exposes the {100} and {110} crystal planes, while c-CeO2 exposes the {100} crystal plane and o-CeO2 exposes the {111} crystal plane.

[0072] Three monolithic catalysts, Pt / r-CeO2 / FF, Pt / c-CeO2 / FF, and Pt / o-CeO2 / FF, were studied using EPR, and the results are as follows: Figure 3 As shown. Figure 3 As shown in (a), a strong symmetric signal appears at a g-factor of 2.004, which is generated by unpaired electrons at the Ov sites of the catalyst. The signal intensity represents the Ov concentration. It is clear from the figure that the Pt / o-CeO2 / FF catalyst has the weakest signal, indicating it has the lowest Ov content. The Ov signal of the Pt / c-CeO2 / FF catalyst is significantly enhanced, while the Ov signal of the Pt / r-CeO2 / FF catalyst is the highest, indicating its highest defect concentration. Strong signals are also observed at g-factors of 1.967 and 1.940. This is because the H2 reduction process removes lattice oxygen from the catalyst, and the Ce... 4+ Reduced to Ce 3 + This causes unpaired electrons to form (such as) Figure 3 (As shown in (b)). When the g factor = 1.967, it is due to Ce perpendicular to the magnetic field direction. 3+ The generated, denoted as g ⊥ Ce 3+ When the g-factor = 1.940, it is due to Ce parallel to the direction of the magnetic field. 3+ The generated, denoted as g ‖ Ce 3+ Three types of monolithic catalysts on g ⊥ Ce 3+ and g ‖ Ce 3+ The intensity variation pattern is similar to that of Ov, i.e., Pt / r-CeO2 / FF > Pt / c-CeO2 / FF > Pt / o-CeO2 / FF. This indicates that under the same H2 reduction treatment conditions, Pt / r-CeO2 / FF with exposed {110} crystal planes is most prone to defect structures, followed by Pt / c-CeO2 / FF with exposed {100} crystal planes. Pt / o-CeO2 / FF with exposed {111} crystal planes has the lowest surface energy, exhibits the highest structural stability, and is unlikely to generate defect structures.

[0073] To reveal the differences in heat transfer processes under IEH and CH modes, the temperature change of the catalyst was measured using a high-precision infrared thermometer in both modes. The test results are as follows: Figure 4 As shown. Among them, Figure 4 Figure (a) shows the temperature difference of the three catalysts before and after MCH feed in CH mode and at different reaction temperatures. It is clear from the figure that the temperature difference increases continuously with increasing reaction temperature or catalyst performance. Further analysis was conducted on the relationship between dehydrogenation conversion rate and temperature difference under the two heating modes (e.g., Figure 4 As shown in (b) of the figure, the temperature difference is positively correlated with the dehydrogenation conversion rate in the CH mode. However, in the IEH mode, the change in conversion rate does not produce a significant temperature difference, indicating that the heat transfer rate from the heat source to the catalyst in this mode can meet the reaction heat requirements under any conditions.

[0074] In summary, this invention utilizes Pt / CeO2 / Foam-based catalysts with different exposed crystal facets as catalytic components and FF, which possesses excellent electrical and thermal conductivity and a unique three-dimensional structure, as a heating component to construct a series of monolithic Pt / CeO2 / FF-based catalysts with different defect structures. In CH mode, Pt / r-CeO2 / FF with exposed {110} crystal facets exhibits the highest reaction performance, with a hydrogen release rate of ~2549 mmol. g Pt -1 min -1 The IEH mode significantly improves the performance of MCH dehydrogenation, with the Pt / r-CeO2 / FF catalyst achieving a hydrogen release rate of ~6643 mmol under this mode. g Pt -1 min -1 It is 2.6 times that of the CH mode.

[0075] The performance evaluation results of this invention show that, at a reaction temperature of 300°C, the hydrogen evolution rate in the internally electrically heated (IEH) mode is significantly higher than the hydrogen release rate reported in the literature for Pt-based catalysts under conventional heating (CH) mode and the same reaction conditions. Combined high-precision temperature measurements, heat transfer rate equations, and reaction heat analysis results indicate that Pt / CeO2 / FF not only possesses high mass and heat transfer capabilities, but also, in IEH mode, exhibits low thermal resistance and heat capacity as the heating unit, demonstrating rapid temperature response and high heat transfer efficiency.

Claims

1. A method for preparing an electrically internally heated Pt / CeO2 / Foam monolithic catalyst, comprising the following steps: A dispersion of CeO2 is mixed with a Pt precursor solution, and after static aging, drying, and calcination, a Pt-CeO2 composite is obtained; wherein the mass ratio of the Pt precursor to CeO2 is (0.01-10):(1-10), preferably (0.01-1):(1-5). The Pt-CeO2 composite was mixed with a solvent to obtain a slurry, which was then coated onto a foam metal. After vacuum drying and reduction pretreatment, the electrically heated Pt / CeO2 / Foam monolithic catalyst was obtained. The loading of the Pt-CeO2 composite on the foamed metal is (0.01-10):(1-100), preferably (0.01-1):(1-10).

2. The preparation method according to claim 1, wherein, The foam metal includes one or more of the following: iron, cobalt, nickel, titanium, copper, aluminum, chromium, and alloys of any of the above metals.

3. The preparation method according to claim 1, wherein, The Pt precursor includes one or more of the following: chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, sodium chloropalladium, platinum acetylacetonate, platinum chloride, and platinum nitrate. Preferably, the concentration of the Pt precursor solution is 0.01-0.1 mol / L.

4. The preparation method according to claim 1, wherein, In the preparation of the Pt-CeO2 composite, the calcination temperature is 300-600℃ and the time is 2-24 h; The vacuum drying temperature is 40-80℃; The reducing atmosphere of the reduction pretreatment is hydrogen, or a mixture of hydrogen with one of nitrogen, argon, or helium, and the temperature of the reduction pretreatment is 300-800℃, and the time is 1-48 h.

5. The preparation method according to claim 1, wherein, The CeO2 is prepared through the following steps: A cerium source solution and an alkaline solution were mixed in a molar ratio of 1:(0.001-10), and then crystallized, centrifuged, dried, and calcined to obtain CeO2 solid powder. Preferably, the cerium source is selected from one or a combination of two or more of cerium nitrate, cerium chloride, cerium sulfate, and cerium acetylacetone; Preferably, the alkaline solution is selected from NaOH solution and Na3PO4 solution; more preferably, the concentration of the NaOH solution is 1-20 mol / L and the concentration of the Na3PO4 solution is 0.001-0.1 mol / L. Preferably, in the process of preparing CeO2 solid powder, the calcination temperature is 300-600℃ and the time is 2-24 h.

6. The preparation method according to claim 5, wherein, The CeO2 is r-CeO2, c-CeO2, or o-CeO2, wherein: The r-CeO2 is prepared by the following steps: mixing cerium source solution and NaOH solution, crystallizing at 70-120℃ for 12-72h, centrifuging, drying, and calcining at 300-600℃ for 2-24h to obtain r-CeO2 solid powder; The c-CeO2 is prepared by the following steps: mixing cerium source solution and NaOH solution, crystallizing at 100-220℃ for 12-72 h, centrifuging, drying, and calcining at 300-600℃ for 2-24 h to obtain c-CeO2 solid powder; The o-CeO2 is prepared by the following steps: mixing cerium source solution and Na3PO4 solution, crystallizing at 100-220℃ for 6-72 h, centrifuging, drying, and calcining at 300-600℃ for 2-24 h to obtain o-CeO2 solid powder.

7. An electrically heated Pt / CeO2 / Foam monolithic catalyst, which is prepared by the method according to any one of claims 1-6.

8. A method for dehydrogenating methylcyclohexane, wherein the electrically heated Pt / CeO2 / Foam monolithic catalyst as described in claim 7 is used as the dehydrogenation catalyst, and the catalyst is directly reacted with a reaction gas containing methylcyclohexane to obtain hydrogen and toluene; in, The electrically heated Pt / CeO2 / Foam monolithic catalyst is energized.

9. The method for dehydrogenating methylcyclohexane according to claim 8, wherein, The temperature required for the reaction is partially or entirely provided by an electrically heated Pt / CeO2 / Foam monolithic catalyst. Preferably, the voltage applied is 0.1-10 kV and the current is 0.001-1000A.

10. The method for dehydrogenating methylcyclohexane according to claim 8 or 9, wherein, The volume concentration of methylcyclohexane in the reaction gas is 1%-100%, preferably 20%-100%; Preferably, the feed volumetric flow rate of the methylcyclohexane is 1.2-6 mL / h; Preferably, the reaction gas further contains a carrier gas; more preferably, the carrier gas is selected from one or more combinations of nitrogen, argon, helium, and hydrogen; even more preferably, the volumetric flow rate of the carrier gas is 5-20 mL / min. Preferably, the volume hourly space velocity (VHSV) of the methylcyclohexane dehydrogenation reaction is 2000-10000 h⁻¹. -1 ; Preferably, the temperature of the methylcyclohexane dehydrogenation reaction is 200-400°C, more preferably 250-400°C; Preferably, the reaction is carried out at atmospheric pressure.

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