Direct catalytic dehydrogenation

Butadiene obtained by dehydrojgenatioii still accounted for one-fifth of world output in 1981, but. by 1990. it appears that this synthesis method will ha e virtually disappeai The operadon was first carried out on butenes, and then on butane in two steps with passage through the intermediary of butenes, and finally in a single step. 

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The processes discussed above are for the direct catalytic dehydrogenation of paraffins to the corresponding olefins or of olefins to diolefins. Other methods have also been considered, although none has reached the level of commercialization. Some of the most notable are ... 

As a result of the high heat transfer performance, rapid heating and cooling of fluids in open reactor systems becomes possible. Reaction mixtures can be efficiently quenched to avoid consecutive decomposition of reactive intermediates in sequential reactions. A practical example is the direct catalytic dehydrogenation of methanol to formaldehyde at a temperature of about 700 °C (Equation (1)) [5-7] ... 

Significant progress has been made in the direct catalytic dehydrogenation of higher normal paraffins to linear olefins, and further developments in this area of technology are likely to occur in the future. 

Geminox A direct process for converting butane to 1,4-butanediol. The butane is first oxidized in the gas phase to maleic anhydride, using BP s fluidized bed technology. The maleic anhydride is scrubbed with water and then catalytically dehydrogenated to butanediol. Developed in 1994 by BP Chemicals and Lurgi. Modifications of the process can be used to make tetrahydrofiuan and y-butyrolactone. The first plant will probably be built on BP s site at Lima, OH, for completion in 2000. 

Processes that enable direct catalytic C-C functionalization of carbinol C-H bonds are highly uncommon. Rh-catalyzed alcohol-vinylarene C-C coupling has been described. The requirement of BF3 and trends in substrate scope suggest these processes involve alcohol dehydrogenation-reductive Prins addition [26-29]. 

The isoprene monomer is not readily available from direct cracking processes. Several routes are employed for its synthesis. One route begins with the extraction of isoamylene fractions from catalytically cracked gasoline streams. Isoprene is produced by subsequent catalytic dehydrogenation. 

Reaction of the iron complex salt 602 with the arylamine 921 in the presence of air led directly to the tricarbonyl(ri -4b,8a-dihydro-9H-carbazole)iron complex (923) by a one-pot C-C and C-N bond formation. Demetalation of complex 923 and subsequent aromatization by catalytic dehydrogenation afforded 3,4-dimethoxy-l-heptyl-2-methylcarbazole (924), a protected carbazoquinocin C. Finally, ether cleavage of 924 with boron tribromide followed by oxidation in air provided carbazoquinocin C (274) (640) (Scheme 5.120). 

Traditionally, ethanol has been made from ethylene by sulfation followed by hydrolysis of the ethyl sulfate so produced. This type of process has the disadvantages of severe corrosion problems, the requirement for sulfuric acid reconcentration, and loss of yield caused by ethyl ether formation. Recently a successful direct catalytic hydration of ethylene has been accomplished on a commercial scale. This process, developed by Veba-Chemie in Germany, uses a fixed bed catalytic reaction system. Although direct hydration plants have been operated by Shell Chemical and Texas Eastman, Veba claims technical and economic superiority because of new catalyst developments. Because of its economic superiority, it is now replacing the sulfuric acid based process and has been licensed to British Petroleum in the United Kingdom, Publicker Industries in the United States, and others. By including ethanol dehydrogenation facilities, Veba claims that acetaldehyde can be produced indirectly from ethylene by this combined process at costs competitive with the catalytic oxidation of ethylene. 

Acetic Acid. Acetic acid production in the United States has increased by large numbers in the last half century, since the monomer has many uses such as to make polymers for chewing gum, to use as a comonomer in industrial and trade coatings and paint, and so on. In the 1930s, a three-step synthesis process from ethylene through acid hydrolysis to ethanol followed by catalytic dehydrogenation of acetaldehyde and then a direct liquid-phase oxidation to acetic acid and acetic anhydride as co-products was used to produce acetic acid... 

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... 

The value of 2-butanol t ii° = 0 08, >,bpuol3 99.5 C) resides in the fact that 90 per cent of its total production is used for the synthesis of MEK. (methylethyiketone) by dehydrogenation. It is manufactured by the indirect hydration of n-butenes. of which the 1- and 2-isomers yield the same 2-butanoL They are absorbed in 80 per cent weight sulfuric acid, between 15 and 20 C, and 0.7.10 Pa absolute. The salfuric esters obtained are then hydrolysed between 25 and 35°C at 0.1.10 Pa absolute, with 65 to 75 per cent weight sulfuric add (Exxon. Maruzen and Shell processes). Despite considerable research work (Deutsche Texaco. Mitsubishi. Mitsui, Petrotex and Shell), the direct catalytic hydration of H-butenes has not yet reached the industrial stage. 

Alkylamines, such as butylamines, can be obtained by direct catalytic amination if the amination reaction is carried out in the presence of a fairly large excess of hydrogen. With specific nickel-, copper-, and cobalt-based catalysts which promote hydrogenation and dehydrogenation reactions, yields and conversions per pass of better than 95 per cent are obtained. See Sec. V for more detailed information on this procedure. 

Scheme 7.30 shows the synthetic pathways to PHOST, including radical, cationic, and anionic polymerization techniques. The polymerization behavior of the hydroxystyrene monomer (also called vinyl phenol) has been extensively investigated by Sovish, " Overberger, " and Kato. " PHOST can by synthesized via direct radical polymerization of 4-hydroxystyrene, which in turn is obtained from catalytic dehydrogenation of 4-ethylphenol. This was the method used in the preparation of the first commercially available PHOST, which was sold by... 

The catalytic dehydrogenation of lower alkanes was first developed more than fifty years ago using chromia/alumina systems [1]. Although there has been development of new processes [2 - 6], the catalyst technology has tended to remain with either modified chromia/alumina or modified platinum/alumina catalysts. Therefore it seemed appropriate to re-examine the possibility of using oxide systems other than chromia to effect the alkane to alkene transition. Supported vanadium pentoxide has been extensively studied for the oxidative dehydrogenation of propane to propene [7-10] but rarely for the direct dehydrogenation reaction [6]. 

An interesting selectivity was uncovered in the direct cross-dehydrogenative coupUng between N-protected indoles and arenes (Scheme 11.40) [151]. Thus, whereas 2-arylated indoles 67a were preferentially obtained from N-acetyhndole in the presence of Cu(OAc)2, the reaction of N-pivalolyUndole with AgOAc led to 67b, with excellent selectivities. The reason for this C-2/C-3 selectivity is most likely due to the formation of higher-order palladium clusters or paUadium/copper clusters under the different reaction conditions. A related reaction between aryl-boronic acids and arenes or heteroarenes also proceeds under oxidative conditions with Pd(OAc)2 as catalyst [76]. A catalytic cycle initiated by an electrophihc attack of Pd(II) on the arene, followed by transmetallation with the aryl boronic acid and reductive elimination, was suggested. In this transformation, Cu(OAc)2 as stoichiometric oxidant could be replaced by O2, and for indoles, arylation at C-2 was observed. 

Alternatively, aliphatic alcohols may be converted directly to the respective dimethyl alkylamines by catalytic amination in the presence of dimethylamine and low-pressure hydrogen over copper catalyst. The mechanism is believed to involve catalytic dehydrogenation of the alcohol to an aldehyde, addition of DMA with concomitant water elimination to form the enamine, and then subsequent reduction to the alkyldimethylamine. This route is particularly favored with longer-chain alcohols, which are derived through hydrogenation of tallow, or palm fatty acids, or methyl esters... 

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