Experimental studies on the pyrolysis of humins from the acid-catalysed dehydration of C6-sugars

• Acid catalysed conversions of sugars leads to solids (humins) formation.
• Humins from glucose and fructose have been characterised.
• Detailed analysis reveals the presence of furanic structures.
• Reaction pathways involve dehydration reactions.
• Pyrolysis of humins leads to liquid products with wide range of components.

Pyrolysis of two representative solid humin samples using pyrolysis GC–MS (300–600 °C, 10 s, He atmosphere) and micro-pyrolysis (500 °C, 12 s, N2 atmosphere) are reported. The humins were obtained by treatment of aqueous solutions of d-glucose and d-fructose at 180 °C in the presence of sulphuric acid (0.1 M) and isolated as brown solids in 20–30% yield. The products were characterised with various techniques (SEM, elemental analysis, solid state CP-NMR, FTIR). Pyrolysis GC–MS showed the presence of furanics and organic acids, though the individual components were present in minor amounts (<1 wt%). Micro-pyrolysis yielded 30 wt% gaseous and liquid products, the remainder being a solid char. Gas–liquid yields are lower than obtained for a typical lignin sample (kraft lignin) under similar conditions.