Exxon process

Commercial production of these acids essentially follows the mechanistic steps given. This is most clearly seen in the Exxon process of Figure 1 (32). In the reactor, catalyst, olefin, and CO react to give the complex. After degassing, hydrolysis of this complex takes place. The acid and catalyst are then separated, and the trialkylacetic acid is purified in the distillation section. The process postulated to be used by Shell (Fig. 2) is similar, with additional steps prior to distillation being used. In 1980, the conditions used were described as ca 40—70°C and 7—10 MPa (70—100 bar) carbon monoxide pressure with H PO —BF —H2O in the ratio 1 1 1 (Shell) or with BF (Enjay) as catalyst (33). 

In the following sections a few typical processes will be described. An example of a cobalt catalysed hydroformylation reaction for higher alkenes is the Kuhlmann process (now Exxon process), for which the flow-scheme -a liquid/liquid separation- is shown in Figure 7.4. In this process the hydroformylation is done in one, organic phase consisting of alkene and aldehyde. The reactor is often a loop reactor or a reactor with an external loop to facilitate heat transfer. 

Low- to medium-molecular-weight polyisobutylenes are produced at —10 to —40°C. In the Exxon process 30% isobutylene in hexane is polymerized in the... 

Butyl rubber is one product formed when isobutylene is copolymerized with a few percents of isoprene. In the Exxon process an isobutylene-methyl chloride mixture containing a small amount of isoprene is mixed at — 100°C with a solution of AICI3 in methyl chloride. An almost instantaneous reaction yields the product, which is insoluble in methyl chloride and forms a fine slurry. Molecular weight can be controlled by adding diisobutylene as a chain-transfer agent. Increased catalyst concentration and temperature also result in lowering molecular weight. The product can be vulcanized and is superior to natural rubber. A solution process carried out in C5-C7 hydrocarbons was developed in the former Soviet Union.471,472... 

Preservation of the once-formed Co(CO)4 by extraction with aqueous caustic and reformation of HCo(CO)4 by subsequent acidification (Kuhlmann or Exxon process). 

Figure 10. Flow sheet of the Exxon process (Kuhlmann technology).

The engineering of the Exxon process is beneficial because the catalyst does not undergo decomposition and is introduced in its most active and effective form. However, all the stages of catalyst separation and recycling have to be car-... 

The Exxon process for diesel oil production with sulfur levels between 200-500 ppm was introduced in 1989. The process is particularly interesting for feeds containing cracked stocks. The low pressure results in an efficient use of hydrogen in diesel upgrading. Since its introduction 9 units have been licensed outside the Exxon group. Various catalysts are approved for this process. RT 601 is the most active one. 

Brief descriptions of commercial gasification processes can be found in the literature 4-8 gasification with steam (Exxon process), gasification with oxygen or air (Koppers-Totzek and Prenflo processes), and gasification with steam/oxygen or air mixtures (Shell, Winkler and Texaco processes). 

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