Direct decomposition

The diazonium hydrogen sulphate is used for this reaction in preference to the diazonium chloride since the latter by direct decomposition always forms small quantities of the chloro-hydrocarbon as a by-product ... 

In the two-dimensional case the iterative alternating direction method or the direct decomposition method turns out to be more economical, but for the multidimensional Dirichlet problem ATM is the most economical one among other available methods. This advantage is stipulated by the special structure of the operator A (see Chapter 4, Section 5) ... 

Zinc oxide is made either by the oxidation of the metal in oxygen (the indirect, IP, or French process), by the direct decomposition of zinc ores in air (the direct or American process) or by the thermal decomposition of zinc salts (TD zinc oxide). IP zinc oxides differ from TD zinc oxides in that their surfaces do not contain absorbed water. Also, whereas TD zinc oxide reacts with plain eugenol, IP zinc oxide hardly reacts unless activated by an acetic add or zinc acetate accelerator (Table 9.2). 

To finish with another trend for NO removal consisting in NO direct decomposition, we would like to depict the infrared study of NO adsorption and decomposition over basic lanthanum oxide La203 [78], In this case, the basic oxygens are proposed to lead to N02 and N03 spectator species, whereas the active sites for effective NO decomposition are described as anion vacancies, which are often present in transition metal oxides. This last work makes the transition with the study of DeNO, catalysts from the point of view of their ability to transfer electrons, i.e. their redox properties. 

Groothaert et al., using operando UV-vis spectroscopy combined with online GC analysis [176] and operando X-ray absorption fine structure (XAFS) [177], presented the first experimental evidence for the formation of the bis( x-oxo)dicopper core in Cu-ZSM-5 and for its key role of intermediate in the sustained high activity of Cu-ZSM-5 in the direct decomposition of NO into N2 and 02. In particular, monitoring the catalytic conversion of NO and N20 above 673 K, they found that the bis( x-oxo)dicopper core is formed by the O abstraction of the intermediate N20 (Figure 4.14). Subsequently,... 

Further study of the direct decomposition revealed that the reaction could not be quenched by the presence of piperylene thus, decomposition must result either from singlet-excited azide or from triplet azide at a rate on the order of 1011 sec"1/471... 

Despite several decades of studies devoted to the characterization of Fe-ZSM-5 zeolite materials, the nature of the active sites in N20 direct decomposition (Fe species nuclearity, coordination, etc.) is still a matter of debate [1], The difficulty in understanding the Fe-ZSM-5 reactivity justifies a quantum chemical approach. Apart from mononuclear models which have been extensively investigated [2-5], there are very few results on binuclear iron sites in Fe-ZSM-5 [6-8], These DFT studies are essentially devoted to the investigation of oxygen-bridged binuclear iron structures [Fe-0-Fe]2+, while [FeII(p-0)(p-0H)FeII]+ di-iron core species have been proposed to be the active species from spectroscopic results [9]. We thus performed DFT based calculations to study the reactivity of these species exchanged in ZSM-5 zeolite and considered the whole nitrous oxide catalytic decomposition cycle [10],... 

When one CO in the octacarbonyl is replaced by C4H202 direct decomposition is again the rate-controlling process provided [P(C6H5)3] >0.1 M. The mechanism proposed by Heck24 is... 

The singlet carbene can undergo intersystem crossing to the triplet carbene the latter on the other hand, can also be formed by direct decomposition of the excited triplet state of the diazo compound. These possibilities are shown in the foUowing scheme ... 

Production of hydrogen by direct decomposition of hydrogen sulfide has been studied extensively (Clark et al., 1995 Zaman and Chakma, 1995 Luinstra, 1996). Hydrogen sulfide decomposition is a highly endothermic process and equilibrium... 

Copper Ion-exchanged Zeolites as Active Catalysts for Direct Decomposition of Nitrogen Monoxide... 

Recently a few reports have claimed that direct decomposition of NO is successfully catalyzed... 

The advantage of this radiation chemical method is that the by-products of radical ions are scarcely generated, because the direct decomposition of solute molecules by ionizing radiation is negligible due to low solute concentration. Another advantage is that the molecular orbitals of radical ions are scarcely disturbed by their counterpart ions, because electrons or holes are captured by solute molecules after traveling more than 5 nm from the point of ionization [34]. 

The para-nitro ester 71d generated only 4-nitroaniline (70%) and 4,4 -dinitroazoxybenzene (10%) when it underwent decomposition (Scheme 29). These products could have been derived from either a triplet nitrene or a triplet nitrenium ion precursor. Homolysis of the N—O bond to generate radical intermediates was ruled out because of the nearly quantitative yield of pivalic acid derived from 71d. The pivaloxy radical would have undergone rapid decarboxylation to generate CO2 and the rert-butyl radical under these conditions. Since no rearrangement product was observed, it was tentatively concluded that this ester underwent direct decomposition to 4-nitrophenyl-nitrene without the intermediacy of a nitrenium ion. ... 

Note, however, that this sequence is not universal that is, carbon can be formed by the direct decomposition of CnHm as shown in reaction (7). 

This precipitate dissolves in thiosulphate to form a thiosulphate complex, which, in common with other metal thiosulphate complexes, decomposes when heated to the metal snlphide (see Sec. 3.3.3). Besides direct decomposition of the thiosnlphate complex, another possibility suggested in this study is formation of snlphide ion by alkaline hydrolysis of thiosulphate [Eqs. (3.20) to (3.24)] and reaction with Hg to form HgS. The substrates were glass precoated with a very thin film of CD PbS (presnmably this improved adherence and/or homogeneity). 

The NOx reduction for the exhaust from lean-burn engine is one of the greatest challenges in environmental protection, and a lot of researchers have strived to develop more effective catalysts by many ways. Their efforts could be possibly categorized into four approaches (1) NOx direct decomposition, (2) selective catalytic reduction on NOx with hydrocarbons (HC SCR),... 

NOx direct decomposition seems the most attractive solution in emission control, because the reaction does not require any reductants added and potentially could lead to the formation of only N2 and 02. Cu zeolite is one of the best catalysts for NOx direct decomposition, but the activity is very poor and needed to be improved several orders of magnitude high (Iwamoto et al., 1981). 

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