Hydrogen diffusion into benzene

Cyclohexane, produced from the partial hydrogenation of benzene [71-43-2] also can be used as the feedstock for A manufacture. Such a process involves selective hydrogenation of benzene to cyclohexene, separation of the cyclohexene from unreacted benzene and cyclohexane (produced from over-hydrogenation of the benzene), and hydration of the cyclohexane to A. Asahi has obtained numerous patents on such a process and is in the process of commercialization (85,86). Indicated reaction conditions for the partial hydrogenation are 100—200°C and 1—10 kPa (0.1—1.5 psi) with a Ru or zinc-promoted Ru catalyst (87—90). The hydration reaction uses zeotites as catalyst in a two-phase system. Cyclohexene diffuses into an aqueous phase containing the zeotites and there is hydrated to A. The A then is extracted back into the organic phase. Reaction temperature is 90—150°C and reactor residence time is 30 min (91—94). 

The hydrocarbon can also be made at room temperature by passing hydrogen into liquid benzene in which is suspended platinum-black prepared by reducing an aqueous solution of platinic chloride with formaldehyde in the presence of sodium hydroxide. Hexamethylene melts at 6.4° and boils at 80°. The hydrocarbon resembles methane in its behavior with halogens. It reacts energetically with chlorine in diffused light, and substitution-products are formed, from which chlorohexamethylene may be separated by fractional distillation. Hexamethylene, like hexane, is not readily attacked by sulphuric acid or nitric acid. 

Common impurities include those formed in reformate fuel streams (carbon oxides (COx), methane (CH4), hydrogen sulfide (H2S), and ammonia (NH3)), pollutants found in air (sulfur oxides (SOJ, nitrogen oxides (NOJ, ammonia (NH3), and organic compounds (propane, benzene, toluene)), catalyst fines carryover, rust from piping, salts, and dust. Impurities may adsorb onto the Pt surface (CO, H2S, SO, and CP), carbon support (H2S and SOJ, or gas diffusion layers (salts, dust, and organic compounds), and adsorb into the ionomer (silica, cations (M+), NH4" ), or simply plug up the flow passages. 

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