DE1112056B - Process and device for the production of fatty alcohols by catalytic hydrogenation of fatty acids and their derivatives - Google Patents

Description

Method and device for the production of fatty alcohols by catalytic hydrogenation of fatty acids and their derivatives The invention relates focuses on a process for the catalytic hydrogenation of fatty acids and fatty acid derivatives to fatty alcohols in the liquid phase at elevated pressures and elevated temperatures in the presence of copper-chromium oxide catalysts.

The fatty acid hydrogenation with copper-chromium oxide catalysts, that too can be activated by additional components has long been known.

Since the catalysts are sensitive to free acids and water, usually not the free fatty acid but a fatty acid ester is used for the hydrogenation, preferably the methyl ester.

The fatty acid methyl esters can be easily converted by transesterification of neutral fats. However, it is often undesirable to do so inevitably Glycerine is obtained, which has to be processed separately. Plus it is in many Cases of economical waste fatty acids or of fatty acid distillates certain composition. The esterification that then becomes necessary the fatty acid with methyl alcohol is difficult and costly. Besides, the Recovery of the methanol from the hydrogenation material and the concentration of the methanol associated with additional expenditure on equipment and costs before reuse.

For obtaining a usable starting product with an acid number below 0.5 distillation of the methyl ester is required. During the hydrogenation part of the methyl ester decomposes and free methanol is broken down, whereby the released carbon monoxide either damages the catalyst or closes it Methane is hydrogenated.

For the process according to the invention for high pressure hydrogenation is therefore expediently assumed esters of fatty acids with native alcohol.

The esterification of the fatty acids to be hydrogenated with that in the hydrogenation resulting alcohol or alcohol fractions is usually carried out in such a way that that the acid and the alcohol are heated together in a stoichiometric amount. The esterification takes place up to a residual acid number of about 10 rapidly, while the residual esterification down to an acid number of less than 0.5, such as it is generally required for the hydrogenation, a multiple of that mentioned above Takes time.

According to the invention, fatty acid or an incomplete for the hydrogenation esterified mixture of fatty acid with alcohol or initial alcohol formed from it introduced into the high pressure system for hydrogenation. The residual esterification then takes place in the hydrogenation apparatus. For this purpose it is necessary agile that the to be hydrogenated Well currently alcohol is introduced into an excess of fat under conditions that with regard to temperature, mixing and possibly also removal of the water of reaction are favorable for esterification. The entire contents of the hydrogenation apparatus exist So from practically fully reacted material, which is saturated with hydrogen and more intensely Movement is kept.

The conditions known per se, d. H.

Temperatures from 200 to 3500 C and pressures from 200 to 700 at in High-pressure hydrogenation in the presence of copper-chromium oxide catalysts liquid phase is particularly advantageous for. B. performed in a system that of two vertically arranged high-pressure chambers connected to one another at the top and bottom exists in which a large amount of the reaction mixture circulates. The high pressure rooms are expedient by two very long, vertically arranged, top and bottom with each other connected high-pressure pipes formed with supply and discharge lines for the reaction products are provided. The ratio of the diameter to the length of the reaction space is preferably less than 1:10, e.g. 1: 100 to 1: 1000.

These high-pressure pipes can also be heated or cooled in a known manner will.

The hydrogen or the hydrogen-containing gas is expediently on The lower end of a high-pressure chamber of the circulation apparatus is finely distributed. The long, as narrow as possible, high-pressure space is designed so that the hydrogenation material from the bubbling hydrogen at a constant speed is granted and that the deflection at the upper end of the room in fluidic is done properly, so that local eddies and slowdowns in the Flow can be excluded. The finely divided rising hydrogen causes a reduction in the density of the reaction material in the ascending part of the system.

Reacted material and excess hydrogen are expedient pulled off the upper connector. The intensive circulation becomes practical Operation achieved by the fact that the amount of hydrogen passed through is more than 3 times expediently 10 to 50 times that required for the hydrogenation of the material fed in Amount of hydrogen. The circulation speeds achieved by the introduced hydrogen of the reaction mixture are at least 0.2 m / sec, expediently 1 to 2 / sec.

The excess hydrogen leaving the system or the hydrogen containing one Gas are used in the hydrogenation after the reaction products and the catalyst have been separated off returned. It is not necessary here to relax the hydrogen. It recommends rather, to relax only the reacted material and the part of the catalyst, which is withdrawn during continuous operation.

The continuous implementation of the fatty alcohol production process usually takes place in several autoclaves or elongated reaction spaces that one after the other from the fats to be hydrogenated and the catalyst suspended therein are flowed through and in which the fats repeatedly come into contact with hydrogen to be brought. Here, the material to be hydrogenated is continuously passed through the reaction space led but not fed into a room in which a large amount almost or completely reacted good in intensive mixing with the catalyst and the Hydrogen is held.

It is also known to use high pressure chemical reactions in autoclaves to be carried out, which are provided with a stirrer, or in devices in which the mixing with the gas and the circulation of the reacüonsgutes through the installation of a pipe is achieved. The reaction participants rise in this tube, while only the liquid phase remains in the space around the tube, or vice versa. Sufficient mixing can often not be achieved in these known devices, because the circulation is not strong enough to keep the slurried contact in more evenly Carry out distribution, and there are in the upper and lower part of the reaction chambers Zones can form in which the liquid reactants linger for a long time and thereby become starved of hydrogen. Due to the rapid circulation of the reaction material in the system of the invention consisting of two interconnected high pressure pipes the catalyst is constantly kept in fine distribution.

The reaction mixture preferably consists predominantly of already fully reacted fatty alcohol saturated with hydrogen. In these is the fatty acid or, better, the ester obtained from this fatty acid and its own alcohol is introduced and thanks to the intense movement immediately so evenly in a large excess distributed by fatty alcohol that the residual esterification takes place almost instantaneously. The invention makes use of the fact that the hydrogen in fatty alcohol is significantly more soluble than in fatty acids or fatty acid esters. Under the conditions The high pressure hydrogenation dissolves a certain amount of fatty alcohol about 25Bio more hydrogen than the same amount of fatty acid. In the method according to the invention serves primarily Line this dissolved and thus in a homogeneous phase hydrogen for hydrogenation. Because the contents of the reactor are constantly saturated with hydrogen, they also have The free fatty acids introduced into the material to be hydrogenated are not harmful to contact Effect more. In addition, the one already described makes free fatty acid practical instantaneous esterification with the large excess of fatty alcohol removed very quickly.

In the same way, catalyst poisons that are to be hydrogenated with Starting material get into the reaction chamber from a relatively large one circulating amount of catalyst was immediately taken up and thus rendered harmless. New fed-in catalyst reaches a practically detoxified medium and retains it hence its catalytic effectiveness for a longer period of time.

With the device according to the invention it is also possible in a simple manner, the addition of the material to be hydrogenated and the catalyst spatially from one another to separate so that a highly active, fresh contact does not contain fatty acids Starting materials comes into contact. For the introduction to the high pressure system the catalyst is expediently made into a paste with fatty alcohol or suspended in it.

By maintaining the high activity of the feed for a long time fresh catalyst in connection with that in homogeneous phase, d. H. in fatty alcohol dissolved hydrogen and that caused by the rapid circulation, practically instant removal of all catalyst-damaging substances results an extremely rapid and effective hydrogenation.

It is known that fatty alcohols under the conditions of high pressure hydrogenation tend to form olefins with elimination of water, which in turn again hydrogenated to saturated hydrocarbons. This side reaction can be avoided when the reaction temperature during the hydrogenation is as low as possible is held. The water of reaction released during the esterification reaction, which genuinely dissolved or in the gas phase, but never in the liquid form, acts as a brake on the formation of hydrocarbons in terms of chemical equilibrium. The conditions of the process according to the invention in their entirety ensure that that the aforementioned side reaction with the formation of hydrocarbons is practical is completely avoided. The hydrogenation temperature depends on the activity and the Depending on the amount of the catalyst and is advantageously 250 to 2800 C.

It is also possible to increase the throughput of the inventive Device to increase in such a way that the introduced raw product in the circulation system only about 90 to 95% 95%, for example up to a saponification number of 6 to 10 is hydrogenated. The reaction product, which is on the upper part of the circulation apparatus is withdrawn is sufficiently saturated with hydrogen and therefore can in a downstream high-pressure autoclave or another suitable high-pressure room under Maintaining the pressure and no further supply of hydrogen react.

With reference to the drawing, the method according to the invention and the used device explained in more detail: In the high pressure chamber 1 is by means of a Distribution device introduced hydrogen-containing gas, the predominant Part consists of cycle gas and which is circulated by means of the pump 4, but the fresh hydrogen can be added from the compressor even at 12. The hydrogen rises in the high-pressure chamber and thus intensifies the reaction mixture Circulation. The unused and undissolved hydrogen-containing gas leaves together with part of the reaction product the system at 5, gives its heat in one Heat exchanger expediently to supplied cycle gas or fresh products and reaches the downstream high pressure chamber 9, in which the hydrogenated material is accumulates while the hydrogen through the line 13 via the pump 4 in the Cycle returns. The hydrogenated product is expanded through the valve 10 and guided in a further container 11, in the bottom of which hydrogenated product is obtained and from which the flash gas is vented at 14. Fresh catalyst will the system at 7, suitably supplied in the vicinity of the hydrogen inlet. That Material to be hydrogenated is at 8 or another from the feed point of the catalyst at a remote location.

Example 1 The hydrogenation is carried out continuously in a magnetic lift stirring autoclave carried out with a content of 2 l. For this purpose, the autoclave is supplied with hydrogen provided that extends to the bottom of the reaction chamber. The Feed line for the fatty acid also carried out to the bottom of the reaction chamber. A third feed line, which is only carried out to the center of the reactor, is used for Feeding the catalyst suspension.

Reaction product, catalyst and hydrogen are shared over one Pulled off the pipe which protrudes 60 mm from the edge of the lid into the high-pressure chamber and maintains a certain reactor content by sniffing. The remaining one usable content is about 1 1.

For the hydrogenation, the autoclave is heated to 3000 C and on this Temperature held. About 300 cm3 of fatty acid are supplied per hour.

4% catalyst = 12 g / h are in the form of a 250% suspension fed into the autoclave through the connection provided for this purpose. The introduction of hydrogen is permanently open and connected to a compressor or a storage bottle, which maintains its pressure of 320 atmospheres. Through the sniffer tube, which with connected to a high pressure template, hydrogen will be the reaction product as well the catalyst is drawn off by continuously increasing an amount of hydrogen to 2 m3 / h relaxed via high pressure separator, low pressure separator and rotameter. That Expansion gas is brought back to working pressure by the compressor.

The distilled coconut fatty acid used for hydrogenation has a Acid number of 257, a saponification number of 260, an iodine number of 12 and a hydrocarbon content from 0.50 / 0. The one from the High pressure receiver withdrawn and freed from the catalyst Fatty alcohol has an acid number of 0, a saponification number of 3, and an OH number of 270, an iodine number of 0 and 0.75%, hydrocarbons.

After using the catalyst 20 times, its activity is like this much decreased that the temperature increased by 18 C to achieve the same numbers must become.

Example 2 The experimental setup is the same as in the example 1 described.

However, 900 cm3 of coconut fatty acid is used, the one with coconut alcohol is incompletely esterified except for an acid number of 15. The amount of catalyst added amounts to 3 <> / <> 18 g copper chromium oxide as a 25ol suspension.

The temperature was kept at 3000 C and the pressure at 325 atm. The alcohol freed from the catalyst has an acid number of 0, a saponification number of 10, an iodine number of 0 and an OH number of 254. The hydrocarbon content is 0.9 ° / c.

To achieve a lower saponification value, the reaction in a second autoclave of the same type at the same pressure and temperature continued. Hydrogen, catalyst and reaction product are made from the first Autoclave continuously passed into the top of the second autoclave.

The reaction product, hydrogen and catalyst are taken from the second autoclave through a sniffer tube, which protrudes 60 mm from the cover into the tube, into the High pressure separator removed.

Since the catalyst settles out, it is not possible for a long time Time for stirring or a movement of the reaction material due to the introduced hydrogen to renounce. As was determined by temporarily turning off the agitation, However, the hydrogen dissolved in the reaction product is generally sufficient to achieve the Carry out hydrogenation up to the desired saponification number. The key figures the end products with and without stirring were almost the same, namely: without stirring: AN = 0, VZ = 3, OH-Z = 267, KW = 1.1 ° / e; with stirring: SZ = 0, VZ = 2.7, OH-Z = 267.5, KW = 1.1 ° / e ,.

Example 3 The hydrogenation is carried out in a circulation pipe, that in its ascending part of a 6 m long and 45 mm wide tube and in its descending part consists of an equally long, 30 mm wide tube. Both tubes are through a 45 mm wide tube at the top and a 30 mm wide tube at the bottom Adapter connected. The highest point of the circulation pipe is connected to a high-pressure separator, which has a further separator as a drip catcher at the top Connected to the hydrogen inlet via the gas circulation pump and the preheater is. The hydrogen inlet is located at the foot of the ascending pipe. Of the Fresh hydrogen required to maintain the pressure is supplied by a Branch line 12 supplied upstream of the hydrogen circulation pump. The lower part of the separator is connected to a low-pressure reservoir via a shut-off and expansion valve, which in turn is in connection with the gasometer, for the discharge of the expansion gas. The catalyst suspension is in the descending part of the circulation system introduced. The hydrogenation is carried out at a hydrogen pressure of 300 atm.

A palm kernel coconut distillate with an acid number is used for hydrogenation of 265, a saponification number of 267 and an iodine number of 12. The hydrocarbon content is 0.5%. The copper chromium oxide catalyst is used as a 250-long suspension in an amount of 6 6% of the weight of the fatty acid introduced into the high pressure chamber. the Fatty acid addition is 8.5 llh. The temperature at the first pass through the catalyst at 300 ° C was sufficient must on the twenty-fifth pass of the catalyst can be increased to 3300 ° C. to achieve a lower saponification value. The key figures of the fatty alcohol applied are: acid number 0, saponification number 2.5, OH number 278, Hydrocarbon content 1 ° / o.

The raw alcohol containing the catalyst is placed in conical settling vessels, which are kept at 700 C and their size an average residence time allows 15 hours, continuously freed from the main amount of the catalyst, which is withdrawn below as a 20- to 600 / cige suspension. Last traces of the catalyst which are still contained in the running alcohol, are in a clarifying centrifuge severed.

Frequent re-use reduces the activity of the catalyst depending on the type and purity of the raw material, more or less depends on what is made by Temperature increase can be compensated. But you can also keep a little one Replace the proportion of the used catalyst with a fresh one, thereby reducing the reaction temperature keep it at a constant level.

Claims (9)

PATENT CLAIMS: 1. Process for the continuous production of Fatty alcohols through catalytic hydrogenation of fatty acids or fatty acid derivatives at temperatures from 240 to 3200 C and pressures from 200 to 700 at in the presence of copper-chromium oxide catalysts, which are modified by additional components can be, characterized in that the material to be hydrogenated continuously in a high pressure chamber is introduced, in which a large amount almost or completely reacted Good kept in intensive mixing with the catalyst and the hydrogen will. 2. The method according to claim 1, characterized in that fatty acid or an incompletely esterified mixture of fatty acid is used. 3. The method according to claims 1 and 2, characterized in that that the ratio of added material to circulating reaction mixture at least 1:10, preferably 1: 100 to 1: 1000. 4. The method according to claims 1 to 3, characterized in that that the amount of hydrogen passed through is more than 3 times, expediently 10- up to SO times the amount of hydrogen required to hydrogenate the feed amounts to. 5. Process according to claims 1 to 4, characterized in that that the catalyst is supplied in pasted or suspended form. 6. The method according to claims 1 to 5, characterized in that that the fatty acid is hydrogenated to 90 to 95 O / o in the circulation apparatus and that the complete hydrogenation takes place in a downstream high pressure vessel or pipe. 7. The method according to claim 1, characterized in that the to hydrogenating material at a point remote from the feed point of the catalyst is fed into the high pressure chamber. 8. Circulation apparatus for carrying out high-pressure reactions in liquid-gaseous form Phase for the production of fatty alcohols according to claim 1, characterized by two very long, vertically arranged high-pressure pipes connected to one another at the top and bottom with inlet and outlet for the reaction products. 9. Apparatus according to claim 8, characterized by one at the lower Apparatus known per se arranged at the end of one tube of the circulation apparatus for fine distribution of the gas in the liquid medium. References Considered: U.S. Patent No. 2,750 429; British Patent No. 723 887.