Glycerol oligomers production by etherification using calcined eggshell as catalyst

The growing expansion of biodiesel industries led to an increasing formation of by-products as glycerol, which can be considered as building block molecule to high-added value products. The use of natural materials, formed by calcium carbonate, has recently become an interesting approach to the development of inexpensive and widely available basic catalysts. In this work, the use of eggshell waste as catalytic precursor was evaluated in the glycerol etherification reaction to obtain glycerol oligomers. Both raw and calcined eggshell were characterized by XRD, FTIR, N-2 adsorption-desorption at -196 degrees C, particle size analysis, SEM, CO2-TPD and TG/DTG. For comparative purposes, commercial CaO was also tested. The solids were tested as-received and calcined in the reaction. Several parameters as catalyst loading, reaction temperature, reaction time and the leaching of calcium to the reaction medium were evaluated. The optimal reaction conditions for the calcined eggshell were catalyst loading of 2 wt.%, temperature of 220 degrees C and reaction time of 24 h, promoting 85% glycerol conversion and oligomers yielding of 43% (Di-and Triglycerol). The material tested shows leaching; however, taking account its low cost and good basic properties, calcined eggshell can be considered as promising catalyst for glycerol oligomerization. (C) 2017 Elsevier B.V. All rights reserved.