Union Carbide Adds

A. E. Broderick (Union Carbide). HEC did not become a viable commercial product until the early 1960s. In addition to the general production problems and market development costs, new products face a variety of environmental controls in the 1990s that add more constraints to market development. None the less two more recentiy developed water-soluble polymers have achieved limited market acceptance and are described below. 

Union Carbide developed cyclo-aliphatic epoxies via peracetic add synthesis. 

Generation of a bernyne intermediate. A general principle of synthesis devised by Bunnett involves creation of an intermediate benzyne having a nucleophilic center so located that it can add intramolecularly to the triple bond. An example is the synthesis of 3-acetyloxindole from o-chloroacetoacetanilide (Union Carbide Chem. Co.) with potassium amide in liquid ammonia. In another synthesis o- and m-halo isomers gave the same product. 

Most of the methyl ethyl ketone (d ° 0.805t3 mp —819 0, bpt013 = 79.6°Q manufactured worldwide is produced by the dehydrogenation of secondary butanol Smaller quantities me obtained as a by-product of the oxidation of a-butane to acetic add. This is the case in the United States of Celanese in its Pampa, Texas, plant (40,000 t/year) and of Union Carbide in Brownsville, Texas (35,000 t/year). Plants of this type built in Western Europe have been shut down, including the Kooas plant in the Netherlands (20.000 year at Europoort) which was closed in 1979. 

The catalyst systems employed are based on molybdenum and phosphorus. They also contain Various additives (oxides of bismuth, antimony, thorium, chromium, copper, zirconium, etc.) and occur in the form of complex phosphomolybdates, or preferably heteropolyacids deposited on an inert support (silicon carbide, a-alumina, diatomaceous earths, titanium dioxide, etc.). This makes them quite different from the catalysts used to produce acrylic acid, which do not offer sufficient activity in this case. With residence times of 2 to 5 s, once-through conversion is better than 90 to 95 per cent, and the molar yield of methacrylic acid is up to 85 to 90 per cent The main by-products formed are acetic add, acetone, acrylic add, CO, C02, etc. The major developments in this area were conducted by Asahi Glass, Daicel, Japan Catalytic Chemical, Japanese Gem, Mitsubishi Rayon, Nippon Kayaku, Standard Oil, Sumitomo Chemical, Toyo Soda, Ube, etc. A number of liquid phase processes, operating at about 30°C, in die presence of a catalyst based on silver or cobalt in alkaline medium, have been developed by ARCO (Atlantic Richfield Co,), Asahi, Sumitomo, Union Carbide, etc. 

The Union Carbide process starting with cydohexane, which is first converted to cyclohexanone, which is in tnm oxidized to caprolactooe. This compound is then converted to caprolactam by the action of ammonia, at 4O0°C, under 17.106 Pa absolute pressure. Cyclohexanone is oxidized around 50 C, at normal pressure, by means of peracetic add, in the presence of acetaldehyde, which is oxidized to acetic add. The plant built by Union Carbide was shut down shortly after its construction. Variants have been proposed by Degussa, Toa Gosei and Ugine Kuhlmann without industrial success. 

M D2EHPA — Add 32.3 g of di(2-ethylhexyl)phosphoric acid (Union Carbide Chemical Company) to chloroform-AR in a 1-liter volumetric flask and make to volume with chloroform. 

The work was strongly inspired by Union Carbide s Ethoxene process, a route for manufacturing ethylene from ethane and oxygen by oxidative dehydrogenation. The first catalysts consisted of molybdenum, vanadium, and niobium oxides. The selectivity for ethylene was very high but, unfortunately, the conversion of ethane was low ( 10%). Therefore, scientists at the time focused on the co-production of ethylene and acetic acid. A catalyst consisting of molybdenum, vanadium, niobium, calcium, and antimony supported on a molecular sieve was developed (63% selectivity to acetic acid, 14% selectivity to ethylene, and 3% conversion of ethane). In addition, Rhone-Poulenc (catalyst vanadium oxide or vanadyl pyrophosphate) and BP (catalyst combination of rhenium and tungsten) patented processes for the production of acetic acid from ethane. Very efficient catalysts were also disclosed by Hoechst (molybdenum vanadate, promoted with Nb, Sb, Ca, and Pd, 250-280 °C, 15 bar, 86% selectivity to acetic add at 11% conversion of ethane per pass) and Sabic (phosphorus-modified molybdenum-niobium vanadate, 260 °C, 14 bar, 50% selectivity to acetic acid at 53% conversion of ethane). 

Several companies have marketed polyarylates under the trade names U-polymer (Unitika of Japan), Arylef (Sohray of Belgium), Ardel (Union Carbide), and Arylon (Du Pont). These are noncrystallizing copolymers of mixed phthaHc adds with a bisphenol and have repeat units of the type shown above. They are melt processable with Tg and heat distortion temperatures in the range of 150—200°C and have similar mechanical properties to polycarbonate and polyethersulfones (see later). 

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