Mass-resolved UV-Vis-GPC mapping diagnoses catalyst ageing in RCF lignin streams

Area of Science:

• Biorefining and Biomass Valorization
• Catalysis and Green Chemistry
• Spectroscopic and Chromatographic Analysis

Background:

• Catalyst stability is critical for the economic viability of lignin-first biorefineries.
• Conventional characterization methods often miss subtle catalyst deactivation pathways affecting product quality.
• Reductive Catalytic Fractionation (RCF) is a key process for lignin valorization.

Purpose of the Study:

• To develop a sensitive diagnostic tool for detecting catalyst performance decline in RCF.
• To introduce a novel spectral index (SI320) for monitoring catalyst ageing.
• To correlate catalyst deactivation with lignin product quality and estimate catalyst lifespan.

Main Methods:

• Combined UV-Vis spectroscopy with Gel Permeation Chromatography (GPC).
• Introduced a concentration-independent spectral index (SI320 = 1 - A320/A280).
• Analyzed SI320 profiles across apparent molar mass distributions (SI320(M)) using post-consumer cardboard and RANEY® Ni catalyst.

Main Results:

• SI320 effectively detects subtle changes in lignin structure (condensation, oxidation) indicative of catalyst deactivation.
• SI320(M) profiles revealed chromophore accumulation in oligomer fractions from recycled catalysts before bulk yield changes were apparent.
• Linear regression of SI320(M) enabled practical estimation of catalyst life, suggesting RANEY® Ni stability for up to 15 runs (45 h).

Conclusions:

• UV-Vis spectroscopy coupled with GPC serves as a powerful diagnostic platform for lignin-first catalysis.
• The GPC-UV-Vis approach allows rapid, non-destructive monitoring of catalyst performance and optimization of RCF processes.
• This methodology is generalizable for diverse feedstocks and catalysts, guiding the development of durable catalysts for a circular economy.