Study Of Ni-Based Catalyst For Steam Reforming Of Biomass Tar Model Compounds

Nowadays,with the depletion of fossil fuels,biomass is a very promising renewable energy source.Biomass gasification is a technology that converts biomass into gaseous fuel.However,complex tar compounds are formed during the process,resulting in reduced gasification efficiency and blockage of downstream equipment.Catalytic steam reforming has been widely used for tar removal.Nickel-based steam reforming catalysts have attracted attention because of their high activity and low cost.Among them,the deactivation caused by coke deposition is the biggest challenge of this technology.Modification The nickel-based catalyst came into being.The loading of metal Ni in the modified nickel-based catalyst not only affects the activity of the nickel-based catalyst but also restricts the preparation cost.Based on the current insufficient research on the modification of nickel-based catalysts with low Ni loading at home and abroad,this paper introduces a promoter to improve the catalytic performance of low Ni loading.The research conclusion is of great significance for improving the economy and anti-coking performance of the catalyst.In this paper,HZSM-5 and rice husk ash（RHA）are selected as catalyst carriers,alkaline earth metal Mg O and rare earth metal Ce O₂ are used as catalyst promoters,toluene is tar model compound.Study on toluene steam reforming of modified nickel-based catalysts with low Ni loading.First,the effects of Ni and Mg O loading on toluene conversion efficiency,gas product distribution and carbon deposition rate were investigated.The results show that for the single metal Ni/HZSM-5 catalyst,the low（3%）Ni loading3Ni/HZSM-5 catalyst exhibits weak catalytic activity;the high（9%）Ni loading9Ni/HZSM-5 catalyst exhibits catalysis Problems such as unstable performance and serious carbon deposits.After loading Mg O,the catalytic activity of the 3Ni/HZSM-5 catalyst in toluene steam reforming is improved.When the Mg O loading is 6%,the toluene conversion rate of the 3Ni-6Mg/HZSM-5 catalyst exceeds the single metal 9Ni/HZSM-5 The level of the realization of Mg O to replace part of the catalytic effect of Ni.In addition,the addition of Mg O inhibited the formation of coke on the catalyst surface,and the carbon deposition rate was only 0.47 wt%.The characterization of the catalyst before and after the reaction revealed that the high catalytic performance of Ni-Mg/HZSM-5 was attributed to the formation of the active center of Ni O-Mg O solid solution,and the ability of the catalyst to resist carbon deposition was attributed to the increase in the basicity of the catalyst surface.In summary,the loading of Mg O plays a significant role in improving the catalytic activity and anti-coking performance of low Ni-loaded catalysts.Modification of 3Ni-6Mg/HZSM-5 catalyst by adding rare-earth metal Ce O₂,the optimal combination of Ce O₂ loading and 3Ni-6Mg-Ce/HZSM-5 catalyst performance was explored,and it was para-toluene under different reaction conditions The effects of conversion efficiency,gas product distribution,and coke deposition rate show that Ce O₂and Mg O play a synergistic role,Ce O₂ improves the reducibility of the catalyst,and improves the catalytic reforming activity of the 3Ni-6Mg/HZSM-5 catalyst and Anti-coking ability,the best Ce loading is 1 wt%.The optimal reaction temperature is 700℃,S/C is 3,volume space velocity is 3000h^-1,the steam catalytic reforming performance is the best,the toluene conversion rate is as high as 97.3%,the catalyst carbon deposit after the reaction is only 0.37 wt%.After 10 hours of continuous stability testing and three repeated cycles of use,3Ni-6Mg-1Ce/HZSM-5 maintained a high catalytic activity,and no catalyst deactivation occurred.Therefore,Ce O₂ further improves the catalytic activity and anti-coking performance of the Ni-Mg/HZSM-5 catalyst with low Ni loading.Due to the high price of HZSM-5,low-cost RHA was used to replace HZSM-5,and the research on the steam reforming performance of RNi catalyst with low Ni loading on toluene was discussed.Studies have shown that the addition of Mg O improves the specific surface area and pore volume of the RHA-supported catalyst,provides more reaction sites and active sites for toluene and water vapor,and improves the catalytic performance.The performance is optimal when the Mg O loading is 6%.The addition of Ce O₂ reduces the catalytic activity of 3Ni-6Mg/RHA.The optimal reaction conditions for the 3Ni-6Mg/RHA catalyst are temperature 700℃,S/C 3,volume space velocity 3000 h^-1,toluene conversion rate up to 98.6%,and carbon deposit after the reaction is only 1.78 wt%.It maintains a high catalytic activity in the 8 hour continuous stability test.The feasibility of chaff ash as a nickel-based catalyst carrier in the presence of Mg O was proved.