Challenges for the periodic operation of trickle-bed catalytic reactors

Since the earliest publications just over a decade ago, the literature on periodic operation of trickle beds has grown rapidly. There are now over 30 published papers. Two applications, flow and feed composition modulation, for control of hot spots in large-scale reactors are sufficiently advanced for full-scale implementation if that has not already taken place. Models are now available that are capable of representing the time-average performance of periodically operated trickle beds, but these are not detailed enough to reproduce all of the transient behavior observed. Much about performance under periodic operation remains to be discovered. Research challenges are discussed under separate types of periodic operation: flow interruption, flow augmentation for hot spot control, feed composition modulation for hot spot control and to improve rate and/or to modify selectivity, and flow variation for enlargement of the pulse flow regime. (C) 2002 Published by Elsevier Science Ltd.