Theoretical Insights on the Fragmentation of Cellulosic Oligomers to Form Hydroxyacetone and Hydroxyacetaldehyde

Abstract

The presence of heavy unknown oligomeric sugar products in bio-oil is evidenced in experimental results reported in the literature. In this paper, we study the fragmentation reactions yielding hydroxyacetone and hydroxyacetaldehyde from oligomeric sugars following previous work on dehydration reactions to propose structures of these oligomers. Hydroxyacetone and hydroxyacetaldehyde are primary products of cellulose fast pyrolysis, but the fragmentation reaction mechanism of these compounds from oligomers merits further study. The density functional theory approach was employed to study this reaction. Results revealed that hydroxyacetone and hydroxyacetaldehyde fragments are more favorably removed from the nonreducing end based on their thermodynamic stabilities. As a result of this study, we proposed new potential structures of unknown oligomeric sugars. Theoretical FTIR and NMR spectra were calculated so that in the future when these molecules are separated their experimental spectra and the theoretical ones herein reported can be used to confirm the structures of these oligomeric sugars. Also, the thermodynamics and physical properties of these compounds were estimated by using the group contribution method. These properties are essential in the design of technologies for bio-oil refining.

Estimation of Fuel Properties for the Heavy Fraction of Biomass Pyrolysis Oil Consisting of Proposed Structures for Pyrolytic Lignin and Humins

“…Estimates for fuel properties provided herein are based on empirical correlations from structural features of molecules and/or subsequent indirect correlations estimating the value of one property based on the value of others. In general, results from regularized regression presented here correspond well with computational structure analyses and property estimation work recently published by Garcia-Perez and associates [18,[81][82][83]. However, as in prior work on solubility parameters [43], the advantage of regularized regression for property estimation is the ability to use unified, simpler models rather than relying on several (potentially disparate) group contribution methods.…”