Low-Temperature Catalytic Steam Reforming Of Corncob Pyrolysis Tar Over Oxygen-Vacancy-Rich Co/Ce-C

Our country is abundant in biomass energy.Biomass gasification is considered as one of the most effective ways to utilize biomass resources but the tar produced in the process would seriously affect the stable operation of the gasification system.Among the technologies for tar removal,Catalytic reforming of tar is considered as the most potential one.The development of a low-cost,high-activity and high-stability catalyst is the key of tar reforming.using modified lignite as carbon precursor has shown good activity in the steam reforming of biomass,but the low-temperature reforming performance of the catalyst needs further improvement because the carbon support is easily depleted at high temperatures.Due to the excellent oxygen migration ability,Ce could effectively enhance the uptake of reactants.In this thesis,a series of Co/Ce-C were prepared using lignite as the carbon precursor.Firstly,the effect of metal ratio and reaction conditions was explored on an in-line stationary bed using toluene as model compound,on which suitable conditions were selected for 100 h stability experiments,then a two-stage stationary bed was used to compare Co/5Ce-C with commercial Ni/Al₂O₃ catalysts in the cycling experiments of steam reform of corn cob.The experimental phenomena and catalyst characterization were combined to analyze the causes of catalyst deactivation and the promotion effect of Ce on the reaction.In this study,a series of Co/Ce-C catalysts were prepared using acid-washed oxidized lignite（OAWSL）as the support.In the steam reforming of toluene experiments,it was found that the highest conversion and the most gas production were achieved under the conditions of Co/5Ce-C,Steam-to-carbon ratio（S/C）of 3.4 and weight hourly space velocity（WHSV）of 2400 m L h^-1 g^-1,the catalysts still had 95%toluene conversion after 100 h of reaction under these conditions.According to the characterization of the catalysts,the strong interaction between Ce and Co enhances the dispersion and reduction of the metal,resulting in smaller metal particle size and more Co⁰ sites.the incorporation of Ce also enhances the number of oxygen vacancies in the catalytic system and improves the absorption of water In the Steam reforming of corn cob,the Co/5Ce-C catalyst achieved a gas yield of 97.2 mmol/g-corn cob（daf）and still had a high tar conversion and gas yield after 10 cycles,which was higher than the reforming performance of commercial Ni/Al₂O₃ catalysts with a higher number of cycles.The spent catalyst characterization revealed that Co/5Ce-C with a large number of reactive sites and high content of oxygen vacancies maintained less carbon accumulation and more stable metal sites after the reaction.These inexpensive and simple Co/Ce-C catalysts show good potential as catalysts for industrial reforming.This thesis has 41 pictures,9 tables and 116 references.