Butane isomerization liquid-phase processes

Fig. 20. Process variables for butane isomerization. Shell liquid-phase process. Conditions (unless otherwise noted) temperature, 176°F. residence time, 13-15 minutes AlCU, 7.5 wt.% HCl, 4.0 wt.% catalyst-to-hydrocarbon ratio, 1/1.

Butane Isomerization. Five processes for butane isomerization were in commercial use by the end of World War II. These processes differ primarily in the method of contacting the hydrocarbon with the catalyst. Two are vapor-phase processes, which require periodic discard and replacement of the catalyst bed the other three are carried out in the liquid phase and are continuous with respect to catalyst addition and withdrawal. 

The butane isomerization process developed by the Universal Oil Products Co. is shown in Figure 4. In this process (3), the feed is maintained essentially in the liquid phase under pressure. Part of the feed is by-passed through a saturator, where it dissolves aluminum chloride. The feed later picks up hydrogen chloride and passes through the reactor, which is packed with quartz chips. Some insoluble liquid complex is formed, and this adheres to the quartz chips. The aluminum chloride in the feed is preferentially taken up by the complex, which thus maintains an active catalyst bed. The complex slowly drains through the reactor, losing activity en route. It arrives at the bottom in essentially spent condition and is discarded. Aluminum chloride carried overhead in the reactor products is returned to the reactor from the bottom of the recovery tower. The rest of the process is the same as in the vapor-phase processes. 

The third liquid-phase butane-isomerization process, shown in Figure 5, was developed by Shell as an improvement over the original intermittent vapor-phase process. 

Fig. 17. Liquid-phase butane isomerization. Standard (Indiana)-Texas process.

The third liquid-phase butane-isomerization process was developed by Shell Oil Company (16) as an improvement over the original intermittent vapor-phase process. The simplified flow diagram is shown in Figure 18. The aluminum chloride is handled, in this case, as an approximately 9% solution in relatively inert molten antimony trichloride the... 

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