Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By double-bond-shift isomerization
Reexamination Certificate
2000-02-18
2001-08-28
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By double-bond-shift isomerization
C585S667000, C585S670000
Reexamination Certificate
active
06281404
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the double bond isomerization of olefinic feed compounds in the presence of a molecular sieve of specific pore geometry.
BACKGROUND OF THE INVENTION
Molecular sieves are crystalline materials which have distinct crystal frameworks with ordered pore structures and cavities. Aluminosilicate zeolite-type molecular sieves useful as adsorbents or catalysts are known in the art and now comprise over 150 species of both naturally occurring and synthetic compositions. In general, the zeolites have frameworks formed from AlO
4
-and SiO
4
tetrahedra joined by the sharing of oxygen atoms. Such zeolites have a significant ion-exchange capacity and are capable of reversibly desorbing an adsorbed phase which is dispersed through the internal voids of the crystal without displacing any atoms which make up the permanent crystal structure.
Non-zeolite molecular sieves comprising aluminophosphates are also known to be useful as adsorbents or catalysts. These non-zeolite molecular sieves generally contain [AlO
2
] and [PO
2
] tetrahedral units as essential framework constituents, and at least one additional element as a framework tetrahedral unit.
Various catalysts are known for their use in the double bond isomerization of olefinic feed compounds. However, many of these catalysts produce substantial amounts of polymer and/or skeletal isomerized product, i.e., branched olefins. For some applications, such as preparing internal olefins for alkylation reactions, it is desirable to limit branched products to the least amount possible. Therefore, for certain applications, it is desirable to use a catalyst which is selective for the isomerization of the double bond without the isomerization of the skeletal structure.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the double bond isomerization of olefinic compounds.
It is another object of the present invention to provide a process with high conversion rates.
It is another object of the present invention to provide a process with high selectivity for internal linear olefins.
It is another object of the present invention to provide a process which produces low amounts of branched olefins.
It is another object of the present invention to provide a process with reduced catalyst coking.
It is another object of the present invention to provide a process with increased catalyst life span.
A process for the double bond isomerization of normal alpha olefins having from 4 to 50 carbon atoms, the process which comprises contacting the alpha olefins with a catalyst under reaction conditions sufficient to produce double bond isomerization, wherein the catalyst comprises an aluminophosphate-containing molecular sieve with one-dimensional pores having a diameter in the range of from about 3.8 Å to about 5.0 Å and wherein said catalyst at a conversion rate of 60% will give a yield of branched olefins of less than 3.5 weight % with a feed of 1-pentene. Preferably the catalyst will contain an element which form oxide linkages in tetrahedral coordination with the aluminum and phosphorous in the crystalline network. The element forming the oxide linkage generally will be selected from the group consisting of silicon, arsenic, beryllium, boron, chromium, cobalt, gallium, germanium, iron, lithium, magnesium, manganese, titanium, vanadium, and zinc. Particularly preferred is silicon. In practicing the present invention the catalyst will preferably be silica-containing aluminophosphate molecular sieve which is usually referred to as a SAPO. Examples of catalyst useful in carrying out the process of the present invention are SAPO-22 and SAPO-39, with SAPO-39 being particularly preferred.
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Ambrosius James W.
Chevron Chemical Company LLC
Griffin Walter D.
Nguyen Tam M.
Scott Reece A.
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