Capacity redox

In contrast to NaZSM-5 zeolite, introduction of CoZSM-5 or HZSM-5 zeolite in the reaction system shifts the "light-off" temperature and modifies the chemistry now not only NO but Nj is formed. Hence, some intermediate species required for Nj formation must be stabilized on the catalyst surface. The "light-off"temperature shifts observed with CoZSM-5 and HZSM-5 catalysts may result from the enhanced redox capacity provided by these catalysts or from the NOj/NO equilibrium achieved more readily than with NaZSM-5. Moreover, equilibrium is approached at a somewhat lower temperature over CoZSM-5 than HZSM-5, and much lower than with the empty reactor (see Fig. 1 of Ref. lOl.The decomposition reaction of NOj into NO -t- occurs readily on these catalysts and the "light-off" temperature of both combustion and SCR is lower in comparison with that of the homogeneous reaction. 

The slope of the tangent to the curve at the inflection point where oc = is thus inversely proportional to the number of electrons n. The E-oc curves are similar to the titration curves of weak acids or bases (pH-or). For neutralization curves, the slope dpH/doc characterizes the buffering capacity of the solution for redox potential curves, the differential dE/da characterizes the redox capacity of the system. If oc — for a buffer, then changes in pH produced by changes in a are the smallest possible. If a = in a redox system, then the potential changes produced by changes in oc are also minimal (the system is well poised ). 

The present discussion is only concerned with the structure/redox capacity of the site responsible for the oxidation of water. The starting point is the evidence that the photosynthetic pathway is triggered by photooxidation of the chlorophylls in photosystem II. The need for chlorophylls to recover the electrons lost in photooxidation (in order to regenerate their ability to absorb light) induces water to undergo oxidation, according to ... 

C70, which is the second easiest carbon cluster to prepare, has essentially the same redox capacity as C60, Figure 16.17... 

Recently, however, the interest in their redox capacity is growing in relation to their potential use as conducting materials, thus the... 

To conclude this brief review of homonuclear metal-sulfur clusters we consider the Ni9S9 assembly present in the dication [Ni9S9(PEt3)6]2+, which highlights the spectacular structure and high redox capacity of this cluster, Figure 19.la... 

The electrochemical reduction of nitric oxide in solid-state electrochemical cell is an interesting field surveyed in [95]. The working principle of the cells is the cathodic reduction of NO to nitrogen and oxygen anions. In [95], the properties of various types of solid-state electrochemical cells used for NO reduction are presented and discussed. It is shown that the cathode materials with a high redox capacity and oxygen vacancies are most active for the electrochemical reduction of nitric oxide, whereas noble metal-based electrodes show a much lower selectivity. As an alternative route, the promotion of the reduction with a reductive agent is also considered. 

Bartnicki, E. W., N. O. Belser, and C. E. Castro, Oxidation of heme proteins by alkyl halides A probe for axial inner sphere redox capacity in solution and in whole cells , Biochemistry, 17, 5582-5586 (1978). 

The most confusing aspect of the pathway proposed by Ochoa and his group now rests with the NAD requirement. In proceeding from L-malic acid to L-lactic acid, there is no net change in oxidation state. Yet in whole cells or cell-free extracts, the malo-lactic fermentation will not proceed in the absence of NAD. Therefore, by the proposed mechanism, one is unable to demonstrate the appearance of reduced cofactor, and the NAD specificity cannot be explained as a redox requirement. However, in the time since this mechanism was proposed, an NAD dependent enzyme (glyceraldehyde-3-phosphate dehydrogenase) has been described which requires NAD in a non-redox capacity (29), and it is possible that the same is true for the enzyme causing the malic acid-lactic acid transformation. 

It must be expected that a polymer material having a much lower conductivity than polyaniline will give impedance responses revealing the effect of the three time constants obtained in the model. The system investigated was chosen for this reason since pECBZ conductivity and redox capacity [94] correspond to DE = 10 7cm2,s 1 and therefore, for the same layer thickness (500nm), the diffusion time constant would be 0.025 s. Electron diffusion should therefore be detectable in the a.c. and even in the EHD frequency domain. 

A variety of different metal complexes have been screened as catalysts for allylic amination using phenyl hydroxylamine 108 as the nitrogen fragment donor, and it was found that iron-complexes have better redox capacity compared to molybdenum [64]. With the iron compounds, higher yields and a lower amount of hydroxylamine-derived byproducts are obtained. These byproducts constitute one of the problems in this type of allylic amination reactions in general, as their formation is difficult to suppress. The allylic amination reaction of a-methyl styrene 112 with 108 can, e.g., be catalyzed by the molybdenum dioxo complex 107, iron phthalocyanine 114, or by the combination of the iron chlorides 115 [64,65]. It appears from the results in... 

Pidello, A. Environmental Redox Potential and Redox Capacity Concepts Using a Simple Po-larographic Experiment, /. Chem. Educ. 2003, 80,68-70. 

Oxygen Storage/Redox Capacity and Reiatcd Phenomena on Ceria-Based Catalysts ... 

OXYGEN STORAGE/REDOX CAPACITY AND RELATED PHENOMENA ON CERIA-BASED CATALYSTS... 

Oxygen storage/redox capacity and related phenomena... 

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