Acetone-acetylene process

Acetone—Acetylene. A process based on acetone and acetylene South Africa have used this process to produce isoprene ... 

Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

Until World War 1 acetone was manufactured commercially by the dry distillation of calcium acetate from lime and pyroligneous acid (wood distillate) (9). During the war processes for acetic acid from acetylene and by fermentation supplanted the pyroligneous acid (10). In turn these methods were displaced by the process developed for the bacterial fermentation of carbohydrates (cornstarch and molasses) to acetone and alcohols (11). At one time Pubhcker Industries, Commercial Solvents, and National Distillers had combined biofermentation capacity of 22,700 metric tons of acetone per year. Biofermentation became noncompetitive around 1960 because of the economics of scale of the isopropyl alcohol dehydrogenation and cumene hydroperoxide processes. 

Chemical Uses. In Europe, products such as ethylene, acetaldehyde, acetic acid, acetone, butadiene, and isoprene have been manufactured from acetylene at one time. Wartime shortages or raw material restrictions were the basis for the choice of process. Coking coal was readily available in Europe and acetylene was easily accessible via calcium carbide. 

Most by-product acetylene from ethylene production is hydrogenated to ethylene in the course of separation and purification of ethylene. In this process, however, acetylene can be recovered economically by solvent absorption instead of hydrogenation. Commercial recovery processes based on acetone, dimetbylform amide, or /V-metby1pyrro1idinone have a long history of successfiil operation. The difficulty in using this relatively low cost acetylene is that each 450, 000 t/yr world-scale ethylene plant only produces from 7000 9000 t/yr of acetylene. This is a small volume for an economically scaled derivatives unit. 

Many engineering thermoplastics (e.g., polysulfone, polycarbonate, etc.) have limited utility in applications that require exposure to chemical environments. Environmental stress cracking [13] occurs when a stressed polymer is exposed to solvents. Poly(aryl ether phenylquin-oxalines) [27] and poly(aryl ether benzoxazoles) [60] show poor resistance to environmental stress cracking in the presence of acetone, chloroform, etc. This is expected because these structures are amorphous, and there is no crystallinity or liquid crystalline type structure to give solvent resistance. Thus, these materials may have limited utility in processes or applications that require multiple solvent coatings or exposures, whereas acetylene terminated polyaryl ethers [13] exhibit excellent processability, high adhesive properties, and good resistance to hydraulic fluid. 

A three-step process developed hy Snamprogetti is based on the reaction of acetylene and acetone in liquid ammonia in the presence of an alkali metal hydroxide. The product, methylhutynol, is then hydrogenated to methylhutenol followed hy dehydration at 250-300°C over an acidic heterogeneous catalyst. 

In the free state acetylene can decompose violently, e.g. above 9psig (0.62 bar) undissolved (free) acetylene will begin to dissociate and revert to its constituent elements. This is an exothermic process which can result in explosions of great violence. For this reason acetylene is transported in acetone contained in a porous material inside the... 

Butanol, which at one time was an unwanted by-product in the preparation of acetone, is now the most important product of the fermentation. The building of a large new factory in Puerto Rico using 10,000 tons of molasses per annum for its production is an indication of this importance. Butanol is probably still the best solvent for cellulose nitrate lacquers. Dibutyl phthalate is certainly the most widely used plasticizer for synthetic resins, and butyl oleate, tributyl citrate and dibutyl tartrate have also been described as plasticizers. Another important use of butanol is as a source of butadiene, which serves as an intermediate in the conversion of sucrose into a synthetic rubber. Although in recent years other methods have been described for the preparation of butanol (for example, from ethyl alcohol and from acetylene), yet the fermentation of carbohydrates is still the cheapest process. 

Twenty-five years ago the only oxygenated aliphatics produced in important quantities were ethyl and n-butyl alcohols and acetone made by the fermentation of molasses and grain, glycerol made from fats and oils, and methanol and acetic acid made by the pyrolysis of wood. In 1927 the production of acetic acid (from acetylene) and methanol (from synthesis gas) was begun, both made fundamentally from coal. All these oxygenated products are still made from the old raw materials by the same or similar processes, but the amount so made has changed very little in the past quarter century. Nearly all the tremendous growth in the production of this class of compounds has come from petroleum hydrocarbons. 

In the mid-l O s, it was found that acetic acid itself could be catalytically dehydrated to ketene, which when absorbed in fresh acid gave the anhydride. Soon after this process became commercially established, the older processes of making the anhydride were discontinued. By this time synthetic acetic acid was being made from acetylene via acetaldehyde oxidation, from synthetic ethyl alcohol also via acetaldehyde, and by the direct oxidation of fermentation ethyl alcohol. The ketene route to acetic anhydride, in addition to starting from acetic acid, later employed acetone as raw material. 

The idea of synthesizing imide oligomers which carry acetylenic terminations appeared attractive because homopolymerization through acetylenic endgroups occurs without any volatile evolution and provides materials with good properties. Landis et. al (8,9) published the synthesis of such acetylene terminated imide oligomers from benzophenone tetracarboxylic anhydride, aromatic diamine and 3-ethynylaniline via the classical route. As usual, the amide acid is formed as an intermediate which, after chemical cyclodehydration, provides the polymide. Since ethynyl-terminated polyimide is used as a matrix resin for fiber composites, processing is possible via the amide acid, which is soluble in acetone, or via the fully imidized prepolymer, which is soluble in NMP. The chemical structure of the fully imidized ethynyl-terminated polyimide is provided in Fig. 44. 

Borazine is prepared by the procedure described above. Impurities in commercially obtained acetylene can result in the precipitation of the catalyst, and in such cases, no reaction is observed. Acetylene is therefore purified by a process similar to that described in the literature17 in which acetone and other impurities are removed by a purification train consisting of two bubblers of concentrated sulfuric acid followed by two U-traps containing NaOH pellets and white Drierite, respectively, to remove moisture. The inlet of the train is connected to a cylinder of acetylene, and its outlet to the vacuum line. 

The primary source of isoprene today is as a by-product in the production of ethylene via naphtha cracking. A solvent extraction process is employed. Much less isoprene is produced in the crackers than butadiene, so the availability of isoprene is much more limited. Isoprene also may be produced by the catalytic dehydrogenation of amylenes, which are available in C-5 refinery streams. It also can be produced from propylene by a dimerization process, followed by isomerization and steam cracking. A third route involves the use of acetone and acetylene, produced from coal via calcium carbide. The resulting 3-methyl-butyne-3-ol is hydrogenated to methyl butanol and subsequently dehydrogenated to give isoprene. The plants that were built on these last two processes have been shut down, evidently because of the relatively low cost of the extraction route. 

The polymer of methyl methacrylate (MMA) is known as Perspex. It is a clear transparent glasslike material with high hardness, resistance to fracture, and chemical stability. The conventional route, as shown by reaction 4.10, involves the reaction between acetone and hydrocyanic acid, followed by sequential hydrolysis, dehydration, and esterification. This process generates large quantities of solid wastes. An alternative route based on a homogeneous palladium catalyst has recently been developed by Shell. In this process a palladium complex catalyzes the reaction between propyne (methyl acetylene), methanol, and carbon monoxide. This is shown by reaction 4.11. The desired product is formed with a regioselectivity that could be as high as 99.95%. 

The raw materials used by this process are acetylene and acetone, which present the drawback of being already elaborated products and therefore expensive. However, the chemical operations involved and the equipment required are rather simple, and yields are also high. The main steps in the conversion are the following ... 

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