Review on Recent Patents in Sulfur Removal from Liquid Fuels by Oxidative Desulfurization (ODS) Process

Oxidative desulfurization (ODS) process, a non-hydrogen consuming method to remove sulfur from liquid fuels, has received a lot of attention recently for desulfurization of some liquid fuel feedstocks. This paper reviewed the recent patents in the ODS process. Generally Hydrogen peroxide (H2O2) is used as an oxidant in organic acids (e.g., acetic acid or formic acid) medium for the ODS process. Compared with the traditional hydrodesulfurization (HDS) process, ODS process has two main advantages: 1) the ODS process can be carried out in liquid phase under very mild operating conditions, thus much less capital intensive; 2) this process shows high reactivity and selectivity for some sulfide compounds which are hard to be removed by the HDS process, e.g. dibenzothiophene (DBT) and its derivatives. After the oxidation, the sulfur compounds are oxidized to their corresponding sulfoxides and subsequently sulfones. Afterward, these highly polarized products can be removed by solvent extraction or sorbent adsorption. Other oxidants, such as t-Butyl hydroperoxide, air, and solid catalyst were also reviewed. Ultrasound greatly facilitates the ODS process. The ODS process is quite useful for small and medium refineries, and also a good fit as a finishing process for downstream of an existing HDS unit producing 300-500 ppm sulfur.