Hydrodesulfurization profiles

Some studies of potential commercial significance have been made. For instance, deposition of catalyst some distance away from the pore mouth extends the catalyst s life when pore mouth deactivation occurs. Oxidation of CO in automobile exhausts is sensitive to the catalyst profile. For oxidation of propane the activity is eggshell > uniform > egg white. Nonuniform distributions have been found superior for hydrodemetallation of petroleum and hydrodesulfurization with molybdenum and cobalt sulfides. Whether any commercial processes with programmed pore distribution of catalysts are actually in use is not mentioned in the recent extensive review of Gavrillidis et al. (in Becker and Pereira, eds., Computer-Aided Design of Catalysts, Dekker, 1993, pp. 137-198), with the exception of monolithic automobile exhaust cleanup where the catalyst may be deposited some distance from the mouth of the pore and where perhaps a 25-percent longer life thereby may be attained. 

Figure 1 Axial profiles of sulfur removal and hydrogen sulfide concentration in the gas for hydrodesulfurization of oil following second-order kinetics in total sulfur.

Feed properties and operation conditions determine catalyst life in the residue hydrodesulfurization. In a high conversion operation of vacuum residue, catalyst deactivation due to coke is as important as the one due to metals. Though many researchers have worked on understanding and modelling deactivation of residue hydrodesulfurization catalysts, there has still been a controversy in a coke deactivation mechanism [2, 3]. Very few publications are available discussing an effect of a bed temperature profile on catalyst deactivation in large scale adiabatic commercial reactors. Most of the studies on deactivation of residue hydrodesulfiirization catalysts have been done with small-scale isothermal reactors [2,3,4,5]. The activity tests of the used catalysts were conducted to study the catalyst deactivation in the commercial reactors. This paper also describes an effect of a bed temperature profile on coke deactivation, which was tested in the commercial reactors. 

Vakros J, Papadopouloua C, Lycourghiotisa A, Kordulisa C (2011) Hydrodesulfurization catalyst bodies with various Co and Mo profiles. Appl Catal Gen 399 211-220... 

This chapter deals with the noncatalytic hydrodesulfurization (NHDS), hydrodemet-allization (NHDM), and hydrocracking (NHDC) of heavy crude oil and atmospheric residue. Some experiments were carried out in two different bench-scale units equipped with fixed-bed reactors in series operated in adiabatic and isothermal modes. The reactors were loaded with inert material (silicon carbide). Different feedstocks were used for the tests 13°API heavy crude oil, 21°API crude oil, atmospheric residue from the 13°API heavy crude oil, and atmospheric residue from the 21°API crude oil. The effects of pressure, residence time, temperature, and type of feed on noncatalytic reactions and axial reactor temperature profiles are examined. Reaction kinetics of the different noncatalytic reactions is studied by following the power-law approach. 

Based on Laxminarasimhan s work, Korasheh et al. (2001,2005) and Ashuri et al. (2007) have extended the application of the continuous lumping to model hydrocracking, hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) in order to predict the dependence of parameters with temperature. Basak et al. (2004) have modeled the hydrogen consumption and the bed temperature profile in an industrial... 

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