Liquid phase alkylation of phenol with 4-hydroxybutan-2-one in the presence of modified zeolite HBEA Original Research Article

Liquid phase alkylation of phenol with 4-hydroxybutan-2-one was carried out in presence of H-beta zeolite modified by different techniques, such as thermal treatment, acid washing, ion-exchange and surface passivation. Thermal- and acid-treated samples showed decrease in activity due to the removal of aluminium from the framework. The new Lewis acid sites generated by thermal treatment increased the selectivity of the O-alkylated product. Ion-exchange with cesium favoured the O-alkylated product due to the introduction of basic sites. Low temperature favoured the O-alkylated product, whereas high temperatures favoured the para alkylated product. When methyl vinyl ketone was used as the alkylating agent instead of 4-hydroxybutan-2-one, the change led to an increase in the selectivity of oligomers and other polyalkylated products. The increase in the concentration of the alkylating agents increased the selectivity of the O-alkylated product, due to the greater possibility of nucleophilic attack of phenoxide ion over the alkylating agents. The increase in the catalyst weight decreased the yield of O-alkylated product and increased the yield of para alkylated product. This demonstrated the conversion of the O-alkylated product into the para alkylated product. The studies on the rearrangement of the O-alkylated product which was synthesised separately also confirmed this fact. The para to O-alkylated product ratio observed over surface-passivated H-beta zeolite was the same as that observed over H-beta. This identity showed that the rearrangement takes place mainly inside the micropores.