Ultrasonic catalyst feed for fluid bed olefin polymerization

Details Ultrasonic catalyst feed for fluid bed olefin polymerization Ultrasonic catalyst feed for fluid bed olefin polymerization

2000-04-11

2002-04-02

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S901000, C526S919000

Reexamination Certificate

active

06365695

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the manufacture of polyolefins in fluidized beds, and particularly to processes for feeding liquid catalyst into fluidized bed polyolefin reactors.
BACKGROUND OF THE INVENTION
Liquid catalysts offer many advantages over traditional solid-supported catalysts for the gas phase polymerization of olefins. Feeding of liquid catalysts into reactors has, however, often led to reactor and/or nozzle fouling. Traditional nozzles for spraying liquids,, such as gas assisted nozzles and conventional two-fluid nozzles, require critical coordination of the flow rates of the gas and liquid for satisfactory performance. Flow rates of both the components and the mixture are functions of the nozzle design, particularly the orifice diameter and gas mixing site. Generally, traditional nozzles deliver dense, high velocity sprays immediately downstream of the nozzle exit. The density and velocity of the spray causes it to tend to deposit on the resin in the fluidized bed, leading to accelerated polymerization on the surface of the resin particles already formed. Continued coating with catalyst and the subsequent surface reaction can lead to the formation of resin particles too large to be fluidized in the bed, in turn leading to shut-down of the reactor, a very expensive event. Growth of resin particles from agglomeration effects can also occur due to concentrated catalyst activity. A high initial reaction rate increases the temperature of the young polymer particles, causing them to approach temperatures near, or in excess of, the resin softening temperature. The soft, or molten, resin can adhere to other particles in the bed, resulting in agglomeration and uncontrolled particle growth.
Poor control over catalyst distribution can also lead to unacceptably high concentrations of fine resin particles, which tend to increase the undesirable effects of static electricity, always a potential problem in the reactor. As is known, static charges lead to unwanted accumulations of resin and sheeting. Fine particles also can lead to fouling of the recycle piping, compressor, and heat exchanger.
The use of liquid catalysts in fluidized bed olefin polymerization is discussed in Brady et al U.S. Pat. No. 5,317,036 and in Goode and Williams U.S. Pat. No. 5,693.727, both of which are incorporated herein by reference. See also Keller et al U.S. Pat. No. 5,744,556.
Ultrasonic liquid atomizers are known. See, for example, Berger's U.S. Pat. No. 4,655,393 and Tsai's U.S. Pat. No. 5,687,905, which uses concentric gas introduction to assist in atomization.
Ultrasonic energy has been used to make olefin polymerization catalyst components—see U.S. Pat. No. 4,730,071, col. 1 lines 52-53 and examples 1, 4, and 5; col. 4, lines 19-20; U.S. Pat. No. 5,455,366 col. 20, line 20, U.S. Pat. No. 3,979,370, col. 3 line 13; U.S. Pat. No. 5,559,199, col. 38 line 42; U.S. Pat. No. 5,830,821, col. 18 line 62, and U.S. Pat. No. 5,780,562, col. 16, line 48. However, these processes generally involve the use of ultrasonic baths or dispersions or occasionally breaking up solids. Ultrasonic nozzles are suggested for making polymerization catalysts in U.S. Pat. No. 5,215,949.
Liquid catalysts have been fed to a combustion reaction zone—see U.S. Pat. No. 5,386,690, col. 5 lines 1-8; in four related U.S. Pat. No. 5,804,677 (col. 13, line 42), U.S. Pat. No. 5,733,510 (col. 13, line 44), U.S. Pat. No. 5,668,228 (col. 13, line 44) and U.S. Pat. No. 5,541,270 (col. 13, line 40) a liquid recycle in olefin polymerization is assisted with ultrasonic nozzles.
Methylaluminoxane was fed together with ethylene through an ultrasonic nozzle into a polymerization reactor, which resulted in “no activity from the zirconium sites”—page 26, WO94/14856.
Many conventional nozzles provide unbroken ligaments of liquid from the nozzle rather than discrete droplets if all conditions are not right—for example, a minimum flow rate. Where high activity solution catalysts are to be fed, it has been observed that substantial amounts of diluent, such as isopentane, must be used to maintain liquid flow rates above the critical value in order to assure droplet formation.
SUMMARY OF THE INVENTION
Our invention provides for the use of an ultrasonic nozzle to feed liquid catalyst to a fluidized bed olefin reactor. A prime example of the type of reactor, and the catalysts fed to it, to which our invention is applicable, is given in the aforementioned Brady et al U.S. Pat. No. 5,317,036, which is incorporated herein by reference. Our invention is useful for any and all known olefin polymerization catalysts to be fed in liquid form. These are generally known in the art but include those identified and referenced by Goode and Williams in U.S. Pat. No. 5,693,727, which is incorporated entirely herein by reference. Our invention may also be used in other known types of commercial fluid bed polyolefin manufacturing systems. Common olefins polymerized by our process include ethylene, propylene, and butadiene, but any other polymerizable olefins and mixtures of olefins are included within the scope of our invention.
The use of ultrasound (or ultrasonic vibrations) to create liquid droplets is a powerful means of introducing liquid catalysts into a gas phase polymerization reactor, such as a UNIPOL reactor for polymerization of ethylene and other olefins as discussed in the Brady '036 patent. The ultrasonic nozzle can be located in a “particle-free” zone, such as the disengagement section or the zone below the fluidized bed (in the absence of a distributor plate) or within a “particle lean” zone. A particle-lean zone may be created by surrounding the catalyst composition droplets with a deflecting gas introduced preferably concentrically with the liquid catalyst composition.
We use the term “liquid catalyst composition” herein to mean olefin catalyst, cocatalyst or activator in liquid form, i.e. either neat, dissolved, emulsified or mixed, and substantially free of gas. The cocatalyst or activator, if used in the liquid catalyst composition, is typically methylaluminoxane (MAO) but may be any of the other cocatalysts described by Goode and Williams in the '727 patent. In particular, the catalyst can be composed of one or more metal compounds in combination with one or more co-catalysts. Alternatively, all or a portion of the cocatalyst can be fed separately from the metal compound(s) to the reactor. Promoters associated with any particular polymerization are usually added to the reactor separately from the cocatalyst and/or compound(s). Our invention may feed any liquid catalyst composition, including Ziegler-Natta catalysts, chromium based catalysts, vanadium based catalysts, metallocene catalysts, cationic forms of metal halides, cobalt catalysts and mixtures thereof, nickel catalysts and mixtures and rare earth metal catalysts all as known in the art and/or as described in more detail in the herein incorporated Goode and Williams U.S. Pat. No. 5,693,727.
If the metal compound and/or the cocatalyst occurs naturally in liquid form, it can be introduced “neat” through the ultrasonic nozzle and into a particle lean or particle free zone. More likely, the liquid catalyst is introduced into the particle lean zone as a solution (single phase, or “true” solution using a solvent to dissolve the metal compound and/or cocatalyst), an emulsion (partially dissolving the catalyst components in a solvent), suspension, dispersion, or slurry (each having at least two phases). Preferably, the liquid catalyst employed is a solution or an emulsion, most preferably a solution. As used herein, “liquid catalyst” or “liquid form” includes neat, solution, emulsion, and dispersions of the transition metal or rare earth metal component(s) of the catalyst and/or cocatalyst.
The solvents that can be utilized to form solutions of the soluble, unsupported transition metal and/or rare earth metal polymerization catalyst compounds are inert solvents, preferably nonfunctional hydrocarbon solvents, and may include nongaseous solvents having from 2 to

Affiliated with

Also associated with

Rating

Ultrasonic catalyst feed for fluid bed olefin polymerization does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ultrasonic catalyst feed for fluid bed olefin polymerization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasonic catalyst feed for fluid bed olefin polymerization will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2916572