Activity hydrocracking

Hydrogenation and hydrocracking activity of iron catalysts has been extensively investigated using coal and model compounds (93 -95). Iron catalysts can hydrogenerate olefinic unsaturated bonds, while they are known to be less active for the hydrogenation of aromatic rings compared with molybdenum-based catalysts. 

Overall hydrocracking activity can be considered as the combination of hydrogenation and acidic functions such that, for cyclohe... 

Reforming. The hydrotreated naphthas were reformed over a conventional platinum reforming catalyst in an attempt to maximize aromatics. The catalyst was Cyanamid AERO PHF-4 (0.3% Pt, 0.6% Cl). The intent was to operate the reformer at constant conditions in order to better compare naphthas. By operating at severe conditions, the expected hydrocracking activity of the catalyst would tend to purify the aromatics by selectively cracking away the paraffins. If the resultant reformate had a suitably high aromatic content, it could be fed directly to a hydrodealkylator. 

Lewis et al. (74) showed that P/Al catalysts have low activities for hydrocracking of diisopropylbenzene, and the activity of NiMoP/Al catalysts increases as a result of addition of 1-3 wt% phosphorus. On the other hand, Muralidhar et al. (125) reported that isooctene hydrocracking activity of Co—Mo —P/Al catalysts decreases with increasing phosphorus loading. Iwamoto and Grimblot (67) reported that cyclopropane hydrocracking increases with increasing phosphorus content, especially with NiMoP/Al catalysts (Fig. 26). 

Hydroisomerization/ hydrocracking of n-octane and 2,2,4-trimethylpentane Al-M impr. with Pt. High hydroisomerization/hydrocracking activity conqiarable to Pt-USY. 55... 

On the other hand, it was proposed that acid catalyzed reactions such as skeletal isomerization of paraffin [2], hydrocracking of hydrocarbons [3] or methanol conversion to hydrocarbon [4] over metal supported acid catalysts were promoted by spillover hydrogen (proton) on the acid catalysts. Hydrogen spillover phenomenon from noble metal to other component at room temperature has been reported in many cases [5]. Recently Masai et al. [6] and Steinberg et al. [7] showed that the physical mixtures of protonated zeolite and R/AI2O3 showed high hydrocracking activities of paraffins and skeletal isomerization to some extent. 

Work by Weisz and Swegler has shown the dual-functional (scheme XIII) hydrocracking activity to increase so rapidly with molecular weight, that... 

It is well known that the supported platinum show a high catalytic activity for the dehydrogenation of alkane whereas the supported palladium does not. The results shown in Figure 1 suggest that the dehydrogenation activity of supported metal is not essential for the appearance of the alkane hydrocracking activity. 

Figure 2. Hydrocracking activity of R-HYC catalyst Feed KW-AR, LHSV = 0.3 h l, PH2 = 135 kg cm". ...

Although the exact structure of the such active Fe-species is still needed to examine, such quality control over Fe-species in the Fe-treated Y-zeolites has been applied to the development of commercial resid hydrocracking catalysts. Cormnercial applications using the R-HYC catalyst and resid HDS units have been realized in Idemitsu, Japan, and Valero, U.S.A. [7, 8]. Idemitsu has been developing new catalysts, which contain new Fe-treated Y-zeolites and which have further improved in a hydrocracking activity and in a selectivity to middle distillates. 

The addition of P into NiMo/Al203 catalyst increases hydrocracking activity. It indicates that P has also an indirect effect on Bronsted acidity. 

FIGURE 10.14 ZSM-5 catalytic dewaxing of waxy hydrocrackates activation energies versus percent non-normals. 

At high Si/Al ratios, removal of aluminum also results in a loss of cracking and hydrocracking activity for cumene. The disappearance of acid sites with decationization could account for loss of activity in both cracking and isomerization. 

Kinetics is the study of the rates of reaction. The rates of reaction determine the key properties of a hydrocracking catalyst initial activity, selectivity, stability and product quality. The temperature required to obtain the desired product at the start of the run measures the initial activity. In general, the catalyst activity is a measure of the relative rate of feedstock conversion. In hydrocracking, activity is defined as the temperature required obtaining fixed conversion under certain process conditions. Hydrocracking conversion is usually defined in terms of change of endpoint ... 

Fig. 4.25 Correlation between diphenylmethtuie hydrocracking activity and 2-propanol dehydration activity.

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