Sulfonic acid catalysts based on porous carbons and polymers

Abstract

Liquid acid catalysts like sulfuric acid and hydrofluoric acid have been used as a catalyst for many years. However, these liquid acids have many inevitable problems, such as corrosion, toxicity, and difficulty of separation and recovery from the reaction medium. This thesis work aims to prepare solid sulfonic acid catalysts by sulfonation of porous carbons and polymers, eventually achieving an environmentally benefit chemical process.

Mesoporous carbons and carbon-silica composites were sulfonated. A low carbonization temperature was observed to be important for achieving a good catalytic activity in esterification reaction. Polymer materials including polypyrrole nanospheres and mesoporous phenol resins were synthesized and converted to carbon nanospheres and mesoporous carbons. Subsequent sulfonation of the polymer materials was conducted. Results showed that sulfonated polymeric materials displayed a better catalytic activity and recycleability than sulfonated carbon nanospheres and mesoporous carbons. Amongst, sulfonated polystyrene-divinylbenzene spheres exhibited the best catalytic activity and stability.

Kinetic study for esterificaton reaction of methanol with acetic acid catalyzed by sulfonated polystyrene-divinylbenzene was conducted using initial rate method and a model was proposed. The apparent order of reaction rate showed the concentrations of both acetic acid and methanol had positive affect on the reaction rate. The results also indicated that single active site was involved in heterogeneous reaction.