Hierarchical zeolites as efficient catalysts for dehydration of substituted indanols

Hierarchical zeolites of different topology and morphology (Al-, Ga- and B-silicate zeolites of MOR, BEA, MFI and MTW structural types with the morphology of aggregated nanosheets, nanorods, or close to spherical nanoparticles) were evaluated in the dehydration of a homologous series of substituted 4-bromo-2-alkyl-2,3-dihydro-1H-indan-1-ols. The optimal strength of the catalyst's acid sites providing both high indanols conversion and selectivity towards indenes (up to 99%) was found for each of the studied substrates. Stronger acid sites than optimal ones resulted in the formation of by-products of self-alkylation of the initial indanols by the formed indenes or alkylation of benzene used as a solvent. Weak acidity of the catalysts led to low substrate conversion and the presence of the corresponding ether. A correlation between the catalyst acidity and the yield of the desired product was found. Medium strength acid sites were discovered to be preferable for the selective dehydration of substituted 4-bromo-2,3-dihydro-1H-indan-1-ol.