Catalisadores Bimetálicos de Óxidos de Mo–Cu (Ni ou Co) Suportado em Alumina para Conversão do Glicerol a Intermediários Químicos

Abstract

The economic viability of biodiesel production depends of the use of glycerol, by-product with multifunctional structure, considered a bio-renewable feedstock of great potential to be transformed to fuel or higher value-added chemicals products. In order to contribute to the development of this research area, study was carried out in order to explore the catalytic potential γ-Al2O3 modified with molybdenum oxide and promoter (Cu, Ni or Co) in the glycerol dehydration reaction to chemical intermediates with industrial application was performed. The strategy was to synthesize Al2O3 spheres by hybrid method with interesting structural, textural and chemical properties for then impregnating with precursors of metals via unconventional method (Pechini). The material composition was chosen with the aim of evaluating the bifunctional effect caused by the combination of acid-base and redox properties of molybdenum catalysts supported on alumina. For comparison was evaluated commercial Ni-Mo/Al2O3 catalyst with high acidity and porosidade. The catalysts were characterized for: ICP-OES, XRF, TGA/DTA, XRD, SEM, IR, H2-TPR, TPD-CO2, N2 adsorption/desorption isotherms, and acidity measurements through pyridine adsorption. The catalytic performance was evaluated in the glycerol dehydration under N2 or H2 flow at atmospheric pressure and 250°C. The modification in the activity and selectivity due to the change of carrier gas are attributed to the changes of acid/redox properties of the catalyst, as suggested by acidity measurements and TPR-H2. Acrolein was the main product observed for all catalysts, but the cupper containing catalyst (CuMoAl) showed higher catalytic activity and, and superior selectivity to allyl alcohol, as well as the production of 1-propanol, which is due to the hydrogen transfer. This selectivity agrees with H2-TPR results, which show stronger effect of the copper over the molybdenum oxide reduction, if compared to the others promoter (Co or Ni). At the end it is proposed the reaction steps mechanism for the glycerol conversion to allyl alcohol.