The Study On The Crab Shell Biodiesel Catalyst And Its Catalyst Performance

Biodiesel is regarded as a green biomass energy of renewable and low carbon. The catalysts using in the production has importance for production costs and quality of biodiesel. Searching for a cheap, environmentally friendly biodiesel catalysts is the key to the study of biodiesel.Waste crab shells from the food industry were used for preparing a solid biodiesel catalyst, according to characteristics of the structure and composition of crab shell, we had devised a strategy to prepare a crab shell catalyst. The catalytic performance of the crab shell catalyst was evaluated by the transesterification of rapeseed oil with methanol.The advantages of heterogeneous solid base catalysts were simple separation of the reaction system, mild reaction conditions, renewable capability, little corrosion and ecologically friendly. Nowadays, heterogeneous biodiesel catalyst which is a key factor to reduce production cost of biodiesel has been one of the major branches in researching of biodiesel catalysts.Crab shell was first incompletely carbonized, KF was then loaded onto the resultant and the material was finally activated at a desired temperature to prepare a high-performance solid base catalyst. The catalytic activity of the catalyst was evaluated using the transesterification reaction of rapeseed oil with methanol. The effects of carbonization temperature, concentration of KF solution and activation temperature on the activity of the catalyst were investigated and the mechanism of catalytic activity was discussed.The optimized preparation conditions are as follows:carbonization temperature 500℃, KF impregnation amount 30 wt.%, activation temperature 200℃.The results indicated that the transesterification rate of rapeseed oil to biodiesel reached 92.4% using the crab shell catalyst when the reaction was carried out at 65℃with a catalyst amount 3.5 wt.%(based on rapeseed oil mass), a methanol/rapeseed oil mole ratio 9:1, and a reaction time of 3h.Crab shell catalyst was characterized by thermogravimetric analysis (TGA), scanning electron microscope (SEM), X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), Element Analyzer (EA), BET, and Fourier transform infrared spectrometer (FT-IR).The results of EA, FT-IR, BET indicated that crab shell catalyst contained organic and inorganic materials, and its had a large specific surface area form a porous framework structure. With explored by incomplete carbonized crab shell, KF, CaCO3 and chitosan, the result indicated the activation process facilitated the reaction between KF and the incomplete carbonized crab shell to form active sites of catalysis on the surface of the crab shell. The results of SEM, XRD, EDS showed active sites of catalysis maybe-CH2OK and the solid base (reaction between KF and CaCO3). The results of TGA-DTG showed the crab shell catalyst had an excellent thermal stability.The activity of the catalyst for the transesterification reaction would come from the high surface area of the catalyst and the ultrahigh active sites formed by the reaction of KF with incomplete carbonized crab shell. The crab shell catalyst, which comes from renewable biomass and can be biodegraded easily, has the distinct characteristics of a green catalyst and could transform production of biodiesel fuel into a faster, less expensive, and more environmentally friendly process.Compared with other solid base catalysts, crab shell catalyst had a relatively high catalytic activity, relatively low cost, excellent thermal stability and chemical stability. The crab catalyst does not produce saponification and emulsification in the process of catalytic reaction. Therefore, the production of biodiesel from rapeseed oil using this catalyst is a promising "green" process.