The catalytic performance of carbide slag in transesterification is investigated and the reaction kinetic parameters are calculated. After being activated at 650℃, calcium compounds of carbonate and hydroxide in the carbide slag are mainly transformed into calcium oxide. The activated carbide slag utilized as the transesterification catalyst is characterized by X-ray diffraction （XRD）, attenuated total reflectance-Fourier transform infrared spectroscopy （ATR-FTIR）, nitrogen adsorption-desorption and the Hammett indicator method. Compared with the carbide slag activated at 700 and 800℃, the largest surface area of 22.63 m2g^-1, the smallest particle size of 265.12 nm and the highest catalytic efficiency of the carbide slag activated at 650℃ guarantee its capacity in catalyzing transesterification. Then, the influences of activated temperature （Ta）, molar ratio of methanol to oil （γ）, catalyst added amount （ζ）, reaction temperature （Tr） and reaction time （τ） on the catalytic performance are investi- gated. Under the optimal transesterification condition of Ta=650℃, γ=15, ζ=3%, Tr=60℃ and τ=-110 rain, the catalytic efficiency of 92.98% can be achieved. Finally, the kinetic parameters of transesterification catalyzed by the activated carbide slag are calculated, where activation energy （E） is 68.45 kJ mol^-1 and pre-exponential factor （k0） is 1.75×10^9 min^-1. The activated carbide slag shows better reused property than calcium hydroxide.
LIU Meng QiNIU Sheng LiLU Chun MeiLI HuiHUO Meng Jia
Lime mud （LM）, a solid waste from the paper mill, is used as an economic and environmental friendly heterogeneous basic catalyst for transesterification, which is accompanied by characterization of X-ray fluorescence, thermogravimetric-differential thermal analysis, X-ray diffraction, N2 adsorption, and Hammett indicator method. To investigate the performance of the achieved catalyst, which is activated through calcination, the aspects of calcination temperature, reaction time, mole ratio of methanol to oil, catalyst addition percentage, and reaction temperature are concerned. Characterization of catalyst reveals that LM could be activated through calcination to transform the carbonate and hydrate of calcium into the oxide forms and higher calcination temperature could lead to stronger basic strength. However, N2 adsorption results indicate that higher temperature causes the sintering of the catalyst and shrinkage of the catalyst grains. When LM is activated at 800℃ （LM-800） and the reac- tion is carried out at 64℃ with a methanol to oiL mole ratio of 15：1, catalyst addition percentage of 6%, and reaction time of 2 h, the maximum transesterification conversion of 94.35% could be achieved. Reusability of LM-800 is also investigated com- pared with laboratory grade CaO in five reaction cycles and the results indicate that the catalysts derived from LM can be used as an economic and efficient catalyst for biodiesel production.
