A large number of studies have been devoted to solving the problems of accumulation and recycling of polymer waste, but to date there are no generally accepted effective and economically feasible technologies for chemical processing of secondary polyolefins into demanded products. This paper presents the results of experimental studies on the processing of polyethylene and polypropylene waste by soft pyrolysis for depolymerization and obtaining substances that can improve the low-temperature properties of medium and heavy fuels. Pyrolysis of stretch film, containers, packaging was carried out in a stainless steel reactor at temperatures of 380-660°C for 3 hours. The yield of liquid pyrolysis products was 42-86% wt. for polyethylene and from 61-81% wt. for polypropylene. The remainder was no more than 0.2% wt., the rest is hydrocarbon-containing gas. The condensed pyrolysis products were determined in terms of density, pour point, average molecular weight, composition and structure depending on the pyrolysis temperature by IR spectroscopy. It is shown that addition of 125-250 ppm of pyrolysis polyethylene, polypropylene to heavy diesel fuel allows to reduce its pour temperature by 22-28°C, while no significant effect on viscosity and the value of the cold filter plugging point is observed. At addition of pyrolysis products to fuel oil in concentration up to 1% wt. no depressor effect was revealed. Thus, pyrolysis products of polyolefins due to branched structure and relatively high molecular weight can prevent aggregation of paraffin crystals in middle distillate oil products, which do not have requirements for the cold filter plugging point, and can be potentially used as a depressor additive.
VILDYAIKIN et al. (2023) studied this question.