CO2 Capture by the Amine-modified Mesoporous Materials
ABSTRACT Novel CO2 adsorbents were prepared by grafting two different aminosilanes on mesoporous silica MCM-41 and SBA-15. The properties of the mesoporous materials before and after surface modification were investigated by powder X-ray diffraction (XRD) pattern, solid-state 29Si nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectra, and measurements of N2 adsorption and desorption isothermal, which confirmed that aminosilanes were grafted on the surface of the channels in the mesoporous materials. Thermogravimetry analysis (TGA) evaluated the amount of grafted amine to be about 1.5–2.9 mmol·g−1. The CO2 adsorption capacity of MCM-41 increased from 0.67 mmol·g−1 to 2.20 mmol·g−1 after AEAPMDS (N-β-(aminoethyl)-γ-aminopropyl dimethoxy methylsilane) modification (p=101 kPa) at room temperature. The studies of the mechanism of CO2 adsorption suggested that there were two main contributions to the increase: the chemical adsorption based on the active sites of amine groups and the capillary condensation caused by the nano-scale channels of the mesoporous materials.
SourceAvailable from: Yafei Guo[Show abstract] [Hide abstract]
ABSTRACT: The requirement for self-sustained and long-duration human operations in confined spaces including submarines, spacecrafts, or underground citadels has made ambient removal of low-concentration CO 2 a critical technology. Mesoporous silica materials have been regarded as promising carriers to support active components for CO 2 sorption. The CO 2 sorption kinetic of mesoporous silica-supported adsorbent is an important parameter to be assessed. In this paper, K 2 CO 3-impregnated mesoporous silicas were prepared by impregnating K 2 CO 3 on MCM-41, SBA-15, and silica gel (SG) in ethanol solution, respectively. The CO 2 sorption experiments were performed in a simulated confined space atmosphere of 1.0 % CO 2 , 2.0 % H 2 O, and 293–333 K using thermogravimetric analysis. The kinetic performances of the sorbents were evaluated by fitting the experimental data to the shrinking core model. K 2 CO 3 /SG exhibited the optimum carbonation kinetic performance. The apparent activation energies for chemical reaction-controlled region and internal diffusion-controlled region are 3.95 and 64.87 kJ mol-1 , respectively. To obtain the specific carbonation kinetic mechanism, a double exponential model was used to simulate the car-bonation process of K 2 CO 3 /SG. The apparent activation energies for H 2 O diffusion–hydration and CO 2 diffusion– carbonation stages are 8.40 and 4.32 kJ mol-1 , respectively. H 2 O diffusion–hydration is the rate limiting step in the whole carbonation process.Journal of Thermal Analysis and Calorimetry 03/2015; DOI:10.1007/s10973-015-4537-9 · 2.21 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: In this work, the amine grafting treated activated carbons were studied for carbon dioxide adsorbent. The surfaces of activated carbon were functionalized by 3-chloropropyltrimethoxysilane, which was subsequently grafted with amine compounds tris-(2-aminoethyl)amine and tri-ethylenetetramine and subjected to comparison. The surface functional groups of the amine grafted activated carbons were characterized using XPS. The textural properties of the amine grafted activated carbons were analyzed by N 2 /77 K isotherms. Carbon dioxide adsorption behaviors of the amine grafted activated carbons were examined via the amounts of carbon dioxide adsorption at 298 K and 1.0 atm. From the results, tris-(2-aminoethyl)amine grafted activated carbons showed 43.8 cm 3 /g of carbon dioxide adsorption while non-treated activated carbons and tri-ethylenetetramine grafted activated carbons showed less carbon dioxide adsorption. These results were thought to be due to the presence of isolated amine groups in the amine compounds. Tris-(2-aminoethyl)amine grafted activated carbons have basic features that result in the enhancement of adsorption capacity of the carbon dioxide molecules, which have an acidic feature.Bulletin- Korean Chemical Society 09/2011; 32(9). DOI:10.5012/bkcs.2011.32.9.3377 · 0.84 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: New ternary and binary composite mesostructures consisting of alumina, zirconia and organosilica with isocyanurate bridging groups were synthesized via co-condensation of suitable precursors in the presence of triblock copolymer, Pluronic P123. The resulting binary amd ternary composite mesostructures were used for CO2 capture at low (0 oC), ambient (25 oC), and elevated (60, 120 oC) temperatures. The CO2 adsorption capacities measured at 1 atm for alumina-organosilica mesostructure are: 1.43 mmol/g at 0 oC, and 1 mmol/g at 25 oC. Much higher CO2 adsorption capacities were recorded at 1 atm for zirconia-organosilica mesostructure: 2.53 mmol/g at 0 oC, and 1.93 mmol/g at 25 oC. This significant increase in the CO2 uptake for zirconia-organosilica was achieved due to the development of microporosity, which was shown to be beneficial for CO2 physisorption at low pressures. Temperature programmed desorption (TPD) was used to measure the CO2 sorption capacities for the mesostructures studied at 60 and 120 oC. The TPD studies revealed the superior sorption capacities of zirconia-organosilica mesostructures at 60 oC (3.02 mmol/g) and 120 oC (2.76 mmol/g). Various surface hydroxyls present in alumina and zirconia are primarily responsible for CO2 capture. These hydroxyls were shown to be essential for interactions with CO2 by forming hydrogen carbonate and bidentate carbonate complexes. The thermal stability, corrosion resistivity, and chemical stability of the mesostructures studied make them attractive sorbents for CO2 capture in the fossil fuel-based power plants, which generate large volumetric flow rates of flue gas at 1 atm with low partial pressure of CO2 in the temperature range of 100-150 oC.12/2014; 3(6). DOI:10.1039/C4TA04677C