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.

Processes rendered obsolete by the propylene ammoxidation process (51) include the ethylene cyanohydrin process (52—54) practiced commercially by American Cyanamid and Union Carbide in the United States and by I. G. Farben in Germany. The process involved the production of ethylene cyanohydrin by the base-cataly2ed addition of HCN to ethylene oxide in the liquid phase at about 60°C. A typical base catalyst used in this step was diethylamine. This was followed by liquid-phase or vapor-phase dehydration of the cyanohydrin. The Hquid-phase dehydration was performed at about 200°C using alkah metal or alkaline earth metal salts of organic acids, primarily formates and magnesium carbonate. Vapor-phase dehydration was accomphshed over alumina at about 250°C. 

A new ammoxidation process uses less hazardous raw materials (propylene and ammonia (Dale, 1987 Puranik et al., 1990). 

This process does produce HCN as a by-product in small quantities. Puranik et al. (1990) report on work to develop an improved, more selective catalyst, and on coupling the ammoxidation process with a second reactor in which a subsequent oxycyanation reaction would convert the by-product HCN to acrylonitrile. 

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

Erdolchemie A process for treating the waste from the ammoxidation process for making acrylonitrile, yielding ammonium sulfate. Developed by the eponymous German company, a joint venture of Bayer and BP Chemicals. 

Kurtz A process for making acrylonitrile by reacting hydrogen cyanide with acetylene in the presence of aqueous cuprous chloride. Invented by R Kurtz at I. G. Farbenindustrie in the 1940s. The process was widely used, but by 1970 had been abandoned in the United States in favor of the ammoxidation processes. 

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. 

The cost of producing acrylonitrile dropped when the ammoxidation process was introduced in the 1960s. Then it became economical at that time to produce methyl and ethyl esters of acrylic acid by hydrolyzing acrylonitrile in the presence of alcohol. The hydrolysis and esterification take place at the same time, in the presence of sulfuric acid at about 225°F. Yields are about 98%. 

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. 

The main route to ACRN is the one-step propylene ammoxidation process. In this process propylene, ammonia and air reacted in a fluidized bed reactor to produce ACRN with acetonitrile and hydrogen cyanide as by-products. New technology based on propane ammoxidation has been developed by BP, Mitsubishi (in conjunction with BOC) and Asahi Kasei with claims of a 30% production cost advantage over the propylene route276. However no plans have been announced to build a propane-based plant as of first quarter 2004 297. 

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 ammoxidation process could be also used in the conversion of less-conventional molecules. Various examples are discussed in detail, and it can be remarked that owing to the relatively limited research effort, there is still a relatively large degree of possible improvement. The need for more reproducible results in some cases is also stressed. Nevertheless, this field could offer new interesting commercial opportunities. 

Although still limited, there is also some interest in using biomass-derived raw materials (bio-ethanol, glycerine) in ammoxidation processes. These processes could be of value only in the context of valorization of side streams in bio-refinery plants. However, owing to the growing interest in the latter, it may be expected that some opportunities will arise for the ammoxidation of biomass-derived side-products in the near future. 

All selective oxidation and ammoxidation catalysts possess redox properties. They must be capable not only of reduction during the formation of acrolein or acrylonitrile, but also subsequent catalyst reoxidation in which gaseous oxygen becomes incorporated into the lattice as to replenish catalyst vacancies (Scheme 2). As mentioned earlier, the incorporation of such redox properties into solid state metal oxides was one of the salient working hypotheses on which the development of the Sohio ammoxidation process was based (2). Later, Keulks (70) confirmed the involvement of lattice oxygen in propylene oxidation by using as a vapor phase oxidant. The results showed that the incorporation of O into the acrolein (and CO2) increases with time (Fig. 11), which is consistent with the above redox mechanism. 

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