Title of Invention

PROCESS FOR THE PREPARATION OF DINITRILES

Abstract

The present invention relates to a process for the preparation of dinitrile compounds by hydrocyanation of unsaturated mononitrile compounds in the presence of a catalytic system comprising an organometallic complex formed from a nickel element and from a mixture of organophosphorus ligands comprising at least one monodentate organophosphite compound and at least one bidentate organophosphorus compound chosen from the group consisting of organophosphites, organophosphinites, organo phosphonites and organophosphines, and optionally a promoter, the said prQcess comprising an hydrocyanation stage, a recovery stage of the catalytic system, characterized in that the' process consists in controlling the concentration of unsaturated nitriles in the reaction medium resulting from the hydrocyanation stage in order to obtain a concentration by weight of unsaturated nitriles of less than 20% in the said medium, in feeding the said medium to the recovery stage of settling into two upper and lower phases, and in separating the two phases, the lower phase being at least partially recycled to a hydrocyanation stage and the upper phase being subjected to a liquid/liquid extraction in order to extract the organometallic complex and the organophosphorus compounds present in the said phase.

Full Text

PROCESS FOR THE PREPARATION OF DINITRILES The present invention relates to a process for the preparation of dinitriles by hydrocyanation of unsaturated nitrile compounds in the presence of a catalyst based on a metal element in the zero oxidation state and on organophosphorus ligands. It relates more particularly to a process for the recovery from the hydrocyanation medium of a catalyst for the hydrocyanation of unsaturated nitriles to dinitriles. The hydrocyanation reaction is used industrially for the synthesis of compounds comprising nitrile function groups from compounds comprising unsaturations. Thus, adiponitrile, which is an important chemical intermediate, in particular in the manufacture of hexamethylenediamine, a monomer for a number of polymers, such as polyamide, is manufactured by hydrocyanation in two stages of butadiene or of a hydrocarbon cut, known as the C4 cut, comprising butadiene. In this manufacturing process, the two reactions are carried out with catalytic systems composed essentially of the same entities, namely an organometallic coordination complex and at least one organophosphorus ligand of monodentate organophosphite type, such as tritolyl phosphite. Numerous patents disclose this process for the manufacture of adiponitrile, and processes for the manufacture of the catalysts. Furthermore, for the economics of the process, it is important to be able to recover the catalytic system and to recycle it in the hydrocyanation stages. Thus, Patent US 4 539 302 discloses a process for the recovery of the catalyst from the reaction medium obtained in the second stage of the process of the preparation of adiponitrile, namely hydrocyanation of unsaturated nitriles to dinitriles. This process for recovery by settling makes it possible to limit the losses of metal element and facilitates the control of the organophosphorus ligand/metal element ratio, which is low for the hydrocyanation of unsaturated nitriles. Thus, it is also possible to recover a catalytic system with a high ligand/metal element ratio, which makes possible recycling and reuse of the catalytic system in stages for the manufacture of catalyst and/or in stages for the hydrocyanation of butadiene or the isomerization of branched pentenenitriles. Numerous other organophosphorus ligands have been provided for the catalysis of these hydrocyanation reactions. Thus, bidentate ligands of organophosphite, organophosphinite, organophosphonite and organo-phosphine type have been disclosed in numerous patents, such as, for example, Patents WO 99/06355, WO 99/06356, WO 99/06357, WO 99/06358, WO 99/52632, WO 99/65506, WO 99/62855, US 5 693 843, WO 96/1182, WO 96/22968, US 5 981 772, WO 01/36429, WO 99/64155 or WO 02/13964. Finally, provision has also been made, by Patent WO 03/11457, to use a mixture of mono- and bidentate ligands for the catalysis of hydrocyanation reactions. The use of such a mixture makes it possible to facilitate the synthesis of the catalyst and the formation of the organometallic complex, in particular with respect to processes for the synthesis of organometallic complexes with bidentate ligands. In the case of mixtures of ligands, it is also important to be able to recover the catalyst without losing ligands or metal element. One of the aims of the present invention is to provide, in a process for the preparation of dinitriles, a process for the recovery of a catalyst formed by a mixture of mono- and bidentate ligands and to be able to reuse the catalyst thus recovered in the hydrocyanation and/or isomerization stages. To this end, the invention provides a process for the preparation of dinitrile compounds by hydrocyanation of unsaturated mononitrile compounds in the presence of a catalytic system comprising an organometallic complex formed from a metal element and from a mixture of organophosphorus ligands comprising at least one monodentate organophosphite compound and at least one bidentate organophosphorus compound chosen from the group consisting of organophosphites, organophosphinites, organophosphonites and organophosphines, and optionally a promoter, the said process comprising a recovery of the catalytic system, characterized in that the process consists in controlling the concentration of unsaturated nitriles in the reaction medium resulting from the hydrocyanation reaction in order to obtain a concentration by weight of unsaturated nitriles of less than 2 0% in the said medium, in feeding the said medium to a stage of settling into two upper and lower phases, and in separating the two phases, the lower phase being at least partially recycled to the said hydrocyanation stage and the upper phase being subj ected to a liquid/liquid extraction in order to separate the organometallic complex and the organophosphorus compounds present in the said upper phase from the dinitriles. Mention may be made, as monodentate organophosphite ligand suitable for the invention, by way of examples, of triphenyl phosphite, tritolyl phosphite (TTP) or tricymenyl phosphite. Mention may be made, as bidentate ligands which are suitable for the invention, of the compounds with the following structures, in which Ph means phenyl: 5 generally comprises a number of moles of bidentate ligand, expressed as number of phosphorus atoms with respect to a metal element atom, of between 1 and 4, while that of monodentate ligand, expressed as number of phosphorus atoms, is between 4 and 7. In the present text, the expression "ligand/nickel" always refers to the ratio of all the molecules of mono- and/or bidentate ligands with respect to the number of nickel atoms, unless expressly indicated otherwise. The metal elements exhibiting a catalytic effect in a hydrocyanation reaction are, for example, nickel, cobalt, iron, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, zinc, cadmium or cerium. Nickel is the preferred catalytic element. For greater clarity, the metal element will be denoted by the term "nickel" in the continuation of the present text, without this being a limiting meaning. Furthermore, in the hydrocyanation reaction of the unsaturated nitriles, a promoter or cocatalyst is generally used. Lewis acids are generally used as preferred promoters. Use may in particular be made, by way of examples, of the Lewis acids cited in the work edited by G. A. Olah, "Friedel-Crafts and Related Reactions", Volume I, pages 191 to 197 (1963). The Lewis acids which can be employed as cocatalysts in the present process are advantageously chosen from compounds of the elements from Groups lb, I lb, Ilia, 11 lb, IVa, IVb, Va, Vb, VIb, VI lb and VIII of the Periodic Table of the Elements. These compounds are generally salts, in particular halides, such as chlorides or bromides, sulphates, sulphonates, haloalkylsulphonates, perhaloalkylsulphonates, in particular fluoroalkylsulphonates or perfluoroalkyl- suipnonates, naloacetates, perhaloacetates, carboxylates and phosphates. Mention may be made, as non-limiting examples of such Lewis acids, of zinc chloride, zinc bromide, zinc iodide, manganese chloride, manganese bromide, cadmium chloride, cadmium bromide, stannous chloride, stannous bromide, stannous sulphate, stannous tartrate, indium chloride, indium trifluoromethylsulphonate, indium trifluoroacetate, the chlorides or bromides of rare earth elements, such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, hafnium, erbium, thulium, ytterbium and lutetium, cobalt chloride, ferrous chloride or yttrium chloride. Use may also be made, as Lewis acid, of compounds such as triphenylborane or titanium tetraisopropoxide. It is possible, of course, to employ mixtures of several Lewis acids. Preference is very particularly given, among Lewis acids, to zinc chloride, zinc bromide, stannous chloride, stannous bromide, triphenylborane, indium trifluoromethylsulphonate, indium trifluoroacetate and zinc chloride/stannous chloride mixtures. The Lewis acid cocatalyst employed generally represents from 0.005 to 50 mol per mole of nickel. According to a preferred characteristic of the invention, the medium fed to the settling stage is cooled to a temperature of between 2 5°C and 75°C, advantageously between 30°C and 55°C. In order to obtain settling and separation into two phases of the reaction medium, it is advantageous for the concentration by weight of nickel in the reaction bn& £. 0 nsswJsd ed oJ 9pB3a pnxlJ39a 9ri3 oJ bsl muxb9m YBm 3x ,noxJBi^n9Dnoo I93to.cn B rfoua nxs:tdo oJ i9bio nl OX^Y-I^BO 1° 3nuomB nxB3i90 B bbB o3 Y^&a3909n 9d 9rf:t moil gnx:fxx9 muxb9m nox^D69i 9rto o;J m9^3YB noilsilnsonoo sdJ 9ajjBD9d ax axriT .9gB^a noxrtBnBYOOibYrf Lstioin 9riJ n9rfw muxb9m nox^DB9i srizf nx b9au l9:>toxn io 9d Y6m briBpxI 9jB^n9bxd 6 rtoiw nox^Bnxdmoo nx b9au ax 03 0 01 lo isbio srtl lo ,9lqmBX9 iol ,BB rioua xwoI Y^9V .muxb9m nox;JoB9i io p^t\l9^toxn lo pm 000S xnoi^n9vnx srlJ io dn9mxbodm9 b9ii9l9iq B or! pnxbioooA gnx:JlnB9i muxb9m 9ri3 nx l9:toxn io nox^Bi^n9onoo 9ri;J 9ldB^xua B od b9^an(;bB ax 9gB:ta noxdBnBYSOibYrf 9xi3 moil noxdioq B 33B9I 3B io noxzlouboiztnx Yd 9^IBV b9ixs9b has .9gBJa pnxlJ^sa 9riJ nx b9nxB^do 9aBriq i9woI 9rid io io ox;tax*x9:JoBiBrio bsiisieiq i9ri:Jon6 Je\ °3 pnxbioooA b9JBin^Banu io noxJ6idn9onoo 9ri:t vnoxJn9vnx 9ilJ ax 9gBJa pnxI^J9a 9ri3 o3 b9i muxb9m 9riJ nx 391 xiifxn Yl 3U0912B Jn&vbs x3ripx9w Y^ ^°£ Q:J -tfiJLrP9 ^o nBrf:t aa9l .:triiDX9w Y^ noxzJBi:tn9onoo B rioua io nox^ouboiq 9riJ io loiJnoo 9riT : aYBw 3n9^9iixb nx ;tuo b9xnso 9d nso 9rf:t 9nxi9b bns XoiJnoo o:J ax Y^-t-tdxasoq 331x1 A 9rf3 nx a9lx-xJxn b93Biu:JB3nu 9riJ io noiai9vnoo io 99ip9b 9riJ nx .fixB^do o3 i9bio nx 9£B3a noxztsnBYOoibYri pnxJxx9 io nox^OB9i 9ri:J io bn9 9ri:J JB muxb9m nox3oB9i b9^BiuJBanu io noi^Bi^aeonoo B ^IOJDSSI bi.se 9ri3 moil .Jripx9w Y^ ^°£ 0:* -tBup9 io nsri^ aa9l io 39lxi:3xn ,nox^n9vnx edJ lo 3n9mxbodm9 i9riJonB oJ pnxbioooA noxJBnBYOoibYri sdJ moil pnx:Jxx9 muxb9m nox:toB9i 9rid b9oub9i i9bnu nox^BlIx^axb lo 9£6:fa & o3 b9l ax 9£>B:fs b9^Biu^Banu b9zti9vnoonn 9riJ io pnxriaBll io siueasic sd3 loi^noo o:f 9ldxaaoq Jx 39?(Bm 9gBJa axriT .39lxi^xr: concentration of the unsaturated nitriles in the medium fed to the settling stage. To avoid losses of nickel by precipitation in the distillation bottoms, it is advantageous for the bottom temperature of this distillation stage to be less than 140°C. The term "distillation bottom temperature" is understood to mean the temperature of the medium which is found in the boiler but also the temperature of the walls of the said boiler. In this embodiment comprising the stage of distillation of a portion of the unsaturated nitriles, the adjusting or control of the concentration of nickel in the distillation bottoms fed to the settling stage can be carried out by recycling a portion of the lower phase from the settling. This recycling is advantageously carried out before feeding the medium to the distillation stage. According to the process of the invention, the lower phase obtained in the decanter or heavy phase comprises most of the nickel and of the bidentate ligand, and a portion of the monodentate ligand. However, as the coefficients for partition of the metal element and of the organophosphorus ligands between the two phases are different, the molar ratio of ligands/metal element atoms will be low in the lower phase and high in the upper phase. In addition, the process of the invention makes it possible to use most of the bidentate ligand preferentially in the stage of hydrocyanation of the unsaturated nitriles to thus obtain a high selectivity for linear dinitriles. According to another characteristic of the process of the invention, the upper phase recovered in the settling stage comprises a ligand/nickel molar ratio, expressed as number of phosphorus atoms, advantageously of greater than 8. According to the invention, the total recovery of the catalyst and of the ligands is carried out by a liquid/liquid extraction of these using an extraction solvent which is immiscible with the dinitriles. Mention may be made, as suitable extraction solvent, by way of examples, of saturated, linear or cyclic, aliphat i c hydrocarbons, such as hexane, heptane, octane, cyclohexane, cyclopentane, cycloheptane and more generally cycloparaffins or analogues. Cyclohexane is the preferred extraction solvent. After extraction, the cyclohexane solution of the organometallic complex and of the ligands is fed to a stage of evaporation or distillation of the extraction solvent. To limit the loss of nickel by precipitation, it is important for the ligand/nickel molar ratio, expressed as number of phosphorus atoms with respect to the number of nickel atoms, to be high and in particular greater than 8. This high ratio is, in the process of the invention, obtained in the settling stage by virtue of the coefficients of partition of the various chemical entities between the two upper and lower phases. In addition, in order to limit losses of nickel, the bottom temperature of the stage of distillation or evaporation at atmospheric pressure or under a pressure of greater than atmospheric pressure is advantageously less than 180°C. The term "bottom temperature" is understood to mean the temperature of the medium present in the boiler of the said stage and the temperature of the walls of the said boiler. The process for recovery of the catalyst of the invention thus makes possible complete recovery of the catalyst and of the organophosphorus ligands. The invention applies generally to a process for the conversion of unsaturated mononitriles to dinitriles which constitutes the second stage of a process for the manufacture of dinitrile compounds by double hydrocyanation of diolefins, such as butadiene. This process comprises a first stage of hydrocyanation of the diolefin to unsaturated nitriles carried out with a catalyst which is advantageously composed of the same compounds as those of the catalytic system used in the second stage with, possibly, different ratios between the compounds. This first stage is generally combined with an isomerization reaction of the branched mononitriles formed in order to convert them to linear unsaturated mononitriles which will be fed to the second stage. This isomerization is carried out with a catalytic system equivalent to that of the first stage and in the absence of hydrogen cyanide. In such a process comprising the two stages, the catalyst and the ligands recovered after evaporation of the extraction solvent are advantageously recycled, either in a stage of hydrocyanation of the diolefins (or of a C4 hydrocarbon cut) or in a stage of preparation of the catalyst, and/or to the isomerization of the branched unsaturated nitriles or alternatively added to the catalyst recovered from the lower settling phase before introduction into the stage of hydrocyanation of the unsaturated nitrile compounds. In one embodiment of the invention, at least a portion of the catalyst recovered after evaporation of the extraction solvent is introduced into the stage of isomerization of the branched nitriles and then optionally into the stage of hydrocyanation of the dienes. The catalyst recovered after the latter stage can be recycled directly in the liquid/liquid extraction stage. In this embodiment, the catalyst used in the isomerization stage and the stage of hydrocyanation of :he dienes comprises a low proportion of bidentate Ligand, thus making it possible to reduce the losses of :his ligand due, for example, to a hydrolysis reaction :>r to a reaction with compounds present in the dienes, such as tert-butylcatechol (TBC) present in butadiene. [•he present invention preferably applies to the lydrocyanation of linear or branched unsaturated litriles comprising from 3 to 8 carbon atoms and more preferably of 3-pentenenitrile and/or 4-pentenenitrile Eor the production of adiponitrile with use of a catalyst of the type represented by the following formula: Ni(Li)x(L2)y in which Lx represents a monodentate ligand and L2 a oidentate ligand, K and y represent decimal numbers ranging from 0 to 4, the sum x + 2y being equal to 3 or 4, The catalyst can be composed of a mixture of complexes corresponding to the above general formula. The catalytic system or the reaction medium can also comprise an amount of mono- and/or bidentate organophosphorus ligand in the free form, that is to say not bonded to the nickel. The catalytic systems of the invention can be obtained by formation, in a first stage, of an organometallic complex between the nickel and monodentate ligand. Processes for the formation of such complexes are, for example, disclosed in patents US 3 903 120 and US 4 416 825. In a second stage, the bidentate ligand is added to the medium comprising the said organometallic complex. The first and second hydrocyanation stages are advantageously carried out in series. In this case, it is advantageous for at least a portion of the catalyst recovered, in particular that recovered in the liquid/liquid extraction, and more particularly the catalyst recovered in the upper phase of the settling stage, to be recycled and used as catalyst in the first stage of hydrocyanation of butadiene and/or in the stage of isomerization of branched unsaturated nitriles to linear unsaturated nitriles. The use of an identical or similar catalytic system for the hydrocyanation of butadiene and that of pentenenitriles is preferred. However, it is also possible to use the catalytic system described above solely in the stage of hydrocyanation of unsaturated nitriles, the catalytic system used in the first stage of hydrocyanation of butadiene and the isomerization stage being different, either in the nature of the compounds or in the ratio between the various compounds. Other details and advantages of the invention will become more clearly apparent in the light of the examples given below solely by way of indication and illustration. Abbreviations: PN: pentenenitriles DN: dinitriles (mixtures of dinitriles AdN, MGN and ESN, predominantly comprising AdN) AdN: adiponitrile MGN methylglutaronitrile ESN: ethylsuccinonitrile Example 1: Hydrocyanation of pentenenitriles was carried out using a catalytic system comprising an organometallic complex obtained from nickel in the zero oxidation state, from a promoter ZnCl2 and from organophosphorus compounds with the following formulae: After flashing the PNs, the reaction medium obtained has the following composition (% expressed by weight; the ratios are molar ratios): Ni = 0.58% TTP/Ni = 5 Ligand A/Ni = 1.2 P/Ni = 7.4 DN = 64.0% PN = 6.4% ZnCl2 = 0.16% The mixture is cooled to 50°C: separation into two liquid phases is observed. The dense phase comprises approximately 83% of the Ni(0) and approximately 73% of the ligand A. The TTP/Ni ratio is approximately 3 in the lower phase and approximately 15 in the upper phase. The TTP/ligand A molar ratio is close to 8 in the upper phase. The upper phase, which comprises adiponitrile, is subjected to a liquid/liquid extraction with cyclohexane. The cyclohexane solution obtained is evaporated. The recovery of the catalytic system as residue from the evaporation is quantitative. Example 2: Settling of the TTP/ligand B mixed system Example 1 is repeated but replacing the ligand A by the ligand B with the following formula: After flashing the PNs, the reaction medium obtained has the following composition (% expressed by weight; the ratios are molar ratios): Ni = 0.70% TTP/Ni = 4 Ligand B/Ni = 1 P/Ni = 6 DN = 67.7% PN = 6.7% ZnCl2 = 0.17% The medium is cooled to 50°C: separation into two liquid phases is observed. The dense phase comprises approximately 70% of the Ni (0) and approximately 70% of the ligand B. The TTP/Ni ratio is less than 2 in the dense phase and approximately equal to 9 in the light phase. The TTP/ligand B ratio is close to 9 in the light phase. The upper phase is subjected to a liquid/liquid extraction with cyclohexane. The cyclohexane solution is evaporated. The recovery of the catalytic system as residue from the evaporation is quantitative. CLAIMS Process for the preparation of dinitrile compounds by hydrocyanation of unsaturated mononitrile compounds in the presence of a catalytic system comprising an organometallic complex formed from a metal element and from a mixture of organophosphorus ligands comprising at least one monodentate organophosphite compound and at least one bidentate organophosphorus compound chosen from the group consisting of organophosphites, organophosphinites, organophosphonites and organophosphines, and optionally a promoter, the said process comprising a recovery of the catalytic system, characterized in that the process consists in controlling the concentration of unsaturated nitriles in the reaction medium resulting from the hydrocyanation reaction in order to obtain a concentration by weight of unsaturated nitriles of less than 20% in the said medium, in feeding the said medium to a stage of settling into two upper and lower phases, and in separating the two phases, the lower phase being at least partially recycled to a hydrocyanation stage and the upper phase being subjected to a liquid/liquid extraction in order to extract the organometallic complex and the organophosphorus compounds present in the said phase. Process according to Claim 1, characterized in that the reaction medium is cooled to a temperature of between 25°C and 75°C before being introduced into the settling stage. Process according to either of Claims 1 and 2, characterized in that the concentration by weight of nickel in the medium fed to the settling stage is between 0.2 and 2%. Process according to one of the preceding claims, characterized in that the concentration by weight of unsaturated nit riles in the medium fed to the settling stage is between 4% and 20% by weight. Process according to one of the preceding claims, characterized in that the concentration of unsaturated nitriles in the reaction medium resulting from the hydrocyanation stage is less than 20% by weight. Process according to one of Claims 1 to 5, characterized in that the reaction medium resulting from the hydrocyanation stage is fed to a stage of distillation of the unsaturated nitriles, the distillation bottoms being fed to the settling stage. Process according to one of Claims 1 to 6, characterized in that the lower phase from the settling stage is at least partially recycled in the reaction medium resulting from the hydrocyanation. Process according to Claim 7, characterized in that a portion of the said lower phase is recycled in the reaction medium resulting from the hydrocyanation, before the stage of distillation of the unsaturated nitriles. Process according to one of the preceding claims, characterized in that the number of moles of bidentate ligand, expressed as number of phosphorus atoms with respect to a metal element atom, is between 1 and 4 in the hydrocyanation medium. Process according to one of the preceding claims, characterized in that the number of moles of monodentate ligand, expressed as number of phosphorus atoms with respect to a metal element atom, in the hydrocyanation medium is between 4 and 7 . Process according to one of the preceding claims, characterized in that the solvent used for carrying out the liquid/liquid extraction of the catalyst and of the organophosphorus compounds present in the upper phase is chosen from the group consisting of saturated or unsaturated, aliphatic or cycloaliphatic hydrocarbons. Process according to one of the preceding claims, characterized in that the catalyst and the organophosphorus ligands extracted in the liquid/liquid extraction stage are recovered by evaporation of the extraction solvent. Process according to Claim 11 and Claim 12, characterized in that the extraction solvent is chosen from the group consisting of hexane, heptane, octane, cyclohexane, cyclopentane and cycloheptane. Process according to one of the preceding claims, characterized in that the number of moles of organophosphorus ligands, expressed as number of phosphorus atoms, in the medium fed to the liquid/liquid extraction stage with respect to a metal element atom is greater than 8. Process according to one of the preceding claims, characterized in that the monodentate ligand is a compound chosen from the group consisting of triphenyl phosphite, tritolyl phosphite and tricymenyl phosphite. Process according to one of the preceding claims, characterized in that the bidentate organophosphorus ligand is chosen from the group consisting of organophosphites, organophosphonites, organophosphinites and organophosphines. Process according to Claim 16, characterized in that the bidentate organophosphorus ligand is chosen from the group consisting of the compounds with the following structures, in which Ph means phenyl: Process according to one of the preceding claims, characterized in that the catalytic system comprises a promoter or cocatalyst composed of a Lewis acid. Process according to Claim 18, characterized in that the promoter is chosen from the group consisting of compounds of the elements from Groups lb, lIb, IlIb, Illb, IVa, IVb, Va, Vb, VIb, Vllb and VIII of the Periodic Table of the Elements.chosen in the group comprising halides, sulphates, sulphonates, haloalkylsulphonates, perhaloalkylsulphonates, haloacetates, perhaloacetates, carboxylates, phosphates, arylboranes, fluoroalkylsulphonates and perfluoroalkylsulphonates. Process according to Claim 19, characterized in that the Lewis acid is chosen from the group consisting of zinc chloride, zinc bromide, zinc iodide, manganese chloride, manganese bromide, cadmium chloride, cadmium bromide, stannous chloride, stannous bromide, stannous sulphate, stannous tartrate, indium chloride, indium trifluoromethylsulphonate, indium trifluoro-acetate, the chlorides or bromides of rare earth elements, such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, hafnium, erbium, thulium, ytterbium and lutetium, cobalt chloride, ferrous chloride, yttrium chloride, triphenylborane, titanium tetraisopropoxide and their mixtures. Process according to one of Claims 6 to 20, characterized in that the column bottom temperature in the stage of distillation of the unsaturated nitriles is less than 140°C. Process according to one of the preceding claims, characterized in that the unsaturated nitrile is a linear or branched aliphatic compound comprising from 3 to 8 carbon atoms. Process according to Claim 22, characterized in that the unsaturated nitrile is a pentenenitrile. Process according to one of the preceding claims, characterized in that the catalytic system solution recovered after the stage of liquid/liquid extraction is subjected to distillation of the extraction solvent, the bottom temperature of this distillation being less than 180°C. Process for the manufacture of dinitrile compounds from diolefins, comprising a first stage of hydrocyanation of the diolefin to give unsaturated mononitriles, optionally an isomerization reaction of the branched unsaturated mononitriles formed in the first stage, and a second stage of hydrocyanation of the unsaturated mononitriles to give dinitrile compounds according to one of Claims 1 to 24. Process according to Claim 25, characterized in that the catalyst recovered from the upper phase of the settling stage is at least partially recycled in the isomerization reaction and/or to the first hydrocyanation stage. Process according to Claim 26, characterized in that the catalyst recovered from the upper phase of the settling stage is at least partially recycled in the isomerization reaction and then in the first hydrocyanation stage. Process according to Claim 27, characterized in that the catalyst recovered from the hydrocyanation medium of the first stage is fed to the settling stage or to the liquid/liquid extraction stage.

Documents:

2972-CHENP-2005 ABSTRACT.pdf

2972-CHENP-2005 CLAIMS GRANTED.pdf

2972-CHENP-2005 CORRESPONDENCE OTHERS.pdf

2972-CHENP-2005 CORRESPONDENCE PO.pdf

2972-CHENP-2005 FORM 1.pdf

2972-CHENP-2005 FORM 3.pdf

2972-CHENP-2005 PETITIONS.pdf

2972-chenp-2005-abstract.pdf

2972-chenp-2005-claims.pdf

2972-chenp-2005-correspondnece-others.pdf

2972-chenp-2005-description(complete).pdf

2972-chenp-2005-form 1.pdf

2972-chenp-2005-form 18.pdf

2972-chenp-2005-form 26.pdf

2972-chenp-2005-form 3.pdf

2972-chenp-2005-form 5.pdf

2972-chenp-2005-pct.pdf