Gallium oxides temperatures

Kisailus, D., Choi, J.H., Weaver, J.C., Yang, W. and Morse, D.E. (2005) Enzymatic synthesis and nanostructural control of gallium oxide at low temperature. Advanced-Materials, 17, 314—318. 

Gallium sesquioxide is precipitated in hydrated form upon neutralization of acidic or basic solution of gallium salt. Also, it is prepared by thermal decomposition of gallium salts. Gallium oxide hydroxide, GaOOH [20665-52-5] on calcinations at high temperatures yields beta- Ga203. 

The finding of the low-temperature activation of propane on zeolite Ga/HZSM-5 indicates a bifunctional reaction mechanism 179,181. The highly dispersed gallium oxide species in close vicinity to the Bronsted acid sites promote the initial activation of propane. Derouane et al. 179,181 further showed that hydrogen inhibits the activation of propane. This effect was explained by a competitive adsorption of hydrogen on the gallium species or even by a reduction of Ga to Ga species. 

Gallium oxides form a similar system, affording a high-temperature a- and a low-temperature y-Ga203 phase. The trioxide is formed by heating the nitrate, the sulfate, or the hydrous oxides that are precipitated from Gam solutions by the action of ammonia. Beta-Ga203 contains both tetrahedrally and octahedrally coordinated... 

The gallium oxide system is somewhat similar to that of aluminum, affording a high-temperature (a) and a low-temperature y-Ga203, each having the same structure as their aluminum counterparts. /9-Ga203 is the most stable crystalline modification (mp 1740 °C) it has a unique crystal stracture with the oxide ions in distorted ccp and Ga in distorted tetrahedral and octahedral sites, with Ga-O distances of 1.83 and 2.00 A, respectively (Figure 11). ... 

A departure from the similarity of gallium oxides with those of aluminum is the stability of the gallium(I) oxide, which is made by high-temperature reactions (e.g. equations 3-5). 

Gallium oxide catalyzes the exchange of vinylic and allylic hydrogens by deuterium with high selectivity. It also interconverts cis- and tr[Pg.241]

The gallium content of NH4-[Si,Ga]MAG (0.73 mmol/g) corresponds well to the amount of ammonia desorbed from this sample in the high-temperature step of the TPD process (0.67 mmol/g). Thus, the amount of intercrystalline gallium oxide should not exceed 10 % of the total gallium content. In contrast to NH4-[Si,Al]MAG, the gallium variety seems to be relatively resistant to extraction of the incorporated trivalent framework element by acid leaching (compare curves 1 and 2 in Figure 4 or the respective data in Table 1). 

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). 

From Figure 6.16, it is clearly seen that the extraframework gallium oxide generated by demetallation at elevated temperatures in water vapor enhances the activity, and the yield of alkenes is increased, whereas the formation of extraframework titanium dioxide leads to the yield of a large amount of methane in the cracking product. 

In a previous paper [10] we assumed that the zeolite acidity is the driving force, that allows a substantial lowering of the reduction temperature of the admixed gallium oxide phase. Recently we proved the... 

The thermal decomposition of gallium nitrate hydrate (Ga(N03)3-xH20) to gallium oxide has been studied by TG/DTG and DSC measurements performed at different heating rates. Berbenni and coworkers [65] concluded that 8 water molecules are present in the hydrate compound. Anhydrous gallium nitrate does not form at any temperature because the reaction consists of coupled dehydration/decomposition processes that occur with a mechanism dependent on heating rate. TG measurements performed with isothermal steps (between 31... 

Catalysts based on other metals, such as gallium and vanadium oxides, can be also employed in DH processes [8, 9]. For example, silica-supported gallium oxide catalyst has been found to be moderately active, but quite selective in propane dehydrogenation (up to 80%) and results in much less coking, 1/10 of that using a silica-supported chromium oxide [8], There is an extensive research aimed to find new DH catalysts that will perform well at moderate temperatures, suffer less from coke deposition and maintain catalytic activity for long periods of time without regeneration. 

Conduction electrons in gallium oxide 3-Ga203 exhibit bistability detectable by EPR at X band (V = 8.4 GHz BO, 340 mT) and temperatures higher than 100 K, but the effect is also observable at room temperature. 

Figure 3.3 Phase transformations and synthesis temperatures in the gallium oxide system. Adapted from Roy et at. [72],...

During the past thirty years several reports have been published on the synthesis of gallium oxonitride phases. The first of these was mentioned by Verdier and Marchand in 1976 as a side product during the reaction of ammonia with gallium oxide, whenaphase with the composition Gai x 3nxpNi xO withx 0.1 and as vacancies was isolated under low-temperature conditions [213]. The authors did not report any detailed crystal structure data, but did note that the XRD pattern was... 

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