And ammonia oxidation

Erwin DP, IK Erickson, ME Delwiche, FS Colwell, JL Strap, RL Crawford (2005) Diversity of oxygenase genes from methane- and ammonia-oxidizing bacteria in the Eastern Snake River plain aquifer. Appl... 

The reactions of adsorption desorption of NH3 and ammonia oxidation to N2 were considered with the kinetic expressions shown in Section V.A.2.b. 

In summarizing the present stability data on AN, prepd from synthetic ammonia and ammonia oxidation nitric acid, it may be said that up to temp of its mp, AN is fairly stable. At slightly above it s mp (say ca 170°), slow decompn begins, but this is hardly perceptible until temps 200—210° are reached. From this point on the decompn, accompanied by evoln of gas, is fairly rapid and, if the substance is confined, explosion may take place above 260° (See Refs 91 92 and 124 for more info rmation on the thermal decompn of AN)... 

HaUatn, S. J., Mincer, T. J., Schleper, C., Preston, C. M., Roberts, K., Richardson, P. M., and DeLong, E. F. (2006). Pathways of carbon assimilation and ammonia oxidation suggested by environmental genomic analyses of marine Crenarchaeota. Plos Biology 4, 520-536. 

Schmidt, I., van Spanning, R. J. M., andjetten, M. S. M. (2004b). Denitrification and ammonia oxidation by Nitrosomonas europaea wild-type, and NirK- and NorB-deticient mutants. Microbiology-Sgm 150, 4107-4114. 

First-principle quantum chemical methods have advanced to the stage where they can now offer qualitative, as well as, quantitative predictions of structure and energetics for adsorbates on surfaces. Cluster and periodic density functional quantum chemical methods are used to analyze chemisorption and catalytic surface reactivity for a series of relevant commercial chemistries. DFT-predicted adsorption and overall reaction energies were found to be within 5 kcal/mol of the experimentally known values for all systems studied. Activation barriers were over-predicted but still within 10 kcal/mol. More specifically we examined the mechanisms and reaction pathways for hydrocarbon C-H bond activation, vinyl acetate synthesis, and ammonia oxidation. Extrinsic phenomena such as substituent effects, bimetallic promotion, and transient surface precursors, are found to alter adsorbate-surface bonding and surface reactivity. 

At a higlier temperature (> 400 °C), ammonia oxidation wath oxygen becomes substantial, and a certain reaction competition is expected between NO reduction and ammonia oxidation. The utilization of amiuonia for NO reduction was high (> 80 %) up to 500 °C, and starts declining at 600 °C (Fig. 1). 

The mechanism of oxidative deamination foiiows a pathway simiiar to that of N-deaikyiation. initiaiiy, oxidation to the imminium ion occurs, foiiowed by decomposition to the carbonyi metaboiite and ammonia. Oxidative deamination can occur with a-substituted amines, exempiified by amphetamine (Fig. 10.13). Disubstitution of the a-oarbon inhibits deamination (e.g., phentermine). Some secondary and tertiary amines as weii as amines substituted with buiky groups can undergo deamination directiy, without N-deaikyiation (e.g., fenfiuramine). Apparentiy, this behavior is associated with increased iipid soiubiiity. 

Standard SCR reaction (10.13), the reactions of adsorption-desorption of NH3, and ammonia oxidation to N2 (10.8) were considered and the kinetic expressions discussed in the previous sections were used jointly with each one of the SCR rate expressions introduced in the following. 

Adsorbed state of oxygen. Research on the adsorbed state of oxygen plays an important role in the reactive mechanism study of catalytic oxidation of hydrocarbon molecules and ammonia oxidation. In general, the adsorptive states of oxygen in the transition metal oxides and metal catalysts are the negative ion type, such as O, O, and 0 etc. Of course, there are also molecular O2, as well as unstable O3 etc. 

It has been suggested that the practical similarities between methanol and ammonia oxidation led to the more rapid development of platinum gauzes for nitric acid production during the 1914-1918 war. Large-scale production of formaldehyde did not become important until the demand for phenol-formaldehyde plastics developed in the 1920s. With so little information available on the production of formaldehyde, it is more likely that the experience gained from ammonia oxidation in the wartime plants was then applied to the manufacture of formaldehyde. 

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