In-situ catalytic hydro-liquefaction of Delonix regia lignocellulosic biomass waste in hydrogen-donor solvent

Abstract

Wastes from forestry residues and tree felling have been a major waste management concern since a long time. This issue had been addressed in this work where utilization of waste Delonix regia biomass by hydro-liquefaction in a hydrogen-donor solvent (methanol) and in presence of Ni–Al co-precipitation catalyst at different temperatures and a fixed pressure have seen to provide synergistic results not only in terms of yield of liquid products but also their higher heating values. To the best of authors’ knowledge, no studies have been testified in the literature using such co-precipitation catalyst for Delonix regia biomass liquefaction. The hydrogen donating capability of alcoholic methanol solvent in the hydro-liquefaction process along with existence of hydrogen rich environment, caused by supply of initial external hydrogen pressure, explained high yield of liquid products. A maximum higher heating value (HHV) of 26.31 MJ/kg for biocrude, obtained at 200 °C and 80 bar final reactor pressure for 60 min reaction time, depicted the potentiality of Ni–Al catalyst in reducing oxygen content of biocrude by partial hydrogenation during the liquefaction process. Apart from this, biocrude showed presence of long chain alkanes, esters, aldehydes and ketones in them. The low phenol content of the biocrude as found from Gas Chromatography-Mass Spectrometry (GC-MS) results were an indication of its less hazardous and toxic nature. The free-flowability and porous nature of solid biochar from this hydro-liquefaction process was a sign of their effectiveness in soil remediation processes and wastewater treatment. Finally, physical properties and fuel potential of biocrude obtained in this process were superior compared to those of bio-oil obtained by catalytic, non-catalytic and hydro-catalytic pyrolysis of same biomass conducted at elevated temperature of 600 °C.