2.4. Hydrogenolysis of stover sugars into polyols
The stover sugar hydrolysate was concentrated to a 300–350 g/L sugar concentration by steam evaporation before hydrogenolysis. Then the concentrated stover sugar hydrolysate was sent to the hydrogenolysis reactor supplemented with 4% (w/w) sodium hydroxide and 15% modified Raney nickel catalyst #12-2 (w/w, based on the total sugar weight in system). The purified hydrogen was ventilated into the reactor to remove the inert air in the reactor and heated to 230 °C and 11.0 MPa slowly in an oil bath, then maintained for 120 min until glucose and xylose were completely converted. After each batch reaction, the Raney nickel catalyst was recycled by washing with deionized water then sent to the next round of catalytic operation.