(291b) Reaction Paths Predicted for Xylose and Xylan Pyrolysis Chemistry Using Reactive Molecular Dynamics

Our approach to understanding the pyrolysis of xylan, a component of hemicellulose, is to use Reactive Molecular Dynamics simulations as implemented in LAMMPS/ReaxFF [1,2,3]. Initial results show how we have inferred reaction pathways, study product yields as functions of temperature, and evaluated accuracy of the LAMMPS predictions.

Calculations were performed on an isothermal-isobaric system of β-D-xylopyranose at conditions to emulate a Pyroprobe-GCxGC/TOFMS experiment in this lab. The most frequent reaction events predicted by the simulations were used as bases for transition-state searches with computational quantum chemistry. In parallel, products predicted by the simulations were compared to experimental product distributions.

Products observed in the Pyroprobe-GCxGC/TOFMS experiment that have also been detected in ReaxFF MD calculations include glyceraldehyde, D-xylose, and glyoxal. NPT ReaxFF MD calculations also produced ethene-1,2-diol, (E)-3-hydroxyacrylaldehyde, and (2R,3S,4R)-3,4-dihydroxytetrahydrofuran-2-carbaldehyde that are structurally similar to the major products glycolaldehyde, 1-hydroxypropan-2-one, and furfural.

In this talk, we will propose pathways that are suggested by these findings, reviewing the information that support these hypotheses. Future work will include modeling of xylan oligomers at condensed-phase densities using NPT Reactive Molecular Dynamics through LAMMPS/ReaxFF, including temperature effects.

References:

[1] S. Plimpton, "Fast Parallel Algorithms for Short-Range Molecular Dynamics," J Comp Phys, vol. 117, pp. 1–19, 1995. https://lammps.sandia.gov/

[2] A. C. T. van Duin, W. A. Goddard, and K. Chenoweth, "ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation," J. Phys. Chem. A, vol. 112, no. 5, pp. 1040–1053, 2008.

[3] S. A. Pandit, A. C. T. van Duin, A. Y. Grama, and H. M. Aktulga, "Parallel Reactive Molecular Dynamics: Numerical Methods and Algorithmic Techniques," Parallel Computing, vol. 38, no. 245–259, 2012.