CHEMOCATALYTIC CONVERSION OF LIGNINOCELLULOSE RAW MATERIALSINTO LACTIC ACID

The article presents the results of research on the hydrolysis of cellulose under the action of hot water in the presence of the catalyst lead (II) nitrate. It was found that lead (II) nitrate not only catalyzes the conversion of ground cellulose, but also glucose and fructose into lactic acid with a high yield (~70%). The transformation of glucose into lactic acid can be conventionally divided into the following three stages: isomerization of glucose into fructose, retro-aldol fragmentation of fructose with the formation of two C3 intermediates or triose, and isomerization of these trioses into lactic acid. The presence of Pb(II) significantly lowers the activation barrier for retro-aldol cleavage of fructose, changing the main reaction pathway from the formation of hydroxymethylfurfurol to the formation of lactic acid. Calculations show that the coordination of Pb(II) with the oxygen atoms of fructose increases the positive charges on the H atom of C4-OH. This indicates that Pb(II) increases the acidity of C4-OH, thereby facilitating proton transfer and C-C bond cleavage in the retro-aldol reaction.