Sohio processes acrylonitrile

Ammoxidation of propene to acrylonitrile (SOHIO process) a mixture of propene, ammonia, and air reacts on a Bi/Mo oxide catalyst 400-500 °C, 0.3-2 bar, high gas throughput, small catalyst particles (mean particle diameter ca. 50 pm) the high heat of reaction is removed by cooling coils incorporated in the fluidized bed. 

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. 

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). 

Acrylonitrile. Acrylonitrile is produced by reacting propylene, ammonia, and owgeu (air) in a single flmdized bed of a complex catalyst. Known as the SOHIO process, this process was first operated commercially in 1960. In addition to acrylonitrile, significant quantities of HCN and acetonitrile are also produced. This process is also exothermic. Temperature control is achieved by raising steam inside vertical tubes immersed in the bed [Veatch, Hydrocarbon Proce.ss. Pet. Refiner, 41, 18 (November 1962)]. 

Made by the reaction of propylene with ammonia and air (the Sohio process). This is the basis for the production of all of the acrylonitrile made in the world. Recoverable and salable by-products include hydrogen cyanide (HCN) and acetonitrile (CH3CN). 

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... 

Practically complete conversion of propylene and ammonia is achieved to produce acrylonitrile in 65-70% yield. Acetonitrile and HCN are the main byproducts. The Sohio process originally used oxides of Bi, Co, and Mo, and bismuth and cobalt molybdates.898,915,941,953 Other catalysts developed later (uranyl antimonate antimony oxide-iron oxide oxides of Fe, Ce, and Mo mixed oxides of Sb and Sn)898,915,939,953,955,956 produce fewer byproducts and ensure higher yields of acrylonitrile. 

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

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. 

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. ... 

The process was developed by Monsanto to use the hydrogen cyanide byproduct of acrylonitrile from the Sohio process [64], However, synthetic lactic acid is not as competitive as that from the fermentation of starch or sugar [65]. 

In the first step, this method is comparable to the Sohio process for manufacturing acrylonitrile from propylene (see Section 11.4). The remaining steps are similar to the production of acrylates from acrylonitrile (see Section 113.23). The operating conditions, catalysts and performance are substantially the same, and the major drawback is the formation of ammonium sulfate as a by-product... 

Commercial plants INEOS is the world s largest manufacturer and marketer of acrylonitrile. With four wholly-owned, world-scale acrylonitrile plants (in Lima, Ohio Green Lake, Texas Koein, Germany Teeside, UK), INEOS has extensive manufacturing expertise and commercial experience in the international marketplace. INEOS total acrylonitrile production capacity is approximately 1.3 million tpy. The SOHIO process was first licensed in 1960. Since then, through more than 45 years of licensing expertise and leadership, INEOS has licensed this technology into over 20 countries around the world. 

The true SOHIO process is in fact the ammoxidation of propene with NH3 and atmospheric oxygen in a highly exothermic reaction to give acrylonitrile (Eq. 8-8). 

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 ... 

Today the most cost-effective processes are those based on propylene as the starting material. There are three major variations of propylene processes, the Distillers process [21-23], the Sohio process [24], and the DuPont process [25,26]. All three processes are based on the ammonoxidation of propylene. The Distillers process is carried out in two stages. In the first, propylene is oxidized in air to form acrolein and water. These intermediate products are allowed to react in the second stage with ammonia in the presence of molybdenum oxide and air to form crude acrylonitrile. The pure monomer is recovered by a series of azeotropic distillations. The Sohio process is carried out in just one stage. Ammonoxidation of propylene takes place in air at 2-3 atmospheric pressure and 425-510°C. With catalysts, such as concentrated bismuth phosphomolybdate or other oxides of molybdenum and cobalt, the reaction takes place with over 50% yield in a reaction time of only about 15 s. In the DuPont version of this process, the ammonoxidation is brought about with nitric oxide at 500°C using silver on silica catalyst. The chemistry of acrylonitrile monomer has been reviewed by a number of authors [27-30]. 

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. 

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. 

Pig. 1. Propylene ammoxidation to acrylonitrile by the SOHIO process. Reprinted from Ref. (8), Cop3rright (1991), with permission from John Wiley Sons, Inc. 

More than half of the worldwide acrylonitrile production is situated in Western Europe and the United States (Table 3). In the United States, production is dominated by BP Chemicals with the Sohio Process, with more than a third of the domestic capacity (Table 4). Nearly one-half of the US. production was exported in 1997 (Table 5), with most going to Far East Asia. 

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. 

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