Co-pyrolysis of oil shale and plastics: Influence of pyrolysis parameters on the product yields

In this study, co-pyrolysis of oil shale with plastic wastes was investigated with the aim to study the product distribution and to identify optimum process conditions for maximizing the oil yield. Experiments were performed in stainless steel autoclave under nitrogen atmosphere. The effects of pyrolysis temperature, heating rate and plastic type on the yields of the products were investigated. Pyrolysis runs were performed using pyrolysis temperatures between 400 and 600 °C with heating rates of 2 to 20 °C/min. Three plastics: high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) were individually co-pyrolyzed with Moroccan oil shale. The results showed that increase the pyrolysis bed temperature from 400 to 500–525 °C resulted in a significant increase in the oil yield, after which temperature the oil yield decreased. It was also observed for both oil shale and oil shale/plastic mixtures that the oil yield was increased as the heating rate was increased from 2 to 10 °C min− 1. Increasing the heating rate up to 20 °C min− 1 caused a slight reduction in the oil yield. The highest oil yield was obtained between 500 and 525 °C pyrolysis temperature with a heating rate of 10 °C min− 1. Existence of interactions between constituents is proved by comparing the result of experimental total conversion and products yields with rationally calculated yields of pure oil shale and polymers from pyrolysis process. The difference between the experimental and calculated values was positive, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual oil shale.

► Co-pyrolysis of oil shale with plastic wastes was investigated with the aim to identify optimum process conditions.
► The effects of pyrolysis temperature, heating rate and plastic type were investigated.
► The highest oil yield was obtained between 500 and 525 °C with 10 °C min–1.
► The difference between the experimental and calculated values was positive.