Synthesis and Characterisation of Sulfonated Polydivinylbenzene as Solid Acid Catalyst for the Production of Furfural

Abstract

Solid acid catalyst known as sulfonated polydivinylbenzene (PDVB-SO3H) was synthesised in order to replace homogenous mineral acid in furfural production. In this study, swelling mesoporous polydivinylbenzene (PDVB) underwent the sulfonation process in dichloromethane (CH2Cl2) using pure chlorosulfonic acid (HSO3Cl) with different concentrations (0.5% (wt/wt), 1.0% (wt/wt), 1.5% (wt/wt), 2.0% (wt/wt), and 2.5% (wt/wt). The sulfonation process was conducted in an ice bath (0°C to 5°C) under inert conditions using N2 gas and was continuously stirred for 8 hours. Each PDVB-SO3H was characterised by the acid-base titration and BET method. The catalytic activity of each PDVB-SO3H was then examined on the yield of furfural by varying the reaction time (20 min to 40 min), temperature (160°C to 180°C), and catalyst loading (0.05 g to 0.2 g) using microwave extraction. The highest furfural yield was 83.3% obtained at 170°C for 30 min using 0.1 g of the 2.0% (wt/wt) PDVB-SO3H catalyst. The BET results showed that the surface area of 2.0% (wt/wt) PDVB-SO3H was 224.67 m2/g after sulfonation. Meanwhile, the acid-base titration indicated that the total acid content of 2.0% (wt/wt) PDVB-SO3H was 4.04 mmol/g. The excellent performance of 2.0% (wt/wt) PDVB-SO3H was attributed to the high concentration of the sulfonic group as well as its mesoporous structure.