NH3 assisted catalytic pyrolysis of low-grade fuel oil with energy self-supply to acquire high-quality products

The petroleum industry and pyrolysis of organic solid waste produce a large amount of low-grade fuel oil characterized by high proportions of heavy fractions, unsaturated compounds, and oxygen content. Catalytic hydro-pyrolysis is an effective approach to improve the quality with co-production of valuable pyrolysis gases and high-grade pyrolysis oils. However, exploration of available and low-cost hydrogen donors is the determining factor for the feasibility of this technique. Given that NH3 is the excellent hydrogen carrier and with an active molecular structure, this work innovatively proposed NH3 assisted catalytic pyrolysis that could significantly promote hydrogenation and cleavage reactions to acquire high-quality products and efficient utilization of NH3 energy. HZSM-5 with specific modification by desilicication and phosphorus loading was selected as the optimal catalyst. The abundant hierarchical pore structure and weak acidity mainly contributed to the excellent catalytic performance. Specifically, 3 + rings aromatics (≥3 rings) disappeared, long-chain alkanes decreased by 10.45 %, while short-chain alkanes increased from 0 to 42.05 % for HO pyrolysis at 550 °C. The stability and universality of this approach were respectively investigated. Meanwhile, the heat value of pyrolysis gas increased by 3766 times under the optimal condition mainly due to the distinctly high yield of C2-C4 combustible hydrocarbons, ca. 429.22 mL/g-oil. Accordingly, the pyrolysis gas could reach the target of energy self-supply for pyrolysis process by in-situ combustion with the residual NH3. Additionally, simulation calculations demonstrated that co-combustion of NH3 and pyrolysis gases increased the laminar burning velocity and enhanced the combustion efficiency of NH3. Approximately 37,675 kJ/kg-oil energy could be produced in gas during NH3 assisted catalytic pyrolysis to provide sufficient heat in pyrolysis with zero natural gas input. Extremely low production of CO2, zero natural gas input, and abundant C2-C4 hydrocarbons jointly promoted the negative carbon effect, ca. 948.65 L CO2-eq./kg-oil. This study aims to propose NH3 as a hydrogen donor so that low-grade fuel oil can be upgraded with energy self-supply.