Sawdust wastes-derived porous carbons for CO2 adsorption. Part 1. Optimization preparation via orthogonal experiment

Abstract

• Orthogonal experiments were conducted to prepare sawdust-derived porous carbons. • Granulation destroys original porous structure of sawdust-derived porous carbons. • Sawdust-derived porous carbon extrudates are inferior to powders for CO 2 adsorption. • Sawdust-derived porous carbon extrudates possess good mechanical property. Sawdust wastes were used as the low-cost feedstock to prepare porous carbons by KOH activation, and the preparation parameters were optimized via orthogonal experiment. Four main activation parameters (i.e., sawdust type, KOH/sawdust ratio, activation temperature and activation time) were investigated. It is found that activation temperature and KOH/sawdust ratio are the two most important parameters that affect the porous texture properties (specific surface area and micropore volume) of sawdust wastes-derived porous carbons. The optimal sawdust wastes-derived porous carbon possesses a high specific surface area of 1601 m 2 /g and a micropore volume of 0.75 cm 3 /g, therefore exhibiting a desirable CO 2 adsorption capacity of 4.25 mmol/g at 0 °C under ambient pressure. Comparatively, the sawdust wastes-derived porous carbon extrudates exhibit the inferior CO 2 adsorption capacity, dropping to 2.85–3.03 mmol/g. It is mainly attributed to the extrusion treatment and binder addition causing the collapse and blockage of the original porous structure, consequently increasing the CO 2 diffusion and adsorption resistance. However, the sawdust wastes-derived porous carbon extrudates possess the advantages of null pressure build-up, improved bulk density and high compress strength (7.3–12.3 MPa) considering the real application point of view.