What are the more attractive isomerisation configurations and catalysts available to meet the growing demand for light paraffin isomerisation? What can be done to lower the equipment cost, such as the recycle hydrogen compressor?
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07/09/2007
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Amarjit Bakshi, Refining Hydrocarbon Technologies LLC, abakshi@rhtgulfcoast.com
There are few options in isomerization flowscheme/configuration at present. As the effluent from reactor will be in equilibrium in normal and branched C5 and C6 hydrocarbons/paraffins, it is expected that recycle of unconverted normal species after separation from the isomerate to the reactor will enhance the octane. The isomerate from once through or recycle configuration could have 8 to 10 point difference. Additionally, chlorinated alumina catalyst provides better equilibrium as reaction temperature is lower than for the Pt/zeolite catalyst. Naturally to enhance the conversions recycle option is best and to gain the octane advantage one will require rcycle option.
There are other advancements in this technology based on thermodynamics and have not been exploited yet and RHT LLC is filing patents to exploite the advance configuration/design options.
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23/07/2007
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Margaret Stine, UOP, margaret.stine@uop.com
The UOP Penex process and the Par-Isom process are the most common processes chosen to meet the worldwide needs for light paraffin isomerisataion. Penex uses the aluminum chlorided catalysts, I-8 Plus and I-82. The UOP catalysts process all feedstocks, including those with high C7 hydrocarbons or benzene content. Penex is frequently coupled with deisopentaising and/or deisohexanising to reach high isomerate product octane. The process is very efficient and does not require a recycle compressor.
Par-Isom has been widely accepted as the best means of converting an idle process unit, such as a fixed-bed reforming unit, to light paraffin isomerisation. Little capital investment is required, because the idle reforming unit contains all the major equipment required for Par-Isom operation. No additional feed treatment equipment is necessary beyond typical hydrotreating. The newest Par-Isom catalyst, PI-242, is the highest activity non-chlorided catalyst available on the market today. It is contaminant-tolerant and can recover from water or sulphur upsets.
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23/07/2007
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Stephan Zuijdendorp, Albemarle, stephan.zuijdendorp@albemarle.com
With the latest generation of chlorinated alumina isomerisation catalysts, refiners save on platinum investments and gain from long lifecycles and high conversion. Albemarle delivers such catalysts with the ATIS range. In units of IFP-Axens and ABB Lummus Global design, but also other designs, ATIS-1L and ATIS-2L bring such improvements, which finally result in significant cost reduction. Depending on the conditions per unit, a technical and economic evaluation will show if revamping from hydrogen recycle to hydrogen once-through will be of interest. The lower conversion in the liquid phase might be compensated by more active catalysts and reduced yield loss by cracking.
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23/07/2007
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Bruno Domergue, Axens, bruno.domergue@axens.net
Gasoline specifications are getting tighter when it comes to octane, sulphur, olefins and aromatics, which is why interest in isomerisation will grow accordingly. With its octane number up to 25 numbers higher than the C5/C6 cut and the total absence of sulphur, benzene and olefins, isomerate is the ideal gasoline blendstock. From a processing scheme standpoint, several isomerisation options are available, which include the "once-through" (the most simple) and the deisohexaniser recycle (the current favourite), ranging up to complete iso-normal paraffins separation and recycle (a must in the near future for some geographic areas). Of the various types of catalyst available, chlorinated alumina is the most profitable because it gives the highest possible RON, being by far the most active catalyst. It also has the lowest operating and investment costs, owing to low operating temperatures, low recycle flows (for recycle units) and no need for a recycle compressor.
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