WO1997026217A1 - Dearomatisation of aromatic organo-halogenated and/or organo-oxygenated compounds in the presence of a ruthenium catalyst - Google Patents

Abstract

A method for the dearomatisation and hydrodehalogenation of aromatic organo-halogenated and/or organo-halogenated and oxygenated compounds is disclosed. The method may advantageously be used to remove pollutants from effluents containing polychlorodiphenyl compounds such as pyralene, mono- and polychlorophenols, mono- and polychloro anilines and polychlorodioxins. The method comprises catalytically hydrogenating said compounds dissolved or suspended in a preferably alkaline aqueous solution, using hydrogen at a pressure of 1-20 bars, in contact with a ruthenium catalyst and at temperatures between room temperature and 100 °C.

Description

 DEAROMATION OF ORGANO-HALOGEN AND / OR ORGANO-OXYGEN AROMATIC COMPOUNDS IN THE PRESENCE OF A RUTHENIUM-BASED CATALYST

The present invention relates to a process for the aromatization of organo-halogenated and / or organo-oxygenated aromatic compounds in the presence of a ruthenium-based catalyst. It also relates more particularly to a process for the aromatization and to hydrodehalogenation of organo-halogenated aromatic compounds, and / or organo-halogenated and oxygenated compounds, more particularly of organo-chlorinated compounds, said method comprising the use of a catalyst based The invention also relates to the application of this process to the decontamination of aqueous effluents containing said compounds

In the present application, the term “hydrodehalogenation” relates to the elimination in a hydrogen atmosphere of the halogen atoms entering into the structure of an aromatic compound containing them. In addition, the term “dearomatization” signifies the loss of character. aromatic of the compound by partial or complete hydrogenation of the aromatic nucleus Certain aromatic organo-halogenated compounds, more particularly organo-chlorinated, are generally known for their harmfulness with regard to man and his environment. Among these compounds, it is possible by example include chloroanilines which, in substituted form, are constituents of many fungicides, pesticides and weedkillers, chlorophenols, which can be present on polluted lumber treatment sites or in the residues of treatment of crude oil in refinery, as well as polychlorinated biphenyls or PCBs, such as pyralene, which are found among others es in electrical transformers and capacitors A classic way to destroy this type of organochlorine compounds is to incinerate them at a sufficient temperature while preventing molecular recombination resulting in the formation of dioxins, molecules just as harmful as the original product This way of operating leads to the ultimate products carbon dioxide and hydrochloric acid It is currently widely implemented but requires heavy investments as well as transport of pollutants to the treatment site

Processes provided for this purpose have therefore been implemented, and it has been demonstrated, on the one hand, that hydrogenation in the presence of certain metal catalysts, such as palladium, is capable of inducing the hydrodechlorination of compounds chlorinated aromatics, and on the other hand that hydrogenation in the presence of a nickel catalyst was capable of hydrogenating the aromatic nucleus into saturated hydrocarbon Certain processes, which provide for wet oxidation, using as air oxidant or pure oxygen, use catalysts based on more or less complex oxides under high pressures, of the order of 50 to 200 bars and at temperatures of the order of 150 to 300 ° C. But the investments for the development of this type of process and their operating costs are very high

Other methods, in particular of catalytic hydrogenation of chlorobenzenes and chlorophenols have been described in patents or scientific publications (ref 1, 2, 3 and 4) However, the catalysts used, such as NiMo (Nickel / Molybdenum) on alumina γ, showed only a weak activity as well as an inability to hydrogenate the aromatic nucleus, even under drastic conditions, in particular at temperatures above 225 ° C

The various catalysts used in the processes of the prior art can therefore only catalyze one reaction at a time, either hydrodehalogenation or de-aromatization

The aim of the present invention is to remedy these drawbacks, in particular to provide a process using hydrogen, applicable to the destruction of organohalogenated aromatic compounds, oxygenated, or at the same time organo-halogenated and oxygenated under conditions of temperature close to or slightly higher than room temperature, and under pressures in hydrogen gas more reduced than in the previous processes, and this so as to produce hydrodichlorations and dearomatizations of said compounds

The process for de-aromatization and, where appropriate, hydrodehalogenation, of organo-halogenated, oxygenated, or both organo-halogenated and oxygenated aromatic compounds, in accordance with the invention, comprises the treatment with hydrogen of a solution or suspension, in particular aqueous, and preferably alkaline, containing said compounds, in the presence of a ruthenium-based catalyst

By the expression “ruthenium-based catalyst” is meant in the remainder of this description, in a non-limiting manner, a catalyst in the form of ruthenium metal, for example in the divided state, or of any other alloy or other association or chemical combination in which ruthenium can enter without losing its catalytic qualities in the abovementioned reactions, or alternatively catalysts in which the above ruthenium, alloys and chemical combinations are in "supported" form on supports making it possible to accentuate the divided character By way of example of catalysts based on ruthenium capable of being used, mention will be made of the associations of ruthenium with platinum, palladium, nickel, zinc or iron

When using supported catalysts, the catalyst support is advantageously selected from a set of supports comprising activated charcoal, silica, alumina, silicon alumina, magnesia, titanium oxide, a zeolite or any other already known and sufficiently divided support As such, one could also cite iπfusoires earths, silica gels, peat or KIESEL GUHR®, among others Preferably, we choose a support in the state divided, allowing adsorption of said aromatic compounds such as activated carbon Such support is therefore all the more effective that it allows better adsorption of said compounds, and that it has better compatibility with the catalyst, the adsorption of said compounds on the support making it possible to optimize the efficiency of the process. invention, and in the case of said organo-halogenated and / or organo-halogenated and oxygenated aromatic compounds, the use of a ruthenium catalyst allows the two phases of the process of transformation of an aromatic organo-halogenated compound into a compound non-halogenated completely saturated to be carried out in a single stage One could thus speak ICI of reaction "of hydrodehalogenation-désaromatisation"

The reaction is preferably carried out in a medium with an alkaline pH, even if only in the presence of a weak base. This alkaline nature allows the neutralization of the compounds of acidic nature, in particular the acid halides which are formed during the reaction. The desired dehalogenation is however greatly favored when the aqueous alkaline solution containing the organohalogenated and / or oxygenated aromatic compounds comprises at least one stronger alkali or alkaline earth metal hydroxide, such as potassium hydroxide KOH, dihydroxide calcium Ca (OH ₂ ), or preferably sodium hydroxide NaOH, or compounds or salts such as carbonates of alkali metals, capable of releasing a base in the presence of a halogen acid, the latter being at its tower neutralized at the end of the reaction The neutralization of the phenols, if they are present, tends to increase the reaction rate. ce of sodium hydroxide NaOH Better reaction rates, as well as better yields, are obtained in the presence of this base The various bases mentioned above, and in particular sodium hydroxide NaOH, apparently behave as if they acted as "co-catalysts" of the reaction It is therefore highly preferred to use the "combination" of a ruthenium catalyst and a "co-catalyst" basic catalyst to ensure effective implementation of the process according to the invention

In general, and in the case of "hydrodehalogenation-desaromatization", the amount of base added must be at least sufficient to neutralize the hydrochloric acid produced by the hydrodechlorination of the treated compounds.

In general, the temperature, the hydrogen pressure and the reaction time are adjusted so as to allow, at the same time as complete aromatization as possible of said aromatic organohalogen compounds, by saturation of their aromatic nuclei with hydrogen, and the desired dehalogenation

However, other dearomatization mechanisms can also be used, for example when the organohalogenated and / or organohalogenated and oxygenated aromatic compounds to be treated, for example polychloro-dioxins, comprise cyclic groups containing oxygen. in their structure The hydrodehalogenation-dearomatization reaction is then accompanied by the formation not only of acid halides, but also of the corresponding cyclic alcohols When the solution - or the effluents containing said compounds to be treated - have been alkalized, their contacting with gaseous hydrogen is advantageously carried out under a pressure within a range from atmospheric pressure to about 20 bars and at a temperature within a range from ambient temperature to about 100 ° C. When this temperature is below 80 ° C., the catalyst is preferably activated by pr heating to a temperature of at least about 80 ° C, in particular when the contacting is itself carried out at a temperature of about 80 ° C or lower than 80 ° C Advantageously, this process is carried out at ambient temperature, and under a hydrogen pressure less than or equal to 2.5 bars, preferably equal to ambient pressure.

Thus, while the processes of the prior art are generally carried out under conditions of high temperature and pressure of hydrogen gas, that is to say respectively greater than 150 ° C. and greater than 20 bars, the method of the present invention, which uses a ruthenium-based catalyst, has the advantage of allowing the reaction to proceed under less restrictive conditions, in particular under ambient conditions. This avoids the use of a device complex reaction, having to withstand overpressures and high temperatures, without reducing the yields of the reaction

In the case of certain organohalogenated aromatic compounds of lower reactivity, the nucleus of which is substituted by halogen groups other than chlorine, the values relating to the temperature, the pressure of hydrogen gas and / or the reaction time must be This adaptation of the reaction conditions must be carried out so that these compounds can undergo hydrodehalogenation-dearomatization according to the process of the invention.

The process according to the invention finds a particularly advantageous industrial application in the decontamination of highly toxic effluents polluted by the aromatic compounds described above. In particular, the harmfulness of this type of effluent is often due to high levels of chlorophenols, chloroanilines and / or polychlorobiphenyls. These compounds exhibit excellent reactivity here under non-binding temperature and pressure reaction conditions. The decontamination of these effluents corresponds to a degradation of said aromatic compounds to be treated into non-hazardous products, in particular cyclohexane or cyclohexanol. It must also be clear that the compounds referred to in the present text under the expression "aromatic organo-halogenated, oxygenated, or both organo-halogenated and oxygenated" also extends to aromatic compounds of the dioxin type, in particular complex structures, for example polyhalogen-dioxins, in which aromatic rings are associated with heterocycles including other atoms, for example oxygen

The most known polluting chlorinated aromatic molecules are a) polychlorodioxins (PCD), one of the typical examples of which is 2,3,7,8 tetrachlorodioxin (2,3,7,8 TCD), b) polychlorobiphenyls (PCB) which are transformer oils or c) chlorophenols

A catalytic hydrodechlorination-dearomatization of these compounds is carried out according to the following reactions

Lorsque les effluents pollués sont non basiques, on opère, de préférence, une alcalinisation desdits effluents, préalablement à la décontamination, par l'introduction d'une base, en particulier de l'hydroxyde de sodium, en quantité suffisante pour aboutir à une alcalinité favorable à la réaction d' « hydrodéhalogénation-désaromatisation » D'une façon générale, la quantité de base à mettre en oeuvre est directement liée à la quantité de composés organohalogénés ou organo- oxygénés ou les deux à la fois contenus dans les effluents qu'il faut « dépolluer » Dans certaines situations, les polluants sont déjà en concentration adéquate pour que le procédé selon l'invention puisse leur être directement appliqué Par exemple, une grande quantité d'effluents aqueux pollués par des composés organo-chlorés est récupérée dans les eaux de rinçage d'objets industriels qui ont été mis au contact de produits polluants tels que les PCB, et notamment le pyralene D'autres industries, telle que l'industrie agrochimique productrice de fongicides, pesticides ou désherbants, génèrent d'importantes quantités d' effluents pollués par de tels composés Le cas échéant, l'on procède à une « pré-concentration » des effluents, avant de leur appliquer le procédé selon l'invention Ainsi, selon une application du procédé de l'invention les effluents sont, si nécessaire, préalablement concentrés de sorte que les composés aromatiques organo-halogénés ou organo-oxygénés, ou les deux à la fois, soient à une concentration comprise entre 100 ppm et 100 000 ppm.

When the polluted effluents are non-basic, an alkalization of said effluents is preferably carried out, prior to decontamination, by the introduction of a base, in particular sodium hydroxide, in an amount sufficient to achieve alkalinity. favorable to the “hydrodehalogenation-dearomatization” reaction In general, the quantity of base to be used is directly linked to the quantity of organohalogenated or organo-oxygenated compounds or both both contained in the effluents than In certain situations, the pollutants are already in an adequate concentration so that the process according to the invention can be directly applied to them. For example, a large quantity of aqueous effluents polluted by organo-chlorinated compounds is recovered in the rinsing water from industrial objects which have been brought into contact with pollutants such as PCBs, and in particular p yralene Other industries, such as the agrochemical industry producing fungicides, pesticides or weed killers, generate large quantities of effluents polluted by such compounds. If necessary, a effluent "pre-concentration" is carried out. , before applying the method according to the invention Thus, according to an application of the method of the invention the effluents are, if necessary, previously concentrated so that the aromatic organohalogenated or organo-oxygenated compounds, or both at the times, are at a concentration between 100 ppm and 100,000 ppm.

The invention can also find other applications, in particular when it leads to valorized products of the oxygenated cyclan type from the compounds to be treated. Mention may in particular be made of oxygenated cyclans such as cyclohexanol which is, in fact, an intermediate in the manufacture of polyamides, and which is obtained by “hydrodehalogenation-dearomatization” of aromatic organohalogen compounds such as mono- or polychlorinated phenols or polychlorodioxiπes Other products of the reaction are in turn upgraded to saturated cyclic hydrocarbons for the production of fuels and solvents

The aromatic organo-halogenated compounds in respect of which interesting results are obtained, correspond to the tri-, preferably di-, preferably mono-halogenated compounds, the compounds with “para” orientation being preferable to the “meta” or “ortho” isomers

Detailed description of examples

The following examples were carried out in the laboratory The quality of the results obtained attests to the feasibility of the process under industrial conditions

In a first phase, the support is prepared on which the reaction catalyst will be deposited. This support can be selected from the supports mentioned above, or from any other type of support, as soon as it is sufficiently divided and that it does not negatively interact in the hydrodehalogenation-dearomatization reaction according to the invention

This first phase of preparation of a catalyst support makes it possible to optimize the efficiency of the reaction according to the type of organo-halogenated, oxygenated, or both organo-halogenated and oxygenated compounds (or the type of effluents containing said compounds ) which one wishes to treat One can however use products already prepared Indeed, there are on the market ruthenium-based catalysts on active carbon Ru / C sold by the company DEGUSSA® (catalyst type H101 B at 5% of ruthenium) This type of product was also used for the examples of embodiment below

In a second phase, about 30 to 50 grams of water are introduced into an autoclave, as well as the necessary quantity of catalyst previously quantified and deposited on the adsorbent support or a DEGUSSA® catalyst type H101 B In order to obtain a relatively pure hydrogen gas phase, the air inside the autoclave is completely purged. The medium contained in the autoclave is then heated so as to effect a "preactivation" of the catalyst at a temperature can vary between 70 ° C and 90 ° C This "preactivation" of the catalyst is carried out with stirring, under a pressure of hydrogen gas H ₂ of the order of 2 to 5 bars and for approximately 5 to 15 minutes

An alkaline solution containing the compounds to be treated is then introduced into the autoclave. This solution, of volume approximately equal to 10 ml, contains approximately 2 to 4 grams of said compounds and approximately 0.5 to 2 grams of a base so as to be able to neutralize all of the acid halide produced

A stirring phase which can vary between 30 minutes and 2 hours is then implemented. This stirring takes place under a hydrogen pressure similar to that of the "preactivation" phase (if the catalyst has not already been activated), and at a temperature within a range defined by the ambient temperature and a temperature of 150 ° C.

Following this stirring phase, the autoclave is purged, then cooled and finally opened. In order to determine the level of aromatic compounds remaining, and thereby the reaction yield, an analysis of the liquid phase is carried out in the autoclave. by a UV-Visible spectrometry technique

The results show that the levels of chloroaromatic compounds remaining in solution are in all cases less than 100 ppm Other techniques can be used to determine the quality or the quantity of the products obtained

- the balance on the volume of hydrogen consumed, which corresponds to the transformation of the aromatic organo-halogenated compound into its saturated counterpart and into halide ions, - IRFT spectrometry and CPV analysis, - the dosage of the mineral halide which corresponds to the transformation of 100% of the organic halogen into metallic halogen.

Other characteristics of the invention also follow from the following examples, the sole purpose of which is moreover to illustrate the invention without, however, limiting it.

EXAMPLES

EXAMPLE 1 40 g of water are introduced into an autoclave, 0.25 g of a

5% ruthenium on activated carbon (DEGUSSA® type H101 B) After purging the air, the catalyst is preactivated at 80 ° C. with stirring in the presence of hydrogen under pressure of 2.5 bars, for 10 minutes. 2 g of parachlorophenol dissolved in a solution containing 10 ml of water and 0.62 g of pure caustic soda are then added. After 1 hour of stirring under 2.5 bar of H ₂ and at 80 ° C, the autoclave is purged, cooled and opened. Analysis of the liquid by UV-Visible spectrometry shows that less than 100 ppm of aromatic products remain. In addition, the balance is determined on the volume of hydrogen consumed which corresponds to the transformation of parachlorophenol into cyclohexanol and into Cf ions. IRFT spectrometry and CPV analysis make it possible to detect cyclohexanol as the only organic product in solution, if l 'except for residual traces of chlorinated aromatic products. The metered mineral chlorine corresponds to the transformation of 100% of the organic chlorine into NaCl. This example demonstrates that a ruthenium catalyst deposited on a charcoal is capable of quantitatively transforming parachlorophenol into cyclohexanol and chloride ions. Example 2:

The procedure is as in Example 1 except that 1 g of Ru / C is used, and the reaction takes place at 25 ° C. The solution taken after one hour of stirring under hydrogen, analyzed as in Example 1, contains less than 100 ppm of aromatic products, cyclohexanol and sodium chloride. This example shows that the reaction can take place at room temperature and transforms the whole parachlorophenol after one hour provided that the mass of catalyst is quadrupled.

Example 3 ^•

After 1 hour 36 minutes the orthochlorophenol is also transformed into cyclohexanol and chloride ions by operating as in Example 1 At the end of the reaction, less than 60 ppm of aromatic products remain in the autoclave

Example 4 ^•

After 1 hour 42 minutes of stirring under hydrogen under the conditions of Example 1, a solution of metachlorophéπol is transformed at 100% into cyclohexanol and chlorine ions, since it contains only a concentration of less than 100 ppm of products aromatic.

Example 5:

The procedure is as in Example 1, except that 2.5 g of 3,5-dichlorophenol dissolved in 10 ml of water and 1.24 g of sodium hydroxide are added. After 2 hours 24 minutes of stirring under hydrogen, the autoclave solution contains less than 60 ppm of aromatic products. 3,5-Dichlorophenol transformed into cyclohexanol and sodium chloride quantitatively. Example 6 ^•

The procedure is as in Example 1, except that 3 g of 2,4,5-tπchlorophénol dissolved in 10 ml of water and 1.86 g of sodium hydroxide are added. After 10 hours 20 minutes of stirring under hydrogen, the autoclave solution contains less than 60 ppm of aromatics 2,4,5-chlorophenol has converted to cyclohexanol and sodium chloride quantitatively

EXAMPLE 7 50 g of water, 0.25 g of Ru / C catalyst at 5% active metal, 3 g of 2,4,6-chlorophenol and 1.86 g of sodium hydroxide pellets are introduced into the autoclave. After 7 hours of stirring under 2.5 bar of hydrogen at 80 ° C., the autoclave is purged, cooled and opened. Analysis of the solution by CPV and by IRFT spectrometry shows that cyclohexanol is the only organic product obtained. The assessment of the hydrogen consumed and the quantitative chemical analysis of the mineral chlorine show that the transformation of the organic molecule into cyclic alcohol and NaCl is 100% complete

This example demonstrates that a chlorophenol insoluble in water, such as 2,4,6-trιchlorophéπol, can also be transformed into saturated alcohol and CI ions ^"

Example 8.

The procedure is as in Example 7 except that 2 g of 2,3,4,6-tetrachlorophenol are introduced into the autoclave in place of 2,4,6-tnchlorophenol and 1.36 g of sodium hydroxide after 1 hour stirring, sampling and analysis of the solution show that 2,3,4,6-tetrachlorophenol has transformed 100% into cyclohexanol and CI ^'

Example 9 The procedure is as in Example 7 to treat with hydrogen 2 g of peπtachlorophenol and 1.5 g of sodium hydroxide are added to the autoclave. 11 hours 30 minutes of stirring, 100% of the pentachlorophenol is transformed into cyclohexanol and CI ^"

Example 10: The procedure is as in Example 7 except that the autoclave is charged with 1 g of catalyst, 2 g of 2-chloroanilin in the place of chlorophenol and 0.62 g of sodium hydroxide. After 5 hours of stirring under 2.5 bar of hydrogen, the reagent has transformed into 60% cyclohexylamine and 40% cyclohexanol Chlorine has passed entirely to the NaCl state This example proves that the process described is capable to completely transform the aromatic soul into flavored products and sodium chloride

Example 1 1 The 2,4,6-trichlorophenol of Example 7 is replaced by 1 g of 4,4'-dichlorobiphenyl The mass of catalyst is 1 g and that of sodium hydroxide 0.36 g After 4 hours 20 minutes agitation, the autoclave is cooled and opened The balance sheet on the volume of hydrogen consumed and the IRFT spectrometry prove that the product has been transformed into bicyclohexyl and CI ^' This example shows that a dichlorobiphenyl can be hydrodechlorinated and transformed into hydrocarbon saturated with hydrogen in the presence of Ru / C under mild conditions of temperature and pressure

REFERENCES

1 Kovenklioglu, S, Cao, Z, Shah, D, Farrauto, R J and Balko, E N, AlChE, 38, 1003 (1992)

2 Kalnes, T N and James, R B, Envir Prog, 7, 185 (1988)

3 UOP Patent, US 4895995 (1990)

4 Allen, D T and coil, AlChe J, 37, 1730 (1991) and references cited

5 Fouilloux, P, Cordier, G and Colleuille, Y, Studies in Surface Science and Catalysis, 11, 369 (1982)

Claims

1. Process for the de-aromatization of organo-halogenated or organo-oxygenated aromatic compounds or both at the same time, by treatment of said compounds dissolved or in suspension in a solution, in particular aqueous, with hydrogen, in contact with a catalyst with base of ruthenium metal or any other alloy into which ruthenium can enter without losing its catalytic qualities 2. Method according to claim 1, characterized in that the solution containing said compounds is an alkaline aqueous solution 3. Method according to claim 1 or 2, applied to the hydrodeshalogenation of organo-halogenated, organo-halogenated and oxygenated aromatic compounds, characterized in that the aqueous alkaline solution comprises an alkali or alkaline-earth metal hydroxide, such as l potassium hydroxide KOH or calcium dihydroxide Ca (OH) ₂ , preferably sodium hydroxide NaOH, or an alkali or alkaline earth metal salt such as a decomposable carbonate in the presence of a halogen acid 4. Method according to any one of claims 1 to 3, characterized in that said aromatic compounds, in aqueous alkaline solution, are brought into contact with the ruthenium catalyst under a hydrogen pressure comprised in a range extending from atmospheric pressure to about 20 bar and at a temperature in the range from room temperature to about 100 ° C 5. Method according to claim 4, characterized in that it comprises a prior preactivation of the catalyst by heating to a temperature of at least 80 ° C, in particular when the aforesaid brought into contact is then carried out at a temperature below 80 ° C 6. Method according to claim 5, characterized in that it is carried out at ambient temperature, and under a hydrogen pressure approximately equal to 2.5 bars 7. Method according to any one of claims 1 to 6, characterized in that the ruthenium-based catalyst comprises ruthenium metal deposited on a support in the divided state, this support preferably also allowing adsorption of said organo-compounds. halogenated aromatics 8. Method according to claim 7, characterized in that the adsorbent support is selected from the group comprising activated carbon, silica, alumina, silica-alumina, magnesia, titanium oxide or a zeolite 9. Application of the method according to any one of claims 1 to 8 to the decontamination of effluents polluted by organohalogenated, oxygenated aromatic compounds, or both at the same time 10. Application according to claim 9, characterized in that, when the polluted effluents are non-basic, an alcahnization of said effluents is carried out, prior to decontamination 11. Application according to claim 9 or 10, characterized in that the effluents are, if necessary, previously concentrated so that the aromatic organo-halogenated compounds are at a concentration of between 100 ppm and 100,000 ppm 12. Application of the method according to any one of claims 1 to 8 to the production of compounds of the cyclan type, from organohalogenated, oxygenated aromatic compounds, or both 13. Application according to claim 12 for the production of oxygenated cyclanes, in particular cyclohexanol, from mono or polyhalogenated phenols or polychlorodioxins