Co-processing of bio-oils and petroleum feedstocks: The role of catalyst synthesis routes in mitigating catalytic challenges of co-processing

The increasing pressure to adopt sustainable energy, along with the global shift to decarbonise refinery operations, has strengthened interest in co-processing bio-oils with petroleum intermediate feedstocks. Bio-oils obtained from pyrolysis and hydrothermal liquefaction provide significant renewable carbon potential. However, they come with major challenges such as high oxygen levels, acidity, water content, viscosity, alkali metals, and thermal instability. These properties place strict limits on the catalyst activity, selectivity, and long-term stability during co-processing in residue fluid catalytic cracking (RFCC) and other refinery process units. Although previous reviews largely focused on co-processing pathways and feedstock variability, the present review offers a distinct contribution by providing a rigorous assessment of how specific catalyst synthesis routes such as in-situ and incorporated synthesis influence the structural resilience and contaminant tolerance of zeolite-based catalysts. This review explores bio-oil properties, the various upgrading pathways, the potential insertion points in the refinery, and the catalytic challenges experienced when bio-oils are blended with intermediate hydrocarbon feedstocks. Additionally, recent developments in catalyst design, like boron modification, improved diffusion, and chloride-free binders, are discussed as promising strategies for meeting the demands of bio-oil co-processing. By combining these findings, this work offers a guide for choosing catalyst design strategies that maximise renewable carbon retention while preventing catalyst deactivation. Ultimately, this review highlights that with better catalyst design, co-processing bio-oil at 5 – 20 wt% is a practical way to reduce refinery carbon emissions in the near future while staying within current industry operating limits.