Polypropylene reactors

An interesting article by O Shea and coworkers described the construction and use of a parallel polypropylene reactor comprising cylindrical, expandable reaction vessels with porous frits at the bottom [20], During the reaction, the piston of each... 

A recent article describes the construction and use of a parallel polypropylene reactor comprising of cylindrical, expandable reaction vessels with porous frits at the bottom (Fig. 7.4)21. This is the first description of reaction vessels for microwave-assisted synthesis that may be useful for carrying out solid-phase synthesis using bottom filtration techniques in conjunction with microwave heating. However, at the time when tins chapter was being written no application of this system for solid-phase synthesis had been reported. 

Shin et al. [90] Octopine Scallop Octopine dehydrogenase (ODH)/ODH-bonded beads were packed into a polypropylene reactor tube/ pyruvate oxidase/in a cellulose triacetate, glutaraldehyde and 1,8-diamino-4-aminomethyl octane membrane Oxygen electrode ... 

As an alternative, tagging strategies have been developed, in which the active molecule can be identified by placing a tag on the same bead. These procedures are rather tedious and, with the exception of radiofrequency tagging of small polypropylene reactors, have not fulfilled expectations. 

Immobilized Liquid Membranes. A pilot plant study of the recovery of ethylene and propylene from a polypropylene reactor off-gas stream was presented by Hughes et al. (23). Aqueous solutions of Ag Ion were Immobilized In the pore structure of commercial reverse osmosis hollow fiber modules. The pilot plant operated at feed pressures of 414-827 kPa, feed flow rates of 1.42-4.25 m /h at STP, and sweep flow rates of 3.79 10" - 0.114 m /h hexane. Permeate streams with propylene concentrations In excess of 98 mole % were observed in pilot plant operation with modules containing 22.3 to 37.2 m membrane area. 

An in-reactor TPO may be defined as a reactor-produced polypropylene copolymer (PP-b-E/P), containing between 22 % and 55 % ethylene-propylene copolymer blocks. Small amounts of other comonomers, such as octene-1 or butene-1, may also be present so as to provide unique functionality. In-reactor propylene block copolymers containing less than 20 % ethylene are fairly hard and are usually classified as impact polypropylenes. Reactor-made polymers containing >50 % ethylene are soft and also have relatively poor elastomeric properties - these are classified as plastomers. 

In-reactor TPOs are made in special polypropylene reactors, and they are designed to be cost- competitive to some extent against the compounded TPOs. 

Consider first the case of two tubular reactors in series, making high-impact polypropylene. Reactor 1 produces isotactic polypropylene, while random ethylene-propylene copolymer is made in Reactor 2. Assuming that both reactors are ideal plug-flow reactors, the residence time of all the polymer particles in each reactor is exactly the same. Consequently, if the distribution of active sites in the... 

Reaction vessel 10 mL disposable polypropylene reactor vials with a filter bottom. 

Although the selectivity of isopropyl alcohol to acetone via vapor-phase dehydrogenation is high, there are a number of by-products that must be removed from the acetone. The hot reactor effluent contains acetone, unconverted isopropyl alcohol, and hydrogen, and may also contain propylene, polypropylene, mesityl oxide, diisopropyl ether, acetaldehyde, propionaldehyde, and many other hydrocarbons and carbon oxides (25,28). 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Catalyst Development. Traditional slurry polypropylene homopolymer processes suffered from formation of excessive amounts of low grade amorphous polymer and catalyst residues. Introduction of catalysts with up to 30-fold higher activity together with better temperature control have almost eliminated these problems (7). Although low reactor volume and available heat-transfer surfaces ultimately limit further productivity increases, these limitations are less restrictive with the introduction of more finely suspended metallocene catalysts and the emergence of industrial gas-phase fluid-bed polymerization processes. 

Erom 1955—1975, the Ziegler-Natta catalyst (91), which is titanium trichloride used in combination with diethylaluminum chloride, was the catalyst system for propylene polymerization. However, its low activity, which is less than 1000 g polymer/g catalyst in most cases, and low selectivity (ca 90% to isotactic polymer) required polypropylene manufacturers to purify the reactor product by washing out spent catalyst residues and removing unwanted atactic polymer by solvent extraction. These operations added significantly to the cost of pre-1980 polypropylene. 

Figure 1 shows part of a solvent phase polypropylene plant. The plant consists of three process lines, denoted A, B, and C. During a risk assessment review, a scenario was identified that involved a release of reactor contents from a location near the west end of the A line. Estimates are needed of the blast overpressures that would occur if the resulting cloud of vapor, mist, and power ignites. 

Figure 12-2. The Union Carbide gas-phase process for producing polypropylene " (1) reactor, (2) centrifugal compressor, (3) heat exchanger, (4) product discharge tank (unreacted gas separated from product), (5) impact reactor, (6) compressor, (7) heat exchanger, (8) discharge tank (copolymer separated from reacted gas).

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.

After 8 h of reaction, the reactor was allowed to cool. A two-layer liquid formed. The top layer was found to contain mostly polypropylene ether triols with about 20% by weight diethylene glycol and 5% by weight toluene diamines. The top layer was purified by vacuum distillation at 2 mm Hg and 200° C to produce 320 g of a light brown liquid residue. This residue (polyols) was used as a replacement for 5% by weight of the Pluracol 535 polyol in the formulation of a flexible polyurethane foam. A flexible foam which had good resiliency and a density of 2.2 Ib/ft3 was obtained. At higher replacement levels, lesser quality foams were obtained. 

Gas phase olefin polymerizations are becoming important as manufacturing processes for high density polyethylene (HOPE) and polypropylene (PP). An understanding of the kinetics of these gas-powder polymerization reactions using a highly active TiCi s catalyst is vital to the careful operation of these processes. Well-proven models for both the hexane slurry process and the bulk process have been published. This article describes an extension of these models to gas phase polymerization in semibatch and continuous backmix reactors. 

The biberty (Fig. 10), a monomode microwave reactor for automated SPPS, was recently introduced by the CEM Corporation [153]. Although this instrument was originally developed for SPPS, it also allows for a broader scale of solid-phase applications. The solid-phase vial is equipped with a polypropylene frit and cap at one end (the entire assembly fitting into the standard 10 mb CEM reaction vessel) to allow the processing of 0.1 to 1.0 mmol quantities of resin attached substrates. An integrated fiber optic probe provides... 

Recently, Murray and Gellman demonstrated that parallel synthesis in inexpensive 96-well polypropylene filter plates with microwave irradiation in a multimode reactor is a simple and effective method for the rapid preparation of j8-peptide hbraries on sohd support in acceptable purities [156]. 

The final output of the reactor is a synthesis gas. The composition will depend on the input. If much polypropylene (PP) and polyethylene (PE) is present, relatively high amounts of ethylene and propylene will be formed. If mainly PVC is present, HCl and CH4... 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

---