Effect of ceria addition to na₂o-zro₂ catalytic mixtures on lignin waste ex-situ pyrolysis

Waste lignin is a potential source of renewable fuels and other chemical precursors under catalytic pyrolysis. For this purpose, four mixed metal oxide catalytic mixtures (Cat) derived from Na ₂CO ₃, CeO ₂ and ZrO ₂ were synthesised in varying compositions and utilised in a fixed bed reactor for catalytic vapour upgrading of Etek lignin pyrolysis products at 600 °C. The catalytic mixtures were analysed and characterised using XRD analysis, whilst pyrolysis products were analysed for distribution of products using FTIR, GC-MS and EA. Substantial phenolic content (20 wt%) was obtained when using equimolar catalytic mixture A (Cat_A), however the majority of these phenols were guaiacol derivatives, suggesting the catalytic mixture employed did not favour deep demethoxylation. Despite this, addition of 40–50% ceria to NaZrO ₂ resulted in a remarkable reduction of coke to 4 wt%, compared to ~9 wt% of NaZrO ₂. CeO ₂ content higher than 50% favoured the increase in conversion of the holo-cellulose fraction, enriching the bio-oil in aldehydes, ketones and cyclopentanones. Of the catalytic mixtures studied, equimolar metal oxides content (Cat_A) appears to showcase the optimal characteristics for phenolics production and coking reduction.