Germanium oxide reactions

For the polymerization, either in the melt or solid phase, the reaction is driven to the polymer by removing ethylene glycol. The polymerization reaction is typically catalyzed by solutions consisting of antimony trioxide or germanium oxide. Both polycondensation catalysts also catalyze the reverse reaction, which is driven by an excess of ethylene glycol at melt conditions, generally above 255 °C. The polymerization reaction follows second-order kinetics with an activation energy of 22 000 cal/mol [6],... 

Which of the following intermediate oxidation states is stable with respect to the possible oxidation reactions of the elements in oxygen-free noncomplexing media germanium(II), tin(II) ... 

The heat effect is one of the main characteristics of every chemical process. The heat effects of the reactions occurring at the solid surface and involving gas-phase molecules can be directly measured. To do this, one must know the amount of heat release during the reaction (microcalorimetry) and the number of absorbed gaseous molecules (volumo-metry). The heat effects of some reactions proceeding at the surfaces of activated silicon and germanium oxides and accompanied by the modification of the chemical structure of active sites are given in Table 7.4. 

The measurements of F depth profiles in chipped flints have been realised using the 4.7 keV wide 872 keV 19F(p,a12.3y)160 resonance. This reaction provides a good depth resolution (about 100 nm in Si02). The 4-7.5 MeV y-rays are detected with a BGO (bismuth germanium oxide) detector at 0°C with respect to the incident beam. The flint artefacts can be settled in the vacuum chamber as whole pieces without any sample preparation [35],... 

This unusual reaction has been proposed to occur via a four-center mechanism131. While no structural information was derived from the original experiments, calculations at the HF level predict that a linear structure corresponding to protonated germanium oxide, GeOH+, is considerably more stable than the alternative linear HGeO+ structure151. 

The polycondensation of BHET to PET proceeds in the melt at temperatures of 270-305 °C, under vacuum (< 1 mbar absolute pressure) and in the presence of Lewis acid metal compounds, such as titanium alkoxides, dialkyltin oxide, gallium oxide, germanium oxide, thallium oxide, lanthanide salts, and most commonly, antimony oxide [1,2, 22-26]. Under polymerization reaction conditions, these catalysts are generally converted to their alkoxides with ethylene glycol. Typical of such alkoxides is antimony(III) glycolate, the active catalyst for the majority of the world s PET production [27] (cf. Structure 1). 

Germanium Dioxide. The chemical reaction of oxygen with germanium is similar to the thermal oxidation of silicon which results in the growth of a thin layer of silicon dioxide. As noted above, germanium oxidation is complicated by the formation of an intermediate reaction product, germanium monoxide, which, unlike silicon monoxide, is thermodynamically unstable as a solid and sublimes near its formation temperature (46,47). Therefore, instead... 

Side reactions are the formation of dehydration of the pendent 2-hy-droxyethyl ester to result in pendent vinyl ester groups. These can further react under the ejection of acetaldehyde. Suitable catalysts are germanium compounds, such as germanium oxide, zinc acetate, manganese acetate, or a combination of antimony trioxide and trimethyl phosphate. ... 

Copolymers with high enough molecular weight for practical use were prepared from succinic acid and 1,4-butanediol and minor amounts of lactic acid [30]. An increase in reaction rate was claimed when the aliphatic diol and the aliphatic dicarboxylic acid were polycondensated using a few mole percent lactic acid and a germanium oxide catalyst. 

Zn, Sn... The catalyst amount represents 0.05-0.5 % of the total mass of the reaction medium. Antimony oxide historically emerged as the catalyst of choice. Germanium oxide is also used but although it is a more active catalyst than antimony, the high cost of the germanium excludes its common used in commercial production of PET. During the reaction, methanol is formed and is collected by distillation in order to displace the equilibrium of the reaction. 

D/ef/iy/germanium oxide may also be made by hydrolyzing (C2H5)2GeCl2 prepared from Ge by the direct reaction of C2H5CI102. The hydrolysis product is an oily mixture of polymers, less soluble in water than (CH3)2GeO but decidedly soluble. 

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