Preparation And Catalytic Properties Of A Silicon-Based Co/Ni Ethanol Reforming Catalyst For Hydrogen Production

The development of clean energy such as hydrogen instead of fossil energy can greatly alleviate the problem of energy shortage and environmental pollution.Ethanol steam reforming for hydrogen production has attracted great attention in recent years since ethanol is low-toxicity and renewable materials for high-efficiency hydrogen production.Non-noble metal Co/Ni catalysts,due to the abundant reserve and high catalytic activity,are widely used in the catalytic ethanol reforming to produce hydrogen.However,the considerably low hydrogen selectivity,especially their poor stability,limit their extensive application in the steam reforming of ethanol.Previous studies have shown that carbon deposition on the catalyst surface and aggregation of the active nanoparticles are responsible for catalyst deactivation in reforming process.The development of catalysts with high hydrogen selectivity,excellent stability and low cost is the key to high-efficiency hydrogen production in ethanol reforming.In this thesis,the supported Co/Ni catalysts on highly ordered mesoporous MCM-41 and Si/Al solid solution SiAlON have been successfully prepared,the microstructure and morphology of them were characterized,and the catalytic performance for hydrogen production via ethanol steam reforming was investigated.1.Co/MCM-41 catalyst with porous morphology was prepared by one-step procedure(Co nanoparticles are highly dispersed,particle size of about 2~3 nm).The as-prepared Co/MCM-41 exhibited higher catalytic activity and hydrogen selectivity as compared to the Co/SiO2 catalyst,hydrogen selectivity was about 64.47 %,significantly higher than that of Co/SiO2(47.20%)at 400?.The strong metal-support interaction and the nano-confinement effect of MCM-41 limited the migration and growth of the Cobalt nanoparticles during ethanol reforming reaction,and thus improved the resistance to aggregation.The ordered mesoporous structure was remained even after 28-hour ethanol reforming reaction at 500?,and hydrogen selectivity remained at about 65%.The carbon deposition on the surface of used catalyst was only 3%.2.The Ni/Si6-ZAl ZOZN8-Z catalysts with different Nickel loadings were prepared by using Si6-ZAl ZOZN8-Z with different Si/Al ratios.The results showed that the Si/Al ratio and the Nickel loading could significantly affect the performance of the catalyst for hydrogen production by ethanol reforming.The ethanol conversion and hydrogen selectivity at 500? for the catalyst Ni/Si4Al2O2N6-1.0w were 100% and 80%,respectively.Sixteen-hour ethanol reforming reaction demonstrated that this catalyst possessed excellent stability,and negligible change in ethanol conversion and hydrogen selectivity was observed.