| Coprocessing of waste plastics with coal was investigated using Mo and Fe naphthenate, mineral clays, carbon black and zeolitic catalysts. Reactions were performed with plastics including polyisoprene, polystyrene (PS), polyethylene terephthalate (PET), polyprene (PP), polyethylene (HDPE and LDPE), commingled waste plastics and European commingled waste plastics and with coal alone or coprocessed in the presence and absence of a hydrogen donor solvent and catalysts at 400 to 440{dollar}spcirc{dollar}C and of an initial H{dollar}sb2{dollar} pressure 2.6 to 7.8 MPa.; Polyisoprene and PS liquefied readily at these conditions; however, neither HDPE nor LDPE converted much. After pretreatment, the zeolytic catalysts showed high activity for converting polyethylenes at 440{dollar}spcirc{dollar}C with an initial H{dollar}sb2{dollar} pressure of 5.6 MPa. HZSM-5 was the most effective catalyst for converting both coprocessing systems although more gaseous products were produced than with the fluid cracking catalysts.; The effect of reaction conditions, and catalyst and solvent type on the liquefaction behavior of plastics and on the coprocessing of plastics with coal was also evaluated. Longer reaction time produced higher conversions and product distributions from HZSM-5 and two fluid cracking catalysts. For all three zeolitic catalysts, the straight chain aliphatic solvents were the most effective for solvating the cracked polymer products and promoting higher conversions, while tetralin, a typical hydrogen donor coal solvent proved detrimental to plastics liquefaction.; The chemical incompatibility and then catalytic inconsistency of plastics and coal suggested that separate processing of them under different reaction conditions using different catalysts could optimally utilize both materials; therefore, a two-step process was investigated in this research. In the first step, waste plastics were reacted at a relatively high temperature and low hydrogen pressure, using FCC and zeolite catalysts. The liquid product from the first step was used as solvent for the coal liquefaction reaction in the second step. Coal was liquefied at a lower reaction temperature and higher hydrogen pressure, and molybdenum or iron naphthenate catalyst precursor was used in the second stage. Thus the reaction conditions and the catalysts were optimized for each step, and both types of materials were more effectively utilized than in a single step coprocessing system. |
