DD281182A5 - METHOD FOR PRODUCING SAID FAT ALCOHOLS - Google Patents

Abstract

The invention relates to a process for the preparation of saturated fatty alcohols from esters of fatty acids having acid numbers of 2 to 10 by catalytic high-pressure hydrogenation, at temperatures of 490 to 540 K, hydrogen pressures of 18 to 30 MPa and stationaer arranged copper-containing hydrogenation catalysts. 10 to 50% of the amount of ammonia required to neutralize the acid number present is added to the ester. In addition to the elimination of refining when using esters or avoiding damaging the catalyst when using free fatty acids, the particular advantage lies in the use of hydrogenation plants intended for ester hydrogenation without significant technical changes. saturated fatty alcohols; synthetic fatty acids; esters; high pressure catalytic hydrogenation; copper-containing hydrogenation catalysts; Ammonia}

Description

Field of application of the invention

The invention is applicable in the chemical industry to the production of saturated fatty alcohols from esters of synthetic fatty acids by high pressure catalytic hydrogenation.

Characteristic of the known state of the art

The catalytic high-pressure hydrogenation of fatty acids and fatty acid esters is a process carried out for over 50 years, which is detailed in the literature. An up-to-date overview can be found, for example, in Ulimann's Encyclopaedia of Technical Chemistry 4. Aufig. Vol. 11, p.432ff.

The technical solutions for process control basically require conditions that protect the predominantly used Cu-containing catalysts from the corrosive attack of acidic components of the reaction components. Therefore, the esters of fatty acids are preferably used for the hydrogenation.

Due to their purity, fatty acids of natural origin can be reduced relatively easily down to acid numbers less than 2. The esters are then treated with highly active bleaching earth and then distilled. In this purified form, the acid numbers are less than 1, and the products hydrogenate well with little catalyst overhead. Synthetic fatty acids, preferably from the Pfiraffinoxidation, can be due to their content of polyfunctional compounds with reasonable effort only to acid numbers of about . to age 10. Sufficient distillate deacidification of these esters is not possible. They must therefore be subjected to hydrogenation on stationary catalysts ei ^r ar alkaline refining. Despite workup of the acids contained in the resulting suds in their renewed esterification and refining material losses are very high. The esters of acids recovered from the refining liquor are hydrogenated only with high catalyst consumption.

Special effort requires the removal of small traces of Nalriumseifen from the refined esters, since they irreversibly damage the hydrogenation catalysts in very low concentration.

The technical effort for the refining and reprocessing of Raffinationslaugen are associated with an additional process stage and other costs.

The hydrogenation of free fatty acids is possible with reasonable catalyst consumption only in the liquid phase with suspended catalyst. To avoid fatty acid attack on the catalyst, a large excess of fatty alcohol formed is recirculated in a reactor with internal or external recirculation. The fed fatty acids are in a very short time in the reactor Verestf rt, so that the Hydriei J nc ι almost exclusively on the ester. The disadvantage of this procedure is the consuming! Separation of the catalyst from the reaction product. At pipe bends and valves, the abrasive effect of the catalyst suspension leads to rapid material removal and thus to short life of these equipment. Furthermore, there are disruptive catalyst deposits in the reactor, in pipelines and heat exchangers.

By comparison, the process according to DD-PS 213430 represents an advance. According to this patent, the hydrogenation of free fatty acids is carried out in the presence of excess basic nitrogen compounds on stationary Cu catalysts. The intermediately formed ammonium or amine soaps and an excess of base protect the catalyst. However, an analysis of the process also reveals critical points in this process, which limit its extensive use. Such disadvantages are mainly to be seen in that with a substantially molar. Excess of basic component to secure the protective function of the catalyst must be worked, on the one hand requires a complicated circulation sensing of the liberated in the crude hydrogenation bases and on the other hand, especially when using synthetic fatty acids, already Umalkylierungsprodukte be detected in the alcohols, with increasing ratio base to Fatty acid increase. In addition, the complete sealing of the recycle and circulation facilities for the basic component causes difficulties that cause strong odor nuisance, especially when using trimethylamine. Further disadvantages are that the technical solution according to this principle requires an acid-resistant design of the containers, pumps, pipelines and valves to the reactor inlet and that the hydrogenation of the soaps formed compared to other raw materials, a significant reduction in the space-time yield, based on the same catalyst result Has.

Target de ^'1 invention is to develop a process for the preparation of saturated fatty alcohols by Catalan Hocharuckhydrierung esters of synthetic fatty acids of the stationary catalyst columns, which the aforementioned disadvantages dor known method does not have.

Explanation of the essence of the invention

Consequently, the object of the invention is to find for the high-pressure hydrogenation of esters of synthetic fatty acids still containing small amounts of stationary fatty acid catalysts under conditions in which the acid-sensitive Hydrtorkatalysator is not attacked and its activity and selectivity for the hydrogenation of the carboxyl group to the hydroxyl group not loses.

According to the invention, this object is achieved in that the in fatty alcohol production by catalytic high-pressure hydrogenation on stationary copper catalyst columns between 490 and 540K, hydrogen pressures of 18 to 30MPa and use of acidic components containing fatty acid esters having an acid number of 2 to 10, based on the acid number deficit of basic nitrogen compounds, primarily ammonia. This intermediate is due to the elimination of the refining process and thereby inevitably resulting workup of Raffinationslauge particularly inexpensive to produce and is used in place of refined esters. Surprisingly, the amount of ammonia necessary for long catalyst service lives when using alkyl esters of synthetic fatty acids, preferably from the paraffin oxidation, is only 10 to 50% of the neutralization equivalent required for the residual acid number. This fact proves that with such a procedure, the protection of the catalyst is not ostensibly caused by soap formation with the corresponding acid number of the present acidic components, but directly by a surface protection of the catalyst. The small amounts of ammonia escape during the relaxation of the hydrogenation products and doren subsequent distillation. There is no quality deterioration of the alcohols. A recycling of the ammonia is not required. The concentration of amine compounds formed by transalkylation in the fatty alcohols is so low that it lies at the error limit of the determination methods. In addition to the elimination of refining when using esters or avoiding damage to the catalyst when using free fatty acids, the particular advantage of the process according to the invention is the use of the hydrogenation plants intended for ester hydrogenation without significant technical changes. The invention will be further illustrated by the following examples: Description of the recurring in all examples conditions.

The hydrogenation plant consists of a vertical tubular reactor filled with the hydrogenation catalyst, a closed circulation system with gas circulation pump for the hydrogenation gas to be passed through the reactor in large excess, a product pump, 2 pre-heaters for hydrogenation product and hydrogen upstream of the reactor, condenser and liquid separator behind the reactor.

The tableted catalyst containing Cu and Zn in the ratio 3: 2 is reduced after filling in the reactor. The reduction conditions are:

H ₂ pressure: 10MPa H ₂ throughput: 4 NmVh Temperature rise in the reactor: 5-10 K / h Max. Temperature: 545 K

Under these conditions, the catalyst is reduced for 2 hours and then the reactor temperature is lowered to the desired hydrogenation temperature.

The general hydrogenation conditions are:

Catalyst volume: 3.61 H ₂ throughput: 60NmVh H ₂ pressure: 24MPa

For this purpose, the ester is conveyed via the product pump into the reactor. The hydrogenation product is continuously released from the separator. At intervals of 2 hours, hydrogenation samples are taken and analyzed analytically. The NH3 treatment of the ester takes place by passing quantity-proportional streams of esters and ammonia through a mixing zone at temperatures between 300 and 360K.

Example 1 (comparative example according to the prior art)

A butyl ester of a mixture of synthetic fatty acid v. R. which consists to more than 80% of η-fatty acids having 10 to 16 carbon atoms, used at a rate of 1.2 kg / hindem reactor described above. The ester has an acid number of 6. The hydrogenation temperature is 500 ± 5K. The hydrogenation product has the following characteristics after removal of the butanol

SZ: ί VZ: 2,1 JZ: 1

After a 2-day drive, the hydrogenation effluent turns red-brown through catalyst constituents, and the measures have changed as follows.

SZ: 1,5 VZ: 16 JZ: 1

After another 2 days, the activity of Jes catalyst is exhausted. The hydrogenation products are still colored reddish brown and the VZ has risen to> 30. Increasing the temperature of the reactor by 16K causes a temporary decrease in saponification numbers for only one day.

Example 2 (Inventive Example) It is a butyl ester according to Example 1 and the conditions mentioned there, are added to the 0.8 g of NH ₃ per kg of ester, with

a fed of 1.8 kg / h in the reactor described above.

The hydrogenation product has the following characteristics after removal of the butanol

SZ: 0.2 VZ: 2 JZ: 0.5

After 14 days driving, the key figures have not changed significantly. The Hydrierabiauf is colorless. Example 3 (Inventive Example) It is the methyl ester of a mixture of synthetic fatty acids containing more than 80% of η-fatty acids with 6 bis

9 carbon atoms is used, with a throughput of 2.0 kg / h in the reactor described above. The ester with an acid number of 4, 0.25 g of NH _{3 are added} per kg of ester.

The hydrogenation temperature is 500 ± 5K. The hydrogenation product has, after separation of the methanol, the following Kennznhlen

SZ: 0.1 VZ: 1.1 JZ: 0.2

After a fortnightly drive, the key figures did not change significantly. The product is colorless. Example 4 (Inventive Example) A butyl ester of a mixture of synthetic fatty acids is added to 1 g of NH ₃ / kg of ester and this is added to more than 80%.

consists of η-fatty acids having 10 to 16 carbon atoms, with a throughput of 1.8 kg / h in that described in Example 1

Reactor used and hydrogenated at 500 ± 5K. The ester has an acid number of The hydrogenation product is colorless and, after removal of the butanol, has the following characteristics:

SZ: 0.3 VZ: 1.9 JZ: 0.7

After 14 days driving, the key figures have not changed significantly. The hydrogenation process is still colorless. After a temperature increase to 535 K and an increase in throughput to 2.3 kg ester / h on the 15th day, the hydrogenation sequence has the following characteristics

VZ: 2,1SZ: 0,2JZ: 0,5

The hydrogenation process is still colorless.

Claims (2)

1. A process for the preparation of saturated fatty alcohols by catalytic high-pressure hydrogenation of methyl to butyl esters of synthetic fatty acids having acid numbers of 2 to 10 at temperatures from 490 to 540K and hydrogen pressures of 18 to 30 MPa of stationarily arranged copper-containing hydrogenation catalysts, characterized in that the still acidic components with an acid number of 2 to 10 containing fatty acid ester prior to hydrogenation, basic nitrogen-containing compounds in an amount of 1J to 50% ₍ based on the acid number, are added. 2. The method according to claim 1, characterized in that ammonia is used as the basic nitrogen compound.