Synthesis of nano-carbons from different waste plastics and diverse catalysts

Polymers have important and widespread applications in modern materials due to their excellent formability, chemical stability, light weight and low cost. Their production has increased exponentially over the last 60 years after their introduction to the markets from 1.5 million tons/year in 1950 to 322 million tons per year in 2015. Polymeric materials are often discarded after a single use, and post-consumer waste has become a very serious environmental problem, as it is no-biodegradable. Therefore, different recycling, reuse and, even upcycling methods for waste plastics have been investigated. This research aimed at systematically investigating the influence of the types of stainless steel catalysts and their pretreatment on the formation of nanotubes. The targeted polymer feedstocks were post-consumer polyethylene (PE), polyethylene terephthalate (PETE), polypropylene (PP) and polystyrene (PS) as pellets, clippings or powders. The polymers were pyrolyzed in an inert nitrogen atmosphere in an electrically heated furnace kept at 800 °C. Their effluent gases from this furnace, containing the gaseous pyrolyzates of the polymers, were then channeled to a separate electrically-heated furnace, were the catalyst substrates were heated to 800 °C. Therein synthesis of carbon nanotubes took place by chemical vapor deposition (CVD) in nitrogen. The catalytic substrates used for the nanoparticle growth were T304, T316, and T316L stainless steel meshes. The substrates were used as received, or pretreated by acid wash and/or heat-treated in air or in nitrogen at 800 °C. The produced nanomaterials were characterized by the use of SEM and TEM.