Preparation Of Biomass Porous Carbon Supported Platinum Catalysts And Their Catalytic Oxidation Of VOCs

With the development of industry,population growth and mass burning of biomass resources,the pollution of atmospheric volatile organic compounds has become an urgent environmental problem to be solved.Thermal catalytic oxidation technology has been proved to be an efficient strategy for completely degrading volatile organic compounds.In this work,supported catalysts with noble metal Pt as active component,nitrogen doped biomass porous carbon and oxygen-enriched activated carbon as supports were prepared by surface modification of biomass porous carbon.The activity and stability of catalytic oxidation of benzene were systematically studied.Firstly,five kinds of biomass were utilized as carbon precursors,including soybean straw,sorghum straw,pine,bamboo and sunflower pollen.After mixing with different nitrogen sources,N-doped biomass porous carbon was prepared by one-step pyrolysis,and then Pt/N-doped biomass porous carbon catalyst(Pt/Y-BiomassNxC)was prepared by impregnation reduction method.The mechanism of nitrogen doping in onestep pyrolysis with different nitrogen sources was explored,furthermore the effects of different nitrogen doping amount on the morphology,structure and surface properties of porous carbon and its catalysts were investigated,as well as the catalytic activity and anti-interference of the catalysts.The results indicated that the nitrogen doping amount of organic source was higher than that of inorganic nitrogen source.Although the morphology and crystal structure were not changed,and the specific surface area and pore structure were similar,the organic nitrogen source doping could obtain more Pyridine-N content and more surface defects,which were conducive to the deposition and dispersion of platinum,as well as the adsorption of benzene.After Pt loaded on melamine doped soybean straw porous carbon,higher Pt0/Pt2+and lattice oxygen increased the activity of the catalyst(T90 was 170℃).The catalyst kept the conversion of benzene unchanged during the 90 hours stability evaluation,and showed good antiinterference performance of water vapor and carbon dioxide.Secondly,due to the small specific surface area and the microporous structure of porous carbon prepared by one-step pyrolysis,the Pt/Y-BiomassNxC catalyst limited the mass transfer rate of the reaction and was greatly affected by water vapor to some extent.Therefore,five kinds of biomass were used as carbon precursors to prepare oxygen-enriched biomass activated carbon by three-stage method without chemical reagent addition,including hydrothermal pretreatment,high temperature carbonization in inert atmosphere and low.temperature oxidation in air atmosphere.The results showed that hydrothermal pretreatment could improve the yield of coke,increase the activation temperature and time,and then improve the specific surface area of activated carbon.Air activation steps not only increased mesoporous structure of activated carbon,but also introduced oxygen-enriched groups to the surface of activated carbon,which improved surface activity and surface defect degree,resulting in smaller Pt particle size.The Pt/SO-HCO catalyst exhibited the highest benzene catalytic activity(T90=160℃),and its stability and anti-interference were greatly improved compared with the Pt/YBiomassNxC catalyst.Finally,the model of Pt/SO-HCO catalyst was established and optimized by density functional theory(DFT)calculation.The difference charge,benzene adsorption energy,density of states and d-band center of Pt were calculated,which indicated the interaction between Pt and oxygen-enriched activated carbon support and the reason of high catalytic activity.The four-step reaction mechanism of benzene on Pt/SO-HCO catalyst was proposed through in-situ infrared experiment.