EP2421812A1

EP2421812A1 - Method for preparing a terpenylcyclohexanol

Info

Publication number: EP2421812A1
Application number: EP10714297A
Authority: EP
Inventors: Roland Jacquot
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2009-04-22
Filing date: 2010-04-21
Publication date: 2012-02-29
Also published as: CN102421737A; JP2012524749A; US20120059196A1; CA2758475A1; WO2010122043A1; BRPI1007739A2; CN106518632A; FR2944789B1; FR2944789A1

Abstract

The present invention relates to a method for preparing a terpenylcyclohexanol using a terpenylphenol. The method according to the invention for preparing a terpenylcyclohexanol by the hydrogenation of a terpenylphenol is characterised in that the latter is hydrogenated in a liquid phase, in the presence of a Raney nickel catalyst including residual aluminium and doped with a mixture of iron and chromium.

Description

PROCESS FOR PREPARING TERPENYLCYCLOHEXANOL

The present invention relates to a process for preparing a terpenylcyclohexanol from a terpenylphenol.

Sandalwood oil is one of the oldest raw materials that because of its interesting olfactory properties has been widely used in perfumery. However, this natural product is excessively expensive and synthetic substitution products have been sought.

One of the first classes proposed is terpenylcyclohexanols. These are obtained by condensation of a phenol and camphene, in the presence of a Lewis acid catalyst followed by hydrogenation of the aromatic ring to give cyclohexanol.

Various methods involving this type of reaction are described in the literature.

US Pat. No. 4,061,686, which describes the condensation of pyrocatechol or 1,2-hydroxybenzene and of camphene, in the presence of a Friedel-Crafts catalyst, leads to an intermediate product which is a mixture of terpenylpyrocatechols, the majority product of which is to the following formula:

Hydrogenation of the complex mixture obtained using a conventional Raney nickel catalyst results in an odoriferous mixture of many isomers. The two main isomers correspond to the following formulas

The hydrogenation reaction is conducted at an elevated temperature of between 200 ^° C. and 300 ^° C., preferably between 225 ° C. and 250 ^° C., under a hydrogen pressure of between 200 and 250 bar.

The amount of catalyst used represents from 3 to 20% of the weight of the product of the reaction between catechol and camphene.

The hydrogenation conditions described in US 4,061,686 are relatively extreme and therefore difficult to implement on an industrial scale.

Furthermore, the amount of catalyst to implement is important since Example 9 indicates the use of 30 g of Raney nickel for the hydrogenation of 350 g of substrate.

The Applicant proposes to provide a more interesting process from an economic point of view.

One of the objectives of the present invention is to improve the hydrogenation conditions in particular, to conduct the reaction at a lower temperature.

Another object of the invention is to implement a lesser amount of catalyst.

It has now been found and this is the object of the present invention, a process for the preparation of a terpenylcyclohexanol by hydrogenation of a terpenylphenol, characterized in that the hydrogenation of the latter is carried out in liquid phase, in the presence of a Raney nickel catalyst comprising residual aluminum and doped with a mixture of iron and chromium.

According to the process of the invention, it has been found that the use of the catalyst as defined according to the invention makes it possible to carry out the hydrogenation reaction at a lower temperature and that the amount of catalyst used can be decreased without degrading the olfactory quality of the mixture obtained. The process of the invention is particularly applicable to substrates corresponding to the following general formula:

in said formula: - Y represents:

- a hydrogen atom

an OH group,

a group OR in which R represents a linear or branched alkyl group having from 1 to 4 carbon atoms, T represents a bicyclic terpenyl group comprising 10 carbon atoms.

According to a preferred embodiment of the invention, the terpenylcyclohexanol used corresponds to formula (I) in which Y represents an OH group, a group OR in which R represents a methyl or ethyl group.

For the terpenyl T group, it represents one of the following groups, alone or in mixture: bornyl group, isobornyl, camphyl, isocamphyl, fenchyl, isofenyl. In fact, the starting terpenyl phenol is a mixture of isomers of position and isomers of terpenyl so that the hydrogenated product obtained is also a mixture of isomers.

So called "terpenylphenol", the mixture of isomers bornylphenol, isobornylphenol, camphylphenol, isocamphylphenol, fenchylphenol, isofenchylphenol. These terpenyl groups can be found on all the free positions of the aromatic ring.

The proportion of different isomers depends on the nature of the starting substrate and the conditions of the preparation of terpenylphenol.

A terpenylphenol which can be prepared according to the various processes described in the literature is involved in the process of the invention.

This is a condensation reaction of phenol and camphene in the presence of a Friedel-Crafts catalyst.

As examples of catalysts that may be used, mention may be made, inter alia, of boron trifluoride, a metal halide, for example for example, aluminum trichloride, ferric chloride, zinc chloride; sulfuric acid, zeolites and clays.

A catalyst suitable for the reaction is boron trifluoride.

Since the latter is a gas, it is preferred according to the invention to use complexes of boron trifluoride comprising between 20 and 70% by weight of boron trifluoride.

As examples of complexes, there may be mentioned in particular the complexes comprising boron trifluoride combined with a solvent chosen from ethyl ether, acetic acid, acetonitrile and preferably phenol.

As regards the choice of a zeolite catalyst, preference is given to a zeolite having large pores. As preferred examples of zeolites, mention may be made more particularly of β-zeolites, Y-zeolites and mordenites, all in acid form. Another catalyst that is suitable for the condensation reaction is constituted by the group of clays and more particularly montmorillonites and in particular the clays sold by Sud-Chemie, such as clays K 10 and K 20.

Camphene reacted with phenol is a commercially available product. Generally, it is a mixture of camphene and tricyclene present at a content of not more than 10% of the weight of the mixture, and preferably at a content of not more than 7%.

The phenolic compound reacting with camphene preferentially responds to the following formula:

in said formula, Y has the meaning given for formula (I).

The ratio between the number of moles of phenol and the number of moles of camphene varies between 1 and 4 and is preferably between 1 and 2.

With regard to the amount of Lewis acid catalyst, the amount of catalyst depends on the catalyst selected.

When the catalyst is in the form of a salt or a complexed salt, the amount used may vary for example between 0.05 and 25 g per mole of phenolic compound and for a catalyst of the clay or zeolite type, the amount is from 0.1 to 1 g per mole of phenolic compound. The reaction can be conducted in the presence or absence of an organic solvent depending on the physical properties of the starting substrate.

The choice of the solvent is such that it must be inert under the reaction conditions of the invention. It must have the property of dissolving the starting phenolic substrate.

As nonlimiting examples of suitable solvents in this process step, mention may be made of aliphatic or cycloaliphatic hydrocarbons.

Examples of hydrocarbons that may be mentioned are aliphatic hydrocarbons and more particularly paraffins such as, in particular, cyclohexane.

As regards halogenated hydrocarbons, mention may be made more particularly of aliphatic or aromatic halogenated hydrocarbons, such as perchlorinated hydrocarbons such as in particular trichloromethane; partially chlorinated hydrocarbons such as dichloromethane, dichloroethane; monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene or mixtures of different chlorobenzenes,

The reaction between phenol and camphene is advantageously carried out at a temperature ranging between 20 ^° C. and 200 ^° C. and preferably between 20 ° C. and 180 ° C.

The process of the invention is generally carried out under atmospheric pressure but slightly above or below atmospheric pressures may also be suitable.

The reaction time may vary for example between 2 and 24 hours, preferably between 2 and 12 hours.

At the end of the reaction, the catalyst is removed by a solid / liquid separation technique, preferably by filtration when the catalyst is heterogeneous or by an aqueous hydrolysis operation followed by liquid / liquid decantation when the catalyst is homogeneous. After removal of the catalyst, the excess phenolic compound which can be recycled is distilled off and the distillation pellet is subjected to the hydrogenation step in accordance with the process of the invention.

Thus, in the hydrogenation step, a catalyst of Raney nickel type.

The Raney nickel conventionally used in the reduction reactions and in particular in the hydrogenation reactions is a catalyst generally prepared according to the mode described below. A nickel / aluminum alloy is prepared by melting a mixture comprising from 25 to 75% by weight of nickel and from 25 to 75% by weight of aluminum, but most often an equimassic weight ratio is preferred. The melting point is preferably chosen between 1100 ^° C. and 1700 ^° C.

The molten alloy is then solidified generally as ingots by casting into molds and cooling to room temperature (15 to 25 ° C).

In a following operation, the ingots are crushed and milled until the alloy is obtained in powder form.

A basic treatment is then carried out which allows the dissolution of a part of the aluminum and thus produces a porous microstructure

The catalyst obtained consists of agglomerates of nickel crystallites, having a large specific surface area and a residual content of variable aluminum.

The basic attack is preferably carried out using a concentrated solution of alkaline hydroxide, preferably sodium hydroxide (for example 20 to 30% by weight) and an excess of base; the base / alloy molar ratio expressed in Al being preferably between 1 and 1, 3. The operation is carried out at a temperature preferably chosen between

50 ⁰ C and 100 ⁰ C.

The catalyst is obtained in the form of an aqueous suspension powder and is separated from the aqueous phase which comprises the alkali aluminate. The catalyst is generally washed to remove excess base.

The doped Raney nickel according to the invention is prepared according to the method of preparation given above with the addition of iron and chromium dopants in the molten Ni-Al precursor alloy or at the same time as nickel and aluminum. It is a metallurgical doping.

The quantity of dopants used is such that a catalyst having the compositions defined below is obtained.

The catalyst involved in the process of the invention advantageously comprises: from 1 to 5% by weight of chromium

from 1 to 5% by mass of iron

from 5 to 10% by weight of aluminum

from 80 to 93% by weight of nickel The catalyst preferably used in the process of the invention comprises:

from 1.5 to 3% by weight of chromium

from 1 to 4% by weight of iron, from 5 to 7% by weight of aluminum

- from 86 to 92.5% by weight of nickel

The catalyst of the invention having the composition as defined is most often in the form of a fine powder having a particle size measured by sieving ranging from 10 to 40 microns. The catalyst being a pyrophoric catalyst, it is stored and introduced into the reaction in the form of a basic aqueous suspension having a pH of between 9 and 11 and a concentration ranging between 30 and 50% by weight.

According to the process of the invention, the hydrogenation of terpenylphenol is carried out in the presence of a Raney nickel catalyst as defined. The amount of hydrogenation catalyst used, expressed as the ratio between the mass of metal and the mass of compound of formula (I) can vary, for example, between 1 and 10% by weight, preferably between 1 and 5 % and even more preferably between 1 and 3% by weight.

The reaction is preferably conducted in bulk but it is not excluded to implement an organic solvent when the medium is difficult to manipulate. Examples of solvents include alcohols such as isopropanol.

The process of the invention is carried out at a temperature chosen from a temperature range of 180 ^° C. and 250 ^° C. and more particularly between 190 ° C. and 220 ° C.

The reaction is carried out under hydrogen pressure ranging from a pressure slightly above atmospheric pressure to a pressure of several tens of bars. Advantageously, the hydrogen pressure varies between 18 and 30 bar, and more preferably between 20 and 25 bar. At the end of the reaction, a mixture of isomers of terpenylcyclohexanol is obtained, corresponding to the following formula:

in said formula: Y 'represents a hydrogen atom when Y represents a hydrogen atom,

Y 'represents a hydrogen atom when Y is a group OR,

Y 'represents an OH group when Y is an OH group. When Y is a group OR, hydrogenation according to the process of the invention occurs during the operation, also an alcoholysis reaction which corresponds to the formation of a ROH alcohol which must be eliminated during hydrogenation by continuous or sequential purges. In practice, it is possible to implement the process according to the invention by introducing into a stainless steel autoclave the compound of formula (I), the catalyst, and the solvent (water), then, after the usual purges, by feeding the autoclave with adequate hydrogen pressure; the contents of the autoclave are then stirred at the proper temperature until the absorption ceases. When hydrogen consumption ceases, the reactor is purged to remove water and / or alcohol formed during the hydrogenation reaction. The pressure in the autoclave can be kept constant during the reaction time by successive purges to remove a light alcohol if it has formed. At the end of the reaction, the autoclave is cooled and degassed.

The reaction mixture is then treated in a conventional manner to recover terpenylcyclohexanol.

For this purpose, it is possible to add an amount of an organic solvent, preferably a low molecular weight alcohol, for example isopropanol, in order to fluidify the reaction mixture.

Then, the catalyst is separated according to standard solid / liquid separation techniques, preferably by filtration, and terpenylcyclohexanol is recovered from the filtrate, in particular by distillation.

Examples of embodiments of the invention given below are given by way of non-limiting illustration.

In the examples, the transformation rate of terpenylguaiacol is defined as the ratio between the number of moles of terpenylguaiacol converted and the number of moles of terpenylguaiacol used. Example 1

1. Preparation of terpenyl qaacol.

In a stirred stainless steel reactor of 2 liters, 751 g of gaiacol and 441 g of molten camphene are successively introduced. Stir and obtain a solution.

11 g of K10 clay from Sud-Chemie are then added.

The medium immediately turns brown and is gradually heated to 150 ^° C.

It is maintained under these conditions for 3 hours. Under these conditions, all the camphene or its isomers are no longer detected by gas chromatography (GC).

The temperature is then reduced to 60 ^° C. and the reaction medium is filtered through a bed of Celite (diatomaceous earth) to remove the catalyst.

The filtrate is then charged into a 2 liter boiler and distilled at about 100 ° C., under reduced pressure of 20 mbar of mercury, the guaiacol placed in excess.

682 g of a complex mixture of isomers of terpenylguaiacol as defined above, ie a mixture of isomers isobenzyl, isobornyl, camphyl-, isocamphyl-, fenchyl-, isoferyl-guaiacol, are then obtained. 2. Hydrogenation of terpenyl qaacol.

In a 750 ml stainless steel autoclave, 268 g of terpenylguaiacol and 2.9 g of a Raney nickel catalyst comprising 1.6% by weight of chromium, 1.0% by weight of iron, 5% are introduced. 5% by weight of aluminum: the balance being nickel. The reactor is then purged with nitrogen and hydrogen.

The reactor is then pressurized under 20 bar of hydrogen, stirred and heated gradually to 200 ^° C.

At this temperature, the reactor skies are purged to remove the water introduced with the Raney nickel catalyst. The reactor is pressurized again under 20 bar of hydrogen and the hydrogenation is carried out by keeping the pressure in the reactor constant (20 bar).

Periodically, as the rate of hydrogenation decreases, the hydrogen supply is cut off and the reactor is purged to remove the methanol and lighters formed in the reaction.

During the reaction, 6 purges are performed and the total duration of the hydrogenation is 6 hours. When it is found by GPC that all the terpenylguaiacol reacted, the heating is turned off and the reactor is purged with nitrogen. Thus, 100% terpenylguaiacol was transformed.

The temperature is brought to 60 ^° C. and 50 ml of isopropanol are introduced to reduce the viscosity.

The reaction medium is then filtered through Celite to remove the catalyst.

After distillation at 135-165 ° C. under reduced pressure of 2 mbar of mercury, 212 g of a complex mixture of isomers of terpenylcyclohexanol (mixture of isomers isobutyl, isobornyl, camphyl-, isocamyl-, fenchyl- , isofenchylcyclohexanol) which is compliant in olfactory quality.

The terpenyl unit is not isomerized during the hydrogenation.

Comparative Example 2 The hydrogenation is carried out as in Example 1 but using the catalyst marketed by the company DEGUSSA BK111W doped with molybdenum and containing less than 6.5% by weight of aluminum.

Using 2.9 g of this catalyst and after 12 purges and 12 hours of hydrogenation, it is noted that only 45% of committed terpenylguaiacol were converted into expected products.

Comparative Example 3

The hydrogenation is carried out as in Example 1 but using the catalyst marketed by ACTIVATED METAL A 5000 containing 7% aluminum and 0.16% iron.

With 2.9 g of this catalyst and after 12 purges and 12 hours of hydrogenation, it is noted that only 38% of terpenylguaiacol committed were converted into expected products.

Claims

1 - Process for the preparation of a terpenylcyclohexanol by hydrogenation of a terpenylphenol, characterized in that the hydrogenation of the latter is carried out in the liquid phase, in the presence of a Raney nickel-type catalyst comprising aluminum residual and doped with a mixture of iron and chromium.

2 - Process according to claim 1, characterized in that the terpenylphenol corresponds to the following general formula:

in said formula:

Y represents:

a hydrogen atom - an OH group,

a group OR in which R represents a linear or branched alkyl group having from 1 to 4 carbon atoms,

T represents a bicyclic terpenyl group comprising 10 carbon atoms.

3 - Process according to claim 2, characterized in that the terpenylphenol corresponds to the formula (I) wherein Y represents an OH group, a group OR in which R represents a methyl or ethyl group.

4 - Process according to claim 2, characterized in that the terpenylphenol corresponds to the formula (I) wherein T represents one of the following groups, alone or in mixture: bornyl group, isobornyl, camphyl, isocamphyl, fenchyl, isofenyl .

5 - Process according to claim 2, characterized in that the terpenylphenol corresponding to formula (I) is terpenylguaiacol.

6 - Process according to one of claims 1 to 5, characterized in that the Raney nickel type catalyst comprises: from 1 to 5% by weight of chromium

from 1 to 5% by mass of iron

from 5 to 10% by weight of aluminum

from 80 to 93% by weight of nickel

7 - Process according to claim 6, characterized in that the Raney nickel type catalyst comprises:

from 1.5 to 3% by weight of chromium

from 1 to 4% by weight of iron, from 5 to 7% by weight of aluminum

- from 86 to 92.5% by weight of nickel

8 - Process according to one of claims 1 to 7, characterized in that the catalyst is introduced into the reaction in the form of a basic aqueous suspension having a pH of between 9 and 11 and a concentration ranging between 30 and 50% in mass.

9 - Process according to one of claims 1 to 8, characterized in that the amount of hydrogenation catalyst used, expressed by the ratio between the mass of metal and the mass of compound of formula (I) varies between 1 and 10% by weight preferably between 1 and 5% and even more preferably between 1 and 3% by weight.

10 - Process according to one of claims 1 to 9, characterized in that the hydrogenation reaction is conducted at a temperature selected between

180 ⁰ C and 250 ⁰ C and preferably between 190 ° C and 220 ⁰ C.

11 - Process according to one of claims 1 to 10, characterized in that the hydrogen pressure varies between 18 and 30 bar, and preferably between 20 and 25 bar.

12 - Process according to one of claims 1 to 11, characterized in that an alcohol ROH formed during the hydrogenation reaction of a terpenylphenol corresponding to the formula (I) in which Y represents a OR group.