Thermal Decomposition Behavior of Crude Glycerin

Abstract

The evolution of biodiesel generated an important increase in the supply of glycerin for industrial applications. A situation like this impels to develop additional rational and effective ways to use the glycerol byproducts of biodiesel. One of the most attractive ways is its use for energy needs. The present paper investigates the thermal decomposition of crude glycerin co-products of bovine tallow biodiesel by thermogravimetry (TGA/DTA). The main gaseous products are discussed and evaluated, and the mechanism of thermal decompositions was studied. The process revealed that the decomposition of crude glycerol is carried out in at least three distinct phases. The mechanism of decomposition of each phase is strongly associated with one or more components in the mixture. The occurrence of the first stage of decomposition and the observed behavior it is due to the presence of methanol and water mainly. The changes observed in the other stages are due to reactions of other components such as catalyzed glycerol decomposition, fatty acid methyl esters cracking and some residual salts transformations. The results and observed behavior were compared with glycerol thermal decomposition at the same conditions. The observed differences in some properties, mainly the activation energy reveals the role of some components in the kinetics of the decomposition process. Finally, was found that the thermogravimetry is an important and effective method to evaluate the partial feasibility and some combustion characteristics of potential fuels as crude glycerin.