Co-liquefaction of coal and polypropylene or polystyrene in hot compressed water at 360–430 °C

The co-liquefaction of coal and polypropylene or polystyrene in hot compressed water was carried out in a 50 mL batch stainless steel autoclave reactor. The effects of the polymer ratios by weight (10–40%), reaction temperatures (360–430 °C), and reaction time (30–120 min) were investigated. The main products were analyzed qualitatively by Fourier transform infrared spectroscopy and high-performance liquid chromatography. The results showed that the synergistic effect was demonstrated and the polymer stimulated coal liquefaction as a hydrogen donor during co-liquefaction in hot compressed water. The reaction temperature was the critical factor because the process of oil and gas generating by hydro-cracking, ring-opening and hydrogenation clearly occurred above 400 °C and the conversion and yield of oil and gas reached a maximum of 75.92% and 69.11% at 420 °C, respectively. The phase behavior during co-liquefaction in a fused-silica capillary reactor was recorded by a microscope during the heating and cooling processes, demonstrating that polypropylene melted to form a liquid phase as the reaction medium and hydrogen donor during co-liquefaction.