Industrial processes SOHIO process

Mehta (34) has carried out a reactor network optimization study to find improved designs for the production of acrylonitrile in a collaboration between UMIST and one of its industrial partners. Most industrial installations employ fluidized-bed reactors (BP/Sohio process) with a well-mixed reaction zone. Previous process improvements have mainly resulted from better catalysts, which have produced an increase in yield from 58% to around 80%. The reaction model employed in the optimization study is taken from Ref. 81 and considers seven reactions and eight components. Air, pure oxygen, and propylene are available as raw material streams. The optimization study assumes negligible pressure drop along the reaction sections, isothermal and isobaric operation, and negligible mass gas-solid transfer effects. 

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,... 

Perhaps the most successful application since FCC is the Sohio process. The reasons for the success are explained as follows. First, the process achieved high conversion and selectivity in FCB, even in a reaction system involving several parallel and consecutive reactions. Second, the process was industrialized directly by the use of fluid beds, rather than by passing through the stage of fixed beds. Callahan a/. (Cl) have reported on development of the initial catalyst, bismuth molybdate, for the Sohio process. 

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. 

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) ... 

Racemic DL-lactic acid can be synthesized by fermentation using appropriate bacteria Lactobacillus helvetics in Table 1.1), but it is more easily synthesized by following the chemical process shown in Scheme 1.3. Here, the DL-lactic acid is produced by hydrolysis of lactonitrile that is generally formed by the addition reaction of acetaldehyde and hydrogen cyanide. Industrially, the lactonitrile is obtained as a by-product of acrylonitrile production (Sohio process).The lactic acid thus prepared is purified by distillation of its ester as described above. 

Many petrochemical industry processes are catalytic and give high yields of required products. To pick one at random, US aniline production runs at around 500 000 tonnes per annum, the main route is by the catalytic reduction of nitrobenzene with hydrogen under relatively mild conditions which gives a yield of around 99.5% [22]. At the same time these large scale processes can be quite sophisticated in terms of the molecules which are built. Almost all the world s acrylonitrile is produced from propylene by the SOHIO (now BP America) process ... 

Following this seminal discovery, SOHIO successfully commercialized its technology based on a bismuth-molybdenum oxide catalyst in 1960. The SOHIO process has since become the industry leader for acrylonitrile manufacture, with over 90% of the world s production based on this technology. The propylene-based process effectively displaced all the existing technologies for acrylonitrile that were based on acetylene feedstock, a much more expensive feedstock than propylene. This resulted in an explosion in the development of new applications for acrylonitrile stemming from the invention of the novel, lower cost production technology. 

Acetonitrile is produced as a by-product of the industrial Sohio process during the synthesis of acrylonitrile [163]. The C-alkylation of acetonitrile by transfer hydrogenation using methanol as an alkylating agent therefore represents an efficient route for the synthesis of functionahzed nitrile compounds. 

Acrylonitrile (AN) and methacrylonitrile (MAN) are commercially available products. They are colorless liquids and they may turn yellow in the presence of impurities. Most industrial AN and MAN are produced according to the Sohio process [42,43] corresponding to ammoxidation of propylene or isobutylene phase in the presence of a catalyst at 400-510°C. 

In 1957 Standard Oil of Ohio (Sohio) discovered bismuth molybdate catalysts capable of producing high yields of acrolein at high propylene conversions (>90%) and at low pressures (12). Over the next 30 years much industrial and academic research and development was devoted to improving these catalysts, which are used in the production processes for acrolein, acryUc acid, and acrylonitrile. AH commercial acrolein manufacturing processes known today are based on propylene oxidation and use bismuth molybdate based catalysts. 

Mountain states), Chevron (Standard of California), Exxon (from Standard of New Jersey), Sohio (Standard of Ohio), Marathon (covering western Ohio and other parts of Ohio not covered by Sohio), and Mobil (Standard of New York). These companies, derived from the Standard Oil Co., formed an original oil industry map in US, but that map no longer exist, rather the merging and acquisition processes reduced all them into four of the seven majors (ExxonMobil, ChevronTexaco, ConocoPhillips, and BP America). 

Fig. 10.21. Simplified diagram of the Sohio acrylonitrile process (a) fluidized-bed reactor (b) absorber column (c) extractive distillation column (d) acetonitrile stripping column (e) lights fractionation column (f) product column. (Patrick IV. Langvardt, Ullmann s Encyclopedia of Industrial Chemistry, IV. Gerhartz (Ed.), 5lh ed. Vol. A1, p.179, 1985. Copyright Wiley-VCH Verlag GmbH Co KG. Used with permission of the copyright owner and the author.)...

Simultaneously most petroleum and chemical companies have also brainstormed a safety review which asks "What-If" questions of the process (e.g. SOHIO ca. 1967). This is common practice in the industry and during design phases of a facility but was usually verbal and less formal in its application. Therefore not as much historical documentation is available on it, as compared to the HAZOP method. 

This process, which involves the indirect oxidation of propylene, developed initially by Sohio and Ugine, and then by various Japanese companies such as Asahi, Osaka Gas, Showa Denka anti Toyo Koatsu, is only used industrially today in Japan and Mexico. The main reasons restricting its commercialization are its low total yield compared with the direct oxidation of propylene, and the by-production in large quantities of sulfuric wastes that can be converted to ammonium sulfate, amounting to nearly 2 t/t of acrylate. 

With the Sohio technology, fluidized catalyst bed processes represent the most widespread industrial method. Lying far behind in the number of units installed, the PCUK/Distillers fixed bed technique is nevertheless the most widely used of competing processes. 

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... 

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