The elementary reactions leading to the formation of the first carbon-carbon bond during early stages of the zeolite-catalyzed methanol conversion into hydrocarbons were identified by combining kinetics, spectroscopy, and DFT calculations. The first intermediates containing a C-C bond are acetic acid and methyl acetate, which are formed through carbonylation of methanol or dimethyl ether even in presence of water. A series of acid-catalyzed reactions including acetylation, decarboxylation, aldol condensation, and cracking convert those intermediates into a mixture of surface bounded hydrocarbons, the hydrocarbon pool, as well as into the first olefin leaving the catalyst. This carbonylation based mechanism has an energy barrier of 80 kJ mol(-1) for the formation of the first C-C bond, in line with a broad range of experiments, and significantly lower than the barriers associated with earlier proposed mechanisms.

Different types of DNA have been used to investigate binding interactions of Cu(TMpyP4), where TMpyP4 denotes the deprotonated form of mesotetrakis(4-(/V-methylpyridiniumyl))porphyrin. Physical methods employed include electronic absorption and circular dichroism as well as luminescence spectroscopy. Most of the studies have been carried out at µ = 0.2 M in a pH 7.8 Tris buffer at 25 °C. With DNA samples containing both guanine-cytosine and adenine-thymine base pairs, our results confirm that Cu(TMpyP4) can bind at external sites-most likely within one of the grooves of DNA-or by intercalation (

Coupled cluster theory with single, double and perturbative triple excitations (CCSD(T)) is widely considered to be the 'gold standard' of ab initio quantum chemistry. Using the domain-based pair natural orbital local correlation concept (DLPNO-CCSD(T)), these calculations can be performed on systems with hundreds of atoms at an accuracy of about 99.9% of the canonical CCSD(T) method. This allows for ab initio calculations providing reference adsorption energetics at solid surfaces with an accuracy approaching 1 kcal/mol. This is an invaluable asset, not least for the assessment of density-functional theory (DFT) as the prevalent approach for large-scale production calculations in energy or catalysis applications. Here we use DLPNO-CCSD(T) with embedded cluster models to compute entire adsorbate potential energy surfaces for the binding of a set of prototypical closed-shell molecules (H2O, NH3, CH4, CH3OH, CO2) to the rutile TiO2(110) surface. The DLPNO-CCSD(T) calculations show excellent agreement with available experimental data, even for the 'infamous' challenge of correctly predicting the CO2 adsorption geometry. The numerical efficiency of the approach is within one order of magnitude of hybrid-level DFT calculations, hence blurring the borders between reference and production technique.

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In dieser Zuschrift wurde fälschlicherweise eine in der Literatur angegebene Reakti-onsgeschwindigkeit als Geschwindigkeitskonstante bei der Geschwindigkeitsberech-nung in den Hintergrundinformationen (S9) verwendet:"As emi-quantitative estimation of the carbonylation rate is made based on reported kinetic data from literature. A rate constant of 6.8 mol (g atom Al) À1 h À1 was applied for the reaction on HZSM-5 at 450 8 8C, according to literature (Fig. 1Angew.C hem. Int. Ed. 2006, 45, 1617-1620). Applying areaction order of 1f or CO and 0f or dimethyl ether,and an H-ZSM-5(Si/Al 90) loading of 1g,acetyl species (HOAc and MeOAc) formation rate of 560 mmol/min under 1mbar CO or 5.6 mmol/min under 0.01 mbar CO was obtained." Eine neue Schätzung der Carbonylierungsgeschwindigkeit durch die Autoren auf der Grundlage ihrer experimentellen Daten ergab, dass diese Aussage korrigiert werden muss zu "A semi-quantitative estimation of the carbonylation rate is made based on our experimental results over H-ZSM-5(Si/Al 90). Acarbon-based reaction rate constant of 140 mmol (g cat) À1 h À1 (bar CO) À1 at 450 8 8Cwas obtained from our DME carbonylation experiment. Applying areaction order of 1f or CO and 0f or dimethyl ether,and an H-ZSM-5 loading of 1g,acetyl species (HOAc and MeOAc) formation rate is calculated to be 140 mmol h À1 (2.3 mmol min À1)under 1mbar CO." Bei 450 8 8Czeigt dieser Katalysator eine Anfangsperionde von ca. 1.5h(g cat) À1 (mol MeOH) À1 vor der Olefindetektion, und er liefert ca. 0.4 %Ausbeute an Methan, was zu einem geschätzten CO-Druck von ca. 0.7 mbar führt. Daraus resultiert eine Ausbeute von 150 ppm Acetylspezies während dieser Anfangsperiode, was sich im DME-Carbonylierungsexperiment als ausreichend zur Initiierung der Olefinbildung selbst bei 300 8 8Cerwies. Die Korrektur der Rechnung ändert daher nichts an der Feststellung eines langsamen Carbonylierungsprozesses und der ausreichenden Anreicherung von Acetylprodukten zur Initiierung der Kohlenwasserstoffbildung. Die Autoren danken Prof. Aditya Bhan, University of Minnesota, fürhilfreiche Kommentare.