SBA-15 prepared via ethanol extraction for template removing was grafted with three kinds of amine precursors (mono-, di-, tri-aminosilanes) to synthesis new CO2 adsorbents. The SBA-15 support and the obtained adsorbents were characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), N2 adsorption/desorption, thermogravimetry (TG), elemental analysis, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that, except higher silanol density, the ethanol-extracted SBA-15 support possessed a more regular mesophase and thicker walls than traditionally calcined samples, leading to a good stability of the adsorbent under steam treatment. The adsorption capacity of different amine-grafted samples was found to be influenced by not only the surface amine density, but also their physiochemical properties. These observations provide important support for further studies of applying amine-grafted adsorbents in practical CO2 capture process.
Two type of modulators, including sodium acetate and triethylamine were used to synthesize nanosized HKUST-1 crystals with tailored size and morphology using a coordination modulation method. The results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 sorption isotherms confirm that the size of the HKUST-1 crystals can be tuned from the micron scale to the nanoscale through precise modulation of the amounts of the modulators. Moreover, hierarchical porous structures are obtained with the addition of modulators. It is suggested that a moderate acid–base environment and capping groups play an important role in controlling the size and morphology of HKUST-1. Dynamic CO2 breakthrough experiments illustrate that the CO2 capacity of nanosized HKUST-1 crystals is superior to that of micron-sized HKUST-1 crystals under low CO2 partial pressure conditions (0.1 bar). Besides, the CO2 adsorption capacity of nanosized HKUST-1 crystals was maintained after ten adsorption/desorption cycles.
28 June 2008 in Industrial & Engineering Chemistry Research
A series of Ce/SBA-15 catalysts with different degrees of hydrophobicities were prepared via a post-grafting method and used for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol.