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Hydrogen-starved unit struggles to make ULSD

This is a 36 bar (525 psig) unit that was converted to ulsd service. The first two cycles used Albemarle KF-757 and lasted 6 months compared to one year expected cycle life. They switched to Topsoe catalyst for the next cycle and saw no improvement.

Two suppliers recommended replacing the reactor internals; but Johnson Matthey did a convincing analysis showing the unit was constrained by hydrogen supply, not flow distribution, and new internals would not fix the root cause of their short cycles.

The refinery passed on the flow distributor recommendations, and purchased Johnson Matthey’s JM-FHUDS ulsd catalyst for the next cycle. Initial temperature on the JM-FHUDS catalyst was the same as the previous cycle on Topsoe catalyst and (at the time of this story) the cycle was at 10 months with improved management of feed rate and feed composition to accommodate the hydrogen constraint.

P.S. this unit was subsequently shut down for low profitability, but the story shows a common theme -- which is the importance of understanding the root cause of short cycles before spending lots of money on expensive “fixes”.

This story was told during one of our semi-annual “War-stories lunches”, during which Hoekstra Trading clients share real-life stories of catalyst successes and failures in commercial unit.

Other Literature

Hoekstra war stories

In the past two years, there have been many field failures in ultra-low sulfur diesel (ulsd) hydrotreaters. By field failures we mean short cycles of less than half the expected cycle life. The root cause of these failures was overestimating what a catalyst can do in a hydrogen starved unit.


Cycle life estimates for catalyst reload vary from 7 to 44 months

It is very difficult to accurately predict the cycle life for a hydroprocessing unit. This is especially true with today’s highly variable feed slates. Despite this fact, catalyst suppliers are always asked to estimate cycle life when bidding for a catalyst reload, and they comply with the request ...


High aromatic/nitrogen feeds cause rapid initial deactivation in pilot plants

A feed sent to C Solutions in Thessaloniki, Greece caused catalyst to deactivate very rapidly when introduced on day one of a pilot plant run.  Analysis showed the feed to be full of high boiling aromatics and high in nitrogen. The pilot plant run was restarted with the usual 3-day break-in ...


Hydrogen-starved unit struggles to make ULSD

This is a 36 bar (525 psig) unit that was converted to ulsd service. The first two cycles used Albemarle KF-757 and lasted 6 months compared to one year expected cycle life. They switched to Topsoe catalyst for the next cycle and saw no improvement.

Two suppliers recommended replacing ...


Refinery weighs proposals for 10 ppm diesel

This refinery wanted to make 10 ppm diesel in blocked out commercial trials as preparation for upcoming diesel specifications. Some catalyst vendors said the refinery would need to double the reactor volume to make 10ppm. Other vendors said they had a new drop-in solution, a catalyst that will do the ...


Sulfur speciation analysis helps with feedstock management

Cycle life for successive runs on this diesel hydrotreater has varied from 6 to 18 months.The cycle history was analyzed to assess the difficulty of processing varying feeds. Sulfur speciation analysis enabled measurement of difficult sulfur in the feed components. The unit’s cycle life was found ...