Ammoxidation process, Sohio

Acrylonitrile is produced in commercial quantities almost exclusively by the vapor-phase catalytic propylene ammoxidation process developed by Sohio... 

SOHIO [Standard Ohio] The Standard Oil Company of Ohio (later BP Chemicals America) has developed many processes, but its ammoxidation process, for converting propylene to acrylonitrile, is the one mostly associated with its name. First operated in the United States in 1960, it is the predominant process for making acrylonitrile used in the world today. Jacobs, M., Ind. Eng. Chem., 1996, 74(41), 40. 

In 1959, Idol (2), and in 1962, Callahan et al. (2) reported that bismuth/molybdenum catalysts produced acrolein from propylene in higher yields than that obtained in the cuprous oxide system. The authors also found that the bismuth/molybdenum catalysts produced butadiene from butene and, probably more importantly, observed that a mixture of propylene, ammonia, and air yielded acrylonitrile. The bismuth/molybdenum catalysts now more commonly known as bismuth molybdate catalysts were brought to commercial realization by the Standard Oil of Ohio Company (SOHIO), and the vapor-phase oxidation and ammoxidation processes which they developed are now utilized worldwide. 

Bismuth Molybdate Catalysts. The Raman spectra of the bismuth molybdates, with Bi/Mo stoichiometric ratios between 0.67 and 14, have been examined using the FLS approach (see Section 3.2). " The bismuth molybdates fall into an unusual class of compounds, the ternary bismuth oxide systems Bi-M-0 (where M = Mo, W, V, Nb, and Ta) which exhibit a variety of interesting physical and chemical properties. Of commercial importance, the bismuth molybdates are heterogeneous catalysts for selective oxidations and ammoxidations (the Sohio process), for example, propylene ( 311 ) to acrolein (C3H4O) by oxidation or to acrylonitrile (C3H3N) by arrunoxidation. ... 

All selective oxidation and ammoxidation catalysts possess redox properties. They must be capable not only of reduction during the formation of acrolein or acrylonitrile, but also subsequent catalyst reoxidation in which gaseous oxygen becomes incorporated into the lattice as to replenish catalyst vacancies (Scheme 2). As mentioned earlier, the incorporation of such redox properties into solid state metal oxides was one of the salient working hypotheses on which the development of the Sohio ammoxidation process was based (2). Later, Keulks (70) confirmed the involvement of lattice oxygen in propylene oxidation by using as a vapor phase oxidant. The results showed that the incorporation of O into the acrolein (and CO2) increases with time (Fig. 11), which is consistent with the above redox mechanism. 

The development of the Sohio ammoxidation process was based on the theory that lattice oxygen from a solid metal oxide would serve as a more selective and versatile oxidant ... 

The SOHIO ammoxidation process was developed since 1957. Production capacity for acrylonitrile, the most important product derived from propene, is greater than 4x10 t/a, of which over 70 % is produced by the SOHIO process. Plants are constructed with capacities of up to 180000 t/a. There are numerous variants of ammoxidation, the following products also being produced by this process ... 

Molybdate-Based Catalysts. The first catalyst commercialized by SOHIO for the propylene ammoxidation process was bismuth phosphomolybdate, Bi9PMoi2052, supported on silica (9). The catalytically active and selective component of the catalyst is bismuth molybdate. In commercial fluid-bed operation, the bismuth molybdate catalyst is supported on silica to provide hardness and attrition resistance in the fluidizing environment. Bismuth molybdate catalysts can be prepared by a coprecipitation procedure using aqueous solutions of bismuth nitrate and ammonium molybdate (10). The catal3ret is produced by drying the precipitate and heat treating the dried particles to crystallize the bismuth molybdate phase. Heat treatment temperature for bismuth molybdate catalysts is generally arovmd 500°C. 

Widespread successful process Very successful SOHIO ammoxidation process Oxychlorination of ethylene successful process Naphthalene partial oxidation supplanted by fixed-bed process... 

Acrylonitrile is currently the second largest outlet for propylene (after polypropylene). It is used as a monomer for synthetic fibers and acrylic plastics (thermoplastics and food packaging mainly), AS (acrylonitrile-styrene) resins, and ABS (aerylonitrile-butadiene-styrene) thermoplastics, as well as in the synthesis of acrylamide, adiponitrile, and nitrile elastomers. The manufacture of acrylonitrile is exclusively based on the one-step propylene ammoxidation process. Originally developed by Sohio, Standard Oil Company (now part of BP America), the conventional method used since 1957 employs a fluidized-bed reactor and multicomponent catalysts based on Mo-containing mixed-metal oxides. Over the years, the industrial... 

Addition of Hydrogen Cyanide. At one time the predominant commercial route to acrylonitrile was the addition of hydrogen cyanide to acetylene. The reaction can be conducted in the Hquid (CuCl catalyst) or gas phase (basic catalyst at 400 to 600°C). This route has been completely replaced by the ammoxidation of propylene (SOHIO process) (see Acrylonitrile). 

Oxidation Catalysis. The multiple oxidation states available in molybdenum oxide species make these exceUent catalysts in oxidation reactions. The oxidation of methanol (qv) to formaldehyde (qv) is generally carried out commercially on mixed ferric molybdate—molybdenum trioxide catalysts. The oxidation of propylene (qv) to acrolein (77) and the ammoxidation of propylene to acrylonitrile (qv) (78) are each carried out over bismuth—molybdenum oxide catalyst systems. The latter (Sohio) process produces in excess of 3.6 x 10 t/yr of acrylonitrile, which finds use in the production of fibers (qv), elastomers (qv), and water-soluble polymers. 

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). 

Two synthesis processes account for most of the hydrogen cyanide produced. The dominant commercial process for direct production of hydrogen cyanide is based on classic technology (23—32) involving the reaction of ammonia, methane (natural gas), and air over a platinum catalyst it is called the Andmssow process. The second process involves the reaction of ammonia and methane and is called the BlausAure-Methan-Ammoniak (BMA) process (30,33—35) it was developed by Degussa in Germany. Hydrogen cyanide is also obtained as a by-product in the manufacture of acrylonitrile (qv) by the ammoxidation of propjiene (Sohio process). 

Ammoxidation illustrates several principles. First, it shows the benefit of telescoping two successive processes into one reactor. The Sohio inventor, James D. Idol, Jr., observed that catalysts for two successive stages in an earlier ammoxidation procedure were very similar. He then found that the same catalyst could be used for both, thus eliminating a complete plant stage, at great saving of capital and operating cost ... 

Production of acrylonitrile by ammoxidation of propylene (SOHIO process) ... 

Using the Kunii-Levenspiel bubbling-bed model of Section 23.4.1 for the fluidized-bed reactor in the SOHIO process for the production of acrylonitrile (C3H3N) by the ammoxidation... 

The crucial factor in the successful use of the fluidized-bed reactor for the synthesis of acrylonitrile by the ammoxidation of propenc (Sohio process) was... 

BP Sohio and Asahi are developing processes for the ammoxidation of propane to produce ACRN. This process is believed to yield a lower level of HCN than the optimized oxidation of propylene.131 In 2007 Asahi started up a propane process in Tongsuh, South Korea. 

The initial drive for acrylonitrile (AN) production (6.2 Mt/a in 2004 worldwide) was the discovery, in the late 1930s, of the synthetic rubber Buna N. Today nitrile rubbers represent only a minor outlet for AN which is utilized primarily for polymerization to give textile fibres (50%) and ABS resins (24%), and for dimerization to adiponitrile (10%). Early industrial processes depended on the addition of hydrogen cyanide to acetylene or to ethylene oxide, followed by the dehydration of intermediate ethylene cyanohydrin. Both processes are obsolete and are now supplanted by the ammoxidation of propylene (Equation 34) introduced in 1960 by Standard Oil of Indiana (Sohio). The reason for the success stems from the effectiveness of the catalyst and because propylene,... 

Figure 20.3 Schematic flow sheet of the SOHIO process of propene ammoxidation to acrylonitrile. Adapted from [11].

The Sohio process is considered one of the most successful applications of FCB. Problems in industrial application of the reaction arose from the strong exothermicity of propylene ammoxidation and from the intermediate production of acrylonitrile in the consecutive reactions (V9). It is particularly noticeable that the catalyst gives high selectivity, and the reactor design aims at better fluidization and higher contact efficiency than in the FCC process. 

Ammoxidation refers to the catalytic oxidation of a feedstock with ammonia. When propylene is the feedstock, acrylonitrile is produced. Most of the world s acrylonitrile is based on the Sohio (now BP) process in which stoichiometric amounts of propylene and ammonia are reacted with a slight excess of air in a fluidized bed operated in the turbulent fluidization flow regime. The reactor temperature and pressure are 450° C and 1.5 bar, respectively. The reaction usually... 

The ammoxidation reaction, which is by far the largest-scale industrial allylic oxidation process, was originally discovered and developed at Sohio (2) in the early 1960s. This process, by which more than a million tons of acrylonitrile are produced annually in the United States and more than 4 million tons worldwide, revolutionized the manufacture of this important monomer, displacing the more expensive acetylene-HCN-based route (Eq. 9) ... 

Although a large number of its basic patents already He in the public domain, the process commercialized by Sohio, concerning the ammoxidation of propylene, has acquired a virtual monopoly in view of the technological know-how accumulated in the past decade. 

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