FR2722709A1 - New hydrogenation catalysts for redn. of nitrile(s) to amine(s) - Google Patents

Abstract

Hydrogenation catalysts of the Raney-nickel-type doped with at least one element from gps. IIB, IVB or VIIB are new. The novelty is that dopant is not added to the alloy pre-cursor but during alkali treatment. Also claimed is the prepn. of the catalyst and use in the hydrogenation of nitriles to amines.

Description

CATALYST FOR HYDROGENATION OF NITRILES TO AMINES. ITS PROCESS

  PREPARATION AND PROCESS FOR HYDROGENATION USING THE SAME.

  The field of the invention is that of the catalytic reduction of nitriles to amines. More precisely, it is a question here of the catalytic hydrogenation of nitriles using catalysts of the Nickel type from RANEY, that is to say obtained by attack

  alkali of a Ni / AI precursor alloy.

  The present invention particularly relates to a catalyst for the hydrogenation of nitriles, in particular of dinitriles to diamines, said catalyst being of the RANEY nickel type doped with at least one element chosen from groups IIB, IVB to VIIB of the

periodic classification.

  The present invention also relates to a process for the preparation of a catalyst for the hydrogenation of nitriles into amines of doped RANEY type Ni, such as

the one referred to above.

  The present invention further relates to a process for the hydrogenation of

  nitriles to amines applying the catalysts considered above.

  Within the meaning of the invention, the term “nitriles” denotes all the aromatic and / or aliphatic mono and dinitriles and, in particular but not limited to, the dinitriles resulting from dicarboxylic acids, preferably from C3 to C6 such as adiponitrile, glutaronitrile, succinonitrile, malononitrile, optionally substituted by lower alkyl groups having from 1 to 6 carbon atoms, such as in particular

methyl or ethyl.

  RANEY nickels are catalysts widely used in industry and laboratories for hydrogenation reactions. They are prepared by alkaline attack of AI / Ni alloys rich in aluminum. The catalyst consists of agglomerates of nickel crystallites with a large specific surface and a content of

variable residual aluminum.

  In the field of catalysis in general and in hydrogenation catalysis in particular, the constantly aimed objectives are, on the one hand, the optimization of the activity and

  the selectivity of the catalyst with respect to the substrate to be hydrogenated and, on the other hand, the stability.

  It goes without saying that these three key parameters are inseparable from other constraints such as the ease of manufacture of the catalyst, its low cost price,

  as well as the flexibility and convenience of its implementation in hydrogenation.

  It has thus already been proposed to boost the nickel catalysts of RANEY using promoters such as titanium, chromium, iron, cobalt, copper, molybdenum, tantalum, zirconium or other metals, in order to improve their activity and / or their selectivity. The function of these promoters is to modify the electronic structural factors of RANEY nickel. Conventionally, they are added to the Ni / AI alloy in

  fusion, in accordance with a so-called "metallurgical" doping technique.

  The patent FR 913 997 describes in particular the use of a RANEY Ni, prepared from an AI / Ni alloy containing from 0.5% to 3.5% by weight of chromium relative to the

  nickel, for the hydrogenation of adiponitrile to hexamethylenediamine.

  The document B.N. TYUTYUNNIKOV et al - The Soviet Chemical Industry,

  NO 6, June 1991, as well as the article L.Kh FREIDLIN et ai - Russian Chemical Reviews -

  vol 33 NO 6 - June 1964, among others, relate to the catalytic reduction of aliphatic nitriles (dinitriles) using RANEY hydrogenation catalysts, promoted to

Using metal dopants.

  Such catalysts are relatively difficult to obtain, because they require the use of means for supplying and keeping the precursor alloy in fusion. In addition, the processes for obtaining these known catalysts are relatively inflexible, in particular with regard to the adjustment of the amount of dopants introduced into the alloy. Indeed, the mixture of the precursor alloy with the dopant may, sometimes, not be homogeneous and thus generate significant variations in composition or dopant content in the mass of the catalyst. It should also be noted that we do not control the phenomena that occur in the fade. We can thus witness, in certain cases, the formation of complex crystallographic structures, harmful to

  catalytic performance of the product.

  In addition, there are certain limitations as to the choice of the nature of the dopant in

  due to compatibility issues with nickel and molten aluminum.

  It should also be noted that some of the metallurgically doped Ni catalysts from RANEY do not always allow satisfactory results to be obtained.

  as for activity, selectivity and stability over time.

  It should also be noted that the known catalysts described by TYUTYUNNIKOV et ai as well as by FREIDLIN have relatively high residual aluminum contents, that is to say greater than 6% by weight. This is not to promote the performance of the catalyst. Finally, we observe that they are characterized by a relationship

  dopant / Ni weighting greater than 8%.

  The present invention aims to overcome the shortcomings and disadvantages of

  doped RANEY type hydrogenation catalysts of the prior art.

  It therefore aims to provide a RANEY Ni catalyst of doped hydrogenation, which is easy to prepare and inexpensive and which meets the requirements

  activity, selectivity and stability over time.

  Another objective of the invention is to provide a process for the preparation of a RANEY Ni catalyst for hydrogenation, which is simple and economical to use. Another object of the invention is to provide a process for hydrogenation in

  which uses a RANEY Ni catalyst of the type referred to above.

  The Applicant has had the merit of highlighting that it was necessary to carry out chemical doping of the precursor alloy during the alkaline attack, in order to reach

those goals.

  It follows that the subject of the present invention is a catalyst for the hydrogenation of nitriles into amines, of the Ni type from RANEY and doped with at least one element chosen from the elements of groups liB, IVB to VIIB of the periodic table, characterized in that its precursor alloy is substantially free of dopant before the alkaline attack. Within the meaning of the invention, the term "dopant" corresponds to a chemical element voluntarily added to the raw precursor alloy, immediately after its synthesis

  metallurgical, with a view to improving the catalytic properties.

  Such chemical doping brings a great simplification in obtaining the

  catalyst, as well as a significant improvement in the quality of catalysis.

  In particular, this new catalyst makes it possible to increase the productivity and the selectivity of the hydrogenation, while allowing a reduction in the rate of appearance.

  unwanted hydrogenation impurities or byproducts.

  According to another aspect of the invention, this catalyst comprises an aluminum content, expressed by weight relative to the weight of nickel, of less than or equal to 6%, preferably less than or equal to 5% and, more preferably still, included

between 2.5% and 4.5%.

  Advantageously, the dopant / Ni weight ratio of this catalyst is between 0.05% and 10%, preferably between 0.1% and 5% and, more preferably

again, between 0.3% and 3.5%.

  As regards the dopant, it is preferably chosen from the following elements: titanium, chromium, zirconium, vanadium, molybdenum, manganese, zinc. Titanium, chromium

  and zirconium are particularly preferred.

  In addition to nickel, aluminum and the dopant (s), the catalyst can contain metallic elements of constitution such as, for example, iron. This or these metallic elements of constitution are present in an amount less than or equal to 10%, preferably less than or equal to 7% and, more preferably still, less or

  equal to 5.5% by weight in the finished catalyst.

  The present invention also relates to a process for preparing a catalyst of the RANEY Ni type which can be used for the hydrogenation of nitriles into amines, said catalyst being doped with at least one element chosen from the elements of

  groups 11iB, IVB to VIIB of the periodic table.

  Conventionally, the preparation of a Nickel type catalyst by RANEY consists in subjecting a metal alloy comprising nickel and aluminum to a

  alkaline attack, leading to leaching of most of the aluminum.

  In accordance with the invention, the starting Ni / AI metal precursor alloy was not doped by the metallurgical route. It is therefore substantially virgin of element

metallic promoter.

  The precursor alloy is then alkaline attacked in the presence of the dopant

  in complexed form, which is intended to bind nickel chemically.

  The chemical doping according to the invention does not at all complicate the preparation

  traditional of a RANEY catalyst.

  In addition and quite surprisingly and unexpectedly, it appears that this simple process arrangement makes it possible to achieve a low-cost catalytic structure.

cost effective.

  In accordance with a preferred characteristic of the invention, the dopant is introduced into the alkaline attack medium, in the form of a solution, preferably alkaline and, more preferably still, of the same nature and substantially of the same alkaline content.

as the middle of attack.

  Advantageously, the vector used to transport the dopant and to bring it into contact with the precursor alloy is a complex of the dopant with at least one chelating agent. It may for example be a salt of the dopant, preferably soluble in the alkaline attack medium. The chelating agent used is preferably selected from carboxylic derivatives, trienes, amines or other suitable sequestrants. As regards the carboxylic acid derivatives, the following compounds are more readily chosen: tartrate, citrate, ethylenediaminetetraacetate, gluconate,

  fatty acid carboxylates such as stearate for example.

  In accordance with a particularly advantageous embodiment, tartrate is selected as the chelating agent for the chemical dopant (s).

Ni-AI alloy.

  The doping elements considered are the same as those defined above. Concerning the chronology of the process, the dopant is preferably introduced into the reactor from the start of the leaching and in practice at the same time as the alloy to be treated. Thus, in the case where the alkaline attack medium is constituted, for example, by 6N sodium hydroxide, the dopant in chelated form and also dissolved in 6N sodium hydroxide,

  is brought into the reaction medium simultaneously with the alloy.

  According to a variant implementation of the method according to the invention, the chemical doping is carried out using two metallic admission elements chosen from groups IIB, IVB to VIIB of the periodic table, preferably from

  following elements: titanium, chromium, zirconium, vanadium, molybdenum, manganese, zinc.

  The combination of titanium and chromium is particularly preferred.

  The amount of dopant used during the alkaline attack is a function of the final dopant concentration targeted in the catalyst. A person skilled in the art is perfectly capable of adjusting the titer of the alkaline dopant solution, taking into account the volumes used, the final concentration targeted by doping as well as the limit.

  of solubility of the dopant / chelating complex in the alkaline medium considered.

  It is in fact preferable that, under the reaction conditions, the doping / chelating complex is in solubilized form, when it is introduced into the

  alkaline attack reaction medium.

  Knowing that it is the solubility which fixes the upper limit of concentration of doping in the reaction medium, it can be indicated, to fix ideas, that this concentration is for example greater than or equal to 10-5 mol / liter and preferably

  greater than or equal to 10-3 mole / liter of reaction medium at 25 C.

  Apart from the introduction of dopant, the method according to the invention is assimilated to the conventional methodologies of alkaline attack of Ni-AI precursor alloy, to obtain a

  RANEY Ni catalyst for hydrogenation.

  This process is one of the possible techniques for preparing the new

  doped catalyst according to the invention and described above.

  The present invention also relates to a process for the hydrogenation of nitriles.

  in amines, in which the new catalyst according to the invention is used.

  This process applies, more particularly but not limitatively, to the nitrile substrates of formula (I):

NC-R-CN (I)

  in which R represents an alkylene or alkenylene group, linear or branched, having from 1 to 12 carbon atoms, or an arylene or aralkylene group or

substituted or unsubstituted aralkenylene.

  Preferably, in the process of the invention, dinitriles of formula (I) are used in which R represents an alkylene radical, linear or branched having

from 2 to 6 carbon atoms.

  As examples of such dinitriles, mention may be made in particular of adiponitrile, methylglutaronitrile, ethylsuccinonitrile, malononitrile, succinonitrile and glutaronitrile and their mixtures, in particular adiponitrile, methylglutaronitrile, ethylsuccinonitrile mixtures which originate from the same synthesis process

adiponitrile.

  The introduction of the nitrile substrate, for example adiponitrile, into the reaction medium is carried out while respecting a concentration of between 0.001% and% by weight relative to the total weight (w / w) of the reaction medium and preferably

between 0.1% and 20% w / w.

  In a privileged manner, the strong base used is chosen from the compounds

  following: LiOH, NaOH, KOH, RbOH, CsOH and their mixtures.

  In practice, NaOH and KOH are preferably used, for a good compromise

  price-performance, although RbOH and CsOH give even better results.

  The hydrogenation reaction medium is preferably liquid. It contains at least one solvent capable of dissolving the nitrile substrate to be hydrogenated, knowing that this

  transformation takes place better when said substrate is in solution.

  According to an advantageous method of the process according to the invention, an at least partially aqueous liquid reaction medium is used. Water is generally present in an amount less than or equal to 50%, advantageously less than or equal to% by weight relative to the total reaction medium. Even more preferably, the water content of the reaction medium is between 0.1 and 15% by weight relative to

  to all of the constituents of said medium.

  In addition to or in substitution for water, it is possible to provide at least one other solvent, of the alcohol and / or amide type. The alcohols which are more particularly suitable are for example methanol, ethanol, propanol, isopropanol, butanol, glycols, such as ethylene and / or propylene glycol, polyols and / or mixtures

of said compounds.

  In the case where the solvent consists of an amide, it may for example be

  dimethylformamide or dimethylacetamide.

  When used with water, the solvent, preferably alcoholic, represents from two to four parts by weight per one part by weight of water and preferably three

parts for a part of water.

  According to another preferred characteristic of the invention, amine is incorporated, the preparation of which is targeted by the process, within the reaction medium. It is by

  example of hexamethylenediamine, when the nitrile substrate is adiponitrile.

  The concentration of the amine targeted in the reaction medium is advantageously between 50% and 99% by weight relative to the totality of the solvent included in said reaction medium and, more preferably still, is between 60% and 99

% in weight.

  The amount of base in the reaction medium varies depending on the nature of the

reaction medium.

  As soon as the reaction medium contains only water and the targeted amine, as liquid solvent medium, the amount of base is advantageously greater than or equal to 0.1 mol / kg of catalyst, preferably between 0.1 and 2 mol / kg of

  catalyst and more preferably still between 0.5 and 1.5 mol / kg of catalyst.

  In the case where the reaction medium comprises water and an alcohol and / or an amide, the amount of base is greater than or equal to 0.05 mol / kg of catalyst, is preferably between 0.1 and 10, 0 mol / kg and more preferably still between

1.0 and 8.0 mol / kg.

  Once the composition of the reaction medium and the choice of catalyst have been stopped, these two elements are mixed, then this mixture is heated to a reaction temperature less than or equal to 150 ° C., preferably less than or equal

  at 120 C and, more preferably still, less than or equal to 100 C.

  Concretely, this temperature is between room temperature

(About 20 C) and 100 C.

  Beforehand, simultaneously or after heating, the reaction vessel is brought to a suitable hydrogen pressure, that is to say, in

  practical, between 0.10 and 10 MPa.

  The reaction time is variable depending on the reaction conditions and the

catalyst.

  In a discontinuous mode of operation, it can vary by a few minutes

several hours.

  In a continuous operating mode, which is perfectly conceivable for

  the method according to the invention, the duration is obviously not a fixed parameter.

  It should be noted that a person skilled in the art can modify the chronology of the steps of the process according to the invention, according to the operating conditions. The order given above does not

  corresponds to a preferred, but not limiting, form of the method according to the invention.

  The other conditions which govern the hydrogenation (in continuous or discontinuous mode) in accordance with the invention, fall under traditional technical provisions and

known in themselves.

  Thanks to all the advantageous arrangements mentioned above, the process of the invention makes it possible to hydrogenate nitrile substrates into amines, selectively,

fast, convenient and economical.

  The hydrogenation of adiponitrile to hexamethylenediamine is particularly important for producers of polyamide-6,6, since this hydrogenated derivative is one

  basic monomers of this large-scale industrial synthesis.

  The hydrogenation of dinitriles can also give access to aminonitriles.

  Thus, it is possible to hydrogenate only one of the two nitrile functions of adiponitrile to obtain aminocapronitrile. The latter compound is easily convertible by cyclizing hydrolysis to caprolactam, which is the starting product of another large

  industrial synthesis of polyamide, namely polyamide-6.

  It follows that this new hydrogenation catalyst which is simple to prepare, economical, more selective, more active and more stable than the known catalysts,

  represents significant and appreciable technical progress in this area.

  The invention will be better understood, its advantages as well as its variants of implementation will emerge from the examples which follow, of preparation of the new catalyst considered and of application thereof in the hydrogenation of adiponitrile to hexamethylenediamine.

EXAMPLES

  The starting precursor alloys come from four typical phases of the binary nickel-aluminum mixture: NiAI3, Ni2AI3, the eutectic AI / NiAI3 and a

proeutectic AI / NiAI3.

  The alloys used in the examples are as follows: - the commercial alloy Ni / AI = 50/50 by weight (mixture NiAI3 + Ni2AI3, eutectic AI / NiAI3); - a homogenized NiAI3 pure phase in which Ni / AI = 42/58 by weight; - a proeutectic casting stock in which Ni / AI = 28/72 by weight;

  - And a eutectic crude oil in which Ni / AI = 6/94 by weight.

  METHOD OF PREPARING A CHEMICALLY DOPED NOR RANEY CATALYST

1 OBTAINING DOPING SOLUTIONS

  1.1. Preparation of a solution of titanium tartrate + IV In a 500 ml beaker, 120 g of L.tartric acid are weighed. We add 340 g

  distilled water. The mixture is stirred until the solid has completely dissolved.

  The titanium tartrate is prepared in a purged glove box

several times with argon.

  To do this, a quantity of 12.59 g of TiCl4 is poured using a pipette into the tartaric acid solution. There is always a significant release of HCI with a TiO2 precipitate. The amount of TiCl4 introduced is weighed. The solution is very cloudy (white color). It is transferred to a 1000 ml flask and the volume is made up to 1000 ml by adding a 6N NaOH solution. The solution is still very cloudy. We wait a few hours for the balance to be established. After 6 hours, we

  has a clear solution at 3.16 g / I in Ti + IV.

  1.2. Preparation of chromium tartrate +111 In a 1000 ml Erlenmeyer flask, 140.16 g of L.tartaric acid are weighed. 267.72 g of distilled water are added. Stir to dissolve the solid. 15.09 g of chromium hydroxide acetate +111 (CH3CO2) 7 Cr3 (OH) 2 are then introduced with a spatula. Stir until the solid is completely dissolved. 6N sodium hydroxide is then added.

up to a volume of 1000 ml.

  The solution obtained has a titer of 3.90 g / I in Cr + III.

  2. PREPARATION OF THE NI RANEY CATALYST

  For the four types of Ni-AI precursor alloy used mentioned above, the following methodology is used: Step 1: 300 ml of 6N sodium hydroxide are introduced into a 2 I teflon flask.

ambient temperature.

  Step 2: We weigh 10.00 g of alloy in a beaker.

  Step 3: The alloy is then introduced using a spatula into the sodium hydroxide at a speed of g / h, ensuring that the average temperature of the medium does not

  not exceed 50 C (cooling by ice-water bath).

  Step 3a: Simultaneously, the alkaline solution containing the dopant is incorporated.

using a metering pump.

  Step 4: When all the alloy is introduced, we wait for the end of the effervescence

(5 min).

  Step 5: The mixture is heated at reflux (temperature = 108 ° C.) for 2 hours.

  Step 6: After 2 hours of reflux, the flask is removed from the flask heater and wait 5 min for the boiling to stop. We place a magnet under the ball

  and the supernatant is removed after decantation of the solid phase.

  Step 7: 300 ml of almost boiling 1 N sodium hydroxide (approximately 85 ° C.) are introduced and the flask is stirred 3 or 4 times. We then place a magnet under the balloon and

  the solid is allowed to settle. Finally, the supernatant is removed.

  Step 8: 300 ml of almost boiling 6N sodium hydroxide (approximately 85 ° C.) are introduced and

reflux for 2 hours.

Step 9: same as step 6.

  Step 10: same as step 7 but with 300 ml of "boiling" 6N sodium hydroxide.

  Step 11: same as step 7 but with 300 ml of "boiling" 3N sodium hydroxide.

  Step 12: same as step 7 but with 300 ml of "boiling" 2N sodium hydroxide.

  Step 13: same as step 7 but with 300 ml of 1N "boiling" soda.

  Step 14: The solid is collected in a flask and stored in cold 1N sodium hydroxide. The alkaline solution of step 3 bis can be that of Ti or Cr tartrate,

  the preparations are described in 1.1. and 1.2. above.

  The amount of alkaline doping solution used depends on the

  targeted final concentrations by doping.

  Thus, with 10 g of "commercial alloy", 55.6 ml of a solution of Ti tartrate in 6N sodium hydroxide at 3.6 g / I in Ti is used to obtain a final Ti / Ni ratio = 1, 20% in

weight in the finished catalyst.

  Various catalysts doped with Ti and / or Cr were thus prepared from

  different alloys, with different dopant / Ni concentrations in the finished catalyst.

  EXAMPLES 1 TO 25: HYDROGENATION OF ADIPONITRILE (DNA) IN

  HEXAMETHYLENEDIAMINE (HMD) USING CATALYSTS ACCORDING TO

  THE INVENTION AND COMPARATIVE TESTS 1 TO 4 USING CATALYSTS ACCORDING TO

PRIOR ART

  1. APPARATUS, PRODUCTS IMPLEMENTED AND METHODOLOGY

  1.1. Apparatus for discontinuous tests A 150 ml autoclave made of 316 L stainless steel is used. This autoclave is

  equipped with a magnetic stirring system (1500 rpm, magnetic bar and counter

  blades) ensuring good gas-liquid transfer. The heating is done by means of a thermoregulated heating sleeve. The substrate to be hydrogenated is introduced via a steel bulb above the autoclave; it can also be introduced

  using a high pressure pump in the case of a semi-continuous reactor.

  The hydrogen is stored at 5 MPa in a reserve provided with a pressure gauge connected to a recorder. It is relaxed in the assembly at the constant reaction pressure. The kinetics of the reaction are followed by recording the drop in pressure in the hydrogen reserve. Hydrogenate samples for analysis are taken

  via a dip tube fitted with a steel filter.

1.2. Products used

  - 99.99% adiponitrile (Rhône-Poulenc, PM = 108.15).

  - 99.99% hexamethylenediamine (Rhône-Poulenc, PM = 116.21).

  - Hydrogen U at 99.995% by volume.

- 99.8% ethanol.

- Distilled water

- 98% soda or 86% potash.

  - Catalyst: Raney nickel chemically doped according to the invention with Ti and / or Cr prepared as described above or metallurgically doped with Cr or undoped

according to the prior art.

  1.3. Conduct of a standard test 1.3.1. Charges

Adiponitrile: 6.0 g (0.0055 mole).

Hydrogen: excess (0.222 mole).

  Reaction medium: 42 g of reaction solvent [HMD / H2O / ethanol] + alkaline base [NaOH]; the alkaline base represents 0.10% by weight of the reaction medium; 42 g of reaction solvent [HMD / H2O] + KOH; alkaline base

  represents 0.05% by weight of the reaction medium.

Catalyst: 0.40 g.

  1.3.2. Procedure: Take an excess of Raney nickel slurry (1-2g), wash the catalyst with six times 50 ml of distilled water, weigh exactly 0.40 g of catalyst with

  pycnometer. The wet Raney nickel is then introduced into the autoclave.

  For a mass of 0.40 g of catalyst, the quantity of water currently entrained is of the order of 0.4 g. This mass of water will be taken into account in the weight composition of the reaction solvent of 60/30/10 in HMD / ethanol / water or 98/2 in HMD / water. The alkaline base is introduced with the quantity of water necessary for adjusting the percentages required. All of these manipulations must take place under an argon atmosphere to minimize the

  carbonation of the solvent and oxidation of the catalyst.

  The autoclave is then purged with nitrogen and hydrogen. And it is finally heated and maintained under 2.5 MPa of hydrogen. The recording of the pressure in the hydrogen reserve is started and the DNA is added quickly. When the hydrogen consumption becomes zero, the reactor is still left to stir for half an hour to better ensure the end of the reaction. At the end of the test, a sample of hydrogenate is taken to determine the selectivity. Initial activity and "average activity" are deducted from the curve

  of hydrogen consumption as a function of time.

2. ANALYSIS

  2.1. Measuring the activity The slope at the origin of the hydrogen consumption curve is proportional to the initial speed (Vi). This quantity is calculated by making the quotient at the origin of the number of moles of hydrogen consumed per unit of time reduced to the unit of mass of catalyst. The initial speed will be expressed in kmole of hydrogen

  consumed per kg of catalyst per second.

  For a good appreciation of the performance of a catalyst, it is necessary to know if the initial activity is not altered by premature aging. This is why we also measure the average reaction speed (Vm), which is the quotient of the number of moles of hydrogen involved in the total reaction time per unit.

  mass of catalyst per second.

  The reproducibility of the test for determining Vi and Vm gives an uncertainty

less than 10%.

  2.2. Measuring the selectivity At the end of the reaction, a sample of hydrogenate is taken and diluted approximately 40 times in isopropanol. This sample is quantitatively analyzed by gas chromatography (GC) using a semi-capillary column). The detector is flame ionization. Quantitative determination of reaction by-products

  DNA hydrogenation is carried out by the internal standard method (undecane).

  The list of the main by-products measured is given below: HMI: Hexamethyleneimine AMCPA: Aminomethylcyclopentylamine AZCHe: Azacycloheptene NEtHMD: N - ethylhexamethylenediamine DCH: Diaminocyclohexane cis and trans

BHT: Bis (hexamethylenetriamine).

  The selectivity (S) in HMD in percentage is given by the relation: 100 -

  sum of the selectivities of the by-products. Indeed the HMD being implemented in the

  reaction solvent, it cannot be directly dosed very precisely.

  On the other hand, it has been verified that the by-products are globally all identified.

  The selectivities in each of the by-products are represented by the molar percentage of the by-product formed relative to the transformed DNA. In all the examples and comparative tests carried out, the DNA transformation rate (thus

  than that of the intermediate aminocapronitrile) is 100%.

* When a compound does not reach its detection limit, the indication ND (not

  detected) will be entered in the results tables.

  The level of unsaturated present in the hydrogenate can be evaluated by polarography.

3. RESULTS

  3.1. Titanium doped Ni Raney catalysts

  Hydrogenation with HMD / H20 / ethanol / NaOH (examples there 16).

  Table 1 below collates the results obtained in these examples as well as in a comparative test (Ec) 1 using an undoped Raney Ni catalyst and the comparative tests (Ec) 2 and 3 using Raney Ni doped

metallurgically with chromium.

  3.2. Chromium doped RANEY Ni catalysts Hydrogenation with HMD / H20 / ethanol / NaOH (examples 17 to 20 and test

  comparison 4 with Ni de Raney metallurgically doped with Cr).

  3.3. Titanium and chromium doped Ni Raney catalysts

  Hydrogenation with HMD / H2O / ethanol / NaOH (examples 21 to 25).

  Table 2 below collates the results obtained in Examples 17 to 25 and shows on the one hand that chromium is a dopant just as advantageous as titanium and on the other hand that the use of two doping elements is , her too,

  quite advantageous, with regard to the selectivity and elimination of impurities.

  It is also noted that the metallurgically doped catalysts lead to selectivities in by-products, such as BHT, HMI in particular, higher than the

  chemically doped catalysts according to the invention.

  3.4. Titanium doped Raney Ni catalyst

  Hydrogenation with HMD / H20 / KOH (example 26).

  - starting alloy: Ni / AI = 50/50 by weight - 0.72% by weight of Ti / Ni in the catalyst

  - 3.25% by weight of Al / Ni in the catalyst.

  The following results were obtained - Vi = 46 -Vm = 4 - S in HMD: 98.0% - Sen HMI: 0.203% - Sen AzCHE: 0.191% - S in DCH: 0.046% - S in AMCPA: 0.489%

- S in BHT: 1.130%.

  Alloy Dopant AI / Ni S% in S% in S% in S% in S% in S% in S% in Tests AI / Ni% in% in Vi Vm HMD HMI AzCHe DCH AMCPA NEtHMD BHT% in w / w / Ni w / w cis + trans Ex 1 50/50 0.54 Ti 3.10 80 40 96.9 0.084 0.014 0.035 0.023 0.080 2.822 Ex 2 50/50 0.72 Ti 3.25 85 37 98.3 0.083 0.036 0.034 0.031 0.065 1,503 Ex 3 50/50 0.90 Ti 3.30 97 48 97.7 0.071 0.039 0.034 0.016 0.021 2.133 Ex 4 50/50 1.20 Ti 4, 00 118 56 98.5 0.055 0.040 0.072 0.033 0.063 1.199 Ex 5 50 / 50 1.75 Ti 4.40 123 59 98.3 0, 120 0.072 0.040 0.008 0.029 1.435 Ec 1 42/58 0 2.00 11 3 78.2 4.981 1.038 0.061 0.029 0.099 8.791 Ex 6 42/58 0.12 Ti 2.43 19 6 93.2 1.559 0.789 0.067 0.023 0.061 4.276 Ex 7 42/58 0.40 Ti 2.60 49 22 95.8 0.303 0.056 0.016 0.037 0.074 2.518 Ex 8 42/58 1.00 Ti 2.80 68 30 96, 4 0.100 0.015 0.016 0.033 0.069 2.539 Ex 9 42/58 1.50 Ti 2.80 93 41 97.0 0.182 0.050 0.025 0.032 0.058 2.149 Ln Ex 10 42/58 2.25 Ti 2.90 84 39 97.4 0.164 0.039 0.024 0.031 0.043 1.975 Ex 11 28/72 0.35 Ti 3.02 64 33 97.8 0.176 ND 0.022 ND 0.0 17 1.796 Ex 12 28/72 0.74 Ti 2.94 94 39 98.7 0.257 ND 0.076 ND 0.048 0.920 Ex 13 28/72 1.92 Ti 3.18 164 71 98.4 0.001 0.021 0.018 0.005 0.148 1.451 Ex 14 6/94 0.87 Ti 3.58 185 67 96.6 0.239 0.043 0.018 0.028 0.086 2.851 Ex 15 6/94 1.55 Ti 3.92 233 61 96.8 0.319 0.045 0.015 0.032 0.083 2.700 Ex 16 6 / 94 2.17 Ti 4.22 231 68 97.6 0.187 0.203 0.037 0.013 0.074 1.937 Ec 2 50/50 0.72 Cr 7.10 66 34 96.6 0.190 0.020 0.110 0.004 0.140 3.015 Ec 3 42/58 2 .90 Cr 8.05 32 12 96.2 0.310 1.260 0.120 0.032 0.064 2.025

Table 1

  Alloy Dopant AI / Ni S% in S% in S% in S% in S% in S% in S% in Tests AI / Ni% in% in Vi Vm HMD HMI AzCHe DCH AMCPA NEtHMD BHT% in wt wt / Ni pdscis + trans Ex 17 28/72 0.44 Cr 2.76 126 52 97.6 0.124 0.227 0.034 0.016 0.090 1.873 Ex 18 28/72 0.60 Cr 3.15 153 63 97.4 0.136 0.147 0.033 0.027 0.117 2.171 Ex 19 6/94 1.57 Cr 3.83 204 72 96.8 0.212 0.145 0.039 0.008 0.058 2.756 Ex 20 6/94 2.05 Cr 3.93 241 83 97.4 0.241 0.160 0.013 0.032 0.085 2.036 Ex 21 28/72 0.64 Ti 2.99 156 53 97.9 0.118 ND 0.006 ND ND 2.008 0.47 Cr Ex 22 28/72 0.89 Ti 3.10 166 88 97.6 0.158 0.004 0.025 0.009 0.174 2.005 0.24 Cr Ex 23 28/72 1.52 Ti 3.16 168 64 97.8 0.094 0.049 0.006 0.001 0.049 1.997 0.16 Cr Ex 24 6/94 0.80 Ti 3.87 219 62 97.1 0.288 0.345 0.037 0.018 0.074 2.105 1.13 Cr Ex 25 6/94 1.40 Ti 3.88 220 64 97.1 0.307 0.185 0.039 0.020 0.081 2.276 0.92 Cr Ec4 50/50 2.05 Cr 8.10 107 53 95.5 0.200 ND 0.084 0.014 0.070 3.100

Table 2

Claims (10)

  1 - Hydrogenation catalyst, of Raney Ni type and doped with at least one element chosen from groups 11B, IVB to VIIB of the periodic table, characterized in that its precursor alloy is substantially free of dopant before the alkaline attack.   2 - Catalyst according to claim 1, characterized in that it comprises an aluminum content, expressed by weight relative to the weight of nickel, less than or equal to 6%, preferably less than or equal to 5% and, more preferably still , between 2.5% and 4.5%.   3 - Catalyst according to one of claims 1 or 2, characterized in that the   dopant / Ni weight ratio is between 0.05% and 10%, preferably between   0.1% and 5%, and, more preferably still, between 0.3% and 3.5%.   4 - Catalyst according to one of claims 1 to 3, characterized in that the one or more   doping elements are chosen from the following: titanium, chromium, zirconium, vanadium, molybdenum, manganese, zinc and preferably from titanium, chromium and zirconium.   - Process for the preparation of a catalyst of the Raney Ni type usable for the hydrogenation of nitriles into amines, said catalyst being doped with at least one element chosen from the elements of groups IIB, IVB to VIIB of the periodic table, process in which is subjected to a metal alloy comprising nickel and aluminum to an alkaline attack, characterized in that it consists: - in using a metal alloy Ni / AI substantially free of dopant, - and in carrying out the attack alkali of the alloy in the presence of the dopant in complexed form. 6 - Process according to claim 5, characterized in that the dopant is introduced into the alkaline attack medium, preferably an alkaline solution and more preferably still of the same nature and substantially of the same alkaline title as the middle of attack.   7 - Method according to one of claims 5 or 6, characterized in that the element   dopant is in the form of a complex with at least one chelator, selected from derivatives of carboxylic acids, trienes, amines or other suitable sequestrants.   8 - Method according to one of claims 5 to 7, characterized in that the element   dopant is in the form of a complex with at least one chelator selected from the following compounds: tartrate, citrate, ethylenediaminetetraacetate, gluconate,   fatty acid carboxylates such as stearate, and is preferably a tartrate.   9 - Method according to one of claims 5 to 8, characterized in that the or the   doping elements are chosen from the following: titanium, chromium, zirconium, vanadium, molybdenum, manganese, zinc and preferably from titanium, chromium and zirconium.   - Method according to one of claims 5 to 9, characterized in that one   introduces the dopant at the start of the alkaline attack.   1 - Method according to one of claims 5 to 10, characterized in that one makes   intervene several dopants during the alkaline attack of the precursor alloy.   12 - Process for the hydrogenation of nitriles into amines, characterized in that one puts   using a catalyst according to one of claims 1 to 4, or the catalyst obtained   by the method according to one of claims 5 to 11.   13 - Process according to claim 12, characterized in that the nitrile substrate used is a dinitrile of formula (I): NC-R - CN (I)   in which R represents an alkylene or alkenylene group, linear or branched, having from 1 to 12 carbon atoms, or an arylene or aralkylene or aralkenylene group substituted or not, and preferably a nitrile of formula (I) in which R represents a alkylene radical,   linear or branched having from 2 to 6 carbon atoms.   14) - Method according to one of claims 12 or 13, characterized in that the   nitrile substrate is chosen from adiponitrile, methylglutaronitrile, ethylsuccinonitrile,   malononitrile, succinonitrile and glutaronitrile and their mixtures.   15) - Method according to any one of claims 12 to 14, characterized in   that the substrate, characterized in that the concentration of nitrile substrate in the total reaction medium is fixed at a value between 0.001% and 30% by weight   by weight and preferably between 0.1% and 20%.   16) - Method according to any one of claims 12 to 15, characterized in   which one uses a base constituted by at least one of the compounds   following: LiOH, NaOH, KOH, RbOH, CsOH.   17) - Method according to any one of claims 12 to 16, characterized in   that the liquid reaction medium comprises water, preferably in an amount less than or equal to 20% by weight of the total liquid reaction medium and, more   more preferably still, between 0.1% and 15% by weight.   18) - Method according to any one of claims 12 to 17, characterized in   that the liquid reaction medium contains targeted amine.   19) - Process according to claim 18, characterized in that the targeted amine is introduced into the liquid reaction medium, at a rate of 50 to 99% and preferably   at a rate of 60 to 99% by weight relative to the weight of the total liquid reaction medium.   ) - Method according to one of claims 12 to 19, characterized in that one   implements a liquid reaction medium comprising an alcohol such as methanol, ethanol, propanol, isopropanol, butanol, glycols such as ethylene glycol and / or propylene glycol, polyols and their mixtures and / or an amide such that the   dimethylformamide and / or dimethylacetamide.   21) - Method according to any one of claims 12 to 19, characterized in   what the base is used in an amount greater than or equal to 0.1 mol / kg of catalyst, preferably between 0.1 and 2.0 mol / kg of catalyst and, more   more preferably still, between 0.5 and 1.5 mol / kg of catalyst.   22) - Process according to claim 20, characterized in that the base is used in an amount greater than or equal to 0.05 mol / kg of catalyst, preferably between 0.1 and 10.0 mol / kg and , more preferably still, between 1.0 and 8.0 mol / kg.   23) - Method according to any one of claims 12 to 22, characterized in   that the hydrogenation is carried out at a reaction medium temperature of less than or equal to 150 ° C., preferably less than or equal to 120 ° C. and, more preferably   again, less than or equal to 100 C.   24) - Method according to one of claims 12 to 23, characterized in that the   dinitrile used is adiponitrile and in that the latter is converted into hexamethylenediamine.   25) - Method according to one of claims 12 to 23, characterized in that the   dinitrile used is adiponitrile and in that the latter is transformed into aminocapronitrile.