Sorbents with high efficiency for CO₂ capture based on amines-supported carbon for biogas upgrading

Sorbents for CO₂ capture have been prepared by wet impregnation of a commercial active carbon (Ketjen-black, Akzo Nobel) with two CO₂-philic compounds, polyethylenimine (PEI) and tetraethylenepentamine (TEPA), respectively. The effects of amine amount (from 10 to 70wt.%), CO₂ concentration in the feed, sorption temperature and gas hourly space velocity on the CO₂ capture performance have been investigated. The sorption capacity has been evaluated using the breakthrough method, with a fixed bed reactor equipped with on line gas chromatograph. The samples have been characterized by N₂ adsorption-desorption, scanning electron microscopy and energy dispersive X-ray (SEM/EDX). A promising CO₂ sorption capacity of 6.90 mmol/g_sorbent has been obtained with 70wt.% of supported TEPA at 70°C under a stream containing 80vol% of CO₂. Sorption tests, carried out with simulated biogas compositions (CH₄/CO₂ mixtures), have revealed an appreciable CO₂ separation selectivity; stable performance was maintained for 20 adsorption-desorption cycles.