GB721260A - Improvements in or relating to a process for hydrogenating reducible sugars - Google Patents

Abstract

In a process for continuously hydrogenating a reducible sugar to a polyhydric alcohol by continuously feeding into the lower end of a vertical reactor a suspension of finely-divided hydrogenation catalyst in a solution of the sugar, maintaining the reactor at hydrogenating temperature, continuously feeding hydrogen under pressure into the lower end of the reactor, maintaining a selected pressure in the reactor, and continuously removing the reaction mixture from the upper end of the reactor, the rate of hydrogen feed is at least equal to the critical hydrogen rate, expressed in terms of linear feet of hydrogen flow per hour in the reactor at reactor temperature and pressure, required by the equation critical hydrogen rate = 76.5 + 0.13H where H is the rate of hydrogen usage in cubic feet per hour per square foot of reactor cross-sectional area, hydrogen volume being expressed in terms of one atmosphere pressure and 0 DEG C. Hydrogenation may be effected in a series of reactors and conditions are so arranged that hydrogenation to the maximum extent possible is achieved in the first reactor. The "critical hydrogen rate" is the lowest rate of hydrogen feed which will give the greatest extent of hydrogenation possible under the existing conditions. The rate adopted should be somewhat higher than the critical rate to ensure maximum hydrogenation. In examples: (1) and (2) sorbitol is obtained from glucose; (3) sorbitol and mannitol from inverted sucrose; and (4) lactositol from lactose by hydrogenation in the presence of a supported reduced nickel catalyst at temperatures of about 150-165 DEG C. and pressures of 1000-2000 p.s.i.g., an equation being given for the calculation of the rate of hydrogen usage.