Hydration of acetylene to acetaldehyde

For a long time, only a liquid phase process was employed industrially for the hydration of acetylene to acetaldehyde mercury salts in acidic solution were used as catalysts. Only recent reports can be found in the literature (e.g. ref. 300) on the industrial utilisation of the direct vapour phase hydration of acetylene over solid catalysts. 

It has been reported that solid acids and oxides or salts of different metals can catalyse the vapour phase hydration of acetylene. Most typical are phosphoric acid and phosphates of bivalent metals, such as Zn or Cd. Organic ion exchangers and synthetic zeolites exchanged for Zn2+, Cd2+, Hg2+ and Cu2+ ions were also employed. A survey of inorganic catalysts [254] or of organic ion exchangers [283] catalysing the hydration of acetylene or its derivatives can be found in literature. 

The temperatures reported in the kinetic studies range from 260 to 350°C. In most of the investigations, the hydration rates were found to be of the first order with respect to acetylene [300,302—304]. With zinc phosphate [303], cadmium—calcium phosphate [300] and cation-exchanged zeolites [304], the rates were independent of the concentration of water. Thus the simple kinetic equation 

the partial pressure of water is not really involved in the rate expression for the reaction catalysed by supported phosphoric acid, as for the other mentioned catalysts [300,303,304] [eqn. (18)]. 

It was proposed [302] to explain this form of reaction kinetics on the basis of a homogeneous mechanism. The authors assume that the reaction proceeds in the film of phosphoric acid containing dissolved acetylene and they adopt the reaction scheme of Taft [291,292] for the hydration of 

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FIGURE 3.30 (a) Hydration of acetylene to acetaldehyde and (b) transformation of an isonitrile to... 

Clinoptilolite Isomerization of n-butene, the dehydration of methanol to dimethyl ether, and the hydration of acetylene to acetaldehyde... 

Again, these appear to resemble the corresponding Mo-dependent enzymes. The unique acetylene hydratase from the acetylene-utilizing Pelobacter acetylenicus catalyzes the hydration of acetylene to acetaldehyde.687... 

Concerning alkynes, only the hydration of acetylene to acetaldehyde has been studied on X zeolites in Cu, Ag, Zn, Cd forms (ref. 11). These zeolites are active but they suffer fast deactivation. 

The one non-redox reaction catalyzed by a tungsten enzyme involves the hydration of acetylene to acetaldehyde [5], This same reaction is catalyzed by WO(mnt)22- but not by W02(mnt)22- [186], The five-coordinate W(IV) complex should have an open site that may be available to coordinate and activate the acetylene substrate [194],... 

Other examples of the use of natural zeolites in catalysis has been the use of Cd-exchanged chabazite, clinoptilolite, erionite, and mordenite as catalysts in the hydration of acetylene to acetaldehyde [26], and a Cu-exchanged natural mordenite, which was studied as a catalyst for the selective reduction of NO with NH3 [27],... 

Catalytic conversions were experimentally studied in Russia toward the end of the nineteenth century, and especially in the twentieth century, and regularities were empirically established in a number of cases. The work of A. M. Butlerov (1878) on polymerization of olefins with sulfuric acid and boron trifluoride, hydration of acetylene to acetaldehyde over mercury salts by M. G. Kucherov (1881) and a number of catalytic reactions described by V. N. Ipatieff beginning with the turn of the century (139b) are widely known examples. S. V. Lebedev studied hydrogenation of olefins and polymerization of diolefins during the period 1908-13. Soon after World War I he developed a process for the conversion of ethanol to butadiene which is commercially used in Russia. This process has been cited as the first example of commercial application of a double catalyst. Lebedev also developed a method for the polymerization of butadiene to synthetic rubber over sodium as a catalyst. Other Russian chemists (I. A. Kondakov I. Ostromyslenskif) were previously or simultaneously active in rubber synthesis. Lebedev s students are now continuing research on catalytic formation of dienes. 

Hydration of acetylene to acetaldehyde, catalyzed by sulfuric acid and mercuric sulfate... 

The nse of polysnlfide complexes in catalysis has been discnssed. Two major classes of reactions are apparent (1) hydrogen activation and (2) electron transfers. For example, [CpMo(S)(SH)]2 catalyzes the conversion of nitrobenzene to aniline at room temperature, while (CpMo(S))2S2CH2 catalyzes a number of reactions snch as the conversion of bromoethylbenzene to ethylbenzene and the rednction of acetyl chloride, as well as the rednction of alkynes to the corresponding cw-alkenes. Electron transfer reactions see Electron Transfer in Coordination Compounds) have been studied because of their relevance to biological processes (in, for example, ferrodoxins), and these cluster compounds are dealt with in Iron-Sulfur Proteins. Other studies include the use of metal polysulfide complexes as catalysts for the photolytic reduction of water by THF and copper compounds for the hydration of acetylene to acetaldehyde. ... 

To be historically correct, there were earlier examples of metal-mediated homogeneous catalysis. For example, the Hg -catalyzed hydration of acetylene to acetaldehyde became an industrial process in 1912. There is an intermediate /r-acetylene complex to activate the substrate. The lead chamber process to make sulfuric acid (NO catalysis) is even older but does not involve metals or metal complexes as catalysts [134]. 

As examples, xylene isomerization, toluene hydrodemethylation, n-butene isomerization, dehydration of methanol to demethyl ether, hydration of acetylene to acetaldehyde [31], catalytic reduction of NO [86] have been described to be successful if applying different varieties of treated clinoptilolite (cation exchanged or activated ). For a rough estimate about the importance of clinoptilolite for catalytic applications a search in the Chemical Abstracts... 

Yearly production of acetic acid in the United States is approximately 10 kg, a volume that ranks it at the top of the list of organic chemicals manufactured by the US chemical industry. The first industrial synthesis of acetic acid was commercialized in 1916 in Canada and Germany, using acetylene as a feedstock. The process involved two stages (1) hydration of acetylene to acetaldehyde followed by (2) oxidation of acetaldehyde to acetic acid by molecular oxygen, catalyzed by cobalt (III) acetate. 

Various compounds have been obtained by the reaction between acetylenes and solutions of mercuric salts. Thus crystalline derivatives RC=C—Hg—C=CR are obtained from mercuric oxide and RC=CH. Crystalline substances RHgC=CHgR result when RHgX reacts with acetylene itself in alcoholic potassium hydroxide. An important property of these compounds is their ready hydrolysis to aldehydes. It is probable that hydration of acetylene to acetaldehyde (industrially important some years ago) proceeds though such intermediates. 

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