Computational studies of water and carbon dioxide interactions with cellobiose

Abstract

B3LYP/6-311++G** with dispersion correction (DFT-D) was used to study local and global minimum energy structures of water (H2O) or carbon dioxide (CO2) bonding with a pair of cellobiose molecules. The calculations showed that neither the H2O nor the CO2 prefer to be between the cellobiose molecules, and that the minimum energy structures occur when these molecules bond to the outer surface of the cellobiose pair. The calculations also showed that the low energy structures have a larger number of inter-cellobiose hydrogen bonds than the high energy structures. These results indicate that penetration of H2O or CO2 between adjacent cellobiose pairs, which would assist steam or supercritical CO2 (SC-CO2) explosion of cellulose, is not energetically favored. Comparison of the energies obtained with DFT-D and DFT (the same method but without dispersion correction) show that both hydrogen bonds and van der Waals interactions play an important role in cellobiose-cellobiose interactions.

Changes in the hygroscopic behavior of cellulose due to variations in relative humidity

“…This limit, at approximately 70 % RH or 10 % EMC, is also where water diffusion has been shown to increase strongly (Kulasinski et al 2014;Topgaard and Söderman 2001;Zografi and Kontny 1986). Prior to this RH, specific sorption and water clustering around polar or charged groups (Bazooyar et al 2015;Belbekhouche et al 2011;Berthold et al 1996;Cohan 1938;Kulasinski et al 2017;Maurer et al 2013;Newns 1973;Olsson and Salmén 2004) or a more tortuous diffusion path between the fibrils (Topgaard and Söderman, 2001) might slow down water mobility. The clustering and specific adsorption may sterically hinder water adsorption to nearby sites until there is sufficient water to create a percolating network through the sample (Kulasinski et al 2014).…”

“…The CO 2 treatment may also cause surface molecule reorientation (Johansson et al 2011) due to the low-polar nature of the treatment. Additionally, the treatment has been previously shown to cause changes in the molecular distances on the cellobiose unit level when compared to interactions with water (Bazooyar et al 2015).…”

Understanding Plant Biomass via Computational Modeling

“…[ 49,81 ] A good example for the type of insights that can be derived from this method is that DFT calculations revealed the important contributions of the vdW dispersion force and H‐bond to the interactions between cellulose stacks for forming the crystal structure. [ 82,83 ] However, the results from DFT with different functionals and corrections can vary a lot. [ 49,81 ] With numerous functionals existing, the ones have been applied to cellulose include B3LYP, BLYP, B3PW, mPW1PW91, RPBE, DFT‐D2 (or PBE‐D2), and so on.…”

“…However, classical DFT methods had the problem of underestimating H‐bond and vdW energies. [ 81,83 ] General gradient‐corrected approximations (GGA) such as BLYP were not able to properly treat weakly interacting systems. [ 82 ] B3LYP functional with diffuse and polarization corrections can result in accurate relative energies and structures of hydroxyl‐containing compounds.…”

“…[ 82 ] B3LYP functional with diffuse and polarization corrections can result in accurate relative energies and structures of hydroxyl‐containing compounds. [ 83 ]…”