Process for the preparation of low molecular polyhydroxyl compounds

A process for the preparation of low molecular weight polyhydric alcohols by the hydrogenation of formose solutions in the presence of metal catalysts, comprising:

• (A) introducing a formose solution at a concentration of at least 20%, the pH of which solution has been adjusted to a value of from 7.5 to 12.5, batchwise into a first reactor at a rate such that the concentration of reducible groups (determined as carbonyl groups) inside the reactor does not exceed 2% by weight;
• (B) hydrogenating said solution batchwise in the presence of a catalyst, said catalyst content remaining constant in said reactor;
• (C) withdrawing the reaction product batchwise from the first reactor when the concentration of reducible groups (determined as carbonyl groups) has fallen below 1.5% by weight;
• (D) adjusting the pH of the prehydrogenated product thus obtained to a value of from 1 to 6 and maintaining a temperature of 10.degree. to 100.degree. C. for from 10 minutes to 2 hours;
• (E) introducing the reaction product thus obtained batchwise into a second reactor, the pH of said product being readjusted to a value of from 7.5 to 12.5, immediately before introduction of the product into the second reactor;
• (F) hydrogenating the product batchwise in the presence of a catalyst, said catalyst content remaining constant in said reactor;
• and
• (G) withdrawing the reaction product batchwise from the second reactor after a dwell time of from 5 minutes to 4 hours, further characterized in that the amount of said formose solution introduced into each reactor is from 3 to 30 times the amount of catalyst present in each reactor.