Polymerization and olefins

In 2007, Smolensky and Eisen published a review entitled "Design of organometallic group IV heteroallylic complexes and their catalytic properties for polymerizations and olefin centered transformations.In this article a strong emphasis was placed on various synthetic and catalytic aspects of group IV metal amidinate complexes. It was clearly pointed out that such amidinate... 

The reactions chosen for study in this work were olefin polymerization and olefin disproportionation. Catalysts for the former reaction are, in the majority of cases, metal derivatives of Groups IVB-VIB whereas compounds of molybdenum, tungsten, and rhenium are recognized as catalysts for olefin disproportionation. 

A second indirect alkylation process, InAlk, is also a solid catalyst process (Fig. 18.25).12 29 InAlk combines two commercially proven technologies polymerization and olefin saturation. Isobutylene is reacted with light olefins (C3-C5) in a polymerization reactor. The resulting mixture of iso-olefins is saturated in the hydrogenation reactor. Excess hydrogen is recycled and the product is stabilized to produce a paraffinic gasoline blending stream. Yet, new solid-acid alkylation processes face tech-... 

It was not fully realized until my breakthrough using superacids (vide infra) that, to suppress the deprotonation of alkyl cations to olefins and the subsequent formation of complex mixtures by reactions of olefins with alkyl cations, such as alkylation, oligomerization, polymerization, and cyclization, acids much stronger than those known and used in the past were needed. 

Catalysts used in the polymerization of C-5 diolefins and olefins, and monovinyl aromatic monomers, foUow closely with the systems used in the synthesis of aHphatic resins. Typical catalyst systems are AlCl, AIBr., AlCl —HCl—o-xylene complexes and sludges obtained from the Friedel-Crafts alkylation of benzene. Boron trifluoride and its complexes, as weU as TiCl and SnCl, have been found to result in lower yields and higher oligomer content in C-5 and aromatic modified C-5 polymerizations. 

The conversion of aromatic monomers relative to C-5—C-6 linear diolefins and olefins in cationic polymerizations may not be proportional to the feedblend composition, resulting in higher resin aromaticity as determined by nmr and ir measurements (43). This can be attributed to the differing reactivity ratios of aromatic and aHphatic monomers under specific Lewis acid catalysis. Intentional blocking of hydrocarbon resins into aromatic and aHphatic regions may be accomplished by sequential cationic polymerization employing multiple reactors and standard polymerization conditions (45). 

Chemical Properties. Higher a-olefins are exceedingly reactive because their double bond provides the reactive site for catalytic activation as well as numerous radical and ionic reactions. These olefins also participate in additional reactions, such as oxidations, hydrogenation, double-bond isomerization, complex formation with transition-metal derivatives, polymerization, and copolymerization with other olefins in the presence of Ziegler-Natta, metallocene, and cationic catalysts. All olefins readily form peroxides by exposure to air. 

By-products include ozonides (17). Other peroxidic products including polymeric peroxides and polymeric ozonides can form, depending on reaction conditions, solvent, and olefin used. A variety of cycHc diperoxides (4) have been obtained by ozonolysis of olefins. Both cis- and... 

A mixture of (C H ) , TiCl, and AlCl is useful for polymerizing C —olefins (85). The dimerization of propylene is accompHshed by using catalysts such as Ni(PR2)4 (86). Alkylphosphines such as / fZ-butylphosphine [2501-94-2] have been proposed as a substitute for high purity phosphine in the production of the semiconductor gallium phosphide (87). 

Organic Reagents. Amine oxides are used ia synthetic organic chemistry ia the preparation of olefins, or phase-transfer catalysts (47), ia alkoxylation reactions (48), ia polymerization, and as oxidizing agents (49,50). 

AUylamines are somewhat unique in that both amine and olefin functionahties are available. This allows the aHylamines to find uses in many areas where the simpler aLkylamines are not suitable, eg, taking advantage of the double bond to form polymeric ammonium salts used as flocculating agents (see... 

Specialty sulfonic acid-based surfactants make up a rather large portion of surfactant production in the United States. Approximately 136,000 metric tons of specialty sulfonic acid-based surfactants were produced in 1992, which included alpha-olefin sulfonates, sulfobetaines, sulfosuccinates, and alkyl diphenyl ether disulfonates (64). These materials found use in the areas of household cleaning products, cosmetics (qv), toiletries, emulsion polymerization, and agricultural chemical manufacture. 

Titanium Trichloride. Titanium trichloride [7705-07-9] exists in four different soHd polymorphs that have been much studied because of the importance of TiCl as a catalyst for the stereospecific polymerization of olefins (120,124). The a-, y-, and 5-forms are all violet and have close-packed layers of chlorines. The titaniums occupy the octahedral interstices between the layers. The three forms differ in the arrangement of the titaniums among the available octahedral sites. In a-TiCl, the chlorine sheets are hexagonaHy close-packed in y-TiCl, they are cubic close-packed. The brown P-form does not have a layer stmcture but, instead, consists of linear strands of titaniums, where each titanium is coordinated by three chlorines that act as a bridge to the next Ti The stmctural parameters are as follows ... 

Organic titanates perform three important functions for a variety of iadustrial appHcations. These are (/) catalysis, especially polyesterification and olefin polymerization (2) polymer cross-linking to enhance performance properties and (J) Surface modification for adhesion, lubricity, or pigment dispersion. 

The exopolyhedral metaHacarborane complex Ti(C2B2QH22)4, which is prepared by the reaction of TiCl and 1-Li-1,2-C2B2QH22, has also been reported to be an active heterogeneous catalyst for the polymerization of olefins when supported on alumina and in the presence of (C2H3)2A1C1 co-catalyst (230). 

The Phillips-type catalyst can be used in solution polymerization, slurry polymerization, and gas-phase polymerization to produce both high density polyethylene homopolymers and copolymers with olefins such as 1-butene and 1-hexene. The less crystalline copolymers satisfy needs for materials with more suitable properties for certain uses that require greater toughness and flexibiUty, especially at low temperatures. 

Polymerization of olefins such as styrene is promoted by acid or base or sodium catalysts, and polyethylene is made with homogeneous peroxides. Condensation polymerization is catalyzed by acid-type catalysts such as metal oxides and sulfonic acids. Addition polymerization is used mainly for olefins, diolefins, and some carbonyl compounds. For these processes, initiators are coordination compounds such as Ziegler-type catalysts, of which halides of transition metals Ti, V, Mo, and W are important examples. 

Catalysts developed in the titanium-aluminum alkyl family are highly reactive and stereoselective. Very small amounts of the catalyst are needed to achieve polymerization (one gram catalyst/300,000 grams polymer). Consequently, the catalyst entrained in the polymer is very small, and the catalyst removal step is eliminated in many new processes. Amoco has introduced a new gas-phase process called absolute gas-phase in which polymerization of olefins (ethylene, propylene) occurs in the total absence of inert solvents such as liquefied propylene in the reactor. Titanium residues resulting from the catalyst are less than 1 ppm, and aluminum residues are less than those from previous catalysts used in this application. 

One of the drawbacks of thermal cracking in an FCC is that a high percentage of the olefins formed during intermediate reactions polymerize and condense directly to coke. 

Mejzlik, J., Lesna, M. and Kratochvila, J. Determination of the Number of Active Centers in Ziegler-Natta Polymerizations of Olefins. Vol. 81, pp. 83 — 120. 

Kennedy, J. P. and Gillham, J. K. Cationic Polymerization of Olefins with Alkylaluminium Initators. Vol. 10, pp. 1-33. 

The study of catalytic polymerization of olefins performed up to the present time is certain to hold a particular influence over the progress of the concepts of the coordination mechanism of heterogeneous catalysis. With such an approach the elementary acts of catalytic reaction are considered to proceed in the coordination sphere of one ion of the transition element and, to a first approximation, the collective features of solids are not taken into account. It is not surprising that polymerization by Ziegler-Natta catalysts is often considered together with the processes of homogeneous catalysis. 

V. I. Komarewsky and J. R. Coley Polymerization of Olefins from Cracked Gases... 

Pi and Sigma Transition Metal Carbon Compounds as Catalysts for the Polymerization of Vinyl Monomers and Olefins... 

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