High pressure fractionation of value-added products from lignin hydrolysis

FRANCISCO A. SÁNCHEZ; SELVA PEREDA

Campinas

Congreso; X Iberoamerican Conference on Phase Equilibria and Fluid Properties for Process Design (EQUIFASE 2022); 2022

Universidad Estatal de Campinas (UNICAMP)

In the context lignocellulosic biomass valorization, the fractionation of the depolymerized bio-oil products is a great challenge. There are several pathways to break down these natural polymers, among which are thermal treatments, such as pyrolysis and hydrolysis, as well as base-catalyzed depolymerization or oxidative cleavage. Regardless of the conversion technology, lignin degradation gives rise to a wide variety of polyfunctional aromatic rings, with different oxygenated substituents, such as hydroxyls, ethers, ketones and aldehydes, to name a few. It is worth highlighting that the diversity of compounds that are produced is strongly dependent on both, the raw material and the type of treatment. In this context, bio-oil refining calls for more research on separation technologies. In particular, pioneering works in the field of high pressure technology apply CO₂ extraction as a solvent-free non-destructive analytical method for the characterization of bio-oils; and, more recently, several reviews consider CO₂ extraction as a feasible technology for large-scale recovery of valuable compounds.The design and optimization of separation processes requires a robust thermodynamic model, able to predict the phase behavior of bio-oils. Lignocellulose derived bio-oils are complex multicomponent mixtures that comprise a large number of asymmetric compounds, show non-ideal behavior due to the presence of water and organo-oxygenates and contain polyfunctional molecules whose properties are generally unknown. Since the large number of compounds comprising the bio-oil belong to the few organic families mentioned above, the use of a group contribution approach is a convenient choice to facilitate the thermodynamic modeling of these mixtures.The Group Contribution with Association Equation of State (GCA-EOS) is particularly suitable for this purpose. It has already shown excellent performance to model the phase behavior of complex mixtures containing natural products and biofuels. As part of this work, we extend the GCA-EOS to describe the phase behavior of aromatic compounds from low- to high-pressure phase equilibrium data and their binary mixtures with CO₂. Next, we challenge the GCA-EOS to predict high-pressure phase behavior of lignin-derived polyfunctional aromatic compounds with CO₂ and assess the feasibility of using high-pressure CO₂ to fractionate a typical hydrolysate mixture reported in the literature.