Value added hydrocarbons obtained by pyrolysis of contaminated waste plastics in horizontal tubular reactor: In situ upgrading of the products by chlorine capture

Abstract

Abstract Municipal plastic waste (mixtures of high-density polyethylene, low-density polyethylene, polypropylene, and polyvinyl chloride) was pyrolyzed in a pilot-scale horizontal tubular reactor. To increase the yield of volatile and to improve the product properties (e.g. reduced chlorine content, better storage and transportation) red mud, calcium hydroxide, and nickel loaded zeolite catalysts were used. The nickel loaded synthetic zeolite catalysts were prepared by wet impregnation. Catalysts with high synthetic zeolite content can increase the yields of light oil roughly by 50%. The char formation was slight under the same used conditions. In case of catalyst free pyrolysis, the gases and light oil contained significant amount of chlorinated hydrocarbons, which can occur further corrosion problems. The stability of light oil was followed by aging test. Slight formations of polymerized compounds from unsaturated hydrocarbons were found after the treating in case of catalytic pyrolysis. However, the total acidic number was moderate-high without catalyst. Regarding the catalysts, the concentration of chlorinated compounds can be drastically reduced in the presence of catalysts. Especially, when high ratios of the red mud and calcium hydroxide were used. Therefore, the total acid number could be also reduced. Higher synthetic zeolite ratio in the catalyst mixture led to favorable hydrocarbon composition of products, e.g. higher concentration of branched compounds or lower C/H ratio.