CO2 Sorption by Hydrotalcite-Like Compounds in Dry and Wet Conditions

Abstract

Abstract A pre-combustion removal option, coupling water–gas shift and CO2 capture is the well-known sorption-enhanced water–gas shift (SEWGS): the removal of CO2 produced by WGS reaction, shifting the thermodynamic equilibrium, enhances H2 production. Among the different CO2 sorbents, hydrotalcite-like compounds work at the required intermediate temperature (T = 200–400°C). Using low supersaturation method, three different sorbents were synthesized. Sieved fractions were impregnated with 20%w/w K2CO3 and then dried and subjected to thermal treatment. Sample characterization was performed by means of FT-IR spectroscopy, XRD analysis and TG-DTA analysis. Sample analysis was carried out after synthesis, thermal treatment (calcination) and after fixed bed reactor capture tests. Sorption and desorption tests were performed in a fixed bed microreactor, under cyclic conditions, at temperature level of T = 350°C and P = 5 bar in dry and wet condition. The amount of CO2 captured by the sorbent in each test was quantified by means of a first order with dead time flow distribution model applied to the experimental system. Sorption capacity of sorbents in dry conditions increases of 30% with respect to previous atmospheric pressure results obtained in fluidized bed. These sorbents seem to be good candidates to be used as a bi-functional sorbent-catalyst for SEWGS.