EFFECT OF REACTION PARAMETERS AND CATALYST TYPE ON WASTE PLASTICS LIQUEFACTION AND COPROCESSING WITH COAL

The effect of reaction conditions and catalyst type on the liquefactio n behavior of model waste plastics and on the coprocessing of model wa ste plastics with coal was evaluated. Individual model plastics and mi xtures of these plastics were catalytically reacted at temperatures of 400 to 440 degrees C with an initial H-2 pressure of 5.6 MPa using fl uid catalytic cracking catalysts and a zeolite HZSM-5. Higher conversi ons to tetrahydrofuran-soluble material were achieved in the reactions of individual model plastics than in the reaction with various mixtur es of model plastics, while higher hexane soluble yields and lower gas yields were obtained with the mixtures. A base plastics mixture compo sed of 50% high density polyethylene (HDPE), 30% polyethylene terephth alate (PET), and 20% polystyrene (PS) was used to evaluate the effect of reaction time and initial H-2 pressure on the conversions and produ ct distributions achieved. Reaction times of 120 min produced high and similar conversions and product distributions from HZSM-5 and two flu id catalytic cracking catalysts; however, the differences in the three catalysts' activities were much larger for converting the plastics at shorter reaction times of 30 and 60 min. The highest conversion of th e base plastics mixture occurred when the initial H-2 pressure was low . Addition of aromatic, hydroaromatic, cycloalkane, and straight chain aliphatic solvents to the base plastics mixture influenced the conver sion and product distribution obtained. For all three catalysts, the s traight chain aliphatic solvents were the most effective for solvating the cracked polymer products and promoting higher conversions. Coproc essing reactions of the base plastics mixture with coal yielded the hi ghest conversion when they were reacted catalytically without a solven t. Introduction of a solvent required higher severity conditions to ac hieve equivalent conversions as reactions without solvent.