It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC （fluid catalytic cracking）. The effects of temperature and C/O ratio （catalyst to o...It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC （fluid catalytic cracking）. The effects of temperature and C/O ratio （catalyst to oil weight ratio） on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil （VGO） was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas （LPG）, repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC （hydrogen transfer coefficient） and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/A1203 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.展开更多
The adsorption performance of toluene on ultra-stable Y zeolite (USY) was studied via dynamic adsorption. The eff ects of bed temperature, initial concentration, and feed fl ow rate on adsorption were investigated. Th...The adsorption performance of toluene on ultra-stable Y zeolite (USY) was studied via dynamic adsorption. The eff ects of bed temperature, initial concentration, and feed fl ow rate on adsorption were investigated. The Yoon-Nelson model was used to fi t the toluene breakthrough curves. The length of mass transfer zone was calculated based on breakthrough curves. The Langmuir-Freundlich model fi t the adsorption isotherms of toluene on USY, which indicated that the surface of USY was heterogeneous. The adsorption isosteric heat calculated from adsorption isotherms ranged from 54.3 to 69.8 kJ/mol, indicating physical adsorption. The combined technique of temperature swing adsorption with vacuum swing adsorption (TVSA) exhibited excellent desorption performance, which was attributed to the low desorption activation energy. Under optimized TVSA conditions, the desorption rate of toluene reached 90.6% within 10 min. The long-term cyclic utilization results indicated that the adsorption capacity of USY was stable.展开更多
文摘It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC （fluid catalytic cracking）. The effects of temperature and C/O ratio （catalyst to oil weight ratio） on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil （VGO） was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas （LPG）, repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC （hydrogen transfer coefficient） and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/A1203 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.
文摘The adsorption performance of toluene on ultra-stable Y zeolite (USY) was studied via dynamic adsorption. The eff ects of bed temperature, initial concentration, and feed fl ow rate on adsorption were investigated. The Yoon-Nelson model was used to fi t the toluene breakthrough curves. The length of mass transfer zone was calculated based on breakthrough curves. The Langmuir-Freundlich model fi t the adsorption isotherms of toluene on USY, which indicated that the surface of USY was heterogeneous. The adsorption isosteric heat calculated from adsorption isotherms ranged from 54.3 to 69.8 kJ/mol, indicating physical adsorption. The combined technique of temperature swing adsorption with vacuum swing adsorption (TVSA) exhibited excellent desorption performance, which was attributed to the low desorption activation energy. Under optimized TVSA conditions, the desorption rate of toluene reached 90.6% within 10 min. The long-term cyclic utilization results indicated that the adsorption capacity of USY was stable.
