Conversion of butanol to propene in flow: A triple dehydration, isomerisation and metathesis cascade

A combined three-step flow cascade conversion of n-butanol to propene is demonstrated. Zeolite H-ZSM-5 gives high conversion in the initial n-butanol dehydration step (98%). Subsequent isomerisation of terminal butenes to internal butenes over zeolite H-Fer takes place with good conversion (87%). Finally, cross-metathesis with ethene over a tungsten on acid-washed SiO2/Al2O3 catalyst affords propene with good selectivity (65%). Coupling these three steps into a single flow sheet gives an overall yield of 64% propene from n-BuOH. Ethene cross-metathesis catalyst performance was probed using 2-pentene as a model co-substrate giving good conversion (~90%) and moderate selectivity to butenes (67%).