RESUMO
This report describes strategies to increase the reactive surfaces of integrated gold nanoparticles (AuNPs) by employing two different types of host materials that do not possess strong electrostatic and/or covalent interactive forces. These composite particles are then utilized as highly reactive and recyclable quasi-homogeneous catalysts in a C-C bond forming reaction. The use of mesoporous TiO2 and poly(N-isopropylacrylamide), PNIPAM, particles allows for the formation of relatively small and large guest AuNPs and provides the greatly improved stability of the resulting composite particles. As these AuNPs are physically incorporated into the mesoporous TiO2 (i.e., supported AuNPs) and PNIPAM particles (i.e., encapsulated AuNPs), their surfaces are maximized to serve as highly reactive catalytic sites. Given their increased physicochemical properties (e.g., stability, dispersity, and surface area), these composite particles exhibit notably high catalytic activity, selectivity, and recyclability in the homocoupling of phenylboronic acid in water and EtOH. Although the small supported AuNPs display slightly faster reaction rates than the large encapsulated AuNPs, the apparent activation energies (Ea) of both composite particles are comparable, implying no obvious correlation with the size of guest AuNPs under the reaction conditions. Investigating the overall physical properties of various composite particles and their catalytic functions, including the reactivity, selectivity, and Ea, can lead to the development of highly practical quasi-homogeneous catalysts in green reaction conditions.
RESUMO
Mesoporous hollow silica material (MHS) was synthesized using polystyrene as a template. Later, it was modified by wet impregnation with tetraethylenepentamine (TEPA) as a solid adsorbent for CO2 capture. Transmission electron microscopy (TEM), X-ray diffraction (XRD), IR, and TGA were used to characterize the average diameter, shell thickness, crystalline structure, and TEPA load of the prepared adsorbents. An increase in the amount of loaded TEPA, improved the CO2 adsorption capacity of the prepared adsorbents. The highest CO2 adsorption capacity was obtained using a 50 wt% TEPA load (AMHS-50).
RESUMO
The objective of the study is to investigate the morphology effects of porous silica supports on the CO2 capture performance of solid amine adsorbents. Mesoporous hollow silica spheres (MHSS) and mesoporous silica spheres (MSS) were synthesized and modified by wet impregnation with tetraethylenepentamine (TEPA) as solid adsorbents. The prepared adsorbents were characterized by TEM, XRD, N2 adsorption/desorption, FT-IR, and TGA. The CO2 capture performances of the adsorbents were evaluated using a flow method at atmospheric pressure. Gas chromatography was used to analyze the CO2 concentration in the influent and effluent gas streams. Due to the excellent structural properties of the MHSS, it was found to be a better amine support than MSS. An increase in the amount of loaded TEPA improved the CO2 adsorption capacity of the prepared adsorbents. The optimum CO2 adsorption capacities were obtained with MHSS-47 and MSS-41.
RESUMO
CuO-TiO2 composite hollow nanospheres were synthesized using polystyrene as a template. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the average diameter, shell thickness, crystalline structure, and composition of CuO-TiO2 composite hollow nanospheres. UV-vis absorption spectrum was used to measure the optical absorption property of the CuO-TiO2 composite hollow nanospheres. The photocatalytic performance of the samples was characterized by degrading 10 mg·L-1 methylene blue under visible light irradiation. The results showed that the CuO-TiO2 composite hollow nanospheres exhibited better photocatalytic performance than the pure TiO2 nanoparticles and TiO2 hollow nanospheres. The improvement in photocatalytic performance was attributed to the enhanced light absorption in the visible light region.
