Management of Platinum in Catalytic Reforming Systems
Oil and Gas Journal, August 2015
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What are the sources of platinum loss in precious-metals catalysts? What role can your refinery engineers play in minimizing this loss?
MITZNER: Platinum loss results primarily from catalyst losses and poor bookkeeping practices. Actual loss of platinum from the catalyst is less likely and limited to extreme regeneration conditions.
Many years will pass and several unit engineers will rotate through during the lifetime of a reforming catalyst. Having a well-thought-out and executed protocol for handling the catalyst, accounting for its whereabouts, and accurately knowing its mass and platinum content at all times during its lifecycle will enable more accurate closure on the platinum balance post-reclamation.
Catalyst losses primarily occur during handling. Unrecovered spillage often occurs during transportation, reactor loading and unloading, screening operations, etc. Occasionally, spent or fresh catalyst is inadvertently disposed of from the warehouse or at the unit, particularly if drums are not clearly labeled. Catalyst that is never loaded and left in storage can be overlooked even though it remains onsite. Catalyst bookkeeping is complicated by intermittent skimming of catalyst, dump and screens, reloading, and transferring catalyst from one reactor or unit to another.
On oil, catalyst losses result from lost containment either as whole pieces, fragments, or dust. Sometimes this material is lost to the liquid product and winds up distributed throughout the unit and downstream equipment all the way to product storage. This contamination only occurs when there is a mechanical failure that allows catalyst loss from the reactor or circulation system.
Inaccurate bookkeeping will often account for a fair portion of the platinum loss. The alumina used to make reforming catalyst is very hygroscopic. In little time, its weight can change by several percent if it is left exposed to humid air. Contaminants accumulated during the catalyst’s lifetime, as well as coke and adsorbed hydrocarbons remaining on the catalyst being sent for reclamation, can also affect its weight. Accurate determination of the loss on ignition (LOI) is critical to accurate bookkeeping. The accurate determination of the platinum content of both the fresh and spent catalyst is also extremely critical.
Samples collected for assay must accurately represent the material from which they are taken. Disproportionate inclusion of inerts, scale, etc. in these samples will impact the accuracy of the platinum assay. Comingling catalysts that are different in size, shape, or platinum content increases the probability of non-representative assay results. Formation of alpha alumina, as a result of severe temperature excursion during regeneration, will encapsulate some of the platinum and render it unrecoverable.
VICE: Catalyst losses occur through the sampling process, fine generation, and continuous catalyst regeneration (CCR) while circulating the catalyst, or as a result of mechanical issues with fixed-bed support systems and during the catalyst change-out process. Relative to the sampling process, it is critical for the lab to have procedures in place to capture all of the catalysts for reclamation. Relative to the CCR engineers, they should be watching catalyst-fines generation on a routine basis, as well as the catalyst makeup. It is really critical to determine if you have a problem earlier to minimize your losses.
During the change-out process, the management of the platinum catalyst is everyone’s responsibility, so that goes from the catalyst-handling company to operations and your tech-service personnel. In our system, the engineer would be tracking the catalyst from the moment it arrives in the warehouse until it goes in the unit and is then loaded in the reactor. The same is true about the spent catalyst when it is removed from the reactor to the storage area and then eventually sent out for reclamation.
As highlighted before, housekeeping is really critical during the loading and unloading processes. All spillage needs to be picked up and captured for reclamation. Any catalyst remaining in the reactor needs to be vacuumed up as well.
HUDE: I want to add that you can see losses in catalyst manufacturing. Engineers need to be aware of that if they are paying a first catalyst surcharge for platinum or a surcharge on the reclaim. We have seen losses in this area up to 1%. Also on the CCR, if you do not have a dust collector on Reactor 1, you will be losing platinum from that dust which is going into your reformate tank. So an engineer should work with maintenance to consider any recovery options when you are cleaning a reformate tank.
KAMINSKY: I just want to elucidate a bit about the chemistry going on with the platinum loss from my perspective as a catalyst chemist. There is a volatile phase of platinum, platinum oxide (PtO2), that forms under hot, oxidizing conditions such as in your regenerator. So it is not just fines but actual volatilization of Pt as PtO2, which causes movement of Pt from the catalyst in the regenerator.
This situation has been documented previously in automobile catalytic converters. Ford and GM have published papers on Pt volatility. Such volatility causes Pt to move out of the oxidation catalytic converter (that oxidizes CO to CO2), but then the PtO2 adsorbs onto the downstream selective catalytic reduction (SCR) catalyst and permanently poisons it.
It is a big problem for car manufacturers. They are solving it by alloying the platinum with palladium or other metals to reduce the propensity for platinum to form the superoxide. Maybe such a solution would help reduce Pt loss in FCC units also.
SMALL: Typical operating conditions in a reformer do not result in volatile platinum. However, it is possible for platinum to become volatile and come off the catalyst at very high temperatures. One place this can occur is in the chlorination zone of the CCR regeneration tower where slipping coked catalyst into an oxygen-rich atmosphere can result in very high temperatures. To prevent this, the refiner should make sure that the regeneration tower is operated according to design.
In UOP’s experience, these questions often arise as the result of an assay difference with the reclaimer rather than with volatilizing platinum. The assay differences can be due to unrepresentative sampling or poor or biased analyses.
OYEKAN: In order to fully answer the questions, it is relevant to separate the precious metal catalyst platinum management into five distinct stages to cover a platinum catalyst manufacture to spent-catalyst platinum reclamation lifecycle. The stages that are pertinent for our review are:
• Reforming catalyst manufacture by the catalyst supplier and platinum settlement.
• Reforming catalyst storage and catalyst loading.
• Catalyst as used in the reforming units.
• Catalyst dumping and transfer to platinum reclamation company.
• Platinum settlement with the platinum-reclamation company.
It must be clearly understood that platinum losses can occur at any of the stages of the catalyst cycle. Some of the losses are due to contractual agreements as agreed upon in the first and fifth stages as a consequence of platinum settlement. The platinum or precious-metals manager for an oil refining company should have the necessary expertise to aid in minimization of platinum losses for the oil refiner for the first and fifth stages.
In the fresh-catalyst manufacture stage, the agreement with the catalyst- manufacturing company for platinum settlement could stipulate 98-99.5% platinum return for the settlements. The platinum settlement requires that the oil refiner and catalyst manufacturer or platinum reclamation companies for the platinum settlement have appropriate analytical data (platinum assay, LOI for solid content) to permit effective conducting of the platinum settlement.
Some oil refiners conduct platinum settlement with the catalyst suppliers, and some do not. I recommend conducting fresh-catalyst platinum settlements to establish a reference for initial platinum in use in a specific process unit that would be utilizing the fresh- catalyst load, and that the nominal platinum concentrations not be relied on as indicative of the reference fresh- catalyst platinum.
In the years I managed precious metals for two oil refiners as a refinery technologist, several excess platinum troy ounces were returned to my companies’ platinum-pool accounts after fresh-catalyst platinum settlements with the catalyst manufacturers. In addition, the fresh-catalyst platinum settlement data provided a good reference basis for the subsequent platinum inventory in the reactors after the catalyst loading.
In the spent-catalyst platinum reclamation, a similar legal agreement could stipulate another 98-99% platinum settlement, with some additional platinum-percent penalties for coke, catalyst alumina state (alpha or delta), and metals impurities. Thus, based on the two platinum settlements for fresh and spent catalyst for a catalyst lifecycle, platinum losses due to contractual agreements and lack of the appropriate level of platinum management expertise by the oil refiner could lead to platinum losses in the range of 3-5 wt% for the oil refiner.
Major additional losses could occur in Stages 2-4. These combined areas of catalyst loading, in-unit catalyst usage, catalyst dumping, and precious metals management are so intertwined and extensive that I strongly recommend securing the services of experienced technical experts who understand clearly the three major catalytic reforming technologies-semi-regeneration, cyclic, and continuous catalytic regeneration reformers-and how their operations could greatly contribute to significant platinum losses.
If you also own paraffin isomerization units and other process units that use platinum catalysts, seek the assistance of a technical expert who fully understands platinum or precious metals management, as well as the operations of the relevant oil refining process units that utilize platinum catalysts.
An excellent oil refining expert could also work with your engineers and other relevant oil refinery personal on proactive steps for cost-efficient catalyst management, process monitoring, and optimization and equipment management to minimize platinum losses.
John Ahern, gasoline and catalyst specialist, Phillips 66
Jeff Hude, process engineering manager, Valero Energy Corp.
Michael Mitzner, senior regional sales manager, Axens North America
Shane Presley, technical service leader, DuPont Clean Technologies
Rick Vice, alkylation and Merox technologist, Marathon Petroleum Corp.
Christopher Gilmore, Irving Oil Ltd.
Geoff Dubin, Axens North America
Mark Kaminsky, Aramco Services Co.
Troy Small, UOP LLC
Ka Lok, UOP LLC
Soni Oyekan, Prafis Energy Solutions