EP0287419A1 - Process for the electroreduction of aliphatic nitro derivatives - Google Patents
Process for the electroreduction of aliphatic nitro derivatives Download PDFInfo
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- EP0287419A1 EP0287419A1 EP88400751A EP88400751A EP0287419A1 EP 0287419 A1 EP0287419 A1 EP 0287419A1 EP 88400751 A EP88400751 A EP 88400751A EP 88400751 A EP88400751 A EP 88400751A EP 0287419 A1 EP0287419 A1 EP 0287419A1
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- aliphatic nitro
- electrochemical reduction
- nitro derivatives
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/25—Reduction
Definitions
- the present invention relates to an electro-reduction process of nitro derivatives.
- the yield does not exceed 80%; the side reactions are numerous leading to the formation of light amines and of heavy residue which must be separated from the desired amino alcohol, by several successive rectifications which result in a significant investment and consumption of energy; in addition, one cannot avoid the formation of N-CH3 derivative which is then difficult to separate from the desired amino derivative.
- Reaction (1) takes place at an electronegative potential close to -0.8 volts. It can therefore be implemented on a large number of materials with low hydrogen overvoltage such as stainless steel, copper, nickel.
- the reaction (2) on the contrary requires a potential close to or greater than -1.5 volts; it can only be carried out on materials with a high oxygen sustension in order to favor the reduction of the -NHOH group, with respect to that of the proton.
- the choice of material is then limited to four or five metals such as mercury, lead, zinc, cadmium, tin or carbon-based materials such as graphite and glassy carbon.
- the cathode consists of a support metal and an active element which, depending on the potential of the surface of the support metal, will either be in solution in the form of a cation, or reduced to a metal constituting a metallic deposit on the support metal.
- support metal is quite wide; it will be done among the elements for which the equilibrium potential M n + + ne ⁇ ⁇ Mo (3) is clearly less electro-negative than the potential of reaction (1) thus guaranteeing the inalterability of the support metal; in addition the support metal will be endowed with a high electrical conductivity; copper and nickel are particularly well suited.
- the active element will be chosen from among the elements for which the equilibrium potential of the reaction (3) is between the potentials reactions (1) and (2); in addition, when the active element is in the Mo state, the metal surface thus produced must be such that the hydrogen overvoltage there is as high as possible so that the reaction (2) is favored therein. proton reduction screw; finally, the active element, in the state (M n + ) must be soluble in the catholyte.
- Zinc and cadmium are elements well suited to this use.
- Zinc will preferably be chosen because of the low toxicity of the Zn++ cation.
- the method of electrochemical reduction of alphatic nitro derivatives is implemented with reactivation of the cathode.
- the active element has the property of changing state according to the potential of the support metal, and of being either in the form of a cation in solution in the catholyte or in the form of a metallic deposit on the support metal so that these transformations are obtained simultaneously with the successive reactions of reduction of the nitro derivative, they involve with each operation, a complete renewal of the electro-active surface with high hydrogen overvoltage.
- the electro-deposition of the active element on the support metal takes place under good conditions when the quantity of metal cation present in an operation is between 1 and 10 millimoles per dm2 of cathode, preferably 2 to 6 millimoles.
- a cell with two separate compartments is used.
- a copper cathode is immersed in an aqueous sulfuric solution of nitroalcohol in which a small quantity of soluble salts of zinc (Zn++), cadmium (Cd++) has been added; an electric current is established and maintained between the two electrodes such that the reduction reactions of the group -NO2 take place at a sufficient speed; the copper cathode then takes a potential which rises gradually with the evolution of the organic electro-reduction in -NHOH then -NH2 to a more electronegative value than the potential of equilibrium (3); the cation is then reduced and becomes a metallic deposit, constituting on the copper a surface with a high hydrogen overvoltage on which the reduction of the proton will be inhibited in favor of the transformation into amine of the hydroxyl amine group.
- the temperature of the catholyte can be between 10 and 100 ° C, preferably between 20 and 60 ° C.
- the density of the optimal cathode current is not very related to the transformation implemented; it will be chosen to obtain the maximum productivity of the device, taking into account the maximum current density, tolerable without deterioration by the membrane and the unit energy consumption, which largely depends on the geometric structure of the cell .
- nitro derivatives in particular to nitro-alcohols represented by the formula: wherein R1 and R2 together or separately are hydrogen, a hydroxyalkyl radical, such as hydroxymethyl, or a linear or branched alkyl radical, in particular, methyl, ethyl, propyl or containing a number of carbon atoms greater than three.
- a cell comprising three parallelepipedic compartments separated by two partitions composed of a cation-exchange membrane of the sulfonic type sold under the brand "Ionac 3470" (Company Ionac), consisting of a polypropylene support and cation-exchange sites, the cathode is placed in the central compartment and two anodes made of ruthenium titanium plate in the external anode compartments.
- Ionac 3470 Company Ionac
- the anolyte is a 20% sulfuric acid solution. We operate at constant intensity corresponding to a cathode current density of 10 A / dm2 (amperes per square decimeter). The load of material to be reduced is 150 millimoles of nitro derivative.
- the anolyte is stationary, while the catholyte is recycled, for the duration of the test, on an external circuit consisting of a peristaltic pump and a glass exchanger allowing thermal conditioning of the catholyte.
- the temperature of the catholyte is maintained between 20 and 30 ° C during the first stage in which it receives an effective quantity of electricity of 4 M / mole; then it is raised to 60 ° C.
- the progress of the reaction is monitored by potentiometric analysis of the catholyte which measures the contents of H+, R-NHOH, R-NH2; a semi-quantitative metric pH assay allows the presence or disappearance or nitro derivative to be ascertained.
- the cathode is a copper plate: its useful surface is 80 cm2; the interpolar voltage varies between 3 and 5 volts.
- the cathode is a copper plate cadmium-plated by conventional electroplating methods.
- test 2 a new copper plate is used and, in solution in the catholyte, at the start of the operation, 1 g of Cd++ is added in the form of cadmium sulphate previously dissolved: at the end of the operation , we see that the copper plate is covered with a gray deposit of metallic cadmium but quite irregular and not very adherent.
- test 3 the procedure is as in test 2, replacing the cadmium sulfate with zinc sulfate, and thus 580 mg of Zn++ is introduced; at the end of the operation, the copper plate is covered with a zinc deposit of more regular appearance, and more adherent than that of cadmium.
- the electrolyte is stopped periodically and the cathode is examined; at the first examination, carried out when the current used is around 3 F / mole, the cathode has found the characteristic red color of copper over almost its entire surface; after 4 F / mole, it resumed a uniform gray appearance characteristic of a cadmium deposit.
- the total cathode surface is 4 dm2; it consists of two copper plates 1 mm thick, slid into each of the cathode compartments; the anodes are made of platinum titanium.
- the anolyte is an 18% aqueous sulfuric solution.
- the nitroalcohol used is nitro-2-methyl-2-propanediol 1-3.
- Test 6 was carried out after test 5 without adding Zn++, the concentration given in the table resulting from an a posteriori assay by pickling and chemical analysis at the end of test 6; the same for test 7 compared to test 8.
- Av (RF> 95%) is the progress of the reaction expressed in the same unit, which was reached before the overall faradaic yield fell below 95%.
- nitropropane formylation product which mainly contains nitro-2-butanol-1 but also nitropropane and nitro-2-ethyl 2 propanediol 1-3.
- the results below are given relative to an average molecular weight of nitro derivative deduced from the following standard analysis: Nitrobutanol 86% Nitroethylpropanediol 11% Nitropropane 1% H2O 1.5%
- the energy consumption is 14.5 kwh.kg.
- the advancement rate, reached before the current yield falls below 95%, is 4.8 F / mole.
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Abstract
Description
La présente invention concerne un procédé d'électro-réduction de dérivés nitrés.The present invention relates to an electro-reduction process of nitro derivatives.
On connaît la réduction du groupement - NO₂ par le couple Fe-Fe⁺⁺ en milieu acide sulfurique ou acétique, mais le poids de réactif mis en oeuvre est d'environ trois fois celui du dérivé nitré à réduire ; il en résulte une grande quantité de résidu solide à éliminer et il est nécessaire de rectifier la phase liquide contenant l'amine pour obtenir un produit pur ; le rendement est de l'ordre de 80%.We know the reduction of the group - NO₂ by the Fe-Fe⁺⁺ couple in sulfuric or acetic acid medium, but the weight of reagent used is approximately three times that of the nitro derivative to be reduced; this results in a large amount of solid residue to be removed and it is necessary to rectify the liquid phase containing the amine in order to obtain a pure product; the yield is around 80%.
On peut aussi faire une hydrogénation catalytique, par exemple sur nickel de Raney en milieu méthanol sous 6 MPa à 40-45°C.It is also possible to carry out a catalytic hydrogenation, for example on Raney nickel in methanol medium at 6 MPa at 40-45 ° C.
Dans ce cas aussi, le rendement ne dépasse pas 80% ; les réactions secondaires sont nombreuses entrainant la formation d'amines légères et de résidu lourd qu'il faut séparer de l'amino-alcool recherché, par plusieurs rectifications succesives qui entrainent un investissement et une consommation d'énergie importante ; en outre, on ne peut éviter la formation de dérivé N-CH₃ qui est ensuite difficilement séparé du dérivé amino recherché.In this case too, the yield does not exceed 80%; the side reactions are numerous leading to the formation of light amines and of heavy residue which must be separated from the desired amino alcohol, by several successive rectifications which result in a significant investment and consumption of energy; in addition, one cannot avoid the formation of N-CH₃ derivative which is then difficult to separate from the desired amino derivative.
Un procédé de réduction électrochimique a déjà été décrit dans la brevet US 2.485.982 selon lequel on opère en solution aqueuse chlorhydrique ou sulfurique dans une cellule électrochimique munie d'un diaphragme poreux en porcelaine ; on obtient une solution aqueuse de chlorhydrate ou de sulfate d'amino-alcool qu'il faut ensuite neutraliser et/ou précipiter pour obtenir l'amine ; outre le dérivé matière première, on consomme l'acide et les réactifs de neutralisation ou de précipitation qu'il convient ensuite de rejeter dans l'environnement.An electrochemical reduction process has already been described in US Pat. No. 2,485,982 according to which one operates in aqueous hydrochloric or sulfuric solution in an electrochemical cell provided with a porous porcelain diaphragm; an aqueous solution of amino alcohol hydrochloride or sulphate is obtained which must then be neutralized and / or precipitated in order to obtain the amine; in addition to the raw material derivative, the acid and the neutralization or precipitation reagents are consumed which must then be discharged into the environment.
Dans la demande de brevet d'invention F 2.577.242 la déposante a décrit un procédé de réduction de nitro-alcools en amino-alcools dans une cellule à diaphragme dans laquelle les compartiments anodiques et cathodiques sont séparés par une membrane échangeur de cations ; le catholyte est constitué par une solution aqueuse sulfurique de nitro-alcool et l'anolyte par une solution d'acide sulfurique dilué.In patent application F 2,577,242 the applicant has described a process for reducing nitro-alcohols to amino-alcohols in a diaphragm cell in which the anode and cathode compartments are separated by a cation exchange membrane; the catholyte is constituted by an aqueous sulfuric solution of nitro-alcohol and the anolyte by a solution of dilute sulfuric acid.
Il est possible de représenteur globalement cette transformation par deux réactions :
- 1) RNO₂ + 4e- + 4H⁺→R- NHOH + H₂O
- 2) R NHOH + 2e- + 2H⁺→R- NH₂ + H₂O
- 1) RNO₂ + 4e- + 4H⁺ → R- NHOH + H₂O
- 2) R NHOH + 2e- + 2H⁺ → R- NH₂ + H₂O
La réaction (1) s'effectue à un potentiel électronégatif voisin de -0,8 volts. Elle peut donc être mise en oeuvre sur un grand nombre de matériaux à faible surtension d'hydrogène tels que l'acier inoxydable, le cuivre, le nickel.Reaction (1) takes place at an electronegative potential close to -0.8 volts. It can therefore be implemented on a large number of materials with low hydrogen overvoltage such as stainless steel, copper, nickel.
La réaction (2) au contraire exige un potentiel voisin ou supérieur à -1,5 volts ; on ne peut la réaliser que sur les matériaux à forte sustension d'oxygène afin de privilégier la réduction du groupement -NHOH, vis à vis de celle du proton. Le choix du matériau est alors limité à quatre on cinq métaux tels le mercure, le plomb, le zinc, le cadmium, l'étain ou des matériaux à base de carbone tels que le graphite et le carbone vitreux.The reaction (2) on the contrary requires a potential close to or greater than -1.5 volts; it can only be carried out on materials with a high oxygen sustension in order to favor the reduction of the -NHOH group, with respect to that of the proton. The choice of material is then limited to four or five metals such as mercury, lead, zinc, cadmium, tin or carbon-based materials such as graphite and glassy carbon.
Il a été obtenu de bons résultats sur le plomb et sur des amalgames de mercure, sur cuivre, nickel, et plomb.Good results have been obtained on lead and on amalgams of mercury, on copper, nickel, and lead.
Mais ce procédé présente divers inconvénients. On a constaté qu'il n'était pas possible d'éviter totalement la corrosion de la cathode, ce qui a pour conséquence de contaminer l'amino-alcool obtenu par des traces de cations toxiques, mercure ou plomb. De plus, on a observé une désactivation de la surface cathodique ; dans le meilleur des cas, cette désactivation se produit après quelques dizaines d'heures de fonctionnement et rend ainsi le procédé impropre à une exploitation industrielle.However, this process has various drawbacks. It was found that it was not possible to completely avoid corrosion of the cathode, which has the consequence of contaminating the amino alcohol obtained by traces of toxic cations, mercury or lead. In addition, deactivation of the cathode surface was observed; in the best of cases, this deactivation occurs after a few tens of hours of operation and thus makes the process unsuitable for industrial operation.
Il a été recherché un procédé de réduction électrochimique de dérivés nitrés du type nitroalcools, selon lequel les réactions chimiques correspondantes sont mises en oeuvre sur une cathode métallique, plongée dans le catholyte qui est une solution ou une émulsion sulfurique aqueuse ou aquo-alcoolique du dérivé nitro-alcool.An electrochemical reduction process for nitro derivatives of the nitroalcohols type has been sought, according to which the corresponding chemical reactions are carried out on a metal cathode, immersed in the catholyte which is a solution or an aqueous or aqueous-alcoholic sulfuric emulsion of the derivative. nitro alcohol.
La cathode est constituée d'un métal support et d'un élément actif qui, selon le potentiel de la surface du métal support sera soit en solution sous forme de cation, soit réduit en métal constituant un dépôt métallique sur le métal support.The cathode consists of a support metal and an active element which, depending on the potential of the surface of the support metal, will either be in solution in the form of a cation, or reduced to a metal constituting a metallic deposit on the support metal.
Le choix du métal support est assez large ; il sera fait parmi les éléments pour lesquels le potentiel d'équilibre
Mn+ + ne⁻ → Mo (3)
est nettement moins électro-négatif que le potentiel de la réaction (1) garantissant ainsi l'inaltérabilité du métal support ; en outre le métal support sera doué d'une conductibilité électrique élevée ; le cuivre et le nickel sont particulièrement bien adaptés.The choice of support metal is quite wide; it will be done among the elements for which the equilibrium potential
M n + + ne⁻ → Mo (3)
is clearly less electro-negative than the potential of reaction (1) thus guaranteeing the inalterability of the support metal; in addition the support metal will be endowed with a high electrical conductivity; copper and nickel are particularly well suited.
L'élément actif sera choisi parmi les éléments pour lesquels le potentiel d'équilibre de la réaction (3) est compris entre les potentiels des réactions (1) et (2) ; en outre, quand l'élément actif est à l'état Mo, il faut que la surface métallique ainsi réalisée soit telle que la surtension d'hydrogène y soit la plus élevée possible de façon que la réaction (2) y soit privilégiée vis à vis de la réduction du proton ; enfin, l'élément actif, à l'état (Mn+) doit être soluble dans le catholyte.The active element will be chosen from among the elements for which the equilibrium potential of the reaction (3) is between the potentials reactions (1) and (2); in addition, when the active element is in the Mo state, the metal surface thus produced must be such that the hydrogen overvoltage there is as high as possible so that the reaction (2) is favored therein. proton reduction screw; finally, the active element, in the state (M n + ) must be soluble in the catholyte.
Le zinc et le cadmium sont des éléments bien adaptés à cette utilisation.Zinc and cadmium are elements well suited to this use.
On choisira de préférence le zinc à cause de la faible toxicité du cation Zn⁺⁺.Zinc will preferably be chosen because of the low toxicity of the Zn⁺⁺ cation.
Selon l'invention, le procédé de réduction électrochimique de dérivés nitrés alphatiques est mis en oeuvre avec réactivation de la cathode. L'élément actif possède la propriété de changer d'état selon le potentiel du métal support, et d'être soit sous forme de cation en solution dans le catholyte soit sous forme de dépôt métallique sur le métal support de telle sorte que ces transformations étant obtenues simultanément aux réactions successives de réduction du dérivé nitré, elles entraînent à chaque opération, un renouvellement complet de la surface électro-active à forte surtension d'hydrogène.According to the invention, the method of electrochemical reduction of alphatic nitro derivatives is implemented with reactivation of the cathode. The active element has the property of changing state according to the potential of the support metal, and of being either in the form of a cation in solution in the catholyte or in the form of a metallic deposit on the support metal so that these transformations are obtained simultaneously with the successive reactions of reduction of the nitro derivative, they involve with each operation, a complete renewal of the electro-active surface with high hydrogen overvoltage.
L'électro-déposition de l'élément actif sur le métal support s'effectue dans de bonnes conditions quand la quantité de cation metallique présente dans une opération est comprise entre 1 et 10 millimoles par dm² de cathode, de préférence 2 à 6 millimoles.The electro-deposition of the active element on the support metal takes place under good conditions when the quantity of metal cation present in an operation is between 1 and 10 millimoles per dm² of cathode, preferably 2 to 6 millimoles.
La mise en oeuvre de l'invention peut être réalisée de la façon suivant donnée à titre d'exemple.The implementation of the invention can be carried out in the following manner given by way of example.
On utilise une cellule à deux compartiments séparés.A cell with two separate compartments is used.
Dans la première opération d'électrolyse, on plonge une cathode en cuivre dans une solution aqueuse sulfurique de nitroalcool dans laquelle on a ajouté une petite quantité de sels solubles de zinc (Zn⁺⁺), cadmium (Cd⁺⁺) ; on établit et on maintient entre les deux électrodes un courant électrique tel que les réactions de réduction du groupement -NO₂ s'effectuent à une vitesse suffisante ; la cathode du cuivre prend alors un potentiel qui s'élève progressivement avec l'évolution de l'électro-réduction organique en -NHOH puis -NH₂ jusqu'à une valeur plus électronégative que le potential de l'équilibre (3) ; le cation est alors réduit et se transforme en dépôt métallique en constituant sur le cuivre une surface à forte surtension d'hydrogène sur laquelle la réduction du proton sera inhibée au profit de la transformation en amine du groupement hydroxyl amine. Quand la réduction en amine est complètement terminée, on arrête le passage du courant ; on vidange le catholyte ; on le remplace par une nouvelle charge de solution sulfurique de dérivé nitré et on rétablit le passage du courant avec une intensité convenable ; au début de cette seconde opération, l'élément actif va passer en solution sous forme Zn⁺⁺ ou Cd⁺⁺ pour se redéposer à nouveau quand le potentiel de cathode aura atteint une valuer plus électronégative que le potentiel de l'équilibre (3).In the first electrolysis operation, a copper cathode is immersed in an aqueous sulfuric solution of nitroalcohol in which a small quantity of soluble salts of zinc (Zn⁺⁺), cadmium (Cd⁺⁺) has been added; an electric current is established and maintained between the two electrodes such that the reduction reactions of the group -NO₂ take place at a sufficient speed; the copper cathode then takes a potential which rises gradually with the evolution of the organic electro-reduction in -NHOH then -NH₂ to a more electronegative value than the potential of equilibrium (3); the cation is then reduced and becomes a metallic deposit, constituting on the copper a surface with a high hydrogen overvoltage on which the reduction of the proton will be inhibited in favor of the transformation into amine of the hydroxyl amine group. When the reduction in amine is completely finished, the flow of current is stopped; the catholyte is emptied; it is replaced by a new charge of sulfuric solution of nitro derivative and the flow of the current is restored with a suitable intensity; at the start of this second operation, the active element will go into solution in Zn Z or Cd⁺⁺ form to redeposit again when the cathode potential has reached a more electronegative value than the equilibrium potential (3) .
Ces alternances de mises en solution et dépôts électrochimiques entraînent, à chaque opération, un renouvellement complet de la surface électroactive qui, ainsi, conserve indéfiniment et intégralement son efficacité.These alternating solutions and electrochemical deposits cause, at each operation, a complete renewal of the electroactive surface which, thus, retains its effectiveness indefinitely and entirely.
Le même résultat est obtenu si, dans l'opération initiale, on utilise comme cathode une plaque de cuivre ou de nickel préalablement galvanisée ou cadmiée ; le dépôt métallique passe en solution sous forme de cations Zn⁺⁺ ou Cd⁺⁺ au début de l'opération puis le cation en solution est réduit on dépôt métallique simultanément à la transformation de l'hydroxyl amine en amine.The same result is obtained if, in the initial operation, a copper or nickel plate previously galvanized or cadmium plated is used as the cathode; the metal deposit goes into solution in the form of Zn⁺⁺ or Cd⁺⁺ cations at the start of the operation, then the cation in solution is reduced to a metal deposit simultaneously with the transformation of the hydroxyl amine into an amine.
La description de la transformation d'un dérivé nitré en dérivé aminé par l'intermédiaire des deux réactions successives (1 et 2) précitées semble pouvoir être considérée comme trop schématique. Il est généralement admis que la réaction (1) peut facilement être mise en oeuvre dans des conditions telles que le rendement du courant (rendement faradique RF) soit très élevé (RF = 95-100 %) ; et, dès que l'on fait réagir 4 F (faraday) par mole de dérivé nitré, la réduction devient moins aisée et l'efficacité instantanée du courant est fortement abaissée, de telle sorte que le rendement faradique global diminue d'autant plus rapidement que la quantité d'électricité efficace se rapproche de 6 F/mole correspondant à une conversion totale du dérivé nitré en fonction amine.The description of the transformation of a nitro derivative into an amino derivative via the two successive reactions (1 and 2) mentioned above seems to be considered too schematic. It is generally accepted that the reaction (1) can easily be carried out under conditions such that the current efficiency (faradic efficiency RF) is very high (RF = 95-100%); and, as soon as 4 F (faraday) is reacted per mole of nitro derivative, the reduction becomes less easy and the instantaneous efficiency of the current is greatly lowered, so that the overall faradic yield decreases all the more rapidly that the amount of effective electricity approaches 6 F / mole corresponding to a total conversion of the nitro derivative into an amine function.
Or, en opérant avec des matériaux de cathode à forte surtension d'hydrogène, notamment sur des cathodes cuivre-zinc ou cuivre-cadmium ci-dessus décrites, avec le milieu cathodique soumis à l'électrolyse ayant une composition telle que le rapport d'acidité H⁺/RX (RX = R-NO₂ + R-NHOH + R-NH₂) soit convenablement choisi, il a été constaté qu'il y a superposition des deux réactions d'électro-réduction organique et que la fonction amine apparaît bien avant que tout le dérivé nitré soit complètement transformé en hydroxylamine.However, by operating with cathode materials with a high hydrogen overvoltage, in particular on copper-zinc or copper-cadmium cathodes described above, with the cathode medium subjected to electrolysis having a composition such that the ratio of acidity H⁺ / RX (RX = R-NO₂ + R-NHOH + R-NH₂) is suitably chosen, it has been observed that there is a superposition of the two organic electro-reduction reactions and that the amine function appears long before all the nitro derivative is completely transformed into hydroxylamine.
Sur les cathodes Cu-Zn ou Cu-Cd, on constate qu'on peut obtenir un rendement faradique très élevé, voisin de 95-100% jusqu'à ce que la quantité de courant efficace soit de l'ordre de 5,2 - 5,8 F par mole de R-NO₂ initial ; ensuite l'efficacité instantanée du courant diminue rapidement ; on peut attribuer cela à la dilution de plus en plus élevée des molécules restant à réduire.On Cu-Zn or Cu-Cd cathodes, we see that we can obtain a very high faradaic yield, close to 95-100% until the effective current quantity is around 5.2 - 5.8 F per mole of initial R-NO₂; then the instantaneous efficiency of the current decreases rapidly; this can be attributed to the increasing dilution of the molecules remaining to be reduced.
L'efficacité du courant est étroitement liée à l'acidité du milieu défini par le rapport molaire H⁺/RX (RX = R-NO₂ + R-NHOH + R-NH₂) celui-ci doit être maintenu dans l'intervalle 1 à 1,5, de préférence rester voisin de 1,1 ; il faut veiller à ce qu'il reste constant pendant toute la durée de l'opération, en particulier à la fin de celle-ci.The efficiency of the current is closely linked to the acidity of the medium defined by the H⁺ / RX molar ratio (RX = R-NO₂ + R-NHOH + R-NH₂) which must be maintained in the interval 1 to 1.5, preferably remaining close to 1.1; care must be taken to ensure that it remains constant throughout the duration of the operation, in particular at the end of the operation.
La température du catholyte peut être comprise entre 10 et 100°C, de préférence entre 20 et 60 °C.The temperature of the catholyte can be between 10 and 100 ° C, preferably between 20 and 60 ° C.
La densité du courant cathodique optimale n'est pas très liée à la transformation mise en oeuvre ; elle sera choisie pour obtenir la productivité maximale de l'appareil, compte tenu de la densité de courant maximum, supportable sans détérioration par la membrane et de la consommation unitaire d'énergie, laquelle dépend pour une large part de la structure géométrique de la cellule.The density of the optimal cathode current is not very related to the transformation implemented; it will be chosen to obtain the maximum productivity of the device, taking into account the maximum current density, tolerable without deterioration by the membrane and the unit energy consumption, which largely depends on the geometric structure of the cell .
Le procédé est applicable aux dérivés nitrés, en particulier aux nitro-alcools représentés par la formule :
Parmi ces produits, ou trouve les dérivés nitrés conduisant à des alcanol-amines industriellement importants tels que l'amino-2 méthyl-2 propanol-1 ; l'amino-2 méthyl-2 propane diol-1,3, l'amino-2 éthyl-2 propane diol-1,3, le tris (hydroxyméthyl) aminométhane, l'amino-2 butanol -1.Among these products are found the nitro derivatives leading to industrially important alkanol-amines such as 2-amino-2-methyl-propanol-1; amino-2 methyl-2-propane diol-1,3, amino-2 2-ethyl-1,3-propane diol, tris (hydroxymethyl) aminomethane, 2-amino butanol -1.
Il est donné ci-après des exemples qui illustrent l'invention à titre non limitatif.Examples are given below which illustrate the invention without implied limitation.
Ces trois exemples ont pour objet la réduction du tris (hydroxyméthyl) nitrométhane en dérivé aminé correspondant.These three examples relate to the reduction of tris (hydroxymethyl) nitromethane to the corresponding amino derivative.
On utilise une cellule comportant trois compartiments parallélépipédiques séparés par deux cloisons composées d'une membrane échangeur de cations de type sulfonique vendue sous la marque "Ionac 3470" (Société Ionac), constituée d'un support en polypropylène et de sites échangeurs de cations, on place la cathode dans le compartiment central et deux anodes constituées de plaque en titane ruthénié dans les compartiments anodiques externes.A cell is used comprising three parallelepipedic compartments separated by two partitions composed of a cation-exchange membrane of the sulfonic type sold under the brand "Ionac 3470" (Company Ionac), consisting of a polypropylene support and cation-exchange sites, the cathode is placed in the central compartment and two anodes made of ruthenium titanium plate in the external anode compartments.
L'anolyte est une solution d'acide sulfurique à 20%. On opèra à intensité constante correspondant à une densité de courant cathodique de 10 A/dm² (ampères par décimètre carré). La charge de matière à réduire est de 150 millimoles de dérivé nitré. L'anolyte est stationnaire, tandis que le catholyte est recyclé, pendant toute la durée de l'essai, sur un circuit externe constitué d'une pompe péristaltique et d'un échangeur en verre permettant le conditionnement thermique du catholyte. La température du catholyte est maintenue entre 20 et 30 °C pendant la première étape dans laquelle il reçoit une quantité d'électricité efficace de 4 M/mole ; ensuite elle est élevée à 60°C.The anolyte is a 20% sulfuric acid solution. We operate at constant intensity corresponding to a cathode current density of 10 A / dm² (amperes per square decimeter). The load of material to be reduced is 150 millimoles of nitro derivative. The anolyte is stationary, while the catholyte is recycled, for the duration of the test, on an external circuit consisting of a peristaltic pump and a glass exchanger allowing thermal conditioning of the catholyte. The temperature of the catholyte is maintained between 20 and 30 ° C during the first stage in which it receives an effective quantity of electricity of 4 M / mole; then it is raised to 60 ° C.
On suit l'avancement de la réaction par analyse potentiométrique du catholyte qui mesure les teneurs en H⁺, R-NHOH, R-NH₂ ; un dosage pH métrique semi-quantitatif permet de constater la présence ou la disparition ou dérivé nitré.The progress of the reaction is monitored by potentiometric analysis of the catholyte which measures the contents of H⁺, R-NHOH, R-NH₂; a semi-quantitative metric pH assay allows the presence or disappearance or nitro derivative to be ascertained.
On arrête l'opération quand il ne reste plus ni hydroxylamine et, à fortiori, ni dérivé nitré dans la solution.The operation is stopped when neither hydroxylamine and, a fortiori, nor nitro derivative remains in the solution.
Selon la technique décrite dans la demande de brevet F 2.577.242, on peut ensuite traiter la solution de catholyte par électro-électrodialyse puis évaporer à sec et obtenir ainsi l'amino-alcool pur.According to the technique described in patent application F 2,577,242, it is then possible to treat the catholyte solution by electro-electrodialysis then evaporate to dryness and thus obtain pure amino alcohol.
Le bilan matière établi sur le catholyte en fin d'électrolyse fait apparaître une légère perte en matière organique dosable par potentiométrie. En tenant compte de cette perte, on calcule le rendement chimique de conversion de R-NO₂ en R-NH₂ et on obtient des valeurs variant entre 94-98 %.The material balance established on the catholyte at the end of electrolysis shows a slight loss in organic matter which can be measured by potentiometry. Taking this loss into account, the yield is calculated chemical conversion of R-NO₂ to R-NH₂ and values varying between 94-98% are obtained.
La cathode est une plaque de cuivre : sa surface utile est de 80 cm² ; la tension interpolaire varie entre 3 et 5 volts.The cathode is a copper plate: its useful surface is 80 cm²; the interpolar voltage varies between 3 and 5 volts.
Dans le tableau I ci-dessous, on donne les résultats obtenus :
Pour l'essai 1, la cathode est une plaque de cuivre cadmié par les procédés classiques de galvanoplastie.For test 1, the cathode is a copper plate cadmium-plated by conventional electroplating methods.
Dans l'essai 2, on utilise une plaque de cuivre neuve et on rajoute en solution dans le catholyte, dès le début de l'opération, 1 g de Cd⁺⁺ sous forme de sulfate de cadmium préalablement dissous : en fin d'opération, on constate que la plaque de cuivre est recouverte d'un dépôt gris de cadmium métallique mais assez irrégulier et peu adhérent.In test 2, a new copper plate is used and, in solution in the catholyte, at the start of the operation, 1 g of Cd⁺⁺ is added in the form of cadmium sulphate previously dissolved: at the end of the operation , we see that the copper plate is covered with a gray deposit of metallic cadmium but quite irregular and not very adherent.
Dans l'essai 3, on opère comme dans l'essai 2 en remplaçant le sulfate de cadmium par du sulfate de zinc, et on introduit ainsi 580 mg de Zn⁺⁺ ; en fin d'opération, la plaque de cuivre est recouverte d'un dépôt de zinc d'aspect plus régulier, et plus adhérent que celui de cadmium.In test 3, the procedure is as in test 2, replacing the cadmium sulfate with zinc sulfate, and thus 580 mg of Zn⁺⁺ is introduced; at the end of the operation, the copper plate is covered with a zinc deposit of more regular appearance, and more adherent than that of cadmium.
Dans un autre essai dans lequel la cathode est une plaque de cuivre préalablement cadmiée, on arrête l'électrolyte périodiquement et on examine la cathode ; au premier examen, effectué quand le courant utilisé est d'environ 3 F/mole, la cathode a retrouvé la couleur rouge caractéristique du cuivre sur presque toute sa surface ; après 4 F/mole, elle a repris un aspect gris uniforme caractéristique d'un dépôt de cadmium.In another test in which the cathode is a previously cadmium plated copper plate, the electrolyte is stopped periodically and the cathode is examined; at the first examination, carried out when the current used is around 3 F / mole, the cathode has found the characteristic red color of copper over almost its entire surface; after 4 F / mole, it resumed a uniform gray appearance characteristic of a cadmium deposit.
On utilise une cellule de laboratoire, type "filtre presse" à 5 compartiments constituée de deux compartiments cathodiques et trois compartiments anodiques séparés par des diaphragmes en membranes échangeur de cations de marque"IONAC 3470" ; les compartiments anodiques et cathodiques sont reliés respectivement à des dispositifs de recyclage et de conditionnement thermique des solutions (pompe péristaltique, échangeur en verre et récipient tampon en verre).We use a laboratory cell, type "filter press" with 5 compartments consisting of two cathode compartments and three anode compartments separated by diaphragms in cation exchange membranes brand "IONAC 3470"; the anode and cathode compartments are respectively connected to devices for recycling and thermal conditioning of the solutions (peristaltic pump, glass exchanger and glass buffer container).
La surface cathodique totale est de 4 dm2 ; elle est constituée de deux plaques de cuivre de 1 mm d'épaisseur, glissées dans chacun des compartiments cathodiques ; les anodes sont en titane platiné.The total cathode surface is 4 dm2; it consists of two copper plates 1 mm thick, slid into each of the cathode compartments; the anodes are made of platinum titanium.
L'anolyte est une solution aqueuse sulfurique à 18 %. Le nitroalcool utilisé est le nitro-2-méthyl-2-propanediol 1-3.The anolyte is an 18% aqueous sulfuric solution. The nitroalcohol used is nitro-2-methyl-2-propanediol 1-3.
On opère en maintenant la tension interpolaire entre 4 et 5,5 volts ; la densité de courant cathodique varie entre 40 A/dm² (début de l'opération) et 15 A/dm² (fin de l'opération) ; le tableau II ci-dessous donne les autres conditions opératoires et les résultats obtenus ; on y indique la densité de courant moyenne (Jc)
L'essai 6 a été effectué après l'essai 5 sans ajout de Zn⁺⁺, la concentration donnée dans le tableau résultant d'un dosage à posteriori par décapage et analyse chimique en fin de l'essai 6 ; de même pour l'essai 7 par rapport à l'essai 8.Test 6 was carried out after test 5 without adding Zn⁺⁺, the concentration given in the table resulting from an a posteriori assay by pickling and chemical analysis at the end of test 6; the same for test 7 compared to test 8.
Dans ce tableau (Av final) signifie avancement de la réaction au moment de l'arrêt de l'opération, c'est à dire la quantité de courant efficace exprimé en Faradays par mole de produit mis en oeuvre.In this table (Av final) means progress of the reaction when the operation is stopped, that is to say the amount of effective current expressed in Faradays per mole of product used.
Av (RF>95%) est l'avancement de la réaction exprimée dans la même unité, qui a été atteint avant que le rendement faradique global ne devienne inférieur à 95 %.Av (RF> 95%) is the progress of the reaction expressed in the same unit, which was reached before the overall faradaic yield fell below 95%.
Ces résultats montrent clairement l'effet de l'acidité, l'exemple 8 avec H⁺/RX = 1,1 donnant de meilleur résultat que l'exemple 6 pour lequel H⁺/RX = 1,3.These results clearly show the effect of acidity, Example 8 with H⁺ / RX = 1.1 giving better results than Example 6 for which H⁺ / RX = 1.3.
Dans la même cellule, on traite un produit de formylation du nitropropane et contenant principalement du nitro-2-butanol-1 mais aussi du nitropropane et du nitro-2-éthyl 2 propanediol 1-3. Les résultats ci-dessous sont donnés par rapport à un poids moléculaire moyen de dérivé nitré déduit de l'analyse type suivante :
Nitrobutanol 86 %
Nitroéthylpropanediol 11 %
Nitropropane 1 %
H₂O 1,5 %In the same cell, a nitropropane formylation product is treated which mainly contains nitro-2-butanol-1 but also nitropropane and nitro-2-ethyl 2 propanediol 1-3. The results below are given relative to an average molecular weight of nitro derivative deduced from the following standard analysis:
Nitrobutanol 86%
Nitroethylpropanediol 11%
Nitropropane 1%
H₂O 1.5%
On traite une solution aqueuse sulfurique contenant 3,9 moles/kg de dérivé nitré et un excès d'acide tel que le rapport molaire H⁺/RX = 1,15 ; la quantité en Zn⁺⁺, après mise en solution électrochimique, exprimée en mM (millimole) par dm2 de surface cathodique est de 5,8 ; la densité de courant cathodique moyenne est de 20,7 A/dm2. La tension interpolaire varie pendant l'opération entre 5 et 5,7 volts. Ces conditions opératoires permettent d'obtenir un rendement chimique molaire de 96,8 % et un rendement faradique global de 63 % pour un taux d'avancement en fin d'opération de 5,95 F/mole, ce qui correspond à la composition finale suivante de catholyte :
(R-NH₂) = 171,5 g/kg (R-NHOH) = 6,5 g/kgTreating an aqueous sulfuric solution containing 3.9 mol / kg of nitro derivative and an excess of acid such that the molar ratio H⁺ / RX = 1.15; the amount of Zn⁺⁺, after dissolving in electrochemical solution, expressed in mM (millimole) per dm2 of cathode surface is 5.8; the average cathodic current density is 20.7 A / dm2. The interpolar voltage varies during the operation between 5 and 5.7 volts. These operating conditions make it possible to obtain a molar chemical yield of 96.8% and an overall faradic yield of 63% for a rate of progress at the end of the operation of 5.95 F / mole, which corresponds to the final composition. following catholyte:
(R-NH₂) = 171.5 g / kg (R-NHOH) = 6.5 g / kg
La consommation d'énergie est de 14,5 kwh.kg.The energy consumption is 14.5 kwh.kg.
Le taux d'avancement, atteint avant que le rendement en courant ne devienne inférieur à 95%, est de 4,8 F/mole.The advancement rate, reached before the current yield falls below 95%, is 4.8 F / mole.
Claims (8)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT88400751T ATE63576T1 (en) | 1987-04-16 | 1988-03-29 | METHOD OF ELECTROREDUCTION OF ALIPHATIC NITRODERIVATIVES. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8705428 | 1987-04-16 | ||
| FR8705428A FR2614044B1 (en) | 1987-04-16 | 1987-04-16 | PROCESS FOR ELECTRO-REDUCTION OF ALIPHATIC NITERIUM DERIVATIVES |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0287419A1 true EP0287419A1 (en) | 1988-10-19 |
| EP0287419B1 EP0287419B1 (en) | 1991-05-15 |
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ID=9350207
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP88400751A Expired - Lifetime EP0287419B1 (en) | 1987-04-16 | 1988-03-29 | Process for the electroreduction of aliphatic nitro derivatives |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4830717A (en) |
| EP (1) | EP0287419B1 (en) |
| JP (1) | JPS63277781A (en) |
| AT (1) | ATE63576T1 (en) |
| CA (1) | CA1309968C (en) |
| DE (1) | DE3862795D1 (en) |
| ES (1) | ES2021847B3 (en) |
| FR (1) | FR2614044B1 (en) |
| GR (1) | GR3001948T3 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2917734A1 (en) * | 2007-06-19 | 2008-12-26 | Magnes Pierre Jean Maurice | "PROCESS FOR ELECTROCHEMIC CHEMICAL MIXING TREATMENT OF A LIQUID MEDIUM CHARGED WITH NITRATES, DEVICE FOR TREATING SUCH A LIQUID MEDIUM AND APPLICATIONS" |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2656605B1 (en) * | 1990-01-03 | 1992-03-13 | Air Liquide | PROCESS FOR THE PREPARATION OF AMINO-2-PROPANEDIOL-1,3 AND ITS SALTS. |
| US5250161A (en) * | 1991-01-24 | 1993-10-05 | Aerojet-General Corporation | Electrochemical desensitization process |
| KR100730460B1 (en) * | 2002-06-19 | 2007-06-19 | 에스케이 주식회사 | Method for preparing 2-amino-2-methyl-1,3-propanediol continuously using heterogeneous catalysts |
| CN115611751A (en) * | 2022-11-08 | 2023-01-17 | 四平欧凯科技有限公司 | Preparation method of tris (hydroxymethyl) aminomethane |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1185024A (en) * | 1956-10-31 | 1959-07-29 | Miles Lab | Process for the electrochemical transformation of nitrobenzene into para-aminophenol |
| EP0198722A2 (en) * | 1985-02-11 | 1986-10-22 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Process for the preparation of amino-alcohols by electrochemical reduction of nitro-alcohols |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2485982A (en) * | 1944-03-13 | 1949-10-25 | Commercial Solvents Corp | Electrolytic production of aminoalcohols |
-
1987
- 1987-04-16 FR FR8705428A patent/FR2614044B1/en not_active Expired - Fee Related
-
1988
- 1988-03-29 AT AT88400751T patent/ATE63576T1/en active
- 1988-03-29 ES ES88400751T patent/ES2021847B3/en not_active Expired - Lifetime
- 1988-03-29 DE DE8888400751T patent/DE3862795D1/en not_active Expired - Lifetime
- 1988-03-29 EP EP88400751A patent/EP0287419B1/en not_active Expired - Lifetime
- 1988-04-11 US US07/180,053 patent/US4830717A/en not_active Expired - Fee Related
- 1988-04-15 CA CA000564313A patent/CA1309968C/en not_active Expired - Lifetime
- 1988-04-15 JP JP63091881A patent/JPS63277781A/en active Pending
-
1991
- 1991-05-16 GR GR90401235T patent/GR3001948T3/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1185024A (en) * | 1956-10-31 | 1959-07-29 | Miles Lab | Process for the electrochemical transformation of nitrobenzene into para-aminophenol |
| EP0198722A2 (en) * | 1985-02-11 | 1986-10-22 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Process for the preparation of amino-alcohols by electrochemical reduction of nitro-alcohols |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2917734A1 (en) * | 2007-06-19 | 2008-12-26 | Magnes Pierre Jean Maurice | "PROCESS FOR ELECTROCHEMIC CHEMICAL MIXING TREATMENT OF A LIQUID MEDIUM CHARGED WITH NITRATES, DEVICE FOR TREATING SUCH A LIQUID MEDIUM AND APPLICATIONS" |
| WO2009004257A3 (en) * | 2007-06-19 | 2009-06-11 | R L Firmus Sa | Process for mixed chemical/electrochemical treatment of a liquid medium loaded with nitrates, device for treating such a liquid medium and applications. |
| AU2008270050B2 (en) * | 2007-06-19 | 2013-03-07 | Firmus S.A.M. | Process for mixed chemical/electrochemical treatment of a liquid medium loaded with nitrates, device for treating such a liquid medium and applications. |
| CN101815678B (en) * | 2007-06-19 | 2013-06-12 | 菲尔姆斯摩纳哥商业公司 | Process for mixed chemical/electrochemical treatment of a liquid medium loaded with nitrates, device for treating such a liquid medium and applications |
Also Published As
| Publication number | Publication date |
|---|---|
| ES2021847B3 (en) | 1991-11-16 |
| US4830717A (en) | 1989-05-16 |
| JPS63277781A (en) | 1988-11-15 |
| DE3862795D1 (en) | 1991-06-20 |
| GR3001948T3 (en) | 1992-11-23 |
| FR2614044B1 (en) | 1991-05-10 |
| FR2614044A1 (en) | 1988-10-21 |
| ATE63576T1 (en) | 1991-06-15 |
| EP0287419B1 (en) | 1991-05-15 |
| CA1309968C (en) | 1992-11-10 |
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