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C5-C6 fractions isomerization Isomalk-2

Pentane-hexane fractions isomerization technology Isomalk-2 is a unique Russian development in the sphere of light naphtha isomerization based on unique low-temperature isomerization catalyst SI-2 developed in SIE Neftehim, LLC.

SI-2 catalyst has been used in industry since 2003 and has great isomerization ability, tolerance to the action of catalytic poisons, withstands 8-10 regenerations without loss of activity, resistant to feed space velocity fluctuations and breakthroughs of water in feed. SI-2 catalyst restores its activity upon short-term breakthroughs of water up to 100 ppm and sulfur up to 5 ppm.



High activity and tolerance to process mode upsets as well as catalytic poisons breakthroughs allow using the catalyst for a long time without regeneration. The maximum service life of SI-2 catalyst without regeneration was achieved at KINEF, LLC unit and it was 13 years.

Currently, Isomalk-2 isomerization technology and SI-2 catalyst are being used at 15 commercial units in Russia, Ukraine, Romania, India, China, and the Middle East. In addition, design and construction of another 12 units in Russia, the PRC and Portugal are in progress.

 Isomerization Technology

SI-2 catalyst is manufactured according to TU (Technical Specifications) 2177-009-04706192-00 revision No. 8 at own production site in Nizhny Novgorod. The catalyst is supplied only by SIE Neftehim, LLC.


Concerning the basic specifications of SI-2 catalyst, Isomalk-2 technology involves pre-treatment of feed, but unlike chlorinated catalysts, it does not require special adsorptive treatment of hydrogenate to remove sulfur, nitrogen, and water micro impurities. Necessary requirements of micro impurities contents are met by simple hydrotreatment and stripping of unstable hydrogenate. Reactor section of Isomalk-2 involves one or two reactors with effluent stream intercooling.

Unit process flow diagram depends on feed composition. Isomalk-2 technology allows processing pentane-hexane fractions, containing considerable amounts of benzene (up to 5-8%) and C7 hydrocarbons – up to 10%, using special technical solutions.

Specific features of isomerization catalyst SI-2 are the following:

  • Isomerization activity of SI-2 catalyst is much higher than that of zeolite catalysts and as good as that of chlorinated catalysts;
  • SI-2 catalyst is tolerant to catalytic poisons action, restores its activity even after short-time water breakthroughs up to 100 ppm and sulfur breakthroughs up to 5 ppm;
  • Supply of acid reactants is not required and thus there is no off-gas alkalization section;
  • High yield of commercial isomerate – 97-99%;
  • SI-2 catalyst service life is 10 years, service cycle is 5-6 years;
  • Isocomponent octane number achieved according to Isomalk-2 technology is from 81 to 92 RON and depends mostly on the chosen PFD option.

 Comparative table of process flow diagram (PFD) options

Isomerization Technology

Isomalk-2 technology and SI-2 catalyst commercial use experience:



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