A pulsed isotope exchange technique was applied to study the oxygen scrambling activity of polycrystalline calcium oxide under temperatures and pressures relevant for the oxidative coupling of methane (OCM). Oxygen exchange was observed above 400 °C. The onset was attributed to the removal of impurities on the catalyst surface. By trapping impurities in the gas feed, the scrambling could already be observed at room temperature. An activation energy of 80 kJ/mol was determined for the oxygen scrambling of O2 on the surface of polycrystalline CaO powder in absence of other gases. Presence of water and carbon dioxide shift the onset of the reaction to higher temperatures and increase the activation energy significantly to 110 and 150 kJ/mol, respectively. The OCM activity could be directly linked to the oxygen scrambling activity of the material in pulsed OCM operation. It is proposed that the same sites are responsible for oxygen scrambling and OCM reaction and that the rate is dictated by desorption of CO2 and H2O. The high reaction temperatures in OCM in case of CaO are only required to regenerate the active sites, which may apply to basic OCM catalysts in general. In situ Raman and thermogravimetric experiments verified the formation of a bulk calcite phase below 750 °C, which is inactive in OCM and oxygen scrambling. Above 750 °C no surface oxygen species or adsorbates were found by Raman spectroscopy suggesting that only surface defects are responsible for catalytic activity of CaO.

More than 1,000 CO2 chemistry publications within the last five years have featured the application of bifunctional catalysts. The majority of these articles investigate hydrogenation reactions of CO2 for producing...

An iridium pincer complex {p-KO-C 6 H 2 -2,6-[OP(t-Bu) 2 ] 2 }Ir(C 2 H 4 ) is immobilized in a propyl bromide-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The support material enables the formation of isolated active metal sites embedded in a chemically robust and highly hydrophobic environment. The catalyst maintained high porosity and -without prior activation -exhibited high activity in the continuous-flow dehydrogenation of cyclohexane at elevated temperatures. The catalyst shows a stable performance for at least 7 days, even when additional H 2 O was co-fed, owing to its hydrophobic nature.

A novel CO2 utilization technology allows for the inclusion of CO2 as carbonate units and double bond moieties to give additional functionality in polyether polyols. This study examines the chain‐elongation kinetics of these diols with diisocyanates to polyurethane rubbers by means of thermal analysis. A reaction order of 1 indicates a strong influence of the chains' mobility on the reaction rate. Spectrometry and comparison with non‐double‐bond polyols reveal that the effect cannot be attributed to a substantial occurrence of side reactions but is rather due to the intertwining of lengthy chains.