| In the wake of the consumption of fossil fuel and the aggravation of the environmental concerns,it is currently an urgent to search for renewable and cleaning energy source.Due to the merit of biodegradability,non-sulfur,renewability,and high lubricity,biodiesel is considered to be one of promising alternative fuels.In the process of producing biodiesel,cheaper oils（e.g.,Jatropha oil）have been elected as raw materials to cut the production cost.In addition,abundant free fatty acids（FFAs）can be generated as important byproducts during food processing.It is also an important way to produce biodiesel by esterification of FFAs and with short-chain alcohols.In addition,the activity of the catalyst with couple acid sites is higher in transterification or esterification.It is possibly due to the synergistic effect of Lewis acid sites and Br?nsted acid sites.Accordingly,three kinds of solid acid catalyst were prepared and used to produce biodiesel.The main results were as follows:（1）The metal fluorides（MgF2,ZnF2 and AlF3）were prepared through a sol-gel method.Their catalytic activity was studied by esterification of oleic acid with methanol,and physical-chemical properties were characterized by XRD,NH3-TPD,TGA,etc.ZnF2 was found to exhibit the best catalytic performance with the oleic acid conversion of 92% under the optimum esterification reaction conditions（methanol/oleic acid molar ratio of 10:1,8 wt% catalyst dosage at 140 °C for 6 h）.And it still keeps high catalytic activity after four consecutive cycles.（2）The TPA-metal fluorides were prepared through impregnation and solvothermal method respectively.The catalysts were characterised by FT-IR,XRD,EDS,NH3-TPD,etc.The catalytic activity was explored by esterification of oleic acid with methanol.Among those acidic catalysts,the Mg20F39TPA-1.0 hybrid presented pronounced catalytic performance in the esterification of oleic acid.It could be due to the higher acidity and better dispersion of active sites.Under the optimum reaction conditions（9/1 methanol/oleic acid molar ratio,5 wt% catalyst,80 °C and 4 h）,the oleic acid conversion of 92% was obtained.Mg20F39TPA-1.0 still keeps high catalytic activity after five consecutive cycles.More importantly,its structure was almost consistent with the fresh ones by characterization.The kinetics study of the esterification was conducted,and the low activation energy（43.9 kJ/mol）was obtained.It could be partially elucidated that Mg20F39TPA-1.0 was benifical for the esterification reaction.The response surface methodology（RSM）was utilized to explore the effects of different experimental variables（e.g.catalyst amount,methanol to oleic acid molar ratio and reaction time）on the esterification reaction.Then,Mg20F39TPA-1.0 was used for the transesterification of Jatropha curcas oil（AV = 19.35 mg KOH/g）with methanol.The biodiesel yield reached 93% under the reaction conditions: catalyst amount of 8 wt%,methanol/oil mass ratio of 30:1 at 140 °C for 12 h.（3）The porous metal fluorides was synthesized using Pluronic P123（EO20PO70EO20）as a structure directing agent.The catalyst was characterised by XRD,NH3-TPD,etc.The catalytic activity was explored through esterification of oleic acid with methanol.Among those acidic catalysts,T6ZnF2 exhibited pronounced catalytic performance in esterification of oleic acid.The reaction conditions were established as follows: methanol/oleic acid molar ratio of 9,amount of catalyst of 5 wt%,reaction time of 5h at 120 °C and got oleic acid conversion of 96%.Next,T6ZnF2 was used for the transesterification of Jatropha curcas oil（AV = 15.47 mg KOH/g）with methanol.The biodiesel yield reached 95% under the reaction conditions: catalyst amount of 10 wt%,methanol/oil mass ratio of 30:1 at 100 °C for 10 h.The T6ZnF2 was reused four times without noticeable drop in activity.It was demonstrated that T6ZnF2 was recyclable.Moreover,a kinetic study performed under optimal reaction conditions revealed a low active energy of 50.05 kJ/mol. |
