Standard Oil process

Two catalyst systems were developed by Standard Oil and Philips petroleum. Standard Oil process uses metal catalyst such as molybdenum trioxide on supports like alumina or titanium or zirconium dioxide. The process is carried out at 200-300°C at Organisation and Qualities... 

Figure 9.3 Simplified flow-sheet of the Standard Oil process for the oxidation of ethane to acetic acid [21],...

The Standard Oil process has the longest history. Working with ethylene pressures around 70 bar, it represents a medium-pressure process. The polymerization is started by one of the usual commercial hydroforming catalysts partially reduced M0O3 aluminum oxide, activated by sodium or lithium aluminum hydride. The ethylene is dissolved to 5-10% in xylene and polymerized to practically a 100% yield at temperatures below 200°C but still above the melting point of poly(ethylene). This solution polymerization enables the catalyst surfaces to be kept predominantly free and active. 

The nature of polymerization with Standard Oil catalysts is not at present completely understood. Nor is it certain whether the Phillips and Standard Oil catalysts operate by the same or different mechanisms. However, the polyethylene obtained by the Standard Oil processes resembles that produced in the Phillips processes in that it, too, is almost completely linear. 

This paper also provides the chronological details of the three catalyst systems outlined in Table 3.2 in which the Standard Oil (Indiana) catalyst was the first ethylene polymerization catalyst identified [3]. However, as pointed out by Sailor and Hogan, the Standard Oil catalyst was commercialized more slowly than the other two catalyst types, and because of higher operating costs, the Standard Oil process was shut down in 1973. The other two catalyst systems listed in Table 3.2 accoxmt for most of the polyethylene manufactured today. 

At the present time the nature of polymerization with Phillips catalysts is incompletely understood. A possible mechanism is discussed briefly under Standard Oil processes. Whatever their mode of reaction may be, these catalysts lead to almost completely linear polyethylene. No ethyl or butyl... 

Although the Phillips and Standard Oil processes can be used to prepare polypropylene, the polymer yields tend to be low and it appears that these processes have not been used for commercial production of polypropylene. Until about 1980, polypropylene has been produced commercially only by the use of Ziegler-Natta catalysts. Commonly a slurry process is used and is carried out in much the same manner as described previously for the preparation of polyethylene (see section 2.3.2(b)). In the case of polypropylene, some atactic polymer is formed besides the required isotactic polymer but much of this atactic material is soluble in the diluent (commonly heptane) so that the product isolated is largely isotactic polymer. Recently, there has been a marked shift towards processes involving gas phase polymerization and liquid phase polymerization. Few details of these newer processes have been published. Gas phase processes resemble those described previously for the preparation of polyethylene (see section (2.3.2(b)) and swing plants are now feasible. In liquid phase processes polymerization is conducted in liquid propylene, typically at 2 MPa (20 atmospheres) and 55°C. Concurrently with these developments, new catalyst systems have been introduced. These materials have very high activity and the reduced levels that are required make it unnecessary to remove catalyst from the final polymer. Also, the new catalyst systems lead to polypropylene with higher proportions of isotactic polymer and removal of atactic polymer is not necessary. 

The metal oxide catalyzed polymerization of ethylene takes place under conditions of medium pressure and temperature. It is practiced according to two methods, the Phillips process and the Standard Oil process (also known as the Indiana process) the former is based on chromium oxide catalysis, whereas the latter uses molybdenum oxide. The Phillips process dominates the field of metal oxide catalysis. Chromium oxide catalysis is the most widely used method for the production of high density polyethylene, accounting for a little more than half the worldwide output. 

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