Papari Sadegh, Bamdad Hanieh, Berruti Franco
Department of Chemical and Biochemical Engineering, Institute for Chemicals and Fuels from Alternative Resources (ICFAR), Western University, London, ON N6A 3K7, Canada.
Materials (Basel). 2021 May 16;14(10):2586. doi: 10.3390/ma14102586.
Plastic production has been rapidly growing across the world and, at the end of their use, many of the plastic products become waste disposed of in landfills or dispersed, causing serious environmental and health issues. From a sustainability point of view, the conversion of plastic waste to fuels or, better yet, to individual monomers, leads to a much greener waste management compared to landfill disposal. In this paper, we systematically review the potential of pyrolysis as an effective thermochemical conversion method for the valorization of plastic waste. Different pyrolysis types, along with the influence of operating conditions, e.g., catalyst types, temperature, vapor residence time, and plastic waste types, on yields, quality, and applications of the cracking plastic products are discussed. The quality of pyrolysis plastic oil, before and after upgrading, is compared to conventional diesel fuel. Plastic oil yields as high as 95 wt.% can be achieved through slow pyrolysis. Plastic oil has a heating value approximately equivalent to that of diesel fuel, i.e., 45 MJ/kg, no sulfur, a very low water and ash content, and an almost neutral pH, making it a promising alternative to conventional petroleum-based fuels. This oil, as-is or after minor modifications, can be readily used in conventional diesel engines. Fast pyrolysis mainly produces wax rather than oil. However, in the presence of a suitable catalyst, waxy products further crack into oil. Wax is an intermediate feedstock and can be used in fluid catalytic cracking (FCC) units to produce fuel or other valuable petrochemical products. Flash pyrolysis of plastic waste, performed at high temperatures, i.e., near 1000 °C, and with very short vapor residence times, i.e., less than 250 ms, can recover up to 50 wt.% ethylene monomers from polyethylene waste. Alternatively, pyrolytic conversion of plastic waste to olefins can be performed in two stages, with the conversion of plastic waste to plastic oil, followed by thermal cracking of oil to monomers in a second stage. The conversion of plastic waste to carbon nanotubes, representing a higher-value product than fuel, is also discussed in detail. The results indicate that up to 25 wt.% of waste plastic can be converted into carbon nanotubes.
全球塑料产量一直在迅速增长，许多塑料制品在使用结束后成为垃圾，被丢弃在垃圾填埋场或四处散落，引发了严重的环境和健康问题。从可持续发展的角度来看，将塑料垃圾转化为燃料，或者更好的是转化为单个单体，与填埋处理相比，能实现更绿色的废物管理。在本文中，我们系统地综述了热解作为一种有效的热化学转化方法用于塑料垃圾增值利用的潜力。讨论了不同的热解类型，以及操作条件（如催化剂类型、温度、蒸汽停留时间和塑料垃圾类型）对裂解塑料制品的产率、质量和应用的影响。将升级前后的热解塑料油质量与传统柴油燃料进行了比较。通过慢速热解可实现高达95 wt.%的塑料油产率。塑料油的热值约与柴油燃料相当，即45 MJ/kg，无硫，水和灰分含量极低，pH值几乎呈中性，使其成为传统石油基燃料的一个有前景的替代品。这种油原样或经过轻微改性后可直接用于传统柴油发动机。快速热解主要产生蜡而不是油。然而，在合适的催化剂存在下，蜡状产物会进一步裂解成油。蜡是一种中间原料，可用于流化催化裂化（FCC）装置中生产燃料或其他有价值的石化产品。在高温（即接近1000°C）和极短的蒸汽停留时间（即小于250毫秒）下对塑料垃圾进行闪速热解，可从聚乙烯垃圾中回收高达50 wt.%的乙烯单体。或者，塑料垃圾向烯烃的热解转化可分两个阶段进行，首先将塑料垃圾转化为塑料油，然后在第二阶段将油热裂解为单体。还详细讨论了将塑料垃圾转化为比燃料更具价值的产品——碳纳米管。结果表明，高达25 wt.%的废塑料可转化为碳纳米管。
