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SEPARATION OF ALPHA-OLEFINS FROM A LIQUID HYDROCARBON STREAM

IP.com Disclosure Number: IPCOM000012478D
Publication Date: 2003-May-09
Document File: 9 page(s) / 38K

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Abstract

This invention provides a reactive extractive distillation process for the recovery of 1-hexene using silver nitrate in ethylene glycol as reactive separation solvent

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SEPARATION OF ALPHA-OLEFINS FROM A LIQUID HYDROCARBON STREAM

 

1.      Andre Banier de Haan;2. Norbetus Josef Maria Kuipers and 3. Annebart Engbert Wentink

1.  23 Chopinstraat, Losser, Netherlands;

2.  Tijenesch 1, 7491 GS, Delden, Netherlands;

3.  40 Maanstraat, Enschende, Netherlands.              

Abstract

This invention provides a reactive extractive distillation process for the recovery of 1-hexene using silver nitrate in ethylene glycol as reactive separation solvent.

BACKGROUND OF THE INVENTION

THIS invention relates to the separation of alpha-olefins from a liquid hydrocarbon stream.

The reaction of synthesis gas in a Fischer-Tropsch reactor at elevated temperature and pressure over a Fe or Co catalyst produces a range of hydrocarbons including paraffins, olefins and alcohols, with carbon chain length varying from 1 to greater than 100.  These hydrocarbons are then separated into different products which may then be used in the fuel and chemical industries. 

It is known in the art that the separation of olefins from hydrocarbon streams such as those produced from a Fischer-Tropsch reaction is particularly difficult.  Prior art processes for the extraction of alpha-olefins from hydrocarbon streams derived from Fischer-Tropsch processes involve a distillation step to remove a required cut of hydrocarbons, oxygenates are removed from the cut whereafter it is subjected to etherification followed by superfractionation.  A typical process is described in South African patent no. 98/4676.  Such processes are costly and often do not result in a high purity product.

It is an object of this invention to provide an alternative and improved method for the separation of alpha-olefins from a liquid hydrocarbon stream.

SUMMARY OF THE INVENTION

According to the invention there is provided a method for the removal of alpha-olefins from a liquid hydrocarbon stream including the steps of:

contacting the hydrocarbon stream with a polar solvent containing transition metal ions which selectively form a complex with the alpha-olefins in the hydrocarbon stream;

removing the complexed alpha-olefins, together with the polar solvent, as a bottoms product in a reactive extractive distillation column; and

decomplexing the alpha-olefins from the transition metal ions and removing the alpha-olefin from the polar solvent to obtain an alpha-olefin product.

Advantageously, the polar solvent includes a suitable ligand complexed to the transition metal ion in the solvent.

The polar solvent may be an organic polar liquid.  Typical organic polar liquids include N-methyl-2-pyrrolidone, N-methyl-morpholine, salfolane, alcohols such as ethylene glycol and propylene glycol, or mixtures thereof.  The preferred organic polar liquid is ethylene glycol.

The solvent may be an inorganic polar liquid such as water, or a mixture of polar organic and inorganic liquids, such as a mixture of water and ethylene glycol.

Typical ligands include organic phosphonic acids, organic sulphuric acids and c...