Vapor-Phase Hydrogenation

The vapor-phase hydrogenation of coal is actually (as intended here) the direct reaction between hydrogen and coal withont a vehicle. The reaction may require higher temperatures or may proceed at lower pressures than those employed for the liquid-phase hydrogenation of coal. 

Obviously, the nature of the reaction under these conditions will differ from the reaction in the presence of a carrier insofar as there is a direct reaction between the hydrogen and the coal. In addition, vapor-phase (or secondary) hydrogenation may also follow the primary hydrogenation in which volatile products from the decomposition of the coal or from the reaction of the coal with hydrogen then react with more hydrogen to modify the slate of primary reaction products. 

In hydrogasification reactions, the conversion to methane is favored by high pressures and by temperatures at the lower end of the range. The reaction is rapid at temperatures above 480°C (900°F) and while the original coal is usually more reactive than the char produced, it may appear paradoxical that the char can often be converted to methane more easily than coal. There are also reports that sodium carbonate can increase the rate of the reaction of coal with hydrogen in the range 815°C-900°C (1500°F-1650°F). However, for those catalysts that are added to the reaction mix as a powder, tin(II) chloride has been noted as having exceptionally beneficial effects. 

On the other hand, for catalysts that are added to the reaction mix by means of solntion impregnation of the coal, ammonium molybdate, tin(II) chloride, nickel(II) chloride, and iron(II) snlfate have been noted to be beneficial. 

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Manufacture. Furfuryl alcohol has been manufactured on an industrial scale by employing both Hquid-phase and vapor-phase hydrogenation of furfural (56,57). Copper-based catalysts are preferred because they are selective and do not promote hydrogenation of the ring. 

Catalytic hydrogenation of furan to tetrahydrofuran is accompHshed in either Hquid or vapor phase. Hydrogenation of the double bonds is essentially quantitative over nickel catalysts but is generally accompanied by hydrogenolysis over the noble metals. 

Reduction. Acetaldehyde is readily reduced to ethanol (qv). Suitable catalysts for vapor-phase hydrogenation of acetaldehyde are supported nickel (42) and copper oxide (43). The kinetics of the hydrogenation of acetaldehyde over a commercial nickel catalyst have been studied (44). 

V-Alkyl or A/-aryl succinimides can be prepared from the corresponding amines (107) or from succinic anhydride, ammonia, and the corresponding alcohol (108). Succinimides are also obtained by vapor-phase hydrogenation of the corresponding maleimides ia the presence of a catalyst (109). 

Silva (1971) used the Berty reactor to execute exploratory measurements on vapor-phase hydrogenation of organic substrates that had little vapor pressure at room temperature. The substrate was measured by weight in a small ceramic boat and put on the catalyst screen beside a few particles of catalyst, also measured by weight. Then the stirring started, and the autoclave was heated to the reaction temperature. Finally the desired hydrogen pressure was applied suddenly and the reaction started. 

Valedyne differential pressure cell. 91 vapor phase hydrogenation... 

Oldenberg and Rase (13) have studied the catalytic vapor phase hydrogenation of pro-pionaldehyde over a commercially supported nickel catalyst. Their data indicate that the mathematical form of the reaction rate at very low conversions and 150 °C can be expressed quite well in the following manner. 

Oldenburg and Rase AIChE J., 3 (462), 1957] studied the catalytic vapor phase hydrogenation of propionaldehyde by making low conversion runs on a commercial supported... 

Korbach and Stewart [Ind. Eng. Chem. Fundamentals, 3 (24), 1964] have studied the vapor phase hydrogenation of benzene in a batch recycle reactor. 

Aniline is an aromatic amine used in the manufacture of dyes, dye intermediates, rubber accelerators, and antioxidants. It has also been used as a solvent, in printing inks, and as an intermediate in the manufacture of pharmaceuticals, photographic developers, plastics, isocyanates, hydroquinones, herbicides, fungicides, and ion-exchange resins. It is produced commercially by catalytic vapor phase hydrogenation of nitrobenzene (Benya and Cornish 1994 HSDB 1996). Production of aniline oil was listed at approximately 1 billion pounds in 1993 (U.S. ITC 1994). Chemical and physical properties are listed in Table 1-2. 

Nakahira, K. Validation of deep vacuum vapor phase hydrogen peroxide sterilizer retrofit to a production lyophilizer. PDA Asian Symposium, p. 1/6-6/6, Tokyo 1994... 

C. The Detection of Cyclohexene Intermediates The postulate that olefins are released from the surface during the hydrogenation of aromatic hydrocarbons has gained considerable support. Madden and Kemball (89) observed cyclohexene during the early stages of the vapor phase hydrogenation (flow system) of benzene over nickel films at 0° to 50°. The ratio of cyclohexene to cyclohexane diminished with time, and little or none of the alkene was detected if the films were annealed at 50° in a stream of hydrogen. 

Vapor Phase Hydrogenation of Acetic Anhydride Acetic anhydride was pumped into an evaporator where it was mixed with hydrogen. The temperature of anhydride-hydrogen mixture was raised to the reaction temperature in a preheater zone, made of a 2 feet bed packed with 2 mm glass beads. The reaction took place in a 2 feet catalyst bed packed with 1 m.m. alpha-alumina coated with 0.5% Pd. The effluent was condensed and analyzed by G.C. 

Reduction. Benzene can be reduced to cyclohexane [110-82-7], C5H12, or cycloolefins. At room temperature and ordinary pressure, benzene, either alone or in hydrocarbon solvents, is quantitatively reduced to cyclohexane with hydrogen and nickel or cobalt (14) catalysts. Catalytic vapor-phase hydrogenation of benzene is readily accomplished at about 200°C with nickel catalysts. Nickel or platinum catalysts are deactivated by the presence of sulfur-containing impurities in the benzene and these metals should only be used with thiophene-free benzene. Catalysts less active and less sensitive to sulfur, such as molybdenum oxide or sulfide, can be used when benzene is contaminated with sulfur-containing impurities. Benzene is reduced to 1,4-cydohexadiene [628-41-1], C6HS, with alkali metals in liquid ammonia solution in the presence of alcohols (15). 

VII. VALIDATION OF VAPOR PHASE HYDROGEN PEROXIDE STERILIZATION PROCESS... 

Vapor phase hydrogen peroxide equipment and process are described elsewhere [36]. The basic steps in the process are dehumidification, conditioning, sterilization, and aeration. More specifically, there are five steps that must be part of the validation protocol [36]. 

Vapor-phase hydrogenation using a fixed-bed catalyst for the conversion of middle oil into gasoline whereby the middle oil was vaporized under pressure in a stream of hydrogen. 

Vapor-phase hydrogenation without a catalyst is impractical the influence of the catalyst on rate and direction of the reaction is by far... 

Vapor-phase hydrogenation results and experimental evidence of this type lead to the conclusion that catalysts on basic supports are suitable for nonsplitting prehydrogenation-type reactions and that acidic supports are best used for splitting catalysts. Activated alumina was found to be the best support because of rapid reduction of tar acids. Especially, alumina precipitated from aluminum salts at constant pH was satisfactory and produced catalysts that could be formed into pellets of high mechanical strength. 

A more modern process involves the use of maleic anhydride as the starting material. In the process (Fig. 1), maleic anhydride is first esterified with methanol and the ester is fed to a low-pressure vapor-phase hydrogenation system where it is converted to butanediol. 

Although the hydrogenation of hydrogen cyanide to methylamine was achieved as early as 1863 (Debus, 1), the history of modern catalytic hydrogenation began in 1897 with the discovery by Paul Sabatier and R. Senderens of the vapor phase hydrogenation of unsaturated compounds over a nickel catalyst (Sabatier and Senderens, 2). Sabatier has said that his interest in the action of nickel was provoked by the newly discovered Mond process for the purification of nickel by the formation and decomposition of nickel carbonyl. The capacity of nickel... 

Cyclohexane. Cyclohexane is the basic starting material for nylon fibers and resins via the intermediates adipic acid, caprolactam, and hexamethylenediamine. The world consumption was about 10 billion lb (with 3.5 billion lb in the United States) in 2000. Of these three derivatives, adipic acid and caprolactam account for over 90 percent of cyclohexane consumption. Cyclohexane is also used as a solvent and as a starting material for cyclohexanol and cyclohexanone. Although cyclohexane can be recovered from natural gasoline, most is made by liquid or vapor-phase hydrogenation of benzene. A nickel or platinum catalyst is generally used at elevated temperature and pressure. 

Shore, S. G., Ding, E. R., Park, C., and Keane, M. A., Vapor phase hydrogenation of phenol over silica supported Pd and Pd-Yb catalysts. Catalysis Commun 2002, 3 (2), 77-84. 

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