Polypropylene, acrylonitrile, propylene oxide, 2-propanol, cumene/phenol, oxo-alcohols, isopropanol, acrylic acids, and so many other derivatives are all obtained from propylene; a main building block in petrochemicals industry.
The increasing propylene-derivatives demand in the last few years has largely absorbed conventional available supplies of propylene as that from steam cracking of naphtha, and FCC off gas. On-purpose propane dehydrogenation is becoming a more economic favorable way to produce large amounts of propylene. Serious search for other routes for propylene production as metathesis and methanol to olefins is being carried out by different R and D hubs all over the world. At the mean time, the emerging gas discoveries in the United States and other parts of the world promotes propane dehydrogenation route over the other alternatives to provide the growing market need for this essential chemical.
A number of proven propane dehydrogenation technologies are available in market including Oleflex™ by UOP, STAR® by Uhde and Catofin® by Lummus. UOP is dominating the market by more than 10 plants in operation and the number is expected to significantly increase in the near future.
Let’s have a look at one of Oleflex™ plants to know how you make propylene out of propane. Fresh propane goes through driers and treaters to remove water and contamination first, and then it goes to a depropanizer column to get rid of the heavier materials “C4+” before being routed to reactor section.
Oleflex™ reactor section consists of a number of reactors in series with interstage fired heaters in between to provide required heat of reaction. A highly selective, platinum based catalyst system is used to dehydrogenate propane. Coke as by-product is formed on catalyst which suppresses catalyst activity and selectivity. To overcome this problem, UOP applies its intelligent technology of CCR “Continous Catalyst Regeneration” through which coke is removed from catalyst by high temperature oxidation, thereby, restoring catalyst activity and selectivity. The regenerated catalyst is then circulated back to the reaction section allowing smooth and stable operation.
Propane dehydrogenation is an equilibrium-limited reaction and the maximum conversion per pass is set by reactor effluent temperature. Unreacted propane is separated from propylene by distillation where polymer grade propylene is collected and sent for storage or to the downstream processing unit while propane is circulated back to the reactor section.
Due to high temperature of reaction (above 600 C), thermal cracking takes place and a small amount of C1 and C2’s are formed in addition to traces of diolefins. Cryogenic refrigeration is applied to separate the light ends from the propane/propylene stream and a selective hydrogenation is performed downstream the reactor section to hydrogenate diolefins back to mono-olefins.
By 2020 it is expected that about 20% of the propylene supply will be produced from on-purpose propane technologies and UOP Oleflex™ will be a key player in this field. Whenever you see a carpet, bottle, toy or bag made of a propylene-derivative remember this name “O-l-e-f-l-e-x”
About the author
This brilliant article was contributed by Malek Ibrahim. He is UOP Field Technical Advisor. He has bachelor degree in chemical engineering from Cairo University. He worked as a development engineer in UOP R&D department where he was focused on paraffin dehydrogenation process and catalysis development. Right now he is a field advisor working on performing startup and commissioning of UOP technologies all over the world. He can be contacted at his email: MalekFayed@Gmail.com
UOP LLC: headquartered in Des Plaines, Illinois, USA, is a leading international supplier and licensor of process technology, catalysts, adsorbents, process plants, and consulting services to the petroleum refining, petrochemical, and gas processing industries. UOP is a wholly-owned subsidiary of Honeywell International, Inc. and is part of Honeywell’s Performance Materials and Technologies strategic business group. For more information, go to www.uop.com.
I’m Zaki. I used to be a project, process and chemical engineer. I'm now employed as a chemical engineering lecturer, but now I'm on my Ph.D study leave. Hope you like reading my blog. I welcome any feedback from you. TQ!
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