Decalin conversion rate

AXB) shows time courees of amounts of evolved hydrogen and decalin conversions with caibon-supported platinum-based catalysts unda" supeiheated liquid-film conditions. Enhancement of dehydrogenation activities for decalin was realized by using fiiese composite catalysts. The Pt-W / C composite catalyst exhibited the hipest reaction rate at the initial stage, whereas the Pt-Re / C composite catalyst showed the second highest reaction rate in addition to low in sensitivity to retardation due to naphthaloie adsorbed on catalytic active sites [1-5], as indicated in Fig. 2(A) ). 

EfiBdent hydrogen supply iiom decalin was only accomplished by the si terheated liquid-film-type catalysis under reactive distillation conditions at modaate heating tempaatures of 210-240°C. Caibcm-supported nano-size platinum-based catalysts in the si ietheated liquid-film states accelerated product desorption fixjm file catalyst surface due to its temperature gradient under boiling conditions, so that both hi reaction rates and conversions were obtained simultaneously. 

When the catalyst was suspended uniformly in 3.0 mL decalin, not only low initial rates of hydrogen generation but also poor 2.5 h conversions were obtained in spite of the excess amounts of substrate in the reaction medium. 

At large feed rates (1.1-2.3 mL/min at 230°C, 3.4 mL/min at 270°C), the catalyst temperature in each immersed state was almost equal to the boiling point of decalin (192°C). These catalysts were suspended uniformly in sufficient amounts of decalin solution, resulting in low catalytic conversions comparatively (Figure 13.19b). 

Relationship of dehydrogenation activities with feed rate of decalin in bench-scale continuous operation, (a) Stationary rate of generated hydrogen and (b) stationary conversion. Catalyst platinum nanoparticles supported on ACC (5 wt-metal%), 0.29 g (one layer, ), 0.58 g (two layers, A), and 0.87 g (three layers, O). Reaction conditions boiling and refluxing by heating at 280°C and cooling at 25°C. 

Concentrations of total octalins are plotted in Fig. 6 as a function of conversion beyond the tetralin stage. The sharp drop in octalin content in early stages of the reaction is largely due to easy saturation of octalins other than A i -octalin. Extrapolation toward zero conversion suggests that most or all of the decalins have octalin precursors. The curves fall generally into two families depending on the rates of saturation of the octalins relative to tetralin. With rhodium, and to a lesser extent with ruthenium, the lined-out concentration remains high, due primarily to the accumulation of A -i -octalin. With palladium, platinum, and iridium, the initial octalin concentrations fall precipitously and line out at low values because all octalin isomers are adsorbed and saturated rapidly relative to tetralin. 

Actually, rhodium and iridium can be used as well as ruthenium in mixtures with palladium. The results, however, allow only the qualitative statement that olefins are significant intermediates. The presence of more than one olefin isomer and uncertainty of the precise ratios of formation and rates of migration preclude any quantitative estimate. The experiments with mixed catalysts were terminated after 20 to 50% conversion. The mixed catalysts not only gave higher yields of (raws-decalin but the actual concentrations of the octalins present in the reaction mixture were lowered owing to preferential adsorption on the palladium component. 

The reactions of these octalins with deuterium, to yield deuterated cis- and irowa-decalins, has also been investigated (14). In each case the exchange rate is 10-20 times slower than the rate of addition, and deuterium contents of the two decalins are about the same. However, the decalins formed from d -octalin were the more extensively deuterated (deuterium contents at 55% conversion, 2.85, 2.85 at 37% conversion, 2.02, 1.83). Hydrogen exchange was apparent during the reaction of d -octalin but not with the d -octalin. A theoretical scheme was developed to interpret the distributions of the deuterated decalins, the tails of which decline in the familiar logarithmic manner (see Fig. 16). 

Adamantane and cis-decalm were hydroxylated with high selectivity, complete stereo-retention, extraordinarily high rates (up to 800 turnovers min ), and high efficiency with up to 15,000 turnovers. Similar conversions were obtained when Ru(VI)(TPFPP)(0)2 and Ru(VI)(TPFPBr8P)(0)2 were used as catalysts. Oxygenation of less reactive substrates such as benzene and cyclohexane proceeded with lower but still significant turnover numbers (100-3,000). Tertiary vs secondary selectivity in adamantane oxidation was above 210. No rearrangement products were detected in cw-decalin hydroxylation. 

Significant differences in the acetylation of naphthalene with acetic anhydride (2 1 molar ratio) over HBEA are observed with decalin or sulfolane as solvents the diffoent hydrophilicities of these solvents dramatically inflnence the resulting naphthalene conversion. The hydrophilic sulfolane into-acts more strongly with the zeolite surface, thus blocking the acid sites that are less available for the acylation reaction (naphthalene conversion = 14%) on the contrary, the hydrophobic decalin enables the adsorption of acetic anhydride and increases the rate of acylation reaction (naphthalene conversion=25%). Due to the defined structure of the HBEA, the selective formation of isoma-15 is probably achieved via a restricted transition state selectivity (15 13=81 19 at 35% naphthalene conversion). It must be underlined that different secondary products are, in general, produced on the catalyst surface due to consecutive reaction of the products. 

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