Hi Pallavikhatri.
About your concerns with hydrogen. I agree Bobby´s advice. And also hydrogen in the hydrodesulfurization it is part of reactions.
For a better understanding, I copy the following paragraph from "Petroleum Refining - Technology and economics" 4th ed from J Gary, G Handwerk (marcel dekker, 2001). Chapter 9 Hydrotreating.
"Hydrotreating is a process to catalytically stabilize petroleum products and/ or remove objectionable elements from products or feedstocks by reacting them with hydrogen. Stabilization usually involves converting unsaturated hydrocarbons such as olefins and gum-forming unstable diolefins to paraffins. Objectionable elements removed by hydrotreating include sulfur, nitrogen, oxygen, halides, and trace metals. Hydrotreating is applied to a wide range of feedstocks, from naphtha to reduced crude. When the process is employed specifically for sulfur removal it is usually called hydrodesulfurization, or HDS. To meet environmental objectives it also may be necessary to hydrogenate aromatic rings to reduce aromatic content by converting aromatics to paraffins."
I Hope this little bit of knowledge will be useful.
Good luck
Fausto.
Edited by Profe, 03 March 2016 - 03:05 PM.