Selective Oxidation of Alkenes over Uranyl-Anchored Mesoporous MCM-41 Molecular Sieves

Abstract

Uranyl-anchored MCM-41 (UO2 2+/MCM-41) catalysts were prepared hydrothermally and systematically characterized employing various analytical and spectroscopic techniques: namely, X-ray diffraction (XRD), nitrogen sorption isotherms, transmission electron microscopy (TEM), electron diffraction (ED), and thermogravimetry−differential thermal analysis, inductively coupled plasma-atomic emission spectroscopy, diffuse reflectance ultraviolet−visible (DRUV−vis) spectroscopy and fluorescence spectroscopy, and Fourier transform-intrared (FT-IR) spectroscopy. XRD confirms the incorporation of uranyl ions into the silicate matrix and that TEM and ED investigations corroborate the highly ordered structure of uranyl-incorporated MCM-41. Further, these findings were well supported by DRUV−vis, fluorescence, and FT-IR spectra, indicating the nature of uranyl ion species as well as their interaction with the silicate framework. Well-characterized, high-quality UO2 2+/MCM-41 catalysts were employed for the liquid-phase allylic oxidation of α-pinene, β-pinene, and cyclohexene under moderate reaction conditions using various solvents and oxidants. Under the optimized experimental conditions, the catalysts showed high substrate conversion and excellent product selectivity. In addition, the influence of various other parameters (viz., temperature, time, recyclability, uranium content, etc.) were also performed.

Synthesis and characterization of indium and thallium immobilized on isonicotinamide‐functionalized mesoporous MCM‐41: Two novel and highly active heterogeneous catalysts for selective oxidation of sulfides and thiols to their corresponding sulfoxides and disulfides

“…The sharp diffraction peak can be attributed to (100), and the two weaker diffraction peaks can be attributed to (110) and (200) reflections, as shown in Figure . These peaks are typically characteristic of a two‐dimensional hexagonal MCM‐41 structure . After functionalization of MCM‐41, the sharp diffraction peak is still seen in the XRD patterns of MCM‐41‐INA‐In and MCM‐41‐INA‐Tl, which clarifies the preservation of the hexagonal structure in these samples.…”

Kinetic study of α-pinene allylic oxidation over FePcCl16-NH2-SiO2 catalyst

“…Verbenone has been obtained using homogeneous and heterogeneous catalysts with moderate yields (Table 1) [14,15]; however, the requirement of expensive and toxic solvents [16][17][18][19], difficulty in catalyst recovery and product purification [20], inert atmosphere or large amount of catalyst and time, limit the application in some of those systems. Furthermore, in some cases reports do not include catalytic stability [21].…”

“…When α-pinene oxidation reaction was carried out without TBHP (with or without catalyst), low α-pinene conversion (2.4%) at 23 h was obtained because of the presence of O2 in the reaction media (curve R-3 and R-4 in Fig. 9), α-pinene epoxide was detected with a selectivity of 28.3 %, and allylic products verbenone and verbenol with selectivities of 19.6% and 14.3%, respectively. The oxidation carried out without catalyst, but in presence of TBHP increased α-pinene conversion up to 20.5% at 23 h, (curve R-2 in Fig.…”

Novel access to verbenone via ruthenium nanoparticles-catalyzed oxidation of α-pinene in neat water

“…-Scheme 1 -Up to now, various catalytic systems, either molecular complexes [16][17][18][19][20] or heterogeneous catalysts [21][22][23][24][25][26][27][28][29][30][31][32], have been used to produce verbenone. Nevertheless, in the most cases, low to medium yields were obtained ( Figure 1) or most of these processes still suffer from various drawbacks, such as sophisticated catalytic systems, toxic organic solvents and high amounts of oxidants, long reaction times, and difficult catalyst's recovery.…”