Thorium catalyst

However, with 1-hexyne or phenylacetylene, the thorium catalyst induces a dramatic inversion in regioselectivity giving imines with various amounts of dimerized alkyne (e.g., Eq. 4.84) [301],... 

Usually not considered as Fischct-Tropsch processes are the methanol synthesis with oxidic chromium/zinc catalysts (c.f. the chapter on Methanol Building Block for Chemicals ) or the higli-pressure-high-temperature synthesis of higher alcohols over alkalized methanol catalysts or thorium catalysts (isobutyl synthesis). Tliese reactions, as well as the methanation reactions, are not covered in this contribution. 

The presence of zinc oxide in thorium catalysts increased the amount of liquid products. The search for a possible substitute for thorium oxide led to the discovery that a two-component catalyst, composed of aluminum and zinc oxides, was capable of catalyzing the formation of higher hydrocarbons as well as that of isobutane. However, the space-time yields obtained with the catalysts of this type are lower than those obtained with the corresponding Th02 catalysts. 

A claim has been made in patents issued to Auzies (374) that nicotine can be prepared on an industrial scale from ammonia and butadiene. This process is reported to involve the production of pyrrole by the catalytic interaction of ammonia and butadiene, the methylation and hydrogenation of pyrrole, the conversion of ZV-methylpyrrolidine to 8-chloropyridine by heating over a thorium catalyst with chloroform, and the interaction of /8-chloropyridine with A-methylpyrrolidine over the same catalyst. The process, however, does not seem to have been put into practice and the reactions described have never been confirmed by a precise chemical investigation. 

The intermolecular process (8 and 9) showed two hydroamination regioselec-tivities depending on the precatalyst. The intermolecular hydroamination catalyzed by the metallocene thorium catalyst yielded the methyl alkyl-substituted imines in... 

Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens. In this application it can be incorporated into oven walls to prevent the collection of cooking residues. 

This is a way to do this procedure without having to use one of those crazy tube furnaces stuffed with thorium oxide or manganous oxide catalyst [21]. The key here is to use an excess of acetic anhydride. Using even more than the amount specified will insure that the reaction proceeds in the right direction and the bad side reaction formation of dibenzylketone will be minimalized (don t ask). 18g piperonylic acid or 13.6g phenylacetic acid, 50mL acetic anhydride and 50mU pyridine are refluxed for 6 hours and the solvent removed by vacuum distillation. The remaining residue is taken up in benzene or ether, washed with 10% NaOH solution (discard the water layer), and vacuum distilled to get 8g P2P (56%). 

Allyl Complexes. Allyl complexes of thorium have been known since the 1960s and are usually stabilized by cyclopentadienyl ligands. AEyl complexes can be accessed via the interaction of a thorium haUde and an aHyl grignard. This synthetic method was utilized to obtain a rare example of a naked aHyl complex, Th(Tj -C2H )4 [144564-74-9] which decomposes at 0°C. This complex, when supported on dehydroxylated y-alumina, is an outstanding heterogeneous catalyst for arene hydrogenation and rivals the most active platinum metal catalysts in activity (17,18). 

Silver-containing catalysts are used exclusively in all commercial ethylene oxide units, although the catalyst composition may vary considerably (129). Nonsdver-based catalysts such as platinum, palladium, chromium, nickel, cobalt, copper ketenide, gold, thorium, and antimony have been investigated, but are only of academic interest (98,130—135). Catalysts using any of the above metals either have very poor selectivities for ethylene oxide production at the conversion levels required for commercial operation, or combust ethylene completely at useful operating temperatures. 

Thorium oxide on activated carbon was prepared by absorption of thorium nitrate from its solution in anhydrous acetone on the activated carbon Supersorbon. The excess solution was decanted, the catalyst was dried at 80 °C, and the adsorbed thorium oxide was decomposed by excess 5% ammonium hydroxide solution. After repeated washing and decanta-nation with distilled water and acetone, the catalyst was dried at 180°C. It was then stabilized by heating to 360°C for 5 hr in a stream of nitrogen. The content of thorium oxide was 2.9% (wt.). The BET surface area was 870 m2/g. Prior to kinetic measurements, the catalyst was modified by passing over acetic acid vapors (100 g acid/1 g catalyst). 

Parallel ketonization of acetic acid and propionic acid was one of the transformations of this type studied in our Laboratory. Ryba6ek and Setinek (94) investigated the kinetics of these reactions in the gaseous phase at 316°C using thorium oxide on activated carbon (p. 27) as the catalyst. This model system allowed the study of each reaction separately as well as of the simultaneous conversion of both acids. 

The reaction does not proceed in the absence of catalysts. As the contemporary Fischer-Tropsch catalysts were heterogeneous, the first hydroformylation catalyst was a solid (66% silica, 30% cobalt, 2% thorium oxide, and 2% magnesium oxide). Only later was the conclusion reached and proved (5) that the actual catalytic species is homogeneous. 

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