Bifunctional biomass-based catalyst for biodiesel production via hydrothermal carbonization (HTC) pretreatment – Synthesis, characterization, and optimization

Authors: FADZILAH ABDULLAH, ROSE - Universiti Putra Malaysia; RASHID, UMER - Universiti Putra Malaysia; LOKMAN IBRAHIM, MOHD - Universiti Teknologi Mara (UITM); LOKMAN NOLHAKIM, MUHAMMAD - Universiti Teknologi Mara (UITM); Moser, Bryan; ALHARTHI, FAHAD - King Saud University

Submitted to: Process Safety and Environmental Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2021
Publication Date: 10/11/2021
Citation: Fadzilah Abdullah, R., Rashid, U., Lokman Ibrahim, M., NolHakim, M.A.H.L., Moser, B.R., Alharthi, F.A. 2021. Bifunctional biomass-based catalyst for biodiesel production via hydrothermal carbonization (HTC) pretreatment – Synthesis, characterization, and optimization. Process Safety and Environmental Protection. 156:219-230. https://doi.org/10.1016/j.psep.2021.10.007.
DOI: https://doi.org/10.1016/j.psep.2021.10.007

Interpretive Summary: This research reveals that inexpensive, low-quality alternative feedstocks such as used cooking oil can be used directly for biodiesel production without the need for expensive and time-consuming pretreatment. This is made possible by a new catalyst from biomass that is capable of simultaneous transesterification (the traditional biodiesel production method) and esterification (the process that occurs during pretreatment). The new catalyst is prepared by modifying solid waste from palm oil processing by a simple process called hydrothermal carbonization. These results will be important to biodiesel producers, distributors, and end-users (customers) because a new process was described that enables production from low-quality feedstocks. This research may ultimately improve market penetration, availability, and public perception of domestically produced agricultural fuels such as biodiesel, thus affording greater national independence from petroleum-based fuels.

Technical Abstract: The hydrothermal carbonization (HTC) technique is known for its advantages in producing hydrochar from biomass samples with high water content compared to conventional pyrolysis techniques. This study utilized HTC to produce an activated carbon catalyst from renewable mesocarp fiber derived from palm oil processing. The introduction of K2CO3 and Cu(NO3)2 produced a bifunctional catalyst suitable for conversion of used cooking oil to biodiesel. The catalyst possessed a mesoporous structure with a BET surface area of 3909.33 m2/g. An optimum treatment ratio of 4:1 (K2CO3 to Cu(NO3)2) provided elevated basic (5.52 mmol/g) and acidic (1.68 mmol/g) concentrations on the catalytic surface, which promoted esterification and transesterification reactions. Maximum yield (96.4%) of biodiesel was obtained at 70 °C for 2 h with 5 wt.% catalyst and a 12:1 molar ratio of methanol to oil. The catalyst endured up to 5 reaction cycles while maintaining biodiesel yields of more than 80%. These findings indicated that HTC pretreatment yielded a high-quality bifunctional catalyst for conversion of low-quality used cooking oil for production of biodiesel.