Oxygen moderate-temperature

Contact with air is greatest in open stirred vessels and least in closed sigma-blade mixers. The data in Fig. 16 show that, in the absence of oxygen, moderate temperatures and mechanical shear are not major causes of degradation. 

Orga.nic Chemistry. The organic chemistry of sulfur dioxide, particularly as it relates to food appHcations, has been discussed (246). Although no reaction takes place with saturated hydrocarbons at moderate temperatures, the simultaneous passage of sulfur dioxide and oxygen into an alkane in the presence of a free-radical initiator or ultraviolet light affords a sulfonic acid such as hexanesulfonic acid [13595-73-8]. This is the so-called sulfoxidation reaction (247) ... 

Direct reaction of oxygen with most organic materials to produce radicals (eq. 13) is very slow at moderate temperatures. Hydrogen-donating antioxidants (AH), particularly those with low oxidation—reduction potentials, can react with oxygen (eq. 14), especially at elevated temperatures (6). 

The process which was developed hy DOW involves cyclodimerization of hutadiene over a proprietary copper-loaded zeolite catalyst at moderate temperature and pressure (100°C and 250 psig). To increase the yield, the cyclodimerization step takes place in a liquid phase process over the catalyst. Selectivity for vinylcyclohexene (VCH) was over 99%. In the second step VCH is oxidized with oxygen over a proprietary oxide catalyst in presence of steam. Conversion over 90% and selectivity to styrene of 92% could he achieved. ... 

The BDE of the a-C—H bonds of ethers R1R2C HOC HR1R2 are weaker in comparison with the C—H bonds of the parent hydrocarbons [2], When a-C—H of ether is cleaved, the formed a-alkoxyalkyl radical is stabilized by the interaction of an unpaired electron with p-electrons of the oxygen atom. Therefore, the attack of the peroxyl radical on the ether molecule occurs more rapidly than on hydrocarbon. Most of the ethers are easily oxidized by dioxygen at moderate temperatures. Table 7.11 contains a list of BDEs of ethers, as well as BDEs of hydrocarbons, and values of enthalpies of peroxyl radical abstraction with ether. 

A number of oxides with the fluorite structure are used in solid-state electrochemical systems. They have formulas A02 xCaO or A02 xM203, where A is typically Zr, Hf, and Th, and M is usually La, Sm, Y, Yb, or Sc. Calcia-stabilized zirconia, ZrC)2.xCaO, typifies the group. The technological importance of these materials lies in the fact that they are fast ion conductors for oxygen ions at moderate temperatures and are stable to high temperatures. This property is enhanced by the fact that there is negligible cation diffusion or electronic conductivity in these materials, which makes them ideal for use in a diverse variety of batteries and sensors. 

Quite recently it was shown that phosphonic esters, trimethylsilyl [124, 143] and alkyl esters [124,143, 145] could also be used to modify the surface of titanium or aluminum oxide in organic solvents at moderate temperatures. Unlike Si-O-C bonds, P-O-C bonds are not easily hydrolyzed, and their cleavage on an oxide surface was unexpected. Most probably, coordination of the phosphoryl oxygen to the surface assists the condensation by increasing the electrophilicity of the P atom, thus facilitating the condensation of P-0-R groups with surface hydroxyls (Scheme 7) [124]. The chemisorption of... 

Here we see that the rate is strongly inhibited by adsorbed oxygen, which blocks sites for NO to adsorb into. This is the reason that NO cannot be decomposed in a unimolecular process at moderate temperatures in the presence of O2. 

Iron reacts with nonmetals forming their binary compounds. It combines readily with halogens. Reaction is vigorous with chlorine at moderate temperature. With oxygen, it readily forms iron oxides at moderate temperatures. In a finely divided state, the metal is pyrophoric. Iron combines partially with nitrogen only at elevated temperatures. It reacts with carbon, sulfur, phosphorus, arsenic, and silicon at elevated temperatures in the absence of air, forming their binary compounds. 

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