Acrylonitrile synthesis from acetylene

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

Much recent work has been done on the synthesis of pyridines from alkynes and nitriles over cobalt catalysts. For example, 2-vtnylpyndine has heen obtained in good yield from acetylene and acrylonitrile using a cyclopentadienyl-cobalt catalyst. Pyridine has also been obtained from cyclopentadiene and ammonia over a sihca/alumina catalyst. 

Nickel catalysts for the syntheses of cyclic compounds were first successfully utilized by Reppe, who was able to prepare cyclooctatetraene from acetylene (65). This eight-membered ring synthesis, and also the preparation of cyclic products from strained olefins (e.g., bicycloheptene and norbornadiene) and acrylonitrile, have been adequately reviewed elsewhere (7) and will therefore not be considered further. A short account of the cyclization reactions of butadiene using nickel-containing catalysts has appeared previously in this series (/). The discovery of new synthetic possibilities and a deeper understanding of the mechanism of these reactions justify a more extensive treatment. 

This reaction was once regarded as an important industrial process, since it afforded a straightforward synthesis of acrylonitrile from acetylene ... 

Copper chloride complexes can be used as catalysts in a number of organic reactions. Examples include the Wacker process, which is the oxidization of ethylene to acetaldehyde by oxygen and aqueous Cu and Pd precatalysts (or, alternatively using iron catalysts) plus the synthesis of acrylonitrile from acetylene and hydrogen cyanide using CuCl. Cuprous chloride has also been used as a desulfiuizmg and... 

The most interesting application from an industrial point of view is the cobalt-catalyzed one-step synthesis of 2-vinylpyridine from acetylene and acrylonitrile (eq. (10)). In this way the fine chemical can be manufactured using equal amounts by weight of the comparatively inexpensive components, acetylene and acrylonitrile. The 2-vinylpyridine synthesis must be carried out in pure acrylonitrile below 130-140 °C, otherwise acrylonitrile and the product 2-vinylpyridine undergo thermal polymerization [34]. Therefore only very active catalysts can be applied in the reaction of eq. (10). The best results were obtained using i/ -l-phenyl-borininatocobalt cod as the catalyst (productivity 2.78 kg 2-vinylpyridine per g cobalt [5 ej. 

Desulfurization of petroleum feedstock (FBR), catalytic cracking (MBR or FI BR), hydrodewaxing (FBR), steam reforming of methane or naphtha (FBR), water-gas shift (CO conversion) reaction (FBR-A), ammonia synthesis (FBR-A), methanol from synthesis gas (FBR), oxidation of sulfur dioxide (FBR-A), isomerization of xylenes (FBR-A), catalytic reforming of naphtha (FBR-A), reduction of nitrobenzene to aniline (FBR), butadiene from n-butanes (FBR-A), ethylbenzene by alkylation of benzene (FBR), dehydrogenation of ethylbenzene to styrene (FBR), methyl ethyl ketone from sec-butyl alcohol (by dehydrogenation) (FBR), formaldehyde from methanol (FBR), disproportionation of toluene (FBR-A), dehydration of ethanol (FBR-A), dimethylaniline from aniline and methanol (FBR), vinyl chloride from acetone (FBR), vinyl acetate from acetylene and acetic acid (FBR), phosgene from carbon monoxide (FBR), dichloroethane by oxichlorination of ethylene (FBR), oxidation of ethylene to ethylene oxide (FBR), oxidation of benzene to maleic anhydride (FBR), oxidation of toluene to benzaldehyde (FBR), phthalic anhydride from o-xylene (FBR), furane from butadiene (FBR), acrylonitrile by ammoxidation of propylene (FI BR)... 

In 1893, the French chemist Moreau described two routes for the synthesis of acrylonitrile that were based on the dehydration of either acrylamide or ethylene cyanohydrin [10]. There was very little interest in acrylonitrile until 1937 when synthetic rubber based on acrylonitrile-butadiene copolymers was first developed in Germany. A process based on the addition of hydrogen cyanide to acetylene was developed at that time and in the 1950s, the acrylic fiber industry provided the stimulus for further process developments. Today acrylonitrile is made commercially by one of three possible methods (a) from propylene, (b) from acetylene and hydrogen cyanide, and (c) from acetaldehyde and hydrogen cyanide. 

Donor substituents on the vinyl group further enhance reactivity towards electrophilic dienophiles. Equations 8.6 and 8.7 illustrate the use of such functionalized vinylpyrroles in indole synthesis[2,3]. In both of these examples, the use of acetyleneic dienophiles leads to fully aromatic products. Evidently this must occur as the result of oxidation by atmospheric oxygen. With vinylpyrrole 8.6A, adducts were also isolated from dienophiles such as methyl acrylate, dimethyl maleate, dimethyl fumarate, acrolein, acrylonitrile, maleic anhydride, W-methylmaleimide and naphthoquinone. These tetrahydroindole adducts could be aromatized with DDQ, although the overall yields were modest[3]. 

The addition [44] of hydrocyanic acid to acetylene (eq. (20)) in a solution of copper chloride in aqueous hydrochloric acid gives good yields and, prior to the time when the synthesis of acrylonitrile by ammonoxidation [45] from propene became technically feasible, was the major preparation process. This synthesis, too, has nowadays completely lost its importance. 

The growth of synthetic fibers has led to the devising of syntheses from petroleum of the chemical intermediates required for this new industry. Leaving aside acetic anhydride from ethylene via synthetic ethanol and from propylene via acetone, already established and used for cellulose acetate in the 193O s, nylon has called for the isolation of petroleum cyclohexane and for the discovery of a route from butadiene to nylon salt Dacron for the isolation of p-xylene from petroleum xylene, and the nitrile fibers for the synthesis of acrylonitrile from ethylene or acetylene. 

Natural gas has become an important starting material for the manufacture of hydrogen, acetylene, and synthesis gas for producing methanol, Fischer-Tropsch hydrocarbons, ammonia, etc. The early processes for producing HCN from CH4, NH3, and air have been greatly improved, so that HCN can be added to the growing list of products derived from natural gas. An example of an important end product is Orion, the du Pont polyacrylonitrile synthetic fiber. The addition of HCN to acetylene yields the required acrylonitrile. 

Treatment of terminal acetylenes with hydrogen iodide, generated in situ from TMSCl, sodium iodide, and water, provides a highly regioselective synthesis of 2-iodo-l-alkenes. Followed by addition of cuprous cyanide, the protocol offers a convenient one-pot preparation of 2-substituted acrylonitriles in fair to good yield (eq 90). In contrast, when the reaction with arylacetylene proceeds in DMSO and with catalytic amount of sodium iodide, the 3-arylpropynenitrile is obtained as the preferred product. 

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