High pressure phase equilibria prediction of renewable lignin derived aromatic compounds with CO2

SÁNCHEZ, FRANCISCO ADRIÁN; PABLO E. HEGEL; SELVA PEREDA

Coímbra

Congreso; 2º Encuentro Ibérico de Fluidos Supercríticos (EISC2022); 2022

Faculty of Sciences and Technology, Universidade de Coimbra

Biomass fractionation into its individual building blocks is a majorchallenge, in particular, for the valorization of low-cost rawbiomass or subproducts/residues from the biomass processing industry,like gums or kraft lignin from oil and pulp plants. Aromatic ringsare present in biomass as part of lignin structure and as linkingcompounds of carbohydrate polymers. There are several pathways tofractionate these natural polymers, among which thermal treatments,like pyrolysis and hydrolysis, are relevant, as well as basecatalyzed depolymerization or oxidative cleavage [1]. In fastpyrolysis, the bio-oil is a promising alternative to fossil fuels andis currently entering the heating oil market [2]. In addition, it canbe further processed to synthesis gas, from which synthetic fuels andchemicals can be obtained. Nonetheless, to boost the whole processeconomy, it is important to recover as much valuable compounds aspossible, prior to either burning or gasifying the bio-oil.Similarly, lignin hydrolysates also comprise aromatic compounds to berecovered from the pre-treatment product. In summary, bio-oilsrefining is calling for research in separation technologies, whichare key to trigger the development of biomass fractionationprocesses. In particular, related to high pressure technology,pioneer works in the field apply CO2 extraction as a non-destructivesolvent free analytical method for biooil characterization [3,4],and, more recently, several reviews consider CO2 extraction as afeasible technology for scale-up recovery of valuable compounds [5].As it is well known, to design andoptimize separation processes, is mandatory to count on a robustthermodynamic model, able to predict the phase equilibria ofbio-oils. Regardless of the upstream biomass depolymerizationtechnology, there are common features that bio-oils from differentsources share: 1) multicomponent mixtures comprising a large numberof complex asymmetric compounds, 2) non-ideal behavior due to thepresence of water and organo-oxygenated compounds, 3) multifunctionalmolecules whose properties are in general unknown. The phase behaviorof biomass derived mixtures is highly non-ideal due to the presenceof association and solvation effects. The numerous oxygenated derivedspecies belong to certain families of organic compounds (alcohols,carboxylic acids, esters, etc); thus, these complex mixtures withhundreds of compounds can be described by a reduced number offunctional groups. For this reason, the use of a group contributionapproach is a logical choice for thermodynamic modeling. The Group Contribution withAssociation Equation of State (GCA-EOS) is especially suited for thisaim [6]. It has already proved excellent predictive capacity torepresent the phase behavior of complex mixtures containing naturalproducts and biofuels. As part of this work, GCA-EOS is extended todescribe phase behavior of aromatic lignin derived compounds based onlow pressure phase behavior data of simple monofunctional aromaticcompounds and their binary mixtures with CO2 available inthe open literature. Once the aromatic functional groups areparametrized, the GCA-EOS will be challenged to predict high pressurephase behavior of multifunctional aromatic lignin derived compoundsin mixtures with CO2. p { text-align: justify; orphans: 2; widows: 2; margin-bottom: 0.21cm; direction: ltr; background: transparent }p.western { font-size: 11pt; so-language: en-US }p.cjk { font-size: 11pt; so-language: es-ES }p.ctl { font-size: 11pt }a:visited { color: #800080; text-decoration: underline }a:link { color: #0000ff; text-decoration: underline }