CS199065B1 - Process for continuous hydrogenation of mixture of saccharides in liquid phase - Google Patents

Description

(54) A method of continuous hydrogenation of a mixture of carbohydrates in a liquid phase

SUMMARY OF THE INVENTION The present invention provides a process for the hydrogenation of saccharides in a liquid phase. There are known processes in which the hydrogenation of non-reducing and reducing carbohydrates is carried out by first hydrolyzing the non-reduced sugars with inorganic or organic acids or salts, at PH 3, after which the solution is neutralized to PH 6-8 and then the solution is hydrogenated mild conditions (U.S. Pat. No. 2,759,024 or British Pat.

742 553). In other methods, the process is carried out in a stepwise manner such that only glucose is hydrogenated at low temperature, and higher carbohydrates are then hydrogenated at higher temperatures (Brit. Pat. 625,171). Sometimes it is necessary to add an acid to the solution to promote hydrolysis of the polysaccharides. According to another process (U.S. Pat. No. 2,968,680), the process is conducted by conducting the first hydrogenation step in a neutral medium (PH 6-8) at t -140-160 ° C, then adding a strong mineral acid (e.g. HgPO 4). ₄ ) and then ae hydrogenated at higher temperatures of 200 to 220 ° C. It is known that the reaction rate of carbohydrate hydrogenation increases with increasing PH, but not the alkaline environment disrupts carbohydrate structure, which in turn leads to contamination of the hydrogenation product. However, in an alkaline environment, oligosaccharides are not hydrolyzed, therefore, wherever it is desired to hydrolyse the polycarbohydrates contained in the feedstock, the PH is usually treated to the acidic region (e.g., acids to the PH3 region, or some salts).

It is known that hydrolysis is a first-order reaction where the loss of oligosaccharide concentration over time is proportional to the initial concentration. The resulting monosaccharide is immediately subjected to hydrogenation, the degree of which is proportional to the environmental conditions. The rate of both reactions, i.e. both hydrolysis and hydrogenation itself, generally increases with increasing temperature. However, in the temperature range of 120-135 ° C, the Ni cat. Hydrogenation of the monosaccharides remains constant. A disadvantage of the previously known hydrogenation processes is, in particular, the fact that to carry out the hydrolysis of the disaccharide

199 Ο65

199 065, foreign components (usually inorganic or organic acids) must be added to the solution, which must be removed from the solution during the final treatment, and the process is therefore technically and aparsturnly more convenient.

The proposed process of the invention processes mixtures of monoeacharides (e.g. glucose) and disaccharide (e.g. eacharose) in varying percentages from S to 95% monoeacharides (glucose) and 95 to 5% disaccharide; The total carbohydrate content of the ee solution is from 20 to 80%, preferably from 50 to 70% eel. For the hydrolysis of non-reducing sugars (e.g. eacharose), the initial acidity of the initial mixture and the acidity of the hydrogenation product of the initial mixture are used. The procedure is further characterized by. The hydrolysis process is carried out at temperatures above 100 ° C in a mildly acidic environment at a rate such that the rate of hydrolysis is sufficient for the hydrogenation process.

Example 1

To a solution containing 5% eacharose and 45% glucose, a hydrogenation RA-Ni catalyst is added in an amount of 4.0 to 5% by weight. (not in euine). This slurry is conveyed by a pump under high pressure hydrogenation at a pressure of 10 to 20 MPa. Before entering the preheater, ee is mixed with the necessary amount of pressurized hydrogen and preheated to a temperature of 120 to 140 ° C and not the first stage of hydrogenation. After passing through the reactor at 1 stage and further heated to 160 to 200 ° C and passed to the reactor at the second stage. After cooling and separation of unreacted hydrogen, the mixture is expanded and passed on filtration to separate the catalyst. The resulting product after demineralization has about 5% mannitol.

Example 2

To the solution containing 60% eacharose and 5% glucose a, the hydrogenation RA-Ni catalyst is added in an amount of about 4 to 6%. This slurry is conveyed by the pump to a high pressure hydrogenation at a pressure of 10 to 20 MPa. Before entering the preheater, it is mixed with the necessary pressurized hydrogen, preheated to 120 to 140 ° C β leading to the first hydrogenation stage. After passing through the reactors in 1 stage, the mixture is preheated to 160 to 200 ° C and fed to the second stage reactors. After cooling and separating the gas, the mixture dispatches and does not filter. The final product after demineralization contains 61% hexltols, of which about 22% mannitol, 0.090% reducing sugars and 0.160% total sugars (the term total sugars within the meaning of this proposal represents the etching of Schoorl reducing sugars, the sample being prior to hydrolysis determination). , 1 M HCl for 1 hour in a water bath),

BRIEF SUMMARY OF THE INVENTION

Claims (2)

BRIEF SUMMARY OF THE INVENTION A process for the continuous hydrogenation of a saccharide mixture in a liquid phase, characterized in that the hydrolysis of dieecharides and hydrogenation is carried out simultaneously in a slightly acidic region at a pH of 4.5 to 6.7 at a temperature of 100 to 170 ° C and a pressure of 5 to 26 MPa. 2. Process according to claim 1, characterized in that the acidity of the monoeacharides used or the acidity of the hydrogenate formed during the hydrogenation is used for the hydrolysis.