Catalytic dehydrogenation of butenes

Butenes are only obtained in mixtures (23 to 45 weight per cent) in cuts containing n-butenes, isobutene, n-butane and isobutane (see Tables 2.11 and 2.28 in Section 2). To achieve a satisfactory return from dehydrogenation operations, the n-butenes concen  

Dehydrogenation takes place according to the following reaction  

These conversions are balanced, endothermic and exentropic. The formation of butadiene is favored at elevated temperature and low pressure. 

In practice, industrial processes operate in the presence of catalysts, at above 600 C with a large adduct of steam, whose effect is to reduce the partial pressure of the hydrocarbons and also to slow down the formation of coke. Depending on the extent of this coking, the process may require operation in cles, with a frequency proportional to the amount of coke deposited. Table 6.1 gives typic examples of operating conditions and results obtained with several catalysts. 

PERFORAtANCE ACHIEVED BY DIFFEXE r CATALYSTS IN THE DEHYDROGENATION OP BinENES 

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Butadiene. Although butadiene was produced in the United States in the eady 1920s, it was not until the start of Wodd War 11 that significant quantities were produced to meet the war effort. A number of processes were investigated as part of the American Synthetic Rubber Program. Catalytic dehydrogenation of / -butenes and / -butanes (Houdry process) and thermal cracking of petroleum hydrocarbons were chosen (12). 

Coke formation during the catalytic dehydrogenation of butene-1 has been studied in the temperature range 525-600 °C at butene-1 partial pressures of 0.05 to 0.25 bars. Moderate levels of coke deposits led to blocking of the catalyst mesopores and a hyperbolic deactivation function was found to provide the best fit to the data. Increase of temperature caused the deactivation to change from a parallel to a series coking process. 

Derivation (1) Catalytic dehydrogenation of butenes or butane (2) oxidative dehydrogenation of butenes. 

Catalytic dehydrogenation of butenes is an important industrial process for preparation of butadiene.102... 

Butadiene and Butylenes. Although the first commercial butadiene was obtained as a by-product in the manufacture of ethylene (Tables 20-3 and 20-7) and much of the butadiene produced during the rubber crisis of World War II was obtained in this manner or from alcohol, later in the war butadiene was made by the catalytic dehydrogenation of butenes. 

In the petroleum (qv) industry hydrogen bromide can serve as an alkylation catalyst. It is claimed as a catalyst in the controlled oxidation of aHphatic and ahcycHc hydrocarbons to ketones, acids, and peroxides (7,8). AppHcations of HBr with NH Br (9) or with H2S and HCl (10) as promoters for the dehydrogenation of butene to butadiene have been described, and either HBr or HCl can be used in the vapor-phase ortho methylation of phenol with methanol over alumina (11). Various patents dealing with catalytic activity of HCl also cover the use of HBr. An important reaction of HBr in organic syntheses is the replacement of aHphatic chlorine by bromine in the presence of an aluminum catalyst (12). Small quantities of hydrobromic acid are employed in analytical chemistry. 

Butadiene is obtained mainly as a coproduct with other light olefins from steam cracking units for ethylene production. Other sources of butadiene are the catalytic dehydrogenation of butanes and butenes, and dehydration of 1,4-butanediol. Butadiene is a colorless gas with a mild aromatic odor. Its specific gravity is 0.6211 at 20°C and its boiling temperature is -4.4°C. The U.S. production of butadiene reached 4.1 billion pounds in 1997 and it was the 36th highest-volume chemical. ... 

Butadiene could also be produced by the catalytic dehydrogenation of butanes or a butane/butene mixture. 

Butadiene (> 98%w/w) 20 ooo longtons Catalytic dehydrogenation of n-butenes feedstock of liquid mixed hydrocarbon stream containing 80.5 mol % n-butenes, 11.5 mol % n-butane, and 1 mol % of higher hydrocarbons. 

A process for the production of 1,3-butadiene results from the catalytic dehydrogenation of 1-butene according to the reaction... 

The dehydrogenation process feed can be refinery streams from the catalytic cracking processes. This mixed C4 stream typically contains less than 20 percent n-butenes. For use in dehydrogenation, however, it should be concentrated to 80-95 percent. The isobutylene generally is removed first by a selective extraction-hydration process. The n-butenes in the raffinate are then separated from the butanes by an extractive distillation. The catalytic dehydrogenation of n-butenes to 1,3-butadiene is carried out in the presence of steam at high temperature (>600°C) and... 

Butadiene (1,3-butadiene) is manufactured in the petroleum industry by the catalytic dehydrogenation of the butanes and butenes, and by the direct cracking of naphthas and light oils. The overall butadiene yield by catalytic dehydrogenation, the most common industrial process, is as high as about 80% at selectivities of about 90%. The yields and selectivities of butadiene by... 

Paraffin dehydrogenation for the production of olefins has been in use since the late 1930s. During World War II, catalytic dehydrogenation of butanes over a chro-mia-alumina catalyst was done for the production of butenes that were then dimerized to octenes and hydrogenated to octanes to yield high-octane aviation fuel. 

This article therefore seeks to examine in depth just one mixed oxide catalyst, tin-antimony oxide, which has been commercially developed (2-5) for the oxidation of propylene to acrolein as well as for the ammoxidation of propylene to acrylonitrile and the oxidative dehydrogenation of butenes to 1,3-butadiene. A recent book (6) and a subsequent review (7) have shown how little unanimity has been established about the fundamental properties of the material. In particular there seems to be much confusion as to the phase composition, the nature of the cationic oxidation states, the chemical environment of the cations, the charge compensation mechanism, the nature of the active sites, the distortion of the host tin(IV) oxide lattice by the dopant antimony atoms and whether any changes in the catalyst result from the adsorption and catalytic processes. 

However, as with other aspects of this catalyst, there is little unanimity as to the significance of specific cationic oxidation states in the formation of active sites. Indeed, Roginskaya et al. (11) reported that the catalytic activity for the oxidative dehydrogenation of butenes and ammoxidation of... 

The catalytic dehydrogenation of 1-butene gives 1,3-butadiene,12 which can be dimerized to 4-vinyl-1-cyclo-hexene by a copper(I)-containing zeolite, with over 99% selectivity.13 This material is converted to styrene by catalytic oxidation with oxygen in the presence of steam... 

The dehydrogenation of butene to butadiene over a 20% chrome on alumina catalyst is an important industrial process. This catalytic reaction, that is deactivated by coke deposition, has been extensively studied by Froment et al. [10,11]. Faccio et al. [7] have simulated this process using a site-bond-site model on a Bethe network. 

Butadiene is a petroleum product obtained by catalytic cracking of naphtha or light oil or by dehydrogenation of butene or butane. It is used to produce butadiene-styrene elastomer (for tires), synthetic rubber, thermoplastic elastomers, food wrapping materials, and in the manufacture of adiponitrile. It is also used for the synthesis of organics by Diels-Alder condensation. 

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