Novolen process

Gas-phase polymerization of propylene was pioneered by BASF, who developed the Novolen process which uses stirred-bed reactors (Fig. 8) (125). Unreacted monomer is condensed and recycled to the polymerizer, providing additional removal of the heat of reaction. As in the early Hquid-phase systems, post-reactor treatment of the polymer is required to remove catalyst residues (126). The high content of atactic polymer in the final product limits its usefiilness in many markets. 

Novolen process -for polypropylene [OLEFIN POLYMERS - POLYPROPYLENE] (Vol 17)... 

Novolen Process (Figure 7) With this technology, which comprises two vertical stirred gas-phase reactors in series, homopolymers as well as impact and random copolymers are produced. The first reactor operates at 80°C and 20-35 bar monomer pressure and is used exclusively for the homopolymerization of propylene. Propylene is injected as a liquid and cools the exothermic polymerization by its... 

Figure 7 Novolen process a) first reactor, b) second reactor for impact copolymers, c) compressor, d) condensation, e) pump,f) filter, g) cyclone, h) deactivation and purge.

Amoco-Chisso Process This process resembles the Novolen process except that the two reactors connected in series are stirred horizontally with blades and operated at 90°C and 20 bar. Polymers produced with the Amoco-Chisso technology show high uniformity, as particle residence time distribution in the reactor is particularly narrow. 

Commercial plants The capacities range from 60,000 to 450,000 metric tpy for single lines. Over 50 production lines are in operation, engineering or under construction. The total licensed capacity worldwide for the Novolen process is in excess of 8 million tons. 

The first gas-phase polymerization was first commercialized in Wesseling, Germany by ROW Co. in a joint venture with BASF and Shell companies in 1969. This facility employed the Novolen process for propylene polymerization in the gas phase. UCC and Sumitomo companies later developed fluidized-bed processes for the gas-phase polymerization of propylene. The advantages of this process are its high-effidency catalysis, elimination of residual removal, and elimination of evaporation or centrifugal separation. Its polymer product can be used in almost all applications [12,13,71,72]. 

Continuous stirred-tank reactors (CSTRs) are used for large productions of a reduced number of polymer grades. Coordination catalysts are used in the production of LLDPE by solution polymerization (Dowlex, DSM Compact process [29]), of HDPE in slurry (Mitsui CX-process [30]) and of polypropylene in stirred bed gas phase reactors (BP process [22], Novolen process [31]). LDPE and ethylene-vinyl acetate copolymers (EVA) are produced by free-radical polymerization in bulk in a continuous autoclave reactor [30]. A substantial fraction of the SBR used for tires is produced by coagulating the SBR latex produced by emulsion polymerization in a battery of about 10 CSTRs in series [32]. The CSTRs are characterized by a broad residence time distribution, which affects to product properties. For example, latexes with narrow particle size distribution cannot be produced in CSTRs. 

Dowlex DSM Compact process Mitsui CX-process Novolen process Innovene process (horizontal stirred bed reactor)... 

The Novolen process [78], now licensed by Novolen Technology Holdings (NTH), uses the vertically stirred reactor for propylene polymerization. The basic process is similar to the Unipol process but with a simpler polymer discharge system. Novolen claims this process requires the lowest capital investment of its class and has low operating costs. 

In a sequence of gas phase reactors, (see the chapter on Ziegler catalysis) for the Novolen process of BASF AG [21], EPM rubber can be incorporated into PP during the second stage. This reactor blend can be tailored to improve low-temperature impact resistance of PP. Typical PP-based reactor blends contain high rubber contents and exploit the benefits of modern supported catalysts. In comparison to PP extruder... 

Metallocene catalysts need to be supported to be used in gas phase reactors, such as Union Carbide s fluidized-bed Unipol process, or BASF s stined-bed Novolen process. For these processes, it is necessary to have a free flowing catalyst powder which will form polymer particles with adequate size distribution, avoiding the formation of fine powder or particle agglomerates. In other words, good replication of the catalyst particle size distribution is essential for the efficient performance of these reactors. 

Novolen A process for making polypropylene in the gas-phase, using a vertical stirred-bed reactor. Developed by BASF and engineered by Uhde. Eight plants had been licensed as of 1985. A metallocene-catalyzed version was introduced in 1996. The name is used also for the product. 

Gaseous polymerization of polyolefins is carried out in fluidized-hed reactors. The conversion per pass is kept rather low (order of 2%) so that the heat of polymerization is removed via convection by the unconverted reactants, which are cooled externally and recycled to the reactor. In some cases, an inert liquid is added to the feed so that its evaporation helps remove some of the heat of the reaction. The Unipol process is one of the most common processes used to carry out this gaseous polymerization. Other processes for producing polyolefins include Hypol, Novolen, Catalloy and Spheriline. 

MeBeInd)2ZrCl2-supported catalyst and the Novolen-BASF process. This catalyst can produce PP with high molecular weight even at elevated temperatures. The pol)nner particles replicate well the size distribution of the catalyst particles. This catalyst can produce PP with new properties, such as low extractables for food wrapping and medical applications, which is a consequence of the uniform stereoregularity of pol)maers produced with a single site-type catalyst. 

Keywords metallocene catalyst, Ziegler-Natta catalyst, olefin polymerization, polyolefins, homogeneous catalysts, supported catalysts, stereoregularity, molecular weight distribution (MWD), chemical composition distribution, Unipol , Novolen , stereoselectivity, single site catalyst, multiple site catalyst, gas phase process, slurry process, homopolymerization, copolymerization. 

Figure 19 Novolen gas-phase process (courtesy of BASF AG).

In gas phase processes, gaseous propylene comes into contact with the solid catalyst which is intimately dispersed in dry pol5aner powder. Industry uses two different methods of carrying out this reaction depending on the chosen method of heat removal. The Unipol PP process uses a modification of the Unipol polyethylene fluidised bed system. The Novolen PP process and Innovene PP process use mechanically agitated dry powder beds with evaporative cooling in vertical and horizontal reactors, respectively. Unipol PP was originally developed by Union Carbide and Shell, the Novolen PP process by BASF and the Innovene PP process by Amoco. 

FIG. 23 Supported metallocene catalyst for the Novolen [BASF] process. (From Ref. 1.)... 

The core for the production of metallocene-based polymers is the Novolen Gas Phase Process [64] which combines metallocene drop-in technology (Fig. 40). The core of the process is one or two vertical stirred reactors in series. The process can manufacture... 

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