Feedstock recycling of agriculture plastic film wastes by catalytic cracking

摘要

Feedstock recycling by catalytic creacking of a real plastic film waste form Almeria greenhouses (Spain)towards valuable hydorcarbon mixturs has been studied over several acid ctalysts.The plastic film waste was mostly made up of ambient degraded low-density polyethylene (LDPE)and ethylene-vinyl acetate (EVA)copolymer,the vinyl acetate content being around 4wt.(percetn).nanocrystalline HZSM-5 zeolite (crystal size approx 60nm)was the only catalyst capable of degrading comletely the refuse at 420 deg C despite using a very small amount of catalyst (plastic/catalyst mass ratio fo 50).However,mesoporous catalysts(Al-SBA-15 and Al-MCM-41),unlike it occurred with virgin LDPE,showed fairly close conversions to that of thermal cracking.nanocrystaline HZSm-5zeolite led to 60 wt.(percetn)selectivity towards C_1-C_5 hydrocarbons,mostly valuable C_3-C-5 olefins,what would improve th eprofiltability of a future industrial recycling process.The remarkable performance of nanocrystalline HZSM-5 zeolite was ascribed to its high content of strong external acid sites due to its nanometer dimension,which are very active for the cracking of bulky macromolecules.hence,nanocrystalline HZSM-5 can be regarded as a promising catalyst for a feasible feedstock recycling process by ctalytic cracking.