Experimental Study On Electro-catalytic Methane Steam Reforming To Hydrogen-rich Syngas With Ni-based Catalyst

Hydrogen is a kind of efficient,high-quality and clean energy which occupies an important position in the world's energy consumption structure.At present,methane steam reforming is the main industrial hydrogen production method,Ni-based catalyst is the most commonly used catalyst in methane steam reforming.Despite of the industrialization of the methane steam reforming,the following problems,such as high reaction temperature,easy carbon deposition inactivation of catalyst and poor stability,still exist in the current methane catalytic reforming.In recent years,the electrocatalyst reforming has been paid some attention.It has been confirmed that the electrocatalytic has a positive effect on improving the catalytic conversion efficiency and inhibiting the catalyst carbon deposition in the reforming of bio-oil and the conversion of biomass tar.However,there is no report about the electrocatalysis of methane steam reforming.Therefore,this paper expects to solve the existing problems on steam reforming of methane in the way of improving its process.First of all,the thesis uses Ni/?-Al2O3 and its use MgO,CaO modified catalysts to test the effectiveness of "electrocatalysis" in steam reforming of methane,while Ni/y-Al2O3,Ni-MgO/?-Al2O3 and Ni-CaO/?-Al2O3 three catalysts were prepared.The effect of current intensity on CH4 conversion,H2 yield and CO selectivity for methane steam reforming impact were investigated under different operating conditions.The results indicated that by introducing the electric current,the CH4 conversion can be improved and H2 yield also increases.Such effects were more intensive under lower reforming temperatures.Among the three catalysts,Ni-CaO/?-Al2O3 catalyst exhibited the best catalytic efficiency,with the CH4 conversion over 95%under conditions of 4.5 A,molar ratio of water vapor(water/carbon ratio,S/C)of 3,and 700?.Stability tests of the catalysts showed that the electric current could improve the stability of catalysts and delay the deactivation caused by coke deposition.In order to study the role of electric current in the steam reforming of methane,the catalyst after the stability test was characterized.And it is found that the presence of electric current enhanced the reduction degree of NiO in the catalyst which can increase the catalytic efficiency.At the same time,the presence of electric current also promotes the molecular dissociation which makes the catalyst have higher reforming efficiency under low temperature.The passage of current also inhibit NiCx conversion to graphite carbon,which could delay catalyst deactivation caused by carbon deposition over reactive sites.Combined with the role of electrocatalysis in steam reforming of methane,the catalyst used is changed to Ni-CeO2/Al2O3-MgO for further enhancement of the electro-catalytic steam reforming of methane efficiency under low temperature conditions.Experiments were performed to investigate the effects of electric current intensity,reforming temperature,and S/C to methane on CH4 conversion,H2 yield,CO selectivity and catalyst stability.Ni-CeO2/Al2O3-MgO catalyst with the CH4 conversion over 95%under conditions of 4.5 A,S/C of 3,and 600? has no obvious deactivation after 9h of stability test.Control experiments were performed with Ni-CeO2/Al2O3-MgO catalyst,which was compared with Ni/Al2O3 and Ni/Al2O3-MgO catalysts.The characterization results of control experiments show that the higher reforming efficiency and good stability of Ni-CeO2/Al2O3-MgO catalyst at low temperature are the results of the combination of catalytic properties and electrocatalysis.This paper provides a new method and idea for solving the existing problems of methane steam reforming process,it also provides theoretical guidance for the follow-up related research.