Glycerol Oligomerization Using Low Cost Dolomite Catalyst.

Abstract

Production of glycerol oligomers by heterogeneous catalysis is being studied as an option for valorization of this biodiesel by-product. In this study, the catalytic activity of dolomite and the effects of parameters such as catalyst loading, reaction temperature, and reaction time were evaluated. Reusability and stability test were also performed. The material was tested as-received and after a thermal treatment, being characterized by XRD, FTIR, N2 adsorption–desorption, SEM, CO2-TPD and TG/DTG. Reaction products were analyzed by GC-FID for oligomers composition and ICP to verify metallic species leaching. The thermal treatment led to a decrease of the particle size, increase of the specific surface area and improved basicity. Calcined dolomite showed better catalytic performance than natural dolomite, leading to almost 80% glycerol conversion and selectivities for diglycerol and triglycerol of 51% and 3%, respectively. Kinetic test revealed that the reaction is slow along the first hours and later the reaction rate increases. Ca and Mg are leached to the reaction medium but the catalyst could be reused up to 2 cycles, with similar diglycerol yield. The reaction conditions for this material are less severe than those reported previously, which added to the low cost and reusability capacity turns suitable for glycerol oligomerization process.