Evacuation Conditions Research Articles

Carbon-13 NMR identification of intermediates formed by 2-methyl-2-propanol adsorption in H-ZSM-5

{sup 13}C NMR spectroscopy has been used to characterize intermediates formed by the adsorption of 2-methyl-2-propanol, (CH{sub 3}){sub 3} {sup 13}COH, on a H-ZSM-5 zeolite. Previous adsorption studies had shown that, upon exposure of H-ZSM-5 to this alcohol and subsequent evacuation at 295 K, an adsorption complex could be formed, which had a coverage of 1 alcohol molecule/Al atom in the zeolite and had carbenium-ion-like properties. In the present NMR studies, it is shown that the adsorbed species can best be described as a silyl ether, with the alkyl group covalently bonded to the zeolite framework oxygen. Furthermore, the adsorption and evacuation conditions used for preparing the samples are found to be very important since these silyl ether intermediates are highly reactive. The {sup 13}C NMR spectrum obtained following adsorption shows two prominent features, one at 77 ppm from TMS, which is assigned to carbon that is bonded to the oxygen, and a second at 29 ppm, which is due to aliphatic carbons formed in secondary reactions. {sup 13}C NMR spectra were taken of samples at 10 K and after heating to 373 K to verify these assignments, as well as search for additional features that could be masked bymore » dynamics at room temperature. No spectral features were observed in the region expected for carbenium ions, even though the chemistry observed for the adsorption intermediate was consistent with this chemistry and similar to that observed following olefin adsorption on H-ZSM-5. This implies that the steady-state concentration of carbenium ions in H-ZSM-5 is low or that the lifetime of these species is short. 32 refs., 8 figs.« less

Simulation on Group Evacuation Linked with an Inundation Analysis

A simulation method on evacuation system linked with a simulation method of an overland flood flow due to river bank breach is presented. A selection of the shortest way to the evacuation site is solved by using the Warshall-Floyd method. Validity of this simulation method is examined at first under the several conditions of evacuation in a model study area. Subsequently, the evacuation of groups can be simulated well by using this simulation method of evacuation linked with an inundation analysis. Finally, this model is applied to the actual basin (Ogura basin, situated in the south of Kyoto Prefecture), and group evacuation is simulated under several conditions.

Temperature runaway of microwave heated materials: Study and Control

AbstractThe behaviour of a material in a microwave field is di-rectly related to the temperature dependence of the imaginary part of the permittivity of a material. According to the conditions of thermal evacuation chosen, for example convection, its heating is either stable or unstable. For some materials, a critical temperature can be defined which represents an upper limit beyond which the heating is unstable whatever the convective heat transfers. The optimal conditions which can be obtained through the use of an automatic regulation of the heating are, as a consequence, determined. The microwave heating of EPDM rubber is treated as an example.

Gas removal from fibrous materials when heated in vacuum

Studies were made to investigate the composition and rate of gas separation in vacuum by considering the time relationship for the partial pressure of gases separating from the specimens in conditions of isothermal soaking and continuous evacuation through a diaphragm with constant conductivity. Mass-spectroscopic analysis of the composition of the gases carried out with the IPDO-1 unit showed that during heating in vacuum, vapors of water, hydrogen, nitrogen, carbon monoxide, and small amounts of carbon dioxide separated from the materials.

Extraction of Endogenous Ethylene and Ethane from Leaves ofPhaseolus vulgarisL.

A procedure to recover small volumes of gases from plant tissues by vacuum extraction is described. Changes in the volume of the gases and the concentrations of ethylene and ethane recovered from Phaseolus leaves were observed when the evacuation conditions during extraction were altered. These changes were different in the primary leaves and in the second trifoliate leaves. Thus, estimates of internal ethylene and ethane concentrations appear to be influenced both by the morphology of the tissue and the evacuation conditions employed. There was a positive correlation between the concentrations of ethylene and ethane in the gaseous extracts. The internal ethylene concentrations in the primary, first trifoliate, and second trifoliate leaves, considered together, were correlated with their respective rates of ethylene emanation.