Production of aromatic-rich oil from marine oily sludge via in situ catalytic pyrolysis using coal gangue

To explore the collaborative disposal and resource utilization of marine oily sludge (MOS), the effects of coal gangue (CG) on the pyrolysis characteristics and product distribution of MOS were studied by employing a fixed-bed reactor and thermogravimetric analysis. The results indicated that catalytic pyrolysis significantly increased the yield of oil and gas products. The catalytic pyrolysis at 900 °C resulted in oil and gas yields of 29.09 wt% and 35.18 wt%, among which the yield and selectivity of aromatics in pyrolysis oil were 28.74 wt% and 98.79 %, respectively, and H2 content in pyrolysis gas was 46.93 vol%. Catalytic pyrolysis promoted the reduction of heteroatomic compounds in pyrolysis oil. The highest yields of CH4, CO, and H2 were 140.63 g/kg, 147.75 g/kg, and 22.32 g/kg, respectively. The sequential temperature responses of functional groups in pyrolysis oil and char were investigated using two-dimensional correlation infrared spectroscopy, indicating that esters/ethers and aliphatic exhibited earlier responses in catalytic pyrolysis oil and char, respectively. These results demonstrated the synergistic effects between CG and MOS. The concentrations of heavy metals (HMs) in pyrolysis char met the standard requirements. The highest potential ecological risk factor (Er) for a single HM in the pyrolysis char was 5.61 (i.e., Ni), and the comprehensive potential ecological risk index (RI) of pyrolysis char reached the highest value of 10.23, much lower than 40 (Er) and 50 (RI), demonstrating low ecological risk. This study provides new insight into the efficient resource utilization of MOS and serves as a reference for catalyst function of CG, and fills the gap in the cooperative disposal and resource utilization of oily sludge and coal gangue.