DE2051316C3 - Process for the preparation of pyridine - Google Patents

Description

The invention relates to a method for . Production of pyridine from crotonaldehyde, formaldehyde and ammonia in the presence of a catalyst.

The production of pyridine, together with small amounts of picolines, by reaction of crotonaldehyde, formaldehyde and / or methanol as and ammonia at elevated temperatures in the gas phase on a fixed bed or fluidized bed contact is, for. B. in British patents 742 643, 971174, 1135 854 and German patents 1,214,689, 1,545,740. In general, according to this process, the gaseous reactants are in the presence of a dehydration and dehydration catalyst (e.g. SiO ₁ - Al ₁ O ₁₁ ), which in a preferred embodiment contains oxides of titanium, zirconium, cerium or thorium and / or fluorides of cadmium, Zinc etc. were added, brought to implementation at temperatures between 300 and 60O ^{0 C.}

It is known that the SiOg - Al ₁ O ₃ -KaIaIySStOr used in this process loses its activity quite quickly due to carbon deposits, so that it is necessary to remove the catalyst from time to time by roasting with air, e.g. B. according to British Patent 1135 854 to euf a residual carbon content of 1% to reactivate. It has been shown, however, that this method of activating the catalyst significantly reduces the service life of the catalyst. The practically complete oxidation of the carbon leads to a considerable extent to the bursting of the contact bodies and thus to a reduction in the optimal activity and the service life of the catalyst.

When proceeding according to the process according to the invention, a catalyst with an extremely high and constant activity is now used, which compared to the previous _; Beli <Mten catalysts has the extraordinary advantage that it delivers practically constant pyridine yields of about 73% of theory with a long service life. . ■ »,, ■

The invention thus provides a process for the preparation of pyridine by reacting crotonaldehyde, formaldehyde and ammonia in the presence of steam and e, ne _? carbon-containing SiO ₃ - Al A 'catalyst be, 45O ⁰ C a space velocity of ^ W per hour and a residence time of about 6.37 seconds in the hot bed Vei, which is characterized in that the KuÄ content of 85% SiO ₁ and 15 · /. AUO, the existing catalyst is kept in the range from 13 to 17% by continuous regeneration outside the reaction zone and a molar ratio of crotonaldehyde to formaldehyde to ammonia to steam of 1: 1.85: 2: 5.25 is maintained.

In contrast to the technical teaching from British patent specification 1135 854, according to the Regeneration of the catalyst with a carbon content of 1 to 2% is recommended, it has now been found that running pyridine yields of c <wa 73% of theory can only be obtained if the carbon content of the catalyst is through continuous regeneration kept at 13 to 17%

will. . , ,,,

The continuous regeneration of the catalyst takes place in a regenerator outside the reaction zone in a manner known per se by oxidation with air - conducted in such a way that there is a carbon content of the catalyst adjusts from 13 to 17%, and the thus regenerated catalyst is continuously the Reactor fed back.

The plant can be started up with a carbon-free catalytic converter. Did the Kataly & atot then after some time a carbon content approximately at the level according to the invention is achieved the desired carbon content is set by driving over the regenerator with air, and from there onwards

held. ,.

The formaldehyde is preferably in aqueous Form used, e.g. B. as a 37% aqueous solution; but he can also z. B. can be used in gaseous form.

The invention is illustrated using a few examples, which are compiled in the table below, explained in more detail.

The reaction product is contaminated with small amounts of / 7-picoline and other alkyl pyridines. The pyridine and the other pyridine bases can be selected by any suitable known method the reaction mixture can be obtained, e.g. B. by fractional distillation or extraction with a • suitable solvent.

Type Pyridine and ß-Picolia from crotonaldehyde / formaldehyde / ammonia Type SiO ₁₁ IAl ₁ O, catalyst carbon reactor
exit reactor % reactor
input */· weather· Circular Fluid 85:15 * Circulation";
speed •/•weather. 9 Betspiel rendes Contact bed
cross-section KonUktbcll-
volume Cracking 85:15 ml / h 7th 15th whirl cm· cm ¹ Catast 85:15 240 13th 16 1 bed 7.1 100 85:15 240 14th 17th 2 7.1 100 85:15 240 15th 26th 3 7.1 100 240 24 4th 7.1 100 240 5 7.1 100

continuation

ffiif:

Reaction P.cskiior.s-Bcdingüngcn Stockings
mingling
gewhwin-
age Stay-
time
NTP Contact
bed ·
tempera
door Croton
aldchyd Stoflelnsatz We »he ammonia Molars
Implementations in Pyridine time
per mole
CfötOR
aldehyde cm / s S. ⁰ C gmol deoiling gmol "/. example H Space-
speed
age 5.88 6.37 450 1.0 Formally
dehydration 5.25 2.0 / J-picoline 49.6 4th Ι) " ¹ 5.88 6.37 450 1.0 gmol 5.25 2.0 % 70.1 1 4th 565 5.88 6.37 450 1.0 1.85 5.25 2.0 19.6 72.7 2 4th 565 5.88 6.37 450 1.0 1.85 5.25 2.0 8.0 71.0 3 4th 565 5.88 6.37 450 1.0 1.85 5.25 2.0 6.6 51.1 4th 4 ^- 565 1.85 7.9 5 565 1.85 12.0

id- »!,

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Claims (1)

Claim; ;. ■ Method of manufacture, of Pyrjdin diireb Implementation of crotohiidftfiyil, formaldehyde and Ammonia in the presence of water vapor and S. . a carbon-containing SiO ₁ - · AUO ^ catalyst at 450 ⁰ C, a space velocity of about 565 per hour and a residence time of about 5.37 seconds in the fluidized bed process, characterized by the fact that the carbon 'Stoffgehalf'des; au3185 / ¹¹ ApSiQ, and 15% ΑΙ, Ο ₃ existing catalyst kept by continuous regeneration outside the reaction zone in the range of 13 "to * 17% and a mol ratio of crotonaldehyde to formaldehyde to ammonia to water vapor like 1 : 1.85: 2: 5.25 is observed,