Study on surface functional group characteristics of Yanzhou coal for thermal maturity

To reveal the changing rule of coal structure during coal gasification, Yanzhou coal was used to make raw coal char, acid‐washed coal char and semi‐cokes in tube furnace at different temperatures, 300–1000 °C, and the infrared spectra were monitored by Fourier transform infrared spectroscopy at every gasification conditions, to analyze the surface functional group characteristics of Yanzhou coal. It was found that the absorption peaks of NH group, as well as free SH and SiO groups, of raw coal were removed during acid‐washing; char‐making temperature had influence on organic groups of raw coal greatly, but little on SiO groups and organic sulfur groups; the function of heating rate was activated only when the temperature reaches a certain role, and heating rate was selective on the characteristic group formation; for semi‐cokes, limited aliphatic structure in coal led to small hydrocarbon generation capacity during coal gasification at low temperature, but the synergistic effect of aromatic structure cracking and condensation increases the hydrogen‐enriched degree of semi‐cokes at high temperature; aliphatic and aromatic structures were affected little by low temperature, and the original aliphatic structure broke off firstly with increasing temperature, whereas at high temperature, aromatic structure began to crack to aliphatic structure to break off gradually; CO 2 participating in gasification, intervening CO group of phenols, ethers, alcohols and esters could influence the total oxygen‐enriched efficiency of semi‐cokes. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.