Ni-Mg/RHA催化剂催化水蒸气焦油模型化合物重整反应研究

Steam reforming tar model compound with Ni-Mg/RHA catalyst

以甲苯为生物质焦油模型化合物,以生物质燃烧产物稻壳灰为载体,采用共浸渍法制备Ni-Mg/RHA催化剂,研究Ni-Mg/RHA催化剂对甲苯水蒸气催化重整的性能。在固定床反应装置中考察了Ni和Mg的负载量、反应温度和水/碳(水和碳的质量比,简称为水/碳或S/C)对甲苯转化率和气体产物组分的影响,采用XRD、BET、SEM等方法对反应前后催化剂进行表征分析。结果显示,稻壳灰(rice husk ash,RHA)作为单金属Ni基催化剂的载体具有一定的催化活性;负载MgO后,MgO改善了Ni/RHA催化剂中活性金属Ni的分散度,与NiO相互结合形成NiMgO固溶体活性中心,显著提升了Ni/RHA催化剂的催化活性和抗积炭能力,Mg负载为6%时性能最佳,甲苯转化率高达98.6%;3Ni-6Mg/RHA催化剂的最佳反应温度为700℃,S/C为3,具有良好催化稳定性。研究结果表明,在MgO存在的情况下,稻壳灰可作为镍基催化剂载体。

Biomass gasification is a technology that converts biomass into gas fuel.However,complex tar compounds will be formed in 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 people’s attention due to its high activity and low cost.Among them,deactivation caused by coke deposition is the biggest challenge of this technology.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.At present,there is no report on the steam reforming of biomass tar with a catalyst supporting Ni-Mg active components on the by-product RHA(rice husk ash,RHA)of biomass pyrolysis in the treatment of tar with nickel-based catalysts.This article introduces a promoter and RHA as a carrier to improve the catalytic performance of the catalyst.It will be of great significance for improving the economic efficiency and anti-coking performance of the catalyst.Biomass combustion product of rice husk ash was selected as the carrier,and Ni-Mg/RHA catalyst was prepared by co-impregnation method.The catalytic performance of Ni-Mg/RHA for steam reforming of toluene was studied using toluene as a model compound of biomass tar.The effects of Ni and Mg loadings,reaction temperature and S/C ratio on toluene conversion and gas product composition were investigated in a fixed-bed reactor.The catalysts before and after reaction were characterized by XRD,BET and SEM.The results showed that RHA as a support of single metal Ni-based catalyst had a certain catalytic activity.Compared with Ni/RHA and Ni/HZSM-5,RHA is a biomass combustion product with small specific surface area and simple pore size structure.In the Ni/RHA catalyst,the active metal is gathered in the outer layer of the catalyst,and there is no porous structure inside.After catalytic reforming of toluene,carbon deposition is easy form to cover the active site,resulting in the low catalytic activity of Ni/RHA catalyst supported by single metal Ni.After adding MgO modification,the catalyst surface area and pore volume was increased and the surface generated porous structure,indicating that the MgO load improved the specific surface area and pore volume of RHA-supported catalyst providing more reaction sites for toluene and water vapor.Results of crystal structure analysis showed that after adding MgO style,Ni characteristic peak did not appear on the Ni-Mg/RHA.NiMgO characteristic peak,peak diffraction angle shifted to the left.Because of the interaction between NiO and MgO style,NiMgO crystal phase structure more easily formed under the low degree of diffraction is detected,indicating that MgO style improves the dispersion of active metal Ni and provides NiMgO solid solution activity sites,which improved the catalytic performance.When Mg load was 6%,the performance was the best,with the toluene conversion rate of 98.6%.The optimal reaction temperature of 3Ni-6Mg/RHA catalyst was 700℃and S/C was 3,having good catalytic stability.The optimal reaction temperature of 3Ni-6Mg/RHA was 700℃and S/C was 3,having good catalytic stability.The feasibility of using rice husk ash as the support of nickel-based catalyst in the presence of MgO is confirmed.