Study On Catalytic Thermal Conversion Of Biomass With Nickel-based Hierarchically Structured Catalyst

Biomass energy has the characteristics of low combustion pollution,renewable,easy to obtain,convenient transportation and storage,which providing a new direction for solving energy and environmental problems.Effective conversion of tar macromolecule and adjustment of H₂ and CO ratio need to be solved in the process of catalytic pyrolysis of biomass for high quality syngas.Traditional supported catalysts are easy to agglomeration or coke deposition,because of poor dispersion of active centers which leads to rapid reduction of their catalytic activity.Therefore,this paper takes advantage of hierarchically structured materials,which are able to solve the problems about the traditional catalysts and further increase the gas yield and improve quality of gas and tar by designing and optimizing the morphology and structure of Ni-based catalysts.The paper synthesized One-dimensional rod Ni-Zn catalytic,two-dimensional laminar Ni-Al catalytic and three-dimensional flower-like Ni-Al catalytic.Discussed the effects of different calcination temperatures on the morphology,thermal stability and catalytic by characterization analysis.With the increase of calcination temperature,The content of Ni₃Zn C_0.7was increased,while the content of Ni and Zn O was decreased,and its specific surface area was increased and then stayed about one-dimensional rod Ni-Zn catalyst;the content of Ni,Ni O and Ni Al₂O₄ was increased and its specific surface area was increased and then decreased about two-dimensional laminar Ni-Al catalyst;the content of Ni was increased,and its specific surface area was increased and then decreased about three-dimensional flower-like Ni-Al catalyst.In this paper,the catalytic pyrolysis of rice husk was experiment in a fixed bed reactor.temperature of catalysis pyrolysis was 600℃,The effect of calcination temperature on catalytic activity was investigated.With the increasing calcination temperature,the gas yield of one-dimensional rod Ni-Zn catalyst was increased and then decreased,the highest gas production was 625 ml/g biomass,the production of H₂ was 297 ml/g biomass and the tar yield was 20%at 600℃;the gas yield of two-dimensional laminar Ni-Al catalyst was increased and then decreased,the highest gas production was 692 ml/g biomass,the production of H₂ was 340 ml/g biomass and the tar yield was 20%at 700℃;the gas yield of three-dimensional flower-like Ni-Al catalyst was increased and then decreased,the highest gas production was 737 ml/g biomass,the production of H₂ was 354 ml/g biomass and the tar yield was 15%at 600℃.Aromatic and phenolic compounds were the most dominating products,with the increase of calcination temperature,the content of phenols was increased,content of aromatic was decreased on the effect of one-dimensional rod Ni-Zn catalyst;the content of phenols was increased,content of aromatic was decreased on the effect of two-dimensional laminar Ni-Al catalyst;the composition didn’t change much on the effect of three-dimensional flower-like Ni-Al catalyst.In order to further study the catalytic activities of the three catalysts.At their respective optimal morphology structure,research the effect of gas production and tar conversion by different pyrolysis temperature（500℃-800℃）.According to experiment analysis,the gas production was increased and the tar yield was decreased with the increasing catalytic temperature,one-dimensional rod Ni-Zn catalyst at 800℃,the highest gas production was776 ml/g biomass,the production of H₂ was 305 ml/g biomass and the tar yield was 11%;two-dimensional laminar Ni-Al catalyst at 800℃,the highest gas production was 785 ml/g biomass,the production of H₂ was 390 ml/g biomass and the tar yield was 17%;three-dimensional flower-like Ni-Al catalyst at 800℃,the highest gas production was 1015 ml/g biomass,the production of H₂ was 511 ml/g biomass and the tar yield was 11%.Aromatic and phenolic compounds were the most dominating products.With the increasing catalytic temperature,one-dimensional rod Ni-Zn catalytic and two-dimensional laminar Ni-Al catalytic were conducive to gained aromatic,but for three-dimensional flower-like Ni-Al catalyst,the content of aromatic was increased and then decreased,and the content of phenols was decreased.Based on this,the specific surface area could only limited affect the activity of the catalyst,there are a deep effect about the morphology and phase composition.The catalytic active elements are orderly assembled into hierarchically structural materials,which make the active center highly disperse and fully expose,making it easy to pyrolysis products of rice husks and promote their decomposition in high-quality gas and biological oil.