Acrylic acids, from acetylenes

The Ni-catalyzed production of acrylic acid from acetylene produces 320 millionkg year. The BASF process operates at... 

Figure 1. Manufacture of acrylic acid from acetylene, CO and H2O [22]. (a, c) saturator, (b) reactor, (d, e) columns, (f) distillation.

By industrially manipulating acetylene or olefins under pressure in this way, chemical engineering helped to bring about very important productions, for instance that of acrylic acid from acetylene with a capacity of 130,000 tons/year and of butanol from propylene with 30,000 tons/year. For each of these reactions very specific and laborious developments were additionally required. The decomposition of iron carbonyl by nascent COg forming FeCOg had to be prevented by an increase of CO partial pressure. 

The carbonylation of alkynes in the presence of methanol or water and carbon monoxide produces a,(3-unsaturated carboxylic acids or esters (Scheme 50).l This reaction is rarely used in large-molecule synthetic applications however, it has been very important in the industrial preparation of acrylic acid from acetylene. 

The reaction is carried out in aqueous tetrahydrofuran, if acrylic acid is the desired product, or in aqueous alcohol if the ester is required. Nickel is introduced as bromide or iodide and is converted into carbonyl complexes under the reaction conditions, typically 200°C/100atm. One catalytic cycle which has been postulated for this process is shown in Fig. 12.18. Selectivity in the formation of acrylic acid from acetylene is better than 90%. Even from propyne, where anti-Markovnikov addition of [Ni]—H competes with the desired pathway, selectiv-ities of over 80% to methyl methacrylate H2C=C(Me)C02Me are achieved. The major by-product is methyl crotonate, MeCH=CHC02Me. 

In fl-trimethylsilylcarboxylic acids the non-Kolbe electrolysis is favored as the carbocation is stabilized by the p-effect of the silyl group. Attack of methanol at the silyl group subsequently leads in a regioselective elimination to the double bond (Eq. 29) [307, 308]. This reaction has been used for the construction of 1,4-cyclohexa-dienes. At first Diels-Alder adducts are prepared from dienes and P-trimethylsilyl-acrylic acid as acetylene-equivalent, this is then followed by decarboxylation-desilyl-ation (Eq. 30) [308]. Some examples are summarized in Table 11, Nos. 12-13. 

Acetylenes can also be carboxylated in the presence of dicobalt octacarbonyl. A patent (105) described the formation of acrylic and succinic acids from acetylene. Cyclopentanone was also formed in the presence of solvents (acetone, dioxane). Substituted succinic acids were formed from the corresponding substituted acetylenes. 

The synthesis of acrylic esters from acetylene, CO, and alcohols probably involves a similar three-step mechanism with CH2=CH—M as the initial addition product. Nickel carbonyl in aqueous acid is the preferred catalyst (176). 

Acetic acid (qv) can be produced synthetically (methanol carbonylation, acetaldehyde oxidation, butane/naphtha oxidation) or from natural sources (5). Oxygen is added to propylene to make acrolein, which is further oxidized to acryHc acid (see Acrylic acid and derivatives). An alternative method adds carbon monoxide and/or water to acetylene (6). Benzoic acid (qv) is made by oxidizing toluene in the presence of a cobalt catalyst (7). 

Thus asymmetric diaryl cyclopropenones were converted to the isomeric acrylic acids 318/319 by aqueous Ni(C0)4 in a similar proportion to that obtained from the corresponding acetylenes by carbonylation with the same catalyst279, whilst in non-aqueous media carbonyls like Ni(C0)4, Co2(CO)8, or Fe3(CO)12 effected de-carbonylation278, 280) probably via metal-complexed intermediates, e.g. 

Reppe A family of processes for making a range of aliphatic compounds from acetylene, developed by W. Reppe in IG Farbenindustrie, Germany, before and during World War II. In one of the processes, acetylene is reacted with carbon monoxide to yield acrylic acid CH=CH + CO + H20 CH2=CH-COOH Acrylic esters are formed if alcohols are used instead of water ... 

Acrylic acid [79-10-7] - [AIR POLLUTION] (Vol 1) - [ALDEHYDES] (Vol 1) - [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) - [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) - [POLYESTERS, UNSATURATED] (Vol 19) - [FLOCCULATING AGENTS] (Vol 11) - [CARBOXYLICACIDS - SURVEY] (Vol 5) -from acetylene [ACETYLENE-DERIVED CHEMICALS] (Vol 1) -from acrolein [ACROLEIN AND DERIVATIVES] (Vol 1) -acrylic esters from [ACRYLIC ESTER P OLYMERS - SURVEY] (Vol 1) -from carbon monoxide [CARBON MONOXIDE] (Vol 5) -C-21 dicarboxylic acids from piCARBOXYLIC ACIDS] (Vol 8) -decomposition product [MAT. ETC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -economic data [CARBOXYLIC ACIDS - ECONOMIC ASPECTS] (Vol 5) -ethylene copolymers [IONOMERS] (Vol 14) -in floor polishes [POLISHES] (Vol 19) -in manufacture of ion-exchange resins [ION EXCHANGE] (V ol 14) -in methacrylate copolymers [METHACRYLIC POLYMERS] (Vol 16) -in papermaking [PAPERMAKING ADDITIVES] (Vol 18)... 

These processes have supplanted the condensation reaction of ethanol, carbon monoxide, and acetylene as the principal method of generating ethyl acrylate [140-88-5] (333). Acidic catalysts, particularly sulfuric acid (334—338), are generally effective in increasing the rates of the esterification reactions. Care is taken to avoid excessive polymerization losses of both acrylic acid and the esters, which are accentuated by the presence of strong acid catalysts. A synthesis for acrylic esters from vinyl chloride (339) has also been examined. 

Other unsaturated substrates arylated by various diaryl iodonium salts included butenone, acrylic acid, methyl acrylate and acrylonitrile [46]. Allyl alcohols with diaryliodonium bromides and palladium catalysis were arylated with concomitant oxidation for example, from oc-methylallyl alcohol, aldehydes of the general formula ArCH2CH(Me)CHO were formed [47]. Copper acetylide [48] and phenyl-acetylene [49] were also arylated, with palladium catalysis. 

Coal was also the feedstock for synthesis gas vide infra). Many contributions to acetylene chemistry are due to Reppe. His work on new homogeneous metal (mainly nickel) catalysts for acetylene conversion, carried out in the period from 1928 to 1945, was not published until 1948. Under the influence of nickel iodide catalysts, acetylene, water and CO were found to give acrylic acid. A process based on this chemistry was commercialized in 1955. 

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... 

Acetylene-Based Routes. Walter Reppe, die father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acrylic acid or esters (75,76). This discovery7 led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60 —80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

A further development of the Reppe acrylic acid synthesis is the reaction, described in recent literature, of the noble metal-catalyzed carbonylation of higher acetylenes to give the corresponding acrylic acid derivatives. Thus, for example, the Pd-catalyzed carbonylation of propyne (eq. (10)) in the presence of methanol leads directly to methyl methacrylate [23]. Based on this work. Shell has developed a new production process for methyl methacrylate [24]. The propyne required can be isolated from the product streams from crackers, (cf. Section 2.3.2.3). 

Reppe process. Any of several processes involving reaction of acetylene (1) with formaldehyde to produce 2-butyne-l,4-diol which can be converted to butadiene (2) with formaldehyde under different conditions to produce propargyl alcohol and, from this, allyl alcohol (3) with hydrogen cyanide to yield acrylonitrile (4) with alcohols to give vinyl ethers (5) with amines or phenols to give vinyl derivatives (6) with carbon monoxide and alcohols to give esters of acrylic acid (7) by polymerization to produce cyclooctatetraene and (8) with phenols to make resins. The use of catalysts, pressures up to 30 atm, and special techniques to avoid or contain explosions are important factors in these processes. 

Three important processes have evolved from Reppe s work. Vinylation, the formation of vinyl derivatives by reaction of such compounds as acids, glycols, and alcohols with acetylene, produces the important vinyl esters and vinyl ethers. Ethinylation is defined as the reaction of acetylene with the carbon atom of a reactant without loss of the triple bond. A major application of the ethinylation reaction is to aldehydes and ketones to give alkynols and alkyndiols—e.g., the reaction of acetylene with formaldehyde to give propargyl alcohol and butyn-2-diol-l,4. Carboxylation (also referred to as carbonylation), the reaction of acetylene with carbon monoxide in the presence of metal carbonyls, has been applied to the production of acrylic acid, acrylates, and hydroquinone. 

The preparation, properties, and reactions, especially polymerization, of products from the acetylene-carbon monoxide reaction, such as acrylic acid and its esters, are given by Blout and Mark (8) and by Schildknecht (98). Similarly treated therein are the vinyl esters from acetylene and carboxylic acids, and other vinylation products such as vinyl ethers. The esterification of organic acids with olefins is reviewed by Morin and Bearse (76). 

Control of reactivity by catalysis provides the capability to shift to lower cost feedstocks. In the twentieth century, advances in catalysis have allowed the substitution of acetylene with olefins and subsequently with synthesis gas as primary feedstocks. For example, production of acrylic acid, traditionally produced by the Reppe process from acetylene and CO, has now been replaced by catalytic oxidation of propylene. The emergence of paraffins, the hydrocarbon feedstock of the future, will depend on development of catalysts for selective alkane C-H activation (2). 

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