Gas-phase polymerization of propylene

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. 

The kinetic models for the gas phase polymerization of propylene in semibatch and continuous backmix reactors are based on the respective proven models for hexane slurry polymerization ( ). They are also very similar to the models for bulk polymerization. The primary difference between them lies in the substitution of the appropriate gas phase correlations and parameters for those pertaining to the liquid phase. 

Table II summarizes the yields obtained from the CONGAS computer output variable study of the gas phase polymerization of propylene. The reactor is assumed to be a perfect backmix type. The base case for this comparison corresponds to the most active BASF TiC 3 operated at almost the same conditions used by Wisseroth, 80 C and 400 psig. Agitation speed is assumed to have no effect on yield provided there is sufficient mixing. The variable study is divided into two parts for discussion catalyst parameters and reactor conditions. The catalyst is characterized by kg , X, and d7. Percent solubles is not considered because there is presently so little kinetic data to describe this. The reactor conditions chosen for study are those that have some significant effect on the kinetics temperature, pressure, and gas composition.

When polymerization is carried out in a solvent, and a solid catalyst is employed, the gaseous poison is distributed among gaseous, liquid and solid phases and the equilibration may take some time. The adsorbed amount of the poison usually forms a minor part of the injected quantity. Thus, its consumption by side processes makes the determination of the adsorbed amount of the poison less certain. A more favourable case is the gas phase polymerization, where a more suitable (much lower) ratio of the poison amount in the gaseous and solid phases can be achieved. Doi et al.102) document a fast and quantitative insertion of CO into transition metal-carbon bonds on the basis of the GC analysis in the gas phase polymerization of propylene. These data may require an additional study of other potential reactions of CO in the system. 

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]. 

Fig. 8 Kinetic curves of propene polymerization with MgCl2/Di/TiCl4/D2-AlEt3, 70°C. Open circles) polymerization of propylene in n-heptane pcsHs = 2.5 atm, Kh = 0.325 mol/(l atm) closed circles) polymerization in liquid propene [CaHg] = 10.5 mol/L open squares) gas-phase polymerization of propylene, pcjHs = 2.5 atm, = 0.13mol/(l atm) closedtriangles)gas-...

More recently, gas-phase polymerizations of propylene were introduced. The technology is similar to the gas-phase technology in ethylene polymerizations described in Section 5.1. 

Later bulk polymerization processes were developed where liquid propylene was either used as the only diluent in a loop reactor or permitted to boil out to remove the heat of reaction. The second was done in stirred vessels with vapor space at the top. More recently, gas-phase polymerizations of propylene were introduced. The technology is similar to the gas-phase technology in ethylene polymerizations [15] described in Sect. 6.1. 

Reddy, C. S. and Das, C. K. 2006. In situ polypropylene nanocomposites Gas-phase polymerization of propylene in the presence of nanofillers using nanosilica-supported-zirconocene catalyst. Journal of Macromolecular Science A Pure and Applied Chemistry 43 1365-1378. 

Gas Phase Polymerization of Propylene with htgCk Supported Catalysts 37... 

The gas phase polymerization of propylene on the surface of oC-TiCl j crystals activated by AlMe has been investigated by Guttman and Guillet by means of electron microscopy, (11,12). By assuming that each fibril was attached to only one active centre values for C were determined. However the values obtained were several orders of magnitude less than those obtained by other methods, a discrepancy diich may be due to active centre clustering, or to the some diat artificial conditions of these imaginative experiments (i.e. gas phase). 

Figure 6. Simulation of a continuous backmix reactor (propylene gas phase polymerization—kg° = 0,0249 cm/sec, X = 9.68 hr, 400 psia reactor gas composition—99% CsH6,1% inerts)...

We have a choice of four major polymerization techniques by which to manufacture polypropylene using Ziegler-Natta catalysts slurry, liquid propylene, solution, and gas phase. Regardless of which technique is employed, all polymerization plants must accomplish the same basic goals they must... 

Metallocenes are homogeneous catalysts that are often soluble in organic solvents. Therefore, polymerization can occur via a solution process with a non-polar diluent dissolving the propylene gas, the catalyst, and the co-catalyst system. They can also be adsorbed onto an inert substrate which acts as part of the fluidized bed for gas phase polymerization processes. 

We have reported a gas phase and solution phase study comparing mono-and dinuclear CF" complexes as catalysts for the ring opening polymerization of propylene oxide. (Adapted from Schon et al., 2004)... 

Fig. 1. The reaction-kinetic relationships between the experimental parameters (duration of experiment, quantities, catalyst components, average molecular mass, solubility in n-heptane, and catalyst yield) for propylene, gas-phase polymerization. Experiment in a I-liter autoclave. Catalyst TiCI3-AlEt3, room temperature, 1 bar, time (r) in hours. From Wisseroth (43).

For the polymerization of ethylene and propylene large-scale gas-phase processes are well established. The implementation of gas-phase technology to the production of sticky polymers such as the ethylene/propylene-based rubbers EPM and EPDM was pioneered by UCC [519]. In a series of patents, UCC describes various approaches to overcome the inherent stickiness of rubber granules in the gas-phase polymerization. These approaches include the use of anti-agglomerants such as carbon black, silica, inorganic salts or appropriate catalyst supports and antistatic voltage etc. [520-535]. The addition of fluidization or anti-agglomeration aids is described by Zollner et al., silica is used in particular [536,537]. 

Propylene, catalyst, cocatalyst, donor, hydrogen, and comonomer (for random copolymers) are fed into the loop reactor propylene is used as the polymerization medium (bulk polymerization). The loop reactor is designed for supercritical conditions and operates at 80-100°C and 50-60 bar. The propylene/polymer mixture exits the loop reactor and is sent to a fluidized-bed, gas-phase reactor, where propylene is consumed in polymerization. This reactor operates at 80-100°C and 25-35 bar. Fresh propylene, hydrogen and comonomer (in case of random copolymers) are fed into the reactor. After removing hydrocarbon residuals, the polymer powder is transferred to extrusion. 

Lummus Novolen Technology Polypropylene homopolymer, random copolymers, impact copolymers, including Metallocene PP Propylene (and ethylene for production of copolymers) Polymerization of propylene in one or two gas-phase reactors stirred by helical agitators to produce a wide range of products 27 2010... 

Finely divided particles of MAO are precipitated from a toluene solution by addition of /3-decane followed by evaporation. Suspension of these particles in decane followed by reaction with toluene solutions of Cp 2ZrCl2 (Cp 2 = Cp2 or Et(Ind)2 ) affords a solid catalyst which can be used in solution or gas-phase polymerization processes using ethylene or propylene as the monomers. Solids also separate from a toluene solution of MAO on addition of an equal volume of hexane or isobutane.Insoluble gels in toluene solutions of MAO, ordinarily a nuisance, can be filtered off, resuspended in aliphatic hydrocarbons, and reacted with metallocene dichlorides to produce active catalysts for olefin polymerization without reactor fouling. 

Different diluent-phase polypropylenes showed similar behaviour but the proportion of affected powder particles varies. Clearly these local variations would tend to disappear in the processing of the polymer to produce stabilised pellets. Variations in oxidation rates of individual particles were also found with gas-phase polymerized propylenes (Figure 11), in this case the catalyst residues could not be seen. 

Crozier PA, Oleshko VP, Westwood AD, Cantrell RD. In situ environmental transmission electron microscopy of gas phase Ziegler-Natta catalytic polymerization of propylene. Presented at Institute of Physics Conference Series 2001. 

Polymerization of vinyl chloride Polyacrylates and polymetiiacrylates Butadiene, isopreal and tiien copolymers Cationic copolymerization of isobutene-isoprene with slurry AICI3 as tiie initiator and metiiyl chloride as diluent AICI3 slurry polymerization of propylene in tiie presence of transition metiiyl catalyst and excess monomer as a diluent Fluidized bed reactor is used in tiie gas phase poljmierization a powdered polymer is produced in a gaseous monomer-low pressure poljmierization of ethylene (HDPE) and propylene... 

For gas-phase or liquid propylene bulk reactors, the bulk monomer concentration in the reactor must be converted to concentration in the polymer phase surrounding the active sites with a thermodynamic relationship. Generally, a simple partition coefficient such as the one used in Equation 2.136a is used. For diluent slurry reactors, where the monomer is introduced in the gas phase, a partition coefficient such as Herny s law constant must also be used to calculate the concentration of monomer in the diluent which, in turn, is used to estimate the concentration of monomer in the polymer phase surrounding the active sites. Evidently, more sophisticated thermodynamic relationships relating the concentration of monomer in the gas phase, diluent and polymer can be used but, from a practical point of view, are only justified when the polymerization kinetic constants are very well known. Similar considerations apply to calculate the concentrations of comonomers, hydrogen and any other reactant in the system. 

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