Valorization of glycerol as a key in the environment of biorefineries

COMELLI, R

Verona

Simposio; XIX ISAF (International Symposium on Alcohol Fuels); 2011

C.R.E.A.R.

Glycerol, the co-product obtained in the biodiesel process, can play an important role as one key-compound in the environment of future biorefineries. Reactions of dehydration-hydrogenolysis, selective oxidation, etherification, and steam reforming of glycerol were studied in order to valorize it and to obtain acetol-propanediols, dihydroxyacetone, ethers of glycerol, and hydrogen, respectively. By considering the dehydration-hydrogenolysis reactions in liquid phase using a commercial copper chromite, the 1,2-propanediol (1,2-PD) yield was improved conducing the reaction in two steps, the first one in mild conditions and without hydrogen, and the second one with hydrogen pressure. Both prepared Pt/W/Zr(OH)4 and Pt/W/ZrO2 allowed to obtain 1,3-PD, depending the 1,2- to 1,3-PD ratio on the preparation technique of these catalysts. Ni impregnated on zeolite 13X was evaluated during hydrogenolysis in liquid and gas phases. Operating conditions in liquid phase were 200-230°C, 18 atm, feeding either pure glycerol or 50% solution, and using 1-4 g catalyst; conversion increased and selectivities to interesting products changed by increasing temperature or the ratio of catalyst mass/glycerol volume. Gas phase conditions were 200°C, 20% glycerol solution, and 200 mg catalyst; Ni/13X was very active (79.9% conversion) but with low selective to acetol and 1,2-PD, favoring the selectivity to 1,2-PD using two successive beds, the upper one of copper chromite and another of Ni/13X, reaching 27.2 and 39.6% selectivity to acetol and 1,2-PD, respectively. Dihydroxyacetone was produced by selective oxidation of glycerol on Pt impregnated on potassium ferrierite, being it an original result because of Pt/C is not selective towards that product needing a second metal to obtain DHA. The etherification reaction of glycerol with butenes was studied using the "wet" Amberlyst 35 sulfonic ion exchange resin; pretreatments cleaning with methanol and activation with an acid solution favored activity. The steam reforming of glycerol to produce hydrogen took place on Ni impregnated on alumina catalysts; the catalytic behavior depended on the operating conditions, increasing conversion with temperature after 4 h and the same WHSV; the largest hydrogen selectivity was obtained at 650ºC. Deactivating during reforming took place but regeneration was possible selecting the adequate conditions.