Fast pyrolysis of mannan-rich ivory nut (Phytelephas aequatorialis) to valuable biorefinery products

摘要

Ivory nut residues from the palm Phytelephas aequatorialis were converted via fast pyrolysis into a set of valuable biorefinery products, being (i) pyrolysis liquids rich in levomannosan and 5-hydroxymethyl furfural (5-HMF), (ii) biochar, with potential for soil applications, (iii) and non-condensable gases with potential for upgrading and syngas processes. The ivory nut residues were mannan-rich leftovers from button manufacturing in Ecuador. A handful of studies, dating back from the 20th century, have investigated gram-scale valorization of ivory nut to e. g. mannose. Nevertheless, advances in science and technology on biorefinery products called for a comprehensive reassessment of the valorization potential of this underutilized feedstock. A fully equipped, continuously operated lab-scale reactor (200 g. h(-1) feed) was used for pyrolysis at 350 degrees C and 500 degrees C. The pyrolysis liquid yield was 57.53 wt% at 350 degrees C and 60.36 wt% at 500 degrees C. The aqueous phase obtained at 350 degrees C contained 17.5 wt% (d. b.) anhydrosugars, of which 90% was levomannosan, and contained 11.6 wt% (d.b.) furans, of which 56% was 5-HMF and 17% furfural. The carbon stability of the biochars, measured with the Edinburgh accelerated ageing tool, were 40.6% and 64.6%, respectively. Non-condensable gases during pyrolysis at 350 degrees C only were composed of CO2 and CO (CO2: CO molar ratio of 4: 1), while at 500 degrees C, gases were obtained with a CO2: CO: H-2: CH4 molar ratio of 9: 9: 4: 1. Overall, the results demonstrate that pyrolysis of ivory nut holds potential as starting point for valuable biorefinery products.