Expansion, hydrogen-induced

Thermal expansion can lead to membrane failure in the case of supported metal membranes if there is a large difference between the CTE of the support layer and the CTE of the permselective metal layer. If the support layer expands more than the permselective metal layer, then the permselective metal layer will be tom or fractured during heat up. On the other hand, if the support layer expands less than the permselective metal layer, then fatigue fracture may occur by the mechanism described above for hydrogen-induced expansion of the permselective metal layer. Mismatch of CTE is often a cause for poor durability in supported membranes comprised of a palladium alloy deposited onto a porous stainless steel support or a porous alumina support. 

When considering the influence of thermal expansion or hydrogen-induced expansion on membrane durability, it should be remembered that the absolute magnitude of expansion is dependent on the size (dimensions) of the membrane. Generally, smaller membranes will be more durable than larger membranes. 

Early attempts to induce the thermal ring expansion of arenes with (arylsulfonyl)nitrenes were disappointing in that primary sulfonamides, formed by hydrogen abstraction by the singlet nitrene, and A-phenylsulfonamides, were the major products.157 l-(Arylsulfonyl)-l//-azepines were produced in low yields and were isolated only as their [4 + 2] eycloadducts with ethene-... 

In the previous sections, expanded porphyrins have been described in which the expansion is restricted to the pyrrole-linking bridges. The smallest expanded porphyrin in which the expansion is created by an additional pyrrole subunit in the macrocycle is the so-called orangarin, a [20]pentaphyrin(1.0.1.0.0).13 Orangarin 39 can be prepared via a hydrogen chloride induced... 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

In the case of a FCB with small particles, the emulsion phase expands [5, 6, 7] when the bed is fluidized. This would make the bed sensitive to the decrease in the gas volume in the emulsion phase. If this assumption is true, we can postulate that the fluidization quality is hardly affected by the gas-volume reduction when the particles, which induce a small emulsion phase expansion, are used. The emulsion phase expansion decreases with increasing particle size and density [6]. In the present study, therefore, the particles used were larger and heavier than that generally used in the FCB. We carried out the hydrogenation of CO2 in a... 

The 4-oximes are convenient intermediates. Reduction with zinc/ acetic acid,54 hydrogen over palladium on charcoal55,56 or nickel,57 or lithium aluminum hydride,55 produces the 4-aminothiochroman. Interestingly, lithium aluminum hydride induces ring expansion to the... 

The final geometry was obtained when the calculated forces acting on the atoms and stress on the supercell became smaller than the threshold values. To evaluate the relative expansion of the lattice induced by the interstitial hydrogen, geometry optimizations of the pure metals were also employed. 

Figure 3. Relative expansion of the lattice constants of V induced by interstitial hydrogen. Open bars = O-site occupation closed bars = T-site occupation.

Laser irradiation induces hydrogen dissociation, which results in the expansion of the network. Hydrogen is then partially released, leaving deep... 

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