Reconsidering the business case for catalytic dewaxing (ERTC)

Most refineries try to optimise their product mix to satisfy market demand for ultra-low sulphur diesel (ULSD) with good cold flow properties during cold winter periods. The difficulty, of course, lies in deciding on the most profitable dewaxing solution.

Per Zeuthen
Haldor Topsoe A/S

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Article Summary

Refinery engineers the world over have heard about catalytic dewaxing – the chemistry is well known for making sure oil products like diesel are liquid at specific temperature ranges. But few refineries have found a way to implement catalytic dewaxing technology effectively in diesel production setups without substantial capex.

Yes, some catalysts are good for improving cold flow properties, but conventional dewaxing catalysts have a major weakness: a revenue-denting poor yield. They also reduce cycle length since they take up space that could otherwise be used for the bulk catalyst, and they are costly, which is never a good thing. So most refineries use some form of 
undercutting, additives, diluting with kerosene, or a combination of these.
Balancing your options: the wider picture

‘Would it make commercial sense?’ considerations are rarely limited to the pros and cons of one particular process. There are knock-on effects and opportunity costs throughout, both positive and negative.

If you are undercutting the feedstock, what should you do with the heavy part that is cut away? Pass it to the VGO fraction? Use it as heating oil? Send it to the FCC unit?

If you are diluting with kerosene, how does that affect your overall product portfolio? Could you have benefitted more from using this kerosene fraction to produce jet fuel, now a growth market worldwide?

Using additives is usually expensive and often involves feedstock limitations, as the effectiveness of additives is highly dependent on product distillation, so sometimes it is necessary to also undercut the feed and/or dilute with kerosene.

There are several conventional cracking dewaxing catalysts available commercially. They do the job, but they also replace part of the main hydrotreating catalyst and result in high yield loss that ruins profit outlooks. Are good cold flow properties your only target? Or do you also need some end-point reduction or additional volume swell? These are just some of the many parameters that need weighing up.

Catalytic dewaxing: considered but often rejected
Refineries consider the ‘business case’ carefully before deciding. Conventional catalytic dewaxing usually gets the thumbs down as a tool for cold flow compliance for two main reasons:
• The catalyst involves cracking, resulting in high yield loss
• The isomerisation catalyst with good yields often involves noble metals, which is costly and often requires some capex in order to be implemented.

Topsoe isomerisation innovation
The recent emergence of a new series of catalyst products from Topsoe has opened up fresh commercial opportunities by bringing effective, reliable catalytic isomerisation dewaxing capabilities into ULSD production, with a solution that does not utilise noble metals. Isomerisation changes long-chain n-paraffins into same-length iso-paraffins, improving cold flow properties significantly and only shifting the boiling point slightly. This keeps carbon atoms in the diesel fraction and ensures minimal yield loss.

The introduction of isomerisation-specific TK-930 D-wax™ eradicates the previous perceived weaknesses of catalytic dewaxing in diesel production. The known strengths are brought centre stage, and the payoffs are lined up in a non-capex drop-in catalyst solution that is ideal for improving cold flow properties in most existing hydrotreating units. It can be phased in seamlessly to provide better quality outputs and more revenue using existing equipment, with no technology licensing requirements to limit the refiner’s technical choices or decision-making independence. The cold flow ‘business case’ discussion has now changed.

Did you know TK-930 D-wax removes the previous perceived weaknesses of catalytic dewaxing in diesel production?

This short article originally appeared in the 2018 ERTC Newspaper, produced by PTQ / DigitalRefining.

For more information contact: pz@topsoe.com

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