Alkali metal ions production

Hydrolysis, although a simple method in theory, yields terephthalic acid (TPA), which must be purified by several recrystallizations. The TPA must be specially pretreated to blend with ethylene glycol to form premixes and slurries of the right viscosities to be handled and conveyed in modern direct polyesterification plants. Hie product of the alkaline hydrolysis of PET includes TPA salts, which must be neutralized with a mineral acid in order to collect the TPA. That results in the formation of large amounts of inorganic salts for which commercial markets must be found in order to make the process economically feasible. There is also the possibility that the TPA will be contaminated with alkali metal ions. Hydrolysis of PET is also slow compared to methanolysis and glycolysis.1... 

Polymer (184) has a network structure and was obtained by reaction of dibenzo-18-crown-6 with formaldehyde in formic acid. Amongst the alkali metal ions, it selectively captures K+ and Cs+ from methanol or methanol/water. A related polymeric product has been reported (as a gel) from the reaction of this crown with formaldehyde in chloroform using sulfuric acid as catalyst (Davydova, Baravanov, Apymova Prata, 1975). 

Fig. 6. Limiting single ion mobility-viscosity product vs. reciprocal of estimated crystallographic radii of alkali metal ions...

Fig. 10. Limiting single ion mobility-viscosity product for alkali metal ions vr. solvent Lewis basicity (as measured by enthalpy of reaction with SbCl5)...

Cyclooctatetraene was reduced electrochemically to cyclooctatetraenyl dianion. In DMF the product is mostly (92%) 1,3,5-cyclooctatriene at —1.2 V. If the potential is lowered the main product is 1,3,6-cyclooctatriene. Previous experiments, in which the anion radical was found to be disproportionated, were explained on the basis of reactions of the cyclooctatetraene dianion with alkali metal ions to form tightly bound complexes, or with water to form cyclooctatrienes. The first electron transfer to cyclooctatetraene is slow and proceeds via a transition state which resembles planar cyclooctatetraene102. 

The reaction product SiF4 would be gaseous, but it reacts with two HF to Si I7 and two protons and stays in solution [Mellj. The solubility of Si 17, which is in the order of mol 1 1 is significantly reduced in the presence of alkali metal ions. Especially for Rb, K or Cs, a micrometer thick, insoluble layer of metal hexafluoro-silicate may be formed on the electrode surface [Hal2j. The divalent electrochemical dissolution reaction is dominant during PS formation. The effects of the reaction products SiFg and H2 on pore growth are discussed in Section 9.5. 

Minachev et al. (41, 42) have recently examined alkali metal ion forms of various zeolites (A, X, Y, L, chabazite, erionite, and mordenite) for cyclohexane oxidative dehydrogenation. Not surprisingly these alkali metal ion forms are considerably less active than those containing transition metal ions (reaction temperatures of approximately 300° and 450°C, respectively). Further, cyclohexene rather than benzene is the predominant product (selectivity to cyclohexane 67-84%), particularly with small-pore zeolites. In fact, NaA was the most active zeolite tested (42), which strongly suggests that the reaction is simply occurring on the outer surface of the zeolite crystallites. 

There is wide agreement that substitution of alkali metal ions retards the early reaction of the aluminate phase, which is thus less for the orthorhombic than for the cubic polymorphs (S35,B43,RI3). The effect has been attributed to structural differences, but the early reaction of pure C, A is also retarded by adding NaOH to the solution, and the OH ion concentration in the solution may be the determining factor (S35). The reaction of C,A is also retarded by iron substitution and by close admixture with ferrite phase formation of a surface layer of reaction products may be a determining factor, at least in later stages of reaction, and the retarding effect of such a layer may be greater if it contains Fe (B44). 

As indicated in the original patent, the absence of alkali metal ions in the synthesis mixture is critical for the incorporation of Ti in the lattice. Their presence as impurities in commercial samples of tetrapropylammonium hydroxide was not recognized in several studies, particularly in early ones, with the result that TS-1 was impure, containing Ti02 particles and amorphous Ti-silicates. Sometimes, however, the presence of alkali and other impurities is the consequence of a deliberate decision, in an attempt to decrease the cost of production of the catalyst by the use of cheaper sources of Si, Ti and tetrapropylammonium hydroxide [12]. 

Alkali metal ion exchanged variants of both zeolites X and Y react with Na vapour to form cluster cations such as Na4 and Na6, with the production of intensely coloured products (reminiscent of the colour (F-) centres in alkali halides). 

A small fraction of the reactant ions collide with Cm molecules, and product ions scattered into the forward hemisphere in the laboratory frame are collected by the octapole. Product and unscattered reactant ions are mass selected by a double focusing electric and magnetic sector mass spectrometer, and detected by an on-axis Daly detector [16]. In the following we give only relative cross sections, due to uncertainties in the absolute pressure of Cm, the product collection efficiency, and the alkali-metal ion beam intensities in the scattering cell. 

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