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Since metal sulfides are still used as hydrogenation desulfurization catalysts, the loss of active components during operation can lead to air pollution (i.e., the generation of SOx during startup and regeneration), and the operating conditions are quite harsh, with high hydrogen consumption and large investment requirements. As a result, research and development on catalytic-free hydrogenation desulfurization technologies are receiving increasing attention. Currently, the main new technologies for diesel desulfurization include the following. (1) New technology for desulfurization using hydrogen peroxide – A new technology for desulfurizing diesel using hydrogen peroxide was successfully developed by the Japan Petroleum Energy Center and Kinki University. This new diesel desulfurization technology developed by the Japan Petroleum Energy Center can reduce the sulfur content in diesel from 500–600 ppm to 1 ppm. This technology requires mild process conditions and simple equipment, whereas conventional deep hydrogenation desulfurization needs to be carried out at 300–400°C and a pressure of 5–6 Mpa. The desulfurization test using the new technology was carried out in a 300 mL continuous reactor. A 30% hydrogen peroxide solution was added to the sulfur-containing oil, and at a temperature of about 50°C and a pressure of 0.1 MPa, the sulfur in the oil was converted into polyalkyl dibenzothiophene dioxide along with an equal amount of oxidized organic sulfides after approximately 1 hour. After washing with a sodium hydroxide solution, the sulfur compounds are adsorbed and removed by silicon or aluminum gel. Compared with existing diesel desulfurization technologies, this method does not use expensive nickel-molybdenum alloy catalysts, has lower energy consumption, and the recovered sulfur can be used as a raw material for products such as pharmaceuticals and tires ； (2) Diesel desulfurization process using ultrasonic technology – The American company Sulphco has developed a fuel desulfurization process driven by ultrasonic waves. The company has tested various feedstocks on a 3.875 L/min medium-scale unit to produce diesel containing 10–15 ppm of sulfur. The feed is mixed with a relatively small amount of an aqueous solution that contains proprietary oxidants and catalysts. The mixture is treated with ultrasound to cause rapid formation and rupture of 200μm bubbles. This results in intense mixing, raising the local temperature to several thousand degrees and the pressure to 1000 MPa. Ultrasonic waves also generate free radicals and excited oxygen atoms, which can oxidize sulfur to produce sulfones and sulfates, which are then removed using a solvent. Depending on the solvent used, sulfur can be recovered as sulfone or converted into elemental sulfur or other compounds. Based on preliminary estimates, the investment for a 1,500 t/year diesel desulfurization unit is less than half that of a comparable hydroprocessing unit, and the operating costs are also lower ； (3) Desulfurization by complexation reaction of sulfides in fuel oil with carboxylates of cobalt or copper: At temperatures of 100–150°C, the sulfides in sulfur-containing oils can be oxidized by air, with the catalysis of transition metal compounds, to form sulfate compounds that are soluble in the aqueous phase; thereafter, the fuel oil can be separated. Transition metal compounds are carboxylates of cobalt or copper, used in amounts of 0.35% to 1.0% of the fuel oil; they are produced from the residues left after the synthesis of fatty acids, alkaline solutions, and their respective chlorides. The fuel oil is brought into contact with carboxylates of cobalt or copper for 1–3 hours, while being aerated with air. This process consists of 2 parts (contact and filtration), totaling 5 stages. Tests have shown that this method reduces the sulfur content in oil to 0.07%, with a desulfurization rate as high as 84%. It is said that this method is particularly suitable for the desulfurization of diesel, enabling an improved desulfurization rate.