Preparation Of Ceramic-Supported Catalyst And Its Application In A Methanol Steam Reforming Microreactor

The extensive exploitation and consumption of fossil energy sources has produced an increasingly serious greenhouse effect and environmental pollution,making the optimization of energy structure and the utilization of new energy become the focus of sustainable development.As a renewable and abundant clean energy with high calorific value,hydrogen has the potential for large-scale application in new energy transports such as hydrogen energy vehicles.However,the common hydrogen supply method of hydrogen storage tank has the problems of low capacity and poor safety,which restricts the application of hydrogen energy vehicles and makes the on-board online hydrogen production technology receive widespread attention.Methanol steam reforming is a hydrogen production method with the characteristics of low reaction temperature,high H₂selectivity and low CO concentration,which has unique superiorities in hydrogen production efficiency.Meanwhile,the rapidly developing microreactor technology in recent years has shown great application prospects in the field of catalysis due to its advantages of high conversion rate,good safety and high degree of integration.Therefore,the combination of methanol steam reforming and microreactor technology could provide a new scheme for the on-board online hydrogen production,which is expected to supply hydrogen safely and efficiently,and could meet the needs of miniaturization and lightweighting of hydrogen production systems.To address the shortcomings of metal catalyst supports such as high processing cost,low catalyst loading strength and poor chemical stability,this work used Al₂O₃ foam ceramic,SiC porous ceramic and cordierite honeycomb ceramic as catalyst supports,and the glycerol in situ reduction method,one-step hydrothermal method,polyacrylic acid modification method,glycol solution combustion method and metal organic framework derivatization method were applied to prepare and support a series of CuO/ZnO/CeO₂/ZrO₂ catalysts and catalyst washcoats,resulting in the progressive improvement of the catalytic performance of ceramic supports in a microreactor for methanol steam reforming.The main researches and results of this work are as follows:（1）CuO/ZnO/CeO₂/ZrO₂ catalyst was prepared by the glycerol in situ reduction method,and the influence mechanism of glycerol content and deposition number on catalyst was elucidated.Glycerol could reduce the catalyst in situ at 220℃,and the increase of glycerol content could increase the reduction degree and residual carbon of the catalyst,thereby reducing the S_BET value of the catalyst.The uniformity of catalyst washcoat improved with the increase of deposition number,while excessive depositions could lead to pore clogging and agglomerated particles.Excellent catalyst washcoat and high loading strength could be obtained when the weight ratio of glycerol to catalyst was 1:1 and the deposition number was 3.The catalyst-loaded Al₂O₃ foam ceramic support could achieve 93.5%methanol conversion rate at a reaction temperature of 360°C and an inlet methanol flow rate of 0.048 mol/h.（2）CuO/ZnO/CeO₂/ZrO₂ nanoflowers catalyst was prepared by the one-step hydrothermal method,and the influence mechanism of one-step hydrothermal on catalyst was elucidated.The catalyst was composed of multiple porous nanosheets assembled by aggregation,and the gas generated during the preparation process led to the pores on the nanosheets.The S_BET value of the catalyst was 21.12 m²/g,and the catalyst showed good redox property,plenty oxygen vacancies,high loading strength and high catalytic activity.The nanoflowers catalyst was firmly bonded to the ceramic surface,resulting in a high loading strength.The catalyst-loaded Al₂O₃ foam ceramic support could achieve 99.8%methanol conversion rate at a reaction temperature of310°C and an inlet methanol flow rate of 0.048 mol/h.（3）Porous reticular CuO/ZnO/CeO₂/ZrO₂ catalyst was prepared by the polyacrylic acid modification method,and the influence mechanism of polyacrylic acid modification on catalyst was elucidated.The catalyst particles were fine and uniform,which was caused by the heat loss due to the gases generated during the calcination process.The porous reticular catalyst with high S_BETvalue reduced the size of the catalytic channels and increased the number of effective catalytic channels simultaneously,which increased the effective catalytic areas and residence time,resulting in a further improvement of catalytic performance of the Al₂O₃ foam ceramic support.The catalyst-loaded Al₂O₃ foam ceramic support could achieve 100%methanol conversion rate at a reaction temperature of 300°C and an inlet methanol flow rate of 0.096 mol/h.（4）CuO/ZnO/CeO₂/ZrO₂ catalyst with nanoporous structure was prepared by the glycol solution combustion method,and the influence mechanism of glycol content on catalyst was elucidated.A pore-in-pore hierarchical structure was formed after the catalyst was supported on the SiC porous ceramic,which increased the number of effective catalytic channels and improved the contact of the feed gas with the catalyst.The increase of glycol content could decease the catalyst particle size and increase the amount of residual carbon on the catalyst surface,thereby affecting the redox property of the catalyst.The catalyst loading amount on the ceramic support was about 20%weight of the whole support and the numerous rough pores of ceramic support significantly increased the catalyst loading amount and loading strength.The catalyst-loaded SiC porous ceramic support could achieve 100%methanol conversion rate at a reaction temperature of 280°C and an inlet methanol flow rate of 0.112 mol/h.（5）CuO/ZnO/CeO₂/ZrO₂ catalyst was prepared by the metal organic framework derivatization method,and the influence mechanism of precursor on catalyst was elucidated.Among the three derived catalysts,the catalyst derived from Cu/Zn-metal organic framework showed high S_BETvalue,good redox property and superior surface elemental state,and the catalyst particles were fine and uniform.The strong interaction between CuO and ZnO could prevent the sintering and agglomeration of CuO particles and promote the formation of solid solution.The catalyst washcoat exhibited good loading strength,and the catalyst-loaded cordierite honeycomb ceramic support could achieve 100%methanol conversion rate at a reaction temperature of 260°C and an inlet methanol flow rate of 0.112 mol/h.