Chromium ethoxide

Bis(2,4-pentanedionato)chromium, 3326 Molybdenum hexamethoxide, 2596 Potassium /er/-butoxide, 1650 Potassium ethoxide, 0861 Potassium methoxide, 0450... 

A typical catalyst containing 2.5% of chromium in n-hexane (20 mg 1" ) activated by aluminium diethyl ethoxide (0.3 mg 1" ) gave a yield of 140 g polymer per h at 88—91°C and a monomer pressure of 300 p.s.i.g. The chromocene based catalysts are also of high activity, this being dependent on the conditions of catalyst preparation. Dehydration at 670°C gave the highest yield of polymer. Detailed kinetics were not carried out, but yields of 130—1670 g polymer per mmole Cr per 100 p.s.i. ethylene per h at 60°C were reported. 

Figure 5.5 Compounds used to produce supported chromium catalysts developed by Union Carbide for use in gas phase processes for LLDPE and HOPE. Catalysts must be supported, usually on silica, for optimal performance. Chromocene catalyst is used without a cocatalyst BTSC uses diethylaluminum ethoxide as cocatalyst.

The reflectance spectra of d chromium(m) methoxide and ethoxide " agreed with ligand field predictions for an octahedral d ion with 10 Dq 17 000 cm (Table 2.22). 

A key attribute of the Bis(triphenylsilyl)chromate catalyst deposited into silica is that this catalyst does not require a high temperatme activation (oxidation) step in the catalyst preparation. Consequently, this catalyst is activated in the polymerization reactor by the ethylene, which results in an induction time similar to the Phillips catalyst before the onset of polymerization. However, because the Bis(triphenylsilyl)chromate catalyst on silica utilizes an aluminum alkyl such as diethylaluminum ethoxide (DEAEO), it is believed that the finished catalyst does not contain Cr(VI), but contains chromium in lower oxidation states probably Cr(II), Cr(III) and/or Cr(IV). Tables 3.4 and 3.5 summarize some polymerization data for... 

A new catalyst in which chromocene was supported on silica gel was developed by Union Carbide" for use in gas-phase polymerization reactions. A typical catalyst contained about 2.5% by weight of chromium, and was activated by the addition of small amounts of alkylaluminium alkoxides, such as diethyl-aluminium ethoxide. Use of such a catdyst formulation gave rise to a polymer with much narrower molecular weight distributions. The average molecular weight could be controlled by the addition of hydrogen, which caused termination of the growing chain. 

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