Abstract: Monosaccharides, such as glucose-water solution, are catalytically hydrogenated by being passed through multiple reaction zones connected in series and each containing a high-activity supported nickel catalyst to produce 99.8 W % overall conversion to an alditol solution such as sorbitol. The pH of liquid in each reaction zone is controlled to between 4.5 and 7 by adding an alkali solution such as sodium hydroxide to the feed to prevent acid leaching of catalyst metal and to help maintain catalyst activity therein. Reaction zone conditions used are 130.degree.-180.degree. C. temperature, 500-2000 psig hydrogen partial pressure, and a ratio of hydrogen gas/feed liquid within the range of about 500-5000. Feedstream liquid space velocity is maintained within range of 0.5-16 V.sub.f /Hr/V.sub.c, with higher space velocities being used for achieving lower incremental conversion desired in the subsequent reaction zones to help maintain pH of the effluent liquid within the desired range.