The green synthesis of a palm empty fruit bunch-derived sulfonated carbon acid catalyst and its performance for cassava peel starch hydrolysis.

A sulfonated carbon acid catalyst (C-SO 3 H) was successfully generated from palm empty fruit bunch (PEFB) carbon via hydrothermal sulfonation via the addition of hydroxyethylsulfonic acid and citric acid. The C-SO 3 H catalyst was identified as containing 1.75 mmol g -1 of acid and 40.2% sulphur. The surface morphology of C-SO 3 H shows pores on its surface and the crystalline index (CrI) of PEFB was decreased to 63.8% due to the change structure as it became carbon. The surface area of the carbon was increased significantly from 11.5 to 239.65 m 2 g -1 after sulfonation via hydrothermal treatment. The identification of -SO 3 H, COOH and -OH functional groups was achieved using Fourier-transform infrared spectroscopy. The optimal catalytic activity of C-SO 3 H was achieved via hydrolysis reaction with a yield of 60.4% of total reducing sugar (TRS) using concentrations of 5% (w/v) of both C-SO 3 H and cassava peel starch at 100 °C for 1 h. The stability of C-SO 3 H shows good performance over five repeated uses, making it a good potential candidate as a green and sulfonated solid acid catalyst for use in a wide range of applications.