Towards a better understanding of the HTL process of lignin-rich feedstock

Abstract

The hydrothermal liquefaction reactions (HTL) in subcritical conditions of a lignin residue has been studied on a lab scale. The starting material was a lignin rich residue co-produced by an industrial plant situated in Northern Italy producing lignocellulosic bioethanol. The reactions were carried out in batch mode using stainless steel autoclaves. The experiments were under the following operating conditions: two different temperatures (300–350 °C), the presence of basis catalysts (NaOH, and NH4OH) in different concentrations and the presence/absence of capping agent 2,6-bis-(1,1-dimethylethyl)-4-methylphenol (BHT). Lignin residue and reaction products were characterized by analytical and spectroscopic techniques such as CHN-S, TGA, GC–MS, EPR, and 1H-NMR with (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (T.E.M.P.O.). The addition of BHT did not significantly affect the yield of char which is formed by radical way. Spectroscopic analysis indicated that the level of radicals during the reaction was negligible. Therefore, the results obtained experimentally suggest that the reaction takes place via an ionic route while radical species would play a minor role.

Highly active and magnetically recoverable heterogeneous catalyst for hydrothermal liquefaction of biomass into high quality bio-oil

“…While corn straw and food wastes are rich in cellulose and carbohydrates, respectively, draff contains higher fractions of lignin, protein, and lipids with recalcitrant C-C and C -O bonds which require strong acid/metal sites to cleave. HTL of lignin under basic conditions produces phenolic monomers which are prone to repolymerise into oligomers increasing solid formation (Ciuffi et al, 2021). Base catalysts have also been found to be detrimental for the conversion of protein and lipid-rich feedstocks due to the inefficiency of alkali catalysts to break the peptide and ether linkage bonds (Shah et al, 2022).…”

Biomass carbon mining to develop nature-inspired materials for a circular economy

“… Biomass type HTL conditions Elemental composition of biocrude oil Reference Polysaccharides Starch Isothermal Ketones, phenols, indanone derivatives, furan derivatives, benzene derivatives Gollakota and Savage 161 , 162 Fast Ketones, phenol, furan derivatives, benzene derivatives, acids Cellulose Isothermal Ketones, phenols, indanone derivatives, furan derivatives, benzene derivatives Fast Phenols, furan derivatives, benzene derivatives, acids, alcohols, esters, hydrocarbons Amylopectin Isothermal Ketones, phenols, indanone derivatives, furan derivatives, benzene derivatives Fast Ketones, phenols, furan derivatives, acids, alcohols, esters, hydrocarbons Amylose Isothermal Ketones, phenols, indanone derivatives, furan derivatives Fast Ketones, phenols, furan derivatives, benzene derivatives, acids, alcohols, esters, hydrocarbons Pectin Isothermal Ketones, phenols, indanone derivatives, furan derivatives, benzene derivatives Fast Ketones, phenols, furan derivatives, benzene derivatives Chitin Isothermal Ketones, phenols, indanone derivatives, benzene derivatives, nitrogenous compounds Fast Ketones, phenols, furan derivatives, hydrocarbons, nitrogenous compounds Lignin Light oil, isothermal, NaOH 2% Phenol, m/p-cresol, guaiacol, creosol, 3-methoxycatechol, p-ethyl-guaiacol, syringol, 4-propylguaiacol Ciuffi et al. 163 Light oil, isothermal, NH 4 OH 8% Phenol, m/p-cresol, guaiacol, creosol, catechol, p-ethyl-guaiacol, 3-methylcatechol, syringol, 4-ethylcatechol Ciuffi et al. 163 Fast Catechols, anisoles, alkyl phenols, guaiacols, benzene derivatives, others (xanthene, 2,3,4-trimethoxybenzoic acid, 2-phenyl-4-tert-butylphenol, coniferaldehyde, 1,2-diphenylethanone, guaiacylacetone) Yong et al.…”

Sustainable Valorization of Wood Residue for the Production of Biofuel Materials Via Continuous Flow Hydrothermal Liquefaction

“…The higher pH values occur due to lignin decomposition. It is a complex decomposition process, and it is unclear which compounds contribute the most [45].…”