Process for the production of low molecular weight polyhydroxyl compounds

Abstract

The instant invention is directed to a process for the production of low molecular weight polyhydric alcohols by hydrogenating formose solutions in the presence of metal catalysts comprising (a) introducing an at least 20% solution of formose, of which the pH-value was adjusted before hydrogenation to a value of from 7.5 to 12.5, in batches into a first reactor in a manner such that the content of reducible groups, determined as carbonyl groups, in the reactor does not exceed a level of 2% by weight; (b) hydrogenating the solution in batches in the presence of a total quantity of a first catalyst of from 10.sup.-4 to 5.10.sup.-2 % by weight, based on the total quantity of starting product to be reduced, the amount of said first catalyst remaining constant in the reactor, said first catalyst being selected from the group consisting of metals having atomic numbers of from 23 to 29 and mixtures thereof, said metals, being in elemental and/or oxidic form; (c) withdrawing the reaction product in batches from the first reactor after the content of reducible groups, determined as carbonyl groups, has fallen to below 1.5% by weight; (d) adjusting the pH-value of the reaction product to between 3 and 7; (e) introducing said reaction product in batches into a second reactor; (f) hydrogenating said reaction product in batches in the presence of a total quantity of a second catalyst of from 10.sup.-5 to 10.sup.-1 % by weight of active metal, based on the total quantity of starting product to be reduced, the amount of said second catalyst remaining constant in the second reactor, said second catalyst being selected from the group consisting of metals having atomic numbers of 44, 45, 75 and 77, compounds thereof, and mixtures thereof; and (g) after a residence time of from 5 minutes to 4 hours withdrawing the reaction product of the second hydrogenation stage in batches from the second reactor.

Dependencies are inferred from the claim text.