Research On Catalytic Cracking And Steam Reforming Of Model Tar Based On Ni/Ca₁₂Al₁₄O₃₃

Catalytic conversion of biomass tar could not only remove tar and but also increase gas production,which is a very potential tar removal method.The key of tar catalytic conversion is how to select the catalyst with high economy and catalytic activity.In this study,catalytic cracking and steam reforming experiments were made with toluene as a model compound based on catalyst Ni/mayenite(Ca₁₂Al₁₄O₃₃ or C₁₂A₇),which combines Ni?high activity?and mayenite?excellent carbon and H₂S resistance prooerty?.The main contents and conclusions of this study are summarized as follows:?1?Ca₁₂Al₁₄O₃₃ as support was prepared by high temperature sintering method and Ni/Ca₁₂Al₁₄O₃₃ was prepared by impregnation method with nickel nitrate hexahydrate.The results show that the Ca₁₂Al₁₄O₃₃ which surface area is15.51 m²/g could be prepared by calcination of 4h in the presence of air;the diffraction peaks of Ca₁₂Al₁₄O₃₃ and NiO were also observed in the X-ray diffraction?XRD?patterns of the sample loaded nickel?2?The effects of reaction temperature,Ni loading on catalytic gas composition?H₂yield and the amout of carbon deposition were researched in a laboratory scale fixed-bed reactor when the catalytic cracking of toluene was carried out.Results show that the optimum reaction temperature and Ni loading of Ni/Ca₁₂Al₁₄O₃₃3 were 700°C and 8wt%,under this condition,the H₂ yield by catalytic cracking of toluene was 0.74L/g,the content of H₂ volume is 73.03%;the carbon deposition rate of catalyst is 18.30wt%.After the reaction,the SEM-EDS of catalyst demonstrated that the catalyst surface exists carbon deposition,which could reduced catalytic activity.?3?In order to further reduce the carbon deposition,Ni8/C₁₂A₇ was used as catalyst in the catalytic reforming of toluene.The research found that steam reforming can increase the H₂ yield and carbon conversion;reduce the carbon deposition.In the temperature of 700°C S/C?steam/carbon ratio?=2.5,the content of H₂ volume,H₂ yield,carbon conversion and the carbon deposition rate is 64.02%,2.75L/g,91.03%,1.89wt%respectively.Sintering and carbon deposition were not observed after the reaction.?4?Ni-CaO/Ca₁₂Al₁₄O₃₃ catalysts,which were prepared by different are used as catalyst in the study of toluene steam reforming.Results show that Ca/Al ratio contribute to the H₂ yield and the content of H₂ volume.The H₂ yield and the content of H₂ volume increased to 3.11L/g and 68.34%when Ca/Al ratio,reaction temperature and S/C is1.71,700°C and 2.5,respectively.In the catalyst of high Ca/Al,the CaO enhanced the steam reforming reaction of toluene.