In industry,sulfur hexafluoride is usually prepared by the reaction of fluorine produced by electrolysis with sulfur at medium and high temperature.In addition to high-purity sulfur hexafluoride,a small amount of sulfur tetrafluoride(SF4)and other by-products are also generated.The method of direct synthesis of sulfur hexafluoride can be divided into three ways:fluorine gas and solid sulfur,and molten sulfur,and sulfur vapor reaction:fluorine gas and solid sulfur reaction,because fluorine sulfur reaction is very intense exothermic reaction,its reaction temperature is not easy to control,resulting in the increase of by-products and increase the burden of post-treatment.

　　In addition,it is difficult to continuously add solid sulfur into a sealed reactor,so this method is not suitable for industrial production.The reaction of fluorine gas and sulfur vapor is to heat sulfur to 445℃(boiling point)and above,so that sulfur becomes vapor and is sent to the reactor to react with fluorine.There is also a defect that the reaction temperature is difficult to control,and the reaction temperature can reach 600℃or above,so special reactor material must be used,and this method is not suitable for industrial production.The reaction of fluorine gas and molten sulfur is to keep the sulfur in the reactor in the molten state of 85~105℃and react with the flowing fluorine gas.The reaction temperature of this method is easier to control.

　　High purity sulfur hexafluoride at room temperature and pressure is a colorless,odorless,non-toxic,non-combustible,non-corrosive gas,gas density 61139 g/L,its chemical stability is strong,500~600℃does not decompose,and acid,alkali,salt,ammonia,water and other non-reaction,under the arc(several thousand degrees)decomposition into S and F atomic gas,However,once the arc is removed,SF6 will be compounded within 0-5~10-6 s.

　　d We all know that sulfur hexafluoride has good electrical insulation performance and excellent arc extinguishing performance,its electric resistance is 215 times of nitrogen under the same pressure,the breakdown voltage is 215 times of air,arc extinguishing ability is 100 times of air,high purity sulfur hexafluoride is a new generation of ultra-high insulation medium material superior to air and oil.

　　Sulfur hexafluoride recovery and purification chemical properties are stable.Slightly soluble in water,alcohol and ether,soluble in potassium hydroxide.No chemical reaction with sodium hydroxide,liquid ammonia,hydrochloric acid and water.It does not react with copper,silver,iron and aluminum in dry environment below 300℃.Quartz has no effect below 500℃.It reacts with sodium metal at 250℃and in liquid ammonia at-64℃.Mix it with hydrogen sulfide and heat it up.At 200℃,in the presence of specific metals such as steel and silicon steel,can promote its slow decomposition.