Study On Cu/Ce_0.8Zr_0.2O₂/SiC Monolithic Catalyst For Hydrogen Production By Methanol Steam Reforming

Methanol steam reforming to hydrogen production is the main way to provide hydrogen source for fuel cell.However,at present,most of the catalysts used in the reaction are traditional particle catalysts,and the particle catalysts have large bed pressure drop.Low heat and mass transfer efficiency and low operating space speed.In this paper,Ce_0.8Zr_0.2O₂ solid solution coating material was prepared by sol-gel method using the formed honeycomb SiC ceramics as support,and then the active components were loaded by immersion method on the basis of the previous research of the Cu based catalyst in our research group.A series of monolithic catalysts were prepared.The effects of cerium source,concentration of cerium-zirconium precursor and amount of cerium-zirconium coating on the catalytic performance of the monolithic catalysts were discussed.The specific contents of the study were as follows:（1）The cerium-zirconium sol with Ce（NO₃）₃·6H₂O and（NH₄）₂Ce（NO₃）₆as cerium source were prepared by sol-gel method,which was used as coating material of SiC ceramic monolithic catalyst.Two kinds of CuO/Ce_0.8Zr_0.2O₂/SiC catalysts were prepared with calcination of active component CuO by impregnation method.The catalysts were characterized by XRD,SEM,BET.The experimental results showed that CuO/Ce_0.8Zr_0.2O₂/SiC catalyst with Ce（NO₃）₃·6H₂O as cerium source had good catalytic activity and thermal stability.This was due to the uniform distribution of the Ce_0.8Zr_0.2O₂ solid solution coating on the surface of the SiC carrier in the CuO/Ce_0.8Zr_0.2O₂/SiC catalyst,which increased the loading area of the active component.CuO formed a material with specific structure and distributed uniformly on the surface of Ce_0.8Zr_0.2O₂ solid solution coating.（2）The effect of cerium-zirconium precursor concentration on the performance of the catalyst was investigated.The catalysts were characterized by XRD,SEM,BET and other characterization methods.It was found that when the concentration of Ce（NO₃）₃·6H₂O and the concentration of Zr（NO₃）₄·5H₂O were 1.6 mol/L,and molar ratio was 4/1,the B₂-CuO/Ce_0.8Zr_0.2O₂/SiC catalyst had better catalytic performance.When the reaction temperature was 340℃,the molar ratio of water to alcohol was 1.2,the space velocity of methanol was 1940 h^-1,the conversion of methanol was65.6%,the content of CO in reforming gas was 0.79%,the hydrogen yield was 469.4 mL·kg^-1_cat·s^-1.（3）The effect of cerium zirconium coating on the performance of the whole catalyst for methanol steam reforming to hydrogen production was investigated.The results show that the coating of Ce_0.8Zr_0.2O₂ solid solution coating has obvious effect on the catalytic performance.When the Ce_0.8Zr_0.2O₂ solid solution coating is thin,the supported CuO is less and the catalytic activity is poor.When the Ce_0.8Zr_0.2O₂ solid solution coating is too thick,there is obvious pore blocking phenomenon,and the agglomeration of CuO is serious,which affects the catalytic performance.When the coating amount of Ce_0.8Zr_0.2O₂ solid solution coating is 12.84%,the catalytic performance of CuO/Ce_0.8Zr_0.2O₂/SiC catalyst is better when the molar ratio of water to alcohol is 1.2 and the space velocity of methanol gas is 1940 h^-11360℃.The conversion of methanol was 90.1%,the hydrogen production rate was 624.5 mL·kg^-1_cat·s^-1,and the CO selectivity was 4.4%.