The review discusses chemical mechanisms of most important reactions that take place in the course catalytic cracking alkenes and alkanes over solid acidic catalysts. main subject is mechanism principal step, fission C─C bonds aliphatic hydrocarbons. via carbenium ion intermediates (with complications caused by oligomerization reactions) well established. In contrast, bond still a controversial subject. compares merits difficulties different proposed literature: several carbenium-ion...

Kinetics of ethylene homopolymerization reactions and ethylene/1-hexene copolymerization using a supported Ziegler–Natta catalyst was carried out over broad range reaction conditions. The kinetic data were analyzed concept multicenter catalysis with different centers that respond differently to changes in parameters. contains five types active differ the molecular weights material they produce their ability. In reactions, each center has high order respect concentration, close second order....

The mechanism of (PCP)Ir-catalyzed transfer-dehydrogenation has been elucidated for the prototypical substrate/acceptor couple, COA/TBE, at 55 degrees C (COA = cyclooctane; TBE tert-butylethylene). catalytic cycle may be viewed as sum two reactions: (i) hydrogenation by (PCP)IrH2 and C-H addition a second mole to give (PCP)IrH(tert-butylvinyl), (ii) dehydrogenation COA (PCP)IrH(tert-butylvinyl) (PCP)IrH2, COE, TBE. These stoichiometric reactions have observed independently their kinetics...

Abstract The GPC method is used widely to measure molecular weights of linear polymers. High‐quality data contains detailed information on many aspects the polymer's weight distribution (MWD). This can be extracted from using computer analysis. Equations have been derived for two simplest MWD functions in coordinates: Flory function (one growing polymer chain produces one molecule), and case when radicals combine into molecule. equations were analyze classes first class includes polymers...

Abstract High activity ethylene polymerization catalysts have been prepared by the interaction of ethylmagnesium chloride in tetrahydrofuran with high surface area silica, followed reaction excess titanium tetrachloride heptane. The were tested ethylene—hexene copolymerization reactions presence AlEt 3 at 80°C. For comparison purposes, properties a similar catalyst without silica also evaluated. Preparative conditions identified which provide that possess reactivity towards 1‐hexane. and...

Abstract Combinations of dialkylaluminum chlorides and dialkylmagnesium compounds, when used at molar [AlR 2 Cl]:[MgR ] ratios ≥ 2, act as universal cocatalysts for all three presently known types alkene polymerization catalysts—Ziegler–Natta, metallocene, post‐metallocene. When these are with supported Ti‐based Ziegler–Natta catalysts, they produce catalyst systems which 1.5–2 times more active than the utilizing AlR 3 compounds cocatalysts. Cl/MgR various metallocene complexes...

We report the first example of catalytic dehydrogenation aliphatic polyolefins to give partially unsaturated hydrocarbon polymers.

Abstract Synthesis of low‐density polyethylene, that is, a density less than 0.925 g/cm 3 , has traditionally been accomplished by the use free‐radical initiators at high ethylene pressures or an alpha olefin comonomer such as 1‐butene lower pressures. We investigated alternative route to branched, polyethylene with single monomer, ethylene, feed in conjunction multicomponent catalyst systems capable situ dimerization and subsequent copolymerization produce polyethylene. This article...

Abstract This article discusses the similarities and differences between active centers in propylene ethylene polymerization reactions over same Ti‐based catalysts. These correlations were examined by comparing kinetics of both monomers two different catalyst systems, δ‐TiCl 3 ‐AlEt TiCl 4 /DBP/MgCl 2 /PhSi(OEt) , molecular weight distributions respective polymers, consecutive ethylene/propylene propylene/ethylene homopolymerization reactions, examining IR spectra “impact‐resistant”...

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTA New Cocatalyst for Metallocene Complexes in Olefin PolymerizationYury V. Kissin, Thomas E. Nowlin, Robert I. Mink, and Anita J. BrandoliniView Author Information Edison Research Center, Mobil Chemical Company, P.O. Box 3029, Edison, Jersey 08818-3029 Cite this: Macromolecules 2000, 33, 12, 4599–4601Publication Date (Web):May 26, 2000Publication History Received7 December 1999Published online26 May 2000Published inissue 1 June...

Abstract A new approach to detailed Tref analysis of ethylene/α‐olefin copolymers prepared with multi‐center polymerization catalysts is developed. It based on resolution complex curves into elemental components described the Lorentz distribution function. This was applied study a series ethylene/1‐butene supported Ti‐based catalyst. The showed that copolymers, which, average, contain from 6.5 3.5 mol % 1‐butene, consist seven discrete different compositions, ranging completely amorphous...

Journal Article Gas Chromatographic Analysis of Polymethyl-Substituted Alkanes Get access Y.V. Kissin, Kissin Gulf Research and Development Company, Pittsburgh, Pennsylvania 15230 Search for other works by this author on: Oxford Academic PubMed Google Scholar G.P. Feulmer, Feulmer W.B. Payne Science, Volume 24, Issue 4, April 1986, Pages 164–169, https://doi.org/10.1093/chromsci/24.4.164 Published: 01 1986 history Revision received: 13 February 1985 Received: November

Abstract A previously developed kinetic scheme for ethylene polymerization reactions with heterogeneous Ziegler–Natta catalysts (see Y. V. Kissin, R. I. Mink, & T. E. Nowlin, J Polym Sci Part A: Chem 1999, 37, 4255 and A. J. Brandolini, 4273, 4281) states that the have several types of active centers different activities stabilities, produce polymer materials, respond differently to reaction conditions. Each type center produces a single component (Flory component), material uniform...

Abstract Ethylene polymerization kinetics was examined using a supported Ti‐based catalyst activated by AlEt 3 . A computer‐based technique for deconvoluting the GPC curves into constituent Flory components developed. The kinetic analysis showed that contains five populations of active centers. Each population has different formation and deactivation rates, produces polymers molecular weights is differently affected hydrogen.

Abstract 2,6‐Bis(imino)pyridyl complexes of Fe and Co in combination with methylalumoxane form very active homogeneous catalytic systems for polymerization ethylene. GPC analysis the polymers prepared indicates that produce single‐center catalysts whereas numerous types centers. Different centers latter catalyst respond differently to reaction conditions such as duration, [MAO]:[Fe] ratio, ethylene concentration, etc. The article examines effects variables on performance both proposes an...

Abstract An experimental technique, crystallization analysis fractionation (Crystaf), is used to analyze compositional uniformity of ethylene/α‐olefin copolymers and isotactic polypropylene. A computerized method for quantifying Crystaf data developed based on resolution curves into their elemental components, with each component representing a fraction the polymer same degree chain imperfection. This gives three parameters characterizing crystallizable material: (a) number compositionally...

Abstract The hydrogen activation effect in propylene polymerization reactions with Ti‐based Ziegler–Natta catalysts is usually explained by hydrogenolysis of dormant active centers formed after secondary insertion a molecule into the growing polymer chain. This article proposes different mechanism for due to Ti iso ‐C 3 H 7 group. group can be two reactions: (1) TiH bond (which generated β‐hydrogen elimination chain or transfer hydrogen), and (2) if coordinated Ti atom orientation....