Selective depolymerization of sugarcane bagasse anaerobic digestate to highly stable phenols-rich bio-oil with the iron-doped K-feldspar catalyst.

Sustainable implementation of thermochemical conversion of biomass to targeted products is dependent on innovations in catalyst design and tuning of structure-property relationships. This study details the use of potassium feldspar (K-feldspar) as a support doped with different iron (Fe) concentrations via wet impregnation (WI) method for hydrothermal liquefaction (HTL) of sugarcane bagasse anaerobic digestate. The Fe/K-feldspar supported catalysts were synthesized and characterized using X-ray diffraction, Inductively Coupled Plasma Optical Emission spectroscopy, Brunauer-Emmet-Teller and Scanning Electron Microscopy analytical methods. Amongst all the catalysts, K-feldspar dopped with 10 wt% Fe (WI-10) was more effective, producing 51.2 wt% bio-crude. The catalyst's activity has been related to the balanced proportion of the microcline: sanidine: haematite (2.8:3.3:1) phases of Fe present on the catalyst, the surface area (porosity), and the surface functionality, thus conferring desirable activity properties. In addition, the WI-10 catalyst had a better selectivity towards substituted phenols that can potentially be used for higher-value applications such as the production of Nylons 6 and 66, and bioplastics. The bio-oil produced with WI-10 has also been demonstrated to be highly stable. The catalyst was reusable up to four times maintaining moderate catalytic performance, and a simple regeneration protocol was shown to restore the activity of the catalyst. The resulting solid residue also exhibited promise as a viable material for use in electrodes for Lithium-ion batteries (LiB). Therefore, this research has demonstrated a promising and sustainable resource recovery strategy for valorising wet biomass wastes into streams of useful products for valuable chemical production and energy application.