One-step synthesis to enhance the acidity of a biocarbon-based sulfonated solid acid catalyst

Abstract

The main purpose of this study is to produce and generate a solid acid catalyst from biomass with high reactivity that can be used in catalytical reactions such as hydrolysis, and is environmentally friendly and reusable. A biocarbon-based sulfonated catalyst was prepared by the carbonization of palm empty fruit bunches (PEFB), followed by sulfonation. In order to enhance the acidity of the biocarbon, different concentrations of hydroxyethylsulfonic acid were added to the solution during sulfonation at 180 oC for 4 h in a Teflon stainless steel autoclave. The H+ ion capacity of the biocarbon-sulfonated acid catalyst (BSC) was increased twofold (3.57 mmol/g) in the presence of 10% of hydroxyethylsulfonic acid and 10% of acrylic acid. XRay Fluorescence (XRF) analysis showed that the BC-SO3H contained 38% of S. The original structure of the PEFB after carbonization disintegrated from the fibrous materials onto porous carbon. The crystalline index (CrI) of the PEFB significantly decreased to about 32% and a wide broad peak of a X-Ray Diffraction (XRD) pattern of around 20-30o were observed, which shows that an amorphous biocarbon structure had been identified. Fourier Transform Infra-Red (FT-IR) analysis confirmed that the -SO3H, COOH and -OH functional groups were deposited on the carbon due to specific peaks at around 1180 cm-1, 1724 cm-1 and 3431 cm-1, respectively. Decomposition of the sulfonic groups on the biocarbon-sulfonated solid catalyst was observed from 227.9 oC, as it shown by thermal gravimetric analysis (TGA).