Oil sludge from an environmentally hazardous pollutant to an efficient source for energy production via thermal/ catalytic pyrolysis routes

Abstract

Oil sludge, a hazardous waste from petroleum operations, poses severe environmental threats when improperly managed. This study presents a comprehensive approach to convert oil sludge into clean fuel gases, mainly liquefied petroleum gas (LPG) and natural gas (NG), using thermal and catalytic pyrolysis. Three nanocomposite catalysts (NiO-MoO3/Al2O3, MgO-MoO3/Al2O3, and MgO-NiO/Al2O3) were synthesized via co-precipitation. The featured characterizations of these three composites were determined using X-ray diffection (XRD), scanning electron microscopy (SEM), BET surface area analysis, energetic Dispersive X-Ray (EDX), and thermal gravimetric analysis (TGA). Textural results showed respective surface area values of 71.2, 204.2, and 213.7 m2/g, observing the highest porosity and thermal stability for MgO-NiO/Al2O3. Thermal pyrolysis (in absence of catalyst) at 300 °C for 1.5 h under pressure (5 bar N2) achieved a maximum oil sludge-to-gas conversion of 53.7 wt%, where (NG)components represented nearly 909 vol% of content in the produced gas. In contrast, catalytic pyrolysis (under similar conditions) could significantly improve the outcomes of oil sludge transformation into energy soutces. The most effective catalyst, MgO-NiO/Al2O3, achieved a conversion wt % of 77.1 and NG concentration of 96 vol% (at 300 °C for 1.5 h under 5 bar N2). On the other side, NiO-MoO3/Al2O3 converted 66 wt% of OS into gases while MgO-MoO3/Al2O3 gave conversion percentage of 64.5, under similar conditions. The noted results confirm that pressurized catalytic pyrolysis, using mesoporous alumina-based nanocomposites, enhances the yield of fuel gases and their quality, proving efficient conversion of oil sludge into high-calorific value and carbon–neutral fuels.