Continuous process of producing fatty alcohols

An improved continuous process of producing fatty alcohols by a catalytic hydrogenation of fatty acids wherein hydrogen is fed and distributed into the annular space through nozzles which are specially designed to effect a pressure loss of 15 to 30 bars is disclosed. Guide tubes having specific dimensions are disposed above said nozzles. The feedstock to be treated and the catalyst dispersion are fed separately. The new process results in milder conditions for the catalyst and in a higher throughput rate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a continuous process of producing fatty alcohols 
by a catalytic hydrogenation of fatty acids or fatty acid derivatives at 
temperatures of 240.degree. to 330.degree. C. and pressures of 200 to 700 
bars in the presence of copper-chromium oxide catalysts, which may be 
modified by additional components, comprising feeding the feedstock to be 
hydrogenated into a high pressure chamber, feeding hydrogen and feeding a 
dispersion of the catalyst into said high pressure chamber equipped with a 
return pipe, thoroughly mixing the ingredients, causing the reaction to 
take place in the presence of a large quantity of material which has been 
almost completely or completely reacted, withdrawing the surplus hydrogen 
and recycling it to the high pressure chamber, and withdrawing the 
reaction product. 
A thorough mixing and an intense exchange of material are desired in such 
process, also a high yield of hydrogenated product and a useful life of 
the catalyst which is used. 
2. Discussion of the Prior Art 
In an attempt to meet these requirements it has been proposed to produce 
fatty alcohols continuously by a catalytic hydrogenation of fatty acid or 
fatty acid derivatives at temperatures of 240.degree. to 330.degree. C. 
and pressures of 200 to 700 bars in the presence of copper-chromium oxide 
catalysts, which may be modified by additional components, wherein the 
feedstock to be hydrogenated is continuously fed into a high pressure 
chamber, in which a large quantity of material which has been almost 
completely or completely reacted is thoroughly mixed with the catalyst and 
the hydrogen (German Pat. No. 1,112,056; U.S. Pat. No. 3,180,898). 
In the known process, it is usual to carry out the reaction in a high 
pressure reactor, in which a return pipe for recycling the completely 
reacted material is disposed suitably in a central position. Hydrogen is 
fed and distributed at the lower end of the reactor. The hydrogen supplied 
in a surplus produces a mammoth pump effect, which causes the 
catalyst-containing fatty alcohol to rise. When the hydrogen has been 
separated, the fatty alcohol returns through the return pipe into the 
lower part (section) of the reactor. Generally, the "lower part" is a part 
from the bottom of the reactor, which is generally vertical and 
cylindrical, up to a point one-third of the vessel's height, preferably up 
to no higher from the bottom than one diameter of the vessel. In order to 
ensure that the mammoth pump action will be as effective as possible, the 
upper part (section) of the reactor is provided with suitable means for 
separating the hydrogen as effectively as possible so that the effect of 
entrained hydrogen bubbles to decrease the velocity of the return flow is 
minimized. A catalyst, which is usually mixed with fatty alcohol to form a 
dispersion, is also fed at the required rate into the reactor cycle. The 
acid is distributed as uniformly as possible at the lower end of the 
reactor and mixes with the circulating reaction mixture. The ratio of 
feedstock to circulating reaction mixture should be at least 1:10, 
preferably 1:100 to 1:1000. The resulting mixing will result in only a 
slight damage to the catalyst. Because the fatty acid is mixed with 
virtually completely reacted material and owing to the presence of surplus 
hydrogen, which is supplied to the high pressure chamber at a rate which 
is at least 3 times and suitably 10 to 50 times higher than the rate at 
which hydrogen is consumed, the fatty acid is rapidly diluted and is most 
effectively esterified with completely reacted material, consisting mainly 
of fatty alcohol. The resultant fatty acid-fatty alcohol ester does not 
attack the catalyst and is hydrogenated in the reaction chamber to form 
fatty alcohol. Surplus hydrogen leaves the reactor at its top jointly with 
the reacton water, the fatty alcohol and the catalyst at a rate which 
depends on the feed rates of fatty acid and catalyst dispersion. 
It is an object of the invention to improve the mixing of the circulating 
material with the fatty acid feedstock so that the attack of acid on the 
catalyst will be further decreased and the catalyst will be damaged less 
than even in the process described above. Additionally, it is an object to 
increase the throughput and/or decrease the catalyst consumption. 
SUMMARY OF THE INVENTION 
This object is accomplished according to the invention that hydrogen is 
introduced and distributed into the high pressure chamber through 4 to 10 
nozzles, which are disposed in the lower part (section) of the annular 
chamber and are so dimensioned that the pressure loss therein amounts to 5 
to 50 bars, preferably 15 to 30 bars, guide tubes are provided above the 
nozzles and are dimensioned that the total cross-sectional area of these 
guide tubes amounts to 70 to 150% of the cross-section of the return pipe, 
the nozzles are disposed centrally under the guide tubes at a distance 
therefrom which is one-half to twice the diameter of the guide tube, the 
height of each guide tube is 3 to 10 times, preferably 5 times, the 
diameter of the guide tube, the lower end of each guide tube is 
approximately level with the lower end or disposed up to three guide tube 
diameters above the lower end of the return pipe, and the feedstock to be 
hydrogenated and the catalyst dispersion are fed above the nozzles 
employed for hydrogen introduction. 
According to a preferred further feature of the invention, the feedstock to 
be hydrogenated is fed on a level within a range between about one-half 
guide tube diameter below the lower end of a guide tube and about one 
guide tube diameter above the lower end of a guide tube and the feedstock 
is distributed to the several guide tubes. 
According to a further preferred feature of the invention, the nozzles for 
feeding the hydrogen are disposed centrally under respective guide tubes 
at a distance of one-half to two guide tube diameters. 
According to another preferred feature of the invention, the catalyst is 
fed to a guide tube like the feedstock to be hydrogenated. In that case, 
no fatty acid is desirably fed to that guide tube or those guide tubes, 
not exceeding two, in which the catalyst is mixed so that the catalyst can 
be activated by surplus hydrogen in a state of high turbulence. 
The advantages afforded by the invention reside particularly in that a 
simple and economical process is provided by which fatty acids and their 
derivatives can be reduced to fatty alcohols. The process is entirely 
continuous. The catalyst is treated gently and the end product is obtained 
in a high yield. 
Because the hydrogen is distributed by properly designed and arranged 
nozzles and fed at a high velocity, a thorough mixing of the reactants and 
an intense mass transfer between them are effected. There will even be a 
return flow in the annular space outside the guide tubes so that the flow 
in the guide tubes will be particularly large particularly because the 
velocity of the reaction material flowing down in the return pipe is not 
decreased but even increased by the measures which have been described. 
All measures together result in an instantaneous mixing in a very small 
space in the presence of highly turbulent hydrogen.

DESCRIPTION OF SPECIFIC EMBODIMENT 
Referring to the drawing, there is shown a high pressure chamber 1, a 
return pipe 2, guide tubes 3, an annular space 4, means 5 for supplying 
hydrogen, nozzles 6, means 7 for supplying the feedstock to be 
hydrogenated, means 8 for supplying catalyst dispersion, means 9 for 
withdrawing hydrogenated product and means 10 for recycling surplus 
hydrogen.