In Situ IR Studies on the Mechanism of Dimethyl Carbonate Synthesis from Methanol and Carbon Dioxide

The synthesis of dimethyl carbonate (DMC) from methanol and Carbon dioxide (CO2) has been investigated over 5% Rh/Al2O3 catalyst. Diffuse Reflectance Infrared Fourier Transfer Spectroscopy (DRIFTS) was used to probe the reaction adsorbates which showed that activation of methanol and CO2 involves generation of intermediate methoxy species and formate ingredients, participating in elementary steps of DMC formation. Formation of DMC involves parallel routes comprising interaction of the OH group of Al2O3 through an acid/base mechanism and formate pathway with participation of metal sites. DMC in acid/base pathway is formed via methoxy species to form methoxy carbonate (CH3O)CO2 (active adsorbate), which then reacts with the methyl species to form DMC. The pathway involving metal Rh sites generates an additional elementary step for the involvement of CO2 in the reaction through active formate species. The synergy of parallel pathways determines the performance of the 5% Rh/Al2O3 catalyst. Further improvement of catalyst performance should be based on such a feature of the reaction mechanism.

AN IR AND FLOW REACTOR STUDY OF CHLOROFORM OXIDATION OVER MANGANESE OXIDES

A series of manganese base oxides (MnCe, MnZr and MnCeZr) obtained by co-precipitation, were characterized by SBET, XRD, TPR, XPS and studiedby FTIR in the oxidation reaction of a typical Cl-VOC such as chloroform, CHCl3. The oxides were compared with a manganeseoxide obtained from the recycling of spent batteries (MnOx). In addition, the catalytic combustion of CHCl3 in a fixed-bed reactor was analyzed and the CHCl3 conversion decreased in the order: MnZr > MnOx = MnCeZr >MnCe. In all cases, the conversion is higher than that obtained without a catalyst. The surface Mn4+/Mn3+ ratio would favor the decomposition of Cl-VOC. The study of CHCl3 reaction atmosphere by in situ IR reveals that in the absence of catalysts, CCl4, COCl2, C2Cl4 and CH2Cl2 were observed. On the other hand, C2Cl4 is not formed in the presence of catalysts, although CCl4 and CH2Cl2 were observed and must be avoided

In situ IR spectroscopy during oxidation process of cobalt Prussian blue analogues

Cobalt Prussian blue analogues (Co-PBA; NaxCo[Fe(CN)6]y), consisting of cyano-bridged transition metal network, –Fe–CN–Co–NC–Fe–, are promising cathode materials for Na-ion secondary batteries. In the oxidation process, oxidization of Fe and/or Co are compensated by Na+ deintercalation. Here, we investigated the oxidization process of three Co-PBAs by means of in situ infrared absorption (IR) spectroscopy. With use of an empirical rule of the frequencies of the CN− stretching mode in ferrocyanide ([FeII(CN)6]4−) and ferricyanide ([FeIII(CN)6]3−), the oxidation processes of Co-PBAs were determined against the Fe concentration (y) and temperature (T). We will discuss the interrelation between the oxidation processes and Fe concentration (y).