Catalysts transition metal containing

Union Carbide Corp. also uses a siUca-supported chromium catalyst in their extremely low cost Unipol gas-phase linear low density ethylene copolymer process, which revolutionized the industry when it was introduced in 1977 (86—88). The productivity of this catalyst is 10 —10 kg polymer/kg transition metal contained in the catalyst. By 1990, the capacity of Unipol linear low density polyethylene reactors was sufficient to supply 25% of the world s total demand for polyethylene. 

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

We may thus conclude after this short overview on DeNO technologies that NH3-SCR using catalysts based on V-W-oxides supported on titania is a well-established technique for stationary sources of power plants and incinerators, while for other relevant sources of NO, such as nitric acid tail gases, where emissions are characterized from a lower temperature and the presence of large amounts of NOz, alternative catalysts based on transition metal containing microporous materials are possible. Also, for the combined DeNO -deSO, alternative catalysts would be necessary, because they should operate in the presence of large amounts of SO,.. Similarly, there is a need to develop new/improved catalysts for the elimination of NO in FCC emissions, again due to the different characteristics of the feed with respect to emissions from power plants. 

Overall, ADMET polymerization is an advantageous strategy for synthesizing transition metal-containing polymers because of the functional group tolerance of the metathesis catalysts employed, the mild conditions under which it operates, the wide range of accessible architectures, and the precise structural control afforded by the method. 

Dimerization presumably takes place on the transition metal-containing sites, and alkylation on the acidic sites of zeolltic surface. The sodium form of zeolite exchanged with transition metal cations Is capable of dimerization (and further polymerization), but does not practically exhibit alkylating capacity. This explains the composition of the product obtained from ethylene and Isobutane over this catalyst (Table V, column 3). 

The term alkene (olefin) metathesis refers to the equilibrium reaction shown in equation (1) in which the alkylidene groups of a pair of alkenes are exchanged with one another in the presence of a transition metal-containing catalyst. The reaction involves the net cleavage of the bonds of the substrate(s) and formation of the new carbon-carbon double bonds of the prodncts. Once equilibrium has been established, the resultant prodnct mixture has a distribution of alkenes (including isomers) that is determined solely by the relative thermodynamic stabilities of the prodncts. 

Table 1.3 Principal characteristics of transition metal-containing catalysts for polyethylene production.

In the present paper, we report some aspects of the oxidation of aniline with various peroxides over a series of transition metal - containing molecular sieves having different structures. The influence of the catalyst structure, of the nature and concentration of the peroxide and of the incorporated metal are discussed. 

Ni-Mo or NAt present, industrial hydrotreating processes are based on alumina supported Co-Mo or Ni-W sulfide catalysts (2,3). We expect that transition metal containing molecular... 

Some of the asymmetric C-C bond forming addition reactions only partially rely on the use of transition metal catalysts, e.g., Diels Alder reactions induced by transition-metal-containing chiral Lewis acids (Section D.1.6.1.1.), chiral versions of transition metal induced... 

Transition metal-containing molecular sieves exhibit remarkable properties as catalysts for a variety of oxidation reactions with peroxides as the oxidant [1]. The potential of transition metal containing zeolites is however, limited because of the number and t e of heteroelements that can be incorporated in the framework and also the pore sizes of the resulting molecular... 

The catalysis of di- or fri-metal-substituted polyoxometalates is interesting not only to understand the action of transition-metal-containing biomolecules but also to design an active catalyst for hydrocarbon oxidation. (2) Further development of micro/meso porous materials containing polyoxometalates or related compounds is expected. These materials will concentrate hydrocarbons in the pores and promote the selective oxidation catalysis. 

AE reactions of simple olefins. The Sharpless AE reaction has been supplemented by other approaches to asymmetric epoxide synthesis the most evident goal being to obviate the need for an allylic alcohol. Attempts to carry out asymmetric epoxidation reactions on simple olefins have utilized transition-metal-containing catalysts such as porphyrins as well as stoichiometric chiral reagents (peroxides, dioxiranes, and oxaziridines). These approaches have been summarized [19]. 

Finally, new types of NOx and SOx abatement catalysts use rare earths in their formulations, helping to increase the activity and stability of transition-metal-containing zeolites. 

Monoborides of transition metals contain single boron chains in the matrix of metal atoms. The monoborides of Zr, Hf, and Ta are superconductors that have a critical temperature of 3-4°C. LuRh4B4 is a superconductor having a transition temperature of ll.T C and the superconducting transition temperature of YPdjBjC (0.3 < X < 0.4) is 23 K. NiB is used as a catalyst in fuel cells to lower the overvoltage. 

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