Dehydrogenation activity test

A systematic investigation of dehydrogenation activity over a variety of metal alloy catalysts has been made by Schwab and co-workers (51-53), who have successfully interpreted their results in terms of the bulk metal theory. The test reaction used, namely the dehydrogenation of formic... 

Dehydrogenation activity has been demonstrated for Rh, Co, and Ni forms of zeolites X and Y (123-125), Both cyclohexane and tetralin dehydrogenation to benzene and naphthalene, respectively, have been used as test reactions. For NiX zeolites, unreduced Ni2 + ions were considered (124) to be the active centers. The incorporation of Ca2+ ions into the zeolite... 

An early attempt to simulate metals deactivation was the introduction of the Mitchell method steam deactivation procedure (2). This procedure involved impregnation of catalysts with Ni and V naphthenates, followed by steaming in the presence of air. While this method was easy to implement and did allow comparison of catalysts in the presence of metal contaminants, both the destruction of the zeolite and the metal dehydrogenation activity was greatly over-predicted (3, 4) in both MAT and riser testing. 

Test results have shown so far that coke make is very sensitive to dehydrogenation activity, when processing high CCR feed, using catalysts with high nickel and vanadium. In figure 5 is shown how the coke make relates to dehydrogenation activity. 

Quantificahon greatly aids the understanding of the catalytic contributions of different vanadia species during catalytic reactions. For example, our preliminary activity test over these supported catalysts showed that the I.2V/6-AI2O3 sample exhibits better stability than higher loading catalysts for butane dehydrogenation in dilute feed [57]. The explanation is that the monovanadate species (ca 50% on the surface) dilute the polyvanadate species so that the two-dimensional coke species responsible for catalyst deactivation are less likely to form [40, 57]. 

Fig. 2. Relationship between temperature requirement for reforming naphtha to 98 O.N. level and dehydrogenation activity (cyclohexane test).

In Fig. 3 the results are presented for the acidic activities (cumene test), on the ordinate, and the re-forming activities (inlet temperature requirement for 98 O.N. product), as the abscissa. In addition, the dehydrogenation activities (/ moles/sec./g., cyclohexane) of each sample are given with the experimental points. The catalyst samples include alumina-base... 

All samples were submitted to activity tests in the isobutane dehydrogenation reaction. In a previous work [8] results of catalytic tests were presented performed at 550°C with a... 

As one further example, in the middle 60 s we developed a dehydrogenation activity (DA) test which measured the rate constants of reforming or hydrocracking catalysts for converting cyclohexane to benzene. We found that fresh platinum/alumina catalysts had a DA of about 1000. After only one day in a unit the DA dropped to about 1. And, of course, such catalysts are used for months without regeneration in a reforming unit. Now you know why I refer to industrial catalysis as the science of dirty surfaces. 

Chitwood (2) found that copper compounds exhibited only a short period of maximum catalytic activity for the dehydrogenation of ethanolamine to glycine salt. In this study, the catalytic activity of a skeletal copper catalyst was tested in repeated use. The catalyst used was prepared by selectively leaching CuAl2 particles in a 6.1 M NaOH solution at 293 K for 24 hours. Figure 1 shows the profiles of hydrogen evolved versus reaction time. 

Such a possibility has been recognized by early workers,9 but in spite of this intriguing possibility, only recently has such a metal surface been created. Chiral kink sites were created on Ag single crystal surfaces to produce the enantiomeric surfaces Ag(643)s and Ag(643)R however, no differences between (R)- and (S)-2-butanol were observed for either the temperature-programmed desorption from the clean surfaces or the dehydrogenation (to 2-butanone) from preoxidized surfaces.10 Unfortunately, Ag exhibits few catalytic properties, so only a limited array of test reactions is available to probe enantioselectivity over this metal. It would be good if this technique were applied to a more catalytically active metal such as Pt. 

An efficient oxidation catalyst, OMS-1 (octahedral mol. sieve), was prepared by microwave heating of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with microwave radiation, and thus pronounced effects on the microstructure were expected. Their catalytic activity was tested in the oxidative dehydrogenation of ethylbenzene to styrene [25]. 

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