The role of CS2 in CS2/NMP mixed solvent in weakening the hydrogen bond of OH-N in coal: a DFT investigation
The interaction processes of trace amounts of N-methyl-2-pyrrolidinone (NMP), CS2/NMP (1:1 by volume) and pure NMP solvent with the hydrogen bond of OH center dot center dot center dot N in coal were constructed and simulated by density functional theory methods. The distances and bond orders between the main related atoms, and the hydrogen bond energy of OH center dot center dot center dot N were calculated. The calculated results show that pure NMP solvent does not weaken the hydrogen bond of OH center dot center dot center dot N in coal. However, trace amounts of NMP and CS2/NMP (1:1 by volume) have a strong capacity to weaken the hydrogen bond of OH center dot center dot center dot N in coal. The H2-N3 distances are elongated from 1.87 angstrom to 3.80 angstrom and 3.44 angstrom, the bond orders of H2-N3 all disappear, and the corresponding hydrogen bond energies of OH center dot center dot center dot N in coal decrease from 45.72 kJ mol(-1) to 7.06 and 11.24 kJ mol(-1), respectively. These results show that CS2 added to pure NMP solvent plays an important role in releasing the original capacity of NMP to weaken the hydrogen bond of OH center dot center dot center dot N in coal, in agreement with experimental observations.
cs2 hydrogen bond coal n-methyl-2-pyrrolidinone density functional theory