Catalytic decomposition approximations

The SWNTs produced by laser-vaporization and arc discharge are usually capped by fullerene-like structures. Those from catalytic decomposition are usually capped by metal particles. Ye et al. (1999) and Dillon et al. (2000) both used ultrasonication to open the tubes. In the work of Dillon et al. (2000), it was reported that by using the ultrasonic probe of Ti-alloy (with 9 wt % Ti, 6 wt % Al, and 4 wt % V), the alloy (T1AI0.1V0.04) was incorporated into the SWNTs as contamination. The maximum adsorption capacity was 7 wt %, and upon TPD, two desorption peaks occurred approximately 2.5% evolved at 300 K, while the remainder evolved between 475-850 K. It was suspected that the alloy contaminant acted as a catalyst that stimulated the adsorption and desorption. This... 

The rate equation [eqn. (26)], given above for the reaction of magnesium oxalate, is also obeyed [1012] by the decomposition of zinc oxalate (620—646 K), although here the catalytic (second) term is dominant, so that behaviour approximated to the Prout—Tompkins equation [eqn. (9)]. The value of E (201 8 kJ mole 1) was the same as that found... 

Equilibrium studies under anaerobic conditions confirmed that [Cu(HA)]+ is the major species in the Cu(II)-ascorbic acid system. However, the existence of minor polymeric, presumably dimeric, species could also be proven. This lends support to the above kinetic model. Provided that the catalytically active complex is the dimer produced in reaction (26), the chain reaction is initiated by the formation and subsequent decomposition of [Cu2(HA)2(02)]2+ into [CuA(02H)] and A -. The chain carrier is the semi-quinone radical which is consumed and regenerated in the propagation steps, Eqs. (29) and (30). The chain is terminated in Eq. (31). Applying the steady-state approximation to the concentrations of the radicals, yields a rate law which is fully consistent with the experimental observations ... 

Nitric oxide is commercially produced by the catalytic oxidation of ammonia using a platinum catalyst 4NH3(g) + 50 —> 4NO(g) + 6H20(g). Nitrous oxide is produced by the thermal decomposition of ammonium nitrate at approximately 240°C NH4N03(g) —> N O + 2H . ... 

The data in Table 11 show some facts, the mechanistic consequences of which will be discussed in Sect 2.4.4. The 2-alkene/l-alkene ratio for the catalytic reaction differs significantly from that for the homogeneous decomposition. On all catalysts, this ratio is higher for the 2-bromo-than for the 2-chloro-derivative therefore the orientation also depends on the nature of the halogen. On some catalysts, both ratios (the 2-/1- and cis/ trans) are equal or approximately the same as the equilibrium values, but on other catalysts, significant differences appear. 

Hiatt et a/.34a-d studied the decomposition of solutions of tert-butyl hydroperoxide in chlorobenzene at 25°C in the presence of catalytic amounts of cobalt, iron, cerium, vanadium, and lead complexes. The time required for complete decomposition of the hydroperoxide varied from a few minutes for cobalt carboxylates to several days for lead naphthenate. The products consisted of approximately 86% tert-butyl alcohol, 12% di-fe/T-butyl peroxide, and 93% oxygen, and were independent of the catalysts. A radical-induced chain decomposition of the usual type,135 initiated by a redox decomposition of the hydroperoxide, was postulated to explain these results. When reactions were carried out in alkane solvents (RH), shorter kinetic chain lengths and lower yields of oxygen and di-te/T-butyl peroxide were observed due to competing hydrogen transfer of rm-butoxy radicals with the solvent. 

Other metals, the commonest being lead,2 bismuth, and manganese, in powder form exert a more moderate effect on the decomposition. Mercury would also fall into this class of moderate accelerators, but the catalytic action in this case is remarkable in being periodic or rhythmic. When the concentration of hydrogen ion is reduced to an almost negligible quantity by the addition of a little sodium acetate solution, a clean mercury surface in contact with hydrogen peroxide solution of approximately 10 per cent, concentration, at periodic intervals of about one second, becomes coated with a bronze film which suddenly disappears with a burst of oxygen from the contact layer of the two liquids the substance of the film, which is alternately formed and decomposed, is probably an unstable oxide, possibly mercurous peroxide.3... 

An early study" " of the decomposition of sodium perborate in aqueous solution indicated that the process is not kinetically simple. Although approximately first-order, the reaction is said to be subject to retardation (possibly due to reversibility) by the reaction products and to slight acceleration by polymeric borate species. A number of catalytic species were found and others have been reported since, e.g. Wilson" and Prokopeikas et The reaction with iodide has been used as the basis for a kinetic method of analysis for molybdate". ... 

P10-25c The decomposition of spartanol to wulfrene and CO2 is often carried out at high temperatures [/ Theor. Exp., 15, 15 (2014)]. Consequently, the denominator of the catalytic rate law is easily approximated as unity, and the reaction is first-order with an activation energy of 150kJ/mol. Fortunately, the reaction is irreversible. Unfortunately, the catalyst over which the reaction occurs decays with time on stream. The following conversion-time data were obtained in a differential reactor ... 

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