DE2244169A1 - METHOD FOR MANUFACTURING IMINES - Google Patents

Description

Di * F.2titfiete »rt » on, »Dr. E. Astmann *) O / /, 1 CQ

Dr »fcKo * nig * berger - Dip !. Phye. R. Holzhauer. <. 4. t * t IV ν /

Dr. F. Zumstein jun.

Patent attorney

• Munich 2, BrtufeauMtraß · 4 / lü

12/10 / me
Case 506

SNAM PROGETTI S.p.Α., Milan / Italy

Process for the production of mines

The present invention relates to a process for the preparation of imines, starting from a primary aromatic amine and a carbonyl compound, especially an aliphatic, cycloaliphatic or aromatic ketone "

These compounds are particularly important in the field of industrial _chemistry} because they can be used for the synthesis of some compounds, among which zuersj the nitrogen-containing heterocyclic compounds, indole and quinoline may be mentioned, as intermediates for dyes, pharmaceuticals, corrosion inhibitors, additives can be used for plastic materials etc. »

There are also methods for the synthesis of imines known based on the implementation of amine and carbony! compounds of the following Type based:

R ¹ . R ¹

R-NH ₀ + O = C ZZZi RN = C + H ₀ O 2 \ \ ²

R "■ ^N R"

where R, R ¹ and R "can be alkyl or aryl radicals and R 'and R" can be identical or different.

309812/1245

It is an equilibrium reaction, its yield is limited by the amount of water present in the system and by simultaneous condensation reactions of the carbonyl compound or the imine itself.

The difficulties listed above, which occur in all previously known synthetic methods, prevented their development with regard to their industrial utilization.

In the German patent specification (German patent application P by the same applicant by the same

dedatum with the working title "Case 507") describes a process for the production of imines which is based on the use of a fixed bed of molecular sieves through which the mixture of amine and ketone is circulated, in which it is possible to produce imines with a selectivity of greater than $ 95 up to $ 100> with almost complete conversion of the reaction components.

The use of molecular sieves makes it possible to achieve the above-mentioned high selectivities in a short time, of less than k hours, by working at temperatures in the range between 0 ° and 80 ° C. and at an amine / ketone ratio in the range from 6: 1 to 1: 6, preferably from 2: 1 to 1: 2, it being preferred to use stoichiometric ratios or an excess of the reaction component with the lowest boiling point.

The amount of molecular sieves that must be used in order to achieve almost complete conversion of the reactant is present in an amount less than the stoichiometric amount, is preferably in the range from 200 to 100 g of molecular sieves per mole of the reactant present in an amount below the stoichiometric amount.

In the case of aliphatic ketones in particular, the high selectivity values are achieved by using reaction times, which are less than 2 hours at a temperature below 50 ° C.

309812/1245

It will- the use of v "öjä" MöielciiiärgieBen W ¥ §e§eii§ri $ lie "full ^ Ä / 4 A * - 5 A ^ p or of Meri ^ laN; sifa ΜΙοΒϋ% eiiipÄaai äelfceü reagent * Sie Üegeö if! dei *! "orm vöü f ^ i-vei? © Her von blstteh verseHiedeöer Größeiri νοί'ί ϊϊϊ eiriei * measuring vessel in the above mentioned area. Örimd on their chäräkteristischeh isothermal AET) SGrpti6n§iirii6h they are ¹ enabled the ganäe v / ater to absorb that can occur theoretically during the reaction.

In contrast to the usual methods, the above-mentioned method can advantageously be used on an industrial scale for production are used by imines »

This is made possible by the measures which form the subject of the present invention and which essentially consist in carry out the conversion to imine synthesis in a reactor, suitably equipped with a plague bed of molecular sieves.

The mixture of amine and ketone is continuously passed or circulated through the sieve bed.

After the molecular sieves have become inactive, what you go through an analytical control can determine, for example on the concentration of unreacted amine in the effluent is directed from the reaction system, the feed mixture is diverted to a second reactor, which has a bed contains regenerated sieves while the first reactor is being regenerated. The regeneration cycle of the molecular sieves can be carried out by any conventional method.

With reference to the accompanying drawing, there is now an implementation scheme of the method according to the invention described, but this is not intended to represent a restriction.

It is left to the person skilled in the art to determine the appropriate number of work units and the time for each work process

^choose - 309812 / mE

1 and 2 represent the storage tanks for the amine and the ketone, respectively The two reagents are fed into reactor 4 through J5. The mixture flowing out comes out through 5 and becomes the vacuum stripping column or "stripping" ·: Column 6 passed, which can be used to remove the excess of a reaction component or the unreacted amine and Remove ketone if a satisfactory conversion is not achieved. The excess reaction component or the unreacted Reaction components are stored through 7 in the intermediate storage tank 8, whereas the imine, which is at the bottom of the Column 6 is obtained as a "tail product" through 9 into the storage tank 10 is stored, from which it can be withdrawn and sent to the subsequent processing.

Sometimes the column 6 is not necessary and the imine that is from the by

Reactor73 comes, can directly through the bypass line 11 after lO be sent. When the reaction phase has ended, the regeneration of the molecular sieves begins. First will a solvent introduced through 12, which is withdrawn from the tank 15 became. The wash solution exiting through 14 is sent to column 15 where the solvent is recovered.

The solvent obtained as the supernatant in 15 is brought to tank Ij5 again through 16.

The product at the bottom of column 15, which consists of a mixture of amine and ketone, which is partially converted to the imine is returned to reactor 4 through 17 and 3 in the following reaction phase.

In the zxveiten regeneration phase steam is of I50 - passed 200 ⁰ C by 18 in the reactor 4 and effluent by I9 is condensed and discharged into the sewer or collector after optionally the organic phase was separated, possibly from the reagents or the used solvent consists of the previous washing phase.

309812/124 1:

Last becomes dry; Gas heated to 500 to 35O ° C through initiated in 4 and the moist gas flowing out is directed into the chimney.

The mixture flowing out of the reaction stage is generally one or more distillation stages subjected to to obtain the imine, which is sent for further use.

In some cases, the product flowing out of the reaction stage can be used as such for further use.

In particular when imines are produced by condensation of an aromatic amine with an aliphatic ketone, for example of aniline and acetone, are obtained, it is necessary to add the reaction mixture subject to a rapid distillation to remove the excess ketone and thus possible subsequent To prevent condensation reactions between the ketone and the imine which reduce the yield of the desired product would.

example 1

320 g molecular sieves of the Linde 5 A type in the form of tablets of 0, ^ 18 cm (1/8 ") were placed on a support mesh in a stainless tube 2.222 cm (7/8 ") inner diameter steel was introduced.

A mixture of aniline and acetone in a ratio of 1: 4 was passed through the fixed bed of the molecular sieves from the top to the bottom circulated by means of a centrifuge pump at room temperature. The implementation was terminated when the aniline conversion Was under $ 90. After the feeding was stopped, the following became Regeneration carried out:.

a) washing with v / ater at room temperature to obtain an outlet from which no organic phase separated,

b) heating to zu'150 ⁰ C and treatment with steam 150-170 ° C

during et;, - / a JO minutes,

30 9 8 1? / Ϊ 2

c) heating up to 30O ⁰ C and treatment with air of 300 for about 1 hour,

d) cooling in a stream of dry air to room temperature.

All operations a) - d) were carried out in about 3 hours. The results obtained after three successive reaction stages, alternating with just as many regeneration stages of the molecular sieves are listed in the following table.

Table 1 Regeneration effect

Aniline / acetone 1: 4 in mol - T - 20 ⁰ C

Time / min Molecular Sieves 5 A 1/8 "(0.318 cm) 320 g moles aniline Conversion %

Test A Test B Test C

41.5 41.1

81.2 81.0

90.3 90.4 95.0 94.7

The selectivity for imine was practically always 100 %.

Example 2

A 1: 1 molar ratio mixture of aniline and acetophenone was fed into the reactor of Example 1 from the bottom to the top Fed in at the end. The temperature was 70 ° C. The flow rate of the feed mixture was adjusted so that that it guaranteed a residence time of about 3 hours. The; Composition of the products was determined at the outlet by gas chromatography Analysis controlled.

BAD ORJGÜNAL 309817/12 A S

40.9 6o 80.9 90 89.7 120 94.7

During a test, a yield of N- (OC-methyl) -benzylideneaniline with a purity of 96 % was achieved for K hours, the only impurities being aniline and acetophenone.

The bed of molecular sieves was then regenerated by the procedures described in Example 1, with the exception of stage a), which in the present case by washing with toluene was replaced.

Ten reaction regeneration cycles were performed.

After the tenth cycle, the reaction was Iminkonzentration in the effluent product after 4 hours * 8 9 ^ fo "

309812/1241

Claims (1)

Claims 1.) Process for the production of imines, starting from aromatic Amines and aliphatic, cycloaliphatic or aromatic ketones, characterized in that a mixture of the two reaction components in a synthesis zone which consists of a fixed bed of molecular sieves, the mixture flowing out of the synthesis zone in a suitable manner treated to unreacted reagents and the generated Imin to win, and the molecular sieves used are regenerated. 2.) The method according to claim 1, characterized in that the Implementation in the range from 0 to 80 ° C is carried out. 5.) The method according to claim 1, characterized in that the reaction is carried out with an amine / ketone ratio in the range between 6: 1 and 1: 6, preferably between 2: 1 and 1: 2. 4.) Process according to claim 1, characterized in that the reaction between an aromatic amine and an aliphatic Ketone is carried out with reaction times of less than 2 hours. 5 ·) Method according to claim 4, characterized in that the Reaction is carried out at a temperature below 50 C. 6.) The method according to claim I ^ characterized in that the Molecular sieves used are preferably of the type of 3 A, 4 A and 5 A sieves. 7.) Method according to claim 6, characterized in that the amount of molecular sieves used is in the range from 200 to 400 g 3 0 9 8 17 Π? 4 5 Molecular sieves per mole of in an amount below the stöehioinetriscnen Amount of available reagent to be used * 8.) Process according to one of the preceding claims, characterized in that aniline is used as amin and acetone as ketone. 9 ») Method according to one of the preceding claims, characterized in that the amine is aniline and the ketone is acetophenone be used. 309812/1245 Blank page