Hydrocracking catalysts deactivation

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

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". 

Accelerated deactivation tests in hydrocracking have been reported (38), where a constant conversion mode was run at much higher space velocity (and hence temperature) than under actual operation conditions. Differences in deactivation were measured that were later substantiated in commercial operation (38). Although all these approaches aim at accelerating the catalyst deactivation reaction in Equation 7, such tests should obviously not be applied to catalyst systems that — at the high space velocity — operate at such high temperatures that very high polyaromatics concentrations prevail. 

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.]...

Platinum (metal)- and acid (oxide)-catalyzed processes were developed to convert petroleum to high-octane fuels. Hydrodesulfurization catalysis removed sulfur from the crude to prevent catalyst deactivation. The discovery of microporous crystalline alumina silicates (zeolites) provided more selective and active catalysts for many reactions, including cracking, hydrocracking, alkylation, isomerization, and oligomerization. Catalysts that polymerize ethylene, propylene, and other molecules were discovered. A new generation of bimetallic catalysts that were dispersed on high-surface-area (100-400 m /g) oxides was synthesized. 

The catalyst deactivation time in hydrocracking is on the order of a few years versus several seconds for FCC catalysts, due primarily to the presence of the transition metal and that the reactor is operated at elevated pressures in the presence of hydrogen. 

Fig 16. Deactivation of amorphous and zeolite base hydrocracking catalyst... 

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