Cyclohexene hydrogenation rate constant

GL 16] [R 12] [P 15] As excess of cyclohexene was used, the kinetics were zero order for this species concentration and first order with respect to hydrogen [11]. For this pseudo-first-order reaction, a volumetric rate constant of 16 s was determined, considering the catalyst surface area of 0.57 m g and the catalyst loading density of1g cm. ... 

This kinetic equation is applied to the observed kinetic curves obtained in cyclohexene hydrogenation (model reaction) following the molecular hydrogen consumption. Of note, the present kinetic equation provides the value of fe2obs and not kj. However, the real value of the rate constant k2 can be obtained easily using the relationship k2 = k2obs x S/C, where S/C is the substrate/catalyst molar ratio (the catalyst is given as the number of metaUic moles employed). 

The overall course of reaction depends on the relative rate constants for the various secondary radical processes. Aliphatic ketones are often photoreduced to secondary alcohols (4.121, but although there are interesting features in the stereochemistry of the reduction, the method is not a worthwhile alternative to thermal reduction using hydride reagents, except in cases where the substrate is sensitive to basic conditions. Photoaddition of methanol is promoted in the presence of titaniurnfiv) chloride, both for acyclic and cyclic (4.33) ketones the titanium involvement probably starts in the early steps of the reaction, but the detailed mechanism is not known. Addition may also be a major pathway when cyclohexene is used as hydrogen source (4.341 unlike many other simple alkenes, cydohexene does not readily give oxetanes by photocycloaddition (see p. 126). 

Michael BD, Hart EJ. The rate constants of hydrated electron, hydrogen atom, and hydroxyl radical reactions with benzene, 1,3-cyclohexadiene, 1,4-cyclo-hexadiene, and cyclohexene. J Phys Chem 1970 74 2878-2884. 

This procedure did not alter the sulfur contents listed in Table L In the following the rate constant for cyclohexen e hydrogenation at 175°C, 225 psia total pressure and 5.9 psia C partial pressure is used as a measure of relative activity. 6... 

Figure 3. Variation of rate constant for cyclohexene hydrogenation, k, with time on stream for deactivated catalysts. Conditions reaction temperature, 175°C and total pressure, 225 psia. Key O, AM-C , NU-A , NU-E , AM-D NU-B A, AM-F and A, NU-F.

Benzene appears to inhibit isomerization with Pt and Rh catalysts however, the effect may be due in part to differences in the solubility of hydrogen in the solvents. Tlie rate of hydrogenation of cyclohexene catalyzed by Pt/Si02 is independent of the solvent, including benzene, provided that the concentration of dissolved hydrogen is used in the rate expression. With Pd however, the corrected rate constants are smaller in benzene and smaller still in xylene, than in nonaromatic solvents. ... 

Attempts have been made to estimate the concentration of active sites on a series of Co-Mo/AI2O3 catalysts by irreversible oxygen adsorption at 195 K on the reduced catalysts. There was a linear relationship between areal rate constants for cyclohexene hydrogenation and thiophen hds over the sulphided catalysts (623 K, 1 atm). For the most active catalyst [M0O3, 10.4% (Co + Mo), 0.10 Co/(Co + Mo), 0.17] the concentration of active... 

Catalytic functionalities of sepiolite supported Mo-sulfided catalysts were evaluated using thiophene hydrodesulfurization and cyclohexene hydrogenation reactions at 400 C. The presulfidation was carried out at 400°C for 2 hrs with mixture of CS2 and Hz- In both the cases first order rate constants are evaluated. The results of such experiments as a function of Mo-loading is given in table 2 and the activity of HDS and HYD reaction as a function of Mo-loading is shown in figure 5. 

The two terms arise from the two principal species present under catalytic cyclohexene hydrogenation conditions—RhClL3 and H2RhClL3, respectively. An additional constant term, like that shown in Rate Law No. 4 in Table 2.2, is not necessary unless a significant amount of another intermediate [H2RhClL2(S)] is also present in the system under conditions where the rate law applies, t... 

Titanium. Catalyses of hydrogenation of alkenes, alkynes, carbonyl-, and nitro-compounds have been described. The effect of the nature of the ligand L and of the alkene to be reduced on reactivity in catalytic hydrogenation by Ti(7r-C5H5)2L2 has been quantitatively studied. The dependence of rate constants on solvent for reduction of decene in the presence of Ti(7r-C5H5)Me+ is interpreted in terms of electrostatic interaction between the active ionic species and the solvent. There is also a thermochemical report relevant here, and that is of a determination of the heats of mixing of cyclohexene and of hex-l-ene with titanium tetrachloride. The heats of mixing are close to zero, which implies very small heats of complex formation between these alkenes and titanium. ... 

Interfacial areas per unit volume in falling-film microreactors have been reported to be as high as 25,000 m m, as compared with the values of 1-200 m m typical in bubble columns. This effect is particularly important in gas-liquid reactions because the rate of mass transfer from the gas to the liquid limits the reaction rate. For the hydrogenation of cyclohexene to cyclohexane in this type of reactor, the mass transfer rate constant Kid) was found to be in the range 3-7 s which is two orders of magnitude higher than that for conventional reactors. 

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