Facile Synthesis of Micro-Mesoporous Copper Phyllosilicate Supported on a Commercial Carrier and Its Application for Catalytic Hydrogenation of Nitro-Group in Trinitrobenzene (original) (raw)
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Environmental Engineering and Management Journal
Copper nanoparticles were successfully synthesized on polyether-functionalized mesoporous silica to investigate the effect of metal loading (10, 25 and 35 wt. % Cu) on their structural and catalytic properties. The oxide forms of these nanocomposite materials were thoroughly characterized by nitrogen physisorption, SAXS, WAXS, TEM, EDXS, and TPR, whereas the metallic forms were analysed by N 2 O chemisorption. The results indicated that the mesostructured SBA-15-like hybrids favoured the generation of highly dispersed supported copper nanoparticles with average sizes in the range of ~2-6 nm, displaying excellent activity in the hydrogenation of cinnamaldehyde. The average particle size was shown to increase with the metal loading. Among the tested catalysts, the highest activity was obtained for the sample having 25 wt. % Cu (total conversion of cinnamaldehyde in 150 min of reaction). All the catalysts exhibited high selectivity towards hydrocinnamaldehyde (> 85 mol %), which did not appear dependent on the copper particle size.
Applied Catalysis A: General, 2011
Copper modifications of ordered mesoporous materials with different pore topology (SBA-15 and KIT-6) were prepared by incipient wetness impregnation and "chemisorption-hydrolysis" methods and further oxidative or consecutive oxidative/reductive treatment. The samples were characterized by nitrogen physisorption, XRD, XPS, FTIR, UV-vis and TPR-TG techniques. The ordered structures and the "chemisorption-hydrolysis" post synthetic method provide the formation of homogeneously dispersed in the mesopores copper species. The "chemisorption-hydrolysis" modification of the silicas with more opened 3D ordered structure (KIT-6) provides the formation of highly active catalysts, but their activity could be easily suppressed after the treatment under the reduction medium.
Applied Surface Science, 2018
The room temperature synthesis of copper (Cu) nanoparticles (NPs) supported within SiO 2 mesoporous thin films (MTF) modified with either COOH or NH 2 functional groups is reported. The functional groups present in the MTF surface acted as adsorption sites for Cu (II) ions, which were afterwards reduced to Cu NPs in presence of sodium borohydride at room temperature. The oxidation state of the copper NPs, corroborated by X-ray Photoelectron Spectroscopy and Electron Energy Loss Spectroscopy, was strongly dependent on the functional group present in the pores of the MTF and on the number of adsorption/reduction (A/R) cycles applied for NPs loading. Metallic Cu (0) NPs were obtained in MTFs displaying COOH groups applying 10 A/R cycles while NPs with higher oxidation state were as well present after 20 A/R cycles. For MTF functionalized with NH 2 groups the copper is present as Cu (I) and Cu(II) in the NPs but no Cu (0) can be detected. The MTF-Cu(CuOx) composite materials were tested as catalysts for the reduction of 4-nitrophenol in the presence of NaBH 4. Catalytic activity of composite materials depends on the oxidation state of Cu NPs, being more active those samples containing Cu (0) NPs, synthesized from COOH functionalized MTFs.
Nanomaterials
Cu2O/CuO nano-architectures were prepared by biogenic-mediated synthesis using pomegranate seeds extract as the reducing/stabilizing mediator during an aqueous solution combustion process of the Cu2+ precursor. The fabricated Cu2O/CuO nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and nitrogen sorption. Nitrobenzene (NB) was applied a probe to test the catalytic activities of the fabricated Cu2O/CuO nanocomposite. The results indicated that pomegranate seeds extract (PSE) manifest Cu2O/CuO NPs of tiny particle size, larger pore volume and greater surface area compared to the bulky CuO synthesized in the absence of PSE. The surface area and total pore volume of Cu2O/CuO NPs were 20.1 m2 g−1 and 0.0362 cm3 g−1, respectively. The FESEM image shows the formation of broccoli-like architecture. The fabricated Cu2O/CuO nanocomposite posse...
This investigation focused on developing an environmentally benign approach to synthesis of nanostruc-tured Cu/SiO 2 catalysts for hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). It was accomplished by using (NH 4) 2 CO 3 , instead of the conventional ammonia evaporation method, for making nanostructured Cu/SiO 2 exhibiting good performance for DMO conversion and EG selectivity in the desired temperature range, with increased temperature stability. The resulting catalysts were characterized for catalytic activity, optimal reaction temperature, specific surface area, crystalline structure, surface composition and the influence of sodium in support raw material. The new method generated active catalysts with improved thermal stability linked to better dimension control and more Cu 2 O content, together with improved morphology of the supported copper particles.
Catalysis Today, 2022
Cu/SiO2 catalysts prepared by a deposition-decomposition (DD) method using ammonium hydroxide are currently among the most promising catalysts for oxalates hydrogenation to ethylene glycol (EG). Here, a Cu/SiO2 catalyst prepared by the DD method was pre-reduced at a) 200-350 °C in 100% H2, and 2) 200°C in a 50% H2/N2 mixture. Then, it was tested at 200 °C, and 25 barg, while EG yields were optimized, with H2-GHSV and H2/DMO ratios in the ranges 1000-4000 h-1 and 30-200 mol/mol. The calcined catalyst presents an XRD amorphous Cu phyllosilicate phase. After pre-reduction in pure H2 at 200 to 250°C (Tred), the Cu metallic surface area increased from 6 to 12 m 2 /gcat and slightly decreased at 350°C. Simultaneously, the silanol's band, measured by DRIFT experiments, increased with Tred. The highest ethylene glycol yield (91 %) was achieved after pre-reduction at 200 °C in pure hydrogen, working with an H2-GHSV and H2/DMO of 1050 h-1 and 68 mol/mol, respectively. The catalyst was stable for more than 36 h after a 20 h induction period. Catalyst characterization results as a function of Tred confirm that mixed-valence copper nanoparticles favor the EG selective formation, while side reactions leading to ethanol and 1,2-butanediol are related to exposed acidic and basic sites due to decreased Cu/support interactions.
Research on Chemical Intermediates, 2018
Supported copper catalysts on low surface area silica were prepared by several methods and characterized by AAS, XRD, N 2 adsorption, SEM, H 2-TPR, N 2 O titration, TGA-DTA, UV-Vis techniques. Their hydrogenating properties were examined in the gas-phase hydrogenation of benzaldehyde. The analysis of characterization results revealed that the choice of preparation method affected the texture, composition, and structure of the calcined and reduced Cu/SiO 2 catalysts. The dispersion and size distribution of copper species was present in different forms in the catalysts that exhibited low specific surface areas. In gas-phase hydrogenation of benzaldehyde to benzyl alcohol, the catalysts tested at the reaction temperatures of 160 and 200°C were stable and conducted to a good catalytic activity and benzyl alcohol selectivity ranging between 5 and 39 lmol min-1 g-1 and 0-95%, respectively. The activity of the catalysts in gas-phase hydrogenation also depended on the particle size and the nature of copper species formed on low surface area silica.
Study on the Catalytic Properties of Silica Supported Copper Catalysts
Procedia Engineering, 2013
The mesoporous silica (MS) supported copper catalysts containing 2 wt. % copper in finely dispersed form were synthesized and characterized. A comparative study on the effect of calcination temperature and reduction of the supported metal on catalytic property of supported copper species was carried out. The loading of copper on the supports provides good reducibility and catalytic activity for dehydrogenation of benzyl alcohol. The acidity and copper ions in mesoporous silica supported copper sample showed good activity in catalytic transformations of benzyl alcohol.
Naturally-Occurring Silicates as Carriers for Copper Catalysts Used in Methanol Conversion
Clays and Clay Minerals, 1992
Almtract-Bentonite-and sepiolite-supported copper catalysts have been prepared either by adsorption of Cu(II) from aqueous solutions of copper nitrate at pH ~4.5 or by adsorption ofa [Cu(NH3)4] 2+ complex from an ammonia solution of CuSO4 at pH ~ 9.5. The structure and composition of the calcined preparations have been studied by X-ray diffraction, chemical analysis, and energy dispersive X-rays. Textural characteristics have derived from the analysis of the adsorption-desorption isotherms of N2. All catalysts have been tested for the dehydrogenation of methanol to methyl formate. For this reaction, bentonitebased catalysts were found to have very little activity, which indicates that copper located in the interlamellar spaces is inaccessible to methanol molecules. On the contrary, copper-sepiolite catalysts showed a very high specific activity even for those catalysts with a very low copper content. The chemical state of copper in the catalysts on-stream has been revealed by X-ray photoelectron spectroscopy and X-rayinduced Auger techniques. In most of the catalysts Cu + is the dominant copper species.
Journal of Colloid and Interface Science, 2016
SBA-15 modified with APTMS (3-aminopropyl trimethoxysilane) having pore diameter (~8 nm) has been synthesized and impregnated with 1-10 wt. % Cu using Cu(NO 3) 2 as a metal source followed by calcination at 350 o C. As-prepared CuO/ap-SBA-15 powder showed changes in the color from white for bare SBA-15 to light green due to formation of anisotropic CuO nanoparticles that exhibited a characteristic plasmon absorption band at 359 and 747 nm. TEM studies showed a change in the morphology of CuO NPs as a function of increased Cu loading. Moreover, well dispersed CuO nanospheres (~5-6 nm) and nanorods (aspect ratio ~11-20 nm) having monoclinic crystal phase were observed within the mesoporous channels of SBA-15. Elemental mapping studies confirmed uniform distribution of CuO nanoparticles on the surface of SBA-15. An increase in surface area was also observed from 694 m 2 g-1 for SBA-15 to 762 m 2 g-1 for 10 wt. % Cu loading probably due to the deposition of excess of CuO nanoparticles on the outer siliceous surface. The catalytic activity also increased with Cu loading and 10 wt. % CuO/ap-SBA-15 catalyst displayed the highest catalytic activity for the reduction of m-chloronitrobenzene and m-nitrotoluene with 83 % and 100 % selectivity for mchloroaniline and m-aminotoluene respectively.