The invention discloses a method for preparing
lactic acid by using an alkaline-earth
metal modified Sn-beta catalyst. The method comprises the following steps: carrying out
ion exchange reaction on an Sn-beta catalyst and an alkaline-earth
metal solution to prepare the alkaline-earth
metal modified catalyst; and mixing the catalyst, a saccharide substrate and a
solvent, adding
lactic acid, and carrying out
lactic acid preparation reaction. In the catalytic reaction process,
hydrolysis of
levoglucosan and the
polysaccharide substrate can be promoted by externally adding lactic acid, Sn is taken as an L acid
active site in the reaction,
alkaline earth metal ions and adjacent skeleton
oxygen are taken as Lewis acid-
base pair active sites, and generation of a trans-
aldol reaction can be promoted through the synergistic effect of Sn, the
alkaline earth metal ions and the adjacent skeleton
oxygen, so that the selectivity of lactic acid is improved. Compared with other methods, the method provided by the invention has the advantages of simple catalyst preparation, short reaction time, good
catalytic effect, easy industrialization and the like. The substrate used in the
catalytic method is suitable for
biomass thermal
cracking product
levoglucosan which can be obtained on a large scale, and has a good effect on high-molecular polysaccharides such as
cellulose and
inulin.