DE1096891B - Process for the preparation of polyhydric aliphatic alcohols - Google Patents

Description

It is known to convert cane sugar into a mixture after inversion with acids in the presence of hydrogenation catalysts of polyhydric alcohols consisting of glycerin, propylene glycols and sorbitol. For In this process, pure crystallized sugars must be used, since sugar syrup is essential to the trade results in poorer yields and, above all, practically no glycerol. It was also described that also let xylose hydrogenate in the presence of nickel catalysts at temperatures above 250 ° C. About the Type of the resulting products are only given imprecise information with the statement that with this process only very small amounts of glycerol and larger amounts of propylene glycols are obtained. It is well known that purified wood sugar solutions after neutralization let it transform into a mixture of sugar alcohols.

It has now been found that wood sugar flavorings such as those obtained from the acid hydrolysis of wood can be obtained can be converted into polyglycols after neutralization and clarification through multi-stage hydrogenation, whose carbon number is lower than in the original sugars.

It was surprisingly found that sugar alcohols which can be obtained by simple hydrogenation obtained from aqueous wood sugar solutions, side by side in several stages in polyhydric alcohols with lower Allow carbon number to be transferred, wherein in a first stage z. B. Hexite and in a second stage at higher temperature the pentites are split. The presence of the pentite disturbs the splitting of the Don't hex.

According to the invention is preferably such process is that purified and neutralized wood sugar seasoning in a vacuum at temperatures of 40 to 60 ° C to about 50 _^0/0 concentrated on reducing sugars. A further cleaning takes place by separating out resins. The concentrated sugar solution is then hydrogenated with nickel catalysts at pressures of about 40 to 70 atmospheres and at temperatures of about 50 to 70 ° C. for several hours. The yield of sugar alcohols is practically quantitative here. The resulting solution, which now contains pentite and hexite, is filtered off from the nickel catalyst and hydrogenated together with a copper oxide-containing catalyst at a pressure of 100 to 200 at and a temperature not exceeding 210 ° C., the hexite for the most part in glycerol and propylene glycol are cleaved. The reaction mixture is now, without the catalyst having to be separated off, possibly distilled in vacuo, the hexite fragments present being separated off. The remaining pentitol solution, which contains only a small amount of hexite, is then used in the presence of the catalyst at a temperature above 250 ° C., a process for the preparation

of polyvalent aliphatic

Alcohols

Applicant:

INVENTA A. G. for research

and patent exploitation,

Lucerne (Switzerland)

Representative: Dr.-Ing. Dr. jur. H. Mediger, patent attorney, Munich 9, Aggensteinstr. 13th

Claimed priority:
Switzerland from April 12, 1956

Dr. Fritz Conradin, Tamins, Graubünden,

Giuseppe Bertossa, Domat, Graubünden,

and Dr. Johann Giesen, Haldenstein, Graubünden

(Switzerland),
have been named as inventors

preferably at 250 to 300 ° C, a second hydrogenation subject.

The two reaction solutions from the first and second stage are now after separation of the catalyst, combined or separately, rectified, whereby one glycerin, 1,3-propylene glycol, 1,2-propylene glycol and Ethylene glycol. The total yield is about 80 to 90% based on sugar. The percentage of glycerin can be up to 60%.

The reaction can be influenced by promoters. If you z. B. Silver used as a promoter, it turns out that more ethylene glycol is obtained, especially in the second stage of the hydrogenative cleavage.

From the German patent specification 892 590 it is known to directly use starch and other carbohydrates, d. H. by hydrogenation in the presence of phosphoric acid at 150 to 170 ° C, in sorbitol and after neutralization to convert phosphoric acid into glycerine and glycols at 200 to 230 ° C.

From the known patent application N 1498 IVd / 12 ο is a two-stage hydrogenation of coal

009 698/505

l · 096B »

hydrates, such as dextrins and technical glycose, in Presence of reducing metals known.

example 1

A 4% sugar spice from the wood saccharification pröze'ß according to Scholler is blunted to Ph = 5 and evaporated in vacuo at 60 ° C to a content of 40% sugar and clarified over a filter press.

In a mixing vessel with a stirrer is in this Solution of finely divided Raney nickel (5 percent by weight, based on the sugar content) -suspended. By means of a Injection pumps are fed every hour 1501 (containing 60 kg of sugar) of this mixture - together with hydrogen gas - from below pumped a pressure vessel and treated with hydrogen at a pressure of 55 atü. the The residence time is 8 hours and the temperature is kept at 60.degree. At the top of the pressure vessel is a corresponding amount of aqueous mixture is continuously withdrawn. The excess is stored in a separator Hydrogen removed and pumped back into the pressure vessel together with fresh hydrogen. In a Filter press is removed after cooling the solution, the catalyst, whereupon the solution, which hexites and Pentite is kept in an intermediate tank.

The aqueous solution thus obtained is in a mixing vessel with 4% (based on the content of hexitol and Pentite) finely powdered copper chromite and mixed in an amount of 1001 per hour together with hydrogen pumped from below into a pressure vessel. The amount of hydrogen is calculated so that one in the reaction chamber Pressure of 155 atm is maintained. The temperature is kept at 205 ° C by a thermostatted heating jacket, the residence time is 7 hours. At the At the upper end of the pressure vessel, an amount of the mixture corresponding to the supply is continuously withdrawn and from this the excess hydrogen is separated off via a separator and together with fresh Hydrogen returned to the reaction vessel.

In a distillation column, the solution is dehydrated at normal pressure and heated further. So you get out 1001 solution used 29.5 kg (corresponding to 74% of the sugar used) of a clear, colorless distillate that boils at 180 to 192 ° C.

The distillation residue (29.2 kg), which mainly consists of pentitol and catalytic, is 301 Water mixed and pumped together with hydrogen from below into another pressure vessel. Under a The hydrogenating cleavage of the pentitol takes place at a pressure of 160 atmospheres at a temperature of 260 ° C. The reaction products are continuously drawn off and worked up by distillation. Obtained after removal of the water one 18.5 kg of a colorless distillate, which at 186 to 199 ° C boils:

The analysis of the distillates shows the following composition:

From 40 kg of the mixture of hexitol and pentitol were obtained:

in the first distillate

12.4 kg glycerine,
6.1 kg propylene glycol,

in the second distillate

3.5 kg of glycerine,
7.8 kg propylene glycol,
, 7.2 kg ethylene glycol,

total

15.9 kg glycerine 39.7%

13.9 kg propylene glycol .. 34.8%
9.1 kg ethylene glycol ... 22.8%

Example 2

Yield,

based

on the

used

sugar

The hexitol-pentitol solution was prepared as in the previous example, and the hydrogenative cleavage was carried out in a similar manner, but with the following Changes: -

The catalyst used was' 5 percent by weight Silver-copper-chromium oxide mixture used. The first stage of the cleavage took place at 160 atmospheres and 207 ° C. 1501 solutions were enforced every hour. In the second reaction stage, the pressure was 170 atm and held the temperature at 255 ° C.

Work-up by distillation was carried out as in the first example.
Exploit:
38.2% glycerine,
31.3% propylene glycol,
25.8% ethylene glycol.

Claims (4)

Patent claims: 1. Process for the preparation of polyhydric aliphatic, straight-chain, saturated alcohols containing less than 5 carbon atoms in the chain by hydrogenation cleavage of pentite and hexite Wood sugar solutions at temperatures above 100 ° C and at pressures above 100 at in the presence of Catalysts, characterized in that the hydrogenation cleavage of the hexites is carried out in a first stage at temperatures below 210 ° C and the hydrogenation cleavage of the pentite in a second stage Temperatures above 210 ° C. 2. The method according to claim 1, characterized in that the reaction in the second stage at a temperature of 250 to 300 ° C takes place. 3. The method according to claim 1 and 2, characterized in that the obtained from the first stage Cleavage products are removed from the reaction mixture, whereupon the uncleaved products in the second stage are cleaved by hydrogenation. 4. The method according to claim 1 and 2, characterized in that the catalyst contains chromium oxide Mixed catalysts are used. Considered publications: German Patent Nos. 634 588, 889 890, 804, 892 590; German patent application N 1498 IVb / 12 ο (announced on March 19, 1953); U.S. Patent Nos. 2209 055, 2,004135; 201 235.