Research On The Application Of Ni-CaO-La₂O₃ Catalyst In The Steam Reforming Of Ethanol For Hydrogen Production

With the development of the times and the progress of the society,the demand of energy is growing and the dependence on energy is also increasing.However,the normal fossil energy is limited and nonrenewable.In addition,the environmental pollution problem has been caused by the use of the fossil energy,which then leads to some troubles to human’s daily life.Therefore,the importance and urgency of the development and utilization of new energy has become a broad consensus of the international community.The hydrogen energy is considered as the most promising alternative energy because of its high combustion heat value and no pollution to the environment.Ethanol is an ideal carrier for the renewable hydrogen because it can be produced by biomass fermentation,and it is low cost,non-toxic,easy to store and transport.Therefore,ethanol has been widely used for hydrogen production.In particular,ethanol steam reforming（ESR）has been studied mostly.It is difficult to find the robust catalysts with good catalytic activity and long-term stability.At present,there are two kinds of catalyst systems for ESR:noble metal catalysts and non noble metal catalysts.Considering the low cost of non noble metal catalysts and their comparable activity to noble metal catalysts,the research on non noble metal catalysts has become a hot topic.Among them,the nickel-based catalyst is one of the most promising catalysts because of its good ability of breaking C-C,low cost and wide availability.In this work,a series of Ni-CaO-La₂O₃catalysts with different nickel,lanthanum and calcium contents have been prepared by sol-gel method.Moreover,the microwave heating is combined with sol-gel method to prepare Ni-CaO-CeO₂ and Ni-CaO-La₂O₃ catalysts to improve the preparation efficiency and reduce the preparation time.The influence of nickel content and lanthanum content,calcium and lanthanummetals,different rare earth elements,different zirconium content and different preparation methods on the activity of the catalyst were studied.The catalysts are characterized by XPS,BET,XRD,H₂-TPR,TEM,etc..The main results are as follows:（1）For catalysts with nickel content<20%,higher activity is achieved over the Ni-CaO-La₂O₃ catalysts with higher nickel content,the activity starts to decrease over Ni-CaO-La₂O₃ catalysts with nickel content>20%.The highest activity is obtained over the Ni-CaO-La₂O₃ catalysts with nickel content of 20%.The addition of lanthanum improves the conversion of ethanol the selectivity of hydrogen,and the best performance achieves at La content of 10%.（2）The addition of La can promote the uniform dispersion of the active Ni and Ca over the catalysts,resulting in smaller nickel particles.Therefore,Ni-CaO-La₂O₃ catalyst can completely transform ethanol at a lower temperature of 450℃;the addition of appropriate proportion of Ca can significantly improve the activity of the catalyst,resulting in higher hydrogen concentration.In addition,the stability of 20Ni-CaO-La₂O₃ catalyst was investigated.A long-term stability can be achieved on 20Ni-CaO-10La₂O₃catalyst during 123 h of time-on-stream at 550℃.（3）For 20Ni-CaO-10CeO₂ catalysts prepared by singel sol-gel method and the combination of microwave heating and sol-gel method,the ethanol conversion of 100%has been achieved at the reaction temperature of 450℃-700℃,and 20Ni-CaO-10CeO₂-W catalysts can obtain the higher selectivity of hydrogen than 20Ni-CaO-10CeO₂-C catalysts when the reaction temperature is above 500℃.Importantly,the stability of 20Ni-CaO-10CeO₂-W catalyst is very good at550℃with no deactivation after 200 h of reaction.