Ethene high linearity

Solid catalysts for the metathesis reaction are mainly transition metal oxides, carbonyls, or sulfides deposited on high surface area supports (oxides and phosphates). After activation, a wide variety of solid catalysts is effective, for the metathesis of alkenes. Table I (1, 34 38) gives a survey of the more efficient catalysts which have been reported to convert propene into ethene and linear butenes. The most active ones contain rhenium, molybdenum, or tungsten. An outstanding catalyst is rhenium oxide on alumina, which is active under very mild conditions, viz. room temperature and atmospheric pressure, yielding exclusively the primary metathesis products. 

In the laboratories of Natta in Milan it was found that the Ziegler catalysts could polymerize (besides ethene) propene, styrene, and several a-olefins to high linear polymers. These polymers appeared crystalline when examined by X-ray diffraction techniques and were able to give oriented fibers. In less than one year since the preparation of the first polymer of propene, Natta was able to communicate, in the meeting of the Accademia dei Lincei of December 1954 in Rome, that a new chapter had been disclosed in the field of macromolecular chemistry, due to the discovery of processes to obtain polymers with an extraordinary regularity in their structure in terms of both chemical constitution and configuration of the successive monomeric units along the chain of each macromolecule. 

Mw/M = 2, highly linear Copolymerization random distribution, LLDPE co-monomers propene, 1-butene, 1-octene Elastomers, Terpolymers of Ethene, Propene and Diene low transition metal concentration in the polymer, narrow molecular weight distribution Polymerization to ... 

Cobalt carbonyls are the oldest catalysts for hydroformylation and they have been used in industry for many years. They are used either as unmodified carbonyls, or modified with alkylphosphines (Shell process). For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc). For higher alkenes, cobalt is still the catalyst of choice. Internal alkenes can be used as the substrate as cobalt has a propensity for causing isomerization under a pressure of CO and high preference for the formation of linear aldehydes. Recently a new process was introduced for the hydroformylation of ethene oxide using a cobalt catalyst modified with a diphosphine. In the following we will focus on relevant complexes that have been identified and recently reported reactions of interest. 

In MeOH the hydride reacts with higher a-olefins, propene, 1-hexene and 1-hexadecene with formation of only the linear insertion product, probably for steric reasons. In all the insertion products, the alkyl ligand presents the /f-agoslic interaction. At room temperature, the insertion of ethene is quantitative whereas with propene an appreciable amount of the hydride is present, with 1-hexene the hydride prevails, with 1-hexadecene only the hydride is present. The fact that the position of the insertion equilibrium strongly depends on the chain length of the alkyl substituent is probably connected with the high steric hindrance of the ligand [115]. 

The higher alkene feed (C10-14) for the production of detergent alcohols is either a product from the wax-cracker (terminal and internal alkenes) or the byproduct of the ethene oligomerisation process (internal alkenes). In the near future a feed from high-temperature Fischer-Tropsch may be added to this. The desired aldehyde (or alcohol) product is the linear one and the cobalt catalyst must therefore perform several functions ... 

Enormous commerical applications flowed from the revolution initiated by Ziegler and Natta. These include high-density and linear low-density polyethylenes (HDPE, LLDE), polypropene, ethene-propene co- and terpolymers, and polymers from 1,3-dienes (Sec. 8-10). The annual United States production of these polymers exceeded 40 billion pounds in 2000 the global production was about 3-3.5 times the U.S. production. Ziegler-Natta chemistry accounts for the production of one-third of all polymers. 

Butene is used in the plastics industry to make both homopolymers and copolymers. Polybutylene (1-polybutene), polymerized from 1-butene, is a plastic with high tensile strength and other mechanical properties that makes it a tough, strong plastic. High-density polyethylenes and linear low-density polyethylenes are produced through co-polymerization by incorporating butene as a comonomer with ethene. Similarly, butene is used with propene to produce different types of polypropylenes. 

In only a few cases have the spectra of adsorbed ethene been explored much above room temperature, in contrast to the situation on single-crystal metals where measurements up to 600 K. are commonplace. The metal-dependent temperature for some surface transformations are summarized in Table VIII, in comparison with similar reactions of the linear butenes (Section VI.C.2.C). At sufficiently high temperatures, e.g., ca. 430 K on Ni/Si02 (32) or at ca. 500 K on Pt/Si02 (240), the CC bond of ethylidyne is broken to give CH4. 

The regioselectivity (branched linear) for the addition of trichlorosilane to 1-alke-nes is in a range of 80 20 93 7 [67], In the case of 1-aryl-1-alkenes such as (2-chlorophenyl)ethene (124), l-pheny)prop-l-ene (125), and indene, the regioselectivity reaches as high as 99 1, although the enantioselectivity for the formation of the correspond-... 

For the polymerization of ethene chiral, metallocenes are not necessary but high activity and linear polymers are wanted. Table 3 compares some metallocene catalysts for the polymerization of ethene. 

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