Olefins dehydrogenation

Recently alkali metals or compounds of alkali metals were found to act as catalysts for reactions, such as isomerization of olefins, dehydrogenation... 

Further transformations of these intermediates lead to either olefins (dehydrogenation) or branched alkanes (isomerization). However, usually heterogeneous processes are not highly selective and afford simultaneously products of dehydrogenation and isomerization (as well as of other reactions, e.g., cracking and condensation). 

The final, dried product is obtained in the form of shining, vitreous, jet-black particles of the proper size for direct use in experimental -catalytic reactors. The gel exhibits catalytic activity in several diverse reactions, for example, dehydration of silcohols, hydrogenation of olefins, dehydrogenation of paraffins, especially gaseous paraflSns, and aromatization of paraffins containing six or more carbon atoms in a straight chain. The material prepared as described is appreciably more active than that made by... 

Buyanov RA, Pakhomov NA (2001) Catalysts and processes for paraffin and olefin dehydrogenation. Kinet Catal 42 72-85... 

Naphthenes Crack to olefins. Dehydrogenate to cyclic olefins. Isomerize to smaller rings. Furdier dehydrogenation to aromatics, by hydrogen transfer. 

Aromatics Alkyl groups crack at ring to form olefins. Dehydrogenation and condensation to polyaromatics. Furdier dehydrogenation and condensation forms coke. 

Similarly, the catalytic behavior of hydrogen forms of zeolites in methanol conversion was completely changed upon loading with 263 via RSSIE. Instead of acid-catalyzed selective dehydration to olefins, dehydrogenation became predominant resulting in products such as H2, CO, CO2 and CH4 [260]. 

J Olefin Syntheses by Dehydrogenation and Other Elimination Reactions 137... 

Olefin—Paraffin Separation. The catalytic dehydrogenation of / -paraffins offers a route to the commercial production of linear olefins. Because of limitations imposed by equiUbrium and side reactions, conversion is incomplete. Therefore, to obtain a concentrated olefin product, the olefins must be separated from the reactor effluent (81—85), and the unreacted / -paraffins must be recycled to the catalytic reactor for further conversion. 

About 35% of total U.S. LPG consumption is as chemical feedstock for petrochemicals and polymer iatermediates. The manufacture of polyethylene, polypropylene, and poly(vinyl chloride) requires huge volumes of ethylene (qv) and propylene which, ia the United States, are produced by thermal cracking/dehydrogenation of propane, butane, and ethane (see Olefin polymers Vinyl polymers). 

Toluene reacts with carbon monoxide and butene-1 under pressure in the presence of hydrogen fluoride and boron trifluoride to give 4-methyl-j iYbutyrophenone which is reduced to the carbinol and dehydrated to the olefin. The latter is cycHzed and dehydrogenated over a special alumina-supported catalyst to give pure 2,6- dim ethyl n aph th a1 en e, free from isomers. It is also possible to isomerize various dim ethyl n aph th a1 en es to the... 

HP Alkylation Process. The most widely used technology today is based on the HE catalyst system. AH industrial units built in the free world since 1970 employ this process (78). During the mid-1960s, commercial processes were developed to selectively dehydrogenate linear paraffins to linear internal olefins (79—81). Although these linear internal olefins are of lower purity than are a olefins, they are more cost-effective because they cost less to produce. Furthermore, with improvement over the years in dehydrogenation catalysts and processes, such as selective hydrogenation of diolefins to monoolefins (82,83), the quaUty of linear internal olefins has improved. 

Antimony tetroxide finds use as an oxidation catalyst, particularly for the dehydrogenation of olefins. 

The mechanistic steps are as follows paraffins dehydrogenate to olefins the olefins oligomerize and cyclize and the cycHcs aromatize. Because the first step is rate controlling, very Httie olefin is actually present. The BTX product is relatively free of nonaromatics and therefore is very desirable as a chemical feed. As in reforming, some C —C2 fuel gas is produced along with a valuable hydrogen stream. Prom a C —feed the BTX product is roughly 35 45 20, respectively. 

Dehydrogenation of isobutane to isobutylene is highly endothermic and the reactions are conducted at high temperatures (535—650°C) so the fuel consumption is sizeable. Eor the catalytic processes, the product separation section requires a compressor to facHitate the separation of hydrogen, methane, and other light hydrocarbons from-the paraffinic raw material and the olefinic product. An exceHent overview of butylenes is avaHable (81). 

The various sources of isobutylene are C streams from fluid catalytic crackers, olefin steam crackers, isobutane dehydrogenation units, and isobutylene produced by Arco as a coproduct with propylene oxide. Isobutylene concentrations (weight basis) are 12 to 15% from fluid catalytic crackers, 45% from olefin steam crackers, 45 to 55% from isobutane dehydrogenation, and high purity isobutylene coproduced with propylene oxide. The etherification unit should be designed for the specific feedstock that will be processed. 

A second route based on olefin disproportionation was developed by Phillips Petroleum (131). Here isobutylene reacts with propylene to form isoamylenes, which are dehydrogenated to isoprene. 2-Butene can be used in place of propylene since it also yields isoamylene and the coproduct propylene can be recycled. Use of mixed butylenes causes the formation of pentenes, giving piperjlene, which contaminates isoprene. 

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