The Development of a Porous Phenol-Sulfonic Acid Resin: Design, Preparation, and Its Use in Catalytic Esterification

Abstract

Organic esters are important products or intermediates in the chemical and pharmaceutical industries. The most straightforward way for the preparation of esters is the acid-catalyzed esterification reaction. Heterogeneous solid acid catalysts have been used in various industrial applications because of their merit such as easy separation, easy regeneration, recyclability, better reaction selectivity, and extensive standing stability. The author developed heterogeneous polymeric acid catalysts for direct esterification and transesterfication without removal of coproducts of water and alcohols as follows:

Chapter I shows the general introduction of the direct esterification and transesterfication

Chapter II shows the preparation of heterogeneous porous acid catalysts for the direct esterification of carboxylic acids with alcohols and the transesterification of esters with alcohols. The condensative polymerization of p-phenolsulfonic acid with formaldehyde was performed at 120 °C for 6 h to give a brownish acid catalyst as hardly soluble precipitates.

Chapter III shows the direct esterification of carboxylic acids with alcohols that is the important transformation in organic syntheses. The direct esterification of various alcohols and carboxylic acids is carried out with 0.7 mol% (SO3H residue) of acid catalyst at 50-80 °C under solvent-free conditions without removal of water to afford the corresponding esters in 92-95% isolated yield. Moreover, the flow esterification for the synthesis of biodiesel fuel was also achieved by using a column-packed macroporous acid catalyst under mild conditions without removal of water.

Chapter IV shows the transesterification of esters with alcohols. Thus, the transesterification of various alcohols and esters is carried out with 0.7 mol% SO3H residue of the macroporous acid catalyst at 80 °C under solvent-free conditions to afford the corresponding esters in 78-97% isolated yield. Moreover, the transesterification of 1-octanol with ethyl acetate was applied to the continuous flow reaction by using a column-packed macroporous acid catalyst under mild conditions.

Chapter V shows the conclusion of the doctoral thesis.