Newsletter - Aachener Verfahrenstechnik - RWTH Aachen University

Molecular Simulations and Transformations
Research in Tailor-Made Fuels from Biomass
As part of the Tailor-Made Fuels from Biomass
Cluster of Excellence, we perform molecular simulations
on components of interest in the biofuel
production process, with a focus on materials
involved in the synthesis of novel fuels from
biomass, ranging from cellulosic precursors to
intermediate “platform chemicals” to the final fuel
candidates.
Research on the behavior of intermediate compounds,
such as methylsuccinic acid (MSA) and
methyltetrahydrofuran, in ionic liquids and in
water, suggests that the chemical structure of
the platform chemicals has a strong correlation
with their behavior in solution. For instance,
in [BMIM]Cl, methylbutanediol forms relatively
small clusters, with only a few interconnecting
Cl atoms in between the monomers. By contrast,
placed in the same medium, MSA forms
extended “chains” containing tens of monomers
with Cl atoms acting as “bridges” in the interstitial
space between adjacent molecules. Having
successfully probed the interactions of platform
chemicals, we are now extending this work to include
the study of the interaction of small cellulose
“bundles” that mimic the dissolution behavior
of a miniature cellulose “crystal” placed in ionic
liquid.
Other collaborative efforts as part of the TMFB
program include an ongoing effort with the group
of Prof. Kai Leonhard (LTT) to study the connections
between the COSMO-RS method, which
uses combinatorial approaches combined with
quantum chemical calculations to predict molecular
properties, with molecular simulations.
Preliminary results suggest that the accuracy of
COSMO-RS predictions are directly related to
the nature of charge distributions within the molecule:
nonpolar molecules, or molecules with
weak charge distributions, usually agree well
with experiment, while “densely”-charged chemicals
offer poorer agreement.
Fig.13: Local water environment around a 3-
MTHF molecule, as revealed by molecular
dynamics simulations.
Research in the AICES Graduate School
Two new projects were started at the AICES Graduate
School during 2011. as two new AICES
fellows joined the MST group.
The first project involves the study of molecular
structure and dynamics at interfaces. Current
methodologies for analyzing these systems relies
on force fields that are characterized primarily
for bulk phases. As a result, interactions that
take place across interfaces – such as wetting,
penetration, dissolution, and solvation – are frequently
inaccurate, and in many cases simulation
results contradict directly with experimental
observations. By using improved and more accurate
methodologies for handling and parameterizing
interfacial interactions, we will provide better
predictions for the important area of multiphase
processes.
In collaboration with the research group of Dr.
Roger Sauer (AICES), we are also examining
the interactions between contact mechanics and
molecular dynamics. Contact between surfaces
is inherently a multiscale process, as atomiclevel
interactions between charges is also balanced
by nano-, micro- and mesoscopic material
properties such as surface roughness.
15 Molecular Simulations and Transformations The AVT Newsletter