Self-Combustion–Depolymerization Approach to Activate Solid-Waste Coal Gangue Minerals for Fluid Catalytic Cracking Catalyst Synthesis

Globally, exploring efficient utilization technologies for coal gangue, a notorious hazardous solid waste, is one of the most important issues among current sustainable development topics. Herein, a green and energy-efficient self-combustion–depolymerization (SCD) approach is proposed to activate coal gangue into highly reactive silica and alumina species for fluid catalytic cracking (FCC) catalyst synthesis. Starting from microspherical precursors composed of SCD-activated coal gangue, FCC catalysts (SCD-Y) bearing in situ-generated Y zeolites with a relative crystallinity of ca. 50% can be readily fabricated via hydrothermal synthesis. SCD-Y shows much higher catalytic activities toward heavy oil cracking than conventional catalysts. The improved performances could be ascribed to the higher accessibility of active sites and better diffusion properties of the hierarchical structure. Remarkably, compared to the conventional method, the energy consumption corresponding to material input (Em) and the total manufacturing process (Etot) of this SCD route falls by 46.8 and 33.5%, respectively.