Thallium catalysts, oxidative

The presence of thallium(0) led to an increase in activity and selectivity of metallic palladium catalysts supported on silica in aldose oxidation reactions. However, silica-supported thallium(0) had no activity by itself (entry 3). ° Similarly, the bimetallic catalyst platinum-thallium/ZSM-5, prepared by impregnation of thallium sulfate and chloroplatinic acid on Zeolite Socony Mobil-5 (ZSM-5), showed greater selectivity in propane aromatisation and almost the same catalytic activity as monometallic thallium/ZSM-5 (entry 4). Similar comparison of vanadium-caesium-copper and vanadium-caesium-copper-thallium catalysts supported on TiOa.SiC demonstrated that addition of thallium improved the catalytic activity in partial oxidation of p-tert-butyltoluene to p-tert-butyl-benzaldehyde (entry The application of solid-supported thallium-based catalysts in different processes includes (a) iron-thallium catalysts in carbon monoxide hydrogenations to form hydrocarbons and alcohols, and catalytic reforming of... 

Most synthetic camphor (43) is produced from camphene (13) made from a-piuene. The conversion to isobomyl acetate followed by saponification produces isobomeol (42) ia good yield. Although chemical oxidations of isobomeol with sulfuric/nitric acid mixtures, chromic acid, and others have been developed, catalytic dehydrogenation methods are more suitable on an iadustrial scale. A copper chromite catalyst is usually used to dehydrogenate isobomeol to camphor (171). Dehydrogenation has also been performed over catalysts such as ziac, iadium, gallium, and thallium (172). 

The Teijin oxychlorination, on the other hand, is considered a modern version of the obsolete chlorohydrin process for the production of ethylene oxide. In this process, ethylene chlorohydrin is obtained by the catalytic reaction of ethylene with hydrochloric acid in presence of thallium(III) chloride catalyst ... 

Isobutylene oxide is produced in a way similar to propylene oxide and butylene oxide by a chlorohydrination route followed by reaction with Ca(OH)2. Direct catalytic liquid-phase oxidation using stoichiometric amounts of thallium acetate catalyst in aqueous acetic acid solution has been reported. An isobutylene oxide yield of 82% could be obtained. 

Friedel-Crafts reactions involving electrophilic substitution of aromatic compounds have been reported on solid base catalysts such as thallium oxide and MgO. The rates of benzylation of toluene by benzyl chloride over MgO nanocrystals were found to be of the order CP-MgO > CM-MgO > AP-MgO.56 An important observation in the study was that x-ray diffraction of the spent catalyst... 

The lithium and thallium (I) salts of i satin-3-oxime (isatin oximates) were employed in the development of ion-selective electrodes for these cations. Transition metal complexes of isatin derivatives can also be employed as catalysts for the oxidative self-coupling of alkylphenol s639,640. 

Thallium Dorfman and Gryder, investigating the kinetics of the Ce(IV)-Tl(I) reaction, concluded that the mechanism involves two 1-equivalent oxidation steps with a Ce(rV) dimer, with T1(II) as an intermediate. They pointed out that the reaction may be complicated by the formation of OH or NOs free radicals that oxidize TI(I). Sinha and Mathur studied the Ce(IV)-Tl(I) reaction in the presence of the catalysts Ag(I) and Os(VIII). The rate was found to be first order with respect to both Ce(IV) and T1(I) but unaffected by Ce(III) or T1(III). Bisulfate and hydrogen ions acted as inhibitors. The slow step in sulfuric acid medium was considered to be... 

Diarylacetylenes are converted in 55-90% yields into a-diketones by refluxing for 2-7 h with thallium trinitrate in glyme solutions containing perchloric acid [413. Other oxidants capable of achieving the same oxidation are ozone [84], selenium dioxide [509], zinc dichromate [660], molybdenum peroxo complex with HMPA [534], potassium permanganate in buffered solutions [848, 856, 864,1117], zinc permanganate [898], osmium tetroxide with potassium chlorate [717], ruthenium tetroxide and sodium hypochlorite or periodate [938], dimethyl sulfoxide and iV-bromosuccin-imide [997], and iodosobenzene in the presence of a ruthenium catalyst [787] (equation 143). 

Whereas internal acetylenes are oxidized to a-diketones, terminal acetylenes give carboxylic acids with one less carbon on treatment with thallium trinitrate [413], potassium permanganate [843], iodosobenzene with tris(triphenylphosphine)ruthenium dichloride as a catalyst [787], or a rather rare oxidant, pentafluoroiodobenzene bis(trifluoroacetate) [797] (equation 144). 

The polycondensation of BHET to PET proceeds in the melt at temperatures of 270-305 °C, under vacuum (< 1 mbar absolute pressure) and in the presence of Lewis acid metal compounds, such as titanium alkoxides, dialkyltin oxide, gallium oxide, germanium oxide, thallium oxide, lanthanide salts, and most commonly, antimony oxide [1,2, 22-26]. Under polymerization reaction conditions, these catalysts are generally converted to their alkoxides with ethylene glycol. Typical of such alkoxides is antimony(III) glycolate, the active catalyst for the majority of the world s PET production [27] (cf. Structure 1). 

A homogeneous catalyst exists in the same phase as the reactants. Ceric ion, Ce4+, at one time was an important laboratory oxidizing agent that was used in many redox titrations (Section 11-8). For example, Ce + oxidizes thallium(I) ions in solution this reaction is catalyzed by the addition of a very small amount of a soluble salt containing manganese(II) ions, Mn +. The Mn + acts as a homogeneous catalyst. 

It takes place at atmospheric pressure, between 450 and 550 C in the presence of a silver oxide based catalyst deposited on silica or of earth alkali metal oxides, thallium and lead, and with excess propylene. An inert (nitrogen, steam, etc.) is used as diluent, in order to absorb the heat generated daring the conversion, whose molar yield is 7Q per cent in relation to propylene. 

Thallium oxide supported on differenf materials was studied as a catalyst in benzene acylation with In general, TIO deposited on... 

Ghoudhary, V. R. and Jana, S. K. 2001. Highly active and low moisture sensitive supported thallium oxide catalysts for Friedel-Crafts-type benzylation and acylation reactions strong thallium oxide-support interactions. /. Catal. 201 225-235. 

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