Dehydrogenation, using zeolites

Fries rearrangement, 18 336, 337 isomerization and transalkylation of alky-laromatics, 18 329 epoxide transformations, 18 351-352 hydration and ammonolysis of ethylene oxide, 18 351, 352 isomerization, 18 351 framework composition, 33 226-228 hydrogenation, dehydrogenation, and related reactions, 18 360-365 dehydrocyclization of s-ethylphenyl using zeolites and carbonyl sulfide, 18 364, 365... 

Alkylation. Ethylbenzene [100-41-4], the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either in the liquid phase in the presence of a Friedel-Crafts catalyst (A1C13, BF3, FeCl3) or in the vapor phase with a suitable catalyst. The Monsanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeolite catalyst process for liquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process using zeolite catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-3], which is obtained by dehydrogenation in the presence of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

The reformation of lower paraffins to aromatics has been studied for about 20 yr by using zeolite catalysts. Recently, an excellent review was published of lower alkane transformation to aromatics on ZSM-5 zeolites [2]. From the studies of the mechanism of this reaction, it has been suggested that the bifunctional catalysts, having solid acidity and dehydrogenation activity, can effectively promote the aromatization of lower paraffins[3-6]. It has been reported that ZSM-5 and ZSM-11 are excellent solid acid catalysts [7] and the transition metals [8], Ga [9] and Zn [9] show high dehydrogenation activity in this reaction. In the case of bifunctional... 

Using zeolite-supported, Ce-promoted Pd catalysts brought enhanced dehydrogenation activity during a-limonene conversion. Thereby, they used preferably weakly acidic boron-pentasil zeolites and obtained p-cymene yields around 85%. 

Dow has developed a process to dimerize the BD in a crude C4 stream to vinylcyclohexene (VCH) using a proprietary copper-loaded zeolite catalyst. The second step converts VCH to styrene via oxidative dehydrogenation using another proprietary tin/antimony oxide catalyst. 

Frisch H L, Maaref S and Deng-Nemer H (1999), Low-temperature dehydrogenation reaction-separation membrane using zeolite 13 X polyethylacrylate , J Membr Sci, 154,33-40. 

Butane isomerization is usually carried out to have a source of isobutane which is often reacted with C3-C5 olefins to produce alkylate, a high octane blending gasoline [13]. An additional use for isobutane was to feed dehydrogenation units to make isobutene for methyl tert-butyl ether (MTBE) production, but since the phaseout of MTBE as an oxygenate additive for gasoline, this process has decHned in importance. Zeolitic catalysts have not yet been used industriaUy for this transformation though they have been heavily studied (Table 12.1). 

The dehydroaromatization of light alkane feeds (methane to butanes) into aromatics has come into prominence as a method of converting the unreactive light paraffins into useful chemical precursors. In many of the world s markets, light alkanes are very undesired off-gasses which can not be used other than as fuel. To accomplish this difficult transformation, catalysts typically are bifunctional, containing a dehydrogenating component such as Pt, Ga, Zn or Mo with an acidic zeolite. 

In addition to the epoxidation of olefins, zeolitic materials have been studied for other fine chemical transformations. Table 12.21 indexes the zeolites used for oxidative dehydrogenation of propane, direct hydroxylation of benzene to phenol and e-caprolactam synthesis. A recent review summarizes other reactions for which there is not enough space in the table [138, 139]. 

Auroux et al. [251] used adsorption microcalorimetry of different alkanes to investigate Ga and Al substituted MFI zeolites used as catalysts in dehydrogenation and cracking reactions. 

A few pyrolytic methods of synthesis are known, leading directly to the formation of pyridine rings by formation of the /3, y-bond. Alkylpyridines are obtained when unsaturated imines (116) or (117) are passed over heated zeolites (80IZV655) or alumina (72IZV2263). More dehydrogenation is achieved by the use of nickel or alumina, as in the synthesis of tetrahydroquinolines (118) or octahydrophenanthridine (119) (78IZV1446). 

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