Chemistry of hydrocarbon compounds – Plural serial diverse syntheses – To produce unsaturate
Reexamination Certificate
2000-11-21
2003-12-09
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Plural serial diverse syntheses
To produce unsaturate
C585S324000, C585S329000, C585S502000
Reexamination Certificate
active
06660894
ABSTRACT:
The present invention relates to a process for upgrading an oligomerization product through use of hydrogenation, selective/minor cracking and isomerization. More particularly, the invention relates to a process for upgrading an oligomerization product through catalytic hydrogenation, selective/minor cracking, and isomerization to yield a synthetic base oil with improved pour point, and increased viscosity index.
BACKGROUND OF THE INVENTION
Preparation of base oil stocks by hydrocracking, dewaxing, and hydrotreating is well known in the art. Generally, mineral oil based hydrocarbon feedstocks with paraffinic content are dewaxed to remove the easily solidified paraffins. Dewaxing may be generally accomplished through two methods. The first method involves hydrocracking in the presence of shape selective catalysts capable of selectively cracking n-paraffins and iso-paraffins. Commonly used shape selective catalysts for hydrocracking are crystalline aluminosilicate zeolites optionally associated with a hydrogenating metal. Typical conditions for catalytic hydrocracking include a temperature between 290° C. and 450° C. and hydrogen partial pressure of 250-1500 psig. Dewaxing may also be performed through solvent dewaxing using refrigeration to crystallize the paraffinic portion of the feed and using a solvent, such as methyl-ethyl-ketone, to sufficiently dilute the oil portion permitting rapid filtration to separate the wax from the oil. Dewaxing is further described by J. Gary and G. Handwerk in Petroleum Refining Technology and Economics, 1984, 2
nd
ed., p. 241-245, which is incorporated by reference herein. Hydrotreating is typically done following catalytic dewaxing to saturate olefinic by-products of the dewaxing process, improve stability, and reduce sulfur content. Hydrotreating processes are described in U.S. Pat. No. 4,267,071 and 4,600,503, which are incorporated by reference herein.
While the purpose of the above mentioned processes is to produce a lubricating base oil with improved stability, pour point, and viscosity index, it is widely believed in the industry that certain levels of oxidative and thermal stability in lubricant oils can only be obtained by using full synthetic formulations as opposed to mineral oil based lubricants. Oxidative stability refers to the ability of the oil to resist oxidation, which generally leads to deterioration of the oil. The belief in the superiority of synthetics has lead to an increasing demand in the industry for high performance, high viscosity index synthetic base oils with high oxidative stability and low pour point. Currently, poly-alpha-olefins (PAOs) are commonly used as synthetic base oils. PAOs are typically produced through the polymerization of 1-alkenes using a Lewis acid, such as AlCl
3
or BF
3
, or Ziegler-catalysts. Their preparation and properties are described by J. Brennan in Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, p. 2-6, which is incorporated herein by reference. PAOs are also described in U.S. Pat. No. 3,742,082, which is incorporated herein by reference. PAOs provide low temperature fluidity (e.g. low pour point), high viscosity index and high oxidative stability; however, PAOs also have a high manufacture price, generally associated with the expense of the 1-alkene feedstock required for PAO production.
This has created a demand for a low cost alternative to PAOs, such as a process for making synthetic base oils from oligomerization products. U.S. Pat. No. 4,650,917, for example, discloses a method for enhancing the viscosity index of a synthetic lubestock by contacting the synthetic lubestock with a solid acidic catalyst, such as an acidic zeolite, under isomerization conditions, then separating out the high viscosity index fraction through sorbing by a shape-selective zeolite, followed by desorbing. Viscosity index is an important characteristic of lubricants because it provides a measure of how much the viscosity of the lubricant changes with temperature. High viscosity index, which indicates a relatively lower rate of viscosity change with temperature, is generally desired. Viscosity index is typically higher in paraffinic stocks, especially paraffinic stocks with minimal branching. This raises a problem, however, because such paraffinic stocks also typically have high pour points, an undesirable quality. Therefore, development of a process for improving the viscosity index and pour point of an oligomerization product for use as a synthetic base oil would be a significant contribution to the art and to the economy.
BRIEF SUMMARY OF THE INVENTION
It is thus an object of this invention to provide an improved process for upgrading an oligomerization product through hydrogenation, selective/minor cracking, and isomerization of the oligomerization product.
It is another object of this invention to provide an improved process for producing a synthetic base oil comprising upgrading an oligomerization product through hydrogenation, selective/minor cracking and isomerization.
It is a further object of this invention to provide a novel catalyst system effective for upgrading an oligomerization product through hydrogenation, selective/minor cracking and isomerization.
It is still another object of this invention to employ this novel catalyst system as a catalyst in the upgrading of an oligomerization product through hydrogenation, selective/minor cracking and isomerization.
The present invention provides a process for upgrading an oligomerization product through hydrogenation, selective/minor cracking and isomerization. The oligomerization product can be an oligomer of an olefin, a co-oligomer of two different olefins or a ter-oligomer of three different olefins. The present invention further provides a process for producing a synthetic base oil by upgrading an oligomerization product. The upgrading process results in a synthetic base oil that exhibits at least one of the following improvements over the oligomerization product:
lower pour point as determined using test method ASTM D97;
higher viscosity index as determined using test method ASTM D567.
Further, the upgrading process results in a product that exhibits physical characteristics making it desirable for use as a synthetic base oil. Such physical characteristics include, but are not limited to, a pour point that is less than 0° C. and a viscosity index that is greater than 100. These values for pour point and viscosity index are representative of commercially acceptable values for a lube base oil.
Also provided in the present invention is a catalyst system for upgrading an oligomerization product. The novel catalyst system comprises a first solid material comprising a porous carrier material and a group VIII metal, and a second solid material comprising an aluminosilicate zeolite. Additionally, a process is provided for the upgrading of an oligomerization product by contacting under conversion conditions the oligomerization product with the novel catalyst system.
Other objects and advantages will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The oligomerization product to be upgraded according to the present invention comprises oligomeric olefins. Each of the olefins, as they exist in their state prior to oligomerization to form the oligomerization product, typically contain at least 2 and less than 16 carbon atoms per molecule. More typically, each of the olefins, prior to oligomerization, contain at least 2 and less than 10 carbon atoms per molecule; and most typically, each of the olefins, prior to oligomerization, contain at least 2 and less than 5 carbon atoms per molecule. Oligomerization of the olefin units may be carried out by any commonly used method. Because methods of oligomerization are well known to those skilled in the art, a description of such a method of oligomerization is omitted herein for the interest of brevity. Such methods of oligomerization are described in U.S. Pat. Nos. 5,942,642 and 4,526,950, which are incorporated by reference herein.
The oligomerization produc
Drake Charles A.
Knudsen Ronald D.
Wu An-hsiang
Carroll Rodney B.
Conley & Rose, P.C.
Dang Thuan D.
Hulett Joe D.
Phillips Petroleum Company
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