Synthesis, characterisation and catalytic performance of boron substituted SBA-15 molecular sieves

Abstract

Boron substituted mesoporous SBA-15 molecular sieves with varying boron content were synthesised by hydrothermal method. The effects of incorporation of boron in the framework on the structure, crystal parameters, framework vibrations and textural properties of SBA-15 were discussed based on the results from XRD, FT-IR and nitrogen adsorption studies. The morphology changes due to boron incorporation were monitored by SEM analysis. The coordination environment of boron in the framework was revealed by 11B MAS NMR and MQMAS NMR techniques. The type of acid sites created by boron incorporation was analysed by DRIFT study of pyridine adsorbed catalysts. All the characterisation results indicate the successful incorporation of boron in the silica framework of SBA-15 in both tetra and tri coordination. Isopropylation of naphthalene with isopropyl alcohol was carried out to test the acidity of the synthesised materials. The effects of reaction temperature, feed ratio and feed space velocity on naphthalene conversion and products selectivity were discussed. The higher activity in naphthalene conversion and selectivity of di-isopropylated naphthalenes were accounted in terms of the increased acid sites due to boron incorporation in the framework.