Green acid catalyst obtained from industrial wastes for glycerol etherification

In this work several carbonaceous wastes (glycerin (G), waste coffee grounds (WC) and polyethylene terephthalate (PET)) were successfully used as precursors to obtain carbon-based catalysts to transform crude glycerol (from biodiesel production) into value added compounds through glycerol etherification. The X-ray diffraction data showed that the produced carbons are amorphous materials. MEV/EDS analyses showed much dispersed surface groups with an increased amount of sulfur (3.5 to 8.2%). Very promising results were obtained for glycerol etherification, reaching about 80% conversion and a high selectivity for the MTBG species (3-tert-butoxy-1,2-propanediol). The catalysts obtained from PET and WC wastes lead to the highest glycerol conversion and selectivity for MTBG, probably due to the higher acidity. These successful results suggest that these catalysts can be applied for glycerol waste conversion in order to obtain value added compounds.