Glycerol conversion in presence of CO2: solvent absence in semi-batch reactor.

Glycerol conversion with CO2 in liquid phase in a semi-batch system was investigated. γ-Al2O3 supported catalysts with 13 wt% Ni, Co, Cr and Zn content were prepared, and a reduction-passivation process was performed. Passivated catalysts were characterized by XRD, TPR, BET and XPS techniques. TPR profiles showed that 65% of total Ni content and 39% of total Co content, was reduced; which was not observed for Zn and Cr catalysts. This fact was confirmed by XRD analysis, where the presence of Ni and Co metallic phases was observed, for Ni and Co catalysts, respectively, while diffractograms of Cr and Zn catalysts presented Cr2O4 and ZnAl2O4 peaks, respectively. Thus, it is observed that reduction-passivation process was efficient. Ni catalyst presented a higher activity and selectivity, with 38% of glycerol conversion, while Co catalyst presented a conversion of 14% with deactivation after 100 min of reaction (Figure 1). Zn and Co presented a very low activity. Semi-batch system remarkably improved gas and liquid phases selectivity above 250 °C during 6 h, when compared to batch system, studied in previous work [1]. In the presence of Ni and Co catalysts, were obtained the same products: H2O, 1,2-Diformyloxypropane, 2-(ethoxymethyl)oxirane, 2-propoxymethyl-oxirano, pinacolone and acetol, representing 50 and 70% of total yield, respectively. Recycle reactions performed with Ni catalyst presented a decreased of 50%, approximately, from408 to 206 g of converted glycerol per gram of Ni0, after 3 h of recycle reaction.