TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The step of pre-treating coarse animal and vegetable oils comprises adding 75-85% phosphoric acid (0.01-6 mass%) to coarse animal and vegetable oils in a reaction kettle and stirring at 50-80 degrees C; adding 30-45% phosphoric acid (20-50 mass%) to the coarse oil mixture and stirring at 60 degrees C to react the phosphoric acid and peptization impurities contained in the coarse oils and to separate the impurities; adding 1-10% water to hydrate, flocculate and collect the impurities from oil; performing thermal precipitation, centrifugation and filtering steps to remove the impurities and to obtain purified raw oil. The peptization impurities include organic phospholipids, protein, diglyceride, or refined foods. The pre-treatment step is carried out at cylindrical jacketed reaction kettle equipped with stirrer, three feeding openings on upper part, discharging opening for clarified liquid at lower part, thermometer sleeve and manhole, reducer frame, pin gear reducer, stirring motor, exhaust port, and liquid extraction port which is connected to deposition tank. The step of esterification and interesterification comprises feeding pre-treated oils (100 pts.wt.), 10-30% dried methanol (21 pts.wt.), and 1-5% alkaline catalyst (1.5 pts.wt.) into stirring reaction kettle; slowly heating while stirring until refluxing temperature is reached, refluxing for 1-3 hours to implement the esterification and interesterification reaction; after removing the methanol, adding 1-5% active attapulgite in the presence of carbon dioxide, stirring and refining at 80-90 degrees C for 1 hour; simultaneously, neutralizing used alkaline catalyst by carbon dioxide; depositing and separating reaction products comprising lower layer containing yellow glycerin layer, upper layer containing biodiesel which is showed in yellow or deep yellow, and bottom layer containing attapulgite of dust-color; and clarifying the biodiesel of upper layer by separation and centrifugation to obtain transparent biodiesel. The esterification and interesterification steps are carried out at cylindrical jacketed reaction kettle equipped with condenser and refluxing dealcoholizing machine at upper part, feeding insulation tank at one side, reducer frame, pin gear reducer and stirring motor at center portion, and back taper of 45-60 degrees C at bottom part to conveniently discharge solid dregs. The step for reclaiming and purifying glycerin comprises decompressing, distilling and dehydrating by pumping coarse glycerin into decompressing distillation kettle at 250 degrees C and 700 mm Hg.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The strong electrolyte can be hydrates or acids of nitrogen, phosphorus, arsenic or antimony; oxide of bismuth, or preferably hydrate of phosphorus oxide. The catalyst used in the esterification and interesterification reaction is hydroxide of alkali metal or alkaline earth metal, lower alcohol of alkali metal, or aluminum-magnesium composite type solid hydroxide of alkali metal prepared from hydrotalcite or oxide.