Dehydrogenation of 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. 

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

For the purpose of demonstrating the superheated liquid-film-type catalysis in a continuous operation on a bench scale, catalytic dehydrogenation of decalin using a continuous reactor together with a new supporting material was investigated [10,11]. 

Shinohara, C., S. Kawakami, T. Moriga, H. Hayashi, S. Hodoshima, Y. Saito, and S. Sugiyama, Local structure around platinum in Pt/C catalysts employed for liquid-phase dehydrogenation of decalin in the liquid-film state under reactive distillation conditions. Appl. Catal. A, 266(2), 251-255 (2004). 

Pt-C (by Kaffer).158 To 10-12 g of active carbon mixed well with water is added an aqueous solution of the calculated amount of chloroplatinic acid. The mixture is warmed on a water bath for a few hours at 50°C. After cooling, a concentrated sodium carbonate solution is added until the mixture becomes alkaline. Then a hydrazine hydrate solution is added drop by drop under stirring. Whether the amount of hydrazine is sufficient to reduce the chloroplatinic acid can be readily determined by the decoloration of a permanganate solution. The platinum-carbon suspension is further warmed for 1-2 h on a water bath, filtered, and washed with hot water until the washing is free from chloride and alkali. After dried as fully as possible between filterpapers, the catalyst is dried for half a day over calcium chloride in vacuum. Kaffer used a 10% Pt-C thus prepared for the dehydrogenation of decalin and found it much more effective than Pt-asbestos by Zelinsky. Newhall used a 5% Pt-C by Kaffer for... 

If there are two solid phases, the action of carriers should be mentioned first. The carriers, as distinct from the second component of the mixed catalyst, usually do not change the activation energy e. Thus, it was found that on dehydrogenation of decalin on Pt on charcoal e =... 

Considerably more energetic conditions are required for dehydrogenatioa of perhydrogenated compounds. Thus, whereas tetralin is dehydrogenated in the liquid phase in the presence of platinum or palladium catalysts at 185°, a temperature of at least 300° is necessary for dehydrogenation of decalin.119... 

Due to slow kinetics, the conventional heterogeneous catalysis of the dehydrogenation of decalin in the solid-gas phase is performed at temperatures of more than 400 °C, which might result in the formation of by-products or carbonaceous deposit on the catalyst in addition to thermal energy loss. In a recent study, an attempt was made to apply the so-called liquid-film concept to hydrogen evolution from decalin with carbon-supported platinum-based catalysts under reactive distillation conditions in order to obtain high electric power suflficient for PEMFC vehicle operations in the temperature range 200-300°C [236]. 

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. 

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]. 

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... 

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). 

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. 

The catalysis pair of decalin dehydrogenation/naphthalene hydrogenation is usable as a hydrogen storage medium loaded in hydrogen vehicles. Here, the power density obtainable from decalin is the most significant factor for the onboard application. 

Hodoshima, S., and Y. Saito, Characteristics of decalin dehydrogenation catalysis in the superheated liquid-film state for mobile storage of hydrogen. /. Chem. Eng. Jpn., 37(3), 391-398 (2004). 

The author and Isagulyants (70) investigated the dehydrogenation of cyclohexane (I) and decalin (II)... 

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