Adsorption Decalin

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. 

The nearly equal amount of cis and trans products formed from 1,5-dimethylcyclo-hexene is explained by the almost equal degree of hindrance of the homoallylic methyl group with the catalyst surface in the alternate adsorption modes.63 64 Another interesting example is the platinum-catalyzed hydrogenation of isomeric octalins.65-67 If syn addition to the double bond is assumed, in principle, both cis- and mms-decalin are expected to result from l(9)-octalin, but only the cis isomer from 9(10)-octalin. In contrast with these expectations, the isomers are produced in nearly the same ratio from both compounds. Transformation in the presence of deuterium revealed that most of the products contained three deuterium atoms. This was interpreted to prove that the very slow rate of hydrogenation of 9(10)-octalin [Eq. (11.9)] permits its isomerization to the 1(9) isomer. As a result, most of the products are formed through l(9)-octalin [Eq. (11.10)] ... 

The preferential attack at position 2 would to be due to the steric mode of adsorption of cis-decalin at the surface of Ti02-... 

Fig. 4a. Adsorption HPLC of polystyrene standards. Column silica (250x2.6 mm d0 = 400 nm dP = 10 pm) gradient decalin/tetrahydrofuran flow rate 0.5 ml/min UV detection at 254 nm. (From Ref. U) with permission), b. SEC of polystyrene standards. Column silica (three columns in series, each 250 x 4 mm nominal pore size 100,500, and 1000A, respectively). In both chromatograms the figures at the peaks indicate the molar mass (kg/mol) of the respective polystyrene standard. (From Ref. li with permission)...

Metallic nanopartides were deposited on ceramic and polymeric partides using ultrasound radiation. A few papers report also on the deposition of nanomaterials produced sonochemically on flat surfaces. Our attention will be devoted to spheres. In a typical reaction, commerdally available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of the metallic nanopartides. In the first report Ramesh et al. [43] employed the Sto-ber method [44] for the preparation of 250 nm silica spheres. These spheres were introduced into a sonication bath containing a decalin solution of Ni(CO)4. The as-deposited amorphous clusters transform to polyciystalline, nanophasic, fee nickel on heating in an inert atmosphere of argon at a temperature of 400 °C. Nitrogen adsorption measurements showed that the amorphous nickel with a high surface area undergoes a loss in surface area on crystallization. 

As soon as analytical procedures became sophisticated enough to detect small amounts of early ideas of Balandin (27) and Linstead (II) relative to complete satiuation of an entire ring by cis addition during a single period of adsorption had to be modified. 

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. 

Because of the small pores in zeolitic catalysts, reaction rates may be controlled by rates of diffusion of reactants and products. Beecher, Voorhies, and Eberly (4) studied hydrocracking of mixtures of n-decane and Decalin with mordenite catalysts impregnated with palladium. They found that acid leaching of the mordenite produces an aluminum-deficient structure of significantly higher catalytic activity. At least part of this improvement appears to be caused by the decrease in diffusional resistance. They observed that with this type of catalyst, the effective catalyst pore diameter appears to be smaller than calculated owing to the strong interaction or adsorption of hydrocarbon molecules on the pore walls. 

Because of unfavorable sorption effects on paper that cause tailing, materials with lower adsorptivity were sought. Thus, cellulose acetate [35] and nitrocellulose [36,37] membranes were introduced. Cellulose acetate can be either prepared in the laboratory by treating cellulose with acetic anhydride, or it may be purchased from commercial sources. Cellulose acetate membranes are readily soluble in phenol, glacial acetic acid, dichloromethane and acetone. In part they can be solubilized in several solvent mixtures e.g., chloroform/ethanol (9 1 v/v). For detection (optical scanning) the foil can be made translucent by immersion in cottonseed oil, decalin, liquid paraffin or Whitemore oil 120. 

In the case of decalin, the extent of reaction is small, and independent of the time of residence on the charcoal, but dependent on the temperature of adsorption. Since the desorption process was standard, irrespective of the temperature, it would appear that the reaction occurs during the adsorption process (or, possibly, that reactive species are produced during... 

Stearic Acid-czs-Decalin Series. The adsorption process of stearic acid from Decalin (Figure 3) is similar to that of the first two acids, with the trend being to still smaller average island diameters for the several stages of monolayer completion. 

The rate of adsorption of cerotic acid was much slower from the hexadecane solutions than from the Decalin solutions this decreased rate is probably at least partially due to the greater viscosity of hexadecane. 

From Decalin solutions, the acid molecules are adsorbed initially in discrete patches which with further adsorption increase in size and number in a fashion dependent on the chain length. 

Perhaps the most striking effect observed in this investigation was the markedly different modes of adsorption of behenic acid from Decalin... 

FIGURE 15.10 Effect of polymer concentration on the kinetics of adsorption onto a silica surface for (a) polystyrene from decalin and (b) subtilisin from water. The polymer fluxes Jf toward the surface are indicated in the figures. (Adapted from Norde, W. and Giacomelli, C.E., Macromol. Symp., 145, 125, 1999.)... 

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