DuPont process

The DuPont process (the oldest syngas process to produce ethylene glycol) reacts formaldehyde with CO in the presence of a strong mineral acid. The intermediate is glycolic acid, which is esterified with methanol. The ester is then hydrogenated to ethylene glycol and methanol, which is recovered. The net reaction from either process could he represented as ... 

As already stated, the actual manufacture of NC is described in detail in Vol 2. A diagrammatic representation of the Dupont process (typical of US production practice), shown in Fig 14, complements the discussion presented in Vol 2... 

It is important that chemical engineers master an understanding of metabolic engineering, which uses genetically modified or selected organisms to manipulate the biochemical pathways in a cell to produce a new product, to eliminate unwanted reactions, or to increase the yield of a desired product. Mathematical models have the potential to enable major advances in metabolic control. An excellent example of industrial application of metabolic engineering is the DuPont process for the conversion of com sugar into 1,3-propanediol,... 

Hydrocyanation represents a reaction of considerable economic importance largely due to the value of the DuPont process involving HCN addition to butadiene to afford adiponitrile.61,62 The mechanism is well known, and involves (i) oxidative addition of H-CN to a coordinatively unsaturated metal complex, (ii) coordination of an alkene to the H-M-CN species, (iii) migratory... 

Isomerisation is also an important step in the DuPont process for making adiponitrile (Chapter 11) in which internal pentenenitriles must be converted to the terminal alkene. The catalyst is the same as that used for the hydrocyanation reaction, namely nickel(II) hydrides containing phosphite ligands. 

Byproducts of large industrial-scale processes are valorized for instance, in the DuPont process for adiponitrile, the byproduct a-methylglutaronitrile is upgraded to p-picoline and further to niacinamide. 

Among other nonaddition processes, adiponitrile may be manufactured by the direct hydrocyanation of 1,3-butadiene (DuPont process).169 172,187 196 A homogeneous Ni(0) complex catalyzes both steps of addition of HCN to the olefinic bonds (Scheme 6.4). The isomeric monocyano butenes (20 and 21) are first formed in a ratio of approximately 1 2. All subsequent steps, the isomerization of 20 to the desired 1,4-addition product (21), a further isomerization step (double-bond migration), and the addition of the second molecule of HCN, are promoted by Lewis acids (ZnCl2 or SnCl2). Without Lewis acids the last step is much slower then the addition of the first molecule of HCN. Reaction temperatures below 150°C are employed. 

In the Dupont process, cyclohexane is reacted with air at 150 °C and 10 atm pressure in the presence of a soluble cobalt(II) salt (naphthenate or stearate). The conversion is limited to 8-10% in order to prevent consecutive oxidation of the ol-one mixture. Nonconverted cyclohexane is recycled to the oxidation reactor. Combined yields of ol-one mixture are 70-80%.83,84,555 The ol-one mixture is sent to another oxidation reactor where oxidation by nitric acid is performed at 70-80 °C by nitric acid (45-50%) in the presence of a mixture of Cu(N03)2 and NH4V03 catalysts, which increase the selectivity of the reaction. The reaction is complete in a few minutes and adipic acid precipitates from the reaction medium. The adipic acid yield is about 90%. Nitric acid oxidation produces gaseous products, mainly nitric oxides, which are recycled to a nitric acid synthesis unit. Some nitric acid is lost to products such as N2 and N20 which are not recovered. 

Propanediol is produced either from the reductive hydration of acrolein (Degussa-DuPont process), or through reductive carbonylation of ethylene oxide (Shell process), or through fermentation of glucose via glycerol (DuPont-Genencor process). 

Figure 20.12 Overview of the DuPont process to polypropylene terephthalate) (3-GT, Sorona ) (Ray Miller, DuPont).

Methanol is oxidized to formaldehyde in a thin layer of finely divided silver or a multilayer screen, with a contact time of 0.01 s at 450 to 600°C (842 to 1112°F). A shallow bed of silver catalyst is also used in the DuPont process for in situ production of methyl isocyanate by reacting monomethlyformamide and oxygen at 500°C. 

Fig. 10.30. Maleic anhydride DuPont process. Chem Systems Report No. 99/00-5. Copyright Nexant Chem Systems, Inc. and used by permission of the copyright owner.)... 

DuPont and Dow use solution polymerization technology to produce LLDPE resins. The process is based on continuous polymerization of ethylene with 1-octene in cyclohexane at about 250°C and 1200 psi. The catalyst is again Ziegler type. Residence time is of the order of several minutes. The catalyst is deactivated by treatment with an alcohol or complexing agent such as acetyl-acetone, and adsorbed on a silaceous adsorbent before stripping the solvent. The Stamicarbon (Dutch State mines) process is similar to the DuPont process, and it uses a short-residence-time solution process for HDPE production. 

Alternatively, caprolactam can be produced from butadiene, via homogeneous nickel-catalysed addition of HCN (DuPont process) followed by selective catalytic hydrogenation of the adiponitrile product to the amino nitrile and vapor phase hydration over an alumina catalyst (Rhodia process) as shown in Fig. 1.49 [137]. 

Although not all the fine details of the DuPont process have been disclosed, enough is known to show the fascinating chemistry underlying it. For example nickel(O) is probably a better catalyst than palladium(O) (coordinated by the... 

Blanchard, W. A., Rhode, J. C. (DuPont). Process for Preparing Perfluoroalkyl Iodides. US Patent Number 3226449, 1965. 

Another approach developed by Lummus Co is used commercially for isophtha-lonitrile production from m-xylene [118]. Oxidation is carried out in the absence of gaseous oxygen (ammonolysis) using lattice oxygen from the catalyst, which is regenerated in a separate vessel. The approach is analogous to the Dupont process... 

In the Dupont process, cyclohexane is reacted with air at 150 °C and 10 atm pressure in the presence of a soluble cobalt(ll) salt (naphthenate or stearate). The conversion is limited to 8-10% in order to prevent consecutive oxidation of the ol-one mixture. Nonconverted cyclohexane is... 

The process yields butanediol as a coproduct. A schematic of the DuPont process is shown in Figure 3.44 [133]. 

Technical note, A DuPont process may lead to H2O2 satellite plant, Chem Week, Dec. 9 20 (1987). 

Description Aniline is produced by the nitration of benzene with nitric acid to mononitrobenzene (MNB) which is subsequently hydrogenated to aniline. In the DuPont process, purified MNB is fed, together with hydrogen, into a liquid phase plug-flow hydrogenation reactor that contains a DuPont proprietary catalyst. The supported noble metal catalyst has a high selectivity and the MNB conversion per pass is 100%. 

Reppe reactions are the formation of carboxylic acids from olefins by reaction with carbon monoxide and water utilizing a metal carbonyl catalyst. The same reactants combine to form carboxylic acids in the presence of an acid catalyst. These acid catalyzed reactions are known as Koch Carbonyla-tion reactions. Commercial processes utilizing this route are the DuPont process for glycolic acid from carbon monoxide and formaldehyde and the carbonylation of olefins to neo acids practiced by Exxon and Shell. 

Isomerization processes involving homogeneous catalysts are mostly intermediate steps in industrial processes. For example, in the Shell oxo process, inner olefins are converted to primary alcohols. The isomerization occurs prior to CO insertion. The key step in the above mentioned DuPont process is the isomerization of 2-methyl-3-butenenitrile to a linear nitrile. A further example is the CU2CI2 catalyzed isomerization of dichlorobutenes [10]. 

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