Cyclohexane production

Adipic acid is a very large volume organic chemical. Worldwide production in 1986 reached 1.6 x 10 t (3.5 x 10 lb) (158) and in 1989 was estimated at more than 1.9 x 10 t (Table 7). It is one of the top fifty (159) chemicals produced in the United States in terms of volume, with 1989 production estimated at 745,000 t (160). Growth rate in demand in the United States for the period 1988—1993 is estimated at 2.5% per year based on 1987—1989 (160). Table 7 provides individual capacities for U.S. manufacturers. Western European capacity is essentially equivalent to that in the United States at 800,000 t/yr. Demand is highly cycHc (161), reflecting the automotive and housing markets especially. Prices usually foUow the variabiUty in cmde oil prices. Adipic acid for nylon takes about 60% of U.S. cyclohexane production the remainder goes to caprolactam for nylon-6, export, and miscellaneous uses (162). In 1989 about 88% of U.S. adipic acid production was used in nylon-6,6 (77% fiber and 11% resin), 3% in polyurethanes, 2.5% in plasticizers, 2.7% miscellaneous, and 4.5% exported (160). 

In the presence of benzophenone, (8) was again the major product (>95°/0) and only trace amounts of the cyclohexane products were produced. These results suggest the intermediacy of a singlet 1,6-hexylene biradical in the direct photolysis and a longer lived triplet 1,6-diradical in the sensitized photolysis. In the triplet biradical more time is available for 1,6-hydrogen transfer to occur prior to spin inversion and hence more olefin (8) is produced. Similar results were reported for the direct and photosensitized photolysis of the 3,8-dimethyl derivative of (7). 

Figure 5.2-44. Cyclohexane production-UOP process (after Chauvel et al. [63]).

Adipic acid is a very large-volume organic chemical. It is one of the top 50 chemicals produced in the United States in terms of volume. Demand is highly cyclic, reflecting the automotive and housing markets especially. Prices usually follow the variability in crude oil prices. Adipic acid for nylon takes about 60% of U.S. cyclohexane production the remainder goes to caprolactam for nylon-6, export, and miscellaneous uses. 

HDA1—hydrodealkylation of toluene to produce benzene CYHEX1—cyclohexane production by hydrogenation of benzene STYR1—styrene production from ethylbenzene XYL1—production of m-xylene from toluene... 

AhydH was measured in n-hexane solution. The sequence -28.5, -27, and -22.5 for Ahyd7/ of cyclohexene, cyclopentene, and 1,2-dimethylcyclopentene shows the influence of hydrogen atom crowding in the cyclopentane ring relative to cyclohexane (product destabilization) and reactant stabilization of the double bond in 1,2-dimethylcyclohexene by two a methyl groups. 

Reactor operating conditions are 20-30 atm (300-400 psig) and 300-350°C (570-660 F). The temperature is established to ensure a maximum of 500 ppm benzene and typically 2(X) ppm methylcyclopentane in the cyclohexane product. 

Aniline is the second largest petrochemical use of gaseous hydrogen. About half as much hydrogen is used for aniline as for cyclohexane production. Approximately 80% of the aniline produced worldwide is used in the manufacture of MDI for polyurethanes. The balance is used for rubber processing chemicals, agricultural chemicals, dyes, pigments, pharmaceuticals, and specialty polymers. DuPont s aromatic polyamide fiber Kevlar is also derived from aniline [1). 

In these ring-opening processes, the nucleophile attacks from the backside of the carbon-heteroatom bond in typical S 2 maimer. This has important stereochemical consequences, which are best illustrated with cycMc derivatives. Thus, from the bicycMc compound 10.2, where an aziridine ring is fused to cyclohexane, the amino and nucleophile groups will have the trans orientation in the cyclohexane product, as diagrammed in Scheme 10.3. 

The criteria for benzene purity are mainly set by its use for cyclohexane production by hydrogenation. For this application, a low sulfur content is especially important, because of the possibility of catalyst poisoning. 

Cyclohexane production requires large quantities of hydrogen. In both the United States and Europe, hydrogen is also needed for the desulfurization of diesel fuel and gasoline. 

About 60% of cyclohexane production is used to make adipic acid and hexamethyl-ene diamine for nylon-6,6 production, as well as the caprolactam for nylon-6 production. About 70% of all caprolactam is produced from cyclohexane (mainly used to synthesize nylon-6). 

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