Infusion of fly ash in alkali salt promoted MgO-based sorbent for CO2 capture at elevated temperatures

Abstract

Carbon capture at elevated temperatures (200-450°C) using MgO-based solid sorbents, typically suffers from slow kinetics and premature saturation lowering the overall uptake performance. A key factor responsible for this is the agglomeration of MgCO₃ during carbonation, which could be potentially overcome by the addition of inert along with promoters. In this context, this work systematically investigates the infusion of Fly ash (FA) as inert in pure MgO and alkali-salt-promoted MgO-based sorbents prepared by the sol–gel method. The study includes characterizing the prepared sorbents based on morphological and textural properties and investigating the uptake kinetics along with cyclic performance based on thermogravimetric analysis under conditions of 250°C and 300°C for 45 mins. Among all tested modified sorbents, MgO_10NaNO₃_5FA exhibited the highest uptake capacity of 14.56 mmol/g (MgO basis) followed by MgO_15NaNO₃ (14.27 mmol/g) at 300°C. Cyclic studies over 10 cycles reveal higher conversion of FA-infused sorbent (MgO_10NaNO₃_5FA: 59.76 %) over non-FA-infused sorbent (MgO_10NaNO₃: 54.50 %) showing higher stability of the former. The results establish minimal FA infusion (5 %) in alkali nitrates promoted sorbent favorable for CO₂ capture at moderate temperature while elucidating physicochemical aspects during uptake.