Hydrogen pressure considerations

Hydrostatic pressure considerably increases workability of hydrogenated titanium alloys. Thus, their ductility at 20-250 C exceeds that of the hydrogen-free alloys in the pressure range of 10 kbar. 

Davis 69) found no considerable variation in the o-xylene versus ethylbenzene ratio as a function of hydrogen pressure. He also observed that the relative amount of o-xylene from n-octane increased (a) with decreasing Pt loading of the catalyst (70) b) with increasing tin addition 69, 7J) (c) with the poisoning of the catalyst with thiophene (77) and d) if octenes or octynes... 

We have presented a general reaction-diffusion model for porous catalyst particles in stirred semibatch reactors applied to three-phase processes. The model was solved numerically for small and large catalyst particles to elucidate the role of internal and external mass transfer limitations. The case studies (citral and sugar hydrogenation) revealed that both internal and external resistances can considerably affect the rate and selectivity of the process. In order to obtain the best possible performance of industrial reactors, it is necessary to use this kind of simulation approach, which helps to optimize the process parameters, such as temperature, hydrogen pressure, catalyst particle size and the stirring conditions. 

According to the above considerations if the optimization is performed under fixed process parameters the initial step in library design is finished, i.e. the catalysts of the initial library can be introduced into the experimental hologram. However, it is strongly recommended to include one or two process parameters into the library design procedure. Reaction temperature and hydrogen pressure is the two most important process parameters influencing both the activity and the reactivity. 

Aromatic hydrocarbons are hydrogenated with considerable difficulty, requiring higher temperatures, higher pressures, and longer reaction times than for alkenes or alkynes ... 

The amount of the cis isomer formed in the hydrogenation of 10 at various hydrogen pressures, however, is always considerably lower150 than that formed in the hydrogenation of 9. All these observations can be interpreted by invoking tr-allyl-adsorbed species (11 and 12) instead of 1,2-cr-diadsorbed species as surface intermediates in the hydrogenation over Pd (equations 11 and 12)150. Of the two species, 12 formed from 10 (equation 12) is expected to result in a higher trans ratio. 

The properties of the HF-treated fuller s earth without activators will be discussed first. This material at 200 to 300 atm. pressure showed small splitting activity and high sensitivity to nitrogen bases. At 600 atm. pressure, considerably increased splitting activity was observed. It seems that the activation of the HF-treated fuller s earth obtained by the WS2, which converts it into a dual-function catalyst (41) of increased activity, can also be achieved—at least to some extent—by higher hydrogen pressure. The results obtained with the petroleum distillate used for the experiments in Table XV are shown in Table XIX. The splitting activity... 

In this study we address hydrocracking of VGO at moderate hydrogen pressures (30 bar) and elevated temperatures (450°C) using catalysts with little or no acidity [1]. The moderate pressures are attractive from a capital investment point of view. A potential drawback could be that the severe conditions lead to considerable coke deposition on the catalyst. In order to control the level of catalyst coking a careful balance of catalyst and process parameters is a prerequisite. 

On such bimetallic catalysts the rhenium loading at saturation of a 0.6% Pt/Al2C>3 catalyst depends on the hydrogen pressure. From a thermodynamic point of view the quantity of additive deposited at saturation is defined by the equilibrium conditions of the system under consideration. By taking into account the reduction of Re04 to Re0 at 303 K (Table 1),... 

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