Pyrolysis of Vegetable Oil Soapstock in Fluidized Bed: Characteristics of Thermal Decomposition and Analysis of Pyrolysis Products

This study investigated the effect of temperature on pyrolysis of soapstock in a fluidized bed reactor, and the characterization of soapstock chars (SCs) and pyrolysis oils (POs) were analyzed. TGA (Thermogravimetric-analysis), TG-FTIR (Fourier-transform-infrared-spectrometry), TG-MS (Mass-spectrometry) were employed to investigate characteristics of SS pyrolysis. Experimental results indicated that the yield of SC decreased with increasing temperature. PO yield reached the maximum of 21.05 wt% at 600 °C and the yield of non-condensable gas varied with temperatures. The content of carbon, hydrogen and nitrogen distributed in the SC decreased with the increasing temperature, and sulfur tended to be retained in SC during pyrolysis with the distribution ratio of 0.55-0.62. Ketones, alcohols and hydrocarbons were the dominate substances in PO, and higher temperature promoted the production of short-chain alkanes and the conversion of alkenes to benzene derivatives. SS pyrolysis can be divided into three stages. Decomposition and transformation of organics mainly occurred at stage II and Ca2+ played a catalytic role for decarboxylation at stage III. Decarboxylation was the main deoxygenation pathway. This study provided a theoretical basis for the application of soapstock thermochemical treatment. It is of great significance for the quality improvement of PO and pollution control for pyrolysis processes.