Catalytic Upgrading of Coal Pyrolysis Products

Coal pyrolysis entails the thermal decomposition of coal in the absence of oxygen, yielding solid char, liquid tar and condensable liquids, and non-condensable gases. Catalytic upgrading applies solid catalysts to interact with volatiles during or after pyrolysis, refining the molecular composition of tar and gas streams, increasing yields of light hydrocarbons, suppressing undesirable polycyclic aromatics and heteroatomic species, and improving fuel properties. Techniques range from in-situ bed mixing and two-stage reactor configurations to ex-situ vapour-phase catalytic beds. Typical catalysts include supported metal oxides, zeolites, alkaline earth oxides, transition metals and waste-derived residues. Parameters such as catalyst composition, temperature, residence time and atmosphere profoundly influence cracking, dehydrogenation, aromatisation and adsorption–desorption processes. Advances aim to produce cleaner, higher-value chemical feeds from coal, reduce environmental pollutants, and integrate carbon management strategies in a cost-effective and scalable manner.

Research from Nature Portfolio

Recent studies have explored catalytic depolymerisation of lignite using CoCl₂ and ZnCl₂ salts, demonstrating up to a 20 % increase in tar yield accompanied by an enrichment of alkanes and two-ring aromatics. Depolymerisation conditions were optimised to promote radical cleavage while minimising char formation, offering a route to tailor tar composition via metal-ion mediated bond scission. More recently, mixed metal-oxide catalysts supported on γ-Al₂O₃ have been deployed in fixed-bed pyrolysis, revealing that Fe₂O₃- and Co₂O₃-modified carriers can more than double tar yield compared to uncatalysed pyrolysis. These catalysts enhance light oil fractions and phenolic output by facilitating cracking of high-molecular-weight species and selectively promoting dehydrogenation and ring-opening, suggesting scalable opportunities for metal-oxide-mediated tar upgrading.

Catalytic Upgrading of Coal Pyrolysis Products publication trend

The graph below shows the total number of articles in catalytic upgrading of coal pyrolysis products across all publications each year (not limited to Nature Index journals).

Technical terms

Pyrolysis: Thermal decomposition of organic material in an oxygen-free environment, yielding char, tar and gaseous products.

Catalytic upgrading: Use of solid catalysts to modify pyrolysis vapours or tar fractions, improving yield and quality of hydrocarbons.

Char: Solid carbonaceous residue remaining after pyrolysis, often used as heat carrier or adsorbent.

Tar: Complex mixture of condensable hydrocarbons from pyrolysis, comprising aromatic, aliphatic and heteroatom-containing compounds.

Fluidized-bed reactor: Vessel in which solid particles are suspended by an upward fluid flow to ensure uniform heat and mass transfer.

Fixed-bed reactor: Reactor containing a stationary bed of catalyst through which vapour-phase reactants pass.

Dehydrogenation: Catalytic removal of hydrogen from organic molecules, often converting saturated to unsaturated species or aromatics.

Aromatisation: Formation of aromatic rings from aliphatic precursors via cyclisation and dehydrogenation over acid or metal sites.

References

1. Catalytic depolymerization of a typical lignite for improving tar yield by Co and Zn catalyst. Scientific Reports (2017).
2. Study on lightening of coal tar with metal oxide supported γ-Al2O3 catalyst. Scientific Reports (2023).
3. The Influence of Solid Heat Carrier Load of Char on Pyrolysis Characteristics of Pulverized Coal in a Fluidized Bed Reactor. Energies (2024).
4. Catalytic Pyrolysis of Naomaohu Coal Using Combined CaO and Ni/Olivine Catalysts for Simultaneously Improving the Tar and Gas Quality. Energies (2024).
5. Application of Ni/MgO catalysts in the pyrolysis of bituminous coal. Applied Mathematics and Nonlinear Sciences (2024).