The method of obtaining 3-methylpiperidine and 3-methylpyridine

 

(57) Abstract:

The invention relates to a method for producing 3-methylpiperidine by cyclization of 2-methyl-1,5-diaminopentane in the gas phase at 300 to 400oC and the pressure 0-10 bar above atmospheric in the presence of a catalyst, such as activated aluminum oxide, mixed aluminum oxide and silicon or natural or synthetic zeolite, which have a ratio of acidic to basic centers on the surface of the above 2 and a specific surface area of above 40 m2/was a Way to keep the catalyst activity for a long period of time and to obtain the target product with high yield. The invention relates also to a method for producing 3-methylpyridine by further conversion of 3-methylpiperidine in the presence of a dehydrogenation catalyst. 2 c. and 4 C.p. f-crystals, 5 PL.

The invention relates to a method for producing 3-methylpiperidine (MPI), respectively, 3-methylpyridine (PIC) of 2-methyl-1,5-diaminopentane (MPDA).

3-Methyl-piperidine is used as a vulcanization accelerator and as an additive to lubricating oil. 3-Methylpyridin is used as a solvent and as an intermediate product upon receipt Niko is ridin based on 2-methyl-1,5-diaminopentane by passing a gaseous source of a product through the catalyst metal oxides at a temperature of 500-600oC. Preferred catalysts are copper chromite, molybdenum oxide or vanadium oxide. These catalysts are preferably applied to the carrier. Depending on the reaction temperature proportion of piperidine to the pyridine may shift in one direction or another. In this description, the patent also mentions the possibility to use as catalysts acidic oxides as SiO2or Si/Al - oxides without other additives. Thus, the achieved output, however, is only mediocre. About the catalyst activity over a longer lifetime, no data was provided.

From U.S. patent 3903079 known method of cycloalkanones disubstituted alkanes, which contain primary amino groups and/or hydroxyl groups. As the catalyst used molecular sieve based on the metal-silicate. As metals are preferably chosen copper, palladium, manganese, Nickel or chrome. The reaction is carried out in the presence of ammonia. Achieved moderate output. Upon receipt of the piperidine derivatives of 1,5-pentanediol reach a yield of 75%.

The present invention is to develop a method of obtaining 3-methylpiperidine of the 2 outputs. The activity of the catalyst should be maintained for a long time. Another task is to develop a method for the preparation of 3-methylpyridine by further conversion of 3-methylpiperidine in the presence of a dehydrogenation catalyst.

According to the invention the task is solved through the method under item 1 of the claims.

Under the said paragraph 1 of the claims oxides A1 and/or Si is understood as individual oxides, as Al2O3mixed oxides of Al2O3/SiO2and their crystallized compounds as aluminum silicates, in particular zeolites.

It is important that they have a predominantly acidic in nature and have a specific surface area of more than 40 m2/,

The acidic nature follows from the ratio of acidic and basic centers on the surface, which according to the invention must be more than 2. Analytically, the acidic centers are determined by irreversible adsorption of NH3when 80oC, and the main centers of irreversible adsorption of CO2when 80oC. as catalysts for the proposed according to the invention, a method is preferably used activated Al2O3mixed oxides of Al2Basilicata, which have a highly ordered structure with a rigid three-dimensional lattice of tetrahedra SiO4and AlO4that are linked by common oxygen atoms. The ratio of silicon atoms and aluminium atoms to oxygen is 1:2. Electrovalent containing aluminum tetrahedra is compensated for by the inclusion in the crystal of cations, for example, ions of alkali metals or hydrogen. You can exchange cations. The spaces between the tetrahedra, before dehydration by drying, respectively, calcination, are occupied by water molecules.

If the zeolite on the basis of the sort of receipt is not in the catalytically active, acidic H form but, for example, in the Na form, by ion exchange, for example with ammonium ions, and subsequent calcination, or by treatment with acids it can be completely or partly converted into the desired H form.

The catalysts preferably used in the form of a fixed catalyst layer and the source material, it is advisable when using hydrogen or inert gas, as nitrogen as a carrier gas, is passed through the catalyst.

The reaction temperature is set in the range of 300-400oC, preferably 305-375oC. the Pressure of the composition is RA represents the volumetric rate of weight per hour" (MHSV). In this case, MHSV preferably is maintained equal to 2.1 to 4.2 g of educt in g of catalyst and per hour. Vapor source product can be diluted, preferably with N2or H2.

3 Methylpiperidin by a known method dehydrogenation can be converted to 3-picoline. When formed by the method of the invention, flow 3-methylpiperidine can directly pass through the catalyst dehydrogenation, so that the dehydrogenation occurs immediately after the cyclization. This is possible due to the fact that 3-methylpiperidin is formed with an unusually high purity and, in particular, contains practically no more no MPDA. Especially was found that the activity of the dehydrogenation catalysts is strongly influenced by MPDA.

As dehydrogenation catalysts preferably used noble metals, such as palladium or platinum, on the media. Especially preferred were the catalysts for dehydrogenation, which is obtained from the amorphous oxides of aluminum and silicon by ion exchange with a soluble palladium complexes, [Pd (NH3)4]Cl2. Amorphous oxides of silicon and aluminum is preferably first dewatered and load Ashida in the solution of the complex. Alternatively, the solution of the complex you can also pass through the gasket amorphous oxide, moreover, however, in contrast to the originally specified method, it is possible to achieve uniform loading by the full exchange.

According to these methods are also using relatively dilute solutions, for example, 0.01 mol/l [Pd(NH3)4]CI2you can reach the contents of palladium up to 5 wt.% and above in a single phase.

The reaction temperature in the dehydrogenation is 220-400oC. According to one variant of implementation, the cyclization catalyst is applied directly on the layer of catalyst in the dehydrogenation of 2-methyl-1,5-diaminopentane is skipped from the top. According to a preferred variant implementation, the catalysts contribute in separate reactors. This allows independent temperature control and, if necessary, independent regeneration of the catalyst.

The following examples illustrate how the implementation of the proposed in the invention method. All the examples of pressure do not represent any absolute pressure, and elevated pressure are correlated to atmospheric pressure.

Examples 1-11. Specified in digislide the m

In the reactor (13 mm) placed 3 g of catalyst (grain size: 0,32-1 mm). MPDA evaporated and current media 15 ml/min of N2at a pressure of 5 bar is passed through the catalyst. The layer of catalyst is gradually heated and the reaction is monitored by gas chromatography. The more active the catalyst, the lower the temperature required for cyclization MPDA to MPI. The activity of the used catalyst can be compared with each other by the temperatures required to obtain high output MPI, and when taking into account the load of the catalyst (MHSV).

Examples 1, 2 and 3 are comparative examples not according to the invention).

The table is complemented by the characteristics of the used catalysts.

Cu-Chromite: Cu - 1230 R (Engelhard, 29% Cu , 32% Cr, 6% Ba)

Al-E: 97% Al2O3- 3% SiO2(Engelhard)

Al-3996E: Al2O3(Engelhard)

K-Y Zeolite Y, K+- exchanged

H-Y Zeolite Y (Degussa)

Si-235-I T: 87% SiO2- 13% AL2ABOUT3(Engelhard)

H-ZSM-5: 54,5% Pentasil (Si/Al = 18) + 45,5% binder

Example 12. The transformation of MPDA in 3-picoline

The reactor (13 mm) is filled with 4 g of a catalyst based on palladium (1% Pd /Al2O3and over it place 3 g of N-ZSMUB>2, pressure = 5 bar. In the temperature interval 305-320oC and when MHSV = 0.6 g/ (GCAS) achieve outputs of up to 97% 3-picoline, and as the only other product found MPI in the amount of 2.9%. Therefore, there is a complete transformation of MPDA in the target product. Within 10 days do not see any deactivation of the catalysts. Instead of N2you can also use the H2as the carrier gas. Therefore, the new method leads to a significant improvement in activity, selectivity and lifetime of the catalyst.

Example 13. Obtaining 3-picoline using two separate reactors and sales MPDA (conversion of MPDA in 3-picoline 2-stage emitting MPI).

stage 1: In the reactor (13 mm) placed 3 g of ZSM - 5 in the ammonium form (grain size: 0.5-1 mm). MPDA evaporated and using current carrier gas 15 ml/min of N2at a pressure of 5 bar and at a temperature of 335oC is passed through the catalyst. MHSV is 4.2 g of MPDA per gram of catalyst and per hour. Used MPDA is a sales product that is produced by the company Du Pont de Nemours under the trade name "Dytek A". The experience lasts for 280 hours. Deactivation of the catalyst is not observed. The product is condensed and about In the reactor (13 mm) was placed 10 g of the catalyst dehydrogenation Pd-MgCl2/Al2O3. MPI from previous experience in the vapor state with the current carrier gas 15 ml/min. N2at a pressure of 1 bar and at a temperature of 280oC, is passed through the catalyst. HSV is 0.23 g MPI per gram of catalyst and per hour. The experience takes place in a period of 190 hours of Deactivation of the catalyst is not observed. After 190 h by gas chromatography to find the following product composition: 99.3% of 3-picoline, 0.4% of MPI.

Example 14. Obtaining 3-picoline using two separate reactors and sales MPDA (conversion of MPDA in 3-picoline in stage 2 without allocating MPI). The reactor (13 mm) fill 3 g NH4-ZSM-5 (grain size: 0.5-1 mm). MPDA evaporated and together with the current carrier gas 15 ml/min. N2at a pressure of approximately 1 bar and at a temperature of 320oC, flows through the catalyst. MHSV is 1-2 g of MPDA per gram of ZSM-5 in an hour. Used MPDA is a commercial product manufactured by Du Pont de Nemours under the trade name "Dytek A". Product from the reactor cyclization support in the gas phase and directly passed through the second reactor. This reactor contains 12 g of dehydrogenation catalyst composition Pd + MgCl2on the media of Al2ABOUT3(grain size: 0,32-1 mm). Conditions Rea which contains 99,1% 3-picoline and 0.9% MPI (determined by gas chromatography). Decontamination of both catalysts during reaction time is not observed.

Example 15 (comparative example). Preparation of catalyst 1% Pd/Al2O3by impregnation. To 540 g of deionized water is added 6.3 g of Pd(NO3)2H2O (Heraeus) and 15.3 g of concentrated HCl. Set pH of 0.7. This solution is added to 250 g of Al2O3(Al - 4191 E 1/16" company Engelhard), which is first moistened with deionized water. The time of impregnation (impregnation) is 3 days. Then the solution is removed by decantation and the catalyst is dried for 20 h at 150oC. After this, it is calcined for 20 hours at 550oC in a drying oven with air circulation. The catalyst granularit and collect the screen mesh fraction 0,315-1 mm

Example 16 (comparative example). Preparation of catalyst 3% Pd/Al2O3by impregnation. Al2O3(Al - 3996 R, firm Engelhard) granularit and use the screen mesh fraction 0,315-1 mm is Prepared 3 solution for impregnation of 150 r deionized water, 1.8 g of Pd(NO3)O2H2(Heraus) and of 2.36 g of concentrated HCl. Set the pH-value of about 0.8. 70 g media consistently for 24 h, impregnorium with these three R ml deionized water, dried at 150oC in a vacuum drying oven and within 2 hours and calcined at 550oC in a drying oven with air circulation.

Example 17 (comparative example). The preparation of the catalyst 4% Pd/Al2O3by impregnation. Prepare two solutions for the impregnation of 150 g of deionized water, 1.25 g of Pd(NO3)3H2(Heraus) and 2.24 g of concentrated HCl. Set the pH-value of 0.8. 50 g of catalyst from example 2 are sequentially impregnorium using these solutions for impregnation, and after each stage, the catalyst is washed with 100 ml of deionized water, dried for 2 h at 150oC in a vacuum drying oven and within 2 hours and calcined at 550oC in a drying oven with air circulation.

Example 18. Preparation of catalyst 3% Pd-SiO2/Al2O3by ion exchange with [Pd(NH3)4]2+. The media of the oxides of Si and Al (13 wt.% Al2O3Si-235-1 T company Engelhard granularit (0,315-1 mm). 50 g of granulated dehydrated in a quartz tube at 400oC current N2within 12 hours Through a cooled sample for 1 hour let dry gaseous ammonia (36 g). Prepare a 0.01 M solution of [Pd(NH3)4] cooling is desired by both molarity is adjusted by adding water. 20 g of pre-treated medium is stirred for 24 h with 2542 ml of 0.01 M solution of palladium salt. Then the catalyst was washed 6 times with 500 ml of deionized water each time and dried for 24 h at 120oC. the Catalyst contains about 5 wt.% palladium.

Example 19. The preparation of the catalyst 5% Pd - SiO2/Al2O3by ion exchange with [Pd(NH3)4]2+. 150 g of the carrier of SiO2/Al2O3(15 wt.% Al2O3Si-HP-87-069 T company Engelhard dehydrated in a quartz tube at 400oC current N2within 12 hours Through the chilled sample is passed within 1 h of dry gaseous ammonia (60 g).

70 g of pre-treated medium is stirred for 20 hours 3720 ml of 0.01 M solution of palladium salt (prepared according to example 18). Then the catalyst was washed 6 times with 1000 ml with deionized water and dried for 15 h at 120oC. the Catalyst contains about 5 wt.% palladium.

Example 20. Preparation of catalyst 3% Pd - SiO2/Al2O3by ion exchange with [Pd(NH3)4]2+. 120 g of the carrier of SiO2/Al2O3(15 wt/% Al2O3Si-HP-87-069 T company Engelhard dehydrate the 1 h dry gaseous ammonia (35 g).

35 g of pre-treated media for 24 h mixed with 1030 ml of 0.01 M solution of palladium salt (prepared according to example 18). Then the catalyst was washed 6 times with 1000 ml with deionized water and dried for 24 h at 120oC. the Catalyst contains about 3 wt.% palladium.

Example 21. Preparation of catalyst 1% Pd - SiO2/Al2O3by ion exchange with [Pd(NH3)4]2+. of 76.5 g of the carrier of SiO2/Al2O3(15 wt.% Al2O3Si-HP-87-069 T company Engelhard dehydrated in a quartz tube at 400oC in a stream of nitrogen. Through a cooled sample is passed within 1 h of dry gaseous ammonia (69 g).

Prepare 0,0033 M solution of [Pd(NH3)4]Cl2: to 100 ml of 0.84 M aqueous solution of ammonia add 0.375 g PdCl2and stirred for 15 minutes at 85oC. After cooling, establish desirable both molarity by adding water. 35 g of pre-treated media for 24 h mixed with 1030 ml 0,0033 M solution of palladium salt. Thereafter, the catalyst was washed 6 times with 1000 ml with deionized water and dried for 24 h at 120oC. the Catalyst contains about 1 wt.% palladium.

Example 22. Th the O2/Al2O3(15 wt.% Al2O3Si-HP-87-069 T company Engelhard dehydrated in a quartz tube at 400oC at the point N2within 12 hours Through a cooled sample for 1 h let dry gaseous ammonia (60 g).

Analogously to example 18, cook of 0.015 M solution of PdCl2. 35 g of pre-treated media for 24 h and stirred with 1000 ml of 0.015 M solution of PdCl2. Then the catalyst was washed 2 times with 500 ml of deionized water and dried for 24 h at 120oC. the Catalyst contains about 1.4 wt.% palladium, a chlorine content below 0.01%.

Example 23. The preparation of the catalyst 6% Pd - SiO2/Al2O3by ion exchange with [Pd(NH3)4]2+in a glass column. 900 g of the carrier of SiO2/Al2O3(15 wt.% Al2O3Si-HP-87-069 T company Engelhard dehydrated in a quartz tube at 400oC at the point of nitrogen for 12 hours Through the chilled sample is passed over a 1.25 hour dry gaseous ammonia (155 g).

Prepare 67,6 l 0.01 M solution of [Pd(NH3)4]Cl2: 31,7 l 0.84 M aqueous solution of ammonia is added 119 g of PdCl2and stirred at 85oC up until the solution is clear. After ohlasy media contribute in a glass column (length 115 cm, diameter 6.5 cm) and within 15 h through the media on the principle of circulation pump Pd - solution by means of a pump with a compressible sleeve (60 l/h). Then the catalyst was washed 6 times in 9 liters of deionized water in a vessel with stirrer and dried for 24 h at 120oC in a drying oven with air circulation. Yellow catalyst (982 g) contains about 6 wt. % palladium.

Example 24. The preparation of the catalyst 6% Pd-SiO2/Al2O3by ion exchange obtained by the Sol-gel method: SiO2/Al2O3with [Pd(NH3)4]2+: Powder SiO2/Al2O3(13 wt. % Al2O3) MS 13/110 firms Grace pressed into tablets (diameter 9 mm). Tablets are crushed and collect the screen mesh fraction 0,315-1 mm 95 g of granulated dehydrated in a quartz tube at 400oC in a stream of nitrogen (250 ml/min) for 12 hours Through the chilled sample is passed within 1 h of dry gaseous ammonia (58 g).

80 g of pre-treated medium is stirred for 24 h with 10.1 l 0.01 M solution of palladium salt (prepared according to example 18). Then the catalyst was washed 6 times with 1000 ml of deionized water and dried for 24 h at 120oC. the Catalyst contains about 6 wt.% palladium.

2O3) with grain size 0,315 - 1 mm contains 30% of alumina as a binder. 60 g of the dehydrated product in a quartz tube at 400oC in a stream of nitrogen for 12 hours Through a cooled sample for 1 h let dry gaseous ammonia (35 g).

20 g of pretreated pentasil injected into an exchange reaction with 420 ml of 0.01 M solution of palladium salt (obtained according to example 18). Then, the zeolite is washed 6 times with 250 ml of deionized water and dried for 24 h at 120oC. the Catalyst contains about 2 wt.% palladium.

Examples 26-33 (PL. 2). The dehydrogenation of 3-methylpiperidine (MPI) to 3-picoline (PIC). In the reactor (13 mm) contribute 3-10 g of catalyst (grain size: 0,315-1 mm). MPI is evaporated and is specified in the table. 2 the temperature of the reactor is passed through a catalyst (p ~1 bar). In most cases, additionally introducing a stream of hydrogen at 15 ml/min. Current product analyzed by gas chromatography. Listed in the table. 2 data analysis receive after fixed reaction conditions (> 20 h).

From table. 2 it is apparent that obtained according to the earlier patent (laid out description of the invention to unaccepted application Aida aluminum using Pd catalysts (examples 27 and 28) less than 3-picoline and more neprevyshenie MPI in the current product, than the catalysts of examples 15-17 and 19. Is there more unexpectedly, that the experiments with the impregnated catalysts were carried out under the light load of the catalyst. The catalysts of examples 29-31 and 33 are obtained by ion exchange SiO2/Al2O3with [Pd(NH3)4] Cl2. Activity to a certain extent can be controlled by the degree of exchange (see examples 29-31, 5%, 3% and 1% palladium subjected to the exchange of the catalyst). In example 22 using a catalyst, in which the media treated not with [Pd(NH3)4/Cl2and using PdCl2. This catalyst shows much lower activity than the catalysts treated with [Pd(NH34/Cl2.

Example 34-40. In the reactor (13 mm) placed 3-10 g of catalyst (grain size 0,315-1 mm). As educt used raw materials ("MPI"), which is prepared from a mixture of the following composition: 74,9% MPI, 13.9% of 2-methyl-1,5-diaminopentane (MPDA), 5.1% of organic impurities (mainly methylcyclopentadiene) and 6.1% of water. Preparation of raw materials is carried out by catalytic cyclization is contained in the original mixture MPDA according to examples 15-25. After cyclization MPI Roh" has the following composition: 89,9% MPI, 4.0 percent organic impurities and 6.1% of water. Idolize catalysts (p ~1 bar). In most cases, additionally set the hydrogen flow at 15 ml/min. Current product analyzed by gas chromatography.

From table. 3 clearly follows that obtained according to the earlier patent (laid out description of the invention to unaccepted application for patent in Germany 3410542), impregnated Pd-Mg catalyst (example 34) when MHSV = 1,76 gives less 3-picoline and more neprevyshenie MPI in the current product, than the catalysts of examples 35 to 40. The catalysts of examples 35 to 40 is obtained by means of ion exchange SiO2/Al2O3with [Pd(NH3)4]Cl2. These catalysts have a significantly higher activity and even when MHSV = 3,52 can be achieved even MPI - transformations above 99.5 per cent.

The catalyst of example 40 is obtained by means of ion exchange SiO2/Al2O3prepared by the Sol-gel method.

In example 35 add ammonia. Experience shows that emitted from cyclization MPDA to MPI ammonia does not interfere with the reaction. The reaction also occurs when not impose any hydrogen as the carrier gas (example 36).

Example 41. Subjected to Pd-ion exchange zeolite as a catalyst. In the reactor (13 mm) was placed 10 g of Pd - ZSM-5 catalyst catalyst (P ~1 bar). Current product analyzed by gas chromatography (GC - FI.- %). After a reaction time of 21 hours current product contains 99.2% of PIC and 0.8% neprevyshenie MPI. After a reaction time 213 h the current product contains 93,15% PIC and 6,85% neprevyshenie MPI.

Example 42. In this experiment strive insulated conducting the reaction. For this purpose, the reactor (diameter 21 mm) enter 27 g of the catalyst of example 19. (grain size 0,315-1 mm). The catalyst is diluted with 53 g of the carrier of the catalyst so that the catalyst is most strongly diluted by the entrance to the reactor on the output side it undiluted and fall of the concentration along the catalyst layer should be approximately exponential. The educt has the following composition: 92.7% of MPI, 6,5% water, 0.8% of organic impurities. Educt evaporated and HSV = 4,73, based on active catalyst (1 g, respectively, of the educt per ml catalyst per hour) is passed through the catalyst bed (p = 0.11 bar). Current product analyzed by gas chromatography (GC - FI. - %). The transformation of quantitative and later 339 h organic portion of the product still contains 99.3% of the PIC and 0.7% of organic impurities. On the basis of endothermy reactions in the center of the reactor set temperature of approximately 240oC (the temperature of the walls is Chora. After a reaction time 362 h as educt use pure, anhydrous MPI. Later 454 h the current product contains 99,2% PIC of 0.4% neprevyshenie MPI and 0.4% of organic impurities.

Example 43. Continuous transformation of a 2 stage 2-methyl-1,5-diamino-pentane (MPDA) in 3-picoline. In a reactor with a diameter of 13 mm), placed 3 g of granulate SiO2/Al2O3(Si-HP-87-069 T company Engelhard) with grain size 0,315-1 mm MPDA evaporated and using current carrier gas 15 ml/min H2at a pressure of approximately 1 bar and the temperature of the reactor 320oC, is passed through the catalyst and cyclist to MPI. Used MPDA is a sales product that is produced by the company Du Pont de Nemurs under the trade name "Dytek A". The product from the cyclization reactor is maintained in the gas phase and directly passed through the second reactor. This reactor contains 3 g of the dehydrogenation catalyst of example 18 (grain size of 0.32-1 mm). The reactor temperature is 280oC, pressure = 1 bar. In the process of experience educt MPDA turns into MPI and then in raw materials (3-Mr Roh), which consists of a mixture of the following composition: 74,9% MPI, 13.9% of MPDA, 5.1% of organic impurities (mainly methylcyclopentadiene) and 6.1% of water. The results with the corresponding values MHSV (MHSV per reactor) picolin. In the reactor (13 mm) placed 3 g of granulate SiO2/Al2O3(Si-HP-87-069 T company Engelhard) with grain size 0,315-1 mm MPDA is evaporated and the current carrier gas 15 ml/min. H2at a pressure of approximately 1 bar and the temperature of the reactor 320oC is passed through the catalyst and cyclist to MPI. Used MPDA is a commercial product, which is produced by the company Du Pont de Nemours under the trade name "Dytek A". The product from the cyclization reactor is maintained in the gas phase and directly passed through the second reactor. This reactor contains 3 g of the dehydrogenation catalyst of example 20 (grain size 0,315-1 mm). The reactor temperature is 280oC, pressure = 1 bar. In the process of experience educt MPDA turns into raw materials (3-MP Roh), which consists of a mixture of the following composition: 74,9% MPI, 13.9% of MPDA, 5.1% of organic impurities (mainly methylcyclopentadiene) and 6.1% of water. The results with the corresponding values MHSV (MHSV per reactor) are presented in table. 5.

Example 45. Continuous transformation of a 2-stage 3-MP Roh 3-picoline with intermediate connected smalloutline. In contrast to example 44, the educt has a different structure and between the first and second reactors built malatjalian.

In the om grains 0,315-1 mm

The educt is a raw material (3-Mr Roh) of the following composition: 45% MPI, 29.9% of MPDA, or 9.8% of organic impurities (mainly methylcyclopentadiene) and 14.5% of water. Starting material (educt) is evaporated and the current carrier gas 15 ml/min H2and MHSV = 4.2V, at a pressure of approximately 1 bar and the temperature of the reactor 320oC, is passed through the reactor. The product from the cyclization reactor is passed through malatjalian (115oC) and directly injected into the second reactor. This reactor contains 3 g of the dehydrogenation catalyst of example 23 (grain size 0,315-1 mm). The reactor temperature is 280oC. After 335 hours reaction time the organic phase product in the quantitative conversion of MPDA and MPI contains a 94.6% PIC and 5.4% of organic impurities (GC-F1.-%). Deactivation of the catalyst is not observed.

1. The method of obtaining 3-methylpiperidine by cyclization of 2-methyl-1,5-diaminopentane in the gas phase in the presence of a catalyst based on aluminum oxide, wherein the catalyst used activated aluminum oxide, mixed aluminum oxide and silicon, or a natural or synthetic zeolite, which have a ratio of acidic to basic centers on the surface of the above 2 and a specific surface area of above 40 m2/g, and% is 3-methylpyridine, characterized in that obtained from 2-methyl-1,5-diaminopentane 3 methylpiperidin under item 1 is passed through the second catalyst is a dehydrogenation catalyst.

3. The method according to p. 2, characterized in that the dehydrogenation is carried out at 220 - 400oC.

4. The method according to p. 2 or 3, characterized in that the dehydrogenation catalyst used noble metal on the carrier.

5. The method according to p. 4, characterized in that the noble metal is used platinum or palladium.

6. The method according to p. 5, characterized in that the dehydrogenation catalyst used palladium on amorphous SiO2/Al2O3prepared by ion exchange with a soluble palladium complex.

Priority points:

02.04.93 on PP.1-5;

06.01.94 - p. 6.

 

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