Transition metal cations, catalysts containing

Use of Catalysts Containing Transition Metal Cations. Ethyl -ene being alkylated over certain zeolite catalysts reacts specifically. Ethylene can not, however, be alkylated with Isobutane In the presence of H2SO., because of the formation of stable ethylsulphates. We examined the Isobutane - ethylene alkylation over crystalline aluminosilicates and found that those catalysts containing RE and/or Ca In combination with transition metal cations were most active. The alkylation has resulted In not hexanes as would be expected, but an alkylate containing octane Isomers as the major product (about 80%). Moreover, the product composition was similar to that obtained from n-butene over CaREY. The TMP-to-DMH ratios were 7.8 and 7.1 respectively. 

In 1971, LDHs containing different metal cations (such as Mg, Zn, Ni, Cr, Co, Mn and Al) with carbonate as interlayer anions, calcined at 473-723 K and partially or completely chlorinated, were reported to be effective as supports for Ziegler catalysts in the polymerization of olefins [8], with the maximum catalytic activity of polyethylene production observed for Mg/Mn/Al - CO3 LDH calcined at 473 K. Even earher, calcined Mg/Al LDHs were used to support Ce02 for SO removal from the emissions from fluidized catalytic cracking units (FCCU) [9,10]. Some transition metal oxides have also been... 

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). 

Ca cation Introduction leads to the catalyst containing both kinds of catalytic sites, and the ethylene-isobutane Interaction over this catalyst proceeds through dimerization to the alkylation step, yielding high quality alkylate (Table V, column 4). The alkylate yield was 120X. The reaction does not occur unless transition metal cations are present In the catalyst even though the latter may contain acidic sites (CaY for example). It Is understood that no butenes are formed In this case, and ethylene does not Interact directly with Isobutane under the conditions of this experiment. 

Zeolites containing transition metai offer interesting possibilities to combine acid properties and a hydrogenation function in bifunctional catalysts. For hydrotreating, e.g. for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions, both functions are essential the acid properties are provided by the zeolite, the hydrogenation activity by the sulfided transition metal cations [1,2]. It can be expected that these catalysts will be attractive alternatives to alumina supported Co-Mo and Ni-Mo hydrotreating catalysts because of their superior catalytic properties. 

On the other hand, ethylene cannot be used in isobutane/olefin alkylation on sulphuric acid, because of the formation of stable ethylsulfates. However, when using a R,Ca-Y catalysts in combination with transition-metal cations (especially Ni) (Minachev et al. 1977) an alkylate containing octane isomers as the major product (about 80%), without the formation of hexanes has been obtained. They observed a strong influence of the chemical composition on the catalytic behaviour of R,Ca-Y zeolites, showing a maximum on a R,Ca-Y (16.6% Ca and 64.2% R) zeolite. 

The polymerization of 1,3-cyclohexadiene can be initiated by free radicals, Ziegler-Natta catalysts, and transition metal catalysts, both cationically and anionically [413-416]. The synthesis of high-molecular-weight poly (1,3-cyclohexadiene) containing 1,4-structures (62), especially has been of great interest, as unbranched poly(/ -phenylenes) are accessible from it after dehydrogenation [417-419]. 

More remarkably, structurally well-characterized Phen-containing transition metal complexes have been prepared and further applied in challenging organic transformations. Thus, cationic palladium complexes of t)fpe Pd(phen)2X2 (where X = CF3SO3, PFs, BF4) are very stable and found fairly active in combination with either benzoic acids or phosphorus acids as cocatalysts in the conversion of nitroarenes to the corresponding carbamate derivatives. Extensive studies have evidenced the key role of the nature of counteranion X of such Phen-based catalysts in the reaction outcome and even metaUacycles of type A have been isolated and identified as active intermediates in the reductive carbonyla-tion of nitrobenzene (eq l). ... 

In 1826 J. J. Berzelius found that acidification of solutions containing both molybdate and phosphate produced a yellow crystalline precipitate. This was the first example of a heteropolyanion and it actually contains the phos-phomolybdate ion, [PMoi204o] , which can be used in the quantitative estimation of phosphate. Since its discovery a host of other heteropolyanions have been prepared, mostly with molybdenum and tungsten but with more than 50 different heteroatoms, which include many non-metals and most transition metals — often in more than one oxidation state. Unless the heteroatom contributes to the colour, the heteropoly-molybdates and -tungstates are generally of varying shades of yellow. The free acids and the salts of small cations are extremely soluble in water but the salts of large cations such as Cs, Ba" and Pb" are usually insoluble. The solid salts are noticeably more stable thermally than are the salts of isopolyanions. Heteropoly compounds have been applied extensively as catalysts in the petrochemicals industry, as precipitants for numerous dyes with which they form lakes and, in the case of the Mo compounds, as flame retardants. 

A large number of transition metal complexes whose cationic complexes are 10- to 16-electron species (including those with the ligands summarized in Fig. 7) were investigated to determine their potential as ethylene polymerization catalysts with methyaluminoxane (MAO) activation at 25 °C under atmospheric pressure. As a result, we discovered a number of high-activity catalysts for ethylene polymerization that contain electronically flexible ligands [11]. 

In contrast to heterogeneous Ziegler-Natta catalysts, homogeneous catalysts based on biscyclopentadienyl derivatives of group 4 transition metals, which contain cationic metallocene species of formally d° 14-electronic structure, hardly promote the polymerisation of conjugated dienes, since the diene can act as a donor of four electrons rather than of two electrons as in monoolefin polymerisation (let us recall that the polymerisation of conjugated dienes is catalysed by half-sandwich metallocene-based catalysts). However, it has been reported [162] that statistical copolymers of ethylene and butadiene were obtained with the Cp2ZrCl2— [Al(Me)0]x catalyst. 

We wish also to point out that the fact that in the above schemes only the transition metal, the last polymerized unit, and the coordinated monomer are represented does not mean that the catalysts prepared from A1(C2H5)3 and a titanium alkoxyde or from A1(C2H5)2C1 and a Co compound are pure organo-metallic compounds of Ti or Co, respectively. These catalysts are presumably complexes containing A1 and the transition metal, the latter probably being part of a cation, the A1 of an anion. In the above schemes we have represented only the transition metal for the sake of simplicity. 

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