Spheripol process

Fig. 11. Spheripol process flow diagram (131). CW = cooling water. Courtesy of Gulf PubHshing Co.

Third-generation high yield supported catalysts are also used in processes in which Hquid monomer is polymerized in continuous stirred tank reactors. The Hypol process (Mitsui Petrochemical), utilizes the same supported catalyst technology as the Spheripol process (133). Rexene has converted the hquid monomer process to the newer high yield catalysts. Shell uses its high yield (SHAC) catalysts to produce homopolymers and random copolymers in the Lippshac process (130). 

An example of the liquid-phase polymerization is the Spheripol process (Figure 12-3), which uses a tubular reactor. Copolymerization... 

Figure 12-3. The Himont Inc. Spheripol process for producing polypropylene in a liquid-phase (1) tubular reactor, (2,4) two-stage flash pressure system (to separate unreacted monomer for recycle), (3) heterophasic copolymerization gas-phase reactor, (5) stripper.

Impact copolymer production, in the Spheripol process, 20 538 Impact copolymers, 26 538 Impact ionization avalanche transit time (IMPATT) diodes, compound semiconductors in, 22 160-162 Impact modifiers... 

The similar, older slurry process uses a less active catalyst. The monomer is dissolved in isooctane, the titanium catalyst and aluminium cocatalyst are added and this mixture is fed to the reactor which is maintained at 70°C. The inorganic corrosive (Cl) residues are removed in a washing step with alcohols. The atactic material is removed by extraction. A third process employs propene as the liquid in combination with a high activity catalyst. The Himont Spheripol process, which uses spherical catalyst particles, gives spherical polymer beads of millimetre size that need no extrusion for certain purposes. A more recent development is the gas-phase polymerization using an agitated bed. All processes are continuous processes, where the product is continuously removed from the reactor. Over the years we have seen a reduction of the number of process steps. The process costs are very low nowadays, propene feed costs amounting to more than 60% of the total cost. 

Application Spheripol process technology produces propylene-based polymers including homopolymer PP and many families of random and heterophasic impact and specialty impact copolymers. 

Description In the Spheripol process, homopolymer and random copolymer polymerization takes place in liquid propylene within a tubular loop reactor (1). Heterophasic impact copolymerization can be achieved by adding a gas-phase reactor (3) in series. 

Economics The Spheripol process offers a broad range of products with excellent quality and low-capital and operating costs. 

Commercial plants Spheripol technology is used for about 50% of the total global PP capacity. There are 94 Spheripol process plants operating worldwide with total capacity of about 17 million tpy. Single-line design capacity is available in a range from 40,000 to 550,000 tpy. 

Spherizone A development of the Spheripol process for making polypropylene. A special zone is established in the continuous circulating reactor in which additional monomer or a comonomer can be introduced in order to make polymers with different properties. The copolymers can be monomodal, bimodal, random, or twin-random. Nine licenses had been issued in 2006. 

Description In the Spheripol process, homopolymer and random copolymer polymerization takes place in liquid propylene within a loop tubular reactor (1). Heterophasic impact copolymerization is done by adding a gas-phase reactor (3) operated in series. Removal of catalyst residue and amorphous polymer is not required. Unreacted monomer is flashed in a two-stage pressure system (2, 4) and recycled back to the reactors. This improves yield and minimizes energy... 

Commercial plants Sixty-three Spheripol process plants with a total capacity of more than 11 million tpy are in operation worldwide. An additional 13 plants are under engineering design or construction. Total licensed capacity exceeds 13.5 MMtpy. Single-line ranges from 40,000 to 400,000 tpy. 

Basell Polypropylene Propylene and ethylene Spheripol process produces a range of homopolymers, randomAmpact copolymers 45 1994... 

In PP manufacture, modern bulk (liquid monomer) and gas-phase processes have largely replaced the earlier slurry processes in which polymerization was carried out in hydrocarbon diluent. The most widely adopted process for PP is Basell s Spheripol process.317 Homopolymer production involves a pre-polymerization step at relatively low temperature, followed by polymerization in a loop reactor using liquid propylene random co-polymers are produced by introducing small quantities of ethylene into the feed. The pre-polymerization step gives a pre-polymer particle with the capacity to withstand the reaction peak, which occurs on entering the main loop reactor. The addition of one or two gas-phase reactors for EP co-polymerization makes it possible to produce heterophasic co-polymers containing up to 40% of E/P rubber within the homopolymer matrix. 

The development of the Spheripol process was based on the use of MgCl2-supported Ziegler-Natta catalysts having spherical particle morphology. Further catalyst and process development, including the manufacture and use... 

Refinement of the bulk polymerization reactor and of the gas-phase reactor led to the development of the Spheripol process in 1982 (Figure 17.2). 

The Spheripol process was a significant step change in the polypropylene process, allowing a broadening of product capabilities and a considerable saving in terms of investment costs as well as operating costs. 

The Spheripol process has been very successful in the PP technology market -since 1982, when the first plant was started up in Brindisi, Italy, over 100 plants have come into operation or are under construction worldwide. 

The Spheripol process has been recognized as an environmentally friendly process, being listed in the Polymers BREF, European Commission - IPPC Integrated Pollution Prevention and Control Best Available Techniques in the production of Polymers dated October 2006. 

Despite the success of the Spheripol process, Basell continue research aimed at improving product characteristics, widening the range of grades and developing the next generation of PP technology, the Spherizone process. 

During polymerization, replication of the catalyst shape occurs, and hence spherical PP beads are obtained directly from the reactor, if t he catalyst is spherical. By producing catalysts with a dense, spherical, and uniform particle shape it is thus possible to generate PP particles that, for many applications, can be shipped and used without a granulation or extrusion step to generate the rubs desired by most customers. This concept is already part of the Himont Spheripol process mentioned earlier. 

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