Acrylonitrile plant process

An acrylonitrile plant eliminated 500,000 pounds of in-process storage of hydrogen cyanide by accepting a shutdown of the entire unit when the product purification area shut down. This forced the plant staff to solve the problems which caused the purification area shutdowns. 

In 2003 Mitsubishi Rayon was believed to be operating a commercial-scale, methanol-based HCN process and had offered to license the technology to other companies. The technology might provide a low-cost way to convert an acrylonitrile plant to HCN-only production. However methanol is a higher cost source of carbon compared to natural gas so the methanol process probably has a higher operating cost than the Andrussow process. 

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. 

One day, Lee, a process engineer in an acrylonitrile plant, runs into a former classmate at a technical society luncheon. The friend has recently taken a job as a regional conpliance officer for OSHA and reveals, after several drinks, that there will be an unannounced inspection of Lee s plant. In a telephone conversation a few days later, the friend mentions that the inspection will occur on the following Tuesday. 

Adiponitrile is made commercially by several different processes utilizing different feedstocks. The original process, utilizing adipic acid (qv) as a feedstock, was first commercialized by DuPont in the late 1930s and was the basis for a number of adiponitrile plants. However, the adipic acid process was abandoned by DuPont in favor of two processes based on butadiene (qv). During the 1960s, Monsanto and Asahi developed routes to adiponitrile by the electrodimerization of acrylonitrile (qv). 

Although some very minor manufacturers of acryhc acid may still use hydrolysis of acrylonitrile (see below), essentially all other plants woddwide use the propylene oxidation process. 

These processes use expensive C2 hydrocarbons as feedstocks and thus have higher overall acrylonitrile production costs compared to the propylene-based process technology. The last commercial plants using these process technologies were shut down by 1970. 

The propylene-based process developed by Sohio was able to displace all other commercial production technologies because of its substantial advantage in overall production costs, primarily due to lower raw material costs. Raw material costs less by-product credits account for about 60% of the total acrylonitrile production cost for a world-scale plant. The process has remained economically advantaged over other process technologies since the first commercial plant in 1960 because of the higher acrylonitrile yields resulting from the introduction of improved commercial catalysts. Reported per-pass conversions of propylene to acrylonitrile have increased from about 65% to over 80% (28,68—70). 

Essentially all the ammonium sulfate fertilizer used in the United States is by-product material. By-product from the acid scmbbing of coke oven gas is one source. A larger source is as by-product ammonium sulfate solution from the production of caprolactam (qv) and acrylonitrile, (qv) which are synthetic fiber intermediates. A third but lesser source is from the ammoniation of spent sulfuric acid from other processes. In the recovery of by-product crystals from each of these sources, the crystallization usually is carried out in steam-heated sa turator—crystallizers. Characteristically, crystallizer product is of a particle size about 90% finer than 16 mesh (ca 1 mm dia), which is too small for satisfactory dry blending with granular fertilizer materials. Crystals of this size are suitable, however, as a feed material to mixed fertilizer granulation plants, and this is the main fertilizer outlet for by-product ammonium sulfate. 

Plants for the production of sodium cyanide from Andmssow process or from acrylonitrile synthesis by-product hydrogen cyanide are operating in the United States, Italy, Japan, the UK, and AustraUa. In Germany, sodium cyanide is produced from BMA hydrogen cyanide, and in AustraUa one plant uses Fluohmic process hydrogen cyanide. 

The first U.S. plant for acrylonitrile manufacture used an ethylene cyanohydrin feedstock. This was the primary route for acrylonitrile manufacture until the acetylene-based process began to replace it in 1953 (40). Maximum use of ethylene cyanohydrin to produce acrylonitrile occurred in 1963. Acrylonitrile (qv) has not been produced by this route since 1970. 

Application of Mass Integration to Enhance Yield, Debottleneck the Process and Reduce Wastewater In an Acrylonitrile an Plant... 

An example of the way in which process competition works in the manufacture of plastics is the story of acrylonitrile. The first process for the production of this plastic was based upon the reaction between hydrogen cyanide and acetylene, both hard to handle, poisonous, and explosive chemicals. The raw material costs were relatively low as compared to materials for other monomers, but the plant investment and manufacturing costs were too high. As a result, originally acrylonitrile monomer (1950s) sold for about 30 cents per pound and the future of the material looked dim as other plastics such as polyethylene became available at much lower prices due to their lower production costs. 

The second principle was the great defensive strength of an established, capital intensive procedure. In the overall process for making acrylonitrile via acetylene, very big plants were needed for making the acetylene either by partial oxidation of methane or from carbide furnaces. Manufacture of HCN from methane involved further expense ... 

Hexamethylenediamine is now made by three different routes the original from adipic acid, the electrodimerization of acrylonitrile, and the addition of hydrogen cyanide to butadiene. Thus, the starting material can be cyclohexane, propylene, or butadiene. Currently, the cyclohexane-based route from adipic acid is the most costly and this process is being phased out. The butadiene route is patented by DuPont and requires hydrogen cyanide facilities. Recent new hexamethylenediamine plants, outside DuPont, are based on acrylonitrile from propylene, a readily available commodity. 

Hexamethylenediamine (HMDA), a monomer for the synthesis of polyamide-6,6, is produced by catalytic hydrogenation of adiponitrile. Three processes, each based on a different reactant, produce the latter coimnercially. The original Du Pont process, still used in a few plants, starts with adipic acid made from cyclohexane adipic acid then reacts with ammonia to yield the dinitrile. This process has been replaced in many plants by the catalytic hydrocyanation of butadiene. A third route to adiponitrile is the electrolytic dimerization of acrylonitrile, the latter produced by the ammoxidation of propene. 

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

The early ammoxidation plants were a two-step design. Propylene was catalytically oxidized to acrolein (CH2=CHCHO). The acrolein was then reacted with ammonia and air at high temperature to give acrylonitrile. The one-step process has replaced most of this hardware. 

Acrylonitrile was first produced in Germany and the United States on an industrial scale in the early 1940s. These processes were based on the catalytic dehydration of ethylene cyanohydrin. Ethylene cyanohydrin was produced from ethylene oxide and aqueous hydrocyanic acid at 60°C in the presence of a basic catalyst. The intermediate was then dehydrated in the liquid phase at 200°C in the presence of magnesium carbonate and alkaline or alkaline earth salts of fonnic acid. A second commercial route to acrylonitrile was the catalytic addition of hydrogen cyanide to acetylene. The last commercial plants using these process technologies were shut down in 1970 (Langvardt, 1985 Brazdil, 1991). 

During the history of a half century from the first discovery of the reaction (/) and 35 years after the industrialization (2-4), these catalytic reactions, so-called allylic oxidations of lower olefins (Table I), have been improved year by year. Drastic changes have been introduced to the catalyst composition and preparation as well as to the reaction process. As a result, the total yield of acrylic acid from propylene reaches more than 90% under industrial conditions and the single pass yield of acrylonitrile also exceeds 80% in the commercial plants. The practical catalysts employed in the commercial plants consist of complicated multicomponent metal oxide systems including bismuth molybdate or iron antimonate as the main component. These modern catalyst systems show much higher activity and selectivity... 

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