(544bg) Simple and Cost-Effective Treatment to Enhance Hydrophobicity of Zeolites

Defined pores and high temperature stability make zeolites effective catalysts for a variety of reactions. However, one limitation that zeolites pose is that the presence of water even in small quantities can cause structural instability and/or deactivation of the active sites. Researchers have employed different strategies including functionalizing the zeolite surface with organosilanes and crystallization under fluoride mediated conditions to make the zeolites more hydrophobic. Yet, preventing water from interacting with the zeolite matrix in a reaction system is still a challenge. Therefore, there is a need to design novel zeolite catalysts with enhanced hydrophobicity. In this work, a simple and effective technique that uses common organic solvents to create a hydrophobic layer on the zeolite particles is demonstrated. The hydrophobicity is maintained even after calcination in air at 300°C, allowing regeneration of catalyst without losing the benefit of hydrophobic layer. In addition to increasing the stability of solid-acid catalysts under aqueous conditions, the hydrophobicity also results in increased selectivity in the processes where water promotes side reactions. This is shown via epoxide ring opening reaction with alcohols, where the hydrophobic catalyst prevents the formation of water ring opening product thereby increasing the selectivity of the process. In summary, this work demonstrates a simple and effective technique to engineer a hydrophobic layer on the zeolite particles.