US 5,510,542 AGranted

Process and apparatus for producing diglycerin

AssigneeSolvay Fluor und Derivate GmbH

InventorsGerald Jakobson, Werner Siemanowski

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Abstract

A process for producing diglycerin having a low content of cyclic components by reacting glycerin with epichlorohydrin by a continuous process in which the epichlorohydrin required for the reaction is introduced into at least one flow reactor at several separate spots or reaction zones mutually separated in space in the direction of flow; the reacted reaction mixture is substantially freed of excess glycerin in at least one evaporator; the remaining chlorohydrin/ether mixture is hydrolyzed in at least one first step with a 5 to 40 mole % excess alkali carbonate solution, calculated with respect to organically bound chlorine in the chlorohydrin ether, at a pH of 6.5 to 9.5, and hydrolysis is at least substantially completed in a second step with an alkali hydroxide at a pH above 10; the resulting hydrolyzed crude product solution is adjusted to a pH of 5.5 to 8 with a mineral acid, preferably hydrochloric acid; and the resulting solution is condensed, precipitating salts are removed, and the diglycerin solution containing less than 8% by weight residual inorganic salts is freed of cyclic diglycerin and residual glycerin in a flash evaporator. Apparatus for carrying out the foregoing method is also disclosed.

Claims24

Dependent claims

A process for continuously producing diglycerin having a low content of cyclic constituents, said process comprising the steps of:

reacting glycerin in at least one continuous flow reactor with epichlorohydrin introduced into said at least one flow reactor at a plurality of spatially separated reaction zones at an overall molar ratio of glycerin to epichlorohydrin of 20:1 to 1:1, a temperature of from 20.degree. to 120.degree. C. and in the presence of an acid catalyst to produce a diglycerin-containing reacted mixture;
subsequently removing excess glycerin from said mixture by evaporation in at least one evaporation device to obtain a chlorohydrin and ether mixture;
hydrolyzing the chlorohydrin and ether mixture in a first hydrolysis stage at a temperature of 60.degree. to 120.degree. C. and a pH of 6.5 to 9.5 with a 5 to 40 mole-% excess of an alkaline reacting alkali carbonate solution calculated with respect to organically bound chlorine in the chlorohydrin and ether mixture,
completing hydrolysis of said chlorohydrin and ether mixture in a second hydrolysis stage at a pH of above 10 with alkali hydroxide to obtain a hydrolyzed crude product solution;
adjusting the hydrolyzed crude product solution to a pH of 5.5 to 8 by addition of a mineral acid;
concentrating the resulting solution and separating precipitated salts to obtain a diglycerin solution containing less than 8% by weight of residual inorganic salts;
and
freeing the diglycerin solution of cyclic diglycerin and any residual glycerin by distillation in at least one flash evaporator.

5 more elements

An apparatus for continuously producing diglycerin having a low content of cyclic constituents, said apparatus comprising connected in succession:

at least one continuous flow reactor divided by at least one cross-sectional constriction into at least two reaction zones at different levels therein, said reactor having a lower end with at least one inlet for a stream of glycerin and an acid catalyst and an upper end with at least one outlet for a glycerin/epichlorohydrin reaction mixture, a stirring shaft arranged coaxially and centrally in said reactor with at least one stirring device fastened to said shaft in each reaction zone of the reactor, and an epichlorohydrin supply conduit arranged in said reactor parallel to the stirring shaft and spaced radially outwardly from said at least one stirring device, said supply conduit having at least one outlet opening into each reaction zone of the reactor through which epichlorohydrin can be introduced into the respective reaction zone;
at least one evaporation device for removing excess glycerin,
at least one first stage hydrolysis reaction vessel connected to a source of an alkali carbonate solution,
at least one second stage hydrolysis reaction vessel connected to a source of an alkali hydroxide, and
at least one flash evaporator for removing cyclic diglycerin and unreacted residual glycerin.

2 more elements

Dependencies are inferred from the claim text.