Preparation of γ-Fe2O3@C@MoO3 core/shell nanocomposites as magnetically recyclable catalysts for efficient and selective epoxidation of olefins

Abstract

Magnetic γ-Fe2O3@C@MoO3 core-shell structures were fabricated via a general approach and characterized by several techniques such as XRD, XPS, ICP-AES, Raman etc. The catalytic performance of them has been demonstrated in heterogeneously catalyzed oxidation of cyclooctene with tert-butyl hydroperoxide (tBuOOH) as an oxidant, and high conversion (100%) and selectivity (over 99%) were achieved with relatively low catalyst dosage under mild conditions. It should be emphasized that the hybrid catalyst could be easily separated by an external magnet and reused up to 9 times with no significant loss of activity and selectivity. The reaction mechanism over MoO3 is also discussed on the basis of the FTIR and XPS measurements. It is suggested that the high catalytic activity is related to the formation of the transition state, a Mo-alkyl peroxide and olefin complex, which is beneficial for an efficient oxygen atom transfer by converting the intermolecular process directly into an intramolecular process.

Corrosion Behavior of Structural Materials in LiCl-KCl Molten Salt by Thermogravimetric Study

“…The LRS spectrum of SS410 (Figure 7[a]) consisted of peaks corresponding to α-Fe 2 O 3 , γ-Fe 2 O 3 , and Fe 3 O 4 along with the spinel FeCr 2 O 4 . [21][22][23][24][25][26] When the measurements were repeated at other locations as shown in Figure 7(b), the Raman bands appeared at 454 and 588 cm -1 in all the samples and these were assigned to Eg and A1g vibrations of LiCrO 2 . 27 A broad peak appeared at around 700 cm -1 in all the samples, and this peak corresponds to the Fe-Cr spinel.…”

“…The Raman peaks were assigned based on the Raman data published in literature. [21][22][23][24][25][26][27] The Raman spectrum of 9Cr-1Mo steel (Figure 7[a]) exhibited dominant peaks at 228, 290, 403, and 1,300 cm -1 corresponding to the alpha phase of Fe 2 O 3 , [21][22][23] and the peaks at 504, 585, and 690 cm -1 correspond to the gamma phase of Fe 2 O 3 . 24-25 A broad peak at 690 cm -1 was attributed to FeCr 2 O 4 spinel phase 26 and the broad signature was due to the overlapping of the spinel phase with γ-Fe 2 O 3 .…”

Three-Dimensional Nanoarchitecture of BiFeO3 Anchored TiO2 Nanotube Arrays for Electrochemical Energy Storage and Solar Energy Conversion

“…Besides these, two tiny satellite peaks can also be observed at the binding energies of 714.2 and 719 eV, redefining the electronic structure of Fe 3+ . Moreover, there is no sign of the Fe 2+ related peaks (at 709.5 eV for Fe 2p 3/2 and 716 eV for Fe 2p 1/2 ) which again confirms the presence of only trivalent oxidation state of iron in BFO 34,35. The XPS analysis indicates that only pure BiFeO 3 phase is present without any type of impurities.…”

“…725 eV, respectively, correspond to the trivalent oxidation state of iron in BiFeO 3 34,35. Besides these, two tiny satellite peaks can also be observed at the binding energies of 714.2 and 719 eV, redefining the electronic structure of Fe 3+ .…”

Recent Advances in Facile Liquid Phase Epoxidation of Light Olefins over Heterogeneous Molybdenum Catalysts

“…The catalyst was active for epoxidation of various olefins [cyclopentene (Y=70.8 %), cyclohexene (Y=90.1 %), cyclooctene (Y=98 %), 1‐octene (Y=54 %), 1‐dodecene (Y=49 %), styrene (Y=67.9 %), limonene (Y=86.5 %), Table S1, #86‐92] and can be recycled at least five times without appreciable loss of catalytic activity. Similarly, Zhang et al . fabricated magnetic γ‐Fe 2 O 3 @C@MoO 3 core‐shell structures.…”