Molecular dynamic investigation on hydrogen production by polycyclic aromatic hydrocarbon gasification in supercritical water

• Method combining ReaxFF with DFT is utilized to investigate SCWG of PAH.
• SCWG process of PAH is compared with steam gasification and pyrolysis.
• SCW decreases the energy barrier of the ring-opening reaction by 558.22 kJ/mol.
• SCW accelerates the gasification rate and also increases the hydrogen yield.
• H radical-rich water clusters contribute to the main source for the H2 production.

The decomposition of polycyclic aromatic hydrocarbon (PAH) is the rate-determining step for coal gasification in supercritical water (SCW). Anthracene, which is the simplest PAH, was selected as the model compound to investigate the gasification characteristics. The reactive force field method combined with the method of density functional theory was utilised to investigate the SCW gasification process of anthracene, and the process was also compared with steam gasification and pyrolysis. Compared with pyrolysis, SCW effectively weakened the C(ring)-C(ring) bond energy in anthracene and decreased the energy barrier of the ring-opening reaction by 558.22 kJ/mol. The effect of SCW on the anthracene gasification was revealed. This effect proved that supercritical water accelerated the gasification rate and increased the hydrogen yield. The SCW molecule was converted into H radical-rich water clusters, which contributed to the main source of H2 production.