Catalytic Performance Of Dolomite-palygorskite Claysupport Ni And Fe For The Catalytic Cracking Of Toluene As A Model Compound Of Tar

Thepresence of biomass tarduring the biomass gasification process is the major obstaclefor the large-scale application of biomass gasification technology.Among various tar removal methods,catalytic conversion is an ideal choice.Therefore,the main objectives of this paper are to investigate the ability ofdolomite-palygorskite clay?DPC?as a catalytic material,and toluene was chosen as a model compound of biomass to study the catalytic cracking performance ofcalcinated dolomite-palygorskite clay?CDPC?.Then,the effects of the reaction temperatures,gas hourly space velocity?GHSV?,Fe and Ni loadings,reduction time and the lifetime test were investigated in this paper.The catalysts before and after catalytic reaction were characterized byXRD,BET,TEM,MS,XPS to clarify the mechanism of toluene conversion.The detailed research contents are as follows:?1?The catalytic activity and stabilityof CDPC was better thandolomite?DO?due to its larger specific surface areaand the retained shape of palygorskite.Besides,the toluene conversion of CDPC improved with the increasing reaction temperature and the decrease of GHSV.When the reaction temperature was 800 ^oC and the GHSV was 3374h^-1,the CDPC catalyst showed the best catalytic activity and the toluene conversion is99.5%.And then,the activation energy and the pre-exponential factor of CDPC were calculated by the first-order kinetic model.?2?After the loading of iron and nickel,the catalytic activity of the catalysts significantly improveddue to the formation of the active component Fe-Ni alloy and the increase of the thermochemical activity of dolomite in the DPC.In the other hand,the catalytic activity of Fe_xNi_10-x/DPC improved with the increase of loadingiron and nickel,and the 8Fe2Ni/DPC showed the best catalytic activity when toluene inlet was 3000ppm.?3?TheCO₂ reforming performance of Fe_xNi_10-x/DPC catalysts werestudied.The results showed that the addition of CO₂ could improve the toluene conversion and effectively suppress the coke formation.The catalytic activity of Fe_xNi_10-x/DPC catalyst remained stable within two hours when the CO₂/C₇H₈ ratio was 1 and the toluene inlet was 5000 ppm.Furthermore,the increase of thereduction time could improve catalytic activity and stability of catalysts.?4?The existence of carbon on the surface of the catalyst after the reaction was analyzed.As was shown in the results of XPS,the carbon on the reacted catalysts includes the metal carbides,C-OH,C-O and adsorption of CO₂.The intensity of the metal carbide binding energy peak increased with the raise of catalytic activity and reaction time.Therefore,the formation of metal carbide species is considered to be the main reason of deactivation for CDPC and Fe_xNi_10-x/DPC catalysts.