Acetone cyanohydrin process

The only method used in the U.S. for the production of methyl methacrylate is the acetone cyanohydrin process. Acetone cyanohydrin (from the reaction of acetone with hydrogen cyanide) is reacted with sulfuric... 

The price of butanes and butylenes fluctuates seasonally depending on the demand for gasoline in the United States. Since much chemical-product usage is determined by price—performance basis, a shift to development of butylene-based technology may occur. Among the butylenes, demand for isobutylene is likely to increase (and so its price) as more derivatives such as methyl methacrylate and methacrylic acid are produced from isobutylene instead of the conventional acetone cyanohydrin process. 

Acetone cyanohydrin process Surface-coating resins Molding and extrusion powders Oil additives Miscellaneous and export automotive paints... 

Polymethyl methacrylate (PMM). Polymethyl methacrylate is manufactured by the acetone cyanohydrin process, which is the only process used in the United States for the manufacturing of polymethyl methacrylate [5], The demand in 2007 for this polymer was 1,485 million lb. In 2002, the demand was 1,285 million lb [6], Price ranged from around 0.75 to 0.41 per pound from 1998 to 2003. 

The most common process used to produce methyl methacrylate ( 0.71/lb) is the acetone cyanohydrin process [36]. Acetone is reacted with hydrogen cyanide and methanol to produce methyl methacrylate ... 

In the petrochemical industry the introduction of unsaturations in hydrocarbons is mainly obtained by dehydrogenation. This kind of reaction is less suitable for the functionalization of fine chemicals, because the high temperature necessary for the endothermic reaction can lead to the decomposition of thermally unstable compounds. An alternative reaction consists in the oxidative dehydrogenation, that can be carried out at lower temperatiu es. An example of this kind of reaction is constituted by the synthesis of methacrylic add (MAA, intermediate of methylmethacrylate production) via the oxidative dehydrogenation of isobutyric add (IBA), itself obtained from isobutyraldehyde (by-product of the oxo synthesis of nbutyraldehyde from propylene). This process constitutes one of the economically most interesting routes, alternative to the acetone-cyanohydrin process, which nowadays is the predominant process for the MAA production. 

Vinyl compounds are widely used in the industry in manufacture of various resins and polymers and the like. Methacrylic acid and methyl methacrylate are especially attractive as row materials of polymethyl methacrylate that is an important polymer so-called "organic glass." Until a new process consisting of two-step oxidation of isobutylene was commercially practiced in 1982, methyl methacrylate had been produced by the "Acetone Cyanohydrine Process," which uses acetone, hydrogen cyanide, methanol, and sulfuric acid as raw materials. Technical and economical drawbacks of this process have spurred a considerable industrial research effort to develop an alternate route to methacrylic acid and methyl methacrylate. Therefore, many attempts have been focused on the production of these compounds by aldol-type condensation using HCHO. 

The current industrial production of methylmethacrylate by the acetone-cyanohydrin process suffers from a number of drawbacks, which make it environmentally unfriendly. In particular, it makes use of a very toxic reactant (HCN) and intermediate (acetone cyanohydrin), and coproduces large amounts of impure ammonium sulphate, contaminated with organic compounds. Among the several alternative synthetic routes which have been proposed, particularly interesting from both the practical and scientific points of view is the single-step oxidation of isobutane to methacrylic acid, intermediate in the synthesis of methylmethacrylate. Several industrial companies have studied this reaction (and the selective oxidation of propane to acrylic acid, as well), and it has been established that the most active and selective catalysts are those which are based on Keggin-type polyoxometalates (POM s), containing phosphorus and molybdenum as the main components [1-18]. 

Most methyl methacrylate (MMA) is made by the acetone cyanohydrin process. Developed in the 1930s for the production of MMA from acetone, hydrogen cyanide, sulfuric acid, and methanol, it has been improved over the years, but problems inherent in the basic process persist. For example, production of large quantities of ammonium bisulfate by-product and sulfuric acid sludge, as well as difficulty in obtaining low cost sources of... 

The major process currently operated on the commercial scale is known as the acetone cyanohydrin (23) (ACN) process [14]. This process uses readily available cheap raw materials (Scheme 2.3). Acetone is produced from propylene and hydrogen cyanide or can be obtained as a byproduct from acrylonitrile production. Acrylonitrile is manufactured via propylene ammoxidation or by catalytic ammoxidation of natural gas. Sulphuric acid is readily available but constitutes the major environmental problem of the acetone cyanohydrin process since a large excess is required to effect the hydrolysis of acetone cyanohydrin to form the methacrylamide sulphate intermediate. 

GLC results confirmed the presence of very slightly depressed levels of NPA after distillation in experiments 1-3 (Table 2). Analysis of experiment 4 by GLC was complicated, however, due to the hexanes introduced with TEA, which is used as a 25% solution in hexanes. The column used in the GLC analysis was the non-polar DC-200 (15%) on a Chromosorb P solid support. The more polar n-propyl alcohol elutes just prior to the elution of the non-polar (but lower boiling) hexane peak. The "hexane peak" is actually two peaks, probably corresponding to two structural isomers. The only problem with peak overlap occurs with the hexane peaks and an impurity intrinsic to Rohm and Haas MMA, possibly a reaction by product from the acetone-cyanohydrin process (ACH). Chromatogram (A) of Figure 3 shows the 1% NPA doped MMA prior to reaction with tri n-octyl aluminum (TOA). The peaks of interest are the air... 

The partial oxidation of isobutene into methacrolein and methacrylic acid would be the best option among all approaches to replace the technology employed in the acetone-cyanohydrin process. ... 

Compounds with active hydrogen add to the carbonyl group of acetone, often followed by the condensation of another molecule of the addend or loss of water. Hydrogen sulfide forms hexamethyl-l,3,5-trithiane probably through the transitory intermediate thioacetone which readily trimerizes. Hydrogen cyanide forms acetone cyanohydrin [75-86-5] (CH2)2C(OH)CN, which is further processed to methacrylates. Ammonia and hydrogen cyanide give (CH2)2C(NH2)CN [19355-69-2] ix.orn. 6<55i the widely used polymerization initiator, azobisisobutyronitrile [78-67-1] is made (4). 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Until 1982, almost all methyl methacrylate produced woddwide was derived from the acetone cyanohydrin (C-3) process. In 1982, Nippon Shokubai Kagaku Kogyo Company introduced an isobutylene-based (C-4) process, which was quickly followed by Mitsubishi Rayon Company in 1983 (66). Japan Methacryhc Monomer Company, a joint venture of Nippon Shokubai and Sumitomo Chemical Company, introduced a C-4-based plant in 1984 (67). Isobutylene processes are less economically attractive in the United States where isobutylene finds use in the synthesis of methyl /i / butyl ether, a pollution-reducing gasoline additive. BASF began operation of an ethylene-based (C-2) plant in Ludwigshafen, Germany, in 1990, but favorable economics appear to be limited to conditions unique to that site. 

Mitsubishi Gas Chemical Company Process. The commercial MMA manufacturing process based on sulfuric acid and acetone cyanohydrin suffers from the large quantities of ammonium sulfate produced. Because ammonium sulfate has only low value as fertili2er, regeneration of sulfuric acid from ammonium sulfate [7783-20-2] is required. Despite the drawbacks of using sulfuric acid, this technology is stiU the most widely practiced... 

The handling of toxic materials and disposal of ammonium bisulfate have led to the development of alternative methods to produce this acid and the methyl ester. There are two technologies for production from isobutylene now available ammoxidation to methyl methacrylate (the Sohio process), which is then solvolyzed, similar to acetone cyanohydrin, to methyl methacrylate and direct oxidation of isobutylene in two stages via methacrolein [78-85-3] to methacryhc acid, which is then esterified (125). Since direct oxidation avoids the need for HCN and NH, and thus toxic wastes, all new plants have elected to use this technology. Two plants, Oxirane and Rohm and Haas (126), came on-stream in the early 1980s. The Oxirane plant uses the coproduct tert-huty alcohol direcdy rather than dehydrating it first to isobutylene (see Methacrylic acid). 

Cyanohydrins are used primarily as intermediates in the production of other chemicals. Manufacture of methyl methacrylate, used to make acrylic mol ding resins and clear sheet, eg, Plexiglas acrylic sheet, from acetone cyanohydrin is the most economically important cyanohydrin process (see Methacrylic polymers). Cyanohydrins are also used as solvents in appHcations including fiber-spinning and metals refining. Cyanohydrins and derivatives reportedly act as antiknock agents in fuel oil and motor fuels and serve as electrolytes in electrolytic capacitors. 

The basic process for manufacture of acetone cyanohydrin was developed in the 1930s by Imperial Chemical Industries and has been improved over the years by the producing companies. 

One of the most important appHcations of this process is that of methyl methacrylate manufacture. In this process (81), acetone cyanohydrin is treated with sulfuric acid at 100°C, affording the corresponding methacrylamide sulfate which is esterified with methanol. After purification, methyl methacrylate (99.8% purity) is obtained in a yield of ca 85%. 

A plant produced methyl methacrylate by reacting hydrogen cyanide with acetone to produce acetone cyanohydrin followed by further processing to produce methyl methacrylate. The hydrogen cyanide was produced at another site and was transported to the methyl methacrylate plant by railcar. A hydrogen cyanide plant was subsequently installed at the methyl methacrylate plant site to eliminate the need for shipping hydrogen cyanide or acetone cyanohydrin. 

This synthesis of N-nitromorpholine is representative of a rather general reaction for the preparation of both primary and secondary nitramines.3 It represents the simplest process for obtaining both types of compounds. The reaction is unique in that a nitration is carried out under neutral or alkaline conditions. Acetone cyanohydrin nitrate may also be used for the nitration of many active methylene compounds.8... 

Organic cyanide compounds, or nitriles, have been implicated in numerous human fatalities and signs of poisoning — especially acetonitrile, acrylonitrile, acetone cyanohydrin, malonitrile, and succinonitrile. Nitriles hydrolyze to carboxylic acid and ammonia in either basic or acidic solutions. Mice (Mus sp.) given lethal doses of various nitriles had elevated cyanide concentrations in liver and brain the major acute toxicity of nitriles is CN release by liver processes (Willhite and Smith 1981). In general, alkylnitriles release CN much less readily than aryl alkylnitriles, and this may account for their comparatively low toxicity (Davis 1981). 

Maruoka and co-workers recently reported an example of a Zr-catalyzed cyanide addition to an aldehyde [64]. As is also illustrated in Scheme 6.20, the reaction does not proceed at all if 4 A molecular sieves are omitted from the reaction mixture. It has been proposed that the catalytic addition proceeds through a Meerwein—Ponndorf—Verley-type process (cf. the transition structure drawn) and that the crucial role of molecular sieves is related to facilitating the exchange of the product cyanohydrin oxygen with that of a reagent acetone cyanohydrin. The example shown is the only catalytic example reported to date the other reported transformations require stoichiometric amounts of the chiral ligand and Zr alkoxide. 

The traditional acetone-cyanohydrin (ACH) process is the most widely used in Europe and North America, while other processes are more used in Asia. In the... 

The ACH process has recently been improved, as stated by Mitsubishi Gas. Acetone-cyanohydrin is first hydrolized to 2-hydroxyisobutylamide with an Mn02 catalyst the amide is then reacted with methylformiate to produce the methyl ester of 2-hydroxyisobutyric acid, with coproduction of formamide (this reaction is catalyzed by Na methoxide). The ester is finally dehydrated with an Na-Y zeolite to methylmethacrylate. Formamide is converted to cyanhydric acid, which is used to produce acetone-cyanohydrin by reaction with acetone. The process is very elegant, since it avoids the coproduction of ammonium bisulphate, and there is no net income of HCN. Problems may derive from the many synthetic steps involved, and from the high energy consumption. 

A method of employing an organic solvent as a reaction medium that incorporates the safe transfer of HCN would be of great advantage to cyanohydrin production. Thus the recent development of enzyme catalysed transhydrocyanation, which employs acetone cyanohydrin [80-84] as a HCN carrier, is of significant value. This method makes the handling process of HCN both easier and less dangerous. 

In a recent development, the kinetics of the transhydrocyanation process between benzaldehyde and acetone cyanohydrin were studied by H NMR methods... 

Acetone cyanohydrin is manufactured by the direct reaction of hydrogen cyanide with acetone catalyzed by base, generally in a continuous process. 

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