Study On The Solid Base Catalyst Used In Preparing Biodiesel

Biodiesel fuel was monoalkyl esters of long chain fatty acids derived from a renewable lipid feedstock, such as vegetable oil or animal fat. Lipid and methanol or another lower alcohol were performed transesterification reactive formation biodiesel by the catalysis of acid, alkali or enzymatic. Compared with traditional homogeneous acid/base catalyst, using heterogeneous base catalyst can obtain pure product and avoid the problem of catalyst separate or waste water pollute circumstance. Researches on the heterogeneous catalyst, catalytic transesterification reaction and the properties of production are meaningful for the improvement of biodiesel production and its application.CaO was a ultra-intense solid alkali and have the excellence of higher activation or longer life. But using pure CaO as catalyst have the problem of from suspensoid or catalyst separate. The prevenient literature was short of the study of using different former body preparation series of supported CaO solid base catalysts. In this work, a series of supported CaO solid base catalysts were prepared. An investigation was made on the effects of the supporter, raw materials and preparing method on the catalytic activities, and it was found that an impregnation using Ca(AC)₂ solution and CaCO₃ as the impregnation medium andγ-Al₂O₃ as supporters were a good method to prepare the base catalysts. Optimal preparation condition were in 25% Ca(AC)₂ solution, drying at 90℃for 12h and calcining at 800℃. Using CaCl₂ and Na₂CO₃ reactive production ontoγ-Al₂O₃ supporter, drying at 90℃for 12h and calcining at 900℃. The catalyst active component can not be leached by methanol.The catalysts were characterized by X-ray diffraction, The sesults show that CaO was well dispersed onto the catalyst support surface. With the amount increase of CaO, catalytic actibity has gradually strengthen. The results also show that calcining on the lower temperature , some former body not complete decomposition.The influences of reaction conditions were studied and the optimized parameters were: Using Ca(AC)₂ as former body, reaction temperature 65℃, amount of catalyst 3%, molar ratio of methanol to oil 18:1, and reaction time of 8h, overall yield of the alkaline reaction 96%. Using CaCO₃ as former body, reaction temperature 65℃, amount of catalyst 5%, molar ratio of methanol to oil 18:1, and reaction time of 8h, overall yield of the alkaline reaction 88%. Because it was a mass transfer reaction, at the initial segment time, triglyceride have a lower conversion.4-6h later, the conversion increased gradually. After reaction 8h, the conversion reaches balanced state.