DSM process

A plant is to be designed for the production of 300,000 kg per day of urea by the reaction of ammonia and carbon dioxide at elevated temperature and pressure, using a total-recycle process in which the mixture leaving the reactor is stripped by the carbon dioxide feed (DSM process, references 1 to 4). 

Numerous other technologies, mainly gas-phase hydrogenations, were developed over the years (Sinclair-Engelhard,333,334 Hytoray,335,336 Arco,337 DSM,338 UOP339). The Arco and DSM processes operate at 400°C and under 25-30 atm. Despite the high temperature, isomerization is negligible because of the very short contact time. 

Figure 7.25 Toyo Soda/DSM process for the enzymatic production of aspartame.

Production of Amino Acids Using Amidases the DSM Process... 

The DSM process (which is more commonly practiced) converts cyclohexane to cyclohexanone in two steps. In the first step, cyclohexane is contacted with air at high temperatures (165 ) and pressures (45 - 150 psig). A variety of radical initiators are used as catalysts. The process require a residence time of 5.5 hours. The conversions are usually low (4 - 23%). The major products are cyclohexanol and cyclohexanone (formed in 2 1 ratio) along with a large number of byproducts. (At higher conversions, the byproducts accumulate at the expense of cyclohexanol and cyclohexanone.) The unreacted cycohexane is separated from the products by fractional distillation and recycled. 

The Dowlex process by Dow Chemicals is the dominant process in solution polymerization, but Dow does not license this technology to other companies (Figure 2.39). The Dowlex process uses two CSTRs in series with a high boiling hydrocarbon solvent. Other competing processes include the DSM process and the Sclairtech process by Nova Chemicals. In some configurations, these processes may also have tubular reactors operated in series with the CSTR to complete monomer conversion. 

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