Butane, oxidative dehydrogenation catalysts

Effects of cesium doping on the kinetics and mechanism of the n-butane oxidative dehydrogenation over nickel molybdate catalysts... 

The reaction scheme is rather complex also in the case of the oxidation of o-xylene (41a, 87a), of the oxidative dehydrogenation of n-butenes over bismuth-molybdenum catalyst (87b), or of ethylbenzene on aluminum oxide catalysts (87c), in the hydrogenolysis of glucose (87d) over Ni-kieselguhr or of n-butane on a nickel on silica catalyst (87e), and in the hydrogenation of succinimide in isopropyl alcohol on Ni-Al2Oa catalyst (87f) or of acetophenone on Rh-Al203 catalyst (87g). Decomposition of n-and sec-butyl acetates on synthetic zeolites accompanied by the isomerization of the formed butenes has also been the subject of a kinetic study (87h). 

O-X-D [Oxidative dehydrogenation] A process for converting n-butane to butadiene by selective atmospheric oxidation over a catalyst. Developed by the Phillips Petroleum Company and used by that company in Texas from 1971 to 1976. See also Oxo-D. 

Rives et al. reported the use of Mg/V mixed oxides obtained from V(III)-substituted LDH precursors as catalysts for the oxidative dehydrogenation of propane and -butane [71]. Their results indicated that the relative amounts of Mg3V04 and MgO, which depend on the V(III) content of the starting LDHs, determine the performance of the catalysts. 

The data in Figs. 3 and 4 show that the ease of removal of a lattice oxygen, which can also be expressed in terms of the reducibility of the neighboring cations, has a strong effect on the selectivity for oxidative dehydrogenation of butane. If this is the only factor that determines selectivity, then a catalyst that is selective for dehydrogenation of butane, such as Mg3(V04)2, will be selective for other alkanes as well. Likewise, any catalyst that contains bonds will not be... 

Other catalysts for alkane oxidative dehydrogenation have also been reported in the patent literature. For example, it was claimed that a Na and Li phosphomolybdate produced 17% butadiene and 5% butenes at 600°C with a 1 1 mixture of butane and oxygen (13). 

There are fewer studies of oxidative dehydrogenation of butane, and even fewer for cyclohexane than ethane or propane. The performance of the better catalysts in these two reactions are summarized in Table VII and Fig. 5. Because of the larger number of secondary carbon atoms in these molecules, they are more reactive with gaseous oxygen than the smaller alkanes. In ex-... 

As to the method of preparation, it was found that V-Mg oxide catalysts prepared with a Mg(OH)2 precursor that was precipitated with KOH was less selective than one prepared with a MgC03 purecursor precipitated with (NH4)2C03 (25). Interestingly, unlike the butane reaction, there was no effect of preparation on the oxidative dehydrogenation of propane using the same catalysts, as mentioned earlier (25, 30). Unlike the oxidation of propane, Mg pyrovanadate was nonselective for butane (25, 26). Mg metavanadate was nonselective as well (26). 

The additional requirement of the size of molecule with respect to the V — V distance in the active site is perhaps the reason behind the fact that propane and butane show not only different selectivity behavior, but also different dependence of the selectivity on the reducibility of the catalyst the selectivity for dehydrogenation in butane oxidation decreases rapidly with increasing reducibility of the catalyst (Figs. 6 and 7), but the selectivity in propane oxidation is much less dependent on it (31). 

Spinel oxides with a general formula AB2O4 (i.e. the so-called normal spinels) are important materials in industrial catalysis. They are thermally stable and maintain enhanced and sustained activities for a variety of industrially important reactions including decomposition of nitrous oxide [1], oxidation and dehydrogenation of hydrocarbons [2], low temperature methanol synthesis [3], oxidation of carbon monoxide and hydrocarbon [4], and oxidative dehydrogenation of butanes [5]. A major problem in the applications of this class of compound as catalyst, however, lies in their usually low specific surface area [6]. 

Dehydrogenation Catalysts are used to remove hydrogen from hydrocarbons. Many catalysts have been developed, including metals and oxides. An example uf the latter is chromia-alumina used in the dehydrogenation of butane. 

Solid heteropoly compounds are suitable oxidation catalysts for various reactions such as dehydrogenation of O- and N-containing compounds (aldehydes, carboxylic acids, ketones, nitriles, and alcohols) as well as oxidation of aldehydes. Heteropoly catalysts are inferior to Mo-Bi oxide-based catalysts for the allylic oxidation of olefins, but they are much better than these for oxidation of methacrolein (5). Mo-V mixed-oxide catalysts used commercially for the oxidation of acrolein are not good catalysts for methacrolein oxidation. The presence of an a-methyl group in methacrolein makes the oxidation difficult (12). The oxidation of lower paraffins such as propane, butanes, and pentanes has been attempted (324). Typical oxidation reactions are listed in Table XXXI and described in more detail in the following sections. 

Butadiene (1,3-butadiene, boiling point -4.4°C, density 0.6211, flash point -85°C) is made by steam cracking and by the dehydrogenation of butane or the butenes using an iron oxide (Fe203) catalyst. 

Supported vanadium catalysts, whereby vanadium oxide is dispersed on a support such as alumina or titania are of particular importance in, for instance, the oxidative dehydrogenation of alkanes [58-64]. Such materials have attracted considerable interest in the direct dehydrogenation of butane, where a key driver is to identify the relationship between catalytic activity and structural properties [5, 6, 65-68]. In the pure (solid) metal oxides the coordination of vanadium is well defined. However, this is not necessarily true in the case of supported catalysts. Vanadium may be present on the support surface as isolated vanadium ions dimeric or polymeric species one- and two-dimensional chains of vanadium ions ... 

The sol-gel synthesis of a V205-Si02 catalyst and its application in the oxidative dehydrogenation of w-butane to give CO, CO2 or dehydrogenated compounds was described by Sham and coworkers using V(acac)3 and Si(OEt)4 (teos) as precursors. Calcination at 500 °C resulted in the formation of a solid with a high surface area, which allows a better dispersion of active species. Furthermore, a direct correlation between the catalytic activity and the Bronsted acidity was also observed. 

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