Preparation method of anhydrous formic acid

The invention relates to a preparation method of anhydrous formic acid, and belongs to the technical field of chemical engineering. The method comprises the following steps: introducing water-containing formic acid into a formate medium with the mass percent concentration of 50-95%, and enabling the molar ratio of formic acid to formate in the solution to be 0.1-4.5, so as to obtain a solution 1; evaporating and concentrating the solution 1 at 80-120 DEG C to remove moisture in the solution 1, so that the value of formic acid mass/(formic acid mass + water mass) in the solution 1 is greater than or equal to 85% to obtain a solution 2; and continuously evaporating the solution 2 at a temperature of 200-300 DEG C, condensing, and taking fractions at different temperatures to respectively obtain 85-99.9 wt% of formic acid products. According to the invention, formic acid and water with similar boiling points are prevented from being distilled, and the production and rectification difficulty of anhydrous formic a