An efficient heterogeneous acid catalyst derived from waste ginger straw for biodiesel production

A green heterogeneous acid catalyst derived from agro-industrial waste obtained from ginger straw was prepared via partial carbonization, followed by sulfonation using sulfuric acid. Three variables, including the carbonization temperature, carbonization time and sulfonation temperature, were optimized to achieve the ideal preparation conditions and the as-synthesized catalyst was characterized using X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, N-2 adsorption-desorption and acid density studies to reveal the relationship between its catalytic performance and physical-chemical properties. The results show that the ginger straw-based catalyst prepared via carbonization for 60 min at 350 degrees C, followed by sulfonation at 105 degrees C, has an amorphous carbon structure with an -SO3H group density of 1.05 mmol/g. In addition, the catalyst exhibits thermal stability up to 200 degrees C and satisfactory catalytic performance (93.2% conversion) during the esterification of oleic acid using methanol under the optimized reaction conditions (9:1 M ratio of methanol to oleic acid; catalyst loading, 7 wt%; reaction temperature, 64 degrees C; reaction time, 210 min). Although its catalytic activity was later found to decrease with cycling, the spent catalyst remains stable after the 5th cycle with a conversion of 65.6%. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The catalyst derived from ginger straw exhibited satisfactory catalytic performance in the esterification of oleic acid with methanol, with a high conversion rate. However, its catalytic activity decreased with cycling, although the spent catalyst remained stable after the 5th cycle with a relatively high conversion rate.