Description: technologyComment of cyclohexane production (RER, RoW): Over 90 % of all cyclohexane is produced commercially by hydrogenation of benzene. A small amount is produced by superfractionation of the naphtha fraction from crude oil. Naturally occurring cyclohexane can be supplemented by fractionating methylcyclopentane from naphtha and isomerizing it to cyclohexane. Hydrogenation of benzene: Benzene can be hydrogenated catalytically to cyclohexane in either the liquid or the vapor phase in the presence of hydrogen. Several cyclohexane processes, which use nickel, platinum, or palladium as the catalyst, have been developed. Usually, the catalyst is supported, e.g., on alumina, but at least one commercial process utilizes Raney nickel. Hydrogenation proceeds readily and is highly exothermic (Δ H500K = – 216.37 kJ/mol). From an equilibrium standpoint, the reaction temperature should not exceed 300 °C. Above this, the equilibrium begins to shift in favor of benzene so that high-purity cyclohexane cannot be produced. As a result of these thermodynamic considerations, temperature control of the reaction is critical to obtaining essentially complete conversion of benzene to cyclohexane. Temperature control requires economic and efficient heat removal. This has been addressed in a number of ways by commercial processes. The earlier vapor-phase processes used multistage reactors with recycle of cyclohexane as a diluent to provide a heat sink, staged injection of benzene feed between reactors, and interstage steam generators to absorb the exothermic heat of hydrogenation. In the 1970s processes have been developed that use only one reactor or a combination of a liquid-and a vaporphase reactor. The objectives of the later processes were to reduce capital cost and improve energy utilization. However, all of the commercial processes have comparably low capital cost and good energy efficiency. In the vapor-phase process with multistage reactors in series, the benzene feed is divided and fed to each of the first two reactors. Recycled cyclohexane is introduced to the first reactor along with hydrogen. The recycled cyclohexane enables higher conversion in the reactors by absorbing part of the heat of hydrogenation. Steam generators between the reactors remove the heat of hydrogenation. The outlet temperature of the last reactor is controlled to achieve essentially 100 % conversion of benzene to cyclohexane. The effluent from the last reactor is cooled, and the vapor and liquid are separated. Part of the hydrogen-rich vapor is recycled to the first reactor, and the rest is purged to fuel gas or hydrogen recovery facilities. The liquid from the separator goes to a stabilizer where the overhead gas is sent to fuel gas; the remaining material is cyclohexane product, part of which is recycled to the first reactor. In the process with liquid- and vapor-phase reactors, benzene and hydrogen are fed to the liquid-phase reactor, which contains a slurry of finely divided Raney nickel. Temperature is maintained at 180 – 190 °C by pumping the slurry through a steam generator and by vaporization in the reactor. Roughly 95 % of the benzene is converted in this reactor. The vapor is fed to a fixed-bed reactor where the conversion of benzene is completed. The effluent from the fixed-bed reactor is processed as described previously for the vapor-phase process. Benzene hydrogenation is done typically at 20 – 30 MPa. The maximum reactor temperature is limited to ca. 300 °C so that a typical specification of < 500 mg/kg benzene and < 200 mg/kg methylcyclopentane in the product can be achieved. This is necessary because of the thermodynamic equilibrium between cyclohexane – benzene and cyclohexane – methylcyclopentane. Actually, equilibrium strongly favors methylcyclopentane, but the isomerization reaction is slow enough with the catalysts employed to avoid a problem if the temperature is controlled. The hydrogen content of the makeup hydrogen has no effect on product purity but it does determine the makeup, recycle, and purge gas rates. Streams with as low as 65 vol % hydrogen can be used. Carbon monoxide and sulfur compounds are catalyst deactivators. Both can be present in the hydrogen from catalytic naphtha reformers or ethylene units, which are typical sources of makeup hydrogen. Therefore, the hydrogen-containing stream is usually passed through a methanator to convert carbon monoxide to methane and water. Prior to methanation, hydrogen-containing gas can be scrubbed with caustic to remove sulfur compounds. Commercial benzene contains less than 1 mg/kg sulfur. In some cases, the recycle gas is also scrubbed with caustic to prevent buildup of hydrogen sulfide from the small amount of sulfur in the benzene. With properly treated hydrogen and specification benzene, a catalyst life in excess of three years can be achieved easily in fixed-bed reactors that use noble-metal catalysts supported on a base. The catalyst in the process that uses Raney nickel in suspension is reported to have a typical life of about six months before it must be replaced. Reference: Campbell, M. L. 2011. Cyclohexane. Ullmann's Encyclopedia of Industrial Chemistry.
Types:
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Comment: This is a market activity. Each market represents the consumption mix of a product in a given geography, connecting suppliers with consumers of the same product in the same geographical area. Markets group the producers and also the imports of the product (if relevant) within the same geographical area. They also account for transport to the consumer and for the losses during that process, when relevant. This is the market for 'cyclohexane', in the Global geography. Transport from producers to consumers of this product in the geography covered by the market is included. cyclohexane' is an organic substance with a CAS no. : 000110-82-7. It is called 'cyclohexane' under IUPAC naming and its molecular formula is: C6H12. It is liquid under normal conditions of temperature and pressure with a characteristic solvent odour. It is soluble in ether, alcohol and acetone. It is modelled as a pure substance. On a consumer level, is used in the following products: lubricants and greases, anti-freeze products, fuels, adhesives and sealants, coating products, non-metal-surface treatment products, inks and toners, washing & cleaning products, polishes and waxes, air care products, leather treatment products and welding & soldering products. There is no publicly available information about the consumption of this substance on industrial sites. This market is supplied by the following activities with the given share: cyclohexane production, RER: 0.174 cyclohexane production, RoW: 0.826 generalComment of cyclohexane production (RER, RoW): This dataset represents the production of 1 kg of cyclohexane by hydrogenation of benzene. Cyclohexane (C6H12) is a clear liquid with a pungent petroleum-like odor. It is essentially insoluble in water but miscible in most organic liquids, and is noncorrosive, easily flammable, and considered to be much less toxic than benzene. Over 98 % of the cyclohexane produced is used to make nylon intermediates: adipic acid, caprolactam, and hexamethylenediamine, with the first two consuming ca. 95 % of the cyclohexane used in nylon manufacture. Minor miscellaneous uses, such as solvents and polymer reaction diluents, consume the remainder of the cyclohexane produced (Campbell 2011). In this dataset, the raw materials, auxiliaries and energy consumption are modelled with data from literature sources. The emissions are estimated and the infrastructure is included with a default value. References: Sutter, J. (2007) Life Cycle Inventories of Petrochemical Solvents. ecoinvent report No. 22. Swiss Centre for Life Cycle Inventories, Dübendorf, 2007. Campbell, M. L. 2011. Cyclohexane. Ullmann's Encyclopedia of Industrial Chemistry.
Origin: /Bund/UBA/ProBas
Tags: Hirsch ? Aluminiumoxid ? Ethylen ? Brenngas ? Palladium ? Zyklohexan ? Erdöl ? Nickel ? Platin ? Schwefelverbindung ? Schwefelwasserstoff ? Benzol ? Brüden ? Katalysator ? Thermodynamik ? Wasserstoff ? Schwefel ? Flusswasser ? Gasförmiger Stoff ? Festbettreaktor ? Futtermittel ? Kohlenmonoxid ? Methan ? Verfahrenskombination ? Investitionskosten ? Abwasser ? Dampfkessel ? Energienutzung ? Reaktionsgleichgewicht ? Reaktionstemperatur ? Reaktor ? Energieeffizienz ? Manufacture of basic chemicals, fertilizers and nitrogen compounds, plastics and synthetic rubber in primary forms ? Manufacturing ? Manufacture of chemicals and chemical products ? Manufacture of basic chemicals ?
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