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Propylene has typically been produced as a byproduct either from the steam cracking of naphtha to produce ethylene or from the fluid catalytic cracking to produce gasoline. With the shale gas boom and the excess of NGLs such as ethane, the production of ethylene has switched the feedstock from naphtha to ethane. This action has eliminated the production of propylene as a byproduct, opening an opportunity for the development of on‐purpose propylene production processes. The alternatives to produce propylene from shale gas include two options via methanol and one using the propane obtained from the purification of shale gas [32,33]. The processes to produce propylene via methanol are the MTO route and the methanol to propylene (MTP) process [33]. The MTO process is described earlier in the ethylene section. MTP follows a similar path. First, natural gas is transformed into syngas gas using a reforming alternative, and then the syngas is transformed into methanol. As opposed to the MTO process, where crude methanol is sent to the MTO reactor, methanol has to be purified for its use as feedstock for the MTP process. Therefore, the crude methanol obtained from the methanol synthesis reactor is sent to a flash unit and purified using a distillation column. The purified methanol is then fed to a reactor, where it is converted to dimethyl ether and water. Then, the outlet stream of the reactor is sent to a fixed bed catalytic reactor to produce propylene. The effluent from the fixed bed reactor contains propylene, gasoline, and LPG, as well as water. It is sent to a flash unit to remove water and the remaining stream is purified using distillation columns.

Another alternative for the production of on‐purpose propylene is the propane dehydrogenation process, in which a depropanizer column is used to separate C⁴⁺ compounds that may be present in the fresh material. The purified propane enters a cold box to refrigerate the effluent from the propylene production reactor. Then, the propane stream is mixed with hydrogen and sent to a fired‐heater before being fed to a fluidized catalyst bed reactor. The reaction is highly endothermic. The outlet stream of the reactor contains propylene, propane, light gases, ethane and ethylene, and some heavier hydrocarbons. The reactor effluent is cooled, compressed, and sent to a cool box where hydrogen is separated from the hydrocarbons. The liquid stream from the cold box is sent to a selective hydrogenation process (SHP) to further improve the production of propylene. The effluent from the SHP is fed to a deethanizer column to remove light gases. Finally, the remaining stream is fed to a C₃‐splitter column to produce the propylene. The propane obtained at the bottom of the splitter column is recycled to the depropanizer column [32].

These processes represent an excellent opportunity for the independent production of propylene instead of obtaining it as a byproduct of other processes.