Molecular interaction between ionic liquids with lignin dimers

Abstract

Biomass is an alternative to using fossil fuels. It is made up mainly of agricultural and forestry residues. The main components of biomass are cellulose, hemicellulose, and lignocellulose (Li, 2015). Due to the structure of lignin and its chemical properties, chemical products based on aromatic compounds and fuels can be obtained (Sangha, 2012). However, its recalcitrant nature and the difficulties encountered in effecting depolymerization, coupled with its low solubility with common organic solvents, result in conversion processes that use extreme conditions of temperature, pressure and acidity (Hicks, 2011). Ionic liquids (ILs) are advantageous solvents for the conversion of lignin to a value-added product due to their ease of dissolving it. In this work we studied the interaction of nine different ILs, formed between the [EMIM+], [BMIM+] y [HMIM+] and the anions [BF4-], [OAc-] and [Cl-], whose use has been reported in the industrial pretreatment of lignocellulose (For, 2007), and lignin dimersderived from coniferyl alcohol (one of the basic units of lignin), which contain the characteristic β-O-4 bond of the biopolymer. Born-Oppenheimer (DMBO) quantum molecular dynamics calculations were performed with the BIOVIA 2016 Materials Studio program (BIOVIA, Dassault Systèmes, 2017), varying the pressure and temperature conditions with the micro canonical assemblies NVE and NVT. The results obtained with the NVE and NVT assemblies show that for some LIs the interaction is favorable and for others there is a great destabilization of the Lignin-IL interaction.