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.