DOI: 10.14457/tu.the.2017.333
title: Biodiesel production from waste palm oil using waste biomass derived solid acid catalysts

description: Production of biodiesel from waste palm oil (WPO) can provide alternative energy and at the same time reduce the problems created by disposal of WPO. In addition, use of solid acid catalysts (SACs) derived from waste biomass for biodiesel production, makes the overall process more economical and sustainable. In this study, desired carbon based SACs were synthesized from palm empty fruit bunch (PEFB), coconut meal residue (CMR), and coconut coir husk (CCH) as waste biomass, adapting two simple protocols; direct in-situ one step concentrated H2SO4 carbonization (DS) and sulfonation of incompletely carbonized biomass (BCS). Prepared catalysts were duly characterized for physical and chemical properties. The activity of the catalysts was studied for biodiesel production from WPO (5.2%) in an open (using a reflux reactor) and closed (using a laboratory scale autoclave and microwave assisted reactor) systems. The fatty acid methyl ester (FAME) yield was determined by gas chromatography. The presence of active functional groups, such as SO3H, COOH, and OH on the surface of the catalysts was confirmed by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results showed that the catalysts prepared from DS protocol have high sulfonic acid groups compared to BCS protocol. Despite the high acid density, they have low surface area compared to the catalysts prepared from BCS protocol. Among the catalysts prepared from DS protocol, PEFB-DS-SO3H and CMR-DS-SO3H showed the highest FAME yields of 91% and 92.7%, respectively, under optimum conditions in an open reflux reactor. For CMR-DS-SO3H, the highest FAME yield of 95.5% was obtained at 150 °C and 3 h reaction time in an autoclave assisted reactor, and 94.7% FAME yield at 70 °C and 40 min in a microwave assisted reactor. However, CCH-DS-SO3H catalyst which showed a poor activity in an open reflux reactor was able to give a maximum FAME yield of 89.8% using 10 wt. % catalyst at 130 °C and 3 h using an autoclave reactor. It was also found that PEFB-DS-SO3H, CMR-DS-SO3H, and CCH-DS-SO3H can be re-used for at least four cycles without significant loss of the catalytic activity. Even though, PEFB-BCS-SO3H, CMR-BCS-SO3H, and CCH-BCS-SO3H showed poor activity during biodiesel production in an open reflux reactor, they showed higher catalytic activity in a microwave assisted reactor.  This study indicated that PEFB, CMR, and CCH as waste biomass can be used for SACs preparation and sustainable biodiesel production. DS is a simple and economical protocol for SAC preparation and prepared catalysts can be successfully employed for biodiesel production from WPO (5.2% FFA). The presence of high amounts of both strong (SO3H-contributing to a high acid density) and weak (COOH and OH-acting as the anchoring sites) acid groups bonded to the hydrophobic carbon structure is a possible reason for the high activity of the catalysts. Biodiesel production using an autoclave and a microwave assisted reactor provided a good yield at relatively low reaction time compared to an open-reflux reactor. However, it is required to understand the cost-effectiveness and sustainability of the overall process through a life cycle assessment. It was found that the fuel properties of the produced biodiesel meet the international standards.