A comparative study on evolution characteristics of organic functional groups and gases during low-rank coal pyrolysis in N₂ and H₂ atmospheres

Coal hydropyrolysis is a promising conversion pathway, but its relationship with the evolution of organic functional groups and gases remains inadequately understood. Fitting the Fourier transform infrared (FTIR) spectra of the solid products reveals that the H₂ atmosphere promotes the devolatilization of phenolic hydroxyl groups, but the variation of carboxyl content is unaffected by the H₂ atmosphere. Real-time analysis of the volatiles by TG-FTIR shows that the reverse water-gas shift reaction is inhibited in the H₂ atmosphere, increasing the CO₂ yield. Gas chromatography analysis of the gaseous products indicates that the H₂ yield increases rapidly after temperature exceeding 650 °C, giving the volatiles significant reducing capabilities. However, the H₂ yield slightly decreases in the H₂ atmosphere. Using model-free kinetic methods, it is found that the H₂ atmosphere reduces the activation energy, energy required, and coal reactivity during the pyrolysis process.