Catalytic Graphitization of Bio-based Carbon Precursors: A Sustainable Process to Produce Bio-graphite

Abstract

The rapid growth of lithium-ion batteries and electric arc furnace steelmaking has led to a sharp increase in global demand for graphite, while conventional natural and synthetic graphite production routes face critical challenges related to resource security, fossil feedstock dependence, high energy consumption, and environmental impact. This thesis investigates sustainable pathways for producing high-quality graphite from renewable bio-based carbon precursors through catalytic graphitization.

Biochar and pyrolysis bio-oil derived from woody biomass were systematically evaluated as carbon precursors. Laboratory scale catalytic graphitization processes were developed to elucidate the influence of precursor type on graphite yield, crystallinity, microstructure, and reaction pathways. Bio-oil was shown to enable superior graphitic ordering through a gas-solid mediated reconstruction mechanism, while biochar provided substantially higher solid carbon yield, making it more suitable for scalable production.

Key operational parameters influencing catalytic graphitization were then systematically investigated, including catalyst compound, catalyst precursor mixing strategy, graphitization temperature, residence time, catalyst loading amount, and catalyst composition. Nitrate based metal salts exhibited better catalytic efficiency compared with metal powders due to improved dispersion, and wet impregnation significantly enhanced graphitic ordering relative to dry mixing. Elevated temperatures and optimized residence times promoted structural reorganization. Hybrid catalyst systems, particularly trimetallic Fe-Ni-Mn catalysts, demonstrated synergistic effects that significantly improved graphitic crystallinity and microstructural development.

To address scalability limitations and environmental concerns associated with metal salt catalysts, a novel molten metal pool based catalytic graphitization process was developed. Inspired by laboratory observations of a density driven phase separation between molten iron and graphitized carbon, this previously unreported process enables direct high temperature separation of graphite from catalyst without purification. Pilot scale experiments demonstrated semi-continuous production of highly ordered graphite with a minimal residual metal content.

The applicability of the produced bio-graphite was validated in two strategically important applications. In electric arc furnace electrodes, bio-graphite exhibited low electrical resistivity and effective metal melting performance. In lithium-ion batteries, bio-graphite anodes exhibited stable cycling behavior in both half-cell and full-cell configurations. Finally, process simulation and life cycle assessment showed that the proposed biomass-based graphite production pathway achieves substantially lower cumulative energy demand and greenhouse gas emissions compared with conventional natural and fossil derived synthetic graphite routes.

Overall, this thesis establishes a comprehensive framework for sustainable graphite production from bio-based carbon precursors, integrating process development, parameter optimization, scale-up strategy, application validation, and environmental assessment. This work demonstrates that catalytic graphitization is a commercially viable and environmentally superior alternative to conventional graphite supply chains.

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