Thermal and catalytic coprocessing of Illinois No. 6. coal with model and commingled waste plastics

Abstract

Coprocessing of waste plastics with coal was investigated at reaction conditions typical of direct liquefaction using slurry phase Mo and Fe hydrogenation catalysts. Reactions were performed with individual model polymers including polyisoprene, polystyrene, and high and low density polyethylene (HDPE, LDPE), and with coal alone in the presence and absence of a hydrogen donor solvent and catalysts at 400 °C and of an initial H 2 pressure of 5.6 MPa. Polyisoprene and polystyrene liquefied readily at these conditions; however, neither HDPE nor LDPE liquefied much with these catalysts or conditions. The conversion to THF solubles and product distributions from coprocessing reactions with coal and each polymer performed at the same reaction conditions were compared to those obtained with individual polymers. The coprocessing reactions with polyisoprene and polystyrene yielded thermal and catalytic conversions in the range of 62.3 to 95.5% while the coprocessing reactions with HDPE or LDPE yielded low conversion in the range of 20.2 to 43.2%. Catalytic reactions using carbon black, minerals, and fluid catalytic cracking catalysts were performed with HDPE and LDPE to evaluate their effect on conversion. After pretreatment, the fluid catalytic cracking catalysts showed activity for converting LDPE at 440 °C with an initial H 2 pressure of 5.6 MPa. Subsequent coprocessing reactions of LDPE and coal and commingled plastics and coal were performed with four fluid catalytic cracking catalysts and a zeolite HZSM-5. HZSM-5 was the most effective catalyst for converting both coprocessing systems although more gaseous products were produced than with the fluid catalytic cracking catalysts. The coprocessing reactions with commingled plastics, which consisted primarily of HDPE with some polypropylene, and coal yielded less conversion and less hexane-soluble materials than the LDPE coprocessing system.