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Diesel dewaxing catalysts

Maximising middle distillate yields while maintaining excellent cold flow properties. In recent years, diesel dewaxing has emerged as a powerful
technique for meeting product specifications and creating additional margin.

To avoid wax compounds crystallising out and causing engine problems, the cold flow properties of diesel fuels that are to be marketed in cold climates must meet stringent specifications. Dewaxing can be used to remove the wax for meeting the required values for cloud point, pour point and cold filter plugging point, and this can be often a better economic option than the alternative techniques, which include additivation and kerosene blending.

Criterion Catalysts & Technologies (Criterion), along with its affiliate the technology licensor Shell Global Solutions, has established an enviable track record of working with customers to design and implement value-adding dewaxing projects that meet their objectives.

Criterion recommends two main process configurations for catalytic dewaxing, and offers a dewaxing catalyst for each (Figure 1). These configurations are:
• single-stage  dewaxing. The dewaxing bed is part of the main hydrotreating section, and a base metal dewaxing catalyst (SDD-800) is used that can withstand the severe operating conditions that are encountered. This configuration can provide a low-cost and flexible solution.

• 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 (SDD-821) can be used. Investment costs may be higher with this configuration, but product qualities and yields can be maximised.

Catalytic dewaxing has helped refiners around the world to unlock substantial value by helping them to:
• maximise the yield of high-value distillates. The addition of kerosene to the diesel oil pool is a common solution for meeting cold flow specifications; however, that detracts from the bottom line.

• enhance margins. Diesel dewaxing avoids the need for expensive additives. In addition, it can facilitate the use of cheaper feedstocks that have a higher cloud or pour point, or more wax.

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