Mechanistic aspects of the higher alcohol synthesis over unpromoted ZnCrO: 1-Propanol flow microreactor study

Mechanistic aspects of the higher alcohol synthesis (HAS) over a ZnCrO sample are investigated by flow-microreactor experiments of 1-propanol. Results indicate that the catalyst can promote a number of chemical functions including hydrogenation/dehydrogenation, ‘normal’ and ‘reversal’ aldolic-type condensation, ketonization, α-addition, dehydration. On comparing the data with those obtained over a K-promoted sample it appears that the alkali dopant does not affect the reactivity of ZnCrO towards hydrogenation/dehydrogenation and ‘normal’ aldolic-type condensation, is essential for ‘reversal’ aldolic-type condensation and α-addition, favors ketonization and essentially suppresses the dehydration function. Thus the alkali promoter, besides playing a crucial role in the C₁→C₂ step, significantly affects the chain growth mechanisms involving C₂₊ oxygenates and effectively preserves oxygenate molecules towards the production of undesired hydrocarbons by dehydration.