Acrylonitrile propylene ammoxidation process

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

Fig. 1. Process flow diagram of the commercial propylene ammoxidation process for acrylonitrile. BFW, boiler feed water.

In fact, over the last 30 years, the market as well as the supply situation for formic acid has been very dynamic. It has been affected by the development of several other major technologies. The commercialization of acetic acid by the carbonylation of methanol and the development of the Propylene ammoxidation process for acrylonitrile which replaced the cyanohydrin process both had a large impact on formic acid. 

Alcohol ammoxidation provides an option to augment the production of HCN and/or acetonitrile in a propylene ammoxidation process for producing acrylonitrile (103). This is accomplished by co-feeding alcohol or alcohol mixtures with propylene over conventional molybdate or antimonate ammoxidation catalysts under typical process conditions for propylene ammoxidation. 

It is an alternative to acetonitrile produced as a coproduct of the commercial propylene ammoxidation process for the manufacture of acrylonitrile (see above). Acetonitrile is used primarily in the pharmaceutical industry as a solvent in drug synthesis. Ethane ammoxidation has several potential advantages over coproduct acetonitrile. 

The potential exists for obtaining a higher purity acetonitrile product with lower recovery and purification costs, since the number and amount of coproducts are less with ethane ammoxidation than with the propylene ammoxidation process. The latter produces acrylonitrile, HCN, acrylic acid, and acrolein in addition to acetonitrile. 

Other Acrylonitrile Processes. Processes rendered obsolete by the propylene ammoxidation process (42) include the ethylene cyanohydrin process (43-45) practiced commercially by American Cyanamid and Union Carbide in the United States and by I. G. Farben in Germany. The process involves the production of ethylene cyanohydrin by the base-catalyzed addition of HCN to ethylene oxide in the liquid phase at about 60°C, and subsequent dehydration. 

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... 

Acrylonitrile Route. This process, based on the hydrolysis of acrylonitrile (79), is also a propylene route since acrylonitrile (qv) is produced by the catalytic vapor-phase ammoxidation of propylene. 

Because of the large price differential between propane and propylene, which has ranged from 155/t to 355 /1 between 1987 and 1989, a propane-based process may have the economic potential to displace propylene ammoxidation technology eventually. Methane, ethane, and butane, which are also less expensive than propylene, and acetonitrile have been disclosed as starting materials for acrylonitrile synthesis in several catalytic process schemes (66,67). 

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). 

Design a plant to produce 1 x 108 kg/year of acrylonitrile (CH2 CH.CN) from propylene and ammonia by the ammoxidation process. 

Acrylonitrile is produced commercially by the process of propylene ammoxidation, in which propylene, ammonia and air are reacted in a fluidized bed in the presence of a catalyst (EPA 1984, 1985a). Production in the United States has increased gradually over the past 20 years from 304,300 kkgain 1967 (Cogswell 1984) to 1,112,754 kkg in 1987 (USITC 1988). 

OSW [Osterreichische Stickstoff-Werke] An ammoxidation process for making acrylonitrile from propylene. Operated in Austria by the named company. 

PETROX An ammoxidation process for making acrylonitrile from propane or propylene. Developed by BOC Group and partially piloted in New Jersey. 

SNAM (2) An ammoxidation process for converting propylene to acrylonitrile. The catalyst is based on molybdenum/vanadium or bismuth, operated in a fluidized bed. Operated in Europe in 1968. 

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. 

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

Processes based on propane ammoxidation to manufacture acrylonitrile have also been developed,915 966 and BP has announced commercialization.966 Dehydrogenation at high reaction temperature (485-520°C), which is about 100°C higher than for propylene ammoxidation, results in the formation of propylene, which subsequently undergoes normal ammoxidation. Despite higher investments and the markedly lower selectivity (30-40%), the process can be economical because of the price difference between propylene and propane.966 Better selectivites can be achieved at lower (40-60%) conversions. 

ACRYLONITRILE. [CAS 107-13-1], Today over 90% of the approximately 4,000.000 metric tons of acrylonitrile (also called aciylic acid nitrile, propylene nitrile, vinyl cyanide, and propenoic acid nitrile) produced worldwide each year use the Soldo-developed ammoxidation process. Acrylonitrile is among the top 50 chemicals producedin the United States as aresult of the tremendous growth m its use as a starting material for a wide range of chemical and polymer products. Acrylic fibers remain the largest use of acrylonitrile other significant uses are in resins and nitrile elastomers and as an intermediate in the production of adiponitnle and acrylamide. 

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. 

Acrylonitrile 100 000 tonnes Fixed-bed catalytic reactor for ammoxidation process for propylene and ammonia reaction. 

In 1960, almost all of the 260 million lb annual production of acrylonitrile was based on acetylene. Ten years later, the volume had risen to 1.1 billion lb, which was based almost entirely on an ammoxidation process with ammonia, propylene, and air as feeds. However, in the latter 1980s the growth rate had slowed considerably. 

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. 

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