Dramatic reductions of the most difficult to remove sulfur species can be efficiently achieved by using an emulsion to deliver a catalyst system that changes the chemical composition of the particular sulfur with the use of an oxygen source. APT has discovered that its leading edge emulsion technology can create the necessary environment to make an emulsion intermediary stable enough to survive the chemical reaction environment of the desulfurization yet capable of the desired emulsion separation. Stringent environmental regulations are demanding dramatic reductions in sulfur levels in diesel fuels to less than 15 parts per million (PPM) from several hundred PPM.
The oxidative desulfurization process being developed by APT is accomplished by combining the fuel with a catalyst and an aqueous hydrogen peroxide solution. The resulting mixture (an emulsion) allows the reaction to proceed without a co-solvent. The catalyst serves the dual purpose of acting both as an emulsifier and a chemical activator. An indication of the unusually high effectiveness of this approach is the observation that dibenzothiophene and related sulfur-bearing organic sulfides, which are the most refractory organic sulfur compounds in fossil fuels, are readily converted to sulfones under relatively modest conditions of temperature and pressure.
To date, our laboratory procedures have resulted in over 99% reductions with just under 2 times the theoretical amount of hydrogen peroxide relative to sulfur. Our current work is focused on optimizing the four processes below and developing engineering design criteria.
The Technical Process of Desulphurization
The chemical and physical processes involved in the desulphurization technology are:
- Preparation of the catalyst
- Determine kinetics of the desulphurization process
- Develop a process for catalysts recovery, removal of the aqueous phase, removal of the oxidized sulfur compounds
- Recovery of oxidized sulfur compounds
APT is currently in discussions with an engineering partner with refinery expertise that can help it evaluate the overall commercial feasibility of such a technology for a refiners use.