Cover Feature: Roles of Enhancement of C−H Activation and Diminution of C−O Formation Within M1‐Phase Pores in Propane Selective Oxidation (ChemCatChem 3/2021)

Abstract

The Cover Feature shows sequential conversions of propane to propene and acrolein inside one‐dimensional pores of M1 phase MoVTeNb mixed oxide. In their Full Paper, Y. Liu, A. Twombly et al. show that the pores tightly confine linear alkanes and alkenes and enhance rates of C−H activations via van der Waals stabilization, but steric hindrance to forming C−O bonds at the M‐O‐M bridging lattice O‐atoms accessible within these pores diminishes O‐insertion near C=C bonds in alkenes. This C−H activation enhancement and C−O formation diminution together improves selectivity to dehydrogenation and allylic oxidation products. More information can be found in the Full Paper by Y. Liu, A. Twombly et al.

Recent Advances in Tetra- (Ti, Sn, Zr, Hf) and Pentavalent (Nb, V, Ta) Metal-Substituted Molecular Sieve Catalysis

“…As discussed above for ethane ODH, the ratios between the activation rates of propane and cyclohexane over these MoVTeNbO catalysts are nearly an order of magnitude higher than those over VO x /SiO 2 . Once again, these results suggest that micropore sites of the M1 phase significantly contribute to propane activation since both molecules (propane and cyclohexane) are activated in a homologous C–H activation rate-limiting reaction step …”

“…Thus, pore confinement effects and framework structures can be used to assess selectivity limitations in selective hydrocarbon oxidations involving complex networks of sequential and parallel steps. 262 Similar shape selectivity studies in selective oxidations have been performed with microporous manganese oxide systems, some of which doped with vanadium. 263 More specifically, various octahedral molecular sieve (OMS) systems with channels consisting of edge-shared MnO 6 octahedra of different sizes (OMS-1, OMS-2, OMS-5, and OMS-6) were tested for ethane and cyclohexane ODH and compared with commercial manganese (MnO), MoVTeNb (M1), and vanadium (V 2 O 5 ) oxides.…”

“…Porous M1 phase MoVTeNb mixed oxide catalysts have been applied in propane and propylene oxidations to acrolein and acrylic acid . The ability of reactants to enter internal catalytic sites in heptagonal pores of these oxides was monitored using probes of different sizes, and the elementary steps were analyzed considered selectivity limitations.…”

“…Yet, less desirable oxygenate formation is limited by C–O bond formation, which also has a considerably higher activation barrier than C–H activation as such reactions occur inside the micropores. Thus, pore confinement effects and framework structures can be used to assess selectivity limitations in selective hydrocarbon oxidations involving complex networks of sequential and parallel steps …”

Cucurbit[7]uril as Nanoreactor for the Fixation of CO2 with Oxirane: A Density Functional Theory Investigation

“…Moreover, confinements have been considered a powerful tool among researchers to modify the structure, electronic properties and efficiency of the catalyst. Also, confinement (or confined) catalysis has gained vast interest in heterogeneous catalysis as it influence the reactivity [25–47] . Presently, confined catalysis has been widely used for the catalytic conversion of CO 2 into useful chemicals [48–51] .…”