Industrial crude bioethanol dehydration to ethylene: Doping ZSM-5 to enhance selectivity and stability
Eliana Quiroga, Nicolás García-Aracil, Bernay Cifuentes, Ricardo Cogua, Jorge Becerra, Julia Moltó Berenguer, Martha Cobo
Abstract
Although the conversion of bioethanol into light olefins is one of the most studied processes in biorefinery schemes, there is a need to develop materials more capable of operating at industrial conditions (WHSV > 20 h −1 crude bioethanol feed). Hence, in this study, we dehydrated crude bioethanol samples derived from sugarcane fermentation to produce ethylene over a series of H-ZSM-5 zeolites . Among them, H-ZSM-5 with different Si/Al ratios (26, 280, and 371) and doped with Ce and Cu were tested on the catalytic activity and stability. Accordingly, a 26 Si/Al ratio showed full conversion and ethylene selectivity at 300 °C with a WHSV of 30.2 h −1 . When doping the zeolites, a decrease in relative crystallinity and a higher amount of acid sites were observed, which affected the interaction with reactants. This interaction was deeply analyzed by the in-situ DRIFTS , which showed that ethanol adsorption is lower for doped zeolites, but the desorption rate is higher, showing higher stability over longer reaction times. Therefore, the H-ZSM-5 with a Si/Al ratio of 26 and doped with Ce maintained its activity and improved its selectivity over 140 h under more drastic conditions of WHSV (42.3 h −1 ). These results elucidate that Ce-doped H-ZSM-5 zeolites can improve stability and represent a starting point for large-scale crude bioethanol conversion.