Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By contact with solid sorbent
Reexamination Certificate
2000-06-28
2001-12-11
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By contact with solid sorbent
C585S827000, C585S831000, C208S31000R
Reexamination Certificate
active
06329562
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for separating off cycloal-kadienes and cyclopolyenes from the reaction mixture formed during the metathesis of cycloalkenes using zeolites, wherein the cyclopolyenes have at least two double bonds.
BACKGROUND OF THE INVENTION
Macrocyclic alkenes having 8 to 20 carbon atoms can be used as intermediates for the preparation of fragrances. 14- to 17-membered cycloalkadienes are used in particular as starting materials for the preparation of musk fragrances. Cyclohexadecenone can be prepared from cyclohexadeca-1,9-diene (S. Warwel, H. Bachem, N. Döring, H. Kätker, E. Rose in Seife-Öle-Fette-Wachse 115, 538 (1989)). In general, it is necessary for the starting compounds to be virtually free from impurities.
Cycloalkadienes are usually obtained by metathesis of corres-ponding cyclomonoenes. By way of example, metatheses, which may be mentioned are those described in U.S. Pat. No. 3,935,270, Brit. Pat. No. 1,105,565, Brit. Pat. No. 1,118,517, EP 182 333, and also Warwel, H. Ridder, G. Hachen in Chemiker-Ztg. 107, 115 (1983).
A disadvantage of these processes is the large amount of solvent, which has to be used to ensure high selectivity for desired cycloal-kadienes. The known isolation processes are saddled with high-energy costs and are therefore expensive. Isolation is usually carried out by means of distillation.
The metathesis of cyclooctene or cyclopolyoctenylenes to give cyclohexadecadiene is carried out as described, for example, in EP 182 333 and EP 343 437. In the liquid phase, the mixture of starting materials is brought into contact with the heterogeneous catalyst system Re
2
O
7
/gamma-Al
2
O
3
in the presence of a tetraalkyltin.
The reaction is preferably carried out at temperatures of from 20 to 60° C. and using from 0.01 to 0.05 molar solutions. The contact time on the catalyst is typically from 25 to 200 seconds. The molar concentration of the solutions, which is given, refers to the calculated cyclomonoene units, which result from the division of the cyclopolyenes into monomers.
In the process described above, cyclooctene or a cyclooctene/cyclopolyoctenylene mixture produces a reaction mixture, which essentially comprises cyclohexadecadiene, cyclotetracosatriene, cyclodotriacontatetraene, cyclotetracontapentaene and cyclooctatetracontahexaene. The proportion of cyclohexadecadiene is generally in the range from 20 to 50%, preferably from 25 to 35%.
In the same process, cyclooctene and cycloheptene produce a reaction mixture, which comprises cyclotetradeca-1,8-diene, cyclopenta-1,8-diene and cyclohexadeca-1,9-diene, and higher macrocyclic cyclopolyenes. The proportion of dienes is generally in the range from 20 to 50% preferably from 25 to 40%.
The reaction mixture is usually in the form of a solution in metathesis inert solvents.
In the above-process, the preferred solvents here are unbranched or cyclic hydrocarbons. The unbranched are compounds having from 5 to 12 carbon atoms, preferably from 5 to 8 carbon atoms, for example n-pentane and n-hexane. The cyclic hydrocarbons are compounds having from 5 to 8 carbon atoms, preferably from 5 to 6 carbon atoms, for example cyclohexane.
It is known that crystalline aluminum silicates (zeolites) can be used for separating hydrocarbons. Thus, for example, U.S. Pat. No. 3,668,730 describes large-pored zeolites for separating xylenes. In U.S. Pat. No. 4,313,014, such zeolites are used for separating off cyclohexenes.
SUMMARY OF THE INVENTION
We have now found a process for separating off cycloalkenes having at least two double bonds from a reaction mixture in hydrocarbon solution formed during the metathesis of cycloalkamonoenes or cyclomonoene/cyclopolyene mixtures. The process is characterized in that the reaction mixture is treated with zeolites in the liquid phase, the olefins having at least two double bonds present in the solution are adsorbed by the zeolite, the laden zeolite is separated off, and cycloalkadienes and cyclopolyenes are obtained by desorption.
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, it has been found that adsorbents of the faujasite type, such as, for example, the zeolites of type X and Y in the alkali metal and alkaline earth metal form, are very suitable adsorbents for macrocyclic compounds which have a critical diameter which is much larger than the pore opening of these zeolites.
The cycloalkadienes or cyclopolyenes contain at least 8 carbon atoms in the ring, preference being given to ring sizes with more than 11 carbon atoms.
Furthermore, it has been found that said zeolites affect selective adsorption of the cycloalkadienes. From the above-described product mixtures of the metathesis of cyclooctene and cyclopolyoctenylenes, it is possible to achieve a stepwise depletion of the dienes from the crude solution. Here, depletion in the solution takes place in the order cis,cis-cyclohexadeca-1,9-diene, followed by cis,trans-cyclohexadeca-1,9-diene. The trans,trans-cyclohexadeca-1,9-diene remains in the solution the longest and becomes concentrated therein. cis,cis-Cyclohexadeca-1,9-diene can be separated off from very dilute solutions using aluminum silicates of the X an d Y type e in the sodium or a ammonium form. The adsorption is particularly gentle and efficient on exposure to ultrasound waves.
Amorphous adsorbents, such as, for example, silica gels of varying grain size and porosity, basic, acidic or neutral aluminum oxides and also noncrystalline aluminum silicates of varying compositions did not effect the desired adsorption.
Type X aluminum silicates are zeolites which have a faujasite crystalline structure. These well-known zeolites can be described using the following formula:
M
2
OAl
2
O
3
xSiO
2
yH
2
O
n: valency of the metal M
x: a number between 2 and 3
y: water of crystallization
Any type X aluminum silicate can be used, and these materials are commercially available.
Type Y aluminum silicates are zeolites which have a faujasite crystalline structure. These well known zeolites can be described using the following formula:
M
2
OAl
2
O
3
xSiO
2
yH
2
O
n: valency of the metal M
x: a number between 3 and 6
y: water of crystallization
Any type Y aluminum silicate can be used, and these materials are commercially available.
Prior to carrying out the adsorption, the water of crystallization must be removed from the zeolites. At temperatures between 150 and 650° C., optionally under reduced pressure, the majority of the water is removed from the zeolite. If this activation is carried out at lower temperatures, only partial dehydration takes place and the loading capacity of the adsorbent is reduced.
Zeolites for the process according to the present invention are large-pored zeolites of type X or Y, which can comprise any type of metal cation. Some of the cations can also be replaced for protons or ammonium ions. The pure H form of the Y zeolite has high catalytic activity which, at elevated temperature, can lead to isomerization of double bonds and carbon backbone. It is likewise possible for two or more different metal ions to be replaced. Preference is given to cations of main groups I and II of the Periodic Table of the Elements. Particular preference is given to the sodium and calcium forms.
The zeolites can be in the form of powders, spheres, rods, cylinders, extruded bars or in other moldings.
The adsorption of the cycloalkadienes and cyclopolyenes from the reaction mixture onto the zeolite takes place at temperatures in the range from 0 to 150° C., preferably in the range from 40 to 100° C.
Adsorption according to the process of the present invention generally requires from 15 minutes to 8 hours, preferably from 1 to 4 hours.
According to the present invention, from 5 to 50 parts by weight, preferably from 10 to 25 parts by weight, of zeolite are used, based on 1 part by weight of cycloalkenes.
The desorption generally takes place using a compound which is chemically and thermally stable under desorption conditions. It must be possible to separate off and recover this low-cost chemical from the extract in sufficient
Schick Peter-Reinhard
Wöhrle Ingo
Cheung Noland J.
Gil Joseph C.
Griffin Walter D.
Haarmann & Reimer GmbH
Nguyen Tam M.
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