Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various technique...Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.展开更多
Recently,there is a growing interest in the use of microalga in various fields.Microalgae have properties such as rapid reproduction and high biomass accumulation,and under certain conditions,some are able to accumula...Recently,there is a growing interest in the use of microalga in various fields.Microalgae have properties such as rapid reproduction and high biomass accumulation,and under certain conditions,some are able to accumulate a large amount of oil.However,microalgae oil often contains more free fatty acids than the vegetable oil and is therefore unsuitable for biodiesel synthesis using alkaline catalysts.For this reason,some authors suggest the application of heterogeneous catalysis.A particular interest in the use of immobilized enzymes has developed.Other solid substances can also be used as heterogeneous catalysts are usually metal oxides,carbonates or zeolites.The use of these catalysts results in simpler biodiesel synthesis,especially purification processes,a cleaner end product and a less polluted environment.The molar ratio of alcohol to oil is lower during enzymatic transesterification,and more than 90%ester yield is obtained using a molar ratio of alcohol to oil of 3:1 to 4.5:1.The alcohols do not have a negative effect on the effectiveness of chemical catalysts,so it is possible to use alcohols in molar ratio from 4:1 to 12:1.The optimal temperature of enzymatic process is 30℃–50℃.An ester yield of more than 95%was obtained in 12–48 h.Using chemical catalysts,greater than a 95%yield of esters was obtained at higher temperatures in a shorter time.Material costs of enzymatic catalysis can be reduced by reusing the catalysts directly or after regeneration.展开更多
基金supported by the Institute of Chemical Materials Foundation of CAEP(No.626010937)
文摘Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.
文摘Recently,there is a growing interest in the use of microalga in various fields.Microalgae have properties such as rapid reproduction and high biomass accumulation,and under certain conditions,some are able to accumulate a large amount of oil.However,microalgae oil often contains more free fatty acids than the vegetable oil and is therefore unsuitable for biodiesel synthesis using alkaline catalysts.For this reason,some authors suggest the application of heterogeneous catalysis.A particular interest in the use of immobilized enzymes has developed.Other solid substances can also be used as heterogeneous catalysts are usually metal oxides,carbonates or zeolites.The use of these catalysts results in simpler biodiesel synthesis,especially purification processes,a cleaner end product and a less polluted environment.The molar ratio of alcohol to oil is lower during enzymatic transesterification,and more than 90%ester yield is obtained using a molar ratio of alcohol to oil of 3:1 to 4.5:1.The alcohols do not have a negative effect on the effectiveness of chemical catalysts,so it is possible to use alcohols in molar ratio from 4:1 to 12:1.The optimal temperature of enzymatic process is 30℃–50℃.An ester yield of more than 95%was obtained in 12–48 h.Using chemical catalysts,greater than a 95%yield of esters was obtained at higher temperatures in a shorter time.Material costs of enzymatic catalysis can be reduced by reusing the catalysts directly or after regeneration.
