Heterogeneous catalytic method for producing 2,2,6,6-tetramethyl-4-piperidone

Abstract

The present invention relates to a process for producing 2,2,6,6-tetramethyl-4-piperidone, particularly comprising (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure FAU, wherein the zeolite material contains YO2 and X2O3 in its framework structure, where Y is a tetravalent element and X is a trivalent element, and wherein the zeolite material has a YO2 / X2O3 molar ratio of 16 - 175; (ii) preparing a reaction mixture comprising acetone and ammonia; (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C to obtain a reaction product comprising 2,2,6,6-tetramethyl-4-piperidone; wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

Description

Technical Field

[0001] The present invention relates to a process for producing 2,2,6,6-tetramethyl-4-piperidone.

[0002] Introduction

[0003] 2,2,6,6-Tetramethyl-4-piperidone is used as a key intermediate in industrial organic chemistry. The preparation of 2,2,6,6-tetramethyl-4-piperidone is usually carried out by a continuous or semi-continuous process via a complex equilibrium system, in which acetone is converted with ammonia in the presence of a catalyst. Ammonium salts are generally used as homogeneous catalysts. The type of conversion can be classified as a ring condensation reaction, thereby releasing water. The work-up procedure is usually carried out by extraction with caustic soda to remove water and neutralize the catalyst. The acetone residue is then separated from the organic phase which is subsequently fractionated.

[0004] Cavani et al. disclosed studies on the acid-catalyzed condensation of acetone and ammonia for the direct production of 2,2,6,6-tetramethyl-4-piperidone under both homogeneous and heterogeneous conditions, in which aqueous ammonia was used as the ammonia source. H-Y zeolites with selected characteristics were tested as catalysts. It has been found that by-products are formed during the preparation of 2,2,6,6-tetramethyl-4-piperidone. The by-products may contain diacetone alcohol, diacetoneamine, mesityl oxide, 1,2,5,6-tetrahydro-2,2,4,6,6-pentamethylpyrimidine and 2,2,4,6-tetramethyl-2,3-dihydropyridine, with the latter being the most undesirable by-product as its formation was found to be irreversible. According to Cavani et al., 1,2,5,6-tetrahydro-2,2,4,6,6-pentamethylpyrimidine can insert water and eliminate ammonia or insert acetone in the presence of acetone and eliminate 2-iminopropane to be converted into 2,2,6,6-tetramethyl-4-piperidone. In addition, it was found that for H-Y zeolites with different silica / alumina ratios (SAR = 6; 15; 200), the lower the SAR, the higher the selectivity to 2,2,6,6-tetramethyl-4-piperidone, while the selectivity to the undesirable 2,2,4,6-tetramethyl-2,3-dihydropyridine was the highest for the H-Y zeolite with an SAR of 15 and the lowest for the H-Y zeolite with an SAR of 6.

[0005] CN 107033066 A particularly relates to a method and a special device for the heterogeneous catalytic synthesis of 2,2,6,6 - tetramethyl - 4 - piperidone. As the heterogeneous catalyst, a Lewis acid catalyst insoluble in water and acetone can be used, including one or more complexes of ion exchange resin, molecular sieve - type catalyst, (doped) metal oxide, (doped) metal hydroxide, or solid organic sulfonic acid, solid organic carboxylic acid, supported metal halide, supported organic ammonium salt, or solid superacid. In Example 1, an exchange resin modified with organic sulfonic acid was used; in Example 2, a molecular sieve loaded with iron chloride was used; in Example 3, a catalyst modified with nano - alumina was used; in Example 4, a catalyst modified with nano - alumina and an ion exchange resin modified with organic sulfonic acid was used; and in Example 5, a catalyst modified with nano - alumina and a molecular sieve catalyst loaded with iron chloride was used. The method includes using a heterogeneous catalyst to react acetone with ammonia in a reaction kettle at 60 - 75 °C for 7 hours, where a water separator is used to separate water from the reaction mixture. After post - treatment, the crude 2,2,6,6 - tetramethyl - 4 - piperidone is purified by distillation. In the disclosed method, ion exchange resin or molecular sieve can be used as the Lewis acid catalyst.

[0006] J. Tian et al. disclosed a study on the effect of HY zeolite on the continuous synthesis of 2,2,6,6 - tetramethyl - 4 - piperidone, in which HZSM - 5 and H - β zeolites were also tested. Several different zeolites were disclosed for the synthesis of 2,2,6,6 - tetramethyl - 4 - piperidone. It has been found that the most effective zeolite in this regard is H - Y zeolite with a silica / alumina molar ratio of 11.2, which achieved an acetone conversion of 46.2% and a selectivity of 2,2,6,6 - tetramethyl - 4 - piperidone of 44.1%. In contrast, H - β zeolite with a silica / alumina molar ratio of 50 achieved an acetone conversion of 15.8% and a selectivity of 2,2,6,6 - tetramethyl - 4 - piperidone of 15.3%. In addition, using H - ZSM - 5 zeolite with a silica / alumina molar ratio of 50 only achieved a low conversion rate (5.6%), where only trace amounts of 2,2,6,6 - tetramethyl - 4 - piperidone were produced. Therefore, J. Tian et al. considered using H - Y zeolite with a relatively low silica / alumina molar ratio instead of any other zeolite used in other tests in terms of reaction conditions.

[0007] Therefore, there is a need to develop an improved method for producing 2,2,6,6 - tetramethyl - 4 - piperidone in which the formation of by - products is avoided or at least reduced.

[0008] Detailed description

[0009] Accordingly, an object of the present invention is to provide an improved process for producing 2,2,6,6-tetramethyl-4-piperidone, particularly with respect to the improved selectivity of 2,2,6,6-tetramethyl-4-piperidone. Specifically, the object is to provide a process in which the selectivity for 2,2,6,6-tetramethyl-4-piperidone is improved over a long reaction time. Thus, the object is in particular to avoid or at least reduce the formation of by-products.

[0010] Surprisingly, it has now been found that the use of a catalyst comprising a zeolite material having a specific silica / alumina molar ratio in a heterogeneous process for producing 2,2,6,6-tetramethyl-4-piperidone results in an improved selectivity for 2,2,6,6-tetramethyl-4-piperidone, in particular with a reduction in the formation of by-products. Further, and in contrast to homogeneous processes, the heterogeneous process allows for simple recycling since the heterogeneous phase is easily separable from the reaction mixture and does not have to be separated from the reaction mixture.

[0011] In addition, it has been found completely unexpectedly that the catalyst does not undergo significant deactivation during the reaction.

[0012] Accordingly, the present invention relates to a process for producing 2,2,6,6-tetramethyl-4-piperidone, comprising:

[0013] (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure selected from EMT, GME, OFF, FER, HEU, MEL, MWW, RRO, TON, FAU, and mixtures of two or more thereof, wherein the zeolite material contains YO2 and X2O3 in its framework structure, where Y is a tetravalent element and X is a trivalent element, and wherein the zeolite material has a YO2 / X2O3 molar ratio of 12 or greater;

[0014] (ii) preparing a reaction mixture comprising acetone and ammonia;

[0015] (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C to obtain a reaction product comprising 2,2,6,6-tetramethyl-4-piperidone;

[0016] wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

[0017] Preferably, the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 8% by weight, more preferably less than 6% by weight, more preferably less than 4% by weight, more preferably less than 2% by weight, more preferably less than 1% by weight, more preferably less than 0.5% by weight, more preferably less than 0.1% by weight, more preferably less than 0.05% by weight, more preferably less than 0.01% by weight of water based on 100% by weight of the reaction mixture.

[0018] Preferably, the zeolite material has a framework structure selected from EMT, GME, FER, MWW, FAU, and mixtures of two or more thereof, more preferably a framework structure selected from FER, FAU, and mixtures thereof, and more preferably the zeolite material has a framework structure of FAU.

[0019] In one embodiment, the present invention relates to a process for producing 2,2,6,6 - tetramethyl - 4 - piperidone, comprising:

[0020] (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure of FAU, wherein the zeolite material contains YO2 and X2O3 in its framework structure, where Y is a tetravalent element and X is a trivalent element, and wherein the zeolite material has a YO2 / X2O3 molar ratio of 12 or greater;

[0021] (ii) preparing a reaction mixture comprising acetone and ammonia;

[0022] (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C

[0023] to obtain a reaction product comprising 2,2,6,6 - tetramethyl - 4 - piperidone; wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

[0024] Preferably, 5% by weight or more, more preferably 10% by weight or more, more preferably 30% by weight or more, more preferably 50% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more, more preferably 95 - 100% by weight, preferably 99 - 100% by weight of the catalyst consists of the zeolite material, and more preferably 99.5 - 100% by weight of the catalyst consists of the zeolite material.

[0025] Preferably, the catalyst is provided as a powder and / or a molded article, preferably as an extrudate.

[0026] According to the present invention, a molded article should be understood as a three - dimensional entity obtained by a shaping method; thus, the term "molded article" is used synonymously with the term "shaped body".

[0027] Preferably, Y is selected from Si, Sn, Ti, Zr, Ge, and mixtures of two or more thereof, where preferably Y is Si and / or Ti, and more preferably Y is Si.

[0028] Preferably, X is selected from B, Al, Ga, In, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and mixtures of two or more thereof, preferably selected from B, Al, Ga, In, and mixtures of two or more thereof, where preferably X is Al and / or B, and more preferably X is Al.

[0029] In another embodiment, the present invention relates to a method for producing 2,2,6,6-tetramethyl-4-piperidone, comprising:

[0030] (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure FAU, where the zeolite material contains YO2 and X2O3 in its framework structure, where Y is a tetravalent element and X is a trivalent element, and where the zeolite material has a YO2 / X2O3 molar ratio of 16 - 175;

[0031] (ii) preparing a reaction mixture comprising acetone and ammonia;

[0032] (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C to obtain a reaction product comprising 2,2,6,6-tetramethyl-4-piperidone;

[0033] where the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

[0034] There is no particular limitation on the YO2 / X2O3 molar ratio of YO2 and X2O3 contained in the zeolite material. Preferably, the zeolite material has a YO2 / X2O3 molar ratio of 13 or greater, more preferably in the range of 13 - 300, preferably 14 - 250, more preferably 15 - 200, more preferably FNMR, more preferably 17 - 150, more preferably 18 - 125, more preferably 19 - 100, more preferably 20 - 90, more preferably 21 - 80, more preferably 22 - 70, more preferably 22.5 - 60, more preferably 23 - 50, more preferably 23.5 - 45, more preferably 24 - 40, more preferably 24.5 - 37, more preferably 25 - 35, more preferably 25 - 30.

[0035] As disclosed above, it is preferred that the zeolite material has a FAU framework structure type. Particularly preferably, when the zeolite material has a FAU framework structure type, the zeolite material contains one or more selected from Li-LSX, zeolite X, zeolite Y, ECR-30, ZSM-20, LZ-210, SAPO-37, US-Y, CSZ-1, ZSM-3, faujasite, and mixtures of two or more thereof, more preferably selected from zeolite X, zeolite Y, ECR-30, ZSM-20, LZ-210, US-Y, CSZ-1, ZSM-3, faujasite, and mixtures of two or more thereof, more preferably selected from zeolite X, zeolite Y, ZSM-20, ZSM-3, faujasite, and mixtures of two or more thereof, more preferably selected from zeolite X, zeolite Y, faujasite, and mixtures of two or more thereof, zeolites having a FAU-type framework structure, wherein more preferably the one or more zeolites having a FAU-type framework structure comprise zeolite X and / or zeolite Y, preferably zeolite Y, wherein more preferably the one or more zeolites having a FAU-type framework structure are zeolite X and / or zeolite Y, preferably zeolite Y.

[0036] Preferably, the zeolite material is in the ammonium form or the H form, more preferably in the H form.

[0037] There are no particular restrictions on the chemical or physical properties of the zeolite material. Preferably, the zeolite material contains an acid site concentration in the range of 0.100 - 4.000 mmol / g at a temperature in the range of 190 - 550 °C, more preferably contains an acid site concentration in the range of 0.200 - 2.000 mmol / g at a temperature in the range of 205 - 400 °C, more preferably contains an acid site concentration in the range of 0.250 - 1.000 mmol / g at a temperature in the range of 250 - 290 °C, more preferably contains an acid site concentration in the range of 0.300 - 0.800 mmol / g at a temperature in the range of 350 - 375 °C, more preferably contains an acid site concentration in the range of 0.400 - 0.700 mmol / g at a temperature in the range of 360 - 366 °C, which is preferably determined by temperature-programmed desorption of ammonia (NH3-TPD) [according to Reference Example 2].

[0038] The temperature-programmed desorption of ammonia (NH3-TPD) was carried out in an automated chemisorption analysis unit (Micromeritics AutoChem II 2920) equipped with a thermal conductivity detector. The continuous analysis of the desorbed species was accomplished using an on-line mass spectrometer (OmniStar QMG200 from Pfeiffer Vacuum). A sample (0.1 g) was introduced into a quartz tube and analyzed using the following procedure. The temperature was measured by a Ni / Cr / Ni thermocouple immediately above the sample in the quartz tube. He with a purity of 5.0 was used for the analysis. A blank sample was analyzed for calibration prior to any measurement.

[0039] 1. Preparation: Start recording; measure once per second. Wait for 10 minutes at 25 °C and a He flow rate of 30 cm 3 / min (room temperature (ca. 25 °C) and 1 atm); heat to 600 °C at a heating rate of 20 K / min; hold for 10 minutes. Cool to 100 °C (furnace slope temperature) at a cooling rate of 20 K / min under a He flow (30 cm 3 / min); cool to 100 °C (sample slope temperature) at a cooling rate of 3 K / min under a He flow (30 cm 3 / min).

[0040] 2. Saturation with NH3: Start recording; measure once per second. Change the gas flow to a 10% NH3 in He mixture (75 cm 3 / min; 100 °C and 1 atm) at 100 °C; hold for 30 minutes.

[0041] 3. Removal of excess: Start recording; measure once per second. Change the gas flow to a He flow of 75 cm 3 / min (100 °C and 1 atm) at 100 °C; hold for 60 minutes.

[0042] 4. NH3-TPD: Start recording; measure once per second. Heat to 600 °C at a heating rate of 10 K / min under a He flow (flow rate: 30 cm 3 / min); hold for 30 minutes.

[0043] 5. End of measurement.

[0044] The desorbed ammonia was measured using the on-line mass spectrometer, which indicated that the signal from the thermal conductivity detector was caused by the desorbed ammonia. This involved using the m / z = 16 signal from ammonia to monitor the desorption of ammonia. The amount of ammonia adsorbed (mmol / g sample) was determined using Micromeritics software by integrating the TPD signal with respect to the horizontal baseline.

[0045] Furthermore, it is preferred that the zeolite material has an acid site concentration in the range of 0.050 - 0.600 mmol / g at a temperature in the range of 175 - 210 °C, more preferably an acid site concentration in the range of 0.140 - 0.530 mmol / g at a temperature in the range of 185 - 200 °C, and the acid site concentration is preferably determined by temperature-programmed desorption of ammonia (NH3-TPD) according to Reference Example 2.

[0046] Furthermore, it is preferred that the zeolite material has an acid site concentration in the range of 0.010 - 0.090 mmol / g at a temperature in the range of 475 - 625 °C, more preferably an acid site concentration in the range of 0.030 - 0.060 mmol / g at a temperature in the range of 500 - 600 °C, and the acid site concentration is preferably determined by temperature-programmed desorption of ammonia (NH3-TPD) according to Reference Example 2.

[0047] It is preferred that the zeolite material has a crystallinity in the range of 50 - 100 wt%, more preferably 75 - 100 wt%, more preferably 80 - 100 wt%, more preferably 90 - 100 wt%, and the crystallinity is preferably determined as described in Reference Example 3.

[0048] It is preferred that the zeolite material has a crystallinity in the range of 50 - 100 wt%, more preferably 75 - 100 wt%, more preferably 80 - 100 wt%, more preferably 90 - 100 wt%. The crystallinity is preferably determined by powder X-ray diffraction (PXRD) using a diffractometer (D8 Advance Series II, Bruker AXS GmbH) equipped with a LYNXEYE detector operated with a copper anode X-ray tube operating at 40 kV and 40 mA. The geometry is Bragg-Brentano and an air scattering baffle is used to reduce air scattering. The crystallinity of the sample is determined using the software DIFFRAC.EVA provided by Bruker AXS GmbH, Karlsruhe. The phase composition is calculated from the raw data using the modeling software DIFFRAC.TOPAS provided by Bruker AXS GmbH, Karlsruhe. The diffraction pattern is simulated using the crystal structures of the identified phases, the instrument parameters, and the grain size of each phase. This is suitable for data except for the function simulating the background intensity. The sample is homogenized in a mortar and then pressed into a standard flat sample holder provided by Bruker AXS GmbH to collect Bragg-Brentano geometry data. The flat surface is achieved by compressing and flattening the sample powder using a glass plate. Data is collected in the angular range 2 - 70° 2θ in steps of 0.02° 2θ while setting the variable divergence slit to an angle of 0.1°. The crystalline content describes the crystalline signal intensity relative to the total scattering intensity.

[0049] Preferably, the zeolite material has a volume-based particle size distribution characterized by a Dv50 value in the range of 4.0 - 7.0 μm, more preferably 4.5 - 6.5 μm, and even more preferably 5.0 - 6.0 μm.

[0050] There is no particular limitation on the content of YO2 contained in the zeolite material calculated as element Y. Preferably, YO2 calculated as element Y is contained in the zeolite material in the range of 35.0 - 47.0 wt%, more preferably 38.5 - 43.5 wt%, and even more preferably 40.0 - 42.0 wt% based on the total weight of the zeolite material.

[0051] There is no particular limitation on the content of X2O3 contained in the zeolite material calculated as X. Preferably, X2O3 calculated as X is contained in the zeolite material in the range of 1.0 - 4.5 wt%, more preferably 2.2 - 3.7 wt%, and even more preferably 2.9 - 3.3 wt% based on the total weight of the zeolite material.

[0052] Preferably, the zeolite material has a BET specific surface area equal to or greater than 380 m 2 / g, more preferably equal to or greater than 650 m 2 / g, and more preferably in the range of 700 - 800 m 2 / g, preferably measured as described in Reference Example 1.

[0053] Preferably, the zeolite material has a BET specific surface area equal to or greater than 380 m 2 / g, more preferably equal to or greater than 650 m 2 / g, and more preferably in the range of 700 - 800 m 2 / g, preferably measured by physical adsorption of nitrogen at 77 K according to the method disclosed in DIN 66131.

[0054] Preferably, the zeolite material has a Langmuir specific surface area equal to or greater than 500 m 2 / g, more preferably equal to or greater than 800 m 2 / g, and more preferably in the range of 810 - 1100 m 2 / g, preferably measured as described in Reference Example 1.

[0055] As disclosed above, preferably X contains Al, preferably Al. In the case where X contains Al, preferably Al, preferably the solid-state 27 Al NMR of the zeolite material shows peaks in the range of 80 - 40 ppm and peaks in the range of 40 - 15 ppm, and the ratio of the peak integral of the peaks in the range of 80 - 40 ppm to the peak integral of the peaks in the range of 40 - 15 ppm is at least 3:1, more preferably at least 7:1, and even more preferably at least 10:1, preferably measured as described in Reference Example 4.

[0056] As disclosed above, preferably X contains Al, preferably Al. In the case where X contains Al, preferably Al, preferably the solid state of the zeolite material 27 Al NMR shows peaks in the range of 80 - 40 ppm and peaks in the range of 40 - 15 ppm, wherein the ratio of the peak integral of the peaks in the range of 80 - 40 ppm to the peak integral of the peaks in the range of 40 - 15 ppm is at least 3:1, more preferably at least 7:1, more preferably at least 10:1, preferably via 27 Al solid state nuclear magnetic resonance (NMR) measurement.

[0057] 27 Al solid state nuclear magnetic resonance (NMR) is carried out as follows: The sample is stored at 62% relative humidity for at least 60 hours before loading; the sample is loaded into a 3.2 mm ZrO2 rotor with a Vespel cap, a Bruker Avance Neo spectrometer with a 14.1 Tesla magnet, 15 kHz (ω / 2π) magic angle spinning, single pulse radio frequency excitation corresponding to a 0.92 μs 15° pulse for an AlCl3 solution (1%, in H2O); 10 ms to obtain the free induction decay, without heteronuclear 1 H radio frequency decoupling, scanning average with a cycle delay of 0.5 s for at least 5120 times, Fourier transform with a 10 Hz exponential line broadening to suppress noise, manual phasing and baseline correction in Bruker Topspin 3.0. On an absolute chemical shift scale at a frequency ratio of 0.26056859 according to Pure Appl. Chem., Vol. 80, No. 1, pp. 59 - 84, 2008 using adamantane with a 13 C methylene resonance as a secondary standard for spectral localization relative to 1.1 mol / kg Al(NO3)3 in D2O.

[0058] Further, in the case where X contains Al, preferably Al, preferably the solid state of the zeolite material 27 Al NMR shows peaks in the range of 80 - 40 ppm and peaks in the range of 15 ppm to -20 ppm, wherein the ratio of the peak integral of the peaks in the range of 80 - 40 ppm to the peak integral of the peaks in the range of 15 ppm to -20 ppm is at least 3:1, more preferably at least 7:1, more preferably at least 10:1, preferably determined as described in Reference Example 4.

[0059] Preferably, the zeolite material has a micropore volume in the range of 0.180 - 0.390 ml / g, more preferably 0.220 - 0.350 ml / g, more preferably 0.260 - 0.310 ml / g, preferably determined as described in Reference Example 1.

[0060] Preferably, the zeolite material has an average pore diameter in the range of 4.0 - 18.0 nm, more preferably 5.5 - 8.0 nm, even more preferably 6.6 - 7.3 nm, and is preferably determined as described in Reference Example 1.

[0061] Preferably, the zeolite material has an average pore width in the range of 1.5 - 5.5 nm, more preferably 2.0 - 3.5 nm, even more preferably 2.4 - 2.8 nm, and is preferably determined as described in Reference Example 1.

[0062] Preferably, the zeolite material provided in (i) is a calcined zeolite material, wherein the zeolite material has been calcined at a temperature in the range of 300 - 900 °C, more preferably 400 - 700 °C, even more preferably 450 - 650 °C, even more preferably 500 - 600 °C.

[0063] Depending on the quality of the precursor of the molded article to be calcined, the duration of calcination should have been adjusted. Preferably, the zeolite material has been calcined for a duration of 0.5 - 24 hours, more preferably 1 - 15 hours, even more preferably 2 - 12 hours, even more preferably 2.5 - 9 hours, even more preferably 3 - 7 hours, even more preferably 3.5 - 6.5 hours, even more preferably 4 - 6 hours.

[0064] There are no particular restrictions on the other process steps. Preferably, the catalyst is washed with acetone before contacting with the reaction mixture in (ii). Preferably, the catalyst is first contacted with acetone before contacting with the reaction mixture in (ii).

[0065] There is no particular restriction on the temperature for contacting the catalyst with the reaction mixture prepared in (ii) in (iii). Preferably, the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a temperature in the range of 45 - 200 °C, more preferably 50 - 150 °C, even more preferably 55 - 120 °C, even more preferably 60 - 100 °C, even more preferably 65 - 90 °C, even more preferably 70 - 80 °C.

[0066] There is no particular restriction on the pressure for contacting the catalyst with the reaction mixture prepared in (ii) in (iii). Preferably, the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a pressure in the range of 1 - 200 bar (abs), more preferably 20 - 150 bar (abs), even more preferably 30 - 100 bar (abs), even more preferably 45 - 80 bar (abs), even more preferably 50 - 70 bar (abs), even more preferably 55 - 65 bar (abs).

[0067] As disclosed above, there is no particular limitation on the pressure for contacting the catalyst with the reaction mixture prepared in (ii) in (iii). It is preferred that the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a pressure in the range of 1 - 30 bar (abs), more preferably 1 - 20 bar (abs), more preferably 1 - 15 bar (abs), more preferably 1 - 10 bar (abs), more preferably 1 - 5 bar (abs), more preferably 1 - 3 bar (abs).

[0068] It is preferred that the method is carried out as a batch method or a continuous method. It is particularly preferred that the method is carried out as a continuous method.

[0069] As disclosed above, it is preferred that the method is carried out as a continuous method. When the method is carried out as a continuous method, it is preferred that the contacting in (iii) is carried out at a liquid hourly space velocity (LHSV) in the range of 0.01 - 1000 ml / (g·h), more preferably 0.05 - 500 ml / (g·h), more preferably 0.1 - 250 ml / (g·h), more preferably 0.3 - 100 ml / (g·h), more preferably 0.5 - 10 ml / (g·h), more preferably 1 - 5 ml / (g·h), more preferably 1.2 - 4 ml / (g·h), more preferably 1.5 - 3 ml / (g·h), more preferably 1.8 - 2.5 ml / (g·h), more preferably 2.0 - 2.2 ml / (g·h).

[0070] As disclosed above, the method may include other process steps. It is preferred that the method further includes:

[0071] (iv) separating 2,2,6,6 - tetramethyl - 4 - piperidone from the reaction product to obtain 2,2,6,6 - tetramethyl - 4 - piperidone and a residual mixture;

[0072] (v) recycling at least a part of the residual mixture to the reaction mixture in (ii),

[0073] wherein it is preferred to separate a compound having a boiling point higher than the boiling point of 2,2,6,6 - tetramethyl - 4 - piperidone from the residual mixture after (iv) and before (v).

[0074] There is no particular limitation on the molar ratio of acetone to ammonia in the reaction mixture prepared in (ii). It is preferred that the molar ratio of acetone to ammonia in the reaction mixture prepared in (ii) is in the range of 5:1 - 25:1, more preferably 7:1 - 22:1, more preferably 10:1 - 19:1, more preferably 13:1 - 16:1, more preferably 14.0:1.0 - 14.7:1.0, more preferably 14.2:1.0 - 14.5:1.0.

[0075] As disclosed above, the method can be carried out as a batch method. In the case where the method is carried out as a batch method, it is preferred that the contact in (iii) is carried out for a duration in the range of 0.1 - 24 hours, more preferably 0.5 - 20 hours, more preferably 1 - 15 hours, more preferably 3 - 10 hours, more preferably 4 - 8 hours, more preferably 5 - 7 hours.

[0076] As disclosed above, the catalyst can be provided as a molded article. In the case where the catalyst is provided as a molded article, it is preferred that the molded article is prepared according to a method comprising the following steps:

[0077] (a) Prepare a mixture comprising the zeolite material and optionally one or more binders;

[0078] (b) Shape the mixture, preferably by extrusion molding, to obtain a shaped material;

[0079] (c) Optionally dry the shaped material in a gas atmosphere;

[0080] (d) Calcinate the shaped material obtained from (b) or (c) in a gas atmosphere to obtain the molded article.

[0081] In the case where the method comprises (a), (b), (c) and (d) as disclosed above, it is preferred that the mixture comprises one or more binders, wherein the one or more binders are one or more of alumina, silica, silica - alumina, graphite, polysaccharides, sugar alcohols and synthetic polymers, more preferably one or more of alumina, silica, silica - alumina, graphite, sugar alcohols, synthetic polymers, cellulose, modified cellulose and starch, more preferably one or more of silica, alumina, silica - alumina, graphite, sugar alcohols, synthetic polymers, microcrystalline cellulose, cellulose ether, more preferably graphite, sorbitol, mannitol, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC) and sodium carboxymethylcellulose.

[0082] Further, in the case where the method comprises (a), (b), (c) and (d) as disclosed above, it is preferred that in the mixture according to (a), the weight ratio of the one or more binders to the zeolite material is in the range of 1:10 - 1:30, more preferably 1:15 - 1:25.

[0083] Further, in the case where the method comprises (a), (b), (c) and (d) as disclosed above, it is preferred that the method comprises drying according to (c), wherein the drying is carried out in a gas atmosphere at a temperature in the range of 90 - 150 °C, more preferably 110 - 130 °C, and wherein it is preferred that the drying is carried out for 10 - 15 hours, more preferably 11 - 13 hours.

[0084] Further, in the case where the method includes (a), (b), (c) and (d) as disclosed above, preferably the gas atmosphere in (d) has a temperature in the range of 400 - 600 °C, more preferably 450 - 550 °C, wherein preferably the calcination is carried out for 3 - 7 hours, more preferably 4 - 6 hours.

[0085] Further, in the case where the method includes (a), (b), (c) and (d) as disclosed above, preferably the gas atmosphere in one or more of (c) and (d) contains one or more of nitrogen, oxygen and argon, preferably nitrogen.

[0086] Within the meaning of the present invention, a specific value of relative humidity is not particularly restrictive with respect to the atmosphere of relative humidity showing said specific value, and thus in principle this value may relate to any suitable atmosphere of relative humidity showing said value, such as an atmosphere of air or an inert gas such as nitrogen, argon or a mixture thereof. However, according to the present invention, it is preferred that the specific relative humidity relates to the relative humidity of an atmosphere selected from air, nitrogen, argon and mixtures of two or more thereof, wherein more preferably the specific relative humidity relates to the atmosphere of nitrogen and / or argon showing the relative humidity of said level, and more preferably the atmosphere of nitrogen showing the relative humidity of said specific level.

[0087] According to the present invention, a molded article should be understood as a three-dimensional entity obtained by a molding method; thus, the term "molded article" is used synonymously with the term "molded body".

[0088] The unit bar (abs) relates to an absolute pressure of 10 5 Pa and the unit angstrom relates to a length of 10 -10 m.

[0089] The present invention is further illustrated by the following set of embodiments and the combinations of embodiments obtained from the shown dependencies and back references. In particular, it should be noted that in all cases where a certain range of embodiments is mentioned, for example with respect to terms such as "the method according to any one of embodiments 1 - 4", it is intended to clearly disclose to the skilled person each embodiment within that range, i.e., the wording of this term should be understood by the skilled person as being synonymous with "the method according to any one of embodiments 1, 2, 3 and 4". Furthermore, it should be clearly noted that the following set of embodiments is not the set of claims that determines the scope of protection, but rather represents a suitable constituent part of the description relating to the general and preferred aspects of the present invention.

[0090] 1. A method for producing 2,2,6,6 - tetramethyl - 4 - piperidone, comprising:

[0091] (i) Provide a reactor with a catalyst containing a zeolite material having a framework structure comprising a framework structure selected from EMT, GME, OFF, FER, HEU, MEL, MWW, RRO, TON, FAU, and a mixed structure of two or more of them, wherein the zeolite material contains YO₂ and X₂O₃ in its framework structure, where Y is a tetravalent element and X is a trivalent element, and wherein the zeolite material has a YO₂ / X₂O₃ molar ratio of 12 or greater;

[0092] (ii) Prepare a reaction mixture containing acetone and ammonia;

[0093] (iii) Contact the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C to obtain a reaction product containing 2,2,6,6 - tetramethyl - 4 - piperidone;

[0094] Wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight, preferably less than 8% by weight, more preferably less than 6% by weight, more preferably less than 4% by weight, more preferably less than 2% by weight, more preferably less than 1% by weight, more preferably less than 0.5% by weight, more preferably less than 0.1% by weight, more preferably less than 0.05% by weight, more preferably less than 0.01% by weight of water based on 100% by weight of the reaction mixture.

[0095] 2. The method of embodiment 1, wherein the zeolite material has a framework structure selected from EMT, GME, FER, MWW, FAU, and a mixed structure of two or more of them, preferably a framework structure selected from FER, FAU, and their mixed structures, and more preferably the zeolite material has a framework structure FAU.

[0096] 3. The method of embodiment 1 or 2, wherein 5% by weight or more, preferably 10% by weight or more, more preferably 30% by weight or more, more preferably 50% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more of the catalyst is composed of the zeolite material, and more preferably 95 - 100% by weight, preferably 99 - 100% by weight, more preferably 99.5 - 100% by weight of the catalyst is composed of the zeolite material.

[0097] 4. The method of any one of embodiments 1 - 3, wherein the catalyst is provided as a powder and / or a molded article, preferably as an extrudate.

[0098] 5. The method of any one of embodiments 1 - 4, wherein Y is selected from Si, Sn, Ti, Zr, Ge, and a mixture of two or more of them, wherein preferably Y is Si and / or Ti, and more preferably Y is Si.

[0099] 6. The method according to any one of embodiments 1-5, wherein X is selected from B, Al, Ga, In, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and mixtures of two or more thereof, preferably selected from B, Al, Ga, In, and mixtures of two or more thereof, wherein preferably X is Al and / or B, and wherein more preferably X is Al.

[0100] 7. The method according to any one of embodiments 1-6, wherein the zeolite material has a YO2 / X2O3 molar ratio of 13 or greater, preferably in the range of 13-300, preferably 14-250, more preferably 15-200, more preferably 16-175, more preferably 17-150, more preferably 18-125, more preferably 19-100, more preferably 20-90, more preferably 21-80, more preferably 22-70, more preferably 22.5-60, more preferably 23-50, more preferably 23.5-45, more preferably 24-40, more preferably 24.5-37, more preferably 25-35, more preferably 25-30.

[0101] 8. The method according to any one of embodiments 1-7, wherein the method for producing 2,2,6,6-tetramethyl-4-piperidone comprises:

[0102] (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure FAU, wherein the zeolite material contains YO2 and X2O3 in its framework structure, wherein Y is a tetravalent element and X is a trivalent element, and wherein the zeolite material has a YO2 / X2O3 molar ratio of 16-175;

[0103] (ii) preparing a reaction mixture comprising acetone and ammonia;

[0104] (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40-250 °C to obtain a reaction product comprising 2,2,6,6-tetramethyl-4-piperidone;

[0105] wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

[0106] 9. The method according to any one of embodiments 1-8, wherein the zeolite material has a FAU framework structure type, preferably the zeolite material contains one or more selected from Li-LSX, zeolite X, zeolite Y, ECR-30, ZSM-20, LZ-210, SAPO-37, US-Y, CSZ-1, ZSM-3, faujasite, and mixtures of two or more thereof, preferably selected from zeolite X, zeolite Y, ECR-30, ZSM-20, LZ-210, US-Y, CSZ-1, ZSM-3, faujasite, and mixtures of two or more thereof, more preferably selected from zeolite X, zeolite Y, ZSM-20, ZSM-3, faujasite, and mixtures of two or more thereof, more preferably a zeolite having a FAU-type framework structure selected from zeolite X, zeolite Y, faujasite, and mixtures of two or more thereof, wherein more preferably the one or more zeolites having a FAU-type framework structure comprise zeolite X and / or zeolite Y, preferably zeolite Y, wherein more preferably the one or more zeolites having a FAU-type framework structure are zeolite X and / or zeolite Y, preferably zeolite Y.

[0107] 10. The method according to any one of embodiments 1-9, wherein the zeolite material is in ammonium form or in H form, preferably in H form.

[0108] 11. The method according to any one of embodiments 1-10, wherein the zeolite material has an acid site concentration in the range of 0.100 - 4.000 mmol / g at a temperature in the range of 190 - 550 °C, preferably has an acid site concentration in the range of 0.200 - 2.000 mmol / g at a temperature in the range of 205 - 400 °C, more preferably has an acid site concentration in the range of 0.250 - 1.000 mmol / g at a temperature in the range of 250 - 290 °C, more preferably has an acid site concentration in the range of 0.300 - 0.800 mmol / g at a temperature in the range of 350 - 375 °C, more preferably has an acid site concentration in the range of 0.400 - 0.700 mmol / g at a temperature in the range of 360 - 366 °C, preferably determined according to Reference Example 2 by temperature-programmed desorption of ammonia (NH3-TPD).

[0109] 12. The method according to any one of embodiments 1-11, wherein the zeolite material has an acid site concentration in the range of 0.050 - 0.600 mmol / g at a temperature in the range of 175 - 210 °C, preferably has an acid site concentration in the range of 0.140 - 0.530 mmol / g at a temperature in the range of 185 - 200 °C, preferably determined according to Reference Example 2 by temperature-programmed desorption of ammonia (NH3-TPD).

[0110] 13. The method according to any one of embodiments 1-12, wherein the zeolite material has an acid site concentration in the range of 0.010 - 0.090 mmol / g at a temperature in the range of 475 - 625 °C, preferably an acid site concentration in the range of 0.030 - 0.060 mmol / g at a temperature in the range of 500 - 600 °C, preferably determined according to Reference Example 2 by temperature-programmed desorption of ammonia (NH3-TPD).

[0111] 14. The method according to any one of embodiments 1-13, wherein the zeolite material has a crystallinity in the range of 50 - 100 wt%, preferably 75 - 100 wt%, more preferably 80 - 100 wt%, even more preferably 90 - 100 wt%, wherein the crystallinity is preferably determined as described in Reference Example 3.

[0112] 15. The method according to any one of embodiments 1-14, wherein the zeolite material has a volume-based particle size distribution characterized by Dv50 in the range of 4.0 - 7.0 µm, preferably 4.5 - 6.5 µm, more preferably 5.0 - 6.0 µm.

[0113] 16. The method according to any one of embodiments 1-15, wherein YO2 calculated as element Y is contained in the zeolite material in the range of 35.0 - 47.0 wt%, preferably 38.5 - 43.5 wt%, more preferably 40.0 - 42.0 wt% based on the total weight of the zeolite material.

[0114] 17. The method according to any one of embodiments 1-16, wherein X2O3 calculated as X is contained in the zeolite material in the range of 1.0 - 4.5 wt%, preferably 2.2 - 3.7 wt%, more preferably 2.9 - 3.3 wt% based on the total weight of the zeolite material.

[0115] 18. The method according to any one of embodiments 1-17, wherein the zeolite material has a BET specific surface area equal to or greater than 380 m 2 / g, preferably equal to or greater than 650 m 2 / g, more preferably in the range of 700 - 800 m 2 / g, preferably determined as described in Reference Example 1.

[0116] 19. The method according to any one of embodiments 1-18, wherein the zeolite material has a Langmuir specific surface area equal to or greater than 500 m 2 / g, preferably equal to or greater than 800 m 2 / g, more preferably in the range of 810 - 1100 m 2 / g, preferably determined as described in Reference Example 1.

[0117] The method according to any one of embodiments 1-19, wherein X is Al and wherein the solid state of the zeolite material 27 Al NMR shows peaks in the range of 80-40 ppm and peaks in the range of 40-15 ppm, wherein the ratio of the peak integral of the peaks in the range of 80-40 ppm to the peak integral of the peaks in the range of 40-15 ppm is at least 3:1, preferably at least 7:1, more preferably at least 10:1, preferably determined as described in reference example 4.

[0118] The method according to any one of embodiments 1-20, wherein X is Al and wherein the solid state of the zeolite material 27 Al NMR shows peaks in the range of 80-40 ppm and peaks in the range of 15 ppm to -20 ppm, wherein the ratio of the peak integral of the peaks in the range of 80-40 ppm to the peak integral of the peaks in the range of 15 ppm to -20 ppm is at least 3:1, preferably at least 7:1, more preferably at least 10:1, preferably determined as described in reference example 4.

[0119] The method according to any one of embodiments 1-21, wherein the zeolite material has a micropore volume in the range of 0.180-0.390 ml / g, preferably 0.220-0.350 ml / g, more preferably 0.260-0.310 ml / g, preferably determined as described in reference example 1.

[0120] The method according to any one of embodiments 1-22, wherein the zeolite material has an average pore diameter in the range of 4.0-18.0 nm, preferably 5.5-8.0 nm, more preferably 6.6-7.3 nm, preferably determined as described in reference example 1.

[0121] The method according to any one of embodiments 1-23, wherein the zeolite material has an average pore width in the range of 1.5-5.5 nm, preferably 2.0-3.5 nm, more preferably 2.4-2.8 nm, preferably determined as described in reference example 1.

[0122] The method according to any one of embodiments 1-24, wherein the zeolite material provided in (i) is a calcined zeolite material, and wherein the zeolite material has been calcined at a temperature in the range of 300-900 °C, preferably 400-700 °C, more preferably 450-650 °C, more preferably 500-600 °C.

[0123] The method of embodiment 25, wherein the zeolite material has been calcined for a duration of 0.5-24 hours, preferably 1-15 hours, more preferably 2-12 hours, more preferably 2.5-9 hours, more preferably 3-7 hours, more preferably 3.5-6.5 hours, more preferably 4-6 hours.

[0124] The method according to any one of embodiments 1-26, wherein the catalyst is first contacted with acetone before contacting with the reaction mixture in (ii).

[0125] The method according to any one of embodiments 1-27, wherein the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a temperature in the range of 45-200 °C, preferably 50-150 °C, more preferably 55-120 °C, more preferably 60-100 °C, more preferably 65-90 °C, more preferably 70-80 °C.

[0126] The method according to any one of embodiments 1-28, wherein the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a pressure in the range of 1-200 bar (abs), preferably 20-150 bar (abs), more preferably 30-100 bar (abs), more preferably 45-80 bar (abs), more preferably 50-70 bar (abs), more preferably 55-65 bar (abs).

[0127] The method according to any one of embodiments 1-28, wherein the contacting of the catalyst with the reaction mixture prepared in (ii) in (iii) is carried out at a pressure in the range of 1-30 bar (abs), preferably 1-20 bar (abs), more preferably 1-15 bar (abs), more preferably 1-10 bar (abs), more preferably 1-5 bar (abs), more preferably 1-3 bar (abs).

[0128] The method according to any one of embodiments 1-30, wherein the method is carried out as a batch method or as a continuous method, and preferably the method is carried out as a continuous method.

[0129] The method according to any one of embodiments 1-31, wherein the method is carried out as a continuous method and wherein the contacting in (iii) is carried out at a liquid hourly space velocity (LHSV) in the range of 0.01-1000 ml / (g·h), preferably 0.05-500 ml / (g·h), more preferably 0.1-250 ml / (g·h), more preferably 0.3-100 ml / (g·h), more preferably 0.5-10 ml / (g·h), more preferably 1-5 ml / (g·h), more preferably 1.2-4 ml / (g·h), more preferably 1.5-3 ml / (g·h), more preferably 1.8-2.5 ml / (g·h), more preferably 2.0-2.2 ml / (g·h).

[0130] The method according to any one of embodiments 1-32, wherein the method further comprises:

[0131] (iv) Separating 2,2,6,6-tetramethyl-4-piperidone from the reaction product to obtain 2,2,6,6-tetramethyl-4-piperidone and a residual mixture;

[0132] (v) Recycling at least a portion of the residual mixture to the reaction mixture in (ii),

[0133] wherein a compound having a boiling point higher than that of 2,2,6,6-tetramethyl-4-piperidone is preferably separated from the residual mixture after (iv) and before (v).

[0134] 34. The method according to any one of embodiments 1-33, wherein in the reaction mixture prepared in (ii), the molar ratio of acetone to ammonia is in the range of 5:1 - 25:1, preferably 7:1 - 22:1, more preferably 10:1 - 19:1, more preferably 13:1 - 16:1, more preferably 14.0:1.0 - 14.7:1.0, more preferably 14.2:1.0 - 14.5:1.0.

[0135] 35. The method according to any one of embodiments 1-34, wherein the method is carried out as a batch process, wherein the contacting in (iii) is carried out for a duration in the range of 0.1 - 24 hours, preferably 0.5 - 20 hours, more preferably 1 - 15 hours, more preferably 3 - 10 hours, more preferably 4 - 8 hours, more preferably 5 - 7 hours.

[0136] 36. The method according to any one of embodiments 1-35, wherein the catalyst is provided as a molded article,

[0137] wherein the molded article is prepared according to a method comprising the following steps:

[0138] (a) Preparing a mixture comprising the zeolite material and optionally one or more binders;

[0139] (b) Shaping the mixture, preferably by extrusion, to obtain a shaped material;

[0140] (c) Optionally drying the shaped material in a gas atmosphere;

[0141] (d) Calcining the shaped material obtained from (b) or (c) in a gas atmosphere to obtain the molded article.

[0142] 37. The method of embodiment 36, wherein the mixture comprises one or more binders, and the one or more binders are one or more of alumina, silica, silica-alumina, graphite, polysaccharide, sugar alcohol, and synthetic polymer, preferably one or more of alumina, silica, silica-alumina, graphite, sugar alcohol, synthetic polymer, cellulose, modified cellulose, and starch, more preferably one or more of silica, alumina, silica-alumina, graphite, sugar alcohol, synthetic polymer, microcrystalline cellulose, and cellulose ether, still more preferably graphite, sorbitol, mannitol, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and sodium carboxymethyl cellulose.

[0143] 38. The method of embodiment 36 or 37, wherein in the mixture according to (a), the weight ratio of the one or more binders to the zeolite material is in the range of 1:10 - 1:30, preferably 1:15 - 1:25.

[0144] 39. The method of any one of embodiments 36 - 38, wherein the method comprises drying according to (c), and the drying is carried out in a gas atmosphere with a temperature in the range of 90 - 150 °C, preferably 110 - 130 °C, and preferably the drying is carried out for 10 - 15 hours, more preferably 11 - 13 hours.

[0145] 40. The method of any one of embodiments 36 - 39, wherein the gas atmosphere in (d) has a temperature in the range of 400 - 600 °C, preferably 450 - 550 °C, and preferably the calcination is carried out for 3 - 7 hours, preferably 4 - 6 hours.

[0146] 41. The method of any one of embodiments 36 - 40, wherein the gas atmosphere in one or more of (c) and (d) comprises one or more of nitrogen, oxygen, and argon, preferably nitrogen. Examples

[0147] Reference Example 1: Determination of BET specific surface area, Langmuir specific surface area, micropore volume, average pore width, and average pore diameter (N2)

[0148] The BET specific surface area, Langmuir specific surface area, micropore volume, average pore width, and average pore diameter (N2) were determined by physical adsorption of nitrogen at 77 K according to the method disclosed in DIN 66131. Reference Example 2: Determination of acid sites: Temperature-programmed desorption of ammonia (NH3-TPD)

[0149] Temperature-programmed desorption of ammonia (NH3-TPD) was carried out in an automated chemisorption analysis unit (Micromeritics AutoChem II 2920) equipped with a thermal conductivity detector. Continuous analysis of the desorbed species was accomplished using an on-line mass spectrometer (OmniStar QMG200 from Pfeiffer Vacuum). A sample (0.1 g) was introduced into a quartz tube and analyzed using the following procedure. The temperature was measured by a Ni / Cr / Ni thermocouple immediately above the sample in the quartz tube. He with a purity of 5.0 was used for the analysis. A blank sample was analyzed for calibration prior to any measurement.

[0150] 1. Preparation: Start recording; measure once per second. Wait for 10 minutes at 25 °C and a He flow rate of 30 cm 3 / min (room temperature (ca. 25 °C) and 1 atm); heat to 600 °C at a heating rate of 20 K / min; hold for 10 minutes. Cool to 100 °C (furnace slope temperature) at a cooling rate of 20 K / min under He flow (30 cm 3 / min); cool to 100 °C (sample slope temperature) at a cooling rate of 3 K / min under He flow (30 cm 3 / min).

[0151] 2. Saturation with NH3: Start recording; measure once per second. Change the gas flow to a 10% NH3 in He mixture (75 cm 3 / min; 100 °C and 1 atm) at 100 °C; hold for 30 minutes.

[0152] 3. Removal of excess: Start recording; measure once per second. Change the gas flow to a He flow of 75 cm 3 / min (100 °C and 1 atm) at 100 °C; hold for 60 minutes.

[0153] 4. NH3-TPD: Start recording; measure once per second. Heat to 600 °C at a heating rate of 10 K / min under He flow (flow rate: 30 cm 3 / min); hold for 30 minutes.

[0154] 5. End of measurement.

[0155] The desorbed ammonia was measured by the on-line mass spectrometer, which indicated that the signal from the thermal conductivity detector was caused by the desorbed ammonia. This involved using the m / z = 16 signal from ammonia to monitor the desorption of ammonia. The amount of adsorbed ammonia (mmol / g sample) was determined using Micromeritics software by integrating the TPD signal with respect to the horizontal baseline.

[0156] Reference Example 3: Determination of X-ray powder diffraction and crystallinity

[0157] Powder X-ray diffraction (PXRD) data were collected using a diffractometer (D8 Advance Series II, Bruker AXS GmbH) equipped with a LYNXEYE detector operating with a copper anode X-ray tube at 40 kV and 40 mA. The geometry was Bragg-Brentano and air scattering was reduced using an air scattering baffle.

[0158] Calculation of crystallinity: The crystallinity of the sample was determined using the software DIFFRAC.EVA provided by Bruker AXS GmbH, Karlsruhe. The method is described on page 121 of the user manual. Calculations were performed using the default parameters.

[0159] Calculation of phase composition: The phase composition was calculated from the raw data using the modeling software DIFFRAC.TOPAS provided by Bruker AXS GmbH, Karlsruhe. The diffraction pattern was simulated using the crystal structures of the identified phases, the instrument parameters, and the grain sizes of the individual phases. This is suitable for data except for the function simulating the background intensity.

[0160] Data collection: The sample was homogenized in a mortar and then pressed into a standard flat sample holder provided by Bruker AXS GmbH to collect data in Bragg-Brentano geometry. The flat surface was achieved by compressing and flattening the sample powder using a glass plate. Data were collected in the angular range 2 - 70° 2θ in steps of 0.02° 2θ while setting the variable divergence slit to an angle of 0.1°. The crystalline content describes the intensity of the crystalline signal relative to the total scattering intensity (user manual of DIFFRAC.EVA, Bruker AXS GmbH, Karlsruhe).

[0161] Reference Example 4: Solid state 27 Determination of Al NMR

[0162] 27 Al solid-state nuclear magnetic resonance (NMR) was performed using the following equipment, procedures, and parameters: The sample was stored at 62% relative humidity for at least 60 hours before loading; the sample was loaded into a 3.2 mm ZrO2 rotor with a Vespel cap, a Bruker Avance Neo spectrometer with a 14.1 Tesla magnet, 15 kHz (ω / 2π) magic angle spinning, single-pulse radiofrequency excitation corresponding to a 0.92 μs 15° pulse for an AlCl3 solution (1%, in H2O); 10 ms acquisition of the free induction decay, without heteronuclei 1H nuclear magnetic resonance decoupling, averaging scans with a delay of 0.5 s for at least 5120 cycles, Fourier transform with an exponential line broadening of 10 Hz to suppress noise, and manual phasing and baseline correction in Bruker Topspin 3.0. On the absolute chemical shift scale at a frequency ratio of 0.26056859, according to Pure Appl. Chem., Vol. 80, No. 1, pp. 59 - 84, 2008, adamantane with a 13 C methylene resonance at 37.77 ppm was used as a secondary standard relative to 1.1 mol / kg of Al(NO3)3 in D2O for spectral calibration.

[0163] Reference Example 5: Characteristics of the Tested Zeolite Materials

[0164] Table 1

[0165] Part I of the Characteristics of the Tested Zeolite Materials

[0166]

[0167]

[0168] Table 2

[0169] Part II of the Characteristics of the Tested Zeolite Materials

[0170]

[0171] Example 1: Catalytic Test - Batch Mode

[0172] Catalysts 1 and 4 and Comparative Catalysts 1 and 3 were tested as catalysts for the production of 2,2,6,6 - tetramethyl - 4 - piperidone in batch mode. For each test, the catalyst usage was 40 g (4 g / g). The temperature was set at 65 °C. Each test was carried out for 6 hours, with ammonia fed within 1 hour before starting heating. The reaction products were analyzed by gas chromatography to determine the contents of 2,2,6,6 - tetramethyl - 4 - piperidone, 2,2,4,6 - tetramethyl - 2,3 - dihydropyridine, 1,2,5,6 - tetrahydro - 2,2,4,6,6 - pentamethylpyrimidine, and acetone. Therefore, the results are given as area % according to the gas chromatography measurements.

[0173] As can be seen from the results shown in Table 3, Catalysts 1 and 4 containing zeolite materials with SAR values of 25 and 20, respectively, showed higher conversion to 2,2,6,6 - tetramethyl - 4 - piperidone than Comparative Catalyst 3 containing a zeolite material with an SAR of 5.2. Specifically, the relative amount of 2,2,6,6 - tetramethyl - 4 - piperidone for Catalysts 1 and 4 was higher than that of Comparative Catalyst 3 throughout the 6 - hour test period.

[0174] Furthermore, as can be seen from Table 3, the relative amounts of the undesired by-product 2,2,4,6-tetramethyl-2,3-dihydropyridine determined by gas chromatography are at relatively low levels for both Catalysts 1 and 4 and Comparative Catalyst 3. In summary, as can be seen from Table 3, Catalysts 1 and 4 are more active catalysts especially with respect to the conversion to 2,2,6,6-tetramethyl-4-piperidone.

[0175] As can be seen from the results shown in Table 3, Catalysts 1 and 4 showed excellent catalytic performance compared to all Comparative Catalysts 1 and 3 - 6. Specifically, the relative amounts of 2,2,6,6-tetramethyl-4-piperidone are significantly higher for Catalysts 1 and 4, where the relative amounts of the undesired by-product 2,2,4,6-tetramethyl-2,3-dihydropyridine are significantly lower than those of Comparative Catalyst 4 and comparable to those of Comparative Catalyst 1. Further, as can be seen from Table 3, the relative amounts of 1,2,5,6-tetrahydro-2,2,4,6,6-pentamethylpyrimidine are significantly lower for Catalysts 1 and 4, and the total conversion of acetone is also higher for Catalysts 1 and 4 than for all Comparative Catalysts 1 and 3 - 6.

[0176] In addition, as can be seen from Table 3, the ratio of 2,2,6,6-tetramethyl-4-piperidone:2,2,4,6-tetramethyl-2,3-dihydropyridine is significantly higher for Catalysts 1 and 4 than for Comparative Catalysts 1 and 3 - 6.

[0177] In addition, as can be seen from Table 3, Comparative Catalyst 6 containing a zeolite material having an MFI framework structure and a silica / alumina molar ratio (SAR) of 30 showed overall poorer performance compared to Catalysts 1 and 4.

[0178] Table 3

[0179] Catalytic test results of different zeolites in batch mode, where the conversions to the corresponding compounds are given as area % determined by GC

[0180]

[0181] The specific characteristics of the tested zeolite materials are listed in Tables 1 and 2 above.

[0182] Example 2: Catalytic test - continuous mode

[0183] Catalysts 2 and Comparative Catalyst 2 were tested as catalysts for the production of 2,2,6,6-tetramethyl-4-piperidone in continuous mode. A reactor with a length of 1 m and a diameter of 8 mm was used. The temperature of the reactor wall was set at 70 °C, the liquid hourly space velocity was set at 1.71 ml / g h and the pressure was set at approximately 55 bar (single phase). The feed stream contained acetone and ammonia in a molar ratio of 14.3:1.0. Each test was run for 6 hours. The average residence time was found to be approximately 60 - 74 minutes.

[0184] For the catalyst test in continuous mode, the corresponding catalyst is used as a shaped body. For this purpose, 1250 g of the corresponding zeolite material, 1180 ml of deionized water and 62.5 g of Walocel TM (Walocel MW15000GB, Wolff Cellulosics GmbH&Co.KG, Germany) are provided in a kneader and kneaded for 10 minutes. For shaping, the kneaded material is extruded at a pressure of 190 bar (abs) to obtain a wire having a circular cross-section with a diameter of 1.5 mm. Then the wire is dried at 120 °C for 12 hours and calcined at 500 °C for 5 hours. The reaction product is analyzed by gas chromatography to determine its 2,2,6,6-tetramethyl-4-piperidone, 2,2,4,6-tetramethyl-2,3-dihydropyridine, 1,2,5,6-tetrahydro-2,2,4,6,6-pentamethylpyrimidine and acetone contents. Accordingly, the results of the gas chromatography measurements are given as area%.

[0185] As can be seen from the results shown in Table 4, compared to Comparative Catalyst 2, Catalyst 2 also shows a higher conversion to 2,2,6,6-tetramethyl-4-piperidone in the continuous mode. As can be seen from Table 4, the ratio of 2,2,6,6-tetramethyl-4-piperidone:2,2,4,6-tetramethyl-2,3-dihydropyridine is higher for Catalyst 2 than for Comparative Catalyst 2. This finding is even more surprising since the prior art Cavani et al. discussed above suggest using in particular H-Y zeolites with a lower SAR of 6, which shows the best results for the preparation of the required 2,2,6,6-tetramethyl-4-piperidone while producing the smallest amount of the unwanted by-product 2,2,4,6-tetramethyl-2,3-dihydropyridine. In contrast, the H-Y zeolite with an SAR of 15 tested by Cavani et al., Journal of Molecular Catalysis A: Chemical 393 (2014), 325 - 332 shows poorer performance both for the preparation of 2,2,6,6-tetramethyl-4-piperidone and for the said by-product. Similarly, J. Tian et al. discussed above, Journal of Heterocyclic Chemistry 2015, Vol. 52, pp. 1377 - 1381 found that the H-Y zeolite with a silica / alumina molar ratio of 11.2 is the most effective for the preparation of 2,2,6,6-tetramethyl-4-piperidone. Apparently, J. Tian believes that zeolites with a lower SAR are the most promising for further testing, especially for acetone, for optimizing the reaction conditions used. In contrast and especially considering a process mode according to the invention that allows only a limited water content, the method according to the invention comprising a zeolite material of the FAU framework structure type surprisingly also shows a technical effect for zeolite materials with a relatively high silica / alumina ratio.

[0186] The characteristic features of the zeolite materials tested are listed in Tables 1 and 2 above.

[0187] Table 4

[0188] Results of catalytic tests of different zeolites in the continuous mode, where the conversion to the corresponding compounds is given as area % determined by GC

[0189] Brief description of the drawings

[0191] Figure 1 Illustrating the solid state of the zeolite material according to Example 1 (top) relative to the zeolite material of Comparative Example 1 (bottom) 27 Al NMR spectra, where the chemical shift (ppm) is plotted along the abscissa and the relative intensity in arbitrary units is shown along the ordinate.

[0192] Cited literature

[0193] - F. Cavani et al., Journal of Molecular Catalysis A: Chemical 393 (2014), 325 - 332

[0194] - CN 107033066 A

[0195] - J. Tian et al., Journal of Heterocyclic Chemistry 2015, Vol. 52, pp. 1377 - 1381.

Claims

1. A method for producing 2,2,6,6 - tetramethyl - 4 - piperidone, comprising: (i) providing a reactor containing a catalyst comprising a zeolite material having a framework structure FAU, wherein the zeolite material contains YO2 and X2O3 in its framework structure, where Y is Si and X is Al, and wherein the zeolite material has a YO2 / X2O3 molar ratio of 16 - 40; (ii) preparing a reaction mixture comprising acetone and ammonia; (iii) contacting the catalyst in the reactor with the reaction mixture prepared in (ii) at a temperature in the range of 40 - 250 °C to obtain a reaction product comprising 2,2,6,6 - tetramethyl - 4 - piperidone; wherein the mixture prepared in (ii) and contacted with the catalyst in (iii) contains less than 10% by weight of water based on 100% by weight of the reaction mixture.

2. The method of claim 1, wherein 5% by weight or more of the catalyst is composed of the zeolite material.

3. The method of claim 1, wherein the catalyst is provided as a powder and / or a molded article.

4. The method of claim 2, wherein the catalyst is provided as a powder and / or a molded article.

5. The method of claim 1, wherein the zeolite material is in ammonium form or in H form.

6. The method of claim 2, wherein the zeolite material is in ammonium form or in H form.

7. The method of claim 3, wherein the zeolite material is in ammonium form or in H form.

8. The method of claim 4, wherein the zeolite material is in ammonium form or in H form.

9. The method of any one of claims 1 - 8, wherein the zeolite material has a crystallinity in the range of 50 - 100% by weight, wherein the crystallinity is determined using the software DIFFRAC.EVA provided by Bruker AXS GmbH, Karlsruhe, and calculated using the default parameters.

10. The method of any one of claims 1 - 8, wherein YO2 calculated as element Y is contained in the zeolite material in the range of 35.0 - 47.0% by weight based on the total weight of the zeolite material.

11. The method of claim 9, wherein YO2 calculated as element Y is contained in the zeolite material in the range of 35.0 - 47.0% by weight based on the total weight of the zeolite material.

12. The method of any one of claims 1 - 8, wherein X2O3 calculated as X is contained in the zeolite material in the range of 1.0 - 4.5% by weight based on the total weight of the zeolite material.

13. The method of claim 11, wherein X2O3 calculated as X is contained in the zeolite material in the range of 1.0 - 4.5% by weight based on the total weight of the zeolite material.

14. The method of any one of claims 1 - 8, wherein in (iii), the contacting of the catalyst with the reaction mixture prepared in (ii) is carried out at a temperature in the range of 45 - 200 °C.

15. The method of claim 13, wherein in (iii), the contacting of the catalyst with the reaction mixture prepared in (ii) is carried out at a temperature in the range of 45 - 200 °C.

16. The method according to any one of claims 1 - 8, wherein the method is carried out as a batch method or a continuous method.

17. The method according to claim 15, wherein the method is carried out as a batch method or a continuous method.

18. The method according to any one of claims 1 - 8, wherein the molar ratio of acetone to ammonia in the reaction mixture prepared in (ii) is in the range of 5:1 - 25:

1.

19. The method according to claim 17, wherein the molar ratio of acetone to ammonia in the reaction mixture prepared in (ii) is in the range of 5:1 - 25:

1.

20. The method according to any one of claims 1 - 8, wherein the catalyst is provided as a molded article, and the molded article is prepared according to a method comprising the following steps: (a) preparing a mixture comprising the zeolite material and optionally one or more binders; (b) shaping the mixture; (c) optionally drying the shaped material in a gas atmosphere; and (d) calcining the shaped material obtained from (b) or (c) in a gas atmosphere to obtain the molded article.

21. The method according to claim 19, wherein the catalyst is provided as a molded article, and the molded article is prepared according to a method comprising the following steps: (a) preparing a mixture comprising the zeolite material and optionally one or more binders; (b) shaping the mixture; (c) optionally drying the shaped material in a gas atmosphere; and (d) calcining the shaped material obtained from (b) or (c) in a gas atmosphere to obtain the molded article.

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