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Insertion of MoO 3 oxide in the mixed borophosphate glass network has been analyzed for the first time by advanced magnetic resonance spectroscopies. For the first time, the xMoO 3 -(100x)(50PbO-10B 2 O 3 -40P 2 O 5 ) composition line has been investigated by 1D ( 11 B, 31 P, 95 Mo) and 2D-correlation NMR ( 11 B DQ-SQ, 11 B( 31 P) D-HMQC) at high magnetic field (18.8 T). The set of data allowed for analyzing both local and medium range orders and identifying the modifications in the BOB and/or BOP mixing induced by the MoO 3 insertion. In a second step, continuous wave EPR has been used to detect the presence of Mo 5+ ions, resulting from partial reduction of Mo 6+ during the melting stage, and the chemical environment around the Mo 5+ species has been documented for the first time by pulsed EPR technique (HYSCORE). Altogether, the data contribute to a better understanding of the glass network modifications induced by the MoO 3 insertion, including the nonlinear evolution of the glass transition temperature that has been explained by a modification of the glass network nature.

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Direct functionalization of methane selectively to value-added chemicals is still one of the main challenges in modern science. Acetic acid is an important industrial chemical produced nowadays by expensive and environmentally unfriendly carbonylation of methanol using homogeneous catalysts. Here, we report a new photocatalytic reaction route to synthesize acetic acid from CH 4 and CO at room temperature using water as the sole external oxygen source. The optimized photocatalyst consists of a TiO 2 support and ammonium phosphotungstic polyoxometalate (NPW) clusters anchored with isolated Pt single atoms (Pt 1 ). It enables a stable synthesis of 5.7 mmol•L −1 acetic acid solution in 60 h with the selectivity over 90% and 66% to acetic acid on liquid-phase and carbon basis, respectively, with the production of 99 mol of acetic acid per mol of Pt. Combined isotopic and in situ spectroscopy investigation suggests that synthesis of acetic acid proceeds via a photocatalytic oxidative carbonylation of methane over the Pt 1 sites, with the methane activation facilitated by water-derived hydroxyl radicals.

The most abundant metals in heavy feedstocks, vanadium and nickel, are mainly concentrated in the asphaltenes fraction, a petroleum fraction which precipitates in presence of paraffinic solvents. Characterization of vanadium and nickel complexes is therefore important to the development of demetallation and conversion strategies used to process heavy crudes. The dependence of vanadyl structures on the geographic origin of feedstocks and their evolution during hydroprocessing in an ebullated-bed pilot unit were studied. The aim of this contribution is to assess the possibilities of the EPR spectroscopy to provide information on the structure of the vanadyl species. This work shows that pulsed EPR spectroscopy is a powerful technique that allows to distinguish several types of environments of vanadium species, amongst which are porphyrinic ligands, even in very complex samples such as C 7 asphaltenes from heavy feedstocks.

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The contribution of copper complexes of salen-based Schiff bases N, N'-bis(salicylidene)ethylenediamine (C1), N, N'-bis(4-hydroxysalicylidene)ethylenediamine (C2), and N, N'-bis(5-hydroxysalicylidene)ethylenediamine (C3) to the flame retardancy of thermoplastic polyurethane (TPU) is investigated in the context of minimizing the inherent flammability of TPU. Thermal and fire properties of TPU are evaluated. It is observed that fire performances vary depending upon the substitution of the salen framework. Cone calorimetry [mass loss calorimetry (MLC)] results show that, in TPU at 10 wt % loading, C2 and C3 reduce the peak of heat release rate by 46 and 50%, respectively. At high temperature, these copper complexes undergo polycondensation leading to resorcinol-type resin in the condensed phase and thus acting as intumescence reinforcing agents. C3 in TPU is particularly interesting because it delays significantly the time to ignition (MLC experiment). In addition, pyrolysis combustion flow calorimetry shows reduction in the heat release rate curve, suggesting its involvement in gas-phase action. Structural changes of copper complexes and radical formation during thermal treatment as well as their influence on fire retardancy of TPU in the condensed phase are investigated by spectroscopic studies supported by microscopic and powder diffraction studies. Electron paramagnetic resonance (EPR) spectroscopy was fully used to follow the redox changes of Cu(II) ions as well as radical formation of copper complexes/TPU formulations in their degradation pathways. Pulsed EPR technique of hyperfine sublevel correlation spectroscopy reveals evolution of the local surrounding of copper and radicals with a strong contribution of nitrogen fragments in the degradation products. Further, the spin state of radicals was investigated by the two-dimensional technique of phase-inverted echo-amplitude detected nutation experiment. Two different radicals were detected, that is, one monocarbon radical and an oxygen biradical. Thus, the EPR study permits to deeply investigate the mode of action of copper salen complexes in TPU.