Reference

The state of chromium in an ethylene-polymerization catalyst prepared by deposition of bis(triphenylsilyl) chromate on silica gel

The state of chromium in an ethylene-polymerization catalyst prepared by deposition of bis(triphenylsilyl) chromate on silica gel. Maksimov, N. G.; Lesnikova, N. P.; Paukstis, E.; Shinkarenko, V. G.; Zakharov, V. A.; Anufrienko, V. F.; Ermakov, Yu. I. (Inst. Katal., Novosibirsk, USSR). Kompleksn. Metalloorg. Katal. Polim. Olefinov, 8, 3-8 (Russian) 1983. CODEN: KMKODJ. ISSN: 0203-8722. DOCUMENT TYPE: Journal CA Section: 35 (Chemistry of Synthetic High Polymers) Section cross-reference(s): 67 The presence of clusters of Cr ions and considerable heterogeneity in Cr compds. were detected by ESR and UV spectroscopy on the silica surface of the title catalysts prepd. by deposition of (Ph3Si)2CrO4 [1624-02-8] on silica gel and subsequent treatment with Et3Al [97-93-8] and/or other activation methods. The identified paramagnetic ions did not participate in polymn. of ethylene. Active centers of the catalyst included low-valent Cr compds. unidentified in the ESR spectra and present in the clusters.

Polymerization catalyst

Polymerization catalyst. Levine, Isaac Jacob; Karol, Frederick John (Union Carbide Corp., USA). Ger. Offen. DE 2802517 27 Jul 1978, 24 pp. (German). (Germany). CODEN: GWXXBX. CLASS: IC: C08F010-02. PRIORITY: US 77-761213 21 Jan 1977. DOCUMENT TYPE: Patent CA Section: 35 (Synthetic High Polymers) Ethylene (I) is polymd. or copolymd. with C3-6 olefins in the presence of silyl chromate (R3SiO)2CrO2 (R = C1-14 hydrocarbyl) catalysts supported on Al- and Ti-contg. silicic acid or silica which has been heat-treated at 500-1000°. Thus, 20 g Polypor silicic acid was treated with a soln. of 1.50 g Al(NO3)3.9H2O in 150 cm3 water, sepd., and dried. A suspension of 9.3 g of the product in 100 cm3 pentane was treated with 2.8 g tetra-iso-Pr titanate, freed of solvent, and heated 17 h in O at 810°, giving a catalyst support (A) with Al and Ti contents (calcd. as oxides) 0.5 and 7.5%, resp. A catalyst slurry prepd. by mixing 1.0 g A and 0.030 g bis(triphenylsilyl) chromate [1624-02-8] with 50 cm3 hexane and stirring 1 h at room temp. was then mixed with 500 cm3 hexane and 40 cm3 1-hexene and used in the polymn. of I at 14 atm. gage and 86° for 40 min, giving 136 g ethylene-1-hexene copolymer [25213-02-9] with melt index 2.81 dg/min, flow index 92.1 dg/min, and d. 0.932 g/cm3. A control polymn. in the presence of a catalyst on a support contg. only Al gave a product with melt index 0.28 dg/min, flow index 11.7 dg/min, and d. 0.939 g/cm3.