▎ 摘　　要

NOVELTY - Preparing lactulose, comprises (i) preparing lactose solution, (ii) adding boric acid to lactose solution, subjecting reaction solution to lactose isomerization, (iii) adding acid to isomerized reaction solution, (iv) adding mannitol in solution, mannitol and boron generate complexes, (v) adding graphene oxide uniformly dispersed in deionized water to material passing through (iv), stirring, hydroxy groups on surface of graphene oxide flakes form hydrogen bonds with mannitol boron complexes and tetrahydroxy boron ions, sheet-shaped graphene oxide bonds to capture mannitol-boron complexes and tetrahydroxyboron ions, contacting and agglomerate with flaky graphene oxide, filtering and separating graphene oxide agglomerate that captures boron, (vi) desalting and removing non-isomerized lactose from material from which graphene oxide-boron is removed, passing material through ion exchange resin to remove salt and through boron selective adsorption resin to remove boron. USE - The method is useful for preparing lactulose. ADVANTAGE - The method: utilizes the selective complexation of boric acid to prepare isomerized lactose, and recovers boric acid, reduces the separation cost of boron. DETAILED DESCRIPTION - Preparing lactulose, comprises (i) preparing 30-50g/100ml lactose solution, (ii) adding boric acid to lactose solution, consumption of boric acid is (4-5g)/100ml, subjecting reaction solution to lactose isomerization, process condition of isomerization is as follows pH value of lactose solution is 9-11, reacting at 70-90°C for 100-140 minutes, (iii) adding acid to isomerized reaction solution to adjust pH value of solution to 2.2-2.8, to remove complexation of tetrahydroxy boron ions and lactulose, (iv) adding mannitol in solution, mannitol and boron generate complexes, (v) adding graphene oxide uniformly dispersed in deionized water to material passing through (iv), stirring, hydroxy groups on surface of graphene oxide flakes form hydrogen bonds with mannitol boron complexes and tetrahydroxy boron ions, sheet-shaped graphene oxide bonds to capture mannitol-boron complexes and tetrahydroxyboron ions, contacting and agglomerate with flaky graphene oxide that is connected with surrounding mannitol-boron complex and tetrahydroxy boron ion, filtering and separating graphene oxide agglomerate that captures boron, (vi) desalting and removing non-isomerized lactose from material from which graphene oxide-boron is removed, to obtain target lactulose, passing material passing through an ion exchange resin to remove salt and through boron selective adsorption resin to remove boron.