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

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.

Recovery of acetic acid from an aqueous pyrolysis oil phase by reactive extraction using tri-n-octylamine

The application of reactive extraction to isolate organic acids, particularly acetic acid, from the aqueous stream of phase splitted pyrolysis oil using a long chain aliphatic tertiary amine is reported. Acetic acid recovery was optimized by selecting the proper amine and diluent combination and adjustment of the process conditions. The best results were obtained with tri-n-octylamine (TOA) in 2-ethyl-hexanol (40 wt%) with 84% acetic acid recovery at equilibrium conditions (room temperature). Other organic acids present in the feed (formic acid and glycolic acid) were also co-extracted (92% and 69% extraction efficiencies), as well as relatively non-polar compounds like substituted phenolics and ketones. The continuous reactive extraction process was successfully demonstrated in a centrifugal contactor separator (CCS) device, and acetic acid recoveries of 51% and 71% were obtained in a single CCS device and a two stage cross currently operated cascade, respectively.