DE2613226B2 - Process for the continuous production of fatty alcohols - Google Patents

Description

It is known to produce fatty alcohols by catalytic high-pressure hydrogenation of fatty acids, their esters or anhydrides with hydrogen or hydrogen-containing gases at elevated temperature in the way make that the starting materials at the same time with the hydrogen or the hydrogen-containing Gases in the flowing system at pressures between approximately 100 and 500 atm. via lumpy catalysts directs. The catalysts used are in particular those made of copper chromite or copper-zinc-chromite, in particular but copper-zinc used, both with and without known carrier substances. To the It was necessary to protect the contact and to obtain a high quality fatty alcohol. Methanol is added to the hydrogenation in the cycle gas travel.

It was an object of the present invention to provide the known process for the preparation of fatty alcohols to simplify technologically through high pressure hydrogenation without deteriorating the product quality.

It has now surprisingly been found that the present object can be achieved in that the hydrogenation is carried out with the addition of 3 to 30% by volume of inert gas, based on hydrogen. as Inert gas is primarily nitrogen. In place of nitrogen, noble gases such as argon can also be used or neon or methane, at least in part, can be used.

It must be regarded as surprising that in the method according to the invention by the replacement Not only equally good end products are obtained from methanol, as is customary according to the prior art but also the yield, based on the contact consumed, is improved.

In the process according to the invention, customary catalysts for high pressure hydrogenation are used used, for example those based on copper and zinc.

Accordingly, the hydrogenation of the fatty acids or their esters, in particular carried out in manner known per se at temperatures above 120 ⁰ C, suitably between 200 and 25O ° C. At temperatures below about 250 ° C, the saturated fatty acids and their derivatives are reduced to alcohols. The pressures to be used are between 100 and 500, preferably 200 and 300 atm.

The starting materials are mixed with the hydrogen in the flowing system over the lumpy catalysts directed. The process is expediently carried out with an excess of hydrogen in which one the starting material with about 10 to 100 times the theoretically required amount of hydrogen passes through the contact volume Circulation is pumped through the hydrogenation apparatus and the hydrogen consumed by hydrogenation is ongoing Compared to the gas phase hydrogenation according to the prior art, one can use a lower one Get along with excess hydrogen.

As a starting material for the process according to the invention The saturated and unsaturated fatty acids found in natural fats or their

ίο Serving esters with monohydric aliphatic alcohols. Mixtures of the compounds mentioned can also be used.

Preferred starting materials for the process according to the invention are the volatile fatty acid esters

ti of fatty acids with 6 to 22 carbon atoms. the end For practical reasons, the fatty acid methyl esters are preferred. Of course, synthetic ones can also be used Fatty acids or their esters are hydrogenated

The replacement of the methanol requires, among other things

2i) the same conditions increase the throughput (Space / time yield) by at least 40% compared to the known prior art. The chemical Breakdown of the methanol to CO, H2O and dimethyl ether is considerably reduced by the new process

r> or excluded when using fatty acids. These gaseous forms that accumulate earlier in the cycle gas By-products therefore no longer have to be removed from the hydrogen or from the apparatus, since automatically with the resulting fatty alcohols

so be deposited. The amounts of water usually obtained in the hydrogenation of fatty acid methyl esters under the given reaction conditions (approx. 1%, based on the amount of ester used), are reduced to a third.

r> Finally, by not using lower Alcohols as a diluent save a considerable amount of energy because of the large amounts of diluent no longer have to be driven off from the reaction product.

4 (1 Finally, it should be noted that the Inert gas content, improved heat transfer of the cycle gas causes the increased specific Ester throughputs, which in itself are weak exothermic of the hydrogenation reaction, are sufficient to

4) the hydrogenation through optimal use of waste heat completely dispense with additional heating of the esters to the required reactor furnace inlet temperature to be able to.

- ₀ example 1

In a continuously operating high-pressure plant for the production of saturated fatty alcohols less than 250 at.n. at 240 ° C 40 l / h coconut fatty acid methyl ester together with the equivalent of 200 NmVh water

> ') substance to which 40 NmVh of nitrogen are mixed, evaporated and tabletted on about 30 liters of one Copper-zinc contact in two reactors connected in series (the first with 201, the second with 101 contact is filled) hydrogenated.

w) After the methanol has been separated off from the hydrogenation product becomes the coconut fatty alcohol in a yield of 99% received. The clear fatty alcohol has the following key figures:

OH number 287 iodine number 0.1 Saponification number 0.4 Hydrocarbon content 0.8%

Comparative experiment

According to DE-PS 10 05 497 , hydrogenation was carried out under the same conditions, but instead of nitrogen, 3 l / h of methanol were metered in. The table below compares the results found

Table I.

below 250 atm. Fatty acid methyl esters produced from natural fat at 230 ⁰ C 18 l / h together with the equivalent of 250 NmVh of hydrogen, to which 30 NmVh of nitrogen are added, evaporated and on approx. 30 liters of a tableted copper-zinc contact in two reactors connected in series (the first with 201, the second is filled with 101 contact) hydrogenated. The fatty acids in the methyl ester had the following chain length distribution:

with 10 C ₁₄ -FS 6% Way of working Methanol C ₁₆ -FS 30% with (Comparison) C ₁₈ -FS 62% nitrogen C ₂₀ -FS 2% (Invention) 15th

Max. Amount of included 3.5 2.7

put methyl ester, l / h

Hydrogen used, 30 50

mVh -'η

Molar WasstritofT- 60 100

overpressure x-fold

Contact mass consumption, 0.07 0.12

% per amount of ester,.

Saponification number 0.5-0.8 0.5-0.8

Iodine number 0.1 0.2

Hydrocarbon content 0.8 0.8

Example 2

In a continuously operating high pressure plant for the production of saturated fatty alcohols was over a usual tabletted (6 mm 0 of the table) Copper-zinc catalyst of the methyl ester of a first run fatty acid at 235 ° C and 250 atm. hydrogenated. the The chain distribution of the fatty acid was essentially:

C ₆ -FS 4% C ₈ -FS 63% C ₁₀ -FS 30.4% CrFS 1.1%

After separating the methanol from the hydrogenation product, the fatty alcohol is in a yield of 99% obtain. The clear fatty alcohol has the following key figures:

The starting material had a saponification number of 332, an iodine number of 1.5 and an acid number of 0.21. It a gas mixture of 140 NmVh hydrogen and 25 NmVh nitrogen was pumped around at a 15-fold molar excess of hydrogen and a maximum ester throughput of 40 l / h.

After separating off the methanol released during the reaction, the raw effluent had the following key figures:

Saponification number approx. 1,
OH number 397 (calculated 398.5),
Hydrocarbon content 0.8,
Iodine number: less than 0.15.

Example 3

In a continuously operating high-pressure system for the production of saturated fatty alcohols OH number

Iodine number

Saponification number

Hydrocarbon content

218 0.2 0.8 0.6%

Comparative experiment B

It was hydrogenated under the same conditions, but without additional nitrogen.

The results found are compared in Table II below.

Table Il

Way of working

with

nitrogen

(Invention)

Max. Amount of
methyl ester used, l / h

composition
Cycle gas

Hydrogen used, mVh

Molar excess hydrogen pressure v-fold

Contact mass consumption,% per
.- ,, amount of ester

Saponification number
Iodine number

M) hydrocarbon content

89H ₂ , ReStN ₂

250

0.15

0.5-0.8
0.2

0.6

without

nitrogen

(Comparison)

15th

99% H ₂ , balance N ₂

280

IK)

0.30

0.5-0.8 0.2

0.9

Claims (1)

Claim: Process for the continuous production of fatty alcohols by catalytic hydrogenation of higher molecular weight fatty acids, especially those formed with low molecular weight, monohydric alcohols Esters using an excess of hydrogen and over 50 atm. lying pressure and elevated temperatures and lumpy catalysts, characterized in that the hydrogenation with the addition of 3 to 30% by volume of inert gas, based on hydrogen, undertakes