Glycerol distillation process

• US 4,655,879 A
• Filed: 10/26/1984
• Issued: 04/07/1987
• Est. Priority Date: 10/28/1983
• Status: Expired due to Term

• Current Assignee: Cognis Deutschland GmbH & Co. KG (BASF SE)
• Original Assignee: Henkel KGaA (Henkel AG & Co KGaA)
• Inventors: Meyer, Helmut, Brockmann, Rolf, Johannisbauer, Wilhelm, Jeromin, Lutz, Plachenka, Juergen, Michel, Otto
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Manoharan, V.
• Application Number:
  US06/664,902
• Time in Patent Office: 893 Days
• Field of Search: 203/37, 203/49, 203/31, 203/41, 203/36, 203/98, 203/80, 203/87, 203/DIG. 19, 203/99, 203/73, 203/89, 435/159, 502/418, 568/854, 568/869, 210/694, 202/205, 202/186, 202/236, 159/49, 159/5
• US Class Current: 203/37
• CPC Class Codes: B01D 3/148 in combination with at least one evaporator
• CPC Class Codes: B01D 3/322 Reboiler specifications
• CPC Class Codes: C07C 29/80 by distillation
• CPC Class Codes: C07C 31/225 Glycerol
• CPC Class Codes: Y10S 203/20 Power plant

Abstract

An improved process for purification of glycerol obtained from natural sources comprising alkalizing a glycerol-containing crude mixture in the presence of air for oxidation, evaporating the mixture in a thin-layer evaporator with redistillation of the residue, rectification and reevaporation in a packed column characterized by low-pressure-loss plates with a falling-film evaporator designed for internal and external partial condensation and to separate off unwanted constituents of the mixture, bleaching the product with activated carbon and separating the bleach in known manner.

Claims

1. A process for the purification of crude glycerol derived from the transesterification, hydrolysis, and saponification of naturally occurring fats and oils, comprising

(a) alkalizing crude glycerol containing up to 10% by weight of water without predrying and chemical prepurificaton by mixing with an aqueous alkali hydroxide solution for about 1 hour at about 90°

-100°

C., followed by the addition of about 10 N/m³ of air per cubic meter of said crude glycerol;

(b) distilling the alkalized mixture at about 165°

-180°

C. and about 10-20 mbar and discharging high boiling constituents for additional distillation;

(c) passing the vapors generated by said distillation into a lower part of a packing column and flowing said vapors upward through said column, said column containing low-pressure-loss plates having a pressure loss of at most 1 mbar/theoretical separation stage at an air velocity of 2 m/s and having at least seven theoretical separation stages;

(d) partially first condensing the vapors from said column at about 80°

-90°

C. under a head pressure of about 5-10 mbars, and second condensing the remaining vapors at about 20°

-30°

C., so that the second condensate corresponds to approximately 1% of the quantity of crude glycerol;

(e) cooling the first condensate by about 30°

-50°

C. and returning same to the head of said column;

(f) continuously removing a main product from said column as a liquid sidestream at a point approximately 1/3 of the height of said column, and returning a partial stream thereof to said column beneath the point of removal;

(g) cooling the remaining non-returned portion of said main product to about 80°

-90°

C.;

(h) adding about 0.1 to 0.3% by weight of activated charcoal to the said non-returned portion as a bleaching agent and stirring under nitrogen for about 15 to 30 mintures while at about 80°

-90°

C.; and

then removing said bleaching agent;

(i) drawing off bottom product from the column sump, evaporating said bottom product at temperatures of about 150°

-180°

C., and returning vapor generated thereby to said sump,

(j) continuously removing a partial stream of about 1% of the quantity of glycerol being processed from said bottom product before it is evaporated.

2. The process of claim 1 wherein in step (i) said evaporating is by falling-film evaporation of said bottom product.

3. The process of claim 1 or 2 wherein about 2 to 4 kg of superheated steam per 100 kg of glycerol being processed is introduced during the evaporation of step (i).