Microwave-Assisted Upcycling of Coke Wastes from a Pilot-Scale Biomass Pyrolysis System: Method Optimization and Mechanism Insights

Abstract

Coke waste accumulation in biomass pyrolysis systems poses significant operational and environmental challenges, disrupting production and limiting renewable energy scalability. This study introduces a self-catalyzed microwave pyrolysis method to valorize coke waste from a pilot-scale biomass pyrolysis system, aiming to produce high-value carbon nanotubes (CNTs) and synthesis gas. Comprehensive analysis of coke samples from various pipeline locations revealed notable structural and chemical differences, which in turn influenced their microwave absorption and reactivity. Experimental results showed that optimized microwave heating and blending ratio significantly enhances the selectivity of CNTs and H2. Isothermal kinetic modeling confirmed a strong correlation with a first-order reaction model, with an activation energy of 11.173 kJ/mol. Furthermore, the CNTs exhibited outstanding electrocatalytic performance, reaching an onset potential of 0.85 V vs. RHE in the oxygen reduction reaction (ORR), comparable to commercial Pt/C catalysts. These findings indicate that microwave-assisted pyrolysis can be effectively integrated into renewable energy systems for biomass waste management, offering insights to advance industrial-scale energy production.

Keywords: Biomass pyrolysis, Coke waste disposal, Pipe coking mechanism, Microwave-assisted catalytic pyrolysis.