Reaction ammonia oxidation

The reaction is exothermic reaction rates decrease with increased carbon number of the oxide (ethylene oxide > propylene oxide > butylene oxide). The ammonia—oxide ratio determines the product spht among the mono-, di-, and trialkanolamines. A high ammonia to oxide ratio favors monoproduction a low ammonia to oxide ratio favors trialkanolamine production. Mono- and dialkanolamines can also be recycled to the reactor to increase di-or trialkanolamine production. Mono- and dialkanolamines can also be converted to trialkanolamines by reaction of the mono- and di- with oxide in batch reactors. In all cases, the reaction is mn with excess ammonia to prevent unreacted oxide from leaving the reactor. 

Toray. The photonitrosation of cyclohexane or PNC process results in the direct conversion of cyclohexane to cyclohexanone oxime hydrochloride by reaction with nitrosyl chloride in the presence of uv light (15) (see Photochemical technology). Beckmann rearrangement of the cyclohexanone oxime hydrochloride in oleum results in the evolution of HCl, which is recycled to form NOCl by reaction with nitrosylsulfuric acid. The latter is produced by conventional absorption of NO from ammonia oxidation in oleum. Neutralization of the rearrangement mass with ammonia yields 1.7 kg ammonium sulfate per kilogram of caprolactam. Purification is by vacuum distillation. The novel chemistry is as follows ... 

Rates and selectivities of soHd catalyzed reactions can also be influenced by mass transport resistance in the external fluid phase. Most reactions are not influenced by external-phase transport, but the rates of some very fast reactions, eg, ammonia oxidation, are deterrnined solely by the resistance to this transport. As the resistance to mass transport within the catalyst pores is larger than that in the external fluid phase, the effectiveness factor of a porous catalyst is expected to be less than unity whenever the external-phase mass transport resistance is significant, A practical catalyst that is used under such circumstances is the ammonia oxidation catalyst. It is a nonporous metal and consists of layers of wire woven into a mesh. 

At low temperatures the SCR reactions dominate and nitrogen oxide conversion increases with increasing temperature. But as temperature increases, the ammonia oxidation reactions become relatively more important. As the temperature increases further, the destmction of ammonia and generation of nitrogen oxides by the oxidation reactions causes overall nitrogen oxide conversion to reach a plateau then decreases with increasing temperatures. Examples are shown in Figure 7 (44). 

The most popular SCR catalyst formulations are those that were developed in Japan in the late 1970s comprised of base metal oxides such as vanadium pentoxide [1314-62-1J, V20, supported on titanium dioxide [13463-67-7] Ti02 (1). As for low temperature catalysts, NO conversion rises with increasing temperatures to a plateau and then falls as ammonia oxidation begins to dominate the SCR reaction. However, peak conversion occurs in the temperature range between 300 and 450°C, and the fah-off in NO conversion is more gradual than for low temperature catalysis (44). 

F.G. Liljenroth, ChemMetEng 19, 287—393 (1918) (Starting and stability phenomenon of ammonia oxidation and similar reactions)... 

Interestingly, this situation is very different when we consider activation of NH3 or H2O by coadsorbed O. This would typically occur in the Ostwald reaction that oxidizes ammonia to NO or the methane reforming reaction in which CH4 reacts with O2 or H2O to give CO, CO2, and H2. 

Closed symbols in Fig. 1 show the effect of reaction temperature on ammonia oxidation over CuO by heating with a conventional electric furnace. The reaction started at about 400 K and the conversion of NH3 became 1 at temperatures higher than 500 K. Fig. 1 also indicates that selectivity to N2 was high at low temperatures but it decreased as the temperature increased. Both N2O and NO increased instead of N2, except at 623 K, at which N2O decreases. NO was detected above 583 K, and it monotonously increased by the temperature. High reaction temperature seems to tend deeper oxidation to NOx. Considering that oxidation of N2 to N2O and NO is difficult in the tested temperature range. 

By far the most important use of the platinum metals is for catalysis. The largest single use is in automobile catalytic converters. Platinum is the principal catalyst, but catalytic converters also contain rhodium and palladium. These elements also catalyze a wide variety of reactions in the chemical and petroleum industry. For example, platinum metal is the catalyst for ammonia oxidation in the production of nitric acid, as described in Pt gauze, 1200 K... 

Rebrov, E. V., Duinkerke, S.A., de Croon, M. H. J. M., Schouten, J. C., Optimization of heat transfer characteristics, flow distribution, and reaction processing for a microstructured reactor/ heat-exchanger for optimal peformance in platinum catalyzed ammonia oxidation, Chem. Eng. 93 (2003) 201-216. 

Figure 3.28 Unexpected increase in NO/N2 selectivity for ammonia oxidation reaction in a micro membrane reactor [19],...

Investigations with the modular multi-channel [28,98] and silicon chip [19, 56-62] micro reactors demonstrate that by exact temperature control the oxidation of ammonia can be run with increased and deliberately steered selectivity. A major application is provided by carrying out former high-temperature reactions in the low-temperature regime. In the case of ammonia oxidation in the chip micro reactor, the yield of the value product NO was actually lower in that regime. In the case of the multi-plate-stack micro reactor, higher yields of the value product NO2 were achieved. 

Ammonia oxidation was a prototype system, but subsequently a number of other oxidation reactions were investigated by surface spectroscopies and high-resolution electron energy loss spectroscopy XPS and HREELS. In the case of ammonia oxidation at a Cu(110) surface, the reaction was studied under experimental conditions which simulated a catalytic reaction, albeit at low... 

Figure 2.6 Variation of the concentration of surface species calculated from the differential equations describing the model for ammonia oxidation.45 Efficient low-energy pathways to products are available through the participation of surface transients present at immeasurably low concentrations under reaction conditions. The NH3 surface concentration is 10 6 ML. (Reproduced from Ref. 45).

The density function calculations for the ammonia oxidation reaction do, however, depend on models where the reactants are in stable adsorption states... 

In view of the spectroscopic evidence available, particularly from coadsorption studies (see Chapter 2), ammonia oxidation at Cu(110) became the most thoroughly studied catalytic oxidation reaction by STM. However, a feature of the early STM studies was the absence of in situ chemical information. This was a serious limitation in the development of STM for the study of the chemistry of surface reactions. What, then, have we learnt regarding oxygen transient states providing low-energy pathways in oxidation catalysis ... 

The production of N20 is shown in Figure 9.7. It should be noticed that on V205/W03-Ti02 N20 is not only formed by ammonia oxidation (refer Chapter 1) but also due to the following reaction [32,33] in analogy to the SCR reaction ... 

Ammonia oxidation catalysts (sometimes called slip catalyst) are conventional oxidation catalysts based on precious metals. The most active types are based on Pt. Then-activity is strongly dependent on the temperature and, thus, relatively large catalyst volumes are required for the ammonia oxidation below 250°C. At rising temperatures, their oxidation power increases and this leads to the formation of N20 and NO. Especially undesired is their strong tendency to form N20 at intermediate temperatures (250-300°C) [2] if the gas coming from the SCR catalyst also contains unreacted NO, which allows for the reaction ... 

The main reactions, which have to be considered on SCR catalysts, are the standard-SCR, fast-SCR, and the N02-SCR reactions, beside the ammonia oxidation and the formation of N20. The fast-SCR reaction is promoted by N02 in the feed that can be generated from NO in a pre-oxidation catalyst. However, the right dimensioning of the oxidation catalyst is critical in order to prevent the production of an excess of hazardous N02. This problem is further aggravated if a continuous regenerating DPF is installed in front of the SCR system, as part of the N02 produced by the oxidation catalyst is always consumed in the filter for soot oxidation. 

The oxidation of NO to NO2, which is an important step in the manufacture of nitric acid by the ammonia-oxidation process, is an unusual reaction in having an observed third-order rate constant (k o in ( rm) = kso Oc02) which decreases with increase in temperature. Show how the order and sign of temperature dependence could be accounted for by a simple mechanism which involves the formation of (NO)2 in a rapidly established equihbrium, followed by a relatively slow bimolecular reaction of (NO)2 with O2 to form NO2. 

The gas leaving an ammonia oxidation unit in a continuous process is cooled rapidly to 20°C and contains 9 mol % NO, 1% N02, 8% O2, and 82% N2 (all the water formed by reaction is assumed to be condensed). It is desirable to allow oxidation of NO to N02 in a continuous reactor to achieve a molar ratio of N02 to NO of 5 before absorption of the N02 to make HNO3. Determine the outlet temperature of the reactor, if it operates adiabatically (at essentially 6.9... 

Ammonia oxidation process, of nitric acid production, 17 170-171 Ammonia oxidation reactions, 10 98 Ammonia plant functions of, 17 293 as reliability example, 26 994-997... 

Most effort over the electrochemical reduction of benzene hydrocarbons has centred on finding a reaction medium, which is also a better solvent for the substrate than liquid ammonia. Aliphatic amines have proved useful solvents and they may be used in an undivided electrochemical cell. Base is generated at the cathode while an equivalent of acid is generated in the anode reaction so that mixing of the cel contents maintains a neutral solution. An alcohol is usually added as a proton donor to prevent the build-up of a localised highly basic environment. The simultaneous anode reaction is oxidation of the amine. Electrodes of platinum, aluminium or graphite have been used. Under these conditions, benzene [38] is converted... 

To describe the NH3 + NO/NO2 reaction system over a wide range of temperatures and NO2 NOxfeed ratios in addition to ammonia adsorption-desorption, ammonia oxidation and standard SCR reaction with the associated kinetics already discussed in Section 2.3.2, the following reactions and kinetics have been considered by Chatterjee and co-workers [79] ... 

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