| The main objective of this paper is to study catalysts for biomass gasification tar removal. The Ni/modified olivine catalyst was prepared for hydrogen production from biomass used in solid heat-carrier system.The modified olivine(MO) support was made by molding the olivine and calcium aluminate cement(CA) and the catalyst was made by impregnation method.The modified catalyst has higher activity and stability.The operation conditions and preparation parameters are determined by using benzene as the model compound in a fixed bed reactor.The catalyst preparation parameters contain two aspects.One is support preparation which contains binder addition,calcination temperature and the addition of structural promoter.The other is active components loading which contains loading methods and promoter addition. Experimental results showed that 99.4%carbon-conversion can be obtained at the reaction temperature 800℃,benzene weight hourly space velocity(WHSV) 0.8h-1,steam to carbon molar ratio(S/C) 2.5.The contents of the product gas were H2 64.3 vol.%,CO 22.3 vol.%and CO2 13.4 vol.%.In addition,no obvious deactivation of the catalyst was observed during 500min sequential test.The X-ray diffraction(XRD) characterization demonstrated a smaller particle size and a better dispersion of NiO for the NiO/MO catalyst than that for the NiO/Olivine.Reaction temperature,steam to carbon ratios and weigh hourly space velocity significantly influenced the modified catalyst activity throught the study of operation conditions.The appropriate operation conditions were:reaction temperature higher than 750℃, S/C higher than 2.0 and WHSV not higher than 1.1h-1.Attapulgite and mixed binder(cement and attapulgite) were also used to modify the olivine support.Through experimental comparison,the attapulgite modified olivine catalyst and the mixed binder modified olivine catalysts were more active than the nickel olivine catalyst,and the two new catalysts have good self-reduction ability. |
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