Regeneration of Fixed-Bed Catalytic Reactors Deactivated by Coke:  Influence of Operating Conditions and of Different Pretreatments of the Coke Deposits

Abstract

The regeneration of coked fixed-bed catalytic reactors has been studied experimentally. Different types of coke distribution have been artificially created in order to study their influence upon the temperatures reached during regeneration. The effect of the oxygen concentration in the reactor feed and the total gas feedrate have also been studied. In addition, a study has been carried out of different coke pretreatments with the aim of eliminating part of the hydrogen-rich coke fractions prior to regeneration, thereby reducing temperature increases during the subsequent regeneration process. A new parameter, the Thermal Aging Index, has been proposed, as a means to quantify the impact that different regeneration procedures may have on a catalyst.

Regeneration of catalysts deactivated by coke deposition: A review

“…Steam, sometimes nitrogen, is used as a diluent in industrial-scale plants [2]. Moreover, a two-stage regeneration system has been developed and is used in FCC units [55][56][57], because hydrogen-rich fractions of coke significantly contribute to heat production and react easily with O2. The first stage operates at a temperature just enough to remove these hydrogen-rich coke.…”

Role of Coke Characteristics in the Regeneration of a Catalyst for the MTG Process

“…Coke instability affects combustion kinetics reproducibility, which is a serious problem for obtaining valid kinetic parameters, and, even more serious, it makes combustion control in the reactor difficult. Royo et al (1994Royo et al ( , 1996 have studied the effect of the H/C ratio of the coke on the regeneration of a Cr 2 O 3 /Al 2 O 3 catalyst in an adiabatic fixed bed. By virtue of this effect, coke aging prior to combustion is needed.…”

Analysis and Model-Based Description of the Total Process of Periodic Deactivation and Regeneration of a VOx Catalyst for Selective Dehydrogenation of Propane

“…This can lead to difficulties in describing reliably coke burning kinetics. Differences in the behavior of the coke during regeneration can occur after different pretreatments but can also be observed in different parts of the reactor [38,41]. The aim of this section is to develop a simplified kinetic model of the complex coke burning kinetics and to check whether these difficulties occur in the considered reaction system.…”

“…This can lead to difficulties in describing reliably coke burning kinetics. Differences in the behavior of the coke during regeneration can occur after different pretreatments but can also be observed in different parts of the reactor[38,41]. The aim of…”