Non-conventional technologies for fuel desulphurization

Refinery distillates, especially gas oil fractions contain considerable amounts of alkylated benzo-thiophene components which are most recalcitrant to desulphurization via classical hydrodesulfurisation. Fuel regulations continue to tighten worldwide in response to the need for cleaner air and refiners meet these regulations at a very significant cost. In fact, most refiners will need a major revamp of existing HDS medium pressure units or even install new grass root units. The need to cut the operational and capital costs has necessitated a renewed look into non-hydrogen consuming, low temperature and pressure processes for producing ultra low sulphur fuels. Non-conventional approaches for ultra low sulphur fuels (ULSF) belong either to oxidative or to selective adsorption routes. In oxidative routes, biodesulfurization (BDS) involving specialized bacteria and oxidation catalysed by chemical oxidants have been thoroughly investigated. BDS by genetically engineered strains has capability to produce ULSD having 20 volumes of fuel before needing regeneration to restore their activity. Small SARS systems are especially attractive at gas stations for fuel cell vehicles. This presentation will review the recent advancements in oxidative and adsorption technologies for fuel desulfurization. Some results obtained in the author's labs for process improvement in biodesulfurization of diesel fractions will also be discussed.