Preparation And Performance Study Of Al-based Heat Storage Catalyst Based On Catalytic Methane Combustion

Thermal runaway of the catalyst bed is a serious problem in exothermic chemical reactions,which can result in catalyst deactivation and a decrease in productivity or selectivity.Studies have shown that microencapsulated phase change materials can achieve a form-stable structure and induce thermal inertia of the system and improve material selectivity,so they can be used as energy storage buffers to mitigate the rapid and potentially dangerous temperature shift.The reactor reinforced by the phase change heat storage material has excellent anti-interference performance,and the presence of the phase change heat storage material highly stabilizes the bed temperature and indirectly enhances the performance of the catalyst particles.To solve the problems that the temperature distribution of the reactant bed in the fixed bed reactor is not uniform and the hot spot is easy to occur in the catalytic reaction,this paper proposed to combine the phase change heat storage material and the catalyst material to construct a regenerative catalyst.The regenerative catalyst can balance the reactor bed temperature,reduce the occurrence of hot spots,and make the system run more stable.To solve the low thermal conductivity of microencapsulated phase change materials and the agglomeration of carbon-based materials,we proposed a new strategy to improve the stability and thermal conductivity by depositing carbon on the surface of Al@Al₂O₃ phase change composite via in-situ catalytic methane decomposition.In this method,the core material aluminum is firstly coated by nano Ni species which can promote the oxidation of the surface layer of Al to Al₂O₃ during the calcination in air.In addition,the carbon will be produced on the Al@Al₂O₃composite when it is submitted to CH₄ flow at high temperatures due to the catalytic methane decomposition by Ni species,obtaining the Al@Al₂O₃-C MEPCM.The Al@Al₂O₃-C phase change composite exhibits high phase transition enthalpy?266 J/g?good thermal conductivity?8 W/m·K?,and low degree of supercooling in the exothermic process during cooling.At the same time,carbon produced by in-situ catalytic methane decomposition clinging tightly to the surface of the materials can hardly agglomerate,and obtain high dispersion with hydrogen as a coproduct.In addition,the nesting of the deposited carbon in shell makes the surface structure of the material more dense and stable,showing excellent stability in successive heating/cooling cycle.The Co₃O₄/?SiAl@Al₂O₃?heat storage functionalization catalyst was successfully prepared by rapid coprecipitation method on the SiAl@Al₂O₃ phase change material.By analyzing the results of each characterization,the application effect of phase change materials in the field of catalysis was examined.The results show that the Co₃O₄/?SiAl@Al₂O₃?heat storage functionalization catalyst can not only achieve catalytic combustion of methane,improve the conversion of methane,but also prolong the reaction time in the process of cooling and make the methane reaction more complete.When the ratio of Co₃O₄ and SiAl@Al₂O₃ in the Co₃O₄/?SiAl@Al₂O₃?heat storage functionalization catalyst is 7:3,the heat storage and catalytic effect is the best.