Titanium carbon monoxide hydrogenation

At high temperature, Ti02 reacts with reducing agents such as carbon monoxide, hydrogen, and ammonia to form titanium oxides of lower valency metallic titanium... 

The hydrogenation of carbon dioxide to produce methanol is a very important commercial process [466], which could be used to reduce the greenhouse effect [467]. Haruta showed that gold supported on titanium, iron, or zinc oxides exhibits an appreciably high activity for carbon dioxide (Fig. 6.20) and carbon monoxide hydrogenation, between 423 and 673 K, when very fine gold particles are deposited on oxide supports by either CP or DP methods [31,468,469]. 

Sakurai, H. Haruta, M. Carbon Dioxide and Carbon Monoxide Hydrogenation over Gold Supported on Titanium, Iron, and Zinc Oxides. Appl. Catal. A Gen. 1995,127, 93-105. 

Titanium carbide may also be made by the reaction at high temperature of titanium with carbon titanium tetrachloride with organic compounds such as methane, chloroform, or poly(vinyl chloride) titanium disulfide [12039-13-3] with carbon organotitanates with carbon precursor polymers (31) and titanium tetrachloride with hydrogen and carbon monoxide. Much of this work is directed toward the production of ultrafine (<1 jim) powders. The reaction of titanium tetrachloride with a hydrocarbon-hydrogen mixture at ca 1000°C is used for the chemical vapor deposition (CVD) of thin carbide films used in wear-resistant coatings. 

Reactor materials. One drawback that could be mentioned is the high corrosivity of iodide. Hydrogen iodide is very corrosive, but the presence of iodide salts makes it even worse. Carbon monoxide will also react with many metals under the reaction conditions (30 bar of CO, 180 °C). Hastelloy-C is an inert material which is used in the laboratory. For the actual plants titanium cladded reactors have been mentioned as a possible solution. 

Sulfur and carbon monoxide can be killers (literally) with hydrogenation catalysts. It will poison them, making them completely ineffective. Some sulfur often shows up in the benzene feed, carbon monoxide in the hydrogen feed. The alternatives to protect the catalyst are either to pretreat the feed and/or the hydrogen or to use a sulfur resistant catalyst metal like tin, titanium, or molybdenum. The economic trade-offs are additional processing facilities and operating costs vs. catalyst expense, activity, and replacement frequency. The downtime consequences of catalyst replacement usually warrarit the more expensive treatment facilities. 

Jacoby et al. (1994) studied the photocatalytic reaction of gaseous trichloroethylene in air in contact with UV-irradiated titanium dioxide catalyst. The UV radiation was kept less than the maximum wavelength so that the catalyst could be excited by photons, i.e., X <356 nm. Two reaction pathways were proposed. The first pathway includes the formation of the intermediate dichloroacetyl chloride. This compound has a very short residence time and is quickly converted to the following compounds phosgene, carbon dioxide, carbon monoxide, carbon dioxide, and hydrogen chloride. The second pathway involves the formation of the final products without the formation of the intermediate. 

The action of carbon tetrachloride or a mixture of chlorine with a hydrocarbon or carbon monoxide on the oxide.—H. N. Warren 9 obtained aluminium chloride by heating the oxide to redness with a mixture of petroleum vapour and hydrogen chloride or chlorine, naphthalene chloride or carbon tetrachloride was also used. The bromide was prepared in a similar manner. E. Demarpay used the vapour of carbon tetrachloride, the chlorides of chromium, titanium, niobium, tantalum, zirconium, cobalt, nickel, tungsten, and molybdenum H. Quantin, a mixture of carbon monoxide and chlorine and W. Heap and E. Newbery, carbonyl chloride. 

In this paper we review the results of our systematic work on the catalytic and adsorptive properties of transition metal carbides (titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and iron). We focus our attention on the oxidation of hydrogen, carbon monoxide, ammonia, and the oxidative coupling of methane. The first two reactions are examples of complete (non-selective) oxidation, while the oxidation of ammonia simulates a selective oxidation process. The reaction of oxidative coupling of methane is being intensively explored at present as a means to produce higher hydrocarbons.5 10... 

Bis(i -cyclopentadienyl)titanium or titanocene, (Tj-C5H5)2Ti (1), and bis(i7-cyclopentadienyl)zirconium or zirconocene, (i7-C5H5)2Zr (2), although frequently referred to in the literature, have never actually been isolated as discrete chemical compounds. However, these molecules have been implicated as highly reactive intermediates in a wide variety of chemical reactions with olefins, hydrogen, carbon monoxide, and dinitrogen. In recent years some discrete, well-characterized bis(7j-cyclopenta-dienyl) and bis(Tj-pentamethylcyclopentadienyl) complexes of low-valent titanium and zirconium have been isolated and studied, and it has become possible to understand some of the reasons for the remarkable reactivity of titanocene- and zirconocene-related organometallics toward small unsaturated molecules. 

The concentration theory completely fails to explain the selective nature of catalysis. Why, for example, does formic acid decompose into hydrogen and carbon dioxide with a zinc oxide catalyst, whereas with titanium oxide, it breaks down to carbon monoxide and water Or, to quote another example, why do carbon monoxide and hydrogen form methane in the presence of nickel, whereas quantitative yields of methanol are produced with a zinc chromite catalyst.6... 

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