TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Methods: The method involves co-precipitation reaction. The co-precipitation reaction comprises blending salt solution and aqueous alkali while stirring at greater than 80 rpm, and crystallizing the mixture at greater than 40 degrees C for greater than 0.5 hour to generate precipitation. The blending of salt solution and aqueous alkali comprises adding salt solution into aqueous alkali, aqueous alkali into salt solution, or synchronously dripping salt solution and aqueous alkali; and separating, washing, and drying precipitate to obtain hydrotalcite-like compound. The adding method comprises dripping or pouring salt solution or aqueous alkali at 5-30 ml/minute. The separating comprises precipitation using centrifugal or filter funnel. The washing comprises washing the filtrate using water. The method involves adding natural oil and short-chain alcohol at mass ratio of 20:1-3:1 into reacting container, adding hydrotalcite-like catalyst containing oil (1-5 pts. wt.), stirring the mixture at greater than 60 degrees C for 0.5 hour, removing catalyst after reaction, allowing the product to stand and lay, and analyzing and calculating the yield of product via color-quality method. Preferred Components: The divalent and trivalent metal salts are nitrate, sulfate or hydrochloride. The concentration of divalent metal ion is 0.1-4.0 mol/L. The concentration of trivalent metal ion is 0.05-2.0 mol/L. The mole ratio of divalent metal ion and trivalent metal ion is 1.6:1-10:1. The aqueous alkali is sodium hydroxide, sodium carbonate, ammonia, ammonium carbonate, potassium hydroxide, potassium carbonate, carbamide, and/or calcium hydroxide. The aqueous alkali is dissolved in water. The concentration of hydroxide ion is 0.2-4.0 mol/L. The concentration of carbonate ion is 0.1-4.0 mol/L. The mol ratio of hydroxide ion to mixture of divalent and trivalent metal ion is 0.6-3.5. The mole ratio of divalent and trivalent metal ions is 1.6:1-10:1. The upper layer is biodiesel. The volume ratio of aqueous alkali to salt solution is 1:1. The lower layer is glycerin. Preferred Parameter: The drying is carried out at 70-100 degrees C.