Deactivation hydrocracking

Hydrogenation Function of Fresh and Deactivated Hydrocracking Catalysts Cyclohexene Hydrogenation... 

Figure 10-27 Temperature-time trajectories for deactivating hydrocracking catalyst, runs 3 and 4. [Reprinted with permission from S. Knshnaswamy and S. R. Kittrell, Ind. Eng. Chern. Process Des. Dev., 18,399 (1979)..Copyright 1979 American Chemical Society.]...

Bifunctional catalysis is one of the most important routes to green (more economical and more environmentally friendly) processes. Indeed, the deactivation of bifunctional catalysts by coking is much slower than that of monofunctional catalysts and their selectivity generally higher (e.g., hydrocracking compared to... 

Other reactions may also occur. These include carbon formation, hydrocracking or thermal cracking, dehydrocyclization of paraffins to naphthenes, and dehydrogenation of naphthenes to aromatics. These have been discussed in the deactivation of reforming catalysts, in Section 2. 

A systematic study of the history of the hydrogenation function ip a series of fresh and deactivated commercial hydrocracking catalysts is reported using cyclohexene hydrogenation as a probe reaction. 

The catalysts were hydrocracking catalysts, both fresh and deactivated up to periods of two years. Hydrogenation activity is shown to be related to sulfur content, while ESR studies indicate a correlation between activity and in the catalyst. 

J.Coreila,A-Monzon,J.B.ButlrR.PlAt)S4l The modelling of the Kinetics of Deactivation of a Commercial Hydrocracking Catalyst in ihe Reaction of Cumene Disproportionation J.CatalysJs 100(1986)149... 

The deactivation of catalysts, especially zeolites, during cracking, hydrocracking, methanol conversion, etc, is one of the major technological and economic problems of the chemical industry (1). The interest of these materials lies not only in their high catalytic activity and selectivity but also in the possibility of regenerating them several times so that their Lifetime" is compatible with the cost of their production. Consequently, it is necessary to understand the manner and the rate of catalyst deactivation as well as the nature of the carbonaceous residues formed, commonly called coke". 

The S-shape deactivation pattern in Figure 10 is determined by the process of metal deposition in the outer core of the catalyst particles desulfurization and hydrocracking occur mainly in the inner core of the catalyst particle (27). This understanding led to development of various effective demetallation catalysts as shown in Figure 11 (22,23,24,25). Furthermore, this has opened the path to industrial solutions (26) for the treatment of high metal feedstocks. 

This article is a brief review of the state of the art in the use of Nuclear Magnetic Resonance for studpng deactivation of zeolite based catalysts which occurs during cracking, hydrocracking, reforming and isomerization reactions. 

Figure 5 shows that coke deactivates a HDN activity more than a HG activity. If acidic sites favor hydrogenolysis of a C-N bond like a hydrocracking reaction, loss of the acidic sites of an alumina support by coke deposition will decrease the HDN activity. Therefore, this result may support preferential deposition of coke on an alumina support. 

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