There are mainly 5 steps to deal it: 1.Pretreat–remove the water, impurities etc 2.Distillation–Get part of light oil directly, most of the rest come to the third step–catalyic 3.Catalytic–reaction with the catalyst to get more diesel oil 4.Cooling–gas type to liquid type 5.Refine–decolor the diesel with silica gel, and remove the rest residues to make the diesel oil more clear