From PFAD Conversion to Refinery Qualification: Catalyst Lifetime, Hydrogen Efficiency and Carbon Integrity in Renewable-Diesel Co-Processing

Palm fatty acid distillate (PFAD) is an attractive free-fatty-acid-rich intermediate for producing paraffinic fuels, but laboratory conversion does not establish reliable performance in an existing petroleum refinery. This critical qualitative literature review examines peer-reviewed research from 2020 to 2026 on PFAD composition, competing deoxygenation chemistry, catalyst deactivation, hydrogen use, refinery co-processing, product qualification, and lifecycle accounting. The thematic synthesis identifies six interlocking constraints: feedstock variability and adsorption-driven side reactions; the carbon-retention versus hydrogen-demand trade-off; uncertainty in catalyst durability; interactions with fossil-stream hydrotreating; hydrogen and thermal-system integration; and contested allocation of upstream palm-oil emissions. It proposes a Feedstock-Catalyst-Hydrogen-Refinery-Carbon (FCHRC) Readiness Framework and a staged evidence scorecard for testing compatibility before deployment. The central finding is conditional: PFAD-to-hydrocarbon conversion has been demonstrated in several settings, whereas long-term, refinery-specific co-processing reliability and unqualified low-carbon status cannot be inferred from high short-run conversion or yield. Future studies should combine representative PFAD characterization, long-duration fixed-bed testing, mass and hydrogen balances, petroleum co-feed benchmarks, appropriate fuel specifications, and transparent consequential lifecycle scenarios. The framework is conceptual and not presented as a field-validated technology.