Effect of Core–Shell Structure and Chitosan Addition on Catalytic Activities of Copper-Containing Silica–Aluminosilicate Composites in deNO_x Reaction by H₂

Abstract

Mesoporous silica-aluminosilicate composites were used as supports for selective catalytic reduction of NO by H2 using copper catalyst. Effect of loading techniques and structures of the supports on the catalytic performance were investigated. The nature, the oxidation state of copper, the structural properties and the morphology of the catalysts were characterized by means of UV-vis spectra, Fourier Transform Infrared Spectroscopy (FTIR), nitrogen sorption, and transmission electron microscopy, respectively. By using substitution technique, the copper(II) species were introduced into the silica-aluminosilicate framework by replacing aluminum atoms that located in the tetrahedral coordination. On the other hand, by using incipient wetness impregnation method, the copper species were deposited on the surface of composite materials. Upon testing their performances in deNO(x) reaction, the catalysts prepared by incipient wetness impregnation method showed higher catalytic activity than those prepared by substitution technique in any copper content. The core-shell structure was able to enhance the catalytic performance. It was found that, among the tested catalysts, the 1.5% Cu loaded core-shell mesoporous silica aluminosilicate composites prepared by an incipient wetness impregnation yielded the highest NO conversion of approximately 59%. However, the addition of chitosan creating macroporosity and controlling the uniform small clusters did not improve the catalytic performance.

Roles of ZnO in Cu/Core–Shell Al–MCM-41 for NO Reduction by Selective Catalytic Reduction with NH3: The Effects of Metal Loading and Cu/ZnO Ratio

“…It should be noted that in this work, the Cu loading of the catalysts was increased by using the impregnation method, in which copper predominately exists as CuO species. 5,18 In addition, with higher metal loading, it is more difficult for a copper precursor to infiltrate deeper in the channels of the catalysts and occupy the exchange sites, leading to the formation of more CuO species on the surface of the catalyst.…”

“…Preparation of Catalysts. A core−shell structured Al−MCM-41 was synthesized via the method reported by Chamnankid et al (2012), 5 in which cetyl trimethylammonium bromide (CTAB: 98%, APS Ajax Finechem) was used as a structural directing agent whereas tetraethyl orthosilicate (TEOS: 98%, Sigma-Aldrich) and aluminum nitrate (Al-(NO 3 ) 3 •9H 2 O: 98%, QREC) were used as silica and alumina sources, respectively. The molar gel composition was 1SiO 2 :0.2CTAB:100H 2 O, whereas the Al 2 O 3 /SiO 2 ratio was fixed at 0.1.…”

“…It should be noted that in this work, the Cu loading of the catalysts was increased by using the impregnation method, in which copper predominately exists as CuO species. 5,18 In addition, with higher metal loading, it is more difficult for a copper precursor to infiltrate deeper in the channels of the catalysts and occupy the exchange sites, leading to the formation of more CuO species on the surface of the catalyst. Interestingly, the reduction temperatures for the two-step reduction of Cu 2+ are observed to increase with increasing metal content, suggesting that at present, it is more difficult to reduce copper ions.…”

“…The oxidation state of copper plays an important role in NO reduction. It has been suggested that Cu + is the key active species for NO reduction 5−7 and the transition between Cu 2+ and Cu + species taking place under SCR reaction was found to be the key factor in this reaction. 1,4 The nature of Cu can be modified by a promoter and different metal loadings.…”

Role of Copper and Cerium on Core–Shell Al-MCM-41 in NO Reduction via a SCR-CH4

“…44 It was found that the use of Al-MCM-41 as the support also showed a high hydrothermal stability after heating to 800 C in the presence of H 2 O in SCR of NO with C 2 H 4 ; the Al-MCM-41 support is consequently more stabilized than the ZSM-5 support. Based on our previous work, 45 coreshell-structured Al-MCM-41 enhances the performance of NO reduction, and copper can be easily reduced from Cu(II) to Cu(I), which is an active site for de-NO x catalytic reaction. On the other hand, the problem of hydrothermal stability can also be improved by adding Ce as a promoter.…”