Acrolein Production from Glycerol: A Systematic Investigation of Metal-Oxides and Zeolite Catalysts

Abstract

Molecular sieves (H-ZSM-5 and US-HY), commercial oxides (alumina and niobium), and modified aluminas (MgO/F-Al₂O₃ and F-Al₂O₃) were used as catalysts in the gas-phase glycerol dehydration reaction to produce acrolein. The glycerol–water mixture was vaporized before being fed into a Haber-Bosch-type reactor containing the catalysts, operating within a temperature range of 320 to 450 °C at near-atmospheric pressures, which is the main advantage of this process. Maximum glycerol conversion was achieved at higher temperatures for all catalysts, while the best selectivity was observed at intermediate temperatures (380–385 °C). However, the two zeolite catalysts exhibited distinct behaviors, despite similar yields (60–65%). The US-HY demonstrated better performance at higher space velocities (LHSV), similar to nonzeolitic catalysts, unlike H-ZSM-5. Although nonzeolitic catalysts achieved similar yields of over 80% at their respective optimal conditions, the feed composition when using Nb₂O₅ was more diluted than with F-alumina. Internal mass transfer, acid site strength, and steric hindrance are crucial parameters affecting the behavior of these catalysts.