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Bicyclic δ-lactones with a carbon group at the bicyclic junction C-7a, designed as pseudoiridolactones, were synthesized from α-alkyl-α-hydroxymethylcyclopentanones via an intramolecular Horner-Wadsworth-Emmons reaction. 相似文献
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Electron irradiation of hcp scandium at T ? 12 K allowed to determine the energy threshold for Frenkel-pair creation, Td = 13.8 ± 0.5 eV, and the defect resistivity, . The annealing spectrum exhibits four substages between 20 and 70 K, a broad substage centered at 105 K attributed to interstitial long-range migration, and a stage III between 240 and 300 K. 相似文献
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Elyssa G. Fawaz Darine A. Salam Severinne S. Rigolet T. Jean Daou 《Molecules (Basel, Switzerland)》2021,26(16)
Hierarchical crystals with short diffusion path, conventional microcrystals and nanocrystals of ZSM-5 zeolites were used for biodiesel production from waste frying oils and were assessed for their catalytic activity in regard to their pore structure and acidic properties. Produced zeolites were characterized using XRD, nitrogen adsorption–desorption, SEM, TEM, X-ray fluorescence, and FTIR. Pore size effect on molecular diffusion limitation was assessed by Thiele modulus calculations and turnover frequencies (TOF) were used to discuss the correlation between acidic character and catalytic performance of the zeolites. Owing to the enhanced accessibility and mass transfer of triglycerides and free fatty acids to the elemental active zeolitic structure, the catalytic performance of nanosponge and nanosheet hierarchical zeolites was the highest. A maximum yield of 48.29% was reached for the transesterification of waste frying oils (WFOs) using HZSM-5 nanosheets at 12:1 methanol to WFOs molar ratio, 180 °C, 10 wt % catalyst loading, and 4 h reaction time. Although HZSM-5 nanosponges achieved high conversions, these more hydrophilic zeolites did not function according to their entire acidic strength in comparison to HZSM-5 nanosheets. NSh-HZSM5 catalytic performance was still high after 4 consecutive cycles as a result of the zeolite regeneration. 相似文献
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An experimental study on the removal of NOx in a simulated vehicle exhaust gas has been carried out using point to plane and multipoint to plane DBD corona reactors. Hydrocarbon (C3H6) and NOx by-products were systematically investigated with a Gas Chromatography coupled to a Mass Spectrometry (GC/MS). NOx (NO and NO2) and CO output were also monitored with a gas analyzer in order to complete the mass balance. 18O tracer technique analyzes is applied to investigate the mechanism of propylene decomposition. From the plasma chemical reaction pathway proposed, it is apparent that the oxygen activation is one of the important steps for initiating the oxidation processes and the R-NOx formation. We present data for the reaction of the (N2/O2/C3H6/CO2NO/H2O system in the corona discharge reactors mentioned above. This system has been shown to generate a significant amount of aldehyde. CH3NO2 and CH3ONO2 are the main R-NOx compounds produced. Reactant composition and discharge energy densities (controlled by a numerical oscilloscope) were the operating parameters under study in wet and dry air mixture. Water vapors played an important role in NOx removal (especially in NO2 removal) via the reaction forming HNO3. Therefore, in wet-gas mixture supplied reactors the highest removal rates of NOx were as high as 30%, while in dry-gas only 15%. Different dielectric materials such as Al2O3/SiO2 and TiO2 on Al2O3/SiO2 support have been used. 相似文献