PRODUCTION OF OXYFUEL ADDITIVES BY GLYCEROL ETHERIFICATION OVER BEA-ZEOLITE CATALYSTS

The chemical valorization of glycerol into high added-value products has been recently regarded as an efficient route for the production of oxygenated additives. On this account, this work has been focused on the etherification reaction of glycerol with bio-butanol over home-made BEA samples, in order to define the suitable experimental conditions controlling the formation of poly-substituted ethers (i.e., di- and tri-butyl glycerol ethers), with huge potential as bioadditives suitable to meet the EU policy requirements for entering either in fossil diesel or biodiesel formulations. Although at a higher temperature than a benchmark Amberlyst-15 acid resin, BEA zeolites resulted to be very active and selective in the production of butyl glycerol ethers, thanks to their specific textural and surface properties determining a suitable availability of acidic sites1. A good compromise between high reaction rate and minimization of by-products was obtained by operating for 6 hours at 180°C, achieving a maximum glycerol conversion of 75%, with a butanol/glycerol molar ratio of 4 and a catalyst amount of 30 wt.% in respect of glycerol. Catalytic and technological benefits have been obtained by using a stirred batch reactor coupled with a membrane separation system in vapor permeation (PV) configuration by removing in continuum the water formed as byproduct2. This technological solution allowed making the clean-up or regeneration steps easier and to independently optimize both the selective and the catalytic properties. Morover, the comprehensive GC-MS analysis of the reaction mixtures allowed a full identification of the main compounds formed, also disclosing the main reaction pathways behind their formation. The feasibility of this novel catalytic route able to extend the biodiesel chain has been finally demonstrated by the zeolite stability and reusability, evidencing how the catalyst activity can be completely restored after a very simple regeneration step, capable to return the same glycerol conversion even after 4 catalytic cycles.