Non-isothermal in-situ (trans)esterification of lipids in pre-functionalized and lipid-dense post-hydrolysis spent coffee grounds with subcritical methanol at low subcritical condition

Kristelle L. Quijote, Alchris Woo Go, Artik Elisa Angkawijaya, Shella Permatasari Santoso, Chintya Gunarto and Siti Zullaikah

Renewable Energy, 2023, vol. 206, issue C, 111-124

Abstract: Pre-functionalized lipid-dense post-hydrolyzed spent coffee grounds (PHSCG) were used as feedstock for fatty acid methyl ester (FAME) production. The lipids in PHSCG were converted to FAME via non-isothermal in-situ (trans)esterification (ISTE). The conversion was achieved with methanol under subcritical conditions. This study investigates the influence of reactor loading (RL), solvent-to-solid ratio (SSR), temperature, and holding time. High FAME yield of ∼21 g/100g PHSCG can be achieved in about 1 h. Both extractable and bound fatty acids (FA) were converted to FAME. The apparent conversion (∼107%) or yield may exceed the expected extractable FA when using pre-functionalized and lipid-dense PHSCG without needing an additional catalyst. Under favorable conditions of 85% RL, 6 mL/g SSR, and reacted non-isothermally to 125 °C (∼0.8 MPa), a minimum conversion of ∼98% could be achieved depending on the PHSCG's characteristics. The residual acid sites in the post-ISTE residues recovered after ISTE still exhibited catalytic activity when used as a catalyst during the esterification of oleic acid with methanol. The catalytic activity of the residues was evaluated by reusing them for up to 7 cycles. Elemental analysis and FT-IR peak identification supported the presence of sulfonic acid sites providing the catalytic activity of PHSCG and its residues.

Keywords: Dilute acid hydrolysis; In-situ (trans)esterification; Lipid-dense biomass; Solid acid catalyst; Spent coffee grounds; Subcritical methanol (search for similar items in EconPapers)
Date: 2023
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:206:y:2023:i:c:p:111-124

DOI: 10.1016/j.renene.2023.02.045

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