Method for preparing petroleum sulfonate

The invention relates to a method for preparing petroleum sulfonate. The invention is characterized that: a distillation range of petroleum distillate oil from 340 DEG C to 520 DEG C is employed, colloid plus asphalt is less than or equal to 10%, the weight percentage of aromatic hydrocarbons is from 5 to 35% acid value is less than or equal to 5 mg KOH/g, sulfonated raw material is obtained through a hydrotreatment process; the components of catalyst comprises: 3 to 30% of nickel oxide and/or 0.1 to 20% of molybdena and/or 0.1 to 8% of cobalt oxide and/or 0.1 to 10 % of tungsten oxide and/or5 to 25% of silicon oxide and alumina carrier as the rest. the sulfonated raw material obtained through a hydrotreatment process is sulfonated, gaseous state sulphur trioxide is employed as a sulfonating agent, volume concentration is 5%, the weight ratio of the sulfur trioxide to raw material oil is equal to 10 : 100, the sulfonation temperature is 45 DEG C, a sodium hydroxide aqueous solution with 20% of volume concentr