Study On Preparation Of Biomass Char-supported Metal Catalyst And Its Catalytic Cracking Tar Characteristics

The energy shortages and environmental pollution problems,which caused by the excessive use of fossil energy,forcing countries around the world to devote to the development of renewable,low-polluting energy sources.Biomass energy has received widespread attention due to its advantages of zero carbon dioxide emissions,low nitrogen and low sulfur and sustainable regeneration.Pyrolysis gasification can directly convert biomass into high-quality synthesis gas,which is an effective way to achieve efficient utilization of biomass energy.Tar is an inevitable by-product in the process of gasification,which is one of the important problems that limit the development of biomass pyrolysis and gasification technology by blocked the pipeline by its condensation at low temperature,reduce the overall energy conversion rate of the gasification system,even caused environmental pollution.At present,the catalytic cracking method is the most effective method for removing tar by utilizing the energy contained in tar to effectively improve the quality of syngas.Hence,the char-based monometallic and bimetallic catalyst with high catalytic performance was synthesized from typical agricultural biomass Peanut Shells and seaweed biomass Sargassum,and applied to the catalytic cracking of biomass tar in the paper.A carbon-silicon composite catalyst structure with a silicon-based protective film is constructed,which effectively improves the stability of the catalyst and provides a certain reference for the catalytic conversion of biomass tar.（1）Using peanut shells as raw materials and introducing K₂Fe O₄ as activator and metal-excipients to analyze the catalytic properties of iron-potassium bimetallic nanoparticles research.The results showed that K₂Fe O₄ was hydrolyzed and recrystallized in a nitrogen atmosphere to form KFe O₂ nanoparticles,which were embedded on the surface of the char support to form active sites.A large number of agglomerated KFe O₂ nanoparticles occupy the pore structure of the carrier,which causes a certain degree of pore plugging,but its excellent catalytic activity can effectively compensate for the defects.KFe O₂ exhibits high catalytic activity for the catalytic cracking of tar and can inhibit the formation of carbon deposits.When the pyrolysis temperature is 600°C and the reforming temperature is 800°C,the tar conversion rate reaches 94.9%and the gas yield reaches 608.1m L/g,and the tar conversion rate remained stable in the five-cycle experiment,indicating that the catalyst has better stability at high temperatures.（2）Using sargassum as raw material,introducing Fe Cl₃ and Ni Cl₂ two components to prepare a catalyst with iron and nickel bimetallic nanoparticles,and research the enhanced characteristics of the catalyst for catalytic cracking of tar.The results showed that Ni Cl₂ was hydrolyzed and reduced by heat to form Ni⁰nanoparticles,and strongly interacted with Fe to form Fe Ni₃ alloy nanoparticles.Fe Ni₃ exhibits a good low-temperature catalytic activity,combined with the oxygen affinity of Fe,the Fe²⁺O/Fe oxygen cycle is formed at the metal active site to inhibit the formation of carbon deposits.When the reforming temperature is 600°C,the tar conversion rate reaches 90.07%,and the gas yield reaches 443.3m L/g,which has good low-temperature catalytic activity.In the five-cycle experiment,the tar conversion rate showed a certain gradient decrease,but the tar conversion rate could still be maintained at about 80%,indicating its good stability at low temperatures.（3）Using Sargassum as raw material and Fe and Ni as active sites,a silicon-based protective film was introduced to prepare a carbon-silicon composite catalyst.The stability of the catalyst to the low-temperature catalytic cracking activator of tar was comparatively studied.The results show that the introduction of a silicon-based protective film can form a Ni-O-Si bond with the active site Ni0.On the one hand,it limits the growth of metal nanoparticles,on the other hand,it enhances the mechanical strength of the semi-coke support,which plays an important role in the tar cracking experiment.Function;Besides,the formation of the silicon-based protective film can protect the active sites from carbon deposits and ensure the stable catalytic activity of the carbon-silicon composite catalyst in the cycling experiment.At a reforming temperature of 600°C,the tar conversion rate reached 92.4%,and the gas yield reached 474.1m L/g,which was maintained well in five-cycle experiments,confirming that the catalyst has strong catalytic activity and excellent stability.