Invented by Margaret M. Wu, Norman Yang, Phil Surana, Anura Patil, Steven P. Rucker, Kuangnan Qian, Shakeel Tirmizi, Mark P. Hagemeister, ExxonMobil Chemical Patents Inc
The ExxonMobil Chemical Patents Inc invention works as followsThis invention describes an improved process that uses mixed alpha-olefins over activated metallocene catalyst systems to produce essentially random liquids polymers, which are particularly useful as lubricant components and as functional fluids.
Background for Lubricants derived from mixed alpha-olefin feedings
PAOs are a class hydrocarbons produced by catalytic polymerization of linear?-olefins. These range from 1-hexene up to 1-octadecene. More commonly, they range from 1-octene up to 1-dodecene. 1-decene is the most popular and preferred material. U.S. Pat. describes such fluids. No. No. No. No.
The HVI-PAOs are thermally and chemically stable enough to use without hydrogenation.
The term “polyalpha olefin” is used in this document. Includes PAOs and HDI-PAOs. The term “PAO” can be used in different contexts. The term “PAO” can be used in conjunction with HVI PAOs, or to differentiate non-HVI PAOs from HVIPAOs. When PAO is used by itself, it means that the products are similar to fluids produced using BF3 and AlCl3 in their conventional polymerization processes or modified versions as described in U.S. Pat. No. No.
It is known that polyalpha-olefins in different viscosity classes are useful for synthetic and semisynthetic grease and lubricant formulations. For example, see Chapters 19-27 in Rudnick and al.’s ‘Synthetic Lubricants & High Performance Functional Fluids, 2nd Edition. Marcel Dekker, Inc., N.Y. (1999). These PAO-based PAO products are superior to mineral oil-based conventional products in terms of viscometrics and performance at high and low temperatures. They are usually energy efficient and have a longer service life.
In the production PAOs and HVIPAOs the feed is typically limited to a specific alpha-olefin, usually 1-decene. When 1-decene in sufficient quantities is not readily available, small amounts of 1-octene and 1-dodecene are added to the mixture to compensate. One-decene has been considered the preferred feed. (See reference “Wide-Temperature range Synthetic Hydrocarbon fluids”). J. A. Brennen, Ind. Eng. Chem. Prod. Res. Dev., 19, 2-6 (1980). Mixtures of feed tend to produce blocky copolymers instead of random copolymers. Products produced at the start of the process may be different from those produced at the finish. In the past, PAOs, HVI-PAOs, and other polymers were made with pure C10 feeds.
Patents from the past report on the use of alpha-olefins mixed with other feedstocks to produce co-oligomers and copolymers that are used as lubricant component components. U.S. Pat. No. No. The process produced liquid copolymers, but the composition of the copolymer is very different from the monomer proportion in the feed. The silica catalyst with reduced chromium oxide polymerized lower alpha olefins such as 1-butene and 1-hexene at a rate that was significantly higher than alpha olefins like 1-decene and 1-dodecene [see examples of comparison in the Example section]. In a conventional synthesis, the copolymer is more blocky and inhomogeneous. Both have detrimental effects on the properties of product VI at low temperatures. Similar to Ziegler and Ziegler-Natta catalysts, it has also been reported that they can copolymerize alpha-olefins mixed with other monomers. U.S. Pat. Nos. Nos. Ziegler and Ziegler-Natta catalysers can only be used to produce polymers with very high molecular masses. The products are therefore used as plastics or additives but not as high-performance base stocks. According to literature, Ziegler and Ziegler-Natta catalysts have higher reactivities towards smaller alpha olefins such as propylene or 1-butene than larger alpha olefins such as 1-decene or 1-dodecene. The difference in catalyst reactivity led to heterogeneous chemical structure for the copolymers. These copolymers are not random and exhibit a high degree of blockiness. “Both characteristics are detrimental to lubricant properties.
It would be highly beneficial if a process could be devised whereby a homogeneous and uniform PAO and/or HVI-PAO having an excellent viscosity-temperature relationship could be produced from a wide variety of mixed feed LAOs.
The present inventors discovered a new method to produce a uniform HVI-PAO or PAO by contacting LAOs with varying carbon number with an activated metallocene catalyst.
The invention is a process that produces PAOs or HVI-PAOs by contacting a feed containing a mixture LAOs, with an activated Metallocene catalyst, optionally following hydrogenation. This results in liquid polymers of superior properties, suitable for use as lubricant component fluids or functional fluids.
This invention also relates to a copolymer composed of at least two alpha olefins in the C3 to C30 region, with monomers distributed randomly within the polymers. The average carbon number as defined in the present invention is preferably at least 4.1. If present, ethylene or propylene are present at a level of less than 50 wt%, individually, or more preferably, less than 50 wt% when combined. Copolymers can be of any tacticity, including isotactic or atactic polymers, syndiotactic or other forms. These copolymers are useful for lubricants, with excellent VI, pour points, and low temperature viscometrics, whether used as a blend fluid or alone. These copolymers also have narrow molecular-weight distributions and good shear stability.
In one embodiment, the mixed-feed LAOs are composed of at least two different linear alpha olefins from C3-C30. In a preferred embodiment the mixed feed LAO can be obtained by an ethylene-growth process using an aluminium catalyst or a metalliclocene catalyst.
In another embodiment the alpha-olefins may be selected from any component of a conventional LAO, together with another LAO from a chemical or refinery plant. This can include propylene or other components such as 1-butene and 1-pentene. It could also be 1-hexene produced in a dedicated facility. In a second embodiment, alpha-olefins are selected from alpha olefins derived from Fischer-Tropsch (as described in U.S. Pat. No. 5,382,739).
The activated metallocene catalyst can be metallocenes simple, substituted metallocenes and bridged metallocenes that are activated or promoted, for example, by MAO or non-coordinating anion.
It is the object of this invention to provide an easy method for making a new HVI-PAO or PAO from various feedstocks.
The following detailed description will reveal these and other features and benefits.
Accordingly to the invention, an feed containing a mixture LAOs from C3-C30 is contacted under oligomerization with a metallocene activated catalyst to produce a liquid suitable for use as lubricant components, or functional fluids. Optionally, this product can be hydrogenated. This invention also relates to a copolymer composed of at least two alpha olefins in the C3 to C30 region, with monomers distributed randomly within the polymers. The phrase “at least two alpha olefins” is used. The phrase?at least 2 alpha-olefins’ will be understood as?at most two different types of alpha-olefins. “At least two alpha-olefins” will be understood to mean?at most two different alpha-olefins?” “At least three alpha-olefins” means “at least three different types of alpha-olefins”.
In preferred embodiments the average carbon number of said two alpha-olefins (defined below) in said feed must be at least 4.1. In a second preferred embodiment, ethylene and propylene are less than 50 wt% each or more preferably combined. “Another preferred embodiment is a feed that has both the above preferred embodiments. That is, a feeding having an average carbon value of at least 4,1 and wherein ethylene and propylene are less than?50wt% individually.
In embodiments, the liquid copolymer obtained comprises at least two alpha olefins. “Essentially random” is meant by “essentially random”. By?essentially random? Herein are other characterizations for randomness. Some of them are preferred. The term “liquid” is also used. The term will be understood by a person of ordinary skill, but here are some preferred descriptions of the word. When describing products as “comprising”, the term is used. A certain number (at least two alpha olefins) of alpha olefins. One of ordinary skill would understand the product described as the polymerization or oligomerization product that incorporates said certain number. It is, in other words the product that results from polymerizing (or oligomerizing) a certain number of monomers.Click here to view the patent on Google Patents.