title: Polymerization of ethylene molecules chemisorbed on CrOH+ as a model system of chromium-containing catalyst.
abstract: The reaction process of the production of CrOH(C2H4)2(+) was studied in connection with the ethylene polymerization on a silica-supported chromium oxide catalyst (the Phillips catalyst). Cluster ions CrOH(C2H4)2(+) and CrOH(C4H8)+ were produced by the reactions of CrOH+ with C2H4 (ethylene) and C4H8 (1-butene), respectively, and were allowed to collide with a Xe atom under single collision conditions. The cross section for dissociation of each parent cluster ion was measured as a function of the collision energy (collision-induced dissociation, or CID). It was found that (i) the CID cross section for the production of CrOH+ from CrOH(C2H4)2(+) increases sharply at the threshold energy of 3.16 +/- 0.22 eV and (ii) the CID cross section for the production of CrOH+ and C4H8 from CrOH(C4H8)+ also increases sharply at the threshold energy of 3.26 +/- 0.21 eV. In comparison with the calculations based on a B3LYP hybrid density functional method, it is concluded that two ethylene molecules in CrOH(C2H4)2(+) are polymerized to become 1-butene. The calculation also shows that the dimerization proceeds via CrOH(C2H4)+ (ethylene complex) and CrOH(C2H4)2(+) (ethylene complex), in which the ethylene molecules bind with CrOH+ through a pi-bonding.
authors.affiliation: East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Hanmura
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ichihashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Monoi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Matsuura
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Kondow
mesh_terms: D002384:Catalysis; D002412:Cations / Q000737:chemistry; D017608:Chromium Compounds / Q000737:chemistry*; D019281:Dimerization; D005030:Ethylenes / Q000737:chemistry*; D006900:Hydroxylation; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D002412:Cations; D017608:Chromium Compounds; D005030:Ethylenes; C036216:ethylene