Preparation method of L-fructose

The invention discloses a preparation method of L-fructose. The preparation method comprises the following steps: S1, preparing a solid base catalyst KF/Fe-O-GN; s2, preparing a graphene/carbon nanotube/styrene sulfonated resin filler; s3, in the presence of a solid base catalyst KF/Fe-O-GN, preparing the L-fructose; s4, converting the resin filler prepared in the step S2 into a calcium type, adding the calcium type resin filler into a separation column, enabling the filtrate obtained in the step S3 to pass through the separation column, and collecting the separation liquid of the L-fructose section.The KF/Fe-O-GN solid alkali is added in the process of producing the L-fructose through the aldehyde-ketone reaction, the catalytic rate is increased to 96.4%, and the yield of the L-fructose is increased to 96.4%. Compared with the existing liquid base catalyst, solid base catalyst and the like, the catalytic rate is improved by 20-30%; the product is separated and purified through graphene/carbon nanotube/styren