Cyclohexene, hydrogenation dehydrogenation

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].

Dehydrogenation and hydrogenation of cyclohexene Hydrogenation of butadiene Dehydrogenation of isopropyl alcohol... 

Consistent with this model It has been shown on platinum (223) that the reaction occurs on the surface covered with a near monolayer of carbonaceous species In an apparently structure-insensitive loanner but that cyclohexene hydrogenation and dehydrogenation reactions proceed on the clean metal surface In a structure sensitive manner and in addition there Is then a striking variation In catalytic behaviour between various crystal surfaces ... 

Caprolactam (world production of which is about 5 million tons) is mostly produced from benzene through three intermediates cyclohexane, cyclohexanone and cyclohexanone oxime. Cyclohexanone is mainly produced by oxidation of cyclohexane with air, but a small part of it is obtained by hydrogenation of phenol. It can be also produced through selective hydrogenation of benzene to cyclohexene, subsequent hydration of cyclohexene and dehydrogenation of cyclohexanol. The route via cyclohexene has been commercialized by the Asahi Chemical Company in Japan for adipic acid manufacturing, but the process has not yet been applied for caprolactam production. 

The effect of microwave irradiation on the catalytic hydrogenation, dehydrogenation, and hydrogenolysis of cyclohexene was studied by Wolf et al. [107]. Optimum conditions for benzene formation were hydrogen flow, N-CaN is-catalyst, atmospheric pressure, and 70 s irradiation time. Cyclohexane was the main product when the irradiation time was 20 s, or in a batch/static system. 

X. Su, K. Y. Rung, J. Lahtinen, Y. R. Shen, G. A. Somorjai, 1-3 and 1-4 cyclohexadiene reaction intermediates in cyclohexene hydrogenation and dehydrogenation on Pt(lll) crystal surface a combined reaction kinetics and surface vibrational spectroscopy study using sum frequency generations, J. Mol. Catal. A 1999, 141, 9-19. 

R. Nassar, J. Hu, J. Palmer, W. Dai, Modeling of cyclohexene hydrogenation and dehydrogenation reactions in a continuous-flow microreactor, Catal. Today 2007, 120, 121-124. 

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. 

Chemical catalysts for transfer hydrogenation have been known for many decades [2e]. The most commonly used are heterogeneous catalysts such as Pd/C, or Raney Ni, which are able to mediate for example the reduction of alkenes by dehydrogenation of an alkane present in high concentration. Cyclohexene, cyclo-hexadiene and dihydronaphthalene are commonly used as hydrogen donors since the byproducts are aromatic and therefore more difficult to reduce. The heterogeneous reaction is useful for simple non-chiral reductions, but attempts at the enantioselective reaction have failed because the mechanism seems to occur via a radical (two-proton and two-electron) mechanism that makes it unsuitable for enantioselective reactions [2 c]. 

The cyclic diolefin formed can then dehydrogenate as was discussed previously for this type of compound, and the hydrogen eliminated may be transferred to -methylstyrene, as was previously discussed for phenyl-cyclohexene, resulting in the formation of cumene. The diaryldiolefin shown in this mechanism was synthesized and successfully cyclized to p-terphenyl in the presence of sodium 55). 

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