Decalin dehydrogenation

To a solution of 50 grams of 6,7-dimethoxy-3-methyl-T(4 -ethoxy-3 -methoxybenzyl)-dihy-droisoquinoline base in 200 ml of dry benzene are added 150 ml of decalin, and the mixture is distilled until its temperature reaches 180°C. 1.5 grams of 5% palladium on carbon are then added. The mixture is stirred under reflux for about 6 hours to dehydrogenate the dihydroisoquinoline. On cooling, the reaction mixture is diluted with petroleum ether and the precipitated 6,7-dimethoxy-3-methyl-1-(3 -methoxy-4 -ethoxybenzyl)-isoquinoline is filtered off and recrystallized from dilute ethanol. 

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. 

Liquid film state under reactive distillation conditions for the dehydrogenation of decalin on platinum supported on active carbon and boehmite... 

The dehydrogenation of decalin to naphthalene has been investigated on Pt/C, Pt/A1(0H)0 and Pt/Al203 catalysts. The maximum conversion of decalin on 3.9% Pt/C, which did not repel decalin, was observed at 483 K under the conditions of 0.3 g of the catalyst and 1ml of decalin, which was corresponded to the liquid film state under reactive distillation conditions. However such a maximum was not observed on Pt/Al(OH)0 and Pt/Al203, which repelled decalin. Furthermore it was found that the reaction temperature, at which the maximum hydrogen evolution was observed on Pt/C, was shifted from the boiling point of decalin to that of naphthalene with increasing the amormt of naphthalene in the reaction solution. 

Figure 1 shows the effects of the volume of decalin on the conversion of decalin on 3.9 wt. % Pt/C (0.3g) (a), 1 wt. % Pt/AlaOa (1.0 g) (b) and 1.46 wt. % Pt/A1(0H)0 (1.0 g) (C) at 483 K. Under those conditions, 0.0117, 0.010 and 0.0146 g of Pt were contained in the systems with Pt/C, Pt/AlaOs and Pt/A1(0H)0, respectively. The conversion of decalin on Pt/C showed to be a maximum at 1 ml of decalin (Fig.l (a)). This point is generally accepted as the liquid film state under reactive distillation conditions, at which the catalyst was just wet but not suspended at all through the dehydrogenation and covered with a thin film of liquid substrate. If such reactive distillation conditions are attained, the dehydrogenation proceeds more efficiently than liquid- and gas-phases [1]. 

Naphthalene itself is solid at ambient temperatures (m.p. 80.5°C) but is dissolved easily in aromatic compounds such as toluene (refer Table 13.1) [10,12], so that the oily mixture can be handled as a "naphthalene oil." The naphthalene oil is catalytically hydrogenated to decalin and methylcyclohexane simultaneously. Decalin and methylcyclohexane are converted into hydrogen and naphthalene oil again by dehydrogenation catalysis. From the handling viewpoint, the naphthalene oil may be deemed as a preferential and practical material for hydrogen storage and transportation. 

Catalytic Dehydrogenation of Decalin and Methylcyclohexane over Carbon-Supported Platinum-Based Nanoparticles under Superheated Liquid-Film Conditions... 

Comparison of Kinetic Parameters for Decalin Dehydrogenation in Superheated Liquid-Film and Suspended States... 

In the adequate case (1.0 or 2.0 mL tetralin), the catalyst appeared to be wet differently from dry sand-bath or suspension states. As in the case of decalin dehydrogenation under the superheated liquid-film conditions, the catalyst temperature is higher than the boiling point, exhibiting a temperature gradient, and the substrate liquid is limited in amount to... 

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. 

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