Dehydrogenation cyclohexene

Figure 9.2 Variation of the rate of cyclohexene dehydrogenation to benzene with gold coverage at Pt(100) at 373 K. (Reproduced from Ref. 8).

Fig. 26. Cyclohexene dehydrogenation to benzene as a function of (a) step density and (b) kink density. Standard reaction conditions.

Cyclohexene can also be oxidized in cyclohexene-2-one which is hydrated into cyclohexan-l-ol-3-one. Dehydrogenation of this compound gives resorcinol selectively (57). 

The condensation of cyclohexanol or cyclohexene is generally carried out in the presence of phosphoric acid, pyrophosphoric acid, or HY 2eohtes the aromatization of intermediate cyclohexyUiydroquinone [4197-75-5] (19) is realized in the presence of a dehydrogenation catalyst. 

Phenol Vi Cyclohexene. In 1989 Mitsui Petrochemicals developed a process in which phenol was produced from cyclohexene. In this process, benzene is partially hydrogenated to cyclohexene in the presence of water and a mthenium-containing catalyst. The cyclohexene then reacts with water to form cyclohexanol or oxygen to form cyclohexanone. The cyclohexanol or cyclohexanone is then dehydrogenated to phenol. No phenol plants have been built employing this process. 

In the Monsanto/Lummus Crest process (Figure 10-3), fresh ethylbenzene with recycled unconverted ethylbenzene are mixed with superheated steam. The steam acts as a heating medium and as a diluent. The endothermic reaction is carried out in multiple radial bed reactors filled with proprietary catalysts. Radial beds minimize pressure drops across the reactor. A simulation and optimization of styrene plant based on the Lummus Monsanto process has been done by Sundaram et al. Yields could be predicted, and with the help of an optimizer, the best operating conditions can be found. Figure 10-4 shows the effect of steam-to-EB ratio, temperature, and pressure on the equilibrium conversion of ethylbenzene. Alternative routes for producing styrene have been sought. One approach is to dimerize butadiene to 4-vinyl-1-cyclohexene, followed by catalytic dehydrogenation to styrene ... 

Intrinsic Selectivity to Benzene During Cyclohexene Hydrogenation- Dehydrogenation is Sensitive to Pt Particle Size... 

Table 6. Cyclohexene hydrogenation-dehydrogenation rates on Pt/SBA-15 nanoparticle encapsulation catalyst series [18].

Figure 15. Turnover rate for cyclohexene hydrogenation and dehydrogenation as a function of particle size. Reaction conditions are lOTorr CeHio, 200 Torr H2, and 310K for hydrogenation and 448 K for dehydrogenation, respectively [18].

Cyclohexadiene and benzene form identical structures on Pt(l 1 1) at low pressures (Figures 7.23 and 7.24). 1,3-Cyclohexadiene dehydrogenates to form benzene on the surface, while benzene adsorbs molecularly. Figure 7.24b schematically shows the adsorbed benzene structure at low pressure. The STM images of the C6 cyclic hydrocarbons show three different adsorbed structures on Pt(l 1 1). Cyclohexene and cyclohexane partially dehydrogenate to form rc-allyl, 1,4-cyclohexadiene adsorbs in a boat configuration, and both 1,3-cylohexadiene and benzene adsorb as molecular benzene on the surface. 

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