Crystalline aluminum diacetate compounds, method for producing crystalline aluminum diacetate compounds, and use

Abstract

The invention relates to crystalline aluminum diacetate compounds characterized in that the aluminum diacetate compounds correspond to the formula: cis-trans-Al(OH)(CH3COO)2. The invention also relates to a method for producing crystalline aluminum diacetate compounds, comprising the following steps: i. providing an aqueous solution of an aluminum salt; ii. adding acetic acid or salts thereof; iii. setting the pH of the mixture; iv. controlling the temperature of the mixture; v. separating the solid from the solution; vi. washing the obtained solid, and vii. drying the washed solid; wherein - step iii. and step iv. are coordinated with one another in such a way that - for the production of compound I. a pH between 0 and 4 and a temperature between 50°C and 140°C or a pH between 0 and 6 and a temperature between 80°C and 140°C are set, and - for the production of compound II. a pH between 4 and 6 and a temperature between 20°C and 80°C are set, and - after step iii. and step iv. have been carried out, the mixture has a reaction time between 15 minutes and 4 weeks at the set conditions before step v. is carried out. The invention also relates to the use of the crystalline aluminum diacetate compounds.

Description

[0001] CRYSTALLINE ALUMINUM DIACETATE COMPOUNDS, CRYSTALLINE

[0002] ALUMINUM DIACETATE COMPOUND - MANUFACTURE PROCESS AND USE

[0003] The invention relates to crystalline aluminum diacetate compounds.

[0004] Furthermore, the invention relates to a process for the preparation of crystalline aluminum diacetate compounds and their use.

[0005] Many methods have been described for the preparation of aluminum diacetate (AI(OH)(CHSCOO)2), also known as acetic alumina, aluminum acetate, basic aluminum acetate, basic aluminum acetate, aluminum monohydroxyacetate or monobasic aluminum acetate.

[0006] According to the state of the art, the first synthetic route for the production of acetic alumina is considered to be the reaction of aluminum sulfate with lead acetate. The production of acetic alumina and its use in the production of colloidal aluminum oxide are described in Walter Crum's publication "On the acetates and other compounds of alumina," Proc. Royal Phil. 1853 (W. Crum, Annalen, 59:156 (1854)).

[0007] KIYOHARA et al. [KIYOHARA, Pedro K. et al.: Structure, Surface Area and Morphology of Aluminas from thermal decomposition of AI(OH)(CHsCOO)2 Crystals. In: An. Acad. Bras. Ci., 2000, Vol. 72 Iss. 4, pp. 471-495.] describe a synthesis for the preparation of aluminum diacetate AI(OH)(CHSCOO)2 by reacting powdered aluminum with aqueous acetic acid at 96°C. The resulting crystallites were characterized by X-ray diffraction (XRD) and assigned to aluminum diacetate (card no.: 13-0833) via ICDD (International Centre for Diffraction Data).

[0008] The publication US 6,498,262 B2 or US 2002 / 0 137 960 A1 claims the production of basic aluminum diacetate (aluminum diacetate monobasic) starting from sodium aluminate, sodium acetate, and aluminum chloride at reaction temperatures between 50 °C and 100 °C. The resulting aluminum diacetate was characterized by X-ray diffraction only above a scattering angle of 2 0 = 12°.

[0009] CLAR et al. [CLAR, C. et al.: Synthesis and characterization of aluminum carboxylate gels. In: Thermochimica Acta 2003, Vol. 407, pp. 33–40.] synthesized gels of aluminum formate and aluminum acetate and characterized them by XRD. The resulting crystal reflections were assigned, among other things, to aluminum diacetate using card no. 13-0833.

[0010] A disadvantage of all currently known processes for producing aluminum diacetate is that the products obtained by various synthesis routes are mixtures of several crystalline compounds. Furthermore, the crystal structures of the crystalline phases occurring in the products are structurally unknown.

[0011] The properties also differ considerably with regard to the absorption of moisture and other guest molecules, which limits their use, especially in applications where high purity is important.

[0012] Nevertheless, there are various publications in which possible applications of aluminum diacetate compounds are disclosed or in which an application would be theoretically possible, even if not explicitly shown in the respective publication.

[0013] The document DE 11 2021 005 746 T5 discloses a lithium-ion battery material based on a lithium transition metal oxide material and its production in which, among other things, aluminum diacetate with the associated formula AI(OH)(CHsCOO)2 is used.

[0014] Furthermore, publication DE 11 2020 003 391 T5 describes a porous solar wavelength conversion material containing luminescent aluminum hydroxide. Aluminum diacetate could theoretically be chosen as the aluminum hydroxide precursor.

[0015] The document EP 2 475 750 B1 describes a process for the purification of biomass using aluminum acetate.

[0016] The document EP 2 934427 B1 claims a dental retraction composition which contains astringent aluminum acetate to stop bleeding.

[0017] Furthermore, the document EP 3 000 835 B1 describes a catalyst material which can be used in the production of polyesters and contains aluminum acetate as a co-catalyst.

[0018] The document EP 3 512 486 B2 claims a cosmetic colorant which comprises complexed aluminum from aluminum diacetate.

[0019] In document EP 3 058 945 B1, aluminum acetate is used as an additional component of a mixture for the treatment of skin diseases.

[0020] The problems with the prior art are essentially, as previously described, that all currently known processes for producing aluminum diacetate using various synthesis routes yield products that are mixtures of several crystalline compounds. Furthermore, the crystal structures of the crystalline phases occurring in the products are structurally unknown.

[0021] The application of aluminum diacetate is currently limited by its inconsistent properties, particularly with regard to the absorption of moisture and other guest molecules. The present invention is based on several objectives.

[0022] An object of the invention is to provide aluminum diacetate with improved properties.

[0023] A further object of the invention is to provide aluminum diacetate with defined Krista II structure and composition.

[0024] Furthermore, it is an object of the invention to provide aluminum diacetate with improved ability to absorb guest molecules.

[0025] In particular, it is an object of the invention to provide aluminum diacetate with improved ability to absorb guest molecules with a molecular weight of less than 300 g / mol.

[0026] In a further aspect, the object of the invention is to provide a process for producing aluminum diacetate with improved properties.

[0027] Furthermore, it is an object of the invention to provide a process for producing the aluminum diacetates according to the invention.

[0028] In particular, it is an object of the invention to provide a production process which can be carried out in aqueous media and at reaction temperatures between room temperature and 140°C with high yields, in particular of more than 90%.

[0029] In a particular aspect, it is an object of the invention to provide a process for preparing the aluminum diacetates according to the invention which can be carried out easily.

[0030] These objects are achieved with crystalline aluminum diacetate compounds according to claim 1 and a process for producing crystalline compounds according to claim 8 and a use according to claim 11.

[0031] The crystalline aluminum diacetate compound II is cis-trans-AI(OH)(CHsCOO)2.

[0032] Other crystalline aluminum diacetate compounds are characterized by the fact that the aluminum diacetate compounds correspond to the formula:

[0033] I. trans-AI(OH)(CH3COO)2 (compound I.) and / or

[0034] II. cis-trans-AI(OH)(CHsCOO)2 (compound II.) are formed in a pure phase. The compound I. can in particular have a crystal structure in which aluminum cations Al 3+ octahedrally coordinated with two OH' and four CHsCOO' ions as ligands, where one OH' ion coordinates two aluminum cations Al 3+ bridged ( 2-OH), where the octahedra with the composition [AI(|J2-OH)2(CH3COO)4)]3 ' are trans-corner-linked via 2-OH groups and form chains of the composition AI(OH)(CH3COO)2, with neighboring aluminum cations Al 3+ are linked via CHsCOO' ions and the chains are arranged parallel to each other in the unit cell.

[0035] The compound II. can in particular have a crystal structure in which aluminum cations Al 3+ octahedrally coordinated with two OH' and four CHsCOO' ions as ligands, where one OH' ion coordinates two aluminum cations Al 3+ bridged ( 2-OH), where the octahedra with the composition [AI( 2-OH)2(CHsCOO)4)] 3 ' in an alternating cis- and trans- corner linkage of the octahedra via 2-OH groups and the CHsCOO' ions are linked to zigzag-shaped cis-trans-AI(OH)(CHsCOO)2 chains and the chains are arranged parallel to each other in the unit cell.

[0036] The compound I. can be measured in the X-ray diffraction pattern with CuKa i-radiation should preferably be designed to have 20 reflections at the scattering angles 12.5, 14.1, 19.4, 22.8, 25.3, 25.5, 26.4, 28.8, 29.6, 30.3°.

[0037] In addition, the compound II. can be formed in the X-ray diffractogram measured with CuKai radiation preferably at the scattering angles 10.9, 14.3, 16.0, 16.4, 16.7, 20.2, 22.0, 23.1, 23.3, 26.0° having 20 reflections.

[0038] It was recognized that several crystalline compounds, i.e. more than one phase, exist side by side in aluminum diacetate and that these phases can be obtained separately from one another in pure phases by applying the process according to the invention for the preparation.

[0039] The phase-pure compound II is characterized by a zigzag structure unique for this class of compounds, which is formed by alternating cis-trans linkages of the [Al(p2- OH)2(CHsCOO)4)] 3'-octahedron is formed and creates a defined microporosity, which is not present in compound I with its linear chain structure.

[0040] Sorption measurements show that compound II, in contrast to compound I, exhibits significant porosity towards various vapors and other guest molecules, which determines its superiority for applications in gas storage and separation.

[0041] The pronounced substance-specific affinity and selectivity of compound II, demonstrated by different sorption capacities at differentiated vapor pressures, enables precisely controllable sorption processes that are not feasible with amorphous or non-phase-pure materials.

[0042] The crystal structure data of compound II show a structural flexibility with respect to the unit cell volume upon incorporation of different guest molecules, whereby the basic chain structure is retained and only the interchain distance varies.

[0043] An expansion of the unit cell volume is observed upon incorporation of guest molecules. The extent of this expansion is evident in the hkO reflections in the X-ray diffractogram and increases with the size of the incorporated molecules. In particular, the structural flexibility and ability to expand the structure upon incorporation of guest molecules can be observed in the X-ray diffractogram using the 110 reflection.

[0044] When toluene is included as a guest molecule, the unit cell volume is increased by 10%.

[0045] Based on the crystal structure data of compound II, a structural flexibility with respect to the unit cell volume is shown upon incorporation of different guest molecules, whereby the basic chain structure is retained and only the interchain distance varies.

[0046] The use of the phase-pure compound II with its defined crystalline structure allows an exact derivation of structure-property relationships, which is essential for targeted material design and reproducible industrial processes.

[0047] In a preferred embodiment, guest molecules can be incorporated into compound II.

[0048] The guest molecules can in particular be selected from the group of homonuclear and / or heteronuclear molecules with a molecular weight of less than 300 g / mol.

[0049] The process for producing crystalline aluminum diacetate compounds comprises the following steps: i. Providing an aqueous solution of an aluminum salt; ii. Adding acetic acid or its salts; iii. Adjusting the pH of the mixture; iv. Tempering the mixture; v. Separating the solid from the solution; vi. Washing the resulting solid; and vii. Drying the washed solid; wherein - step iii. and step iv. are coordinated such that

[0050] - for the preparation of compound I. a pH value between 0 and 4 and a temperature between 50 °C and 140 °C or a pH value between 0 and 6 and a temperature between 80 °C and 140 °C are set and

[0051] - for the preparation of compound II. a pH value between 4 and 6 and a temperature between 20 °C and 80 °C are set and

[0052] - the mixture, after carrying out step iii. and step iv., has a reaction time of between 15 minutes and 4 weeks under the set conditions before carrying out step v.

[0053] The main features of the procedure can be summarized as follows:

[0054] ■=> Compound II. (cis-trans-AI(OH)(CHsCOO)2) is formed only in a narrow pH window (pH = 4 - 6) and low reaction temperatures in phase-pure form (T = RT - 80 °C)

[0055] ■=> Compound I. (trans-AI(OH)(CHsCOO)2) is formed in a larger pH window in phase-pure form

[0056] • At low pH values ​​(< 4) only trans-AI(OH)(CHsCOO)2 is formed (independent of the temperature)

[0057] • In the pH range of 4-6, trans-AI(OH)(CH3COO)2 is formed in pure phase only at high reaction temperatures (> 80 °C)

[0058] Drying the washed solid in step vii can be accomplished in various ways. For example, the temperature can be increased to <120 °C, or it can be dried under vacuum, i.e., under reduced pressure, at room temperature. A drying agent such as zeolite, which absorbs water more strongly than the washed solid, can also be used.

[0059] A particularly advantageous feature of the preparation process according to the invention is that a one-pot reaction can be used, which can be carried out at low temperatures and in aqueous media.

[0060] In addition, yields of more than 90% can be achieved during synthesis.

[0061] The manufacturing process may optionally include the following additional steps:

[0062] - adding water to the mixture after step iii and before step iv and / or

[0063] - Cooling the mixture to room temperature after step iv and before step v.

[0064] There are preferably two options for incorporating guest molecules into compound II. Firstly, following step v., in which water molecules are present in the separated solid, these can be directly exchanged by stirring (step vi.) in a liquid (e.g., alcohols, toluene, etc.). Secondly, the water molecules can first be removed in step vii. (increase in temperature or decrease in pressure or drying agent) and then, following step vii., molecules can be introduced via the gas phase or from solutions. Loading is carried out in particular by stirring the dried, dewatered solid either in solutions of guest molecules or the pure liquid guest molecules (without additional solvent), or by exposing the dried, anhydrous solid to gases or vapors.

[0065] The crystalline aluminum diacetate compounds according to the invention can be used as shown below:

[0066] - in the production of lithium-ion battery material, and / or

[0067] - in the production of solar wavelength conversion material, and / or

[0068] - as an additive in dental reaction compositions, and / or

[0069] - as catalyst material and / or support material for catalysts, and / or

[0070] - as catalyst material and / or support material for catalysts for the production of polyester, and / or

[0071] - for the purification of biomass, and / or

[0072] - for the treatment of skin diseases and / or

[0073] - as an additive in cosmetic colorants.

[0074] The crystalline aluminum diacetate compounds II. can be used

[0075] - for the storage of substances, and / or

[0076] - for the separation of substances, and / or

[0077] - for cleaning fabrics and / or

[0078] - for drying substances. If guest molecules are incorporated into compound II, these can, as previously described, be molecules from the group of homonuclear and / or heteronuclear molecules with a molecular weight of less than 300 g / mol.

[0079] The compound II according to the invention can contain, in particular, water molecules as guest molecules.

[0080] The compound II. containing water molecules as guest molecules can be measured in the X-ray diffractogram with CuK a i-radiation should preferably be designed to have 20 reflections at the scattering angles 10.4, 10.9, 14.5, 14.8, 15.5, 16.5, 16.9, 17.1, 19.6, 20.8°.

[0081] In addition, the compound II according to the invention may contain methanol as guest molecules.

[0082] The compound II containing methanol as guest molecules can be formed in the X-ray diffractogram measured with CuKai radiation preferably at the scattering angles 10.3, 10.9, 14.1, 15.0, 16.0, 16.4, 17.1, 19.6, 21.4, 22.3° having 20 reflections.

[0083] The compound II according to the invention can also contain ethanol as guest molecules.

[0084] The compound II containing ethanol as guest molecules can be formed in the X-ray diffractogram measured with CuKai radiation, preferably at the scattering angles 10.3, 10.8, 14.2, 14.4, 15.2, 16.4, 16.6, 17.1, 19.5, 20.7°, exhibiting 20 reflections.

[0085] In a further embodiment, the compound II according to the invention can contain toluene as guest molecules.

[0086] The compound II containing toluene as guest molecules can be formed in the X-ray diffractogram measured with CuKai radiation preferably at the scattering angles 10.1, 11.1, 13.7, 14.2, 14.9, 16.0, 17.3, 19.8, 19.9, 21.8° 20.

[0087] When considering the unit cell of the crystalline aluminum diacetate compound II according to the invention, the following values ​​for the lengths of the axes are obtained.

[0088] For the crystalline aluminum diacetate compound II according to the invention without incorporation of guest molecules, which can be assigned to the monoclinic crystal system, the lengths of the axes of the unit cell can be in particular a = 13.9 ± 0.1 Å, b = 12.0 ± 0.1 Å, c = 12.3 ± 0.1 Å and angles of a = y = 90° and ß = 114 ± 1°.

[0089] For the crystalline aluminum diacetate compound II according to the invention with incorporation of water molecules as guest molecules, which can be assigned to the monoclinic crystal system, the lengths of the axes of the unit cell can be in particular a = 14.0 ± 0.1 Å, b = 11.9 ± 0.1 Å, c = 12.0 ± 0.1 Å and angles of a = y = 90° and ß = 119 ± 1°. For the crystalline aluminum diacetate compound II according to the invention with incorporation of methanol as guest molecules, which can be assigned to the monoclinic crystal system, the lengths of the axes of the unit cell can be in particular a = 14.1 ± 0.1 Å, b = 11.8 ± 0.1 Å, c = 12.1 ± 0.1 Å and angles of a = y = 90° and ß = 118 ± 1°.

[0090] For the crystalline aluminum diacetate compound II according to the invention with incorporation of ethanol as guest molecules, which can be assigned to the monoclinic crystal system, the lengths of the axes of the unit cell can be in particular a = 14.2 ± 0.1 Å, b = 11.9 ± 0.1 Å, c = 12.1 ± 0.1 Å and angles of a = y = 90° and ß = 119 ± 1°.

[0091] For the crystalline aluminum diacetate compound II according to the invention with incorporation of toluene as guest molecules, which can be assigned to the monoclinic crystal system, the lengths of the axes of the unit cell can be in particular a = 13.0 ± 0.1 Å, b = 12.5 ± 0.1 Å, c = 12.4 ± 0.1 Å and angles of a = y = 90° and ß = 107 ± 1°.

[0092] The synthesis of the phase-pure aluminum diacetate compounds according to the invention can be carried out as a rapid one-pot synthesis in aqueous media with very favorable starting materials.

[0093] Materials and methods

[0094] In the following, the invention is explained using examples without limiting the generality of the teaching.

[0095] Information on chemicals and equipment used is summarized in Tables 1 and 2.

[0096] Table 1 Chemicals used, manufacturers and purities. Table 2: Measurement methods and devices used.

[0097] Synthesis regulations:

[0098] 1a) Preparation of compound I frans-AI(OH)(CH3COO)2 in a 2 mL steel autoclave under hydrothermal conditions:

[0099] In a 2 mL Teflon vessel, 50 pL of water and 125 pL of an aqueous solution of Ah(SO4)3 (0.72 mol L 1 , 0.09 mmol). 375 pL (5.76 mol L' 1 , 2.16 mmol) diluted acetic acid and 450 pL (2 mol L' 1, 0.9 mmol) of diluted sodium hydroxide solution is added. The Teflon insert containing the reaction mixture (pH 3.5) is placed in a steel autoclave and sealed. The sealed steel autoclave is then heated in an oven at 130 °C for 20 hours.

[0100] After cooling to room temperature, the precipitate is separated by filtration and then washed twice with 1 mL of water and 1 mL of ethanol, and centrifuged again for separation. The colorless precipitate is then dried at room temperature for 12 hours. lb) Preparation of compound I (trans-AKOHHCHsCOOh) in a 14 mL Duran® glass reactor at 100 °C:

[0101] In a 14 mL Duran(ß^) glass reactor, 0.4 mL of water and 1.00 mL of an aqueous solution of Al2(SO4)s (0.72 mol L' 1 , 0.72 mmol). 3 mL (5.76 mol L 1 , 17.3 mmol) diluted acetic acid and 3.6 mL (2 mol L' 1, 7.2 mmol) of diluted sodium hydroxide solution is added. The glass reactor containing the reaction mixture (pH 3.5) is sealed and heated in an aluminum block for 20 hours with stirring at 100 °C.

[0102] After cooling to room temperature, the precipitate is separated by centrifugation in 15 mL centrifuge tubes for 10 minutes at a speed of 10,000 rpm. It is then washed twice with water and ethanol and centrifuged again for separation. The colorless precipitate is then dried at room temperature for 12 hours. lc) Preparation of compound AKOHHCHsCOOh in a 250 mL round-bottom flask under Return flow (rf):

[0103] 9.6 g (14.4 mmol) of Ah(SO4)3 x 18 H2O are dissolved in 68.2 mL of H2O in a 250 mL round-neck flask. A solution of 72 mL of an aqueous sodium hydroxide solution (2 mol L') is added to this solution. 1, 144 mmol) and 19.8 mL of acetic acid (100%, 346 mmol). The solution (pH 3.5) is heated and stirred under reflux for 20 hours. After cooling to room temperature, the colorless precipitate is separated by filtration and then washed with 50 mL each of water and ethanol. The mixture is then dried at room temperature for 12 hours.

[0104] 1 d) Preparation of compound I frans-AKOHHCHsCOOh in a 10 L round-bottom flask under reflux (rf):

[0105] 600 g (0.9 mol) of AI2(SO4)3 x 18 H2O are dissolved in 4.26 L H2O in a 10 L round-neck flask. A solution of 4.5 L of an aqueous sodium hydroxide solution (2 mol L- 1, 9 mol) and 1.24 L of acetic acid (100%, 21.6 mol). The solution (pH 3.5) is heated and stirred under reflux for 20 hours. After cooling to room temperature, the colorless precipitate is separated by filtration and then washed with 500 mL of water and 500 mL of ethanol. The mixture is then dried at room temperature for 12 hours. 2a) Preparation of compound II c / 's-frans-AKOHHCHsCOOh • 2 H2O in a 2 mL steel autoclave:

[0106] In a 2 mL Teflon vessel, 146 pL of water and 375 pL of an aqueous solution of Ah(SO4)3 (0.72 mol L 1 , 0.27 mmol). 417 pL (4.32 mol L' 1 ,

[0107] 1.8 mmol) of an aqueous solution of sodium acetate (NaC CCHs) and 62.5 pL (5.76 mol L' 1, 0.36 mmol) of diluted acetic acid is added. The Teflon insert containing the reaction mixture (pH 4.5) is placed in a steel autoclave and sealed. The sealed steel autoclave is then heated in an oven at 50 °C for 20 hours.

[0108] After cooling to room temperature, the precipitate is separated by filtration and then washed twice with 1 mL of water and 1 mL of ethanol, and centrifuged again for separation. The colorless precipitate is then dried at room temperature for 12 hours.

[0109] 2b) Preparation of compound II c / 's-frans-AKOHHCHsCOOh • 2 H2O in a 14 mL Duran® glass reactor at 50 °C:

[0110] In a 14 mL Duran®^Glase reactor, 1.17 mL of water and 3 mL of an aqueous solution of Al2(SO4)5 (0.72 mol L' 1 , 2.16 mmol). 3.34 mL (4.32 mol L' 1, 14.4 mmol) of an aqueous solution of sodium acetate (NaO2CCHs) and 500 pL (5.76 mol L' 1 , 2.88 mmol) of diluted acetic acid is added. The glass reactor containing the reaction mixture (pH 4.5) is sealed and heated in an aluminum block for 20 hours with stirring at 50 °C.

[0111] After cooling to room temperature, the precipitate is separated by centrifugation in 15 mL centrifuge tubes for 10 minutes at a speed of 10,000 rpm. It is then washed twice with water and ethanol and centrifuged again for separation. The colorless precipitate is then dried at room temperature for 12 hours.

[0112] 2c) Preparation of compound II c / 's-frans-AKOHXCHsCOOh - 2 H2O in a 250 mL round-bottom flask:

[0113] 28.8 g (43.2 mmol) of AI2(SO4)3 x 18 H2O are dissolved in 92.2 mL of H2O in a 250 mL round-bottomed flask. A solution of 48 mL of an aqueous sodium hydroxide solution (6 mol L') is added to this solution. 1 , 288 mmol) and 19.8 mL of acetic acid (100%, 346 mmol). The solution (pH 4.5) is heated to 50 °C and stirred for 20 hours. After cooling to room temperature, the colorless precipitate is separated by filtration and then washed with 50 mL each of water and ethanol. The mixture is then dried at room temperature for 12 hours.

[0114] 2d) Preparation of compound AI(OH)(CH3COO)2 • 2 H2O in a 10 L round-bottomed flask:

[0115] 1799 g (2.7 mol) of Ah(SO4)3x 18 H2O are dissolved in 5.76 L H2O in a 10 L round-neck flask. To this solution is added a solution of 3 L of an aqueous sodium hydroxide solution (6 mol L' 1, 18 mol) and 1.24 L of acetic acid (100%, 21.6 mol). The solution (pH = 4.5) is stirred at 50 °C for 20 h. After cooling to room temperature, the colorless precipitate is separated by filtration and then washed with 500 mL of water and 500 mL of ethanol. The mixture is then dried at room temperature for 12 hours.

[0116] The specific surface areas of the phase-pure aluminum diacetate compounds were determined according to the formula:

[0117] I. trans-AI(OH)(CH3COO)2and

[0118] II. cis-trans-AI(OH)(CH3COO)2 was determined by nitrogen sorption measurements at a temperature of 77 K. The results are shown in Table 3.

[0119] Table 3: Specific surface areas determined by nitrogen sorption measurements (77 K) and maximum vapor uptake capacities (water, methanol, ethanol, toluene uptake at p / po = 0.9) of the compounds according to the invention frans-AI(OH)(CHsCOO)2 and c / s-frans-AI(OH)(CH3COO)2 • 2 H2O determined by vapor sorption measurements (298 K).

[0120] The vapor sorption isotherms were determined at 298 K.

[0121] Prior to sorption measurements, the samples were activated at 70 °C under reduced pressure. The results are plotted with a logarithmic x-axis in Fig. 6.

[0122] The invention is described below with reference to the accompanying figure in the description of the figure, which is intended to illustrate the invention and is not to be considered limiting. It shows:

[0123] Fig. 1 is an exemplary schematic representation of the Krista II structure of a crystalline aluminum diacetate compound I.;

[0124] Fig. 2 is an exemplary schematic representation of the crystal structure of a crystalline aluminum diacetate compound II.;

[0125] Fig. 3 exemplary X-ray powder diffractograms of compound I. and compound II.;

[0126] Fig. 4 exemplary X-ray powder diffractograms of compound I and compound II under different reaction conditions;

[0127] Fig. 5 exemplary X-ray powder diffractograms of compound II with various incorporated guest molecules;

[0128] Fig. 6 Vapor sorption isotherms of compound I (filled symbols) and II (open symbols), recorded at 298 K and plotted with a logarithmic x-axis and

[0129] Fig. 7 an X-ray diffractogram of the compound II according to the invention with 110 reflection upon incorporation of various guest molecules.

[0130] Fig. 1 shows a crystalline compound I. (trans-AI(OH)(CHsCOO)2) having a

[0131] Krista II structure in which aluminum cations Al 3+ octahedrally coordinated by two OH- and four CH3COO' ions as ligands, with one OH- ion binding two aluminum cations Al 3+ bridged (p2-OH) and where the octahedra with the composition [AI( 2-OH)2(CH3COO)4)] 3 ' are trans-corner-linked via 2-OH groups and form chains of the composition AI(OH)(CHsCOO)2 and where adjacent aluminum cations Al 3+ are linked via CHsCOO' ions, and the chains are arranged parallel to each other in the unit cell. Figures 1a) and 1b) each show different views of the crystalline compound I. in the Cartesian coordinate system.

[0132] Fig. 2 shows a crystalline compound II. (cis-trans-AI(OH)(CHsCOO)2) having a

[0133] Krista II structure in the aluminum cations Al 3+octahedrally coordinated with two OH' and four CHsCOO' ions as ligands, where one OH' ion coordinates two aluminum cations Al 3+ bridged (P2-OH) and the octahedra with the composition

[0134] [AI(2-OH)2(CH3COO)4)] 3 ' are linked in an alternating cis- and trans-corner connection of the octahedra via 2-OH groups and the CHsCOO' ions to form zigzag-shaped cis-trans-AI(OH)(CHsCOO)2 chains, with the chains arranged parallel to each other in the unit cell. Figures 2a) and 2b) each show different views of the crystalline compound II in the Cartesian coordinate system.

[0135] In Fig. 3, measured (a) and calculated (b) X-ray powder diffractograms of compound I. (I) and compound II. (II) are shown.

[0136] Fig. 4 shows X-ray powder diffractograms of compound I. and compound II. prepared under different reaction conditions (ad).

[0137] In addition, Fig. 5 shows X-ray powder diffractograms of compound II with different embedded guest molecules (water (g), methanol (h), ethanol (i), toluene (j)) and without embedded guest molecules (k).

[0138] Fig. 6 shows vapor sorption isotherms of compound I (filled symbols) and II (open symbols), recorded at 298 K and plotted with a logarithmic x-axis. Prior to sorption measurements, the samples were activated at 70 °C under reduced pressure.

[0139] Fig. 7 shows an X-ray diffractogram of compound II with 110 reflection upon incorporation of various guest molecules.

Claims

CLAIMS 1. Crystalline aluminum diacetate compound II. corresponding to the formula cis-trans-AI(OH)(CH3COO)2.

2. Compound II. according to claim 1, characterized in that the aluminum diacetate compound is formed in a pure phase.

3. Compound II. according to claim 1 or 2, characterized in that the compound II. has a crystal structure in which aluminum cations Al 3+ octahedrally coordinated with two OH' and four CH3COO ions as ligands, where - one OH' ion two aluminum cations Al 3+ bridged (p2-OH); - the octahedra with the composition [AI(2-OH)2(CH3COO)4)] 3 ' in an alternating cis- and trans-corner connection of the octahedra via p2-OH groups and the CHsCOO' ions are linked to zigzag-shaped cis-trans-AI(OH)(CH3COO)2 chains and - the chains in the unit cell are arranged parallel to each other.

4. Compound II. according to claim 1, 2 or 3, characterized in that the compound is formed having 20 reflections in the X-ray diffractogram measured with CuKai radiation at the scattering angles 10.9, 14.3, 16.0, 16.4, 16.7, 20.2, 22.0, 23.1, 23.3, 26.0°.

5. Compound II. according to claim 1, 2, 3 or 4, characterized in that guest molecules can be incorporated into the compound.

6. Compound II. according to claim 5, characterized in that the compound has a structural flexibility due to expansion of the unit cell volume upon incorporation of guest molecules.

7. Compound II. according to claim 5 or 6, characterized in that the guest molecules are selected from the group of homonuclear and / or heteronuclear molecules having a molecular weight of less than 300 g / mol.

8. A process for the preparation of crystalline aluminum diacetate compounds, in particular according to one of claims 1 to 7, comprising the following steps: i. Providing an aqueous solution of an aluminum salt; ii. Adding acetic acid or salts thereof; iii. Adjusting the pH of the mixture; iv. Tempering the mixture; v. Separating the solid from the solution; vi. Washing the resulting solid; and vii. Drying the washed solid; wherein - steps iii and iv are coordinated in such a way that - for the preparation of compound I. a pH value between 0 and 4 and a temperature between 50 °C and 140 °C or a pH value between 0 and 6 and a temperature between 80 °C and 140 °C are set and - for the preparation of compound II. a pH value between 4 and 6 and a temperature between 20 °C and 80 °C are set and - the mixture, after carrying out steps iii and iv, has a reaction time of between 15 minutes and 4 weeks under the set conditions before carrying out step v.

9. Method according to claim 8, characterized in that - after step iii and before step iv, water is added to the mixture and / or - after step iv. and before step v. the mixture is cooled to room temperature.

10. The method according to claim 8 or 9, characterized in that an incorporation of guest molecules into compound II is carried out, wherein - an exchange of water molecules present in the separated solid from step v. takes place by washing with a solution of guest molecules in step vi. or - after obtaining the dried solid in step vii., the solid is loaded in solutions of guest molecules or the pure liquid guest molecules or in gases or vapors of the guest molecules.

11. Use of the phase-pure crystalline aluminum diacetate compound according to one of claims 1 to 7 and / or phase-pure crystalline aluminum diacetate compound prepared by the process for preparing crystalline aluminum diacetate compounds according to one of claims 8 to 10: - in the production of lithium-ion battery material; and / or - in the production of solar wave conversion material; and / or - as an additive in dental reaction compositions; and / or - as catalyst material and / or support material for catalysts; and / or - as catalyst material and / or support material for catalysts for the production of polyester; and / or - for the purification of biomass; and / or - for the treatment of skin diseases and / or - as an additive in cosmetic colorants.

12. Use of the crystalline aluminum diacetate compound II. according to any one of claims 1 to 7 - for the storage of substances; and / or - for the separation of substances; and / or - for the cleaning of substances and and / or - for drying fabrics.

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