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A method established in the present study has proven to be effective in the synthesis of Mn(2)O(3) nanocrystals by the thermolysis of manganese(III) acetyl acetonate ([CH(3)COCH=C(O)CH(3)](3)-Mn) and Mn(3)O(4) nanocrystals by the thermolysis of manganese(II) acetyl acetonate ([CH(3)COCH=C(O)-CH(3)](2)Mn) on a mesoporous silica, SBA-15. In particular, Mn(2)O(3) nanocrystals are the first to be reported to be synthesized on SBA-15. The structure, texture, and electronic properties of nanocomposites were studied using various characterization techniques such as N2 physisorption, X-ray diffraction (XRD), laser Raman spectroscopy (LRS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results of powder XRD at low angles show that the framework of SBA-15 remains unaffected after generation of the manganese oxide (MnO(x)) nanoparticles, whereas the pore volume and the surface area of SBA-15 dramatically decreased as indicated by N2 adsorption-desorption. TEM images reveal that the pores of SBA-15 are progressively blocked with MnO(x) nanoparticles. The formation of the hausmannite Mn(3)O(4) and bixbyite Mn(2)O(3) structures was clearly confirmed by XRD. The surface structures of MnO(x) were also determined by LRS, XPS, and TPR. The crystalline phases of MnO(x) were identified by LRS with corresponding out-of-plane bending and symmetric stretching vibrations of bridging oxygen species (M-O-M) of both MnO(x) nanoparticles and bulk MnO(x). We also observed the terminal Mn=O bonds corresponding to vibrations at 940 and 974 cm-1 for Mn(3)O(4)/SBA-15 and Mn(2)O(3)/SBA-15, respectively. These results show that the MnO(x) species to be highly dispersed inside the channels of SBA-15. The nanostructure of the particles was further identified by the TPR profiles. Furthermore, the chemical states of the surface manganese (Mn) determined by XPS agreed well with the findings of LRS and XRD. These results suggest that the method developed in the present study resulted in the production of MnO(x) nanoparticles on mesoporous silica SBA-15 by controlling the crystalline phases precisely. The thus-prepared nanocomposites of MnO(x) showed significant catalytic activity toward CO oxidation below 523 K. In particular, the MnO(x) prepared from manganese acetyl acetonate showed a higher catalytic reactivity than that prepared from Mn(NO(3))2.

Supported Pd, Au, and Pd−Au alloy catalysts are characterized with in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption (DRIFTS), quantitative powder X-ray diffraction, and X-ray photoelectron spectroscopy. The spectroscopic results presented in the paper demonstrate the existence of electron density transfer between Pd and Au atoms in alloy surfaces. In particular, the modification of the Pd electronic structure by the addition of Au is confirmed probably for the first time by the DRIFT spectra. The relationship between surface composition and catalyst performance in the synthesis of hydrogen peroxide directly from hydrogen and oxygen was established. Preliminary results indicate that the activity and selectivity of Pd−Au alloy catalysts can be significantly enhanced through adjusting the surface structures by changing the Au content in alloys.

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Using a mixture of cetyltrimethylammonium bromide and carboxylate anionic surfactant (C n H2 n +1COONa, n = 11, 13, 15, 17) as templates, siliceous MCM-48 is synthesized with low molar ratio (0.168:1) of mixed surfactants to silica and low concentration (5 wt %) of mixed surfactants.

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For the first time, the intercalation properties of acid-activated montmorillonites treated at different acid/clay (w/w) ratios with a cationic surfactant cetyltrimethylammonium (C16TMA) hydroxide are reported. The acid activation causes a reduction in the number of cation exchange sides and, hence improves the exfoliation of the silicate sheets at higher pH values. The basal spacing increases significantly from 1.54 to 3.80 nm, and is related to the acid activation extent. The acid activated clays with acid/clay ratios above 0.2 intercalated significant amounts of C16TMA cations with a basal spacing of 3.8 nm compared to the non acid activated montmorillonite with a basal spacing of 2.10 nm. The 13C CP/MAS NMR indicates that the intercalated surfactants exhibit a significant degree of gauche conformation in the acid-activated clays. According to in-situ powder XRD, an increase of the basal spacing to 4.08 nm is observed at intermediate temperatures of 50-150 degrees C for organoclay with basal spacing of 3.80 nm, at higher temperatures above 300 degrees C, the decomposition of the surfactant occurs and the basal spacing decreases to a value of about 1.4 nm, with the persistence of a reflection at 3.8 nm for clay at a higher acid/clay ratio of 0.5.

Catalytic properties of Au nanoparticles supported on a one-dimensional γ-Al2O3(1-D) nanofiber and commercial γ-Al2O3 have been investigated during CO oxidation at low temperatures (298∼373 K). The kinetic data showed that the activity of Au catalysts could be remarkably improved by using γ-Al2O3 nanofibers as support compared to the commercial γ-Al2O3. The measured turnover of frequency (TOF) and apparent activation energy (Ea) at room temperature were 0.25 s-1 and 2.7 kJ/mol, respectively, for the Au/γ-Al2O3-nanofibers catalyst (Au-AF), while those for the Au/γ-Al2O3-commercial catalyst (Au-AC) were 0.07 s-1 and 23.7 kJ/mol, respectively. To our knowledge, the Au-AF catalyst developed in this study is the most active alumina supporting Au catalysts ever reported. X-ray diffraction (XRD) results verified that the alumina nanofibers consist of solely γ-type; meanwhile, a transition from γ- to δ/θ-type was identified for the commercial alumina. The results of transmission electron spectroscopy (TEM) and XRD obtained from the fresh and spent catalysts revealed that the size distribution and morphology of Au particles were independent of the nature of alumina. Also, the X-ray photoelectron spectroscopy (XPS) spectra showed that the catalyst surface was predominant with metallic Au species, which were slightly negatively charged because of interacting with γ-Al2O3 matrix. However, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in the region of 3800−3000 cm-1 showed that the OH groups bonded to both γ-Al2O3 surfaces were quite different. In particular, the surface Al atoms of the nanofibers are supposed to be highly isolated; they probably favor the creation of small Au clusters, which have more step/edge sites at interface compared to that for the Au-AC considering the different kinetic behaviors for both catalysts. DRIFTS recorded from the oxidation and adsorption of CO further suggests that the OH groups linking to Au and alumina on the surface of Au-AF may involve the CO oxidation. It is confirmed that a tiny modification of the structure of γ-Al2O3 matrix may have strong influence on the structure and activity of the Au nanoparticles.