Inert competitive adsorption for the inhibition of oligomerization of alkenes during alcohol dehydration

Abstract

Inhibition of secondary chemistries in a linear series of reactions remains a catalytic challenge, particularly when targeting the selective synthesis of intermediate chemicals. In this work, the inhibition of cyclohexene oligomerization following cyclohexanol dehydration with H-BEA zeolite catalyst was achieved with the addition of 2,5-dimethylfuran (DMF). Suppression of undesired olefin oligomerization occurred with the competitive adsorption of the hydrolysis product of DMF, 2,5-hexanedione, thereby preventing cyclohexene adsorption onto Brønsted acid sites. Activation energies were measured for cyclohexanol dehydration both with and without DMF and were found to be the same within experimental error, suggesting that DMF does not alter the catalytic mechanism of cyclohexanol dehydration. Adsorption models were generated to investigate the general case of adding inert chemicals to inhibit product side reactions. Allowable differences in free energies of adsorption between reactant, product, and inert necessary to promote inhibition of product adsorption, while allowing for reactant surface saturation, were quantitatively determined. Reactions that might benefit from the addition of inert chemicals were proposed including linear alcohol dehydration and benzyl acylation and alkylation.