Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Reexamination Certificate
2001-11-30
2004-06-01
Dang, Thuan Dinh (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
C585S511000, C585S512000, C585S513000, C585S515000, C585S521000, C585S522000, C585S523000, C585S526000
Reexamination Certificate
active
06743960
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to oligomerization of olefins to form higher olefins, especially higher &agr;-olefins. The instant invention also relates to the use of sulfur-containing and sulfur-tolerant catalysts to perform the oligomerization.
2. Description of the Related Art
Linear &agr;-olefins are very important and versatile intermediates and building blocks for the chemical industry. The main applications for linear &agr;-olefins are using C
4
-C
8
&agr;-olefins as co-monomers for polyethylene, C
6
-C
10
&agr;-olefins as feedstocks for plasticizers, and C
12
-C
20
&agr;-olefins for surfactants. Hydrocarboxylation of the C
6
-C
8
&agr;-olefins with cobalt carbonyl/pyridine catalysts gives predominantly linear carboxylic acids. The acids and their esters are used as additives for lubricants. The C
6
-C
10
&agr;-olefins are hydroformylated to odd-numbered linear primary alcohols, which are converted to phthalate esters (by reaction with phthalic anhydride) as polyvinyl chloride (PVC) plasticizers. Oligomerization of 1-decene, using BF
3
catalysts, gives oligomers used as synthetic lubricants known as poly-&agr;-olefins (PAO) or synthetic hydrocarbons. The C
10
-C
12
&agr;-olefins can be epoxidized by peracids; this opens up a route to bifunctional derivatives or ethoxylates as nonionic surfactants.
Oligomerization of olefins is a major route that is currently used to make higher olefins, especially &agr;-olefins. Other routes to &agr;-olefins in decreasing importance are: paraffin wax cracking, paraffin dehydrogenation, and alcohol dehydration. A variety of catalysts for olefin oligomerization based on both early and late transition metals have been reported. One method uses Al-alkyls and is based on improvements to the original 1952 Ziegler's
Alfen process.
Another example is the Shell Higher Olefin Process (SHOP), in which a nickel hydride catalyst is used. While these catalysts are highly active and effective, they normally only work with clean feeds. In other words, possible contaminants such as H
2
, CO, and especially mercaptans and thiophene, which are likely to exist in the feed, will poison the catalysts. Late transition metal catalysts are generally thought to be relatively insensitive to non.-sulfur-containing contaminants such as H
2
and CO; however, sulfur-containing contaminants are potent poisons to late transition metal catalysts. Removing the contaminants and cleaning up the feed adds cost to current olefin oligomerization processes. It is therefore desirable to develop a catalyst that can work directly with crude feed, thereby offering potential cost-saving advantages to the process of olefin oligomerization.
Research in the area of olefin oligomerization has been very extensive, and there is continuing interest in developing new and more robust catalysts. Catalysts ranging from transition metal complexes, organoaluminum compounds, and Lewis and Brnsted type compounds to inorganic salts and oxides have been reported.
Compared to the large body of literature available on olefin oligomerization catalysts with nitrogen and/or phosphorous ligands, there have been very few reports in the open literature describing olefin oligomerization catalysts with sulfur ligands. Masters, et al. (
J. Chem. Soc. Dalton Trans.
1993, 59-68; U.S. Pat. No. 4,533,651; WO 83/02907) reported a system that comprises a nickel(II) complex and a co-catalyst. The nickel(II) complex is a square-planar species with a phosphine or phosphite ligand, a halogen ligand, and a substituted dithio-&bgr;-diketone ligand. The co-catalyst is an aluminum alkyl or an alkyl-aluminum chloride. The system catalyzes the oligomerization and/or isomerization of olefins. However, whether the system was contaminant-tolerant was not raised or discussed.
Japanese Patent No. 70007522 discloses a catalyst for co-oligomerization of butadiene and ethylene, wherein the catalyst consists of: (1) a metal complex having the formula M(S
2
C
2
Ph
2
)
2
, where M is Ni or Co and Ph is a phenyl radical; and (2) an organic Al compound of general formula R
3
Al or R
2
AlX, wherein R is a hydrocarbon radical and X is a halogen atom. A mixture of isomers, including C6-C8 dienes, C10 trienes, and vinylcyclohexane, is formed as a result of coupling between butadiene and ethylene, and the product ratio is dependent on the metal used. No oligomerization product from ethylene was observed even though ethylene of pressures up to 700 psig was used.
Riccardo Po, et al., Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 36, 2119-2126 (1998), discloses the polymerization of styrene using catalytic systems based on nickel derivatives and methylaluminoxane. Even though compound Ni(Ph
2
C
2
S
2
)
2
(labeled PS8b) was listed among the catalysts tested, it did not produce any polymeric product, indicating that the compound was inactive in polymerizing styrene.
Organometallic catalyst technology is also a viable tool in oligomerization processes that produce linear &agr;-olefins for use as feedstock in various other processes. However, one problem often encountered when using many of these catalyst systems is the propensity to produce &agr;-olefins with very low selectivity (i.e., a Schulz-Flory type distribution with high k values). For instance, many of the linear &agr;-olefins made today utilize a neutral nickel (II) catalyst having a planar geometry and containing bidentate monoanionic ligands. While these planar nickel (II) catalysts do produce linear &agr;-olefins, these catalysis systems exhibit a Schulz-Flory type of distribution over a very wide range (i.e., C
4
-C
30+
).
To address the Schulz-Flory distribution problem, chromium metal-based catalysts have become popular for use in certain oligomerization processes. More precisely, chromium complexes have been used to oligomerize ethylene in order to form linear &agr;-olefins with improved distributions. In fact, there have been reports of specific chromium catalysts that selectively trimerize ethylene to 1-hexene. See U.S. Pat. Nos. 5,814,575, 5,763,723 and 5,550,305. These techniques employ the use of a chromium compound in conjunction with aluminoxane along with one of a variety of compounds such as nitrites, amines and ethers. Unfortunately, while these techniques have been able to selectively produce &agr;-olefins, polymer is formed as a co-product. Of course, when polymer is co-produced, the yield of desirable &agr;-olefin products decreases accordingly. Also, as a practical matter, polymer build-up in the reaction vessel can severely hamper production efficiency, thereby limiting the commercial use of such processes.
As discussed above, the organometallic catalyst technology now being used to produce &agr;-olefins has two major disadvantages. First, many of the organometallic catalysts produce &agr;-olefins with a Schulz-Flory type distribution. Unfortunately this Schulz-Flory type distribution is not ideal when short chain &agr;-olefins are desired; in other words, the selectivity is not good enough to maintain efficient processes. Because &agr;-olefins are used as intermediates for specific products, &agr;-olefins with certain chain lengths are desired. For instance, the following are examples of &agr;-olefin chain lengths that would be desirable as feeds for certain product types: C
4
to C
8
for co-monomer in ethylene polymerization; C
10
for lube quality poly-&agr;-olefins; and C
12
to C
20
for surfactant products. Thus, considerable inefficiency and waste are present when significant amounts of &agr;-olefins are produced having chain lengths outside of the range required for production of a particular chemical. Second, while some of the current organo-metallic catalysts may improve selectivity, most also produce polymer co-products. This lowers the yield of the desired product. Additionally, the polymer co-products can also accumulate in the reaction vessel. These disadvantages make commercial use of organo-metallic catalysts less attractive and inefficient. Hence, there is still
Patil Abhimanyu Onkar
Stiefel Edward Ira
Wang Kun
Zushma Stephen
Dang Thuan Dinh
ExxonMobil Research and Engineering Company
Wang Joseph C.
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