Activated carbons derived from residual biomass pyrolysis and their CO_2 adsorption capacity

摘要

This research aimed to investigate the pyrolysis process of rapeseed oil cake/walnut shell mixture and to assess the pyrolysis products. The solid fraction was then subjected to high temperature treatment using CO_2 65 vol.% in nitrogen (N_2) as activation agent to obtain activated carbons. The carbon samples were characterized by scanning electron microscopy (SEM), N_2 adsorption at (-196.15 ℃) and measurements of mechanical strength. Two surface treatment methods, including ammonium (NH_3) heat treatment and aqueous monoethanolamine (MEA) impregnation, were used to modify the surface properties of the carbons to increase their CO_2 capture capacity. The influence of treatment conditions and chemical reagent type on carbons properties were investigated and discussed. The surface treatment changed the porous structure and surface chemistry and affected CO_2 adsorption capacity. NH_3 was found more effective than MEA under identical conditions. The NH_3 treatment increased the surface area, especially at lower temperatures (600 ℃) while the chemical impregnation with MEA resulted in a decrease of the surface area. Both the NH_3 treatment and monoethanolamine impregnation have increased the CO_2 adsorption capacity at higher temperature due to the introduction of alkaline nitrogen groups on the surface of carbons that are selective to CO_2 molecules.