The invention relates to the technical field of
organic compound synthesis, in particular to a preparation method of
benzaldehyde, and aims to improve the product yield, reduce the production cost andreduce environmental damage. The preparation method is characterized by comprising the following steps: S1, adding
copper nitrate, water,
silver nitrate and catalyst concentrated
nitric acid into a reaction device, heating, dropwise adding
benzaldehyde, continuously heating, and carrying out heat preservation to react, so as to obtain a reaction
mixed solution; and S2, filtering the reaction
mixed solution to remove
copper hydroxide precipitates to obtain a mother solution, cooling the mother solution, and filtering to obtain a
solid m-nitrobenzaldehyde crude product with the content of o-nitrobenzaldehyde less than 0.5%; and S3, putting the m-nitrobenzaldehyde crude product into a reaction device, adding 3.0-3.5 volume times of a water-soluble
solvent of that of the m-nitrobenzaldehyde crude product, heating, filtering to remove insoluble impurities, adding water of the same volume of the water-soluble
solvent, filtering, taking out precipitated solids, and
drying to obtain the high-purity m-nitrobenzaldehyde.