Effect of Doping Metal Oxide in ZnO/SBA-15 on Its Acid-Base Properties and Performance in Ethanol-to-Butadiene Process

The Ethanol-to-Butadiene (ETB) process is experiencing a renaissance with the increasing shortage of petroleum-based resources, however, the development of active catalysts for this process still remains sluggish due to the lack of fundamental understanding of the properties of catalysts, especially acidity and basicity. We present here that individual reaction step in the ETB process requires specific acid or/and basic sites with different strengths and densities. Weak acid and moderate basic sites are beneficial for ethanol dehydrogenation, while moderate basic sites with optimal strength are also active for condensation and Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reactions. In contrast, moderate and strong acid sites cause the ethanol dehydration, lowering the selectivity towards 1,3-butadiene (BD) production. Moreover, the selectivity and yield of BD are more dependent on the properties of sites for both condensation and MPVO reactions than for dehydrogenation reaction.