Process to prepare an aluminium salphen complex

Abstract

The invention is directed to a process to prepare an aluminium salphen complex by reacting (i) a diamine compound selected from the group of an optionally substituted benzene-1,2-diamine, an optionally substituted 2,3-diaminopyridine and an optionally substituted 3,4-diaminopyridine, (ii) an optionally substituted salicylaldehyde or an optionally substituted 2-hydroxy-1-naphthaldehyde and (iii) aluminium diacetate chloride in a liquid reaction mixture also comprising an alcohol and a base compound.

Description

[0001] PROCESS TO PREPARE AN ALUMINIUM SALPHEN COMPLEX

[0002] The invention is directed to a process to prepare an aluminium salphen complex. The invention is further directed to immobilise this aluminium salphen complex on carrier particles and the use of the immobilised aluminium salphen complex as a catalyst in a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide.

[0003] The use of carbon dioxide as a cheap and readily available C1 source in fine and bulk chemical production is attracting significant interest. One of such chemical production routes is the synthesis of cyclic carbonates from ring- strained epoxides and CO2. Cyclic carbonate products are used as a solvent as part of electrolytes in Li-ion batteries. Further they may be used as monomers for polycarbonate synthesis and non-isocyanate polyurethanes or as synthetic intermediates.

[0004] Various high pressure processes are known such as described in EP2431363. This publication describes a process performed at 20 bar in the presence of a tetra(n-butyl) phosphonium bromide catalyst.

[0005] There is a desire to perform this reaction at more ambient pressure conditions. A suited catalyst for this reaction at lower pressures comprises of a Lewis acid-base catalyst and a halogen salt as a source for a halide anion (X-). RAFIK RAJJAK SHAIKH ET AL: "Catalytic Strategies for the Cycloaddition of Pure Diluted, and Waste CO2 to Epoxides under Ambient Conditions", ACS CATALYSIS, part B, no. 1 , 5 January 2018 (2018-01 -05), pages 419-450, XP055671558 describes various of such catalyst for the cyclic carbonate synthesis starting from an epoxide and carbon dioxide. In this article metalorganic complexes are described as the Lewis acids which perform well as a catalyst in the presence of a halogen salt and especially tetra-n-butylammonium bromide (TBAB). Possible metals mentioned are aluminium, gallium, indium, iron, cobalt, nickel, zinc, titanium and / or bismuth. Further the oxo-dimer of a substituted salen aluminium complex is described as a possible Lewis acid.

[0006] Many of the reported catalyst systems have been tested for this reaction in a homogeneous reaction environment. For a commercial application it is advantageous to perform the reaction in the presence of a heterogeneous catalyst. This for example simplifies the separation of the catalyst and the formed cyclic carbonate.

[0007] W02009 / 109765 describes a process to prepare cyclic carbonate compounds from carbon dioxide and an epoxide compound using a heterogeneous catalyst system comprising an oxo-dimer of a substituted salen aluminium complex. This catalyst system requires a halogen ammonium salt such as tetra-n-butylammonium bromide (TBAB) to be present in order to be catalytically active. Systems involving such dissolved ammonium salt are however not advantageous because of issues with this compound in downstream processing units. This is apparently solved in this patent by immobilizing the salen aluminium complex on a silica carrier via a diethylammonium(propyl)ethyl group substituent on the phenyl group of the complex. The presence of this diethylammonium(propyl)ethyl group not only anchors the complex to the silica carrier but also functions as the ammonium salt. Tetra-n-butylammonium bromide (TBAB) is however still required to be added in order to activate the catalyst. A disadvantage is that it is found that tetra-n-butylammonium bromide leaches from the supported catalyst system.

[0008] A major problem with the catalyst as described in W02009 / 109765 is that the supported salen aluminium ligand is difficult to prepare requiring at least 9 synthesis steps. Some of these steps have a low yield resulting in an overall yield of less than 10% and large amounts of solvents are used in the synthesis process.

[0009] The object of the present invention is to provide a process to prepare an aluminium salphen complex in a more simple and efficient manner. This object is achieved by the following process. Process to prepare an aluminium salphen complex by reacting

[0010] (i) a diamine compound selected from the group of an optionally substituted benzene-1 ,2-diamine, an optionally substituted 2,3-diaminopyridine and an optionally substituted 3,4-diaminopyridine,

[0011] (ii) an optionally substituted salicylaldehyde or an optionally substituted 2- hydroxy-1 -naphthaldehyde and

[0012] (iii) aluminium diacetate chloride in a liquid reaction mixture also comprising an alcohol and a base compound.

[0013] Applicants found that an aluminium salphen complex can be prepared in a one step process when starting from a selected group of diamine compounds, an optionally substituted salicylaldehyde or an optionally substituted 2-hydroxy-1- naphthaldehyde and aluminium diacetate chloride (AI(OAC)2CI). Such a complex may find advantageous use as part of a catalyst in a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide. Further, this complex can be immobilised on carrier particles which in turn can be used as a catalyst in a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide.

[0014] The diamine compound is selected from the group of an optionally substituted benzene-1 , 2-diamine, an optionally substituted 2,3-diaminopyridine and an optionally substituted 3,4-diaminopyridine. Examples are1 ,2- diaminobenzene and preferably 3,4-diaminopyridine. Preferably the diamine compound is 3,4-diaminopyridine.

[0015] The optionally substituted salicylaldehyde or the optionally substituted 2- hydroxy-1 -naphthaldehyde is suitably substituted with an alkyl group on the 3 position. This alkyl group may be methyl, ethyl, isopropyl and more preferably tert.-butyl. The salicylaldehyde and the 2-hydroxy-1 -naphthaldehyde may also be substituted with an electron withdrawing groups, such as a halogen group or with a nitro group. Examples of such halogen groups are chloride and bromide groups. The liquid reaction mixture comprises of an alcohol, preferably an aliphatic alcohol which may be any mono, di or tri aliphatic alcohol. Di and tri alcohols which are reactive with the aldehyde groups are preferably not used. These are for example ethylene glycol, glycerine and 1 ,3-propandiol. It is believed that the close proximity of the hydroxyl groups make these alcohols less suited. Preferably at least four carbon atoms are present between the hydroxyl groups such as in 1 ,4-butanediol and 1 ,5-pentanediol which are found to be effective alcohols. Examples of suitable mono aliphatic alcohols are methanol (MeOH), ethanol (EtOH), butanol, isopropanol and 1 -propanol or their mixtures.

[0016] The liquid reaction mixture comprises a base compound and preferably an organic base compound. Possible organic base compounds are N,N- diisopropylethylamine (DIPEA, Hunig base), tributyl amine (BU3N), Lutidine, potassium tert, butoxide (KOtBu), sodium tert, butoxide (NaOtBu), lithium tertbutoxide (LiOtBu) and potassium acetate. A preferred base compound is triethylamine (Et3N), and potassium acetate (KOAc).

[0017] In the reaction mixture the molar ratio between aluminium diacetate chloride and the diamine compound is suitably between 1 :1 and 2:1 .

[0018] In the reaction mixture the molar ratio between the base compound and the diamine compound is suitably between 2.7: 1 and 6:1.

[0019] The process can be performed at ambient pressures. The temperature of the reaction mixture may be between 10 and 100 °C and is suitably between 50 and 70 °C. The process may suitably be performed at the boiling point of the alcohol. When the salicylaldehyde or the 2-hydroxy-1 -naphthaldehyde is substituted with an electron withdrawing groups, such as a halogen group or with a nitro group it is found that good results are obtained when the temperature is closer to an ambient temperature, i.e. between 10 and 30 °C. The pressure is preferably ambient pressure. The pressure may be higher but it is preferred to operate at pressures at ambient or close to ambient in order not to introduce complexity into the process.

[0020] The concentration of the diamine compound in the liquid reaction mixture is suitably between 0.5 and 0.9 mol / L.

[0021] In an preferred embodiment the aluminium diacetate chloride is gradually added to a mixture of the diamine compound, the optionally substituted salicylaldehyde, the base compound and the alcohol. The aluminium diacetate chloride is preferably added as dissolved in part of the alcohol. The aluminium diacetate may also be dissolved in a mixture of the alcohol and for example ethyl acetate, which mixture may be directly obtained in a previous synthesis step as will be explained below. When adding the aluminium diacetate chloride the reaction mixture is stirred.

[0022] When reference is made to aluminium diacetate chloride also a possible dimer of aluminium diacetate chloride is meant. The aluminium diacetate chloride is not a readily available chemical. It may be prepared by reacting diethylaluminium chloride with acetic acid. A problem with diethylaluminium chloride is that it is pyrophoric. Mehrotra, R. C.; Misra, R. A. Canadian Journal of Chemistry (1964), 42(4), 717-23 describes the preparation of aluminium diacetate chloride by reacting a less pyrophoric aluminium trichloride with butyl acetate in a benzene solvent or in an excess of butyl acetate which acts as a reagent and solvent. The experiments performed in benzene were highly exothermic and required active cooling. After evaporating of the solvent and the formed butyl chloride, aluminium diacetate chloride was obtained as a white powder. The experiments performed in an excess of butyl acetate resulted in the preparation of aluminium triacetate or mixtures of aluminium diacetate chloride and aluminium triacetate.

[0023] Applicants have developed an improved process to prepare aluminium diacetate chloride by reacting aluminium trichloride with an alkali acetate in a liquid reaction mixture comprising an alcohol and an organic acetate to obtain aluminium diacetate chloride and a solid alkali chloride salt as a by-product. This process avoids the use of benzene as a solvent and enables one to prepare aluminium diacetate chloride starting from the more available aluminium trichloride. A next advantage is that no organic chloride compounds are formed as a by-product. These compounds are normally considered a difficult to dispose chemical waste. Instead an alkali salt is obtained which is considered to be a easier to dispose compound. Because the alkali chloride salt is obtained as a solid an easy separation, for example by centrifugal forces or by filtration, is possible. The filtrate or supernatant can be further worked up by evaporating the solvent after which aluminium diacetate chloride is obtained as a white powder. Applicants found that the aluminium diacetate chloride as prepared by this process can be advantageously be used to prepare the aluminium salphen complex according to the process of this invention. This solid aluminium diacetate chloride can be advantageously used in the process to prepare an aluminium salphen complex. The obtained filtrate or supernatant can also be directly used in the process to prepare the aluminium salphen complex without further purification or work-up. The invention is thus also directed to the following process.

[0024] Process to prepare an aluminium salphen complex by performing the following steps:

[0025] (a) reacting aluminium trichloride with sodium acetate or potassium acetate in a liquid reaction mixture comprising an alcohol and an organic acetate to obtain aluminium diacetate chloride and a solid sodium chloride salt or solid potassium chloride salt as a by-product and wherein the molar ratio of aluminium trichloride and sodium acetate or potassium acetate is between 1 :1.5 and 1 :3,

[0026] (b) separating the sodium chloride or the solid potassium chloride salt from the reaction mixture obtained in step (a), suitably by means of filtration, to obtain a liquid, i.e. a filtrate in case of filtration, comprising the aluminium diacetate chloride and poor in solid sodium chloride salt or potassium chloride salt, and

[0027] (c) performing the process of this invention using the liquid comprising aluminium diacetate chloride. Preferably in step (c) the filtrate is gradually added to a mixture of the diamine compound, the optionally substituted salicylaldehyde, the base compound and the alcohol while stirring.

[0028] The alcohol in step (a) may be methanol, ethanol, 1 -propanol, 2- propanol, 1 -butanol, 2-butanol or their mixtures. More preferably the alcohol is a primary alcohol selected from methanol or ethanol or a secondary alcohol having 3 to 5 carbon atoms. Higher yields to the desired aluminium salphen complex may then be obtained. A preferred alcohol is ethanol because potassium acetate has a high solubility in ethanol and the formed potassium chloride salt has a low solubility in ethanol and a high yield to the desired aluminium salphen complex is obtained. The organic acetate is preferably a linear alkyl acetate and may be methyl acetate, ethyl acetate, propyl acetate or butyl acetate. Non-linear alkyl acetates are less preferred because they react with aluminium trichloride. A preferred acetate is ethyl acetate because aluminium trichloride has a good solubility in ethyl acetate. Preferably the alcohol and organic acetate in the solvent mixture correspond. For example a preferred combination is ethanol and ethyl acetate.

[0029] The volume ratio of the alcohol and the organic acetate in the solvent is preferably between 0.5 : 1 and 5 : 1

[0030] The alkali acetate is sodium acetate or potassium acetate, and more preferably potassium acetate. It has been found that the formed potassium chloride or the sodium chloride is substantially present in its solid form in the reaction mixture, enabling easy separation from the reaction mixture. Thus when potassium acetate is used, potassium chloride is obtained as a solid byproduct which can be suitably separated from the reaction mixture. In step (b) the solid alkali salt is separated by filtration. In the filtration, the filtrate is suitably washed with an alcohol and preferably with the same alcohol as present in the solvent in step (a).

[0031] The reaction between aluminium trichloride and the sodium acetate or potassium acetate compound is exothermic. The temperature is suitably kept below the boiling temperature of the solvent mixture. Preferably the temperature at which the reaction is performed is between 10 °C and the boiling point of the solvent mixture.

[0032] The molar ratio of aluminium trichloride and the alkali acetate compound is suitably between 1 :1.9 and 1 :2.5 and even more preferably between 1 :2 and 1 :2.4.

[0033] Preferably the aluminium trichloride is first dissolved in the organic acetate to obtain an aluminium trichloride-organic acetate mixture. Dissolving aluminium trichloride in the organic acetate is exothermic and the temperature is preferably kept below 60 °C by cooling. The addition is preferably performed gradually to avoid excessive temperature rise. The concentration of the aluminium trichloride in the obtained aluminium trichloride-organic acetate mixture is preferably between 0.5 and 3 mol / L.

[0034] This aluminium trichloride-organic acetate mixture is subsequently added to a mixture of the alkali acetate and the alcohol. The concentration of the alkali acetate in the mixture of the alkali acetate and the alcohol is preferably between 0.5 and 3 mol / L. This addition is also exothermic and the temperature is preferably kept below 80 °C by cooling and more preferably between 20 and 60 °C. The aluminium trichloride-organic acetate mixture is preferably added gradually to the mixture of the alkali acetate and alcohol to avoid excessive temperature rise. The alkali acetate and alcohol mixture may be a slurry wherein the alkali acetate is the solid phase.

[0035] After adding the aluminium trichloride-organic acetate mixture to the mixture of the alkali acetate and the alcohol the resulting mixture is stirred to allow the reaction to aluminium diacetate chloride. This phase may continue for between 2 and 18 hours. The temperature is preferably maintained between 25 and 50°C. Preferably this phase is continued until all or substantially all of the aluminium trichloride has reacted. In step (b) the formed solid alkali chloride salt is separated from the reaction mixture obtained in step (a). This separation may be by means of centrifugal forces and suitably by means of filtration. The obtained liquid poor in solid alkali chloride salt may advantageously be used as such in step (c) in a so-called telescoping synthesis. This is preferred because it avoids isolating the aluminium diacetate chloride from this mixture and using the isolated aluminium diacetate chloride in step (c).

[0036] The liquid poor in solid alkali chloride salt as obtained in step (b) may be used a such in step (c). In such a telescoping synthesis process the aluminium diacetate chloride is added to the process of this invention as the liquid comprising the aluminium diacetate chloride obtained in step (b). Preferably the liquid comprising the aluminium diacetate chloride is gradually added to a mixture of the diamine compound, the optionally substituted salicylaldehyde, the base compound and the alcohol.

[0037] The reaction may be as below:

[0038] The solid aluminium diacetate chloride may be used as such in the process to prepare an aluminium salphen complex. It is found that the aluminium diacetate chloride as present in the solvent mixture, optionally diluted with washing fluid of the preferred filtration, can be directly used in a step (c).

[0039] The invention is also directed to a process to prepare a halogen aluminium salphen complex salt by performing the following steps: (aa) preparing an aluminium salphen complex in a process according to this invention wherein the diamine compound is 3,4-diaminopyridine to obtain an aluminium salphen complex having a 3,4-pyridyl group bridging the two nitrogen atoms of the aluminium salphen complex, and

[0040] (bb) alkylating the pyridine nitrogen of the aluminium salphen complex by contacting the aluminium salphen complex with an organic halogen compound in a solvent.

[0041] The organic halide compound in step (bb) may be an organic iodide or chloride compound. Preferably the organic halogen compound is an organic bromide compound to prepare a bromide aluminium salphen complex salt. More preferably the organic bromide compound is presented as Br-R and wherein R is an alkyltrichlorosilane, propyl(alkyl)dichlorosilane, propyl(trialkoxysilane), or a propyl(dialkyl)chlorosilane group wherein the alkyl group has between 1 and 6 carbon atoms. These silane groups are advantageous because they enable to immobilise the bromide aluminium salphen complex by covalent bonding with the silanol groups as present on the surface of metal oxides, such as for example a silica or silica-alumina particle and / or the aluminol groups as present on the surface of an alumina or silica-alumina particle or the titanol groups as present on the surface of a titanium dioxide particle.

[0042] Step (bb) is performed in a solvent, preferably a polar solvent. A suitable solvent is 3-methyl-2-oxazolidione (MEOX), tetrahydrofuran (THF), dimethylformamide (DMF), 3-dimenthl-2-imidazolidinone (DMI), N-methyl-2- pyrrolidone (NMP), N-butyl-2-pyrrolidone (NBP), N,N-dimethylacetamide (DMA), / V, / V-Dimethyl- / \ / , / ' -trimethylene urea (DMPLI), sulfolane, dimethyl sulfoxide (DMSO) or mixtures of dimethyl sulfoxide (DMSO) and sulfolane or mixtures of dimethyl sulfoxide (DMSO) and n-butyl pyrrolidone (NBP). Mixtures of dimethyl sulfoxide (DMSO) and acetonitrile are preferred. Preferred polar solvents are chosen from the group of DMSO, DMF, NMP, DMA, DMI and DMPLI. Most preferred polar solvents are DMF or DMSO or their mixture.

[0043] The reaction may be as below:

[0044] As describe above it is possible to prepare a halogen aluminium salphen complex salt which can be immobilised on a surface of a silica or silica-alumina particle, of an alumina or silica-alumina particle or of a titanium dioxide particle. More in particular the invention is also directed to the following process.

[0045] Process to prepare a supported halogen aluminium salphen complex salt by performing the following steps:

[0046] (aaa) preparing a halogen aluminium salphen complex salt according to a process according to this invention wherein the diamine compound is 3,4- diaminopyridine, and

[0047] (bbb) immobilising the halogen aluminium salphen complex salt obtained in step (aaa) on titanium dioxide, silica, alumina and / or silica-alumina carrier particles, wherein the silanol groups as present on the surface of the silica or silica-alumina particle and / or the aluminol groups as present on the surface of the alumina or silica-alumina particle or the titanol as present on the surface of the titanium dioxide particle covalently bond with the silane group of the halogen aluminium salphen complex salt.

[0048] Preferably a halogen salt different from the halogen aluminium salphen complex salt is immobilised on the carrier particles. To the carrier surface the halogen aluminium salphen complex salt and a halogen salt will then be immobilized. The halogen aluminium salphen complex salt and the halogen salt are each individually immobilized to the carrier surface. Applicants have found that the supported catalyst or also referred to as heterogeneous catalyst according to this invention can be advantageously used as a catalyst or as part of a catalyst in a chemical process in the presence of an organic halogen compound and in the absence of a non-immobilised halogen ammonium salt, such as tetrabutylammonium bromide TBAB. The presence of this halogen compound enhances the activity of the catalyst and enhances the activity when the catalyst is used in a continuous process or reused in for example subsequent batch or semi-batch operations to prepare the cyclic carbonate. This allows one to use this catalyst in chemical processes which are up to now catalysed by an aluminium salphen complex and in the presence of a non-immobilised halogen ammonium salt, i.e. TBAB. By using this catalyst in the presence of an organic halogen compound one does not require the presence of the unwanted non-immobilised halogen ammonium salt. It is especially found that the heterogeneous catalyst of this invention can be used in a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide without leaching of a halogen ammonium salt, i.e. TBAB.

[0049] Furthermore the fact that the metal-complex and the halogen salt are each individually immobilized enables one to influence the relative presence of the halogen salt with respect to the metal complex of the catalyst.

[0050] Preferably an amine is also individually co-immobilized to the carrier surface next to the halogen aluminium salphen salt and the different halogen salt. It is found that the heterogeneous catalyst more effectively binds carbon dioxide when an amine is also immobilised. This allows one to directly contact carbon dioxide containing gasses, such as flue gasses or cement kiln flue gasses, with the catalyst. The amine is preferably a tertiary amine and may be presented by the general formula F R2R3N wherein R^ is an anchoring group for covalently binding the tertiary amine to the carrier surface. R2 and R3 may be the same or different organic group and preferably the same or different alkyl group having from 1 to 20 carbon atoms, preferably 1-6 carbon atoms. R2 and R3 can also be part of a ring structure forming a 5- or 6 membered ring. R2 or R3 may also be an aminoalkyl group. Examples of compounds where R^ and R3 are part of a ring structure are morpholine, piperidine and pyrrolidine structured compounds. More preferably, R2 and R3 are preferably the same alkyl group for example the same methyl or ethyl group. R^ may be an alkyl(trialkoxy)silane anchoring group, wherein the alkyl group preferably has 2 to 6 carbon atoms and the alkoxy group has preferably 1 to 3 carbon atoms. R^ may be an alkyltrichlorosilane, propyl(alkyl)dichlorosilane, propyl(trialkoxysilane), and a propyl(dialkyl)chlorosilane anchoring group wherein the alkyl group may have between 1 and 6 carbon atoms. Examples of these groups are propyl(trimethoxy)silane, propyl(triethoxy)silane, propyl(methyl)dichlorosilane and a propyl(dimethyl)chlorosilane and propyltrichlorosilane. R1 may also be a styryl(trialkyl)silane, propylbis(methylallyl)silanepropyl, tris(methy lally l)silane, propylphosphoric acid, propyl(dialkyl)phosphonate, and alkyl-1 , 1 bisphosphonic acid wherein the alkyl group may have between 1 and 6 carbon atoms.

[0051] The halogen salt is preferably an ammonium or phosphonium halogen salt. The choice of the halogen will also decide the choice of any other halogen compound used as part of the catalyst system as they are preferably the same. This halogen is also referred to as the catalyst system halogen. Preferred halogen salts are iodide salts and bromide salts. The iodide salt which is immobilised is preferably a phosphonium iodide salt and more preferably a quaternary ammonium iodide salt. The bromide salt which is immobilised is preferably a phosphonium bromide salt and more preferably a quaternary ammonium bromide salt. The quaternary ammonium iodide salt and the quaternary ammonium bromide salt may have the general formula R4R5R6 R |\IX, wherein X is a bromide or an iodide anion, R^ is an anchoring group and R5, R6 and R^may be the same or different alkyl or aryl groups preferably having between 1 and 20 carbon atoms. R and R® can also be part of a ring structure forming a 5- or 6 membered ring. Examples of compounds where R and R6 are part of a ring structure are morpholine, piperidine and pyrrolidine structured compounds. Preferred groups R5, R® and R7are alkyl groups having between 1 and 20 carbon atoms, more preferably between 3 and 12 carbon atoms, such as for example propyl, n-butyl, iso-butyl, tert.-butyl, n-pentyl, neopentyl and iso-pentyl.

[0052] Anchoring group R4may be as described for anchoring group R1 .

[0053] The halogen aluminium salphen complex salt (halogen Al salt), tertiary amine and halogen salt are suitably individually immobilized on the carrier particles as presented below:

[0054] S-(R1-(R2R3N))k

[0055] S- (R4-(R5R6R7NX))m

[0056] S-(R3-Halogen Al salt)nwherein S is the carrier surface, wherein the tertiary amine is R^ R2R3N and wherein R^ is an anchoring group which covalently binds the tertiary amine to the carrier surface S and R2and R3are the same or different alkyl group having from 1 to 20 carbon atoms or wherein R2and R3are part of a ring structure forming a 5- or 6 membered ring or R2or R3are amino alkyl groups, wherein the quaternary ammonium halogen salt is R4R3R6R7NX, wherein X is a bromide or an iodide anion, R4is an anchoring group which covalently binds the quaternary ammonium halogen salt to the carrier surface S and R3, R3and R^ are the same or different alkyl groups having between 1 and 20 carbon atoms, wherein R3is an anchoring group which covalently binds the metal complex to the carrier surface S and wherein k:m:n is the molar ratio of the amine, the halogen salt and the metal-complex as individually immobilized to the carrier surface S.

[0057] The molar ratio of halogen salt and metal-complex is suitably 1 :1 and higher. Expressed for the above formula this would be that m is equal or greater than n. When no amine is immobilized k will be equal to zero. More preferably the molar ratio of k:m is between 3:1 and 8:1. The molar ratio of n:k is preferably between 1 :3 and 1 :10 and more preferably between 1 :3 and 1 :5.

[0058] When the carrier surface has silanol groups as present on the surface S of the silica or silica-alumina particle and / or aluminol groups as present on the surface S of the alumina or silica-alumina particle it is preferred that F , R^ and R8 are the same or different alkyl(trialkoxy)silane anchoring group and / or an alkyltrichlorosilane anchoring group.

[0059] The heterogeneous catalyst as obtained by this process may be used as a catalyst or as part of a catalyst in a copolymerisation process to prepare aliphatic polycarbonates starting from an epoxide compound and carbon dioxide. Another reaction where the heterogeneous catalyst may be used is in a process to prepare a polyester by ring-opening polymerisation of a lactone compound as for example described in WO2012 / 065711.

[0060] Preferably the heterogeneous catalyst is used as a catalyst or as part of a catalyst in a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide.

[0061] The invention is therefore also directed to a process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide in the presence of the heterogeneous catalyst.

[0062] Preferably the process is performed in the presence of a corresponding halogen compound. The halogen compound may be an aryl halogen compound and preferably an alkyl halogen compound. The halogen of the halogen compound is the catalyst system halogen. The presence of the corresponding halogen compound is beneficial for the activity and stability of the catalyst. It has been found that by adapting the content of corresponding halogen compound when performing the process the reaction rate can be influenced. The halogen compound is not a halogen salt. The amount of corresponding halogen compound does not necessarily be high. Good results have been obtained when the corresponding halogen compound is present in between 0.3 and 10 mol% with respect to the epoxide compound, preferably between 0.5 and 3 mol% with respect to the epoxide compound.

[0063] When a bromide salt is immobilised preferably a bromide compound is present as the corresponding halogen compound. This bromide compound can in situ react with the immobilized tertiary amines to form the required quaternary ammonium salt. In this manner any immobilised halogen salt which is somehow removed from the carrier surface and which does not act as a co-catalyst can be replaced by in-situ formed immobilised quaternary ammonium salt. In this way the level of the co-catalyst can be kept at a desired level at the carrier surface. When the desired bromide salt is used the process is preferably performed in the presence of an aryl bromide and / or an alkyl bromide. Thus reactivation with a tetra-n-butylammonium bromide (TBAB) as in the process of W02009 / 109765 can be omitted. A suitable aryl bromide is benzyl bromide. Because this compound is corrosive for some metals it may be preferred to perform the process in glass or glass lined process apparatuses. Preferably less corrosive bromide compounds are used such as alkyl bromide, such as C3- C10 alkyl bromide compounds, for example propyl bromide, butyl bromide, pentyl bromide, hexyl bromide, heptyl bromide and octyl bromide. Another suited group of alkyl bromides are alkyl dibromides, such as 1 ,2-dibromoethane, 1 ,3-dibromopropane, 1 ,4-dibromobutane, 1 ,5 dibromopentane and 1 ,6- dibromohexane.

[0064] The starting epoxide compound suitably has 2 to 8 carbon atoms. Suitable epoxide compounds are ethylene oxide, propylene oxide, butylene oxide, pentene oxide, glycidol, styrene oxide, epichlorohydrin or fluoroethylene oxide.

[0065] The process may be performed as a continuous process wherein the heterogeneous catalyst is for example present as part of a fixed bed in a fixed bed reactor or as a slurry in a continuously stirred reactor. The halogen compound may then be co-fed to the fixed bed reactor together with the epoxide and carbon dioxide. Depending on the epoxide and further process conditions the reaction in the fixed bed may be performed in the gas or liquid phase or combinations of gas and liquid phases. The temperature may be between 20 and 150 °C, more preferably between 40 and 120 °C, and the absolute pressure is suitably between 0.1 and 1.5 MPa, more preferably between 0.1 and 0.3 MPa.

[0066] The carbon dioxide is suitably contacted with the epoxide compound in a suspension of liquid cyclic carbonate and the heterogeneous catalyst. The temperature and pressure conditions are chosen such that the cyclic carbonate is in its liquid state. The temperature and pressure conditions are further chosen such that carbon dioxide and epoxide easily dissolve in the liquid cyclic carbonate reaction medium. The temperature may be between 0 and 200 °C and the pressure between 0 and 5.0 MPa (absolute) and wherein temperature is below the boiling temperature of the cyclic carbonate product at the chosen pressure. At the high end of these temperature and pressure ranges complex reactor vessels will be required. Because favourable results with respect to selectivity and yield to the desired carbonate product are achievable at lower temperatures and pressures it is preferred that the temperature is between 20 and 150 °C, more preferably between 40 and 120 °C, and the absolute pressure is between 0.1 and 0.5 MPa, more preferably between 0.1 and 0.4 MPa. The process may be performed as for example described in WO202 1 / 094447.

[0067] Example 1

[0068] 232.78 g of AICI3 is added portion wise to a thermostated 5L reactor containing 0.67 L of Ethyl acetate. The reactor temperature is kept below 30°C during the addition. The AICI3 is then transferred to another thermostated reactor containing a slurry of 376.78 g of KOAc in 1.5 L of EtOH. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.2. The reaction mixture is kept below 30°C during the addition and stirred for an extra 12 hours after the end of the addition. The reactor is drained and filter over paper filter to separate the solid potassium chloride salt, washed with 2 x 500 mL EtOH. The filtrate is then slowly transferred to another reactor loaded with 171.6 g of 3,4-diaminopyridine, 500 mL EtOH, 800 mL of Et3N and 571 mL of 3- tertbutylsalicylaldehyde. At the end of the addition the reactor is heated to 75 °C overnight. The resulting orange clay is drained out of the reactor and filtered over Buchner filter. The resulting solid is washed three times with 500 mL Ethanol and dried in vacuum oven (8 mbar, 40°C) to give 721 .5 g of orange solid (93% yield). Analysis confirmed that the desired aluminium salphen complex was prepared in the illustrated telescoping synthesis:

[0069] 1 H NMR (300 MHz, DMSO-d6) 6 9.34 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.56 (d, J = 5.6 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.44 (m, 4H), 6.68 (m, 2H), 1.52 (s, 18H).

[0070] Example 2

[0071] 20 g of AICI3 is added portion wise to a round bottom flask containing 115 mL of ethyl acetate. The reaction temperature is kept below 30°C during the addition. The AICI3 is then transferred to a round bottom flask containing a slurry of 29.3 g of KOAc in 230 mL of EtOH (ethanol). The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.0. The reaction mixture is kept below 30°C during the addition and stirred for an extra 12 hours after the end of the addition. The reactor is drained and filter over paper filter to separate the solid potassium chloride salt, washed with 2 x 20 mL EtOH. The filtrate is concentrated under vacuum using a rotavapor apparatus. The obtained residue is stripped 3 times with toluene (30 mL) to obtain a free flowing white powder. 24.76 g, 63% yield.

[0072] Example 3

[0073] A round bottom flask was loaded with 1 .31 g of 3,4-diaminopyridine, 3.46 g of the white powder (AI(0Ac)2CI) as obtained in Example 2, 4.32 mL 3- tertbutylsalicylaldehyde, 8.37 mL N,N’-diisopropyl ethylamine and 16 mL MeOH. The reaction mixture was refluxed for 18h before being cooled down to room temperature. The slurry was then filtered over glass frit and washed 3 times with 20 mL MeOH. The resulting orange solid was dried under vacuum (40 °C, 8 mbar) for 4 hours to yield 4.09 g of an orange powder (69% yield). Analysis confirmed that the desired aluminium salphen complex was prepared:

[0074] 1 H NMR (300 MHz, DMSO-de) 6 9.34 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.56 (d, J = 5.6 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.44 (m, 4H), 6.68 (m, 2H), 1 .52 (s, 18H).

[0075] Example 4

[0076] A round bottom flask was loaded with 1 .31 g of 3,4-diaminopyridine, 3.46 g of AI(OAC)2CI as obtained in Example 2, 4.32 mL 3-tertbutylsalicylaldehyde, 3.46 g KOAc (potassium acetate) and 24 mL MeOH (methanol). The reaction mixture was refluxed for 18h before being cooled down to room temperature. The slurry was then filtered over glass frit and washed 3 times with 20 mL MeOH. The resulting orange solid was dried under vacuum (40 °C, 8 mbar) for 4 hours to yield 3.54 g of an orange powder (60% yield). Analysis confirmed that the desired aluminium salphen complex was prepared:

[0077] 1 H NMR (300 MHz, DMSO-d6) 6 9.34 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.56 (d, J = 5.6 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.44 (m, 4H), 6.68 (m, 2H), 1 .52 (s, 18H).

[0078] Example 5

[0079] An aluminium complex having the same structure as the complex obtained in example 1 (3.68 g, 7.5 mmol) was loaded into a flame dried Schlenk flask under nitrogen atmosphere. To the Schlenk flask was added dry dimethylformamide (8.4 mL) and 3-bromopropyltrimethoxysilane (5.64 mL, 30 mmol). The reaction mixture was heated to 80°C for 48 hours and yielded an orange precipitate. The reaction was then cooled down to room temperature and centrifuge to isolate the solid which was subsequently washed with 3x10 mL petroleum ether and 3x10 mL diethyl ether to remove the excess 3- bromopropyltrimethoxysilane. The orange powder obtained was dried under vacuum to yield 5 g of the silylated compound with 6 molecules of DMF per mol silyated compound. 1 H NMR: (DMSO-c / 6) 9.88 (br s, 1 H), 9.63 (br s, 1 H), 9.53 (br s, 1 H), 9.07 (d, 7.00 Hz, 1 H), 8.69 (d, 7.00 Hz, 1 H), 7.65 (m, 4H), 7.56 (d, 7.6 Hz, 1 h), 6.89 (t, 7.59 Hz, 2H), 4.55 (t, 7.20 Hz, 2H), 3.51 (s, 9H, Si-OMe), 2.11 (m, 2H), 1.56 (s, 9H), 1.55 (s, 9H), 0.70 (m, 2 H)

[0080] Example 6

[0081] A heterogeneous catalyst was made by immobilising the siliyated aluminium salphen complex as obtained in Example 5. 4 g of Grace Silica (40- 63 pm particle size, 35 A pores) was dried in a baffled flask using a Kugelrohr apparatus at 200 °C and 50 rpm for 15 hours. The silica was cooled down to room temperature and the flask was refilled with nitrogen. 30 mL of propylene carbonate was then added to the silica and the resulting slurry was heated up to 130 °C. The complex, ammonium bromide salt and amine were individually immobilized to the silica surface by adding a solution of silylated (1 .13 mL of a 0.44 M dimethyl formamide solution), a solution of 3- (tributyl)ammoniumpropyltrimethoxysilane bromide (1 .2 mL of a 0.5 M acetonitrile solution) and / V, / V-dimethylaminopropyltrimethoxysilane (540 pL) in 6 mL of propylene carbonate to the silica over 3 hours. At the end of the addition, the addition vessel was washed with 2x5 mL propylene carbonate and the reaction was continued for 18 hours. The reaction mixture was cooled down to room temperature before filtration over glass fibre filter. The solid was washed with 2x30 mL propylene carbonate and 2x30 mL ethyl acetate and dried under vacuum (10 mbar) at 70°C for 2 hours to yield 4.67 g of the catalyst as a yellow powder.

[0082] The molar ratio of the individually immobilized salen aluminium complex as expressed in mol aluminium, individually immobilized tertiary amine and total individually immobilized ammonium of the heterogeneous catalyst and determined by ICP-MS was about the ratio of the above referred to starting compounds: 1 mol aluminium, 4 mol amine and 1 mol ammonium also referred to as Ratio of AI / N / N+ (mol) or the ratio of n / k / m (mol). The ammonium in this ratio relates to the ammonium of the 3-(tributyl)ammoniumpropyltrimethoxysilane bromide only.

[0083] The molar ratio of AI / N / N+ as determined by ICP-MS analysis of the immobilized salen aluminium complex as prepared in this example is provided in the below table 1.

[0084] Table 1

[0085] Example 7

[0086] Example 6 was repeated wherein more ammonium salt was individually co-immobilized such that the ratio of the starting compounds as expressed as a molar ratio of the salen aluminium complex as expressed in mol aluminium, mol tertiary amine and mol ammonium was 1 mol aluminium, 4 mol amine and 2 mol ammonium. The ammonium in this ratio relates to the ammonium of the 3- (tributyl)ammoniumpropyltrimethoxysilane bromide only.

[0087] Example 8

[0088] Example 6 was repeated wherein more ammonium salt was individually co-immobilized such that the ratio of the starting compounds as expressed as a molar ratio of salen aluminium complex as expressed in mol aluminium, mol tertiary amine and mol ammonium was 1 mol aluminium, 4 mol amine and 1.5 mol ammonium. The ammonium in this ratio relates to the ammonium of the 3- (tributyl)ammoniumpropyltrimethoxysilane bromide only.

[0089] Example 9

[0090] In this example the catalytic activity of the heterogeneous catalyst of Examples 6, 7 and 8 were tested in the presence of added octyl bromide in the below reaction of styrene oxide (StO) and carbon dioxide to prepare 4-phenyl- 1 ,3-dioxolan-2-one. In a Schlenk reaction flask, 98.06 mg of the heterogeneous catalyst, was heated to 100 °C and put on vacuum. The flask was refilled with CO2 gas after which the propylene carbonate (3.33 mL), styrene oxide (1 mL) and octyl bromide (30.26 pL) were added. The flask was purged with CO2 and the stirring was started. After 24 hours the conversion was measured and listed for the different catalysts in Table 2. The main product was 4-phenyl-1 ,3-dioxolan-2- one.

[0091] Table 2

[0092] Example 10

[0093] Example 9 was repeated with the catalyst of Example 6 except that the halogen compound was 1 ,4-dibromobutane (DBB) instead of octyl bromide. The experiment was performed with varying amounts of DBB as listed in Table 3 as Examples 10a-10d. After a first run (Run 1 ), the stirring was stopped, and the solid catalyst was allowed to settle to the bottom of the Schlenk reaction flask. Thereafter, the solvent phase of the reaction mixture was removed. Then, ethyl acetate (4 mL) was added, the reaction mixture was stirred for 15 minutes before letting the solid catalyst to settle to the bottom of the Schlenk reaction flask. The solvent phase of the reaction mixture was removed. This washing procedure using ethyl acetate was performed twice in total. Then, the Schlenk reaction flask was heated to 100 °C and put on vacuum. The flask was refilled with CO2 gas after which the propylene carbonate, styrene oxide and the 1 ,4- dibromobutane (if present) were added. The flask was purged with CO2 and the stirring was started to repeat the example 9 experiment. After 20 hours the conversion was measured and listed for the different catalysts in Table 3 as Run

[0094] 2. This was repeated for a Run 3 and Run 4. The results are presented in Table

[0095] 3. The results indicate an optimal DBB content of around 2 mol% to styrene oxide for the catalyst of Example 6. The presence of DBB enhances the activity of the catalyst and enhances the activity when the catalyst is reused or recycled in subsequent runs when preparing the cyclic carbonate.

[0096] Table 3

[0097] Example 11

[0098] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 1 mL of a 0.75 M stock solution of 3,4-diaminopyridine in ethanol, 1 mL of a 1 .59 M stock solution of 3-tert-Butyl-2- hydroxybenzaldehyde in ethanol, 1 mL of a 0.83 M stock solution of AI(0Ac)2CI as obtained in Example 2 in ethanol, and 1 mL ethanol. The reaction mixture was refluxed for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge tube and centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of H2O and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of acetonitrile and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 4 hours to yield 0.35 g of an orange powder (95% yield). Analysis confirmed that the desired aluminium salphen complex was prepared: 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.55 (d, J = 5.6 Hz, 1 H), 8.02 (d, J = 5.8 Hz, 1 H), 7.52 - 7.37 (m, 4H), 6.68 (td, J = 7.6, 2.1 Hz, 2H), 1.52 (s, 18H).

[0099] Comparative experiment C

[0100] Example 11 was repeated except that instead of 3,4-diaminopyridine, ethylene diamine is used as the diamine compound. The experiment failed in that the free ligand was prepared and that not the desired aluminium salphen complex was prepared.

[0101] Comparative experiment D

[0102] Example 11 was repeated except that instead of 3,4-diaminopyridine (1 S,2S)-cyclohexane-1 ,2-diamine was used as the diamine compound. The experiment failed in that the free ligand was prepared and that not the desired aluminium salphen complex was prepared.

[0103] Example 12

[0104] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 1 mL of a 0.75 M stock solution of o-Phenylenediamine in ethanol, 1 mL of a 1.59 M stock solution of salicylaldehyde in ethanol, 1 mL of a 0.83 M stock solution of AI(OAC)2CI as obtained in Example 2 in ethanol, and 1 mL ethanol. The reaction mixture was refluxed for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge tube and centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of H2O and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of acetonitrile and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 4 hours to yield 0.28 g of a yellow powder (quantitative yield). Analysis confirmed that the desired aluminium salphen complex was prepared:

[0105] 1 H NMR (300 MHz, DMSO-d6) 6 9.12 (s, 2H), 8.06 (dd, J = 6.3, 3.5 Hz, 2H), 7.73 - 7.55 (m, 2H),7.54 - 7.34 (m, 4H), 6.84 (d, J = 8.4 Hz, 2H), 6.74 (t, J = 7.4 Hz, 2H).

[0106] Example 13

[0107] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 81.08 mg benzene-1 ,2-diamine, 445.06 mg 3,5-dibromosalicylaldehyde ,148.93 mg AI(OAc)2CI as obtained in Example 2 and 4 mL methanol.

[0108] The reaction mixture was allowed to proceed at room temperature for 16 hours. The reaction mixture was transferred into a centrifuge tube and centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of acetonitrile and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 16 hours to yield 0.53 g of an orange powder (98% yield). Analysis confirmed that the desired aluminium salphen complex was prepared: 1 H NMR (300 MHz, DMSO-d6) 5 9.00 (s, 2H), 7.89 (d, J = 2.5 Hz, 2H), 7.65 - 7.62 (m, 2H), 7.50 - 7.44 (m, 2H), 7.38 - 7.32 (m, 2H).

[0109] Comparative experiment A

[0110] Example 13 was repeated except that no KOAc and no AI(OAc)2CI was added. No aluminium complex was obtained. Instead the non-complexated ligand was obtained. After drying 0.41 g of a dark orange powder (87% yield) was obtained. Analysis confirmed that the free salphen ligand was prepared:

[0111] 1 H NMR (300 MHz, DMSO-d6) 5 14.02 (s, 2H), 8.99 (s, 2H), 7.99 - 7.93 (m, 4H), 7.60 - 7.45 (m, 4H). Comparative experiment B

[0112] Example 13 was repeated except that no KOAc was added. No aluminium complex was obtained. Instead the non-complexed ligand was obtained as in Experiment A. After drying 0.42 g of a dark orange powder (90% yield). Analysis confirmed that the free salphen ligand was prepared as in Experiment A:

[0113] 1 H NMR (300 MHz, DMSO-d6) 5 14.02 (s, 2H), 8.99 (s, 2H), 7.97 - 7.94 (m, 4H), 7.58 - 7.47 (m, 4H).

[0114] Example 14

[0115] Example 12 was repeated except that instead of a the unsubstituted salicylaldehyde a substituted salicylaldehyde was used with a tert, butyl group on the 3 position. After drying under vacuum 0.33 g of a yellow powder (90% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex was prepared:

[0116] 1 H NMR (300 MHz, DMSO-d6) 69.10 (s, 2H), 8.08 (dd, J = 6.3, 3.5 Hz, 2H), 7.50 - 7.39 (m, 4H), 7.39 (s, 2H), 6.65 (t, J = 7.6 Hz, 2H), 1 .52 (s, 18H). Example 15

[0117] Example 12 was repeated except that instead of the o-

[0118] Phenylenediamine, 2,3-diaminopyridine was used as the diamide compound:

[0119] After drying under vacuum 0.27 g of a brown powder (95% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex was prepared:

[0120] 1 H NMR (300 MHz, DMSO-d6) 6 9.43 (h, J = 1.4 Hz, 1 H), 9.20 (q, J = 1.1 Hz, 1 H), 8.63 - 8.34 (m, 2H), 7.81 - 7.64 (m, 1 H), 7.64 - 7.52 (m, 2H), 7.52 - 7.37 (m, 2H), 6.95 - 6.81 (m, 2H), 6.83 - 6.57 (m, 2H).

[0121] Example 16

[0122] Example 12 was repeated except that instead of the o-

[0123] Phenylenediamine, 3,4-diaminopyridine was used as the diamide compound:

[0124] After drying under vacuum yield 0.28 g of a yellow powder (quantitative yield). Analysis confirmed that the desired aluminium salphen complex was prepared:

[0125] 1 H NMR (300 MHz, DMSO-d6) 6 9.30 (s, 2H), 9.27 (s, 1 H), 8.59 (d, J = 5.5 Hz, 1 H), 8.01 (d, J =5.6 Hz, 1 H), 7.59 (td, J = 8.0, 1 .9 Hz, 2H), 7.54 - 7.37 (m, 2H), 6.96 - 6.82 (m, 2H), 6.82 - 6.70 (m, 2H).

[0126] Example 17

[0127] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 81.85 mg 3,4- diaminopyridine, 272.18 mg 2-Hydroxy-1 -naphthaldehyde, 148.93 mg AI(OAc)2CI as obtained in Example 2, and 4 mL ethanol. The reaction mixture was refluxed for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge tube and centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of H2O and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of acetonitrile and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 4 hours to yield

[0128] 0.36 g of a dark orange powder (quantitative yield). Analysis confirmed that the desired aluminium salphen complex was prepared:

[0129] 1 H NMR (300 MHz, DMSO-d6) 6 9.84 (s, 1 H), 9.77 (s, 1 H), 9.49 (s, 1 H), 8.59 (t, J = 7.3 Hz, 2H), 8.53 (d, J = 5.6 Hz, 1 H), 8.26 (d, J = 5.6 Hz, 1 H), 7.95 (t, J = 9.7 Hz, 2H), 7.78 (d, J = 8.0 Hz, 2H), 7.54 (q, J = 6.9 Hz, 2H), 7.32 (q, J = 6.9 Hz, 2H), 7.04 (d, J = 9.0 Hz, 2H).

[0130] Example 18

[0131] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 81.85 mg 3,4- diaminopyridine, 283.39 mg 3-tert-Butyl-2- hydroxybenzaldehyde, 148.93 mg AI(OAc)2CI as obtained in Example 2, and 4 mL methanol. The reaction mixture was refluxed for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge tube and centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of H2O and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, replaced by 4 mL of acetonitrile and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 4 hours to yield 0.20 g of an orange powder (54% yield). Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0132] 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.29 (s, 1 H), 9.23 (s, 1 H), 8.55 (d, J = 5.5 Hz, 1 H), 8.02 (d, J = 5.8 Hz, 1 H), 7.51 - 7.35 (m, 4H), 6.67 (t, J = 7.2 Hz, 2H), 1.52 (s, 18H). Example 19

[0133] Example 18 was repeated except that instead of 4 ml methanol 4 ml 2- propanol is used as the solvent. After the vacuum drying 0.26 g of an orange powder (71 % yield) was obtained. Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0134] 1 H NMR (300 MHz, DMSO-d6) 6 9.31 (s, 1 H), 9.27 (s, 1 H), 9.21 (s, 1 H), 8.54 (d, J = 5.6 Hz, 1 H), 8.00 (d, J = 5.6 Hz, 1 H), 7.51 - 7.32 (m, 4H), 6.65 (t, J = 7.1 Hz, 2H), 1.51 (s, 18H).

[0135] Example 20

[0136] Example 18 was repeated except that instead of 4 ml methanol 4 ml 1 - pentanol was used as the solvent. After the vacuum drying 0.23 g of an orange powder (63% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0137] 1 H NMR (300 MHz, DMSO-d6) 6 9.31 (s, 1 H), 9.24 (s, 1 H), 9.20 (s, 1 H), 8.53 (d, J = 5.7 Hz, 1 H), 8.00 (d, J = 5.7 Hz, 1 H), 7.49 - 7.33 (m, 4H), 6.71 - 6.59 (m, 2H), 1.51 (s, 18H).

[0138] Example 21

[0139] A 4 mL vial was loaded with 228.18 mg of KOAc (potassium acetate), 81.85 mg 3,4-diaminopyridine, 283.39 mg 3-tert-Butyl-2-hydroxybenzaldehyde, 148.93 mg AI(OAc)2CI as obtained in Example 2, and 4 mL 1 ,4-butanediol. The reaction mixture was allowed to proceed at 80 °C for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge tube containing 20 mL methanol causing immediate precipitation after which the tube was centrifuged for 5 minutes at 4000 rpm. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 16 hours to yield 0.10 g of a dark yellow powder (27% yield). Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared: 1 H NMR (300 MHz, DMSO-d6) 5 9.35 - 9.12 (m, 3H), 8.53 (d, J = 5.6 Hz, 1 H), 7.99 (d, J = 6.4 Hz, 1 H), 7.52 - 7.32 (m, 4H), 6.64 (t, J = 9.6 Hz, 2H), 1 .51 (s, 18H).

[0140] Example 22

[0141] Example 21 was repeated except that instead of 4 ml 1 ,4-butanol, 4 ml of 1 ,5-pentadiol was used. After drying 0.20 g of an orange powder (53% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0142] 1 H NMR (300 MHz, DMSO-d6) 5 9.34 (s, 1 H), 9.29 (s, 1 H), 9.22 (s, 1 H), 8.55 (d, J = 5.6 Hz, 1 H), 8.01 (d, J = 5.6 Hz, 1 H), 7.52 - 7.35 (m, 4H), 6.67 (t, J = 6.9 Hz, 2H), 1.52 (s, 18H).

[0143] Comparative experiment E

[0144] Example 18 was repeated except that instead of methanol a number of alternative alcohols were used as the solvent, which are either cyclic alkanols or di or tri-alcohols where the alcohol groups are positioned relatively close along the carbon chain. The alcohols tested were glycerol, ethylene glycerol, 1 ,3- propanediol and cyclohexanol. The experiments failed in that no aluminium salphen complex was prepared.

[0145] Example 23

[0146] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate) and 2.1 mL of 1 -propanol. A 4 mL vial was loaded with 66.67 mg AlCh and 1.0 mL ethyl acetate and subsequently added to the centrifuge tube. The reaction mixture was shaken for 16 hours at room temperature. The molar ratio of aluminium trichloride and potassium acetate is 1.0:2.1.

[0147] A 20 mLvial was loaded with 138.29 mg of KOAc (potassium acetate), 49.60 mg of 3,4-diaminopyridine, 0.70 mL 1 -propanol and 0.165 mL 3- tertbutylsalicylaldehyde and stirred for 1 hour at room temperature. The centrifuge tube was centrifuged for 3 minutes at 4000 rpm. The supernatant was removed and added to the 20 mL vial. Then, 0.7 mL of 1 -propanol was added to the centrifuge tube and the reaction mixture was vigorously shaken to disperse the solid material. The centrifuge tube was centrifuged for 3 minutes at 4000 rpm. The supernatant was removed and added to the 20 mL vial. This washing procedure was repeated three times and all supernatants were added to the 20 mL vial.

[0148] The reaction mixture in the 20 mL vial was allowed to proceed at 80 °C for 16 hours before being cooled down to room temperature. The reaction mixture was transferred into a centrifuge and centrifuged for 3 minutes at 4000 rpm. The supernatant was removed, replaced by 1 mL ethanol and the reaction mixture was vigorously shaken to disperse the solid material. The reaction mixture was centrifuged for 3 minutes at 4000 rpm. This washing procedure was repeated three times. The supernatant was removed, and the resulting solid was dried under vacuum (70 °C, 8 mbar) for 2 hours to yield 0.12 g of an orange powder (54% yield). Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0149] 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.55 (d,

[0150] J = 5.5 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.51 - 7.36 (m, 4H), 6.68 (t, J = 7.3 Hz, 2H), 1.52 (s, 18H).

[0151] Example 24

[0152] Example 23 was repeated except with 2.1 mL of 1 -butanol instead of 2.1 ml of 1 -propanol. The 20 mL vial was loaded with 0.70 mL 1 -butanol instead of 1 - propanol. After the drying, 0.11 g of an orange powder (48% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex as in Example 11 was prepared:

[0153] 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.28 (s, 1 H), 9.24 (s, 1 H), 8.55 (d,

[0154] J = 5.5 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.53 - 7.34 (m, 4H), 6.66 (t, J = 7.2 Hz, 2H), 1.52 (s, 18H). Example 25

[0155] Example 23 was repeated except with 2.1 mL of ethanol instead of 2.1 ml of 1-propanol and 1.0 mL methyl acetate instead of 1.0 mL ethyl acetate. The 4 mL vial was loaded with 1.0 mL methyl acetate instead of 1.0 mL ethyl acetate. The 20 mL vial was loaded with 0.70 mL ethanol instead of 1 -propanol. After the drying, 0.03 g of an orange powder (12% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex of Example 11 was prepared:

[0156] 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.30 (s, 1 H), 9.23 (s, 1 H), 8.56 (d, J = 5.5 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.50 - 7.37 (m, 4H), 6.67 (t, J = 7.5 Hz, 2H), 1.52 (s, 18H).

[0157] Example 26

[0158] Example 25 was repeated except that 1.0 mL isobutyl acetate was used instead of 1 .0 mL methyl acetate. The 4 mL vial was loaded with 1 .0 mL isobutyl acetate instead of 1 .0 mL methyl acetate. After the drying, 0.02 g of an orange powder (10% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex of Example 11 was prepared:

[0159] 1 H NMR (300 MHz, DMSO-de) 6 9.33 (s, 1 H), 9.29 (s, 1 H), 9.23 (s, 1 H), 8.55 (d, J = 5.4 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.49 - 7.37 (m, 4H), 6.67 (t, J = 7.2 Hz, 2H), 1.51 (s, 18H).

[0160] Example 27

[0161] Example 25 was repeated except that 1.0 mL n-propyl acetate was used instead of 1 .0 mL methyl acetate. The 4 mL vial was loaded with 1 .0 mL n-propyl acetate instead of 1 .0 mL methyl acetate. After the drying, 0.01 g of an orange powder (7% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex of Example 11 was prepared and was isolated alongside 3- tertbutylsalicylaldehyde (free aldehyde) and (E)-2-(((3-aminopyridin-4- yl)imino)methyl)-6-(tert-butyl)phenol (half salphen) in a molar ratio of 1.0:0.2:0.4 as shown below:

[0162] Al-salphen Free aldehyde Half-salphen

[0163] Example 28

[0164] A 15 mL centrifuge tube was loaded with 122.68 mg of KOAc (potassium acetate) and 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AlCh and 1 .0 mL ethyl acetate and subsequently added to the centrifuge tube. The reaction mixture was shaken for 16 hours at room temperature. The molar ratio of aluminium trichloride and potassium acetate is 2.5. The remaining procedure is as in Example 22. After the drying 0.01 g of an orange powder (6% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex was prepared and was isolated alongside 3-tertbutylsalicylaldehyde and (E)-2-(((3- aminopyridin-4-yl)imino)methyl)-6-(tert-butyl)phenol in a molar ratio of 1.0:0.1 :0.2.

[0165] Example 29

[0166] A 15 mL centrifuge tube was loaded with 86.14 mg of NaOAc (sodium acetate) and 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AICI3 and 1 .0 mL ethyl acetate and subsequently added to the centrifuge tube. The reaction mixture was shaken for 16 hours at room temperature. The molar ratio of aluminium trichloride and potassium acetate is 2.1 The remaining procedure is as in Example 22. A solid sodium chloride salt was separated. After the drying 0.03 g of an orange powder (15% yield) was obtained. Analysis confirmed that the desired aluminium salphen complex of Example 11 was prepared: 1 H NMR (300 MHz, DMSO-d6) 6 9.33 (s, 1 H), 9.30 (s, 1 H), 9.24 (s, 1 H), 8.55 (d,

[0167] J = 5.6 Hz, 1 H), 8.02 (d, J = 5.7 Hz, 1 H), 7.50 - 7.37 (m, 4H), 6.67 (t, J = 7.1 Hz, 2H), 1.52 (s, 18H). Some of the above examples are summarized in the below table, wherein the alcohol (step (a), acetate and XOAc refers to the alcohol, organic acetate and potassium acetate or sodium acetate used to prepare the aluminium diacetate chloride, ie step (a) of the above telescoping synthesis process to prepare the same aluminium salphen complex. The alcohol in step (c) refers to the alcohol used in the final step (c) where the aluminium salphen complex is prepared.

[0168] Table 4

[0169] In admixture with the free aldehyde and the half salphen

Claims

Claims1. Process to prepare an aluminium salphen complex by reacting(i) a diamine compound selected from the group of an optionally substituted benzene-1 ,2-diamine, an optionally substituted 2,3-diaminopyridine and an optionally substituted 3,4-diaminopyridine,(ii) an optionally substituted salicylaldehyde or an optionally substituted 2- hydroxy-1 -naphthaldehyde and(iii) aluminium diacetate chloride in a liquid reaction mixture also comprising an alcohol and a base compound.

2. Process according to claim 1 , wherein the diamine compound is 3,4- diaminopyridine.

3. Process according to any one of claims 1-2, wherein the optionally substituted salicylaldehyde is substituted with an alkyl group on the 3 position.

4. Process according to claim 3, wherein the alkyl group is ter. butyl.

6. Process according to any one of claims 1-5, wherein the alcohol is a mono, di or tri aliphatic alcohol, wherein at least 4 carbon atoms are present between the hydroxy groups for the di or tri aliphatic alcohols.

7. Process according to any one of claims 1-6, wherein the alcohol is an aliphatic alcohol excluding ethylene glycol, glycerol and 1 ,3-propanol.

8. Process according to any one of claims 6-7, wherein the alcohol is methanol, ethanol, isopropanol or their mixtures.

9. Process according to any one of claims 1-8, wherein the base compound is or potassium acetate, N,N-diisopropyl ethylamine or triethylamine.

10. Process according to any one of claims 1-9, wherein the molar ratio between aluminium diacetate chloride and the diamine compound is between 1 :1 and 2:1.

11. Process according to any one of claims 1 -10, wherein the molar ratio between the base compound and the diamine compound is between 2.7: 1 and 6:1 .

12. Process according to any one of claims 1-11 , wherein the temperature is between 10 and 100 °C.

13. Process according to any one of claims 1 -12, wherein concentration of the diamine compound is between 0.5 and 0.9 mol / L.

14. Process according to any one of claims 1-13, wherein aluminium diacetate chloride is gradually added to a mixture of the diamine compound, the optionally substituted salicylaldehyde, the base compound and the alcohol.

15. Process to prepare an aluminium salphen complex by performing the following steps:(a) reacting aluminium trichloride with sodium acetate or potassium acetate in a liquid reaction mixture comprising an alcohol and an organic acetate to obtain aluminium diacetate chloride and solid sodium chloride salt or solid potassium chloride salt as a by-product and wherein the molar ratio of aluminium trichloride and sodium acetate or potassium acetate is between 1 :1.5 and 1 :3,(b) separating the solid sodium chloride salt or potassium chloride salt from the reaction mixture obtained in step (a)to obtaining a liquid comprising the aluminium diacetate chloride and poor in solid sodium chloride salt or potassium chloride salt, and(c) performing the process of any one of claims 1-14 using the aluminium diacetate chloride as present in the liquid obtained in step (b).

16. Process according to claim 15, wherein in step (c) the aluminium diacetate chloride is added to the process of claims 1 -14 as part of the liquid comprising the aluminium diacetate chloride obtained in step (b).

17. Process according to claim 16, wherein in step (c) the liquid comprising aluminium diacetate chloride is gradually added to a mixture of the diamine compound, the optionally substituted salicylaldehyde, the base compound and the alcohol.

18. Process according to claim 15, wherein in step (c) the aluminium diacetate chloride is added to the process of claims 1-14 as a solid obtained by evaporating the alcohol from the liquid comprising the aluminium diacetate chloride obtained in step (b).

19. Process according to any one of claims 15-18, wherein the alcohol in step (a) is ethanol.

20. Process according to any one of claims 15-19, wherein the organic acetate in step (a) is ethyl acetate.21 . Process according to any one of claims 15-20, wherein the alkali acetate in step (a) is potassium acetate.

22. Process according to any one of claims 15-21 , wherein the temperature at step (a) is performed is between 10 °C and the boiling point of the solvent mixture.

23. Process according to any one of claims 15-22, wherein the molar ratio of aluminium trichloride and the alkali acetate compound is between 1 :1.9 and 1 :2.5.

24. Process to prepare a halogen aluminium salphen complex salt by performing the following steps:(aa) preparing an aluminium salphen complex in a process according to any one of claims 1-23 wherein the diamine compound is 3,4-diaminopyridine to obtain an aluminium salphen complex having a 3,4-pyridyl group bridging the two nitrogen atoms of the aluminium salphen complex,(bb) alkylating the pyridine nitrogen of the aluminium salphen complex by contacting the aluminium salphen complex with an organic halogen compound in a solvent.

25. Process according to claim 24, wherein the organic halogen compound is an organic bromide compound to prepare a bromide aluminium salphen complex salt.

26. Process to prepare a supported halogen aluminium salphen complex salt by performing the following steps:(aaa) preparing a halogen aluminium salphen complex salt according to a process according to any one of claims 24-25, and(bbb) immobilising the halogen aluminium salphen complex salt obtained in step (aaa) on titanium dioxide, silica, alumina and / or silica alumina carrier particles, wherein the silanol groups as present on the surface of the silica or silica- alumina particle and / or the aluminol groups as present on the surface of the alumina or silica-alumina particle or the titanol as present on the surface of the titanium dioxide particle covalently bond with the silane group of the halogen aluminium salphen complex salt.

27. Process according to claim 26, wherein a halogen salt different from the halogen aluminium salphen complex salt is immobilised on the carrier particles.

28. Process according to claim 27, wherein the different halogen salt is a quaternary ammonium halogen salt and / or a phosphonium halogen salt.

29. Process according to any one of claims 26-28, wherein a tertiary amine is immobilised on the carrier particles.

30. Process according to claim 29, wherein the halogen aluminium salphen complex salt, tertiary amine and halogen salt are individually immobilized on the carrier particles as presented below:S-(R1-(R2R3N))kS- (R4-(R5R6R7NX))mS-(R3-MetalComplex)nwherein S is the carrier surface of the carrier particle, wherein the tertiary amine is R^ R2R3N and wherein R^ is an anchoring group which covalently binds the tertiary amine to the carrier surface S and R2and R3are the same or different alkyl group having from 1 to 20 carbon atoms or wherein R2and R3are part of a ring structure forming a 5- or 6 membered ring or R2or R3are amino alkyl groups, wherein the quaternary ammonium halogen salt is R4R5R3R7NX, wherein X is a bromide or an iodide anion, R4is an anchoring group which covalently binds the quaternary ammonium halogen salt to the carrier surface S and R3, R3and R are the same or different alkyl groups having between 1 and 20 carbon atoms, wherein R3is an anchoring group which covalently binds the metal complex to the silanol groups as present on the surface of the silica or silica-alumina particle and / or the aluminol groups as present on the surface of the alumina or silica-alumina particle or the titanol as present on the surface of the titanium dioxide particle carrier surface S and wherein the molar ratio k:m is between 3:1 and 8:1 and the molar ratio n:k is between 1 :3 and 1 :10.31 . A process to prepare a cyclic carbonate by reacting an epoxide compound and carbon dioxide in the presence of the heterogeneous catalyst obtainable with the process of any one of claims 29 or 30 and a halogen compound.

32. The process according to claim 31 , wherein the heterogeneous catalyst is present as a suspension in the cyclic carbonate.

33. The process according to claim 31 , wherein the heterogeneous catalyst is present as part of a fixed bed in a fixed bed reactor.

34. The process according to any one of claims 31-33, wherein the halogen compound is an aryl halogen compound or an alkyl halogen compound.

35. The process according to claim 34, wherein the halogen compound is a C3-C10 alkyl bromide.

36. The process according to claim 35, wherein the alkyl bromide is any one of propyl bromide, butyl bromide, pentyl bromide, hexyl bromide, heptyl bromide, octyl bromide, 1 ,2-dibromoethane, 1 ,3-dibromopropane, 1 ,4-dibromobutane, 1 ,5 dibromopentane and 1 ,6-dibromohexane.

37. The process according to any one of claims 31-36, wherein the epoxide compound has 2 to 8 carbon atoms.

38. The process according to claim 37, wherein the epoxide compound is ethylene oxide, propylene oxide, butylene oxide, pentene oxide, glycidol, styrene oxide or fluoroethylene oxide.

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