Influence of operating variables on solid carbons obtained by low-density polyethylene pyrolysis in a semicontinuous fast heating quartz reactor

Low-density polyethylene (LDPE) was pyrolyzed in aquartz semicontinuous feed reactor with fast heating to obtain solid carbons. Two different carbons were obtained by pyrolysis: pyrolytic carbon deposited on the wall of the reactor and spherical carbon from gas-phase nucleation and growth in the inner part of the reactor. The spherical carbon constituted the major portion of the solid carbon product (95%-99%). A two-factorial experimental design was used to study the influence of pyrolysis variables (temperature, nitrogen flow rate, and LDPE feed rate) on morphology, solid carbon yield, and structure. The yield of LDPE to solid carbon was high (15.3%-49.4%) and increased as the temperature and residence time each increased. Solid carbons with more homogeneous morphology and a higher degree of structural order were obtained at higher temperatures as well as lower nitrogen flow rates and lower LDPE feed rates (both leading to a higher residence time of pyrolytic gases).