Silica-supported heteropoly acids as catalysts for low-temperature dehydration of 1-butanol in the gas phase: Application and mechanistic insight

• Gas-phase 1-BuOH-to-butene dehydration over supported HPA catalysts investigated. • The HPA catalysts showed greater activity and performance stability than zeolites. • The reaction obeys the Langmuir rate equation and is zero order in 1-BuOH at a partial pressure ≥1 kPa. • A positive correlation between catalyst acid strength and reaction turnover rates was established. • Evidence provided that the reaction proceeds via a surface-type mechanism through an E2 elimination pathway. Dehydration of 1-butanol primarily produces n-butene isomers, key olefinic feedstocks in the chemical industry. The reaction was studied in the gas phase using silica-supported Keggin heteropoly acids (HPAs) H 3 PW 12 O 40 (HPW) and H 4 SiW 12 O 40 (HSiW) as solid acid catalysts. The HPA catalysts were benchmarked against zeolites, such as H-ZSM-5, H-Mordenite and HY, the established catalysts for alcohol dehydration. The HPA catalysts were found to exhibit significantly higher activity and performance stability than zeolites. 25% HPW/SiO 2 and 25% HSiW/SiO 2 catalysts produced n-butene isomers at 130 °C with 99% selectivity (1-butene (8.4%) < cis-2-butene (30.3%) < trans-2-butene (61.3%)) at 99% conversion of 1-butanol and maintained stable performance for at least 24 h. The HPA-catalysed dehydration of 1-butanol followed the Langmuir rate equation, becoming zero-order in 1-butanol at partial pressures ≥1 kPa. A positive correlation between catalyst acid strength and reaction turnover rates was established. Evidence was provided that the reaction proceeds via a surface-type mechanism through an E2 elimination pathway.