Reduction of TiCL

TiCl catalysts produced by the reduction of TiCl with Al(C2H 2d> subsequentiy treated first with an electron donor (diisoamyl ether), then with TiCl, are highly stereospecific and four to five times more active than d-TiCl (6). These catalysts were a significant advance over the earlier TiCl systems, because removal of atactic polymer was no longer required. They are often referred to as second-generation catalysts. The life of many older slurry process faciUties has been extended by using these catalysts to produce "clean" polymers with very low catalyst residues. 

Other methods iaclude hydrogen reduction of TiCl to TiCl and TiCl2 reduction above the melting poiat of titanium metal with sodium, which presents a container problem plasma reduction, ia which titanium is collected as a powder, and ionized and vaporized titanium combine with chlorine gas to reform TiCl2 on cool-down and aluminum reduction, which reduces TiCl to lower chlorides (19,20). 

Titanium trichloride is almost always prepared by the reduction of TiCl, most commonly by hydrogen. Other reduciag agents iaclude titanium, aluminum, and 2iac. Reduction begias at temperatures of ca 500°C and under these conditions a-TiCl is formed. The product is cooled quickly to below 450°C to avoid disproportionation to the di- and tetrachlorides. P-TiCl is prepared by the reduction of titanium tetrachloride with aluminum alkyls at low (80°C) temperatures whereas y-TiCl is formed if titanium tetrachloride reacts with aluminum alkyls at 150—200°C. At ca 250°C, the P-form converts to d. d-TiCl is made by prolonged grinding of the d- or y-forms. 

Lower oxides of titanium, Ti2C>3 and TiO, have been produced by reduction of TiCL. 

Tripositwe titanium is an excellent reducing agent, lying between H2 and Sn(II) in potential. Reduction of TiCl " electrolytically or with... 

TiCb produced by reduction of TiCL with aluminium, and containing 4.7% Al. From Fig. 4 in ref. 30. 

Early (1960-1965) commercial Ziegler-Natta catalysts were produced by reduction of TiCl using metallic aluminum, hydrogen or an aluminum alkyl. Simplified overall equations are listed below ... 

In TiClj, each Ti is octahedral in each of the four crystalline modifications identified. The brown, fibrous or jS-form of TiClj is prepared by low temperature reduction of TiCl with trialkylaluminum compounds and consists of (TiClj) polymeric chains composed of confacially linked Ti octahedra. The Ti-Ti separation of 291 pm is similar to that found in elemental Ti, and the RT magnetic moment is half of that found for the a form of TiClj (12.1 x 10 A m ) . Both TiClj andTiClj are antiferromagnetic, with low magnetic moments relative to related monomeric complexes. All three layered forms of TiClj (a, y, S) have Ti-Ti distances greater than 350 pm, and no metal-metal interaction is evident. Reduction of TiCl is the route to reduced Ti chlorides with syntheses of the four TiClj modifications summarized in Table 1 ". Preparations involve collection of the TiClj at low temperature to avoid disproportionation ... 

The reduction of TiCl(/r2-OCMe2CI I2Ph2P)3RhCl afforded the formally Tini/Rh(0) species Ti(/ 2-OCMe2CH2Ph2P)3Rh (98), which was reported to have a Ti—Rh bond distance of 2.2142(11) A.1005... 

Titanium owes its great importance due to its excellent mechanical and corrosion performance. Titanium is produced by reduction of TiCl with magnesium (Kroll method) or sodium (Hunter method). As the cost of Hunter method is higher than Kroll method, Kroll method is considered the most efficient method for titanium electrodeposition. 

Recently, The reduction of TiCl has been studied in Lewis acid ionic liquids [BmimjCl/AlClj in our laboratory. It was found that the aluminum-titanium alloy of 14 pm thickness as given in Fig. 5.9 can be deposited on the titanium or aluminum substrate. Thermodynamically, Ti deposition should be possible in thick layers in ionic liquids, but the right ionic liquid and especially the right titanium precursors still have to be found. An idea might be to make TiCTf N) or similar compounds for titaninm electrodeposition. 

The reduction of TiCls with 4 eq. of LiAlH4 in THF gives a fine black suspension of a titanium(II) species. A 4 1 ball-milled mixture of TiCls and L1A1H4 is available from Alfa Inorganics ( McMurry s Reagent )- Addition of this stable solid to THF leads to evolution of hydrogen and formation of titanium(II). 

Although the coordination chemistry of TP and, to a lesser extent, TP has been relatively well investigated, few complexes are known in the lower oxidation states and are almost all unstable to oxidation. Reduction of TiCL with excess of dilithium 2,2 -bipyridyl in THF with excess bipyridyl gives Li[Ti(bpy)3]-3THF, as shown in equations (5) and (6). Further reduction to Li2[Ti(bpy)3]-3.7THF is possible. ... 

The homoleptic see Homoleptic Compound) titanium diene complex (jj -r-BuCH=CHCH=CHBu-r)2Ti (11) has been prepared by the condensation of electron-beam vaporized titanium with an excess of 1,4-di-r butylbuta-1,3-diene (5ee Metal Vapor Synthesis of Transition Metal Compounds). The bis-diene dmpe complex Ti(dmpe)( -C4H6)2Ti (12) has been prepared by the reduction of TiCL (dmpe) with Na/Hg in the presence of butadiene, and by the reduction of TiCU with CH2=CHLi in the presence of dmpe. ... 

Reduction of TiCL with Na/Hg, or of TiCL with Li in THF and 2,2 -bipyridine leads to violet [Ti(bpy)3]. Formally this contains Ti(0), but results of MO calculations and spectroscopic studies indicate that electron delocalization occurs such that the complex should be considered as [Ti (bpy )3] see also the end of Section 20.5 and discussion of complexes containing ligand 20.12 in Section 20.7. 

In a certain aspect the Kroll and Hunter metallothermic reduction processes can be seen as indirect electrowinning processes that rely on fused salt electrolytic production of magnesium or sodium for reduction of TiCl, Battelle Columbus Laboratories (1975) - Interim Report on Energy Use Patterns in Metallurgical Processing. -Columbus, OH. 

The reduction of TiCl with diphenylmagnesium to produce highly-active ethylene polymerization catalysts was reported by scientists L. Petkov, R. Kyrtcheva, Ph. Radenkov and D. Dobreva [38,39] at SEC Neftochim Research Centre in Bourgas, Bulgaria. This catalyst exhibited an activity of about 30,000 g PE/gTi for a 0.25 hr polymerization at 75°C and ethylene pressure of 5 kg/cm ... 

In U.S. Patent 4,174,429 [54], Montedison characterized a large number of Mg/Ti/Cl/electron donor complexes based on a wide variety of ligands such as ethyl acetate, ethanol, ethyl benzoate, benzonitrile, ethylene carbonate, n-butyl acetate and diethyl ether, using TiClj prepared from hydrogen reduction of TiCl. ... 

The basic mechanism of ethylene polymerization is shown in Figure 6.4. Apart from the bulk reduction of TiCl that produces colloidal TiClj, a critical role of the cocatalyst at a molecular level is to effect the chain initiation reaction by forming a Ti-carbon bond. This reaction, the conversion of 6.1 to 6.2, may also be classified as a chain transfer reaction where the chain is just an ethyl group. 

Write balanced equations for (a) ohgomerization of ethylene using AlEtj (b) reductions of TiCl with AlEtj and AlEt Cl (c) reaction of Cp TiClj with AlMCj (d) reaction of AlMCj wito water in (n+ l)/n molar ratio (e) reaction of a constrained geometry catalyst with 2 mol of MAO. 

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