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The potential of hierarchical H‐ZSM‐5 zeolites was studied for the conversion of DME to fuel‐compatible hydrocarbons. For this purpose, hierarchical H‐ZSM‐5 zeolites have been prepared from commercial H‐ZSM‐5 by desilication and organosilane‐directed hydrothermal synthesis. The zeolites were characterized by X‐ray diffraction, NH3‐TPD, DRIFTS, and N2 physisorption measurements. The catalysts have been tested in a tube reactor (1 bar, 648 K). The results indicate important structural changes in framework and acidic sites, which are significant for the synthesis of gasoline‐range hydrocarbons.

Low-temperature combustion (LTC) receives increasing attention because of its potential to reduce NO x and soot emissions. For the application of this strategy in practical systems such as internal combustion engines and gas turbines, the fundamental chemical reactions involved must be understood in detail. To this end, reliable experimental data are needed including quantitative speciation to assist further development of reaction mechanisms and their reduction for practical applications. The present study focuses on the investigation of low-temperature oxidation of ethanol and dimethyl ether (DME) under identical conditions in an atmospheric-pressure laminar flow reactor. The gas composition was analyzed by time-of-flight (TOF) mass spectrometry. This technique allows detection of all species simultaneously within the investigated temperature regime. Three different equivalence ratios of ϕ = 0.8, 1.0, and 1.2 were studied in a wide, highly-resolved temperature range from 400 to 1200 K, and quantitative species mole fraction profiles have been determined. The experiments were accompanied by numerical simulations. Their results clearly show the expected different low-temperature oxidation behavior of both fuels, with a distinct negative temperature coefficient (NTC) region only observable for DME. With detailed species information including intermediates, differences of the kinetics for both fuels are discussed. Small modifications of the mechanisms served to identify sensitivities in the model. The experimental results may assist in the improvement of kinetic schemes and their reduction.

Bei Versuchen zur Darstellung der syn- und anti-[3.3]Metacyclophan-Chinhydrone 1 und 2 wurde durch Demethylierung von 3 bzw. 4 und anschliesende Oxidation dasselbe [3.3](2,6)-p-Benzochinonophan (5) erhalten, das durch katalytische Hydrierung syn-[3.3]Metacyclophan-Chinhydron 1 ergab. Partielle Demethylierung und anschliesende Oxidation fuhrten jedoch ausgehend von 3 zum Dimethylether 7 des syn-Chinhydrons 1 und entsprechend aus 4 zum Dimethylether 8 des anti-[3.3]Metacyclophan-Chinhydrons 2. Die Strukturzuordnung der Stereoisomeren wurde durch Rontgen-Strukturanalyse von 7 bestatigt. Neben 7 und 8 wurden die entsprechenden Monomethylether 10 und 12 erhalten. – Die anti-Verbindungen 8 und 12 lagern sich thermisch quantitativ in die syn-Isomeren 7 bzw. 11 um, woraus auf eine starkere Grundzustands-Stabilisierung durch Charge-Transfer-Wechselwirkung bei den Donor-Acceptor-Systemen der syn-Reihe geschlossen wird. – Die Chinhydrone 7, 8, 10, 11 und 12 zeigen breite, intensive Charge-Transfer-Absorptionen im Bereich von 300 – 550 nm, die bei den Stereoisomeren-Paaren 7/8 und 11/12 trotz der sehr unterschiedlichen Donor-Acceptor-Orientierung uberraschend ahnlich sind; die Absorptionsintensitat der CT-Bande ist jedoch bei den anti-Chinhydronen betrachtlich groser als bei den syn-Isomeren. Electron Donor-Acceptor Compounds, XX. Intramolecular Quinhydrones of the [3.3]Metacyclophane Series: Synthesis, Stability, and Charge Transfer Absorptions of Stereoisomeric [3.3]Metacyclophane Quinhydrones On the attempt to synthesize the syn- and anti-[3.3]metacyclophane quinhydrones 1 and 2 by demethylation of 3 and 4, resp., and subsequent oxidation the same [3.3](2,6)-p-benzoquinonophane (5) was obtained which on catalytic hydrogenation yielded syn-[3.3]metacyclophane quinhydrone 1. Partial demethylation, however, and following oxidation led from 3 to the dimethyl ether 7 of the syn-quinhydrone 1, and analogously from 4 to the dimethyl ether 8 of anti-[3.3]-metacyclophane quinhydrone 2. The structural assignment of the stereoisomers was confirmed by an X-ray structure analysis of 7. In addition to 7 and 8, the corresponding monomethyl ethers 10 and 12 were obtained. – The anti-[3.3]metacyclophanes 8 and 12 undergo a complete thermal rearrangement to the syn-isomers 7 and 11, resp., from which a stronger ground state stabilisation by charge transfer interaction is concluded for the donor-acceptor systems of the syn-series. – The quinhydrones 7, 8, 10, 11, and 12 show broad, intensive charge transfer absorptions in the range from 300 to 550 nm which for the pairs of stereoisomers 7/8 and 11/12, in spite of the very different donor-acceptor orientation, are surprisingly similar: the absorption intensity of the CT band, however, is considerably stronger for the anti-quinhydrones than for their syn-isomers.