Thermochemical conversion of cobalt-loaded spent coffee grounds for production of energy resource and environmental catalyst.

Thermochemical conversion of cobalt (Co)-loaded lignin-rich spent coffee grounds (COSCG) was carried out to find the appropriate pyrolytic conditions (atmospheric gas and pyrolytic time) for syngas production (H2 and CO) and fabricate Co-biochar catalyst (CBC) in one step. The use of CO2 as atmospheric gas and 110-min pyrolytic time was optimal for generation of H2 (∼1.6 mol% in non-isothermal pyrolysis for 50 min) and CO (∼4.7 mol% in isothermal pyrolysis for 60 min) during thermochemical process of COSCG. The physicochemical properties of CBC fabricated using optimized pyrolytic conditions for syngas production were scrutinized using various analytical instruments (FE-SEM, TEM, XRD, and XPS). The characterizations exhibited that the catalyst consisted of metallic Co and surface wrinkled carbon layers. As a case study, the catalytic capability of CBC was tested by reducing p-nitrophenol (PNP), and the reaction kinetics of PNP in the presence of CBC was measured from 0.04 to 0.12 s-1.