DISPROPORTIONATION OF PROPYLENE (Metathesis) 

Olefins could be catalytically converted into shorter and longer-chain olefins through a catalytic disproportionation reaction. For example, propylene could be disproportionated over different catalysts, yielding ethylene and butylenes. Approximate reaction conditions are 400°C and 8 atmospheres:

Table 1.1 indicates the wide variety of catalysts that can effect this type of disproportionation reaction, and Figure 1.1 is a flow diagram for the Phillips Co. triolefin process for the metathesis of propylene to produce 2-butene and ethylene.

Figure 1.1. The Phillips Petroleum Co. process for producing  -butene and ethylene from propylene: (1) metathesis reactor, (2) fractionator (to separate propylene recycle from propane), (3, 4) fractionator for separating ethylene, butylenes, and C₅⁺.

Anderson and Brown have discussed in depth this type of reaction and its general utilization. The utility with respect to propylene is to convert excess propylene to olefins of greater economic value.

Table 1.1:Representative disproportionation catalysts