Preparation Of Ni/Char Based Catalyst For Low Temperature Catalytic Steam Reforming Of Tar

The presence of tar in the crude syngas will cause a series of problems such as blockage of pipelines,downstream equipment corrosion,and deactivation of catalysts in the refining process.Therefore,the removal of tar from crude syngas is the key to the large-scale application of gasification technology of low rank coal and biomass.Catalytic reforming is considered as the most promising tar removal method due to its high tar removal efficiency and mild reaction conditions.In this study,the purpose is to prepare Ni/Char based catalyst which has high catalytic activity.The activity differences of catalysts prepared by different Ni loading methods are compared.The effects of the oxidation degree of support on the activity of catalysts prepared by ion exchange are analyzed.Furthermore,intrinsic correlation between the oxidation degree of support and catalytic activity is explored by ICP analysis,XRD spectroscopy,and TEM.In addition,toluene and phenol are used as tar model compounds,and the self-designed fixed-bed reactor system is employed to evaluate the catalyst activity.The influences of P loading methods on catalyst activity are investigated,and the reasons for the different catalytic performance caused by loading conditions are analyzed.Besides,in order to ensure the activity and stability of the Ni-P/Char catalyst,the catalytic temperature and steam flow rate are optimized.Finally,the catalytic performance of different catalysts for tar steam reforming is compared,and the distribution of gas-phase products and liquid-phase products is detailed.The results show that the activities of catalysts prepared by different Ni loading methods are significantly different.The Ni loaded catalyst prepared by ion exchange of Yining raw coal has the best catalytic performance.Meanwhile,the oxidation degree of coal samples has a significant effect on the catalyst activity.As the mass fraction of oxidant increases,the loading and crystallite size of Ni gradually increase,it is also found that there is an optimal matching value between them which affects the performance of catalyst.The activity of catalysts prepared by pretreatment of coal samples with H₂O₂ is better than that prepared by HNO₃ pretreated coal samples.Compared with Ni/Char catalyst,the catalytic performance of the Ni-P/Char catalyst prepared under co-loading of Ni and P has been significantly improved.The catalyst activity is the highest when the p H of the solution is 11and the concentration of P is 0.2 mol/L.At 600 ^oC and 600 m L/min of steam flow rate,the catalyst has high activity and good hydrothermal stability.Compared with Ni/?-Al₂O₃,the steam reforming of tar in the presence of Ni-P/Char catalyst achieves the highest gas yield and the lowest tar yield.