Novel solid base catalyst for biodiesel production by surface modification CaO with ethyl bromide

To decrease the environmentally toxic wastewater caused by the homogeneous basic system of biodiesel production, a stable CaO was developed by modifying commercial CaO with ethyl bromide. Fourier transform infrared spectroscopies indicate that the modifier bonded onto the surface of CaO chemically. Almost no other water was adsorbed on the modified CaO surface, even with exposure in saturated water vapor atmosphere for 50 h, as suggested by the results of a humidity test, while a 98 % moisture absorption degree was detected over commercial CaO. The high catalytic activity of modified CaO in a 4 % water-content reaction system contributes to the hydrophobic layer formed by ethyl groups of modifier, which have the capacity of preventing the absorption of water to the CaO surface. Both the optimization of reaction condition and the water resistance of modified CaO were investigated in this work.