Top Ten Ways to Improve Catalyst Performance
By George Swan, Ph.D.
In-service catalyst deactivation is unavoidable, and poisoning incidents
compound the problem. The goal in catalytic processing is to minimize
catalyst cost in ¢/bbl of feed while achieving process targets
(conversion, selectivity, etc.) over the useful life of the catalyst. Thus
catalyst “management” is key to maximizing unit profitability.
Following are generalized action steps to more effectively manage
catalysts for fixed bed, moving bed, and fluidized bed commercial
Choosing the best catalyst formulation for a specific application assures
that factors such as expected feed characteristics and process conditions
are properly considered. Is the catalyst “fit for purpose?” Soliciting
proposals from catalyst vendors is a good way to start the selection
process. In some situations a pilot plant study comparing candidate
catalysts may be warranted and is a valuable investment.
Does the delivered catalyst meet all physical and chemical properties
specified? Laboratory analysis of the fresh catalyst can reveal potential
problems, e.g., higher abrasion which could lead to excessive fines
formation during loading and operation. Subtle deviations from
specifications like pore size distribution can dramatically affect
Are dense loading vs. sock loading taken into consideration to assure
fixed bed homogeneity and minimize pressure drop? Does FCC fresh catalyst
loader/e-cat withdrawal operate with precision?
Critical steps such as reduction and pre-sulfiding should be carefully
monitored to avoid such pitfalls as noble metal sintering. Systematic
development and implementation of detailed procedures for catalyst
activation pay big dividends in capturing their full potential.
Oil-in for fixed bed operations can be challenging, especially when
deviations from normal procedures are required to address unanticipated
events. Team review of start-up procedures prior to oil-in is a good
practice. Formulating back-up plans addressing “what ifs” are useful to
minimize catalyst damage, e.g., from localized exotherms.
- Feed Contaminant Monitoring
Regular feedstock analysis is critically important to identify higher than
normal concentrations of basic nitrogen compounds or heavy metals
introduced from imported feeds or possibly addition of refinery “slop
streams.” These and other poisons can quickly impair catalyst activity. An
aggressive feed sampling and analysis program, ideally before planned feed
changes to the process are made, is a good investment of time and money.
- Process Monitoring/Upset Mitigation
Continuously tracking indicators such as bed temperature profiles can
reveal a decline in catalyst selectivity. Likewise, when process upsets
occur swift corrective actions to protect the catalyst can prolong its
- Regular Catalyst Sampling/Analysis
Frequent monitoring of catalyst properties provides information useful for
taking remedial steps where possible and for planning changeouts. This
information is routine in fluidized bed operations such as FCC, where
e-cat analysis and MAT testing is normal. Sampling fixed bed units is
typically non-routine, but equally useful to characterize catalyst
condition and suggest changes such as bed skimming to enhance unit
performance. Online fixed bed catalyst sampler designs have been
successfully implemented in a number of applications.
Whether in fixed or fluid bed operations, regeneration plays a crucial
role in both the life and performance of the catalyst. Fixed bed or moving
bed catalyst regen procedures can be adjusted to compensate for some
prevalent shortfalls, for example by redispersing partially agglomerated
noble metals. Furthermore, ex-situ regeneration of fixed bed catalysts is
another option which can facilitate better control of conditions and
enhanced recovery of activity. Judicious monitoring when torch oil is
added to FCC regenerators is important to minimize loss of catalyst
surface area due to localized high temperatures at the nozzles. Also
adjusting other variables in FCC regenerators such as bed level can reduce
- Replacement/Change-out Strategy
Ultimately catalysts deactivate to a point where replacement is the only
feasible option. Quite often these decisions are deferred to the point
that overall process capability is significantly reduced and economics are
negatively impacted. Developing a longer range plan for replacing
catalysts offers an opportunity to reevaluate their formulation (selection
process), as well as recapturing the initial performance realized if a
replacement in kind is chosen. Learnings captured during a particular
catalyst’s life cycle are extremely valuable in guiding future decisions.