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Conversion of plastic waste into transportation fuels over bifunctional catalysts was systematically studied. Previous work showed that some acid catalysts were active for degradation of pure polyolefins, but they were easily deactivated by nitrogen, sulfur, and impurities contained in actual postconsumer plastic waste. Ni and NiMo sulfides loaded on a hybrid support (HSiAl), a mixture of HZSM-5 and silica−alumina, were found to be effective for converting both pure high-density polyethylene and plastic waste to gasoline-range products. Hydrocracking reactions were carried out mostly at 375 °C, 1000 psig H2 (initial), for a reaction time of 1 h, though the effects of initial hydrogen pressure and reaction time were also examined. Ni/HSiAl had higher hydrocracking and hydroisomerization ability than did NiMo/HSiAl. The quality of liquid products obtained over Ni/HSiAl was comparable to that of a commercial premium gasoline. Moreover, being resistant to poisoning by N- and S-containing compounds, these catalysts could be regenerated simply by recalcination and resulfiding.

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