Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
  • C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
  • C07C37/84—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by crystallisation

Definitions

• the subject of the present invention is a process for the preparation of highly purified hydroquinone, said process notably enabling access to different degrees of high purity.
• the invention aims to provide hydroquinone free of impurities resulting from its preparation process. 0
• Hydroquinone (or 1,4-dihydroxybenzene) is a product widely used in many fields of application as a polymerization inhibitor, an antioxidant in elastomers or as a synthesis intermediate. Another area of application is photography. It follows that it is a consumer product.
• hydroquinone must meet requirements of varying purity and which can be in some cases quite restrictive.
• the problem that arises is that purification is not easy because hydroquinone is an oxidation-sensitive product which rapidly leads to degradation products which are colored.
• a strong protic acid that is to say an acid having a pKa in water of less than 0.1, preferably less than - 1.
• strong protic acids examples include sulfuric acid, chlorosulfuric acid, perchloric acid, sulphonic acids, for example methanesulphonic acid, trifluoromethanesulphonic acid, toluenesulphonic acid, phenolsulphonic acid, and the like.
• protic acid catalysts there may be mentioned sulfonic resins and more particularly the resins marketed under different trade names. Among others, mention may be made of the following resins: Temex 50, Amberlyst 15, Amberlyst 35, Amberlyst 36, Dowex 5OW.5 [0014]
• the abovementioned resins consist of a polystyrene backbone bearing functional groups which are sulfonic groups. .
• the polystyrene backbone is obtained by polymerization of styrene and divinylbenzene, under the influence of an activation catalyst, most often an organic peroxide, which leads to a cross-linked polystyrene which is then treated with sulfuric acid or concentrated sulphochloride leading to a sulfonated styrene-divinylbenzene copolymer.
• sulphonic resins which are phenol-formaldehyde copolymers and which relate to the aromatic ring a methylenesulphonic group, for example the resin sold under the name Duolite ARC 9359.
• a mixture comprising essentially pyrocatechol (or 1, 2-dihydroxybenzene) and hydroquinone, in variable proportions with, in general, a mass ratio pyrocatechol / hydroquinone of from 0.25 to 4.0, as well as various by-products in much smaller quantities, especially resorcinol (or resorcin or 1,3-dihydroxybenzene) and trihydroxybenzenes, and more particularly pyrogallol (or 1, 2,3-trihydroxybenzene), generally at levels of the order of 0.5% to 4.0% by weight, percentages expressed relative to the amount of hydroquinone and pyrocatechol (or pyrocatechol) formed.
• variable compositions comprising, by weight, from 20% to 80% of pyrocatechol, from 80% to 20% of hydroquinone, from 0.1% to 2% of resorcinol and 0.1% at 2% pyrogallol.
• mixtures comprising, by mass, from 50 to 80% of pyrocatechol, from 20 to 50% of hydroquinone, from 0.1 to 2% of resorcinol and from 0.1 to 2% of pyrogallol are obtained. .
• a currently known method is to perform the distillation of said mixture to obtain at the top of the distillation pyrocatechol (which is the most volatile compound of the mixture), and at the bottom of distillation, a "crude hydroquinone" HQ 0 , namely a mixture containing mainly hydroquinone, associated with small amounts of impurities (resorcinol and pyrogallol as well as any traces of pyrocatechol not removed by the distillation ).
• hydroquinone consist in the oxidation of 1,4-diisopropylbenzene, with as by-products Ie 1, 2- and / or 1,3-dihydroxybenzene (pyrocatechol and resorcinol). in the absence of tri-hydroxybenzene compounds, such as pyrogallol.
• the document FR 2 788 763 discloses the preparation of crude hydroquinone containing dihydroxy impurities, pyrocatechol and resorcinol. The pyrocatechol is removed by distillation, and the purified hydroquinone is obtained by melt refining the hydroquinone / resorcinol binary mixture.
• the invention provides a method for obtaining a hydroquinone having the desired purity.
• an object of the invention is to provide a crude hydroquinone purification process, in which are simultaneously present di-hydroxybenzene and tri-hydroxybenzene impurities.
• Another object of the invention is to provide a flexible process that allows to control the purity of the desired hydroquinone and to obtain a product that can meet high purity requirements.
• a process for the preparation of hydroquinone from a crude hydroquinone characterized in that it comprises at least the steps the following: (a) crude hydroquinone in liquid form, containing at least resorcinol and pyrogallol as impurities, is subjected to controlled cooling to crystallize pure hydroquinone, (b) separation of pure hydroquinone crystals from liquors (c) reheating and partial melting; (d) total melting of purified hydroquinone; and (e) recovery of purified hydroquinone.
• a hydroquinone is obtained whose purity is more or less improved according to the type of embodiments of the invention.
• composition of the crude hydroquinone HQ 0 treated according to the steps of the process of the invention may vary to a relatively large extent.
• the process of the invention is particularly well suited for crude hydroquinones having total impurity contents of the order of 0.5% to 6% by weight, for example 0.5% to 4% by weight, in particular from 1% to 3% by weight relative to the total mass of crude hydroquinone.
• the invention can also be applied to crude hydroquinones richer in impurities beyond 10% impurities.
• a crude hydroquinone HQ 0 treated according to the invention contains from 0.1 to 4%, for example from 0.2 to 3% by weight, of "light" impurities consisting essentially of the isomers of the hydroquinone namely resorcinol and possibly pyrocatechol residual.
• the amount of "heavy" impurities, the most important is constituted by pyrogallol is usually from 0.1 to 4%, for example from 0.2 to 3% in mass.
• a crude hydroquinone HQ 0 particularly suitable for the process of the invention comprises, by weight relative to the total amount of crude hydroquinone: from 94 to 99.5% of hydroquinone,
• pyrocatechol in the form of traces, for example from 10 to 100 ppm, preferably from 10 to 20 ppm.
• the purification process of the present invention corresponds to a purification, without solvent, by crystallization.
• the crude hydroquinone, containing impurities is engaged in the purification process in liquid form, without solvent, that is to say in the molten state.
• the method according to the invention has the advantage of being easily implemented on an industrial scale, with relatively low costs compared to the methods currently used today.
• the process of the invention makes it possible to obtain hydroquinone of high purity, without using the methods conventionally used, such as distillation, or else recrystallization in a solvent medium, which use a large amount of energy and / or require the use of large amounts of solvent.
• the process according to the present invention makes it possible to obtain hydroquinone of high purity, especially containing less than 3% by weight, advantageously less than 2% by weight, generally less than 1% by weight, at a few hundred ppm. (by weight) impurities, or even a few tens of ppm (by weight) of impurities.
• the process of the invention makes it possible to reduce the quantities of dihydroxybenzene impurities, such as resorcinol, and the tri-hydroxybenzene impurities, such as pyrogallol. j
• the oxygen is removed beforehand from the chamber in which the purification operation is carried out.
• the supply of hydroquinone in the liquid state is carried out in an oxygen-free atmosphere.
• the hydroquinone is introduced in the liquid state into the crystallizer. One can consider feeding the hydroquinone in the liquid state directly from a manufacturing line.
• the product is heated to its melting temperature.
• the crude hydroquinone is brought to a temperature slightly above the hydroquinone melting temperature, preferably greater than 5 0 C above its melting point, more preferably greater than 5 0 C to 30 0 C with respect to its melting point.
• the temperature at which the crude hydroquinone is carried is chosen between 175 ° C. and 200 ° C., preferably between 178 ° C. and 195 ° C., advantageously between 180 ° C. and 185 ° C.
• the melting operation is carried out, generally with stirring and can be carried out in a stirred tank and heated.
• the heating is advantageously carried out by circulation of steam or a suitable coolant in the jacket.
• coolants suitable for the invention there may be mentioned in particular heavy esters of carboxylic acids (for example, octyl phthalate), aromatic ethers such as biphenyl oxide and / or benzyl, diphenyl, terphenyls, other partially hydrogenated polyphenyls, paraffinic and / or naphthenic oils, petroleum distillation residues, silicone oils, etc.
• carboxylic acids for example, octyl phthalate
• aromatic ethers such as biphenyl oxide and / or benzyl, diphenyl, terphenyls, other partially hydrogenated polyphenyls, paraffinic and / or naphthenic oils, petroleum distillation residues, silicone oils, etc.
• the crude hydroquinone directly from a manufacturing line, or having undergone a melting operation
• a crystallizer previously put under an atmosphere inert as indicated previously.
• the crystallizer (or crystallizer) may be of any type known per se as indicated below, depending in particular if the process is carried out continuously or discontinuously, and optionally has a stirring system. It can operate in a static melt (without agitation or circulation of the liquid phase) or dynamic (loop circulation of the liquid, dripping film technique or other).
• the crystallizer is equipped with a system for both controlled heating and cooling of species present therein.
• a system is generally used for circulating a heat transfer fluid in a double jacket, and / or a system of heat exchanger type, tubes, plates, disks, etc..
• the fluids will be used usually used for such purposes, including fluids with a high boiling point at least greater than 200 D C, see at 250 0 C, and having a viscosity adapted in the temperature range implemented during the process of the invention.
• the equipment, and in particular the crystallizers, used for the process of the present invention are known and can be of any type known per se, for example those used in the Proabd ® MSC process, and in particular the crystallizers for crystallization in vitro. medium melted marketed by the company Sulzer (see http://www.sulzerchemtech.com) or by the company Covalence (Saint-Amand-les-Eaux, France).
• the first step of the process consists in a controlled cooling of molten hydroquinone (HQ 0 ) according to a "temperature gradient" curve. g / decreasing / time "(see Example 1) according to a previously established hydroquinone / impurity phase diagram (s). It has been discovered that phase diagrams can be constructed between pure hydroquinone and the impurities it contains.
• phase diagrams have a eutectic point for hydroquinone / resorcinol, a eutectic point for hydroquinone / pyrogallol, a eutectic point for resorcinol / pyrogallol and a eutectic point for hydroquinone / resorcinol / pyrogallol.
• This last point called more simply "eutectic point” in the following, corresponds to a temperature which is denominated "temperature of inversion" in the continuation of this exposition.
• This inversion temperature is lower than the melted HQ 0 temperature, and is generally between 80 0 C and 100 0 C, preferably between 9O 0 C and 95 0 C, and for example around 95 ° C , for crude hydroquinones containing from 0.5% to 6% of impurities as defined above.
• the duration of this first cooling step to the inversion temperature can vary within wide limits depending on whether the thermal gradients (temperature difference between the crystallizer (heat transfer fluid) and the melt) are low or large. .
• the duration of the first step can generally vary from a few minutes to a few hours (1 or 2 hours, for example).
• cooling is generally carried out relatively slowly, for example of the order of 5 to 15 hours, advantageously of the order of 8 to 12 hours, generally of the order of 10 hours.
• the cooling of the melt leads to the appearance of purified hydroquinone crystals, that is to say containing a reduced amount of impurities (relative to HQ 0 ).
• the crystallizer contains crystals of purified hydroquinone, and a residual liquid phase (mother liquors) concentrated in impurities.
• the mixture of crystals and liquid is advantageously, but not necessarily, maintained at the inversion temperature for a time sufficient to reach thermal equilibrium and minimize the final supersaturation.
• This duration varies according to whether the process is conducted statically or dynamically, as indicated above, and is generally between a few minutes and 4 hours, for example approximately 2 hours, in the case of processes carried out in static mode. It is also possible to promote crystallization, or even to control the formation and porosity of the crystal lattice, for example by creating a cold spot, or by introducing seed crystals at a content preferably of less than 2%.
• crystallization seeds a small amount of crystallized hydroquinone originating for example from a previous manufacture and optionally of suitable particle size is used.
• the hydroquinone crystals are separated from the mother liquors.
• This separation is carried out according to the conventional liquid-solid separation techniques known to those skilled in the art, and in this respect, for example, gravitational flow separation or mechanical separation, such as filtration, centrifugation or spinning, or else by pressurizing inert gas (generally nitrogen), the latter technique allowing desaturation / filtration of liquid retention impregnating the crystal lattice, that is to say promoting the elimination of the impure liquid phase included in the crystals.
• a solid / liquid separation technique quite suitable for the process of the present invention is gravity flow separation.
• the separation step is generally conducted at the end of crystallization temperature, that is to say at the inversion temperature. However, a different temperature may be chosen, although this is not a preferred embodiment of the invention.
• the third step of the process consists in heating in a controlled manner the crystallizer of the inversion temperature, up to the melting point of the pure hydroquinone (172 ° C.), or just above the melting point. of 173-174 ° C., and to partially melt pure impure hydroquinone crystals by impure liquid phase retention. This is called bleeding: the purity of the liquid phase withdrawn continuously increases continuously: its purity globally describes the liquidus liquid-solid phase diagram.
• the duration of this third step may also vary in large proportions (depending on whether the process is static or dynamic as indicated above), and is generally conducted for a period ranging from a few minutes to 12 hours, preferably for 2 to 10 hours, more preferably for about 6 hours, in the case of a static process.
• the melting step is carried out by heating to a temperature above the partial melting point (172 ° C.), in order to remelt all the purified hydroquinone crystals. .
• This step is carried out for a period generally of between a few minutes and 8 hours, more preferably between 1 and 6 hours, in particular for a duration of the order of 4 hours.
• This shaping can in particular be carried out by implementing one or the other of the following techniques: ⁇ a shearing on a cylinder or on a strip, in which the liquid hydroquinone is brought into contact with a cylinder or a colder metal strip, then scraping with a knife the film obtained on the cylinder, whereby the solid hydroquinone is recovered in the form of scales, "a prilling" (as pearls), as described in particular in
• EP-A-1 556 322 in which the liquid hydroquinone is dispersed in the form of drops in a stream of air, for example by dropping it from the top of a tower in a column of air or inert gas, which leads to obtaining solid hydroquinone in the form of pearls, • quenching or shot blasting, where the liquid hydroquinone is dispersed generally in the form of drops, in an immiscible cold liquid, whereby solid hydroquinone is obtained in the form of aggregates.
• the purified hydroquinone obtained according to the process of the invention comprises a very low level of impurities, as indicated below.
• the purified hydroquinone in liquid form may be re-engaged, in whole or in part, in the refining process as described above; to say in a second refining stage.
• This embodiment makes it possible to further increase the purity of the hydroquinone.
• the amount of hydroquinone of intermediate purity HQ 1 introduced with the main feed of crude hydroquinone HQ 0 can vary in large proportions.
• An advantageous ratio of recycling HQ 0 / HQ 1 can for example be ⁇ close to 1.
• a ratio HQ 0 I HQ 1 greater than 1, for example close to 2 is possible but involves a larger volume to be treated, although it is quite compatible with a gain in the degree of purity of hydroquinone obtained.
• a ratio HQ 0 I HQ 1 less than 1, for example close to 1/2 is also possible but has little advantage with respect to the gain in degree of purity hydroquinone obtained.
• the method of the invention can be implemented by combining one or more refining stages and one or more recycling. It should be noted that recycling can be carried out on the same refining stage or between two or more refining stages.
• the method of the invention can be implemented with two refining stages, and a recycling stage 2 to stage 1, or with three refining stages, and a recycling of the floor 3 to floor 2 and / or floor 1, or alternatively with four refining stages, and recycling from floor 4 to floor 3 and / or recycling from floor 2 to floor 1 and / or recycling from stage 4 to stage 1, etc.
• the refining operations implementing the method of the invention can be carried out in continuous or discontinuous mode.
• several crystallizers, static or dynamic can therefore be arranged in cascade, in series and / or in parallel.
• the hydroquinone content is greater than 97%, advantageously greater than 98%,
• the resorcinol content is less than 8000 ppm, preferably less than 4000 ppm, more preferably less than 400 ppm, or even less than
• hydroquinone is less than 8000 ppm, preferably less than 4000 ppm, more preferably less than 400 ppm, or even less than 100 ppm.
• hydroquinone it is possible to obtain hydroquinone:
• the method of the invention is particularly interesting because it allows to obtain hydroquinone with different degrees of purity ranging between at least 98% and can be close to 100%.
• FIG. 1 schematically represents an embodiment of the method of the invention implementing a refining stage, in which:
• FIG. 2 is a diagram of an embodiment with a stage for refining and recycling an HQ fraction of intermediate purity, in which:
• FIG. 3 diagrammatically represents another embodiment of the method of the invention implementing two refining stages, with two internal recycling operations at each of the two stages, as well as a recycling of the stage 2 towards the floor 1.
• this embodiment :
• feed 2nd stage HQ pure 1 st floor (4) + recycling HQ intermediate purity 2nd stage (7)
• the first step consists of a controlled cooling of 185 ° C to
• the second stabilization step lasting for 2 hours, is carried out at the inversion temperature of 95 ° C., to reach thermal equilibrium and to minimize the supersaturation final.
• the third step is dewatering at the inversion temperature of 95 ° C., and consists in withdrawing the residual liquid phase concentrated in impurities.
• the fourth step of a duration of 6 hours, bleeding, consists of heating the crystallizer in a controlled manner from 95 ° C. to 172 ° C., and to partially melting the pure hydroquinone crystals impregnated with retention. impure liquid phase.
• the withdrawal is fractionated so as to establish, after chemical analysis of the different fractions, an experimental characteristic of the purification, where the purity of the production is represented as a function of the recovery rate of the initial charge.
• the fifth step is the melting step of a duration of 4 hours, it is carried out from 172 0 C is redone all the pure hydroquinone crystals.
• EXAMPLE 2 1-Stage Process Without Internal Recycling (FIG. 1) A crude hydroquinone is purified to 4% by weight of total impurities (2% resorcinol weight, 2% pyrogallol weight, traces of pyrocatechol). The following Table 2 groups the data of the experimental purification characteristic.
• EXAMPLE 4 Process 1 Stage with Internal Recycling (FIG. 2) A mixture of crude hydroquinone at 4% by weight of total impurities (2% resorcinol weight, 2% pyrogallol weight, pyrocatechin traces) is removed. hydroquinone recycled from a previous operation at 6.02% weight of impurities (3.01% by weight of resorcinol, 3.01% by weight of pyrogallol). According to the process scheme of FIG. 2, Table 5 is obtained:
• EXAMPLE 6 Process with 2 stages of purification and internal recycling As for Example 5, a mixture of crude hydroquinone at 4% by weight of total impurities (2% by weight resorcinol, 2%) is purified on a 1st stage. % pyrogallol weights, traces of pyrocatechol) and hydroquinone recycled from a previous operation at 6% weight of impurities (3% by weight of resorcinol, 3% by weight of pyrogallol).

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• 2006
  • 2006-09-04 FR FR0607730A patent/FR2905374B1/fr not_active Expired - Fee Related
• 2007
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