Investigation of Porous Silica Supported Mixed-Amine Sorbents for Post-Combustion CO₂ Capture

Abstract

Prospective post-combustion CO2 capture sorbents were prepared by the immobilization of a low-molecular-weight, branched polyethyleneimine (PEI) and 3-(aminopropyl)triethoxysilane (APTES) within a commercially available porous PQ Corporation CS-2129 silica support to investigate (i) CO2 adsorption properties of the supported mixed-amine (PEI+APTES) sorbents in both pure CO2 environments and simulated flue gas conditions, (ii) their thermal and hydrolytic stability over numerous adsorption and desorption cycles, and (iii) their equilibrium and kinetic adsorption behavior. Initial CO2 adsorption–desorption measurements via thermogravimetric analysis (TGA) were conducted in pure CO2 to measure dry, near-equilibrium CO2 adsorption capacities, together in calculating amine efficiencies, which was recognized in being a meaningful criterion in evaluating sorbent performance for selecting the “most favorable” mixed-amine (PEI+APTES) composition. The as-prepared materials containing various weight ratios of PEI to APTES showed less uptake of CO2, relative to the supported PEI-only impregnated material under investigated TGA experimental conditions. Nitrogen adsorption–desorption isotherms in evaluating the physical properties of the synthesized mixed-amine (PEI+APTES) samples showed reduced values specific to surface area, and total pore volume largely predictable from the successful incorporation of PEI multilayers into the structure of the porous silica matrix, together with unreacted APTES moieties remaining behind after material synthesis. Breakthrough curves produced by (PEI-15-APTES-35)-PQCS2129, (PEI-25-APTES-25)-PQCS2129, (PEI-35-APTES-15)-PQCS2129, and (PEI-50)-PQCS2129 showed mean near-equilibrium CO2 adsorption capacities of 1.81 ± 0.17, 2.43 ± 0.26, 2.44 ± 0.19, and 2.44 ± 0.45 mol CO2/kg of sorbent, respectively, over multiple CO2 adsorption–desorption cycles utilizing a 10% CO2, 8% H2O (balance, He stream) at 60 °C and 1.01 bar for adsorption; followed by regeneration in a He stream containing 90 vol% water vapor at 105 °C. From these studies, (PEI-25-APTES-25)-PQCS2129 and (PEI-35-APTES-15)-PQCS2129 exhibited a higher CO2 capturing efficiency (absorbed amount of CO2 per gram of PEI), relative to (PEI-50)-PQCS2129, indicating the PEI/APTES interface (i.e., interaction between layers of surface alkyl chains associated with APTES and PEI) is perhaps contributing to improving the deposition/dispersion of PEI, thereby decreasing the diffusion resistance with regard to CO2 entering into the bulk of the PEI multilayers. Conversely, the lower amine efficiency of (PEI-50)-PQCS2129 can be ascribed to the possible clustering of the PEI molecules from the higher PEI loading, resulting in a decrease of accessible amine sites and creating a higher diffusional resistance in connection with CO2 molecules penetrating into the majority of layers of PEI. Near-equilibrium CO2 adsorption measurements of (PEI-25-APTES-25)-PQCS2129 in utilizing the laboratory-scale, fixed-bed flow reactor system located at ADA-ES (Littleton, CO) ...

CO2 Adsorption: Experimental Investigation and CFD Reactor Model Validation

“…Abbasi, Choi, Fauth, Gray, and Sjostrom [18-20, 22, 23, 26, 34] have all considered mesoporous materials for sorbents in carbon capture systems The work presented in this paper is based on a silica-supported amine sorbent material developed at NETL. This material is very similar to the materials described by both Gray et al [19,20] and Fauth et al [18]. The CO 2 adsorption process is modeled utilizing mechanism that is similar to the one proposed by Lee et al [21] for a similar sorbent for a dry reaction.…”

“…The interphase momentum transfer rate per unit volume, , in (4) is found from (17) and, finally, (18) gives the solid displacement. Collectively, these equations and relationships provide the backbone to CPFD's Barracuda code that was used in this work.…”

“…There are four main categories of these technologies: precombustion, postcombustion, oxy-fuel combustion, and chemical looping [5]. [12] 13X Zeolite PSA and VSA N/A Chaffee et al [13] 13X Zeolite VSA N/A Schell et al [14] Activated Carbon PSA Fixed bed Wang et al [15] 13X Zeolite and activated carbon VPSA Fixed bed Pirngruber and Leinekugel-Le-Cocq [16] Supported polyamine PSA N/A Siriwardane et al [17] NaOH/CaO TSA TGA and fixed bed Fauth et al [18] Supported mixed amines TSA Fixed bed Gray et al [19] Supported tertiary amine TSA TGA and fixed bed Gray et al [20] Supported amine TSA TGA Lee et al [21] Supported amine TSA TGA Sjostrom et al [22] Supported amine TSA CFB Sjostrom and Krutka [23] Supported amine TSA Fixed bed Monazam et al [24] Supported amine TSA Fluidized bed…”

“…An overview of the literature [12][13][14][15][16][17][18][19][20][21][22][23][24] and the various sorbent reactor configurations is presented in Table 1. Samanta et al [25] and Choi et al [26] provide comprehensive reviews of sorbent processes employing temperature swing, pressure swing, or vacuum swing to regenerate the adsorbate, referred to as PSA, TSA, and VSA concepts, respectively.…”

“…Samanta et al [25] and Choi et al [26] provide comprehensive reviews of sorbent processes employing temperature swing, pressure swing, or vacuum swing to regenerate the adsorbate, referred to as PSA, TSA, and VSA concepts, respectively. The TSA concepts have gained favor recently because the polyamine impregnated sorbents which have strong temperature dependence in the temperature range of interest can be made with high CO 2 capacity [17][18][19][20][21][22][23][24].…”