Dehydrogenation activity

The carbocation may rearrange, eliminate a proton to produce an olefin, or crack at a beta position to yield an olefin and a new carbocation. Under an atmosphere of hydrogen and in the presence of a catalyst with hydrogenation-dehydrogenation activity, the olefins are hydrogenated to paraffinic compounds. This reaction sequence could be represented as follows ... 

The CF and GF represent the coke- and gas-forming tendencies of an E-cat compared to a standard steam-aged catalyst sample at the same conversion. The CF and GF are influenced by the type of fresh catalyst and the level of metals deposited on the E-cat. Both the coke and gas factors can be indicative of the dehydrogenation activity of the metals on the catalyst. The addition of amorphous alumina to the catalyst will tend to increase the nonselective cracking, which forms coke and gas. 

Improvement of dehydrogenation activities for decalin by carbon-supported composite catatysts under superheated Uquid-fihn conditions... 

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) ). 

EfiSdent hydrogai supply firm decalin at modoate temperatures of below 250°C was acomplished by utilizing the superheated liqirid-film- pe catalysis under reactive distillation conditions in the present study. The composite catalysts in Ak liquid-film states improved dehydrogenation activities for decalin. 

Ruthenium NHC dihydride complex 26 was found to exhibit interesting reversible hydrogenation/dehydrogenation activity (Scheme 10.11) [35,36]. When excess acetone was used as a hydrogen acceptor, dehydrogenation of several alcohols was achieved (Table 10.5). 

Therefore, the high activity of Cu/Si02 in transferring hydrogen from a donor alcohol may be due not only, as already mentioned, to its ability to activate molecular H2, but also to its dehydrogenation activity. 

Fig. 6. Activities of copper-nickel alloy catalysts for the hydrogenolysis of ethane to methane and the dehydrogenation of cyclohexane to benzene. The activities refer to reaction rates at 316° C. Ethane hydrogenolysis activities were obtained at ethane and hydrogen pressures of 0.030 and 0.20 atm., respectively. Cyclohexane dehydrogenation activities were obtained at cyclohexane and hydrogen pressures of 0.17 and 0.83 atm, respectively (74).

Dehydrogenation Activities for Decalin and Tetralin under Superheated Liquid-Film Conditions... 

Dehydrogenation activities, compared for tetralin and decalin [5,12] under the same superheated liquid-film conditions over the same Pt/C catalyst, exhibited around 3.9-63 times preference of tetralin (Table 13.3), which can certainly be ascribed to advantageous adsorption due to the a-bonding capability of its aromatic part [17-19]. It was, thus, confirmed experimentally that tetralin is superior to decalin as the organic hydrogen carrier for stationary applications in terms of rapid hydrogen supply or power density, provided that the density of fuel storage is unimportant. 

Contrast between decalin isomers on the molecular structures of adsorption resulting in different dehydrogenation activities. 

Figure 13.19a shows a relationship of the catalyst-layer temperature during the reaction with the feed rate of decalin in the continuous operation. The smaller the feed rate of decalin, the higher the catalyst-layer temperature. It was also revealed that dehydrogenation activities for decalin were dramatically changed in accordance with the feed rate of decalin (Figure 13.19b and 13.19c). 

Time courses of dehydrogenation activities with carbon-supported platinum catalyst under superheated liquid-film conditions in laboratory-scale continuous operation. Catalyst platinum nanoparticles supported on granular activated carbon (Pt/C, 5 wt-metal%), 1.1 g. Feed rate of tetralin 0.5 mL/min (superheated liquid-film conditions). Reaction conditions boiling and refluxing by heating at 240°C and cooling at 25°C. (Reproduced from Hodoshima, Sv Shono, A., Satoh, Kv and Saito, Yv Chem. Eng. Trans8,183-188, 2005. With permission.)... 

In addition, the more the number of piled catalyst sheet, the larger the dehydrogenation activities in the liquid-film state especially, as evident in Figures 13.23 and 13.24. It is easy for the liquid reactant to penetrate into the catalyst layer consisting of the ACC with lots of air space. By piling the ACC, therefore, decalin would penetrate into catalyst layer further and be kept in it for a long time, resulting in an enhanced catalytic performance. 

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