Study the Effect of Various Sulfonation Methods on Catalytic Activity of Carbohydrate-Derived Catalysts for Ester Production

In the present study, four types of sulfonation method, including thermal treatment with concentrated sulfuric acid (H2SO4), thermal decomposition of ammonium sulphate (NHSO4), thermal treatment with chlorosulfonic in chloroform (HSO3Cl), and in situ polymerization of poly(sodium4-styrenesulfonate) (PSS), were employed to convert incomplete carbonized glucose (ICG) to sulfonated heterogeneous catalysts for the fatty acid methyl ester (FAME) production. The characteristics of synthesized catalysts were further examined using Raman spectroscopy, Fourier transformation infrared (FT-IR), ammonia temperature programmed desorption (NH3-TPD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). According to experiments, the sulfonic acid density was varied in a range from 4.408 to 14.643 mmol g−1 over various sulfonation methods. The catalytic activity of synthesized catalysts over different sulfonation methods was determined by performing the conversion of palm fatty acid distillate (PFAD) to ester synthesis in a batch-system reactor. The findings reveal that using PSS-ICG resulted in the highest FAME yield of 96.3% followed by HSO3Cl-ICG of 94.8%, NHSO4-ICG of 84.2%; and H2SO4-ICG of 77.2%. According to results, the ICG sulfonated by PSS method with the highest acid density (14.643 mmol g−1) gave the highest catalytic activity over PFAD conversion to biodiesel. According to experiment results, acid density played a crucial role over FAME yield percentage. Besides acid density, it is also worth mentioning that various sulfonation methods including different mechanisms, chemicals and sulfonating agents played crucial roles in the FAME yield percentage.