摘要
The transesterification reaction of soybean oil with methanol over kalsilite-based heterogeneous catalysts was investigated. The kalsilite was synthesized from potassium silicate, potassium hydroxide, and aluminum nitrate aqueous solutions by controlling the pH value at 13. After calcination in air at 1200°C, a very porous kalsilite (KAlSiO ) was obtained with surface pores ranging from 0.2 to 1.0 μm. However, this kalsilite had relatively low catalytic activity for the transesterification reaction. A biodiesel yield of 54.4% and a kinematic viscosity of 7.06 cSt were obtained at a high reaction temperature of 180°C in a batch reactor. The catalytic activity of kalsilite was significantly enhanced by introducing a small amount of lithium nitrate in the impregnation method. A biodiesel yield of 100% and a kinematic viscosity of 3.84 cSt were achieved at a temperature of only 120°C over this lithium modified catalyst (2.3 wt-% Li). The test of this lithium modified catalyst in pellet form in a laboratory-scale fixed-bed reactor showed that it maintained a stable catalytic performance with a biodiesel yield of 100% over the first 90 min.
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