A world of opportunities

Isomerisation remains the main technology driver for upgrading light hydrocarbons, as demand for gasoline and petrochemicals, both in terms of quality and quantity, have experienced steady growth in most regions of the world.

C₄ isomerisation technology prepares feedstock for the alkylation process, producing gasoline pool blending stock. C₅ - C₆ light naphtha isomerisation technology plays a key role in meeting octane demand in the gasoline pool for cleaner fuels and premium gasoline grades.

The isomerisation process involves the skeletal arrangement of a straight chain paraffin to a more highly branched paraffin with the same carbon number. The isomerisation reaction is initiated by an acid function promoted catalyst. Apart from production of higher-octane isomers, the isomerisation process is also one of the simplest and most economical ways to manage benzene constraint in the gasoline pool, as all types of isomerisation catalyst perform the benzene saturation in the first place.

Several paraffin isomerisation technologies are available on the market today, along with a wide variety of catalyst technologies. Catalyst formulation may be based with zeolite, mixed-metal oxide (zirconia), and chlorinated-alumina. All types of catalyst contain platinum. Deep feed pre-treatment to remove sulfur, nitrogen and oxygenates is necessary for all types of catalyst to ensure efficient performance. Therefore, the isomerate produced through the isomerisation process is a sulfur-free blending component that helps to meet the lower sulfur specification of gasoline pool.

Over the past years, there has been a steady evolution in both the flow scheme and catalysts used in the light naphtha isomerisation processes. Depending on isomerate research octane number (RON) target, flow scheme enhancements including the addition of super-fractionators such as deisopentanisers (DIP), deisohexanisers (DIH), or the use of a molecular sieve, help to separate iso and normal paraffin. All of these measures help to recycle the unconverted paraffin back to the reaction section for further conversion.

Catalyst advancements include the use of new materials and base formulations to increase activity, selectivity, and the life of catalysts.

Irrespective of flow scheme improvements to meet isomerate RON target, the choice of catalyst also has an important influence on process scheme configuration. Depending on the catalyst selected for the isomerisation process, the key operating parameters and facilities needed for feed contaminants management can vary.

This article was originally published in the November 2023 issue of Hydrocarbon Engineering magazine. To read the full article, sign in or register for a free subscription.

Written by Gabriel Buffin, Bijay Barik and Laurent Watripont, Axens.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/13112023/a-world-of-opportunities/