Microwave-assisted pyrolysis of oily sludge from offshore oilfield for recovery of high-quality products.

Microwave pyrolysis of oily sludge (OS) was investigated in this study. In this case, the highest oil yield (85.93 wt%) was achieved at 500 °C. The molar ratio of H/C was lower for OS char (OC) at higher pyrolysis temperatures, indicating good stability of OC owing to high degree of carbonization and aromaticity. Then, iodine adsorption value of OC reached maximum (531.2 mg/g) at 750 °C. While methylene blue (MB) uptake slightly increased with temperature and reached maximum (384.08 mg/g) at 850 °C. In order to improve the quality of pyrolysis products, different catalysts were employed in OS pyrolysis. The maximum content (64.31%) of aromatic hydrocarbon was found in PO500-10β. In addition, β-zeolite also reduced oxygenates content in oil, beneficial for stability of oil products. The gas products from catalytic pyrolysis were abundant in CO and CH, and KOH achieved the highest CO (5.9 wt%), CH (16.9 wt%) and H (2.4 wt%) yields. Finally, a reaction mechanism pathway for OS pyrolysis was proposed to show the production routes of gas, liquid, and solid products.