2 – Treatment


The second stage in the petroleum process is treating various hydrocarbon streams (naptha, kerosene, distillate, gas oil, etc.) to remove contaminants such as organic compounds (containing sulfur, nitrogen, and oxygen), dissolved metals and inorganic salts, and soluble salts that are dissolved in the water. However, treatment is mainly focused on removing unwanted sulfur compounds.

Petroleum Refining Process Map


Petroleum Products

Common Treatments

Three processes are commonly used to treat hydrocarbon streams: desalting, catalytic hydrotreating, and sweetening. Desalting is a process whereby crude oil is “washed” in an effort to remove initial dissolved inorganic metals and salts. The salts can cause severe corrosion problems in downstream processing equipment. Catalytic hydrotreating is a process that uses reactors to remove organic compounds that contain sulfur, nitrogen, and oxygen in order to meet environmental regulations. These elements can also be detrimental to downstream process equipment. Finally, sweetening uses absorbers to remove “sour” sulfur compounds such as hydrogen sulfide and elemental sulfur.

Catalytic Hydrotreating Reactor
Catalytic Hydrotreating Reactor
Sweetening Absorber
Sweetening Absorber

After treatment via the processes above, the hydrocarbon streams are ready for the final step of the petroleum refining process, conversion.



  • Catalano, Salvatore, Marathon Oil Corporation, Industry Consultant, personal communication, 2015
  • “Hydrotreating.” Shell Global. Web. 13 June 2017. < http://www.shell.com/business-customers/global-solutions/refinery-technology-licensing/hydrotreating.html >.
  • “Petroleum Refining Process.” OSHA Technical Manual. Section IV: Chapter 2. United States Department of Labor, Occupational Safety & Health Administration, n.d. Web. 24 February 2016.
  • Woodcock, Kermit E., and Myron Gottlieb. “Gas, Natural.” Kirk-Othmer Encyclopedia of Chemical Technology. 2004. Print.


  • Matthew Posh