| The sustainable development of national economy is now facing the dual pressures of energy and environment and so to develop and utilize the renewable energy to substitute the fossil fuels is the focus of scientific research.In this research,regarding the extensive source of biomass straw as raw material,a series of problems in bio-oil preparation are studied,in which Fe,Co and Cu support modified HZSM-5 for online catalytic upgrading.The impregnation method is used to prepare the modified catalysts and the effects of modified catalysts on surface physical parameters are researched via the modern characterization.Biomass vacuum pyrolysis catalytic upgrading experiments are carried out through two stage fixed bed reactors and the physiochemical properties and chemical components of bio-oil before and after the upgrading are contrasted.The thermo gravimetric analyzer is applied to characterize the coke on the surface of the deactivated catalysts and the effects of modification on anti-coking of catalysts are contrasted and analyzed.The specific research works are as follows:?1?The HZSM-5 is modified by Fe,Co and Cu through impregnation method,the modified HZSM-5 is characterized by XRD,BET and Py-IR and the results show,after modification,the loads on the surface of the catalyst are dispersed uniformly,the particles are not aggregated into large particles and the modified molecular sieve shows good crystallization performance.After modification the acid distribution on the surface has changed.For HZSM-5 modified by Fe,L acid significantly increases and B acid significantly decreases,modified by Co,L acid significantly increases and B acid significantly decreases and by Cu,L acid slightly increases and B acid significantly decreases.After modification,the pore volume is also decreased.?2?The online catalytic upgrading of biomass pyrolysis was experimented in two stage fixed bed reactors,the pyrolysis temperature,system pressure and heating rate significantly affects the bio oil yield,and so the optimal parameters of the previous research results are used to conduct the experiments,in which the final pyrolysis temperature is controlled to 500?,the heating rate is 20? /min and the pressure of system is 5.0kPa,the rape straw vacuum pyrolysis can generate more condensable organic vapor in this condition and also the online catalytic upgrading pyrolysis vapor brings about high rate of organic phase products.The catalytic properties of modified HZSM-5 are analyzed from the aspects of product yield,product composition and oxygen content.The results show that,after catalyzed by Fe/HZSM-5,Co/HZSM-5 and Zn/HZSM-5,the yield,oxygen content,pH value,dynamic viscosity and high heating value?HHV?of the refined bio-oil are 18.3719.03%,15.1317.23%,5.055.12,5.165.22mm2/s and 34.5636.01MJ/kg respectively.There exist many kinds of organic compounds in the refined bio-oil produced,such as aldehydes,ketones,acids,esters,alcohols,phenols and other substances,present as chemical functional groups,the total content of hydrocarbons in refined bio-oil increases remarkably,especially the remarkable increase of polycyclic aromatic hydrocarbons?PAHs?and the performance of aromatization enhances obviously,in which the contents of the monocyclic aromatic hydrocarbons?MAHs?are relatively high after catalytic upgrading by Fe/HZSM-5 and Co/HZSM-5.In the catalytic reaction of HZSM-5,organic oxygen is removed in the form of COX and H2O,while the carbon ions produced in the middle of the process are converted to aromatic hydrocarbons and aldehydes,ketones,acids,esters,alcohols,phenols and other substances are prone to esterification,condensation,polymerization and other reactions.?3?The deactivated catalyst is analyzed by thermo gravimetric analysis,the coke type on the surface of the catalyst is studied and the effects of modification on coking resistance of catalyst are also analyzed and contrasted.The results show that Fe/HZSM-5 and Cu/HZSM-5 has stronger resistance to amorphous coke and Co/HZSM-5 to graphite type coke. |
PDF Full Text Request