Method for improving dehydrogenation performance of methylcyclohexane catalyst
By directly heating the Pt@Al2O3 catalyst through Joule heating on a honeycomb silicon carbide support, its electronic state is controlled and hydroxide ions are generated. This solves the problems of low heat transfer efficiency and short catalyst life under traditional heating methods, and realizes a highly efficient methylcyclohexane dehydrogenation reaction.
Patent Information
- Application Number
- CN202610026241.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-05-01
AI Technical Summary
Traditional catalytic dehydrogenation of methylcyclohexane suffers from problems such as low heat transfer efficiency, high energy consumption, uneven temperature distribution, and difficulty in controlling the electronic state of the catalyst, leading to increased side reactions and shortened catalyst lifetime, which affects product yield.
A honeycomb silicon carbide support is used to generate Joule heat through electric current to directly heat the Pt@Al2O3 catalyst. The electronic state of the catalyst is controlled by the current and the generation of hydroxide ions is promoted, forming highly dispersed active sites and improving catalytic performance.
It improves the activity and selectivity of the catalyst, extends its service life, reduces production costs, and enhances heat transfer efficiency and catalyst stability.
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Abstract
Description
A method for improving the dehydrogenation performance of methylcyclohexane catalysts Technical Field
[0001] This invention relates to the field of organic liquid hydrogen storage technology, and in particular to a method for improving the dehydrogenation performance of methylcyclohexane catalysts by changing the energy supply method. Background Technology
[0002] Methylcyclohexane (MCH) is an ideal liquid organic hydrogen carrier, and its catalytic dehydrogenation reaction is a key step in realizing hydrogen energy storage, transportation, and release. Currently, this reaction process is mostly heated using a traditional muffle furnace, which involves heating air and then indirectly transferring the heat to the catalyst bed through the reaction tube wall. This indirect heating method suffers from problems such as low heat transfer efficiency, high energy consumption, and uneven temperature distribution inside the reactor, easily leading to local overheating and triggering side reactions such as cracking and carbon deposition, thereby reducing the yield of the target product and the catalyst's lifespan. In addition, the traditional heating mode only provides a thermal effect and cannot effectively control the intrinsic electronic state of the catalyst, limiting further optimization of its catalytic performance. Therefore, developing a novel, efficient, and controllable heating method that can improve heat transfer efficiency while positively influencing the microstate of the catalyst is of great significance for promoting the practical application of methylcyclohexane dehydrogenation technology. Summary of the Invention
[0003] This invention aims to provide a method for improving the catalytic dehydrogenation performance of methylcyclohexane by changing the energy supply method, with toluene as the dehydrogenation product and a selectivity exceeding 99%. This invention not only aims to suppress side reactions by increasing the heat transfer rate, but also hopes to fundamentally enhance its catalytic activity by inducing a change in the physicochemical state of the catalyst through a novel heating mode.
[0004] This invention is achieved through the following technical solution:
[0005] A method for improving the dehydrogenation performance of a methylcyclohexane catalyst by changing the energy supply method, wherein the dehydrogenation products are toluene and hydrogen, includes the following steps:
[0006] A honeycomb silicon carbide carrier is provided, the carrier having resistance, the honeycomb silicon carbide being a cylindrical porous silicon carbide with a diameter of 16 mm and a height of 10 mm, hereinafter referred to as honeycomb silicon carbide;
[0007] The Pt@Al2O3 catalyst was placed in the honeycomb pores of the honeycomb silicon carbide support;
[0008] An electric current is passed through the honeycomb silicon carbide support, and the Joule heat generated by the current passing through the resistor directly and rapidly heats the honeycomb silicon carbide, thereby providing the heat required for the methylcyclohexane dehydrogenation reaction of the Pt@Al2O3 catalyst placed in its pores.
[0009] During the methylcyclohexane dehydrogenation reaction, an electric current is passed through the honeycomb silicon carbide support, so that it is in an electron-rich state while generating Joule heat.
[0010] During the dehydrogenation reaction of methylcyclohexane, the electrons of the honeycomb silicon carbide in the electron-rich state regulate the electronic structure of the platinum (Pt) active center in the Pt@Al2O3 catalyst, preferably through an inward electron interaction force. This electronic effect changes the electron cloud density of Pt, thereby enhancing its catalytic activity for the dehydrogenation reaction.
[0011] Furthermore, during the reduction pretreatment of the Pt@Al2O3 catalyst, applying the current through the honeycomb silicon carbide promotes hydrogen dissociation and induces the generation of a large number of hydroxyl radicals on the catalyst surface. These in-situ generated hydroxyl radicals can serve as channels for platinum species migration and anchoring, significantly promoting platinum dispersion and forming more and more stable highly dispersed active sites, thereby exhibiting superior performance in subsequent reactions. Attached Figure Description
[0012] The invention will be further described below with reference to the accompanying drawings.
[0013] Figure 1a is a STEM particle size analysis diagram of the catalyst in Example 1 of the present invention;
[0014] Figure 1b is a STEM particle size analysis diagram of the catalyst in Comparative Example 1 of this invention;
[0015] Figure 2 shows the TPSR diagrams during the reaction process of Example 2 and Comparative Example 2. Detailed Implementation
[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. However, the scope of the present invention is not limited to the following embodiments. Those skilled in the art will understand that various changes and modifications can be made to the present invention without departing from the spirit and scope thereof.
[0017] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.
[0018] A method for dehydrogenating methylcyclohexane using a catalyst includes:
[0019] S1. Place the Pt@Al2O3 catalyst inside the pores of the honeycomb silicon carbide support;
[0020] S2. Under the condition of passing an electric current through the honeycomb silicon carbide support, methylcyclohexane undergoes a catalytic dehydrogenation reaction.
[0021] In some embodiments, before the dehydrogenation reaction in step S2, an in-situ catalyst reduction step is also included: while the support is heated by passing an electric current, a reducing atmosphere containing hydrogen is introduced into the system for pretreatment.
[0022] The in-situ reduction step is carried out at 280°C to 320°C for 2 to 4 hours.
[0023] The preferred conditions for in-situ reduction are: a temperature of 300°C and treatment in a hydrogen atmosphere for 3 hours.
[0024] In some embodiments, the temperature of the honeycomb silicon carbide support is maintained at 280°C to 320°C during the dehydrogenation reaction.
[0025] Alternatively, the specific conditions for the dehydrogenation reaction are as follows: methylcyclohexane is vaporized at 180°C and then introduced into a catalyst bed at a temperature of 300°C.
[0026] In step S2, the range of the current applied is 0.9A to 1.5A.
[0027] A catalyst for the dehydrogenation of methylcyclohexane includes Pt, Al, and O elements, wherein the mass content of metallic Pt is 0.2% to 0.4%, and the remaining components are γAl2O3, which serves as a support for Pt.
[0028] Preferably, the mass content of metallic Pt is between 0.28% and 0.32%.
[0029] On the other hand, there are two different energy supply methods, including:
[0030] Traditional heating methods involve heating air in a muffle furnace, with heat indirectly conducted through the reaction tube walls. Joule heating, on the other hand, involves directly passing an electric current through the honeycomb silicon carbide to rapidly generate heat.
[0031] Specifically, the preparation methods of Pt@Al2O3 catalysts include:
[0032] (1) Calcine boehmite at 500℃ to prepare γ-Al2O3 support;
[0033] (2) The support obtained in step (1) is treated in a hydrogen-containing atmosphere at 300°C to 400°C;
[0034] (3) Using the equal volume impregnation method, the platinum precursor solution was loaded onto the treated support, and then dried and pressed into tablets to obtain the Pt@Al2O3 catalyst.
[0035] An alternative approach, a method to improve the dehydrogenation performance of a methylcyclohexane catalyst by changing the energy supply method, includes methylcyclohexane reacting under the action of the catalyst to produce hydrogen; the reaction temperature is controlled between 298 °C and 302 °C.
[0036] The catalyst prepared in this invention is first reduced before catalyzing the dehydrogenation of methylcyclohexane. Specifically, it is reduced at 300°C for more than 3 hours in an atmosphere containing a reducing agent (e.g., hydrogen).
[0037] The reaction pressure is atmospheric pressure.
[0038] The activation time is 0.5 h, and the reaction and data acquisition time is usually set to 5 hours.
[0039] The methylcyclohexane dehydrogenation system of the present invention has high selectivity for the product (hydrogen), long catalyst life cycle, and is not easily deactivated, which can effectively reduce industrial production costs, improve overall efficiency, and is easy to promote.
[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.
[0041] Example 1: In-situ reduction of catalyst at 300°C using Joule heating
[0042] The catalyst preparation method is as follows:
[0043] (1) Preparation of carrier: The pseudoboehmite was placed in a muffle furnace and calcined at 500℃ for 12h, and then naturally cooled to room temperature. After being taken out of the muffle furnace, it was placed in a tube furnace and kept at 350℃ for 2h in a reducing atmosphere with a heating rate of 5℃ per minute. It was then taken out for use.
[0044] (2) Pt loading: Prepare the corresponding platinum nitrate ethanol mixture according to the mass fraction (0.32%), and load it onto the prepared support by impregnation method. After loading, place it in an oven to dry overnight. After the above process is completed, perform tableting to obtain the catalyst.
[0045] The Joule heating in-situ reduction method is as follows:
[0046] Honeycomb silicon carbide was placed in the reaction tube of a fixed-bed reactor, and the catalyst was loaded into the honeycomb silicon carbide. Electricity was applied to generate heat, and a reducing atmosphere was introduced at 300°C for 3 hours to obtain the reduced catalyst. The effects of different heating methods on the reduction efficiency were compared. After Joule thermal reduction, to maintain a single variable, a conventional thermal reaction was performed with a methylcyclohexane space velocity of 32. The average conversion rate of methylcyclohexane within five hours was 68.7%, with toluene and hydrogen as products.
[0047] Example 2: Joule heating at 300°C - catalyst for reaction
[0048] The Joule heating method is as follows:
[0049] Honeycomb silicon carbide was placed in the reaction tube of a fixed-bed reactor, and the catalyst was loaded into the honeycomb silicon carbide. Electricity was applied to generate heat, and methylcyclohexane was introduced when the catalyst temperature reached 300℃, with a methylcyclohexane space velocity of 32. The effects of different heating methods on the reaction were compared. To maintain a single variable, the catalyst reduction pretreatment process employed a Joule thermal reduction method.
[0050] The catalyst preparation and reduction process, as well as the parameters, were the same as in Example 1. The average conversion rate of methylcyclohexane within five hours was 75.1%, with toluene and hydrogen as the products.
[0051] Comparative Example 1: Conventional thermal in-situ reduction catalyst at 300℃
[0052] The traditional thermal in-situ reduction method is as follows:
[0053] Honeycomb silicon carbide was placed in the reaction tube of a fixed-bed reactor, and the catalyst was loaded into the honeycomb silicon carbide. The catalyst was indirectly heated by heat generation through a muffle furnace, and a reducing atmosphere was introduced at 300°C for 3 hours to compare the effects of different heating methods on the reduction effect. After conventional thermal reduction, in order to maintain a single variable, the conventional thermal reaction was carried out with a methylcyclohexane space velocity of 32.
[0054] The catalyst preparation and reduction process, as well as the parameters, were the same as in Example 1. The average conversion rate of methylcyclohexane within five hours was 63.2%, with toluene and hydrogen as the products.
[0055] Comparative Example 2: Conventional thermal 300℃ reaction catalyst
[0056] The traditional thermal reaction method is:
[0057] Honeycomb silicon carbide was placed in the reaction tube of a fixed-bed reactor, and the catalyst was loaded into the honeycomb silicon carbide. The catalyst was indirectly heated by heat generation through a muffle furnace. Methylcyclohexane was introduced when the catalyst temperature reached 300℃, and the methylcyclohexane space velocity was 32. The effects of different heating methods on the reaction were compared. To maintain a single variable, the catalyst reduction pretreatment process employed a Joule thermal reduction method.
[0058] The catalyst preparation and reduction process, as well as the parameters, were the same as in Example 1. The average conversion rate of methylcyclohexane within five hours was 70.5%, with toluene and hydrogen as the products.
[0059] Combining Example 1 and Comparative Example 1, it can be seen that the appearance of the catalyst after in-situ reduction changes significantly after changing the energy supply method. Referring to Figure 1, the STEM morphology of the catalysts with two different energy supply pathways shows that, according to particle size analysis, the average particle sizes of platinum particles in the catalysts obtained by Joule thermal reduction and conventional thermal reduction are 1.3 nm and 1.63 nm, respectively. The significantly smaller average particle size (1.3 nm vs. 1.63 nm) directly proves that Joule thermal in-situ reduction can effectively improve the dispersion of platinum in the catalyst. The catalysts in Example 2 and Comparative Example 2 were subjected to mass spectrometry (MS / MS) analysis, and the desorption of toluene was observed in Figure 2. It was found that compared with the conventional thermal reaction process, the Joule thermal reaction can better promote product desorption, thereby improving its performance.
[0060] In summary, this invention successfully replaces the traditional indirect heating method by employing a novel heating mode of direct current-heated honeycomb silicon carbide. This technical solution not only fundamentally improves heat transfer efficiency but also achieves synergistic effects in regulating the electronic state of the catalyst and optimizing its microstructure through the induced electron-rich effect and the unique current-assisted reduction process, providing an effective new approach for the efficient catalytic dehydrogenation reaction of methylcyclohexane.
[0061] The specific embodiments of the present invention have been described above by way of example, but this is not intended to limit the scope of protection. Any equivalent modifications, adaptive changes, or obvious technical substitutions made by conventional means within the scope of the technical principles and core concepts disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A method for dehydrogenation of methylcyclohexane using a catalyst, characterized in that, Includes the following steps: S1. Place the Pt@Al2O3 catalyst within the pores of a honeycomb silicon carbide support; S2. Under the condition of an electric current flowing through the honeycomb silicon carbide support, methylcyclohexane undergoes a catalytic dehydrogenation reaction.
2. The method according to claim 1, characterized in that, Before the dehydrogenation reaction in step S2, an in-situ catalyst reduction step is also included: while the support is heated by passing an electric current, a reducing atmosphere containing hydrogen is introduced into the system for pretreatment.
3. The method according to claim 2, characterized in that, The in-situ reduction step is carried out at 280°C to 320°C for 2 to 4 hours.
4. The method according to claim 3, characterized in that, The specific conditions for in-situ reduction are: a temperature of 300℃ and treatment in a hydrogen atmosphere for 3 hours.
5. The method according to claim 1 or 2, characterized in that, In the dehydrogenation reaction, the temperature of the honeycomb silicon carbide support is maintained between 280°C and 320°C.
6. The method according to claim 5, characterized in that, The specific conditions for the dehydrogenation reaction are as follows: methylcyclohexane is vaporized at 180°C and then introduced into a catalyst bed at a temperature of 300°C.
7. The method according to claim 1 or 2, characterized in that, In step S2, the range of the current applied is 0.9A to 1.5A.
8. The method according to any one of claims 1 to 7, characterized in that, The preparation method of Pt@Al2O3 catalyst includes: (1) calcining boehmite at 500°C to obtain γ-Al2O3 support; (2) treating the support obtained in step (1) at 300°C to 400°C in a hydrogen atmosphere; (3) loading a platinum precursor solution onto the treated support by an equal volume impregnation method, and then drying and pressing it into tablets to obtain Pt@Al2O3 catalyst.
9. The method according to claim 8, characterized in that, The Pt@Al2O3 catalyst contains 0.2% to 0.4% platinum by mass.