Catalytic Thermal Cracking of Postconsumer Waste Plastics to Fuels. 2. Pilot-Scale Thermochemical Conversion

摘要

Synthetic gasoline and diesel fuels were prepared via catalytic and noncatalytic pyrolysis of waste polyethylene and polypropylene plastics followed by distillation of plastic crude oils. Reaction conditions optimized using a 2 L batch reactor were applied to pilot-scale production of plastic crude oil from polypropylene. The optimum conditions on the pilot-scale system were a reaction temperature of 500 degrees C and a residence time of 4.7 min. Plastic crude oil yields at pilot scale were comparable to those of the batch scale (70-80%). Plastic crude oils obtained from pyrolysis were distilled into the boiling point range of motor gasoline, diesel no. 1, gas oil, and vacuum gas oil range fractions. The elemental composition of the crude oil and its distillates were similar to the starting plastic material. Fuel properties were studied for both neat and in blends (5% and 20%) with ultralow sulfur diesel fuel (ULSD). Excellent low temperature properties were obtained for some of the samples, as indicated by a pour point of <-74 degrees C and cold filter plugging point (CFPP) of <-50 degrees C. Oxidative stabilities and kinematic viscosities of plastic diesel-range samples were found to be within the limits prescribed in American (ASTM D975) and European (EN 590) petroleum standards, where applicable. In addition, the plastic diesel-range samples yielded greater energy content than ULSD. Three plastic diesel-range samples were selected for further evaluation as blend components in ULSD, as these were determined to have the best combination of fuel properties relative to the other diesel-range samples. The 5 and 20% blends exhibited superior low temperature performance relative to ULSD. In addition, oxidative stability was not negatively affected by blend ratio. All blends provided oxidative stabilities and kinematic viscosities within the ranges specified in the petrodiesel standards. Density decreased slightly and energy content increased with increasing concentration of the plastic diesel-range sample in ULSD. In summary, our results demonstrated that a plastic diesel-range sample prepared from pilot-scale pyrolysis of waste plastics followed by distillation can be used as drop-in or as blend components with ULSD without negatively affecting fuel properties of ULSD.