Propane, Propylene, and Their Separation

Propane is a colorless, easily liquefied, gaseous hydrocarbon, the third member of the paraffin series following methane and ethane. The chemical formula for propane is CH3CH2CPI3. It is separated in large quantities from natural gas, 

As with ethane and other paraffin hydrocarbons, propane is an important raw material for the ethylene petrochemical industry. The decomposition of propane in hot tubes to form ethylene also yields another important product, propylene. The oxidation of propane to compounds such as acetaldehyde is also of commercial interest. 

In general, a C3 stream is obtained that contains propane, propylene, pro-padiene, and propyne, and these are separated in a C3 distillation column, also referred to as the C3 splitter. Propane-propylene separation and, as a rule, olefin-paraffin separation, are energy-intensive, and some estimates are that 1.27 x 1017 J are used for olefin-paraffin separation on an annual basis [4] while roughly 3% is used by paraffin-olefin distillation columns [5]. This provides an incentive to examine the propane-propene separation, which is an example of paraffin-olefin separation. 

Propane and propylene have similar atmospheric boiling points (propane -42.1°C, propylene -47.70°C) and, as a result, the separation of these compounds requires highly complicated units. Distillation is by far the most commonly used separation process in the chemical industry today. The variants in use are  

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