Cold sintered geopolymer and geopolymer-zeolite composite sorbents for CO2 capture
Cristina Di Pietro, W. Guzman, Elettra Papa, Elena Landi, Francesco Miccio, Matteo Minelli, Valentina Medri
Abstract
Geopolymer and geopolymer-zeolite composite monoliths were produced by cold sintering process (CSP) at 40°C and 56 MPa or 168 MPa, as solid adsorbents for CO 2 capture. Structural integrity, surface area and adsorption capacity are achieved along with reducing the energy penalty, resulting in more efficient, durable and sustainable CO 2 adsorbents. KOH or NaOH 4 M were used as alkaline solutions (to wet the powders, namely a geopolymer with SiAl = 2.0 and KAl = 1.0, a geopolymer containing 81 vol% of in situ formed zeolite NaA and commercial zeolite Na13X, and activate the near room temperature sintering process under pressure. This process resulted in relative densities approaching 60 %. Pore size distributions , microstructures, specific surface areas up to 310 m 2 g −1 for geopolymer-Na13X based monoliths, and compressive strengths from 4 to 27 MPa area found to be mainly dependent on the material composition. Adsorption isotherms for CO 2 and N 2 were also obtained to assess the performances of the adsorbents. The CO 2 capacity of zeolite Na13X is basically preserved, reaching 1.9 mmol g −1 (at 35°C and p CO2 =0.1 bar). The great CO 2 capacity and CO 2 /N 2 selectivity, especially at low CO 2 partial pressure , makes these materials great candidates for post combustion carbon capture adsorbents.