Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-05-08
2003-11-25
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C585S329000, C585S512000, C585S523000, C585S527000, C585S823000
Reexamination Certificate
active
06653514
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to a process of removing contaminants from olefin feedstocks using sorbents. In a preferred embodiment, phosphorus-containing impurities, most preferably organophosphines and/or organophosphine oxides, are removed from the olefin feedstock using an acidic or a neutral sorbent. The sorbent preferably is selected from the group consisting of an acidic ion exchange resin, an acidic zeolite, an acidic alumina, a neutral alumina, and an activated carbon. Preferred olefin feedstocks are those made by oligomerizing ethylene to linear olefins having from about 6 to about 36 carbon atoms, preferably from about 11 to about 20 carbon atoms, and most preferably from about 14 to about 18 carbon atoms.
BACKGROUND OF THE INVENTION
Depending upon the method of their production, olefin feedstocks may comprise a variety of impurities. Impurities found in olefins that are produced by oligomerization of ethylene units include phosphorous-containing impurities, including but not necessarily limited to organophosphines and organophosphine oxides. These phosphorous-containing impurities are largely removed from many olefin streams during the process of distillation to separate various “cuts” of olefins. Unfortunately, the organophosphines and organophosphine oxides found in C
14
-C
18
streams tend to codistill with the C
14
-C
18
in the product, making it difficult, if not impossible to remove these phosphine impurities by simple distillation.
C
6
-C
36
olefins have utility in the fields of paper and pulp processing, drilling fluids, and machine or metal working oils. Alcohols of such olefins have commercial importance in a variety of applications, including detergents, soaps, surfactants, and freeze point depressants in lubricating oils. These alcohols are produced by a number of commercial processes, such as by oxo or hydroformylation of long chain olefins. In many of these applications, the olefin feedstocks are treated using acid catalysts.
Unfortunately, any phosphorus-containing impurities in these olefin feedstocks will negatively affect acid catalysts. The phosphorous-containing moieties are basic in nature and will neutralize the active acid sites of the catalyst, which lowers catalyst activity and performance. The organophosphine moeities may even cause the olefins to oligomerize into undesirable forms.
Methods are needed to reduce the phosphorous-content of olefin feedstocks.
SUMMARY OF THE INVENTION
The present invention provides a process for purifying an olefin feed comprising a content of phosphorus-containing impurities. The process comprises contacting the olefin feed with a sorbent selected from the group consisting of an acidic ion exchange resin, an acidic zeolite, an acidic alumina, a neutral alumina, and an activated carbon under conditions and for a time effective to reduce the content of phosphorus-containing impurities and to produce a purified olefin feed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process and sorbents which efficiently and effectively reduce the content of phosphorous-containing impurities in olefin streams. In a preferred embodiment, the content is reduced to about 1 ppm or less, preferably about 0.5 ppm or less, most preferably to about 0.1 ppm or less. Given sufficient run time, the sorbents reduce the content of phosphorous-containing impurities in the olefin stream to parts per billion (ppb) levels. In a preferred embodiment the sorbents of the present invention may be used to remove dienes from the olefin stream.
The invention may be used to treat substantially any olefin stream. Preferred olefin streams are linear olefin streams made by oligomerizing ethylene. Some of the known processes for oligomerizing ethylene use organophosphorus compounds that result in phosphorus as a contaminant in the resulting olefin stream. A preferred commercially available olefin feed for the treatment of the present invention is the product marketed in the United States by Shell Chemical Company under the trademark NEODENE®. In a preferred embodiment, the olefin feedstock is treated before exposure to an acid catalyst, or before exposure to other conditions which would be adversely affected by the basic nature of phosphorus-containing contaminants.
In a most preferred embodiment, the olefin stream is the feedstock for the skeletal isomerization catalyst used in the method described in U.S. Pat. No. 5,849,960, which has been incorporated herein by reference. The olefins used in the feed to this skeletal isomerization catalyst are mono-olefins having at least 6 carbon atoms, preferably having from about 11 to about 20 carbon atoms, and most preferably having from about 14 to about 18 carbon atoms.
In general, the olefins in the feed to the skeletal isomerization catalyst are predominately linear. While the olefin feed can contain some branched olefins, the olefin feed processed for skeletal isomerization preferably contains greater than about 50 percent, more preferably greater than about 70 percent, and most preferably greater than about 80 mole percent or more of linear olefin molecules.
The olefin feed to the skeletal isomerization catalyst does not consist of 100% olefins, and usually contains a distribution of mono-olefins having different carbon lengths, with at least 50 wt. % of the olefins being within the stated carbon chain range or digit, however specified. Preferably, the olefin feed will contain greater than 70 wt. %, more preferably about 80 wt. % or more of mono-olefins in a specified carbon number range, the remainder of the product being olefins of other carbon number or carbon structure, diolefins, paraffins, aromatics, and other impurities resulting from the synthesis process. The location of the double bond is not limited. The olefin feed composition may comprise alpha olefins, internal olefins, or a mixture thereof.
The sorbent of the present invention may be substantially any suitable sorbent capable of sorbing phosphorus-containing impurities, preferably neutral and acidic sorbents, most preferably acidic sorbents. Suitable neutral sorbents include neutral aluminas, activated carbons, and metal impregnated activated carbons, such as BARNEBEY CE, a silver impregnated carbon available from Barnebey & Sutcliffe. Suitable acidic sorbents include, but are not necessarily limited to acidic ion exchange resins and acidic aluminas. Suitable commercially available aluminas include, but are not necessarily limited to acidic and neutral activated aluminas, such as those available from Aldrich Chemical Co. and Selecto Scientific Co. Also suitable are the modified aluminas, such as SELEXSORB CDO 200, SELEXSORB CDX, AND SELEXSORB CD. These aluminas are modified to improve the sorption of polar organics, and are commercially available from Alcoa Industrial Chemicals. Also suitable are acidic ion exchange resins, such as AMBERLYST 15 RESIN, available from Rohm & Haas Chemical Co.
The surface area of the sorbent is not critical, but preferably is at least about 10 m
2
/g in order to provide sufficient contact between the sorbent and the olefin stream. In a preferred embodiment, the sorbent has a surface area of from about 100 m
2
/g to about 900 m
2
/g. It is preferred for the sorbent particles to be as small as possible; however, if the size of the particles is too small, the pressure drop through the bed becomes too large. Very small particles also are difficult to retain in the sorbent bed. The particles may have substantially any form, including but not necessarily limited to spherical form, tablet form, cylindrical form, multilobed cylindrical forms, and their corresponding hollow counterparts. In a preferred embodiment, the particles have a diameter of from about 50 mesh to about 6 mm, preferably about 0.8 mm ({fraction (1/32)} inch) to about 1.6 mm ({fraction (1/16)} inch), most preferably about 0.8 mm. The length of the particles is not critical, with suitable lengths including, but not necessarily limited to less than about 10 mm, preferably from about 3 mm to about 5 mm.
In a pr
Diaz Zaida
Murray Brendan Dermot
Singleton David Michael
Price Elvis O.
Richter Johann
Shell Oil Company
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