Bismuth molybdate SOHIO process

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. 

Patents claiming specific catalysts and processes for thek use in each of the two reactions have been assigned to Japan Catalytic (45,47—49), Sohio (50), Toyo Soda (51), Rohm and Haas (52), Sumitomo (53), BASF (54), Mitsubishi Petrochemical (56,57), Celanese (55), and others. The catalysts used for these reactions remain based on bismuth molybdate for the first stage and molybdenum vanadium oxides for the second stage, but improvements in minor component composition and catalyst preparation have resulted in yields that can reach the 85—90% range and lifetimes of several years under optimum conditions. Since plants operate under more productive conditions than those optimum for yield and life, the economically most attractive yields and productive lifetimes maybe somewhat lower. 

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. 

These enable temperature control with built-in exchangers between the beds or with pumparound exchangers. Converters for ammonia, 80.3, cumene, and other processes may employ as many as five or six beds in series. The Sohio process for vapor-phase oxidation of propylene to acrylic acid uses hvo beds of bismuth molybdate at 20 to 30 atm (294 to 441 psi) and 290 to 400°C (554 to 752°F). Oxidation of ethylene to ethylene oxide also is done in two stages with supported... 

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. 

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. 

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. 

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. ... 

This process is known as the SOHIO (Standard Oil of Ohio Company) process. The bismuth-molybdate catalyst functions by providing intimately associated Bi—O and Mo=0 sites. The Bi—O sites are involved in abstracting a-hydrogen (see structure 24.47) while the Mo=0 sites interact with the incoming alkene, and are involved in activation of NH3 and in C—N bond formation. 

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. 

Acrylonitrile is produced today almost exclusively by ammonoxidation of propylene using the so-called Sohio process. Sohio stands for Standard Oil of Ohio, the first company to demonstrate successfully the process in 1960. The Sohio process reacts propylene, ammonia, and oxygen in a highly exothermic process (AH = —502 kj mol ) at 400-500 °C to acrylonitrile and water. The process uses a fluidized bed reactor to operate the reactor as isothermally as possible. The catalyst is a Fe-modified bismuth-phosphorous molybdate contact. The Sohio process has... 

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