Isomerization

Isomerization, in itself, has become somewhat less desirable in recent years due to the mandate to increase ethanol in gasoline and the restrictive RVP specifications on finished gasoline with the isomerate share in the gasoline pool declining to about 3%. C₅-C₆ isomerization units increase octane by as much as 25 points, though octane is not as desirable as it used to be given declining gasoline demand around the world, and increase RVP, which is a major constraint particularly in the summer months. As a result of these factors, isomerization unit economics have suffered greatly and a number of units in the US and Europe have either been shut down completely or seen operating rates reduced greatly.

Refiners that are continuing to operate isomerization units are looking to increasingly saturate benzene in these units due to the more restrictive benzene limits being placed on gasoline around the globe. C₅-C₆ isomerization has become even more integral in helping refiners manage benzene in the gasoline pool given these tighter specifications.

Basically, four different types of isomerization process schemes are available for use. These include a once-through isomerization scheme, a once-through isomerization scheme with prefractionation, a scheme that recycles low-octane hexanes, and a scheme that combines recycle of low-octane hexanes with an upstream prefractionation step. Each scheme will give a different yield and octane number and refiners must choose a scheme based on specific product goals. These schemes can be used with either a zeolite or chlorided alumina catalyst. Refiners that are continuing to operate isomerization units are looking to increasingly saturate benzene in these units due to the more restrictive benzene limits being placed on gasoline around the globe. C₅-C₆ isomerization has become even more integral in helping refiners manage benzene in the gasoline pool given these tighter specifications.

Additionally, the isomerization section features the latest trends and technology offerings, including:

• Updated look at the global isomerate market including gasoline supply and demand fundamentals and what impact new regulations on benzene coupled with increased ethanol blending and the ongoing shale boom in North America will have on isomerization operations moving forward;
• I-84 light naphtha isomerization catalyst from UOP which is a version of the I-82 catalyst with lower Pt content;
• New PI-244 C₅-C₆ isomerization catalyst from UOP which is a lower Pt version of the PI-242 catalyst;
• Updated discussion on the ATIS 2L C₅-C₆ isomerization catalyst from Albemarle/Axens;
• New information on the HYSOPAR 5000 catalyst from Clariant;
• Commercial licensing examples of the Isomalk-2 process from GTC Technology/NPP Neftekhim;
• PRIS process from RRT Global that utilizes a reactive rectification column that contains a ZrO₂/SO₄ catalyst to reduce benzene;
• Updated look at the Penex Plus process from UOP for minimizing benzene;
• Adsorbents from Johnson Matthey (PURASPEC_JM) and UOP (GB-346S) for removing mercury from isomerization feeds;
• Improved moisture control for isomerization feeds;
• Adding a deisopentanizer to debottleneck existing isomerization capacity; and
• A discussion of the latest patent applications and research papers regarding isomerization technology including novel isomerization catalyst (e.g. borosilicates, sulfated zirconia, tungated zirconia, ionic liquids, and SAPO) compositions and preparation methods; improved isomerization reactor designs; isomerization fractionation techniques that replace molecular sieves with other equipment (e.g., membranes, strippers); integration of isomerization with other refining processes (e.g., catalytic reforming); and more.