ABSTRACT
Selective deoxygenation is one of the common unit processes in biomass conversion [4], which is exemplied here by demonstrating our own work on hydrodeoxygenation (hydrogenolysis) of glycerol to 1,2-PDO. Glycerol is the smallest, highly functionalized polyol obtained from biomass either directly or as a by-product of (i) industrial conversion of lignocelluloses into ethanol [5,6] and (ii) biodiesel production [7,8]. With wide industrial applications of 1,2-PDO, its production
CONTENTS
9.1 Introduction .......................................................................................................................... 167 9.2 Experimental ........................................................................................................................ 168 9.3 Results and Discussion ......................................................................................................... 169 9.4 Conclusions ........................................................................................................................... 179 References ...................................................................................................................................... 180
from glycerol becomes a viable sustainable process as is evident from the rst commercial plant (Archer Daniels Midland Co., Chicago, Illinois, United States) having a capacity of 0.1 million tpa [9-11]. Glycerol hydrogenolysis involves parallel and series reactions producing several products, as shown in Scheme 9.1. However, 1,2-PDO formation via dehydration is more acceptable due to simple preparation methods of catalyst systems having inherent acidic properties. Between the noble and nonnoble metal catalysts reported for glycerol hydrogenolysis, the choice of the latter-in spite of lower activity-is obvious due to their (i) much lower prices, (ii) higher resistance to poisoning by trace impurities, and (iii) their suppression of C-C cleavage [9]. The pioneering work of Suppes on Cu-Cr catalysts for glycerol hydrogenolysis was subsequently studied extensively by several other researchers for further improvement in catalyst stability, activity, and selectivity [12-16]. In all these studies, Cr containing catalysts have been shown to be the robust and most efcient systems for glycerol hydrogenolysis. However, active research efforts are ongoing to develop new catalysts without chromium [17-19]. In continuation of our efforts to understand the structure activity correlation of catalysts in glycerol hydrogenolysis, here we discuss the effect of combination of alkaline earth (Mg, Ba) and transition (Zn, Cr, Al) metals with Cu on activity and product selectivity. The activity of these catalysts was studied in an aqueous as well as in an organic medium. One of the best catalysts, Cu-Al, was tested for the in situ glycerol hydrogenolysis without use of external hydrogen.
