| Hydrogen is an typical efficient and clean energy,which can simultaneously solve the energy crisis and environmental pollution.At present,hydrogen is mainly prepared by reforming hydrocarbons（especially natural gas and petroleum）,Seeking sustainable raw material of hydrogen production is the inevitable trend to hydrogen energy development.Ethanol is a kind of biomass with high hydrogen content,low toxicity,easy storage and renewable.Therefore,ethanol hydrogen production has been paid more and more attention because of its sustainable characteristics,among which ethanol steam reforming has become a research hotspot because of its high hydrogen production.There are two main types of catalysts for hydrogen production from steam reforming of ethanol:noble metal catalysts and non-noble metal catalysts.The noble metal catalyst has a high cost,and the non-noble metal catalyst has low cost and is widely concerned with the activity of the noble metal catalyst.In the non-noble metal catalyst,due to its outstanding C-C bond cleavage ability,Ni has become a rising star in the study of steam reforming catalyst for hydrogen production.However,Ni based catalyst is easy to be deactivated by sintering and carbon deposition due to the weak interaction between support and active components as well as the strong acid centers.Thus,the addition of the second active metal and rare earth metal may form stronger interaction with Ni and could decrease the strength of acid centers,which is advantageous to the dispersion of Ni and the prevention of its sintering.For this reason,Ni-Fe/γ-Al2O3 bimetallic catalyst was prepared,and the supportγ-Al2O3 was modified by the rare earth.The effects of different active components,different modified rare earths and different ratio of water to alcohol were studied.At the same time,different impregnation methods were also investigated.Meanwhile,the influence of different impregnation methods,Ni precursors and supports were also investigated in the catalytic steam reforming of ethanol to produce hydrogen,the main conclusions are as follows:（1）The different impregnation methods had great influence on the catalytic performance of the catalyst.The activity catalyst prepared by successive impregnation method is obviously higher than that prepared by co-impregnation method.The stability experiment shows that after 50 h stability experiment,the conversion of ethanol of the catalyst prepared by successive impregnation method was higher than87%,and the selectivity of hydrogen was above 70%.However,the conversion of ethanol of the catalyst prepared by co-impregnation method decreased to 80%and the selectivity of hydrogen decreased from 82%to 48%after 40 h online reaction.Obviously,the catalyst prepared by successive impregnation method has better stability.Comprehensive analysis shows that the catalyst prepared by successive impregnation method has the advantages of better dispersity of active components,smaller grain size of active phase,anti-sintering property and stronger resistance to carbon deposition.The stability test also showed that after 50 h stability test,the conversion of ethanol was higher than 87%,and the selectivity of hydrogen was more than 80%.（2）The results show that the activity of the catalyst modified by rare earth La is higher than that of other rare earths（Pr,Nd）.So the La promotes the dispersion of Ni,which is beneficial to the reduction of Ni particles.Comprehensive experiments show that that the addition of rare earths enhances the interaction between Ni and the support,which is beneficial to increase the resistance to carbon deposition of the catalyst.The investigation of the effect of supports confirmed that the catalyst usingγ-Al2O3 as the carrier had excellent catalytic activity.However,the activity of the catalyst with ZSM-5 as the carrier was the lowest.（3）Through the study of different Ni precursors,it can be found that the catalysts prepared with nickel nitrate and nickel citrate as precursors have higher catalytic activity than the nickel chloride.The results of the study of the loading amount of Ni,Fe and La show that the best catalytic activity was obtained when the loading amount of Ni,Fe,La was 8 wt.%,10 wt.%,6 wt.%,respectively.It is found that the increase of ethanol conversion and hydrogen selectivity is obvious when the La and Fe is added to Ni-γ-Al2O3 catalyst. |
