Study on interaction between coal and model plastics during liquid-phase catalytic coliquefaction

Coliquefaction of Tanitoharum coal with PP, PS, high-density PE was carried out using red mud plus sulfur as the catalyst, at 430°C for 60 min under 7 MPa inital pressure of hydrogen. There existed almost linear relationship of coal concentration in coal/plastics mixture with conversion to THF-soluble (THFS) or oil yield for the mixture of coal/PP, coal/PS or coal/PE in case of tetralin. Observed oil yield at 75 % of coal concentration for any coal/plastics mixture was slightly larger than that calculated. The use of decalin gave lower values of conversion, yields of THFS in VR and oil, particularly at coal concentration of 75% for the coal/PE mixture, compared to those calculated, while a similar tendency as to interaction in respect of conversion, yields of THFS in VR, oil, and gas was observed for the mixture of coal/PP and coal/PS. However, when the coal was reacted with mixed plastics of PP, PS and PE at coal concentration of 50 %, the interaction observed for the coal/PE mixture disappeared, and higher oil yield than that calculated was obtained. The results suggested interaction between PE and the other plastics (PP, PS) is larger than that between coal and PE. It is also suggested from the results for the coal/PP mixture that radicals from PP cracking was used for stabilization of radicals from the coal and PP, instead of hydrogen donated from gas and solvent. Higher values of conversion and oil yield for the use of decalin were obtained, compared to tetralin. The results indicated that a good hydrogen donor solvent would not be necessary in case of the use of catalyst for coliquefaction of coal with waste plastics.