Bi-lawsone preparation method

The invention discloses a bi-lawsone preparation method which is characterized in that 2-hydroxy-1,4 naphthoquinone is mixed with trioxymethylene in organic solvents, synthetic reaction of bi-lawsone is performed under the catalytic action of concentrated sulfuric acid at the temperature of 0-80 DEG C, stirring reaction is performed for 6-8 hours, the molar volume ratio of the 2-hydroxy-1,4 naphthoquinone, the trioxymethylene, the organic solvents to the sulfuric acid is 1mmol:(0.4mmol-1.2mmol):(5-25mL):(0.20-5)mL, and the organic solvents include cyclohexane, dichloromethane, glacial acetic acid or ethyl alcohol, and the mass concentration of the sulfuric acid is 98%. Compared with the prior art, the bi-lawsone preparation method has the advantages that process is simple, yield is high, production cost is low, reaction conditions are milder, environmental pollution caused by release of toxic formaldehyde gas to environments in the synthesis process is effectively avoided, and the bi-lawsone preparation metho