Catalytic dewaxing

Over 90 refineries worldwide apply or have applied catalytic dewaxing to improve the cold flow properties of their diesel and lubricating oils, and Shell Global Solutions believes that many other refiners could enhance their margins by using this technique.

Catalytic dewaxing prevents wax compounds from crystallising out in diesel and causing engine problems, thereby helping refiners to achieve the cold flow properties necessary for diesel to be marketed in cold climates. Laurent Huve, Dewaxing and Base Oil Technology Manager, Shell Global Solutions, says that catalytic dewaxing can often be a better economic option than the
alternatives, which include additivation and kerosene blending, although it depends on what the cold flow constraint actually is.

He explains, “To ensure that the various products have the required lowtemperature flow properties, three main cold flow property specifications are used: the cloud, pour and cold filter plugging points. If the constraining factor is the cloud point, catalytic dewaxing will often prove to be the most economic option, especially if an improvement of more than 6–7°C is required. If the constraint is pour point or cold filter plugging point, an economic evaluation of the other options may be necessary.

There is no definitive answer, as it also depends on local factors such as the price of naphtha, gasoline, kerosene and so on.”

Shell Global Solutions, in association with Criterion Catalysts & Technologies, has established an enviable track record of working with customers to design and implement value-adding catalytic dewaxing projects that meet their objectives.

There are two main process configurations for catalytic dewaxing. In single-stage dewaxing, the dewaxing bed is part of the main hydrotreating section, and a base metal dewaxing catalyst that can withstand the severe operating conditions is used. This configuration can provide a low-cost and flexible solution.

With second-stage dewaxing, a dedicated second-stage reactor downstream of the hydrotreating reactor provides a cleaner environment (low sulphur and nitrogen) so that a high-activity noble metal catalyst can be used. The investment costs may be higher with this configuration, but product qualities and yields can be maximised. Huve insists that, for the best results, catalytic dewaxing projects must follow a collaborative approach that leverages the refiner’s site-specific knowledge and marketplace perspectives with the global operational and technical expertise of the licensor and catalyst supplier.

“Catalytic dewaxing may not be the most economic option for all refiners,” says Huve, “so they should carefully evaluate the benefits against other cold flow improvement techniques. But it has helped refiners around the world to unlock substantial value. It has helped some to increase their yield of high-value distillates, while others have reported enhancing their margins through a reduced need for expensive additives. It can also facilitate the use of cheaper feedstocks that have a higher cloud or pour point, or more wax.”

“That is why,” he concludes, “catalytic dewaxing is emerging as a powerful technique for meeting product specifications and creating additional margin. Potentially, it is a very valuable opportunity for many refiners.”

For more information contact Laurent Huve.