Study of Conversion of Bio-oil Model Compounds in Supercritical Water Using Density Functional Theory

Abstract

It is well known that supercritical water is a favourable medium for biomass conversion followed by its hydrodeoxygenation (HDO). Moreover, the actual kinetics and mechanism of reaction occurring in the supercritical water are not yet completely understood, either by experimental or computational approaches. Within the framework of DFT, the major challenge is non-availability of models to simulate supercritical phase. In this study, the authors manually define the descriptors of a solvation model to describe an implicit supercritical phase. In order to examine the suitability of supercritical water for thermal and hydrotreatment of bio-oil model compounds, nine different reactions involving conversion of furfural, tetrahydrofuran, xylose, phenol, guaiacol, ferulic acid, acetic acid, 2-hydroxybenzaldehyde and hydroxyacetone have been considered. Further these reactions are also studied in gas and liquid phase to compare results of different phases, including supercritical water. It was found that while HDO of aromatic compounds like phenol and 2-hydroxybenzaldehyde was favourable in the supercritical phase, smaller molecules like acetic acid and hydroxyacetone did not show much advantage in the supercritical phase over gas and liquid phase. It was also found that the thermochemical parameter - Gibbs free energy change (ΔG) was equally influenced by the solvation effect and the effect of temperature-pressure under supercritical conditions. In several instances, the two effects were found to offset each other in the supercritical phase.

Thermochemical Mapping of Levulinic Acid Conversion to Pentane in Supercritical Water within the Framework of Density Functional Theory

“…are susceptible to the operating parameters. The location of these supercritical conditions on the T–P−ρ plot has been shown in our work …”

“…Therefore, in this study, the authors focus on upgrading levulinic acid to pentane via value-added products using the supercritical water under different conditions. The supercritical phase is simulated using manually defined parameters in an implicit solvation model under density functional theory (DFT) in a manner that has been recently reported by the authors of the same group . The kinetic mapping of the pathways is conducted in the gaseous and aqueous phases along with the supercritical phase for comparison purpose.…”

“…To incorporate the solvation effect, the “universal solvation model based on solute electron density”, or SMD implicit solvation model is used. The modeling method used in this study is based on a previously reported work by Agrawal and Kishore . The SMD model contains an electrostatic component and a nonelectrostatic component.…”

Produzindo Ladrilhos Hidráulicos: Conexões E Experimentações Em Pernambuco E Na Bahia

“…Quando esses fluidos estão presentes 2 com catalisadores ácidos e álcool tem a reação chamada de esterificação em condição supercrítica, como resultados, tem um aumento no poder calorífico e diminuição da viscosidade (PANWAR et al, 2021). A elucidação da utilização dos fluidos supercríticos vem sendo explorada, sendo uma novidade, apresenta grande potencial de utilização (OMAR et al, 2019;DURAK, 2016;AGRAWAL et al, 2020).…”

Kinetic Modeling of Conversion of Levulinic Acid to Valeric Acid in Supercritical Water Using the Density Functional Theory Framework

“…The SMD implicit solvation model 31 was used to incorporate the solvation effects in the study. Agrawal and Kishore 32 have recently described the method used in the study. A total of seven descriptors are used to describe the electrostatic and non-electrostatic component of the solute− solvent system 33 in the SMD model.…”