Patent Application
20060149093
The present invention relates to a process for separating a hydroxybenzonitrile type compound obtained by means of an amination/dehydration process. More particularly, it relates to 2-hydroxybenzonitrile, also known as 2-cyanophenol. The invention also relates to a process for separating and purifying a hydroxybenzonitrile type compound contained in a gaseous reaction stream.
Hydroxybenzonitriles are products of major industrial interest as they are used as colorants and as intermediates in the preparation of active ingredients such as herbicides, fungicides and insecticides.
One route to obtaining hydroxybenzonitriles consists of aminating an alkyl hydroxybenzoate followed by dehydration.
More particularly, German patent DE-A-2 020 866 describes a process for preparing 4-hydroxybenzonitrile in the gas phase by reacting ammonia and the methyl ester of 4-hydroxybenzoic acid in the presence of a catalyst, namely phosphoric acid deposited on a support such as silica gel.
A process of the same type has been described in French patent FR-A-2 332 261 and Canadian patent CA-A-2 177 939, except that the catalyst is respectively boron phosphate or boron phosphate doped with a transition metal from group Va, VIa, IIb, IIIb of the periodic table published in the Bulletin de la Societe Chimique de France, no 1 (1966).
The problem when separating the hydroxybenzonitrile type compound obtained using that type of process, which consists of reacting methyl 2-hydroxybenzoate and ammonia in the gas phase in the presence of a dehydration catalyst, is that difficulties arise because the product obtained solidifies as soon as it condenses, which makes isolation difficult.
Other difficulties reside in the formation of by-products due to two types of secondary reactions.
The higher the temperature of the reaction medium, the faster the product obtained trimerizes to S-triazine. It has been found that from 140° C., trimerization is immediate and exhibits an auto-catalytic nature.
A further type of secondary reaction that occurs is hydrolysis of the 2-hydroxybenzonitrile obtained to 2-hydroxybenzamide due to the water liberated during preparation of the 2-hydroxybenzonitrile, which reaction is accentuated by the presence of ammonia.
Thus, there is a genuine industrial problem in obtaining 2-hydroxybenzonitrile from the gaseous reaction stream containing it.
We have now discovered, and this constitutes the subject matter of the present invention, a process for separating a hydroxybenzonitrile type compound from a gaseous reaction stream containing it either completely or partially in the form of an ammonium salt, characterized in that it consists, with the aim of obtaining a hydroxybenzonitrile type compound, of displacing the ammonium ions:
The term “hydroxybenzonitrile type compound” as used throughout the description of the present invention means an aromatic compound carrying at least one hydroxyl group and a nitrile group and/or the hydrated form of said compound, i.e., the nitrile group is completely or partially replaced by an amide group.
In accordance with a first implementation of the present invention, the ammonium ions are displaced using a physical treatment, more precisely a heat treatment.
In accordance with a second implementation of the present invention, the ammonium ions are displaced using a chemical treatment, more precisely an acid treatment.
It has been discovered that the hydroxybenzonitrile type compound is present in the gaseous reaction stream in a form in which the OH group is in the salt form, i.e., it is in the form of the ammonium salt, and that the free OH content represents less than 10 mole %, preferably less than 5 mole %.
In order to separate the hydroxybenzonitrile type compound, it has been discovered that the ammonium ions have to be displaced.
At the end of the vapour phase reaction for preparing the hydroxybenzonitrile type compound by means of amination/dehydration of an alkyl hydroxybenzoate type compound, the gaseous reaction stream is at a high temperature, generally more than 200° C., preferably in the range 200° C. to 600° C., more preferably in the range 350° C. to 450° C.
In accordance with the process of the invention, it has been discovered that it is possible to obtain a benzonitrile type compound with a free OH group by heat treating a compound in the salt form without aiding secondary reactions such as trimerization and hydrolyzing the nitrile group.
In a first variation of the process of the invention, the gas stream is heat treated.
In a second variation, the process of the invention consists of liquefying the gaseous reaction stream then recovering the hydroxybenzonitrile type compound in its salt form as a solid from said stream and heat treating the solid product obtained either directly or after dissolving.
In a further variation, the process of the invention consists of liquefying the gaseous reaction stream then treating it with an acid resulting in the production of a 2-hydroxybenzonitrile type compound then recovering it in an organic phase which is separated out.
The process of the invention is applicable to any aromatic compound containing at least one aromatic ring containing 6 carbon atoms and carrying at least one nitrile group and an OH group which is completely or partially in its salt form.
The invention encompasses benzene rings, naphthalene rings or a concatenation of benzene rings separated by a covalent bond, an alkyl or alkylidene group containing 1 to 4 carbon atoms, or an atom (for example oxygen or a functional group such as CO).
More particularly, the invention concerns compounds that can be represented as follows:
in which formula R represents one or more substituents.
The hydroxybenzonitrile with formula (I) can carry one or more substituents provided that they do not interfere with the process of the invention.
The number of substituents present on the ring depends on the carbon condensation of the cycle and on the presence or otherwise of unsaturated bonds in the cycle.
The maximum number of substituents that can be carried by a cycle can readily be determined by the skilled person.
In the present text, the term “plurality” generally means less than 4 substituents on an aromatic nucleus.
Examples of substituents are given below; this list is not limiting in nature. The following can be cited:
The invention is of particular application to separating and purifying 4-hydroxybenzonitrile and 2-hydroxybenzonitrile.
In the following description of the present invention, for simplification, the process of the invention will be described in its application to the preparation of 2-hydroxybenzonitrile, but it can be applied to all of the compounds cited above.
In accordance with the process of the invention, we start from a gaseous reaction stream (F1) essentially comprising 2-hydroxybenzonitrile, either completely or partially in its salt form. This means that the quantity of 2-hydroxybenzonitrile expressed as a mole % with respect to the alkyl 2-hydroxybenzoate employed is at least 50%, preferably at least 75% and still more preferably in the range 80% to 95%.
The gas stream (F1) also comprises ammonia in an amount of 200 to 600 mole %, nitrogen in an amount of 5 to 200 mole %, the alcohol liberated by the starting ester, usually methanol in an amount of 50 to 100 mole %, and the water formed during the reaction, about 50 to 100%.
The gaseous reaction stream (F1) can optionally comprise 0 to 5 mole % of phenolic compounds, for example phenol, 0 to 5 mole % of starting hydroxybenzoate ester, and products resulting from secondary reactions such as hydrolysis or trimerization, in particular 0 to 10 mole % of 2-hydroxybenzamide optionally N-alkylated by the liberated alcohol, for example N-methyl-(2-hydroxybenzamide), and less than 3 mole % of S-triazine.
The different concentrations of the components of the stream are given by way of illustration and are in no way limiting in nature.
It should be noted that this reaction stream is essentially gaseous but the invention also encompasses the case of an aerosol, i.e., a portion of the gaseous stream may be condensed so that liquid particles are present, preferably in an amount of less than 10% by volume.
This gaseous reaction stream can derive from an alkyl hydroxybenzoate amination/dehydration reaction.
It can be represented by the following formula:
in which formula, R has the meaning given above in formula (I) and R1 generally represents an alkyl group containing 1 to 4 carbon atoms, preferably a methyl or ethyl group.
Preferred hydroxybenzoates that can be employed that can be cited are methyl 2-hydroxybenzoate, ethyl 2-hydroxybenzoate and ethyl 4-hydroxybenzoate. Preferably, methyl or ethyl 2-hydroxybenzoates are used.
Thus, the compound with formula (II) is reacted with ammonia in the vapour phase in the presence of a heterogeneous catalyst.
Examples of catalysts that can be cited are boron phosphate, optionally doped as mentioned in CA-A-2 177 939, or phosphoric acid deposited on a support which may be silica and/or alumina and/or titanium oxide. Preferably, a silica gel or kieselguhr type support is used; the phosphoric acid represents 50% to 75% by weight of the catalyst.
While the quantity of ammonia engaged can equal the theoretical quantity determined by the stoichiometry of the reaction (i.e., one mole of ammonia per mole of hydroxybenzoate), amination is preferably carried out using an excess of ammonia. In general, it is preferable to use at least two moles, more particularly 2 to 5 moles of ammonia per mole of hydroxybenzoate. The excess ammonia present in the gas stream resulting from the amination reaction can be recycled.
The apparent dwell time for the gas stream with the catalyst, defined as the time in seconds during which one unit volume of gas mixture (measured under normal temperature and pressure) is in contact with one apparent unit volume of catalyst, can be in the range 0.001 sec to 10 min, preferably in the range 0.01 sec to 2 min.
The reaction is generally carried out at atmospheric pressure, at a temperature of 200° C. to 600° C.; preferably, it is in the range 350° C. to 450° C.
At the end of the reaction, a gaseous reaction stream (F1) is obtained comprising light gases, ammonia, water and an alcohol deriving from the starting alkyl hydroxybenzoate (preferably methanol) and heavy gases, essentially 2-hydroxybenzonitrile, which is completely or partially in its salt form, and the by-products mentioned above.
The process of the invention, which can produce a hydroxybenzonitrile type compound with a free OH group from a benzonitrile type compound, completely or partially in the form of the ammonium salt, can also be applied to a benzonitrile type compound in the hydrated form, i.e., a hydroxybenzamide type compound with formula (I) in which the CN group is replaced by a CONH2 group, completely or partially in the ammonium salt form.
The scope of the present invention also encompasses applying the process of the invention to a hydroxybenzonitrile type compound in its hydrated form.
Said compound is obtained in a known manner by means of amination of an alkyl hydroxybenzoate type compound by reaction with ammonia in the presence of a conventional catalyst: glass beads, silica or silica-alumina.
In accordance with the process of the invention, it has been discovered that to separate 2-hydroxybenzonitrile from a gaseous reaction stream, the ammonium salt has to be displaced.
To this end, the temperature of the hot reaction stream is reduced to a temperature so that a liquid phase essentially comprising 2-hydroxybenzonitrile in its salt form is condensed, enabling decomposition of the ammonium salt leading to the liberation of ammonia.
In a first variation of the process of the invention, this operation is accomplished by bringing the gaseous reaction stream into contact with a solvent (organic solvent and/or water) then cooling the ensemble to a temperature below 200° C., preferably in the range 200° C. to 100° C., to obtain a liquid phase essentially comprising 2-hydroxybenzonitrile.
The gas stream is brought into the presence of a solvent (S1).
Several criteria govern the choice of solvent.
Firstly, the solvent has to be stable under the reaction conditions.
Secondly, the solvent must be vaporized in the selected temperature zone, i.e., its boiling point must be less than 250° C.
Advantageously, the solvent has a boiling point in the range 100° C. to 250° C., preferably in the range 100° C. to 200° C.
In a preferred variation, the solvent is selected that can also purify the 2-hydroxybenzonitrile obtained, by crystallization. Thus, it is a good solvent when hot but a poor solvent when cold, usually at ambient temperature, preferably in the range 15° C. to 25° C.
A polar or apolar solvent is used.
Examples of suitable solvents that can be cited are water, water/alcohol mixtures, for example methanol or ethanol; halogenated or non halogenated aromatic hydrocarbons, for example toluene, xylenes, ethylbenzene, monochlorobenzene; and ethers, for example anisole or 2-ethylhexanol.
When using water/alcohol mixtures, they generally contain less than 50% of alcohol, preferably 1% to 50%, more preferably 1% to 25% of alcohol and 50% to 99%, preferably 75% to 99% of water.
The quantity of solvent employed represents 30% to 500% of the weight of the gaseous reaction stream.
In practice, the hot gas stream is brought into contact with a co-current of the vaporized reaction solvent.
Light gases (F2) comprising ammonia, alcohol (usually methanol), water and in some cases an azeotropic water/organic solvent mixture are recovered, along with the heavy compounds (F3) essentially comprising 2-hydroxybenzonitrile and the solvent (organic solvent and/or water) and minor products such as phenolic compounds, for example phenol, the starting hydroxybenzoate ester, 2-hydroxybenzamide and possibly N-methyl-(2-hydroxybenzamide), and S-triazine.
The invention also concerns a process for separating and purifying 2-hydroxybenzonitrile.
The first step is carried out as described above and the heavy fraction (F3) essentially comprising 2-hydroxybenzonitrile and solvent is treated.
Purification is then carried out by distilling the products with the lower boiling points then distilling the 2-hydroxybenzonitrile.
The first fraction recovered between 20° C. and 40° C. at 0.4 mbars of pressure corresponds to the solvent.
The second fraction obtained between 40° C. and 110° C. at 0.4 mbars of pressure corresponds to phenol and the starting hydroxybenzoate.
The third fraction obtained at 110° C. under 0.4 mbars of pressure is constituted by 2-hydroxybenzonitrile.
The salicylamide, N-methylsalicylamide and S-triazine are recovered from the bottom.
The purity of the distilled 2-hydroxybenzonitrile is at least 95%, preferably at least 98%.
A further purification technique consists of crystallizing the 2-hydroxybenzonitrile then carrying out a solid/liquid separation of the crystallized product.
We start with the fraction (F3) from the separation step.
Then cooling to a temperature in the range 100° C. to −10° C., preferably in the range 10° C. to 0° C., causes the 2-hydroxybenzonitrile to crystallize.
The crystalline product is then separated using conventional solid/liquid separation techniques, preferably by filtration.
A solid is recovered that is essentially 2-hydroxybenzonitrile and a liquid phase (F6) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products.
The solid can be dried at a temperature in the range 30° C. to 80° C., preferably in the range 40° C. to 50° C.
The purity of the 2-hydroxybenzonitrile is very high, at over 90%, preferably more than 95%.
A further purification technique that can be employed is purification by refining.
We start from the fraction (F3) deriving from the separation step.
Firstly, it is cooled to a temperature in the range 100° C. to 30° C.
An aqueous phase (F7) and an organic phase (F8) are obtained that are separated after decanting.
The organic phase is essentially constituted by 2-hydroxybenzonitrile and solvent (S1).
The water and/or solvent is/are separated by distillation at a temperature of 90° C. to 100° C. and under a reduced pressure in the range 1 mbar to 1 bar.
A crude reaction mass is obtained that essentially comprises 2-hydroxybenzonitrile.
A refining purification operation is then carried out.
Refining is carried out discontinuously using apparatus that can carry out liquid/solid separation (dewatering, zone melting) and of a size that depends on the volume to be treated and on the number of devices employed. Further, the choice of type of apparatus is not critical. As an example, conventional draining sieves can be used, or other refining apparatus, for example those sold under the trade name PROAPT (registered trade mark). Vertical cylindrical tube exchanger type draining sieves could be used, for example.
The fraction (F9) is treated in one or more pieces of apparatus essentially by means of the following 4 phases:
The production of fractions with substantially constant compositions facilitates automisation of this refining step.
Fraction (F9) comprising 2-hydroxybenzonitrile is sent to one or more pieces of refining apparatus.
Prior to phase 1, the apparatus is heated above the melting point of 2-hydroxybenzonitrile (98° C.), for example to between 100° C. and 120° C.
During phase 1, the mass is cooled, for example to a temperature in the range 10° C. to 50° C., over several hours, for example 5 to 15 h, which induces slow crystallization of the charged mixture.
After phase 1, the product remains liquid and is removed from the apparatus (phase 2) before passing to phase 3.
Phase 3 consists of slowly reheating the refining apparatus, possibly commenced during phase 2, for example to a temperature in the range 94° C. to 98° C., over several hours, for example 8 to 15 h.
The end of phase 3, which determines the purity of the product, can be determined either by measuring the crystallization point or by any other physico-chemical analytical technique.
Phase 4 requires heating the apparatus to a temperature of over 95° C. to melt the 2-hydroxybenzonitrile which is extracted in the molten state (F11).
The eutectic fractions (F10) recovered during refining can be recycled as a mixture or separately with the hot dewatering, preferably to the preceding step.
2-hydroxybenzonitrile is obtained with a purity of at least 98%, preferably at least 99%.
In a further implementation of the invention, 2-hydroxybenzonitrile is separated from the gaseous reaction stream (F1) containing it in the salt form, in a variation of the process that comprises the steps of liquefaction of the gaseous reaction stream, crystallization of the 2-hydroxybenzonitrile as an ammonium salt hereinafter termed “ammonium cyanophenate”, solid/liquid separation of the crystallized product then heat treatment of the separated solid to liberate ammonia, water, and an alcohol (preferably methanol) and to recover the 2-hydroxybenzonitrile.
In a further variation, the invention consists of heat treating the ammonium cyanophenate not in the solid form, but heat treating the ammonium cyanophenate in solution in an organic solvent (S2).
The gaseous reaction stream is then liquefied and the ammonium cyanophenate is crystallized and solid/liquid separation is carried out then the solid product obtained is dissolved in an organic solvent, preferably a polar solvent and finally, the organic solution obtained is heat treated.
More precisely, the gaseous reaction stream (F1) is first liquefied by cooling from 90° C.-100° C. to a temperature of 40° C.-30° C. and bringing it into contact with water, which can eliminate the light products (ammonia and water) and recover an aqueous phase comprising ammonium cyanophenate and ammonia.
The quantity of water employed represents 50% to 100% by weight of (F1).
In the next step, in a first step, the ammonium cyanophenate is crystallized.
By cooling the liquefied stream (F12) to a temperature in the range 0° C.-30° C., the ammonium cyanophenate is caused to crystallize.
The crystalline product is then separated using conventional solid/liquid separation techniques, preferably by filtering.
Separation is carried out at a temperature in the range 0° C. to 20° C.
A solid is recovered that is essentially ammonium cyanophenate and a liquid phase (F13) comprising the solvent, a little of the 2-hydroxybenzonitrile (less than 5% by weight) and by-products.
The recovered product can be represented by formula (III):
in which formula, R has the meanings given above.
The heat treatment is then carried out at a temperature in the range 80° C. to 20° C., and at a pressure in the range 1 mbar to 1 bar, preferably between 1 mbar and 500 mbar.
A light fraction (F14) is eliminated which comprises ammonia and the solvent (S1), and 2-hydroxybenzonitrile is recovered as a solid.
In a further variation of the invention, the heat treatment is carried out on the ammonium cyanophenate which is dissolved in an organic solvent (S2).
Firstly, the solid ammonium cyanophenate obtained as described above is dissolved by liquefying the gaseous stream, crystallization and separation resulting in ammonium cyanophenate in the solid form and a liquid phase (F15).
The ammonium cyanophenate is dissolved by adding a polar aprotic solvent.
Examples of suitable solvents that can be mentioned are dimethylformamide and N-methylpyrrolidone.
Preferably, dimethylformamide is used.
The quantity of solvent employed represents 30% to 500% of the weight of the ammonium cyanophenate.
An organic solution of ammonium cyanophenate is obtained that is then heat treated at a temperature in the range 80° C. to 20° C. and at a pressure in the range 1 mbar to 1 bar, preferably between 1 mbar and 500 mbar.
A light fraction (F16) comprising ammonia and the solvent is eliminated and a fraction (F17) is recovered which is 2-hydroxybenzonitrile in solution in a solvent (S2), and it is possible to isolate it conventionally by distillation or by cooling in a flaker.
In a further implementation of the invention, the 2-hydroxybenzonitrile is separated from the gaseous reaction stream (F1) containing it in its salt form, by chemically displacing the ammonium ions.
This variation of the process consists of liquefying the gaseous reaction stream, treating it with an acid to obtain the 2-hydroxybenzonitrile, and carrying out liquid/liquid separation to recover the 2-hydroxybenzonitrile in the organic phase.
More precisely, firstly the gaseous reaction stream (F1) is liquefied by cooling from 90° C.-100° C. to a temperature of 40° C.-30° C. and bringing it into contact with water to eliminate the light compounds (ammonia and water) and to recover an aqueous phase comprising ammonium cyanophenate and ammonia.
The quantity of water employed represents 50% to 700% of the weight of (F1).
The ammonium ions are then neutralized using an acid.
A Brönsted acid with a pKa, measured in water, of less than 6, preferably in the range −1 to 4, is used.
More particular examples that can be cited are sulphuric acid, hydrochloric acid, phosphoric acid and acetic acid.
The concentration of the acid solution is immaterial: it can be between 30% and 100%.
The quantity of acid employed is such that the pH obtained is between 6 and 1, preferably between 4 and 3.
The neutralization operation is carried out at a temperature that is advantageously in the range 90° C. to 30° C.
The reaction mixture obtained is then decanted to separate an aqueous phase (F19) comprising excess acid and ammonium salts, from an organic phase (F20) comprising the 2-hydroxybenzonitrile.
This latter can be purified using purification techniques such as distillation, crystallization and refining, as described above.
The present invention also concerns facilities for carrying out the different variation of the process of the invention.
The present invention also concerns a facility for carrying out the process of the invention which comprises at least one unit for separating 2-hydroxybenzonitrile from a gaseous reaction stream and optionally, a 2-hydroxybenzonitrile purification unit.
The separation unit comprises:
The facility for separation comprises a first column (1) for ensuring good gas/liquid contact, for example a wash tower. It comprises means at the column head for admitting a gaseous reaction stream (F1) to be treated and means for admitting solvent (S1), for example a pump and a device (nozzles) for vaporizing the latter. In its lower portion, the column comprises means for evacuating a heavy phase (liquid and/or gas) connected to a second column (2) which is supplied at mid-height.
Column (2) for gas/liquid separation is a column comprising cooling means (condenser). Its upper portion is provided with means for withdrawing a gas phase comprising light compounds (F2) and means for withdrawing a liquid phase (F3).
In a preferred implementation of the invention, the facility comprises a separation unit and a purification unit.
The separation unit is completed by means ensuring purification of 2-hydroxybenzonitrile contained in the heavy fraction (F3) recovered at the outlet from the separation unit.
FIGS. 2 to 4 illustrate different means for carrying this out.
In a first preferred embodiment, which consists of carrying out the purification by distillation (
From this information, the skilled person will be capable of selecting the means to be employed as a function of the starting mixture. The following is simply an outline. The size (in particular the diameter) of the distillation columns depends on the circulating stream and on the internal pressure. They are dimensioned principally according to the flow rate of the mixture to be treated. The internal parameter, which is the number of theoretical stages, is determined in particular by the composition (ratios) of the entering mixture and the purity or composition of the mixture that should be obtained at the head and bottom of the distillation column. The columns can be packed with an ordered packing, as is known to the skilled person. Once the facility has been determined, the skilled person will adjust the operating parameters of the columns.
The distillation column (3) can advantageously, but not in a limiting fashion, be a column with the following specifications:
In a second embodiment, purification is accomplished by crystallization (
It is connected to a solid/liquid separation device (5) such as an aspirator, agitated filter, filter-press, or multi-tube filter.
It can recover a solid essentially constituted by 2-hydroxybenzonitrile and an aqueous phase (F6) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products.
The separation device (5) can optionally be associated with drying means (6) such as a rotary drier or an agitated drier, enabling the 2-hydroxybenzonitrile to be recovered in the form of a powder (P).
In a third embodiment (
It is connected to a liquid/liquid separation device (8) such as a settler.
It can separate an aqueous phase (F7) from an organic phase essentially constituted by 2-hydroxybenzonitrile (F8).
This organic phase is directed to a reactor (9) provided with stirring means at a temperature regulating device (hot/cold). It is surmounted by a distillation column and provided with a reduced pressurization system that can separate the organic solvent and/or remaining water by distillation (F9).
The organic phase (F8) is routed to an apparatus (10) for refining (dewatering, zone melting) and dimensioned as a function of the volume to be treated and their number. The choice of apparatus type is also not critical. It may, for example, be a conventional draining sieve or other refining apparatus, for example those sold under the trade name PROAPT (registered trade mark). As an example, it is possible to use draining sieves of the vertical cylindrical tube exchanger type.
Different fractions are recovered containing impurities (F10) and a 2-hydroxybenzonitrile fraction (F11).
In accordance with a further variation of the invention, ammonium cyanophenate rather than the gaseous reaction stream comprising 2-hydroxybenzonitrile is heat treated, and the process is carried out in a facility comprising the separation unit illustrated in
The facility shown in
In reactor (12) the ammonium cyanophenate is crystallized; it is provided with means for admitting the fraction (F12); said reactor is provided with agitation means and with a temperature regulating device (hot/cold).
In its lower portion it has a withdrawal device that can connect it to a solid/liquid separation device (13) such as an aspirator, agitated filter, filter-press or multi-tube filter.
It can recover a solid essentially constituted by ammonium cyanophenate and an aqueous phase (F13) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products.
The separation unit is associated with drying means (14) such as an agitated drier in which it undergoes a temperature and pressure cycle to decompose the solid ammonium cyanophenate to 2-hydroxybenzonitrile, allowing the 2-hydroxybenzonitrile to be recovered in the form of a powder (P) while eliminating the solvent and remaining ammonia (F14).
In a further variation shown in
Its lower portion comprises a withdrawal device that can connect it to a solid/liquid separation device (15) such as an aspirator, agitated filter, filter-press or multi-tube filter and is provided with a means for admitting a solvent (S2) to dissolve the ammonium cyanophenate.
It can recover the ammonium cyanophenate in an organic solution and an aqueous phase (F18) comprising the solvent (S1), a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products.
The mixture is sent to a reactor (16) provided with stirring means, a temperature regulating device (hot/cold) surmounted by a distillation column and provided with a reduced pressurization system to separate the organic solvent and/or remaining water (F16) and to carry out thermal decomposition of the ammonium cyanophenate to 2-hydroxybenzonitrile by the joint application of temperature and pressure.
(F17) is recovered, namely 2-hydroxybenzonitrile in solution in a solvent (S2) and it is possible to isolated it conventionally by distillation or by cooling on a flaker.
The separation unit shown in
This latter can be purified using purification techniques such as distillation, crystallization and refining illustrated in FIGS. 2 to 4.
The process of the invention can produce very pure 2-hydroxybenzonitrile.
The invention will now be described in more detail by means of implementations of the invention that are taken by way of non limiting example.
The crude reaction stream from a reactor comprising 0.52 moles of 2-hydroxybenzonitrile in its salt form (2-HBN) and 1.7 moles of ammonia (F1) was dissolved in 72 g of water at 60° C. in the wash tower (17).
The stream (F18) was then transferred to a stirred reactor (18) where 35.1 g of 98% sulphuric acid was added, keeping the temperature at 60° C.
The final pH had to be in the range 3 to 4 when sulphuric acid addition was complete.
The upper phase (F20), crude 2-hydroxybenzonitrile, was recovered after decanting at 60° C. in a settler (19).
The titer of the crude 2-hydroxybenzonitrile was 61% by weight.
The recovery yield was 96% (0.506 moles).
In the apparatus shown in
The following results were obtained:
In the apparatus shown in
The following results were obtained:
The crude reaction stream from a reactor comprising 0.52 moles of 2-hydroxybenzonitrile in its salt form (2-HBN) and 1.7 moles of ammonia (F1) was dissolved in 216 g of water at 60° C. in the wash tower (11).
The stream was charged into a reactor (12) where it underwent cooling to 15° C.
The precipitated ammonium 2-cyanophenate was recovered by filtering in a filter (15) where it was washed with 50 g of 5% by weight ammonia.
The precipitate was drained then re-dissolved in the filter in 70 g of dimethylformamide.
The ammonium 2-cyanophenate solution in dimethylformamide was transferred to reactor (16) where the water then the ammonia were eliminated by heating to 60° C. at 100-50 mbars.
The isolation yield of the 2-hydroxybenzonitrile was 72% and the purity (ex DMF) of the 2-hydroxybenzonitrile was 99.5%.
The crude reaction stream from a reactor comprising 0.52 moles of 2-hydroxybenzonitrile in its salt form (2-HBN) and 1.7 moles of ammonia (F1) at 420° C. was brought into contact with in 200 g of xylene at in the wash tower (1).
The stream was then transferred to a column (2) where the mixture was cooled to 110° C. by an exchanger.
The ammonium 2-cyanophenate decomposed to ammonia and was eliminated from the column head.
The crude 2-hydroxybenzonitrile dissolved in xylene (F3) was recovered from the column bottom.
The tire of the crude 2-hydroxybenzonitrile was 89% by weight (ex solvent).
The recovery yield was 94% (0.49 moles).
In the apparatus shown in
The following results were obtained:
The crude reaction stream from a reactor comprising 0.52 moles of 2-hydroxybenzonitrile in its salt form (2-HBN) and 1.7 moles of ammonia (F1) at 420° C. was brought into contact with 200 g of xylene in wash tower (1).
The stream was then transferred to a column (2) where the mixture was cooled to 110° C. by an exchanger.
The ammonium 2-cyanophenate decomposed to ammonia and was eliminated from the column head.
The crude 2-hydroxybenzonitrile dissolved in xylene (F3) was recovered from the column bottom.
The titer of the crude 2-hydroxybenzonitrile was 89% by weight (ex solvent).
The recovery yield was 94% (0.49 moles).
In the apparatus shown in
The following results were obtained:
In the apparatus shown in
The following results were obtained:
The crude reaction stream from a reactor comprising 0.52 moles of 2-hydroxybenzonitrile in its salt form (2-HBN) and 1.7 moles of ammonia (F1) at 420° C. was brought into contact with 180 g of xylene and 20 g of DMF in the wash tower (1).
The stream was then transferred to a column (2) where the mixture was cooled to 110° C. by an exchanger.
The ammonium 2-hydroxybenzonitrile decomposed to ammonium and was eliminated from the column head.
The crude 2-hydroxybenzonitrile dissolved in the xylene+DMF (F3) was recovered from the column bottom.
The titer of the crude 2-hydroxybenzonitrile was 88% by weight (ex solvent).
The recovery yield was 97% (0.49 moles).
In the apparatus shown in
The following results were obtained:
It should be understood that the invention defined in the accompanying claims is not limited to the particular implementations described in the above description but encompasses variations that do not depart from the spirit or the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 00/07568 | Jun 2000 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR01/01833 | 6/13/2001 | WO | 6/10/2003 |
