Direct conversion of toluene into styrene with high selectivity over a composite catalyst

Abstract Although side-chain methylation of toluene with methanol to produce styrene has been investigated in the past decades, commercial application of this process is still a great challenge due to the lack of efficient catalysts. Here we present a bifunctional catalyst composed of dehydrated sodium borate (Na2B4O7) and zeolite (CsX) that yields a high selectivity to styrene (89.6%) with a relative high toluene conversion (9.57%). Na2B4O7 not only contributes to the formation of the reaction intermediate formaldehyde but also constructs the frustrated Lewis pairs (FLPs) with basic sites on the zeolites, which could activate C–H bond in the methyl group of toluene more efficiently. Thus, the crucial role of boron species is revisited. The nature of cesium in CsX is found to be important for the reactivity of the bifunctional catalyst. Good reaction performance on composite catalyst Na2B4O7-CsX also depends on the spatial proximity and mass ratio of the two components.