scholarly journals Fine Crystalline Mg-Al Hydrotalcites as Catalysts for Baeyer-Villiger Oxidation of Cyclohexanone with H2O2

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1493
Author(s):  
Robert Karcz ◽  
Bogna D. Napruszewska ◽  
Alicja Michalik ◽  
Joanna Kryściak-Czerwenka ◽  
Dorota Duraczyńska ◽  
...  

The catalytic activity of Mg-Al hydrotalcite (HT) materials in base-catalyzed reactions is known to be promoted by the low crystallinity of the HT solid. In the present work, two routes enabling the preparation of finely crystalline Mg-Al HT materials were explored: (1) the inverse microemulsion technique, and (2) co-precipitation in the presence of starch. Carbonate, chloride and bromide forms of HT were prepared, examined with X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and infrared spectroscopy, and used as catalysts in the Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone with a H2O2/acetonitrile system. The bromide forms proved significantly less active than the chlorides and carbonates, as they promoted nonselective consumption of H2O2. The fine crystalline materials were more active than the more crystalline HT references obtained by conventional co-precipitation. Catalysts prepared by inverse microemulsion were less crystalline and more active than the starch-templated ones, but suffered stronger deactivation by the acidic reaction environment. Alkalization of the reaction medium with NaHCO3 stabilized the HT materials and increased the ε-caprolactone yield, which became comparable for both types of fine crystalline catalysts—thus pointing to the synthesis involving a simple and cheap starch templating approach as being a particularly attractive one.

2013 ◽  
Vol 838-841 ◽  
pp. 2306-2309
Author(s):  
Guang Hua Wang ◽  
Kun Chen ◽  
Wen Bing Li ◽  
Dong Wan ◽  
Qin Hu ◽  
...  

Magnetic modified organobentonite (Fe3O4/CTAB–Bent) was synthesized by chemical co-precipitation method in which CTAB–Bent was firstly achieved via ion–exchange.The composite materials have been characterized by powder X–ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and Scanning electron microscopy (SEM) . The results revealed that basal spacing of bentonite was increased through organic modification and the Fe3O4 particles synthesized which covering the surfaces of bentonite .Compared with natural bentonite, the adsorption capacity of Fe3O4/CTAB–Bent for Orange II was greatly enhanced and can be easily separated from the reaction medium by an external magnetic field after the treatment.


2008 ◽  
Vol 54 ◽  
pp. 50-55
Author(s):  
Erika Furlani ◽  
Eleonora Aneggi ◽  
Stefano Maschio

The present research compares properties and behaviour of co-precipitated 3Y-PSZ powders submitted, after co-precipitation, to different milling treatments. The characteristics of the different products were evaluated by measurement of particle size distribution, thermogravimetric analysis, X-ray diffraction, specific surface area and scanning electron microscopy analysis. It has been demonstrated that 1h of attrition milling enables the production of powders with micrometric particles: the dispersing liquid used on milling has little influence. Crystallization of the amorphous powder is achieved after 1h of high energetic milling, without any thermal treatment.


2014 ◽  
Vol 25 (1) ◽  
pp. 43-46
Author(s):  
Cristina Ileana Covaliu ◽  
Gina Alina Traistaru ◽  
Gigel Paraschiv

Abstract Methane oxidation using different catalysts is an useful process for preventing air pollution. This study presents the methane oxidation by two types of catalysts: Pd-Sn/Al2O3 and spinel mixed oxide, CuFe2O4. The Pd-Sn/Al2O3 was successfully prepared by sol-gel method and CuFe2O4 by co-precipitation method. The catalysts obtained have been characterized structurally, morphologically and texturally by X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area (BET). The catalytic activity tests regarding methane oxidation were also performed.


2011 ◽  
Vol 675-677 ◽  
pp. 57-60
Author(s):  
Yuan Sun ◽  
Xiu Juan Zhao ◽  
Rui Ming Ren

The olivine-type LiFePO4 powder was prepared by a chemical method using the synthesized FePO4⋅2H2O, LiOH and glucose as raw materials. The synthesized FePO4⋅2H2O powder was obtained by co-precipitation method. FePO4⋅2H2O and LiFePO4 powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the synthesized FePO4⋅2H2O powder at pH of 2.05 was in a single phase and nearly spherical in shape. Using the synthesized powders to prepared LiFePO4 at 600 °C in vacuum for 2 h was nearly spherical in shape and whose size was in the range of 0.1-0.5μm.


2011 ◽  
Vol 675-677 ◽  
pp. 77-80 ◽  
Author(s):  
Hai Li Jing ◽  
Guo Jun Li ◽  
Rui Ming Ren

Nano-sized precursor FePO4·xH2O particles were obtained by oxidation co-precipitation using FeSO4⋅7H2O, H2O2 and ammonia. The powder was characterized by differential thermal analysis (DTA) and thermogravimetry (TG), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The TG-DTA results determined the content of crystal water of FePO4·xH2O, i.e. x = 1.5. The SEM observation suggested that FePO4·xH2O particles were spherical in shape and its grain size was about 150 nanometers. The dispersion of the synthesized powder was improved through the addition of surfactant. The XRD analysis indicated that the synthesized FePO4·xH2O was amorphous. After being calcined at 720 °C for 10 hrs, the synthesized FePO4·xH2O at pH of ~3.5 was crystallized and FePO4 in a single phase was obtained. According to the test results, the optimized preparation process parameters were determined.


1991 ◽  
Vol 249 ◽  
Author(s):  
Amita Pathak ◽  
P Pramanik

ABSTRACTA new co-precipitation technique for the preparation of fine ceramic mixed-oxide povders using a mixture of (NH4)HCO3, triethylamine and formaline in presence of soluble polymers, like polyvinyl alcohol (PVA). The mixture is chemically equivalent to one mole of triethylamnroniumcarbonate (TEAC). The mixed-oxide ccmpositions synthesized and characterized are - MN2O4 [Spinels; where M = Ni(II), Cu(II), Zn(II), Co(II) and N = Fe(III), tr(III)]; M3Fe5O12 [Garnets; where M = Y(III), Gd(III)] and RBa2Cu3O7+δ [Ceramic superconductors; where R = rare-earths]. The final product is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy for microanalysis (EDX) and scanning electron microscopy (SEM).


2017 ◽  
Vol 14 (2) ◽  
pp. 116-122 ◽  
Author(s):  
Saima Wani ◽  
Hasham S. Sofi ◽  
Faheem A. Sheikh ◽  
S. A. Shivashankar ◽  
Shafquat Majeed

Nanocrystalline ZnGa2O4 spinel powders were prepared through a simple and facile microwave-irradiation assisted solution-based route, using ethylene glycol as the reaction medium and, without using any structure-directing agents. The as-prepared product consists of ZnGa2O4 nanoparticles, which are crystalline as revealed by X-ray diffraction studies and TEM analysis. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies also show that, the size of these as-prepared nanoparticles is less than 10 nm. The annealed nanopowders show intense blue luminescence, under UV excitation, which makes these nanopowders important in the field of phosphor applications.


2012 ◽  
Vol 581-582 ◽  
pp. 292-296 ◽  
Author(s):  
Guang Hua Wang ◽  
Yun Zhou Lu ◽  
Wen Bing Li ◽  
Xue Qin Liu ◽  
Ming Dong Sun

Al-pillared bentonite supported Fe3O4 nanoparticles were prepared by co-precipitation and characterized with X-ray diffraction (XRD), specific surface area (BET) and scanning electron microscopy (SEM). The supported Fe3O4 nanoparticles exist on the surface of clays, with better dispersing and no obvious aggregation than the ones without bentonite support. Batch tests were carried out to investigate the catalytic oxidation Orange II by the obtained heterogeneous catalysts. The effect of pH, temperature and initial H2O2 concentration on degradation was discussed, and the regeneration ability of catalyst was also studied.


2011 ◽  
Vol 311-313 ◽  
pp. 1294-1299 ◽  
Author(s):  
Liang Zheng ◽  
Hui Zheng ◽  
Jiang Xia Deng ◽  
Zhi Hua Ying ◽  
Jun Wu ◽  
...  

Single-phase nanocrystalline YIG powders have been successfully synthesized through chemical co-precipitation methods. The influence of pH value of the precursor solution and calcinating conditions (temperatures ranging from 700 to 900°C and times ranging from 0.5 to 12 hours) on the purity and grain size of the single-phase nanocrystalline YIG powders were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) technique. The results show that a pure single-phase YIG powder was obtained as the pH value of precursor solution above 10 and the YIG grain grows bigger as calcinating temperature and time increased. Finally, the optimal condition to form single-phase nanocrystalline YIG with the smallest grain size is calcinating at 750°C for 7 hours.


2018 ◽  
Vol 936 ◽  
pp. 53-57
Author(s):  
Bheechanat Duangdee ◽  
Dussadee Rattanaphra ◽  
Anusith Thanapimmetha ◽  
Maythee Saisriyoot ◽  
Penjit Srinophakun

This work presents the synthesis and characterization of mixed rare earths hydroxide heterogeneous catalyst. The catalysts were prepared by co-precipitation of mixed rare earths with NaOH at different pH (6, 7 and 12). The prepared catalysts were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDS). The XRF results showed that the catalyst composed of cerium (Ce), neodymium (Nd), lanthanum (La), praseodymium (Pr) and samarium (Sm) being predominant at pH up to 7. Particularly, cerium (Ce) was favorable precipitation at pH 7. This results were confirm by SEM-EDS. The Ce (OH)3 phase was clearly observed for the mixed rare earth catalyst precipitated at pH 7. The XRF, SEM-EDS and XRD results were consistency.


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