Titanium metal-modified

A soluble titanium-based modified Ziegler-Natta catalyst [Ti(OR)4-Et3Al, R = n-Bu, isoPr] is employed in the reaction.42 Since similar catalysts may be used for the oligomerization and polymerization of ethylene, the nature and oxidation state of the metal and reaction conditions determine selectivity. Ti4+ was found to be responsible for high dimerization selectivity, whereas polymerization was shown to be catalyzed by Ti3+. According to a proposed mechanism,42,43 this catalyst effects the concerted coupling of two molecules of ethylene to form a metal-lacyclopentane intermediate that decomposes via an intramolecular p-hydrogen transfer ... 

Metallocenes (Fig. 2) are sandwich structures, typically incorporating a transition metal such as titanium, zirconium, or hafnium in the center. The metal atom is linked to two aromatic rings with five carbon atoms and to two other groups—often chlorine or alkyl. The rings play a key role in the polymerization activity (23-27). Electrons associated with the rings influence the metal, modifying its propensity to attack carbon-carbon double bonds of the olefins. The activities of these metallocenes combined by aluminum alkyls, however, are too low to be of commercial interest. Activation with methylaluminoxane, however, causes them to become 10-100 times more active than Ziegler-Natta catalysts. 

For redox catalysis, efforts have been spent on preparing transition metal modified mesoporous materials. These materials are capable of extending the catalytic oxidation chemistry to large molecules. The selective catalytic activity has also been demonstrated, for example, in the oxidation of aromatic compounds by using titanium-containing mesoporous silica (Ti-MCM-41 and Ti-HMS). ... 

The process is based on the fact that alkali metal-modified or alkaline earth modified zeolites of type X, A, L or ZMS-5 and also titanium dioxide, adsorb p-cresol more strongly than m-cresol. Thus m-/p-cresol mixtures can be separated in an adsorption column and can be dissolved again with a suitable desorbing liquid such as an aliphatic alcohol and ketone. The separating efficiency depends both on adsorption and desorption. 

BASF has also claimed the use of metal-modified TS-1 catalysts [25]. Various catalyst compositions have been described, including (i) titanium or vanadium silicalites containing rare earth ions [25a] and (ii) titanium or vanadium silicalites containing noble metals (Ru, Rh, Pd, Os, Ir, Pt, Re, Au, Ag). In these systems the... 

The objectives of this Workshop, to present and discuss new results in the development and processing of metallic materials with high structural efficiency and to establish new interactions and networks between the participants, were successfully met. A number of new developments were presented and discussed at this Workshop, including recent information on titanium alloys modified with relatively small amounts of B and Si to provide dramatic improvements in strength and stiffness, and new A1 alloys strengthened with quasicrystalline precipitates for good elevated temperature properties. In addition, a current extensive update on severe plastic deformation and on nanocrystalline metals for structural applications was provided. 

Dolat D, Mozia S, Wrobel R, Moszynski D, Ohtani B, Guskos N, Morawski A (2015) Nitrogen-doped, metal-modified rutile titanium dioxide as photoeatalysts for water remediation. Appl Catal Environ 162 310-318... 

Some porous ceramic structures of oxides on titanium (CT2O3, RuOj, MnOj, VOJ obtained by baking films of metal complexes like acetylacetonates on titanium surfaces can also be regarded as chemically modified electrodes Applications... 

The process has been commercially implemented in Japan since 1977 [1] and a decade later in the U.S., Germany and Austria. The catalysts are based on a support material (titanium oxide in the anatase form), the active components (oxides of vanadium, tungsten and, in some cases, of molybdenum) and modifiers, dopants and additives to improve the performance, especially stability. The catalyst is then deposited over a structured support based on a ceramic or metallic honeycomb and plate-type structure on which a washcoat is then deposited. The honeycomb form usually is an extruded ceramic with the catalyst either incorporated throughout the stmcture (homogeneous) or coated on the substrate. In the plate geometry, the support material is generally coated with the catalyst. 

In 1990, Choudary [139] reported that titanium-pillared montmorillonites modified with tartrates are very selective solid catalysts for the Sharpless epoxidation, as well as for the oxidation of aromatic sulfides [140], Unfortunately, this research has not been reproduced by other authors. Therefore, a more classical strategy to modify different metal oxides with histidine was used by Moriguchi et al. [141], The catalyst showed a modest e.s. for the solvolysis of activated amino acid esters. Starting from these discoveries, Morihara et al. [142] created in 1993 the so-called molecular footprints on the surface of an Al-doped silica gel using an amino acid derivative as chiral template molecule. After removal of the template, the catalyst showed low but significant e.s. for the hydrolysis of a structurally related anhydride. On the same fines, Cativiela and coworkers [143] treated silica or alumina with diethylaluminum chloride and menthol. The resulting modified material catalyzed Diels-Alder reaction between cyclopentadiene and methacrolein with modest e.s. (30% e.e.). As mentioned in the Introduction, all these catalysts are not yet practically important but rather they demonstrate that amorphous metal oxides can be modified successfully. 

The key effect of oxide supports on the catalytic activities of metal particles is exerted through the interface between oxides and metal particles. The key objective of this study is to develop synthesis methodologies for tailoring this interface. Here, an SSG approach was introduced to modify the surface of mesoporous silica materials with ultrathin films of titanium oxide so that the uniform deposition of gold precursors on ordered mesoporous silica materials by DP could be achieved without the constraint of the low lEP of silica. The surface sol-gel process was originally developed by Kunitake and coworkers.This novel technology enables molecular-scale control of film thickness over a large 2-D substrate area and can be viewed as a solution-based... 

Metal ion modified polyimide films have been prepared to obtain materials having mechanical, electrical, optical, adhesive, and surface chemical properties different from nonmodified polyimide films. For example, the tensile modulus of metal ion modified polyimide films was increased (both at room temperature and 200 0 whereas elongation was reduced compared with the nonmodif ied polyimide (i). Although certain polyimides are )cnown to be excellent adhesives 2) lap shear strength (between titanium adherends) at elevated temperature (275 0 was increased by incorporation of tris(acetylacetonato)aluminum(III) (2). Highly conductive, reflective polyimide films containing a palladium metal surface were prepared and characterized ( ). The thermal stability of these films was reduced about 200 C, but they were useful as novel metal-filled electrodes ( ). 

---