Nitric oxide generation, catalysts

The reaction is exothermic (see Exercise 12.1), but, since it is very slow, a catalyst is necessary. Nitric oxide, once again, can serve as an oxygen carrier, as in the lead chamber process (Section 10.2) and in reaction 10.8, where (CH3)2S generated in the kraft process is converted to DMSO. Even so, at the elevated temperatures required, reaction 12.1 needs to be forced to completion by absorption of the steam in concentrated sulfuric acid or some other desiccant. In variants of the Deacon process, copper chloride acts as the catalyst or as an intermediate for chlorine regeneration. 

Cobalt oxide (C03O4) catalysts are being used in some nitric acid plants as an alternative to platinum-rhodium (Pt-Rh). They generate less N2O, cost less and have a longer campaign life than Pt-Rh gauzes. (A paper in 2000 reported a conversion rate of ammonia to nitrous oxide as low as 0.5% over cobalt oxide catalyst)222. 

As mentioned in Table 4.2, the industrial Ube reaction is probably carried out on a heterogeneous catalyst. The probable mechanism is based on generation of an alkyl nitrite and oxidative addition of the alkyl nitrite onto a Pd° center. Nitric oxide is used as a co-catalyst in the Ube process. The Hoechst... 

Zirconia cells with Pt catalyst-electrodes can also be used to convert ammonia to nitric oxide with simultaneous electrical energy generation (6-7). Other industrially important oxidation reactions have been recently proposed for solid-state electro-... 

Examples of catalysts in combustion reaction include the effect of H2O on the carbon monoxide oxidation reaction CO H- 2 C02- Nitric oxide also catalyzes CO oxidation through the mechanism 2 NO 4-O2 2NO2 (overall) and NO2 -f CO NO H- CO2. In both of these examples, an intermediate compound (for example, NO2) is formed and then destroyed. The addition of a small amount of NO2 to an H2 — O2 mixture leads to a branched-chain explosion by introducing the relatively rapid initiation step NO2 H- X NO H- O H- X, with the O atoms so produced generating the usual H2 — O2 chain. The NO2 also participates in the efficient termination step NO2 H- O NO H- O2, which is sufficiently important at large concentrations of NO2 to cause a slow reaction to be... 

Benzyl ethers may be converted into their corresponding benzaldehyde derivatives by oxidation with nitric oxide (NO) in the presence of catalytic (V-hydroxyphthaUmide (NHPl). NO reacts with the catalyst to give phthalimide N-oxyl (PINO), which abstracts the benzylic hydrogen atom from the substrate to generate a radical, which reacts in turn with NO to give a carbocation. Nucleophilic attack of water to the cationic species gives the aldehyde via a hemiacetal intermediate. ... 

Mediated electrochemical oxidation (MEO) is an ex situ treatment technology that uses electricity, acid, and a metal catalyst to destroy organic wastes at low temperatures and pressures. The proprietary CerOx Corporation MEO configuration uses cerium metal as a catalyst to oxidize organic waste into carbon dioxide and water. The process occurs in an acidic solution, typically nitric acid. The first step involves the generation of an oxidant at the anode, followed by the reduction of water or another chemical species at the cathode. This technology serves as a nonthermal alternative to incineration. 

A treatment with different mineral acids is usually apt to remove catalyst particles as these normally consist of base metals. Hydrochloric or nitric acid are most frequently used for this purpose (Figure 3.36). The first, however, can only attack on directly accessible metal particles, whereas concentrated nitric acid leads to quite an efficient removal of metal because the oxidizing power of the acid enables it to attack on and even to open the closed tips of nanotubes. This ensures direct contact with the metal particles. Yet at the same time, the acid reacts with other defects in the nanotubes walls, which generates functional groups containing oxygen, like COOH, C=0, etc., on their surface. Upon prolonged acidic action and... 

---