CS257645B1 - Method of pyridine and pyridine bases preparation - Google Patents

Abstract

Process for preparing pyridine and pyridine based on catalytic synthesis from ammonia and aldehydes at 350 to 500 ° C, preferably 400 to 420 ° C, such that the catalyst is pure alumina in alpha-gamma- or eta- -form with a porosity of 55 to 65%, preferably 60%, and a macropore volume of at most 0.22 up to 0.25 cm 2 / g, formulated in a suitable form tabletting or extruding tablets prints, balls, rings or granules.

Description

The invention relates to a process for the preparation of pyridine and pyridine bases.

The largest part of the world production of pyridine and pyridine bases is covered by their production by synthetic way and by catalytic synthesis from aldehydes and ammonia. It is generally known that when acetaldehyde is reacted with ammonia at a temperature of 300-500 ° C in the gas phase, 2-picoline and 4-picoline are formed as the main product, in addition to a small amount of pyridine and a number of higher alkylated pyridines, mainly lutidines and collidines. When acetaldehyde, formaldehyde and ammonia are involved in this reaction, the major components of the product are pyridine and 3-picoline. In addition, the aforementioned higher alkylated pyridines are again formed. This synthesis preferably takes place in the temperature range of 400 to 450 ° C at a molar ratio of acetaldehyde to formaldehyde to ammonia of 1: 1.25: 1.75 to 1: 1.5: 2.0 to 2.1.

However, the synthesis may also be carried out with other aldehydes, for example acrylaldehyde or by reaction of a mixture of crotonaldehyde, formaldehyde and ammonia, where the formaldehyde is in molar excess to crotonaldehyde. Their molar ratio is up to 3: 1, but usually 1.5 to 2.5: 1.

A very important factor in this synthesis is the use of a suitable catalyst. Numerous catalyst systems are reported in the literature, but silicon-aluminum catalysts with a high SiO ₂ content and activated by various metals and their compounds, usually oxides, are usually used.

The most commonly used catalysts have a SiO ₂ content of 80 to 90%. A? 0? 5 to 15%, activator up to 5%. For example, silicon-aluminum catalysts having the following composition and properties are disclosed

Content % Specific area Pore volume sio ₂ ^A1 ° 2 m ² / g cm / g 85 15 Dec 400 0.6 to 0.8 87 13 600 0.7 83 17 500 0.8 82 18 400 - 75 25 395 - 82 18 400 - As activators are used most often metals and oxides of elements Mg, Zr, Th, Ce, further fluorides ZnF ₂ , PbF ₂ , CdF ₂ , NH ₄ F, BrF ₃ , MnF ₂ .

Of the other less frequent elements W, Ni, Co, Cr, Mo, Fe, Pa, Al and their compounds.

Another type cited catalysts are phosphates such as Co-Al ₂ (PO ^), Co-Al ₃ (PO ^) _5, Co ₃ Al (PO ^) ^ CO ^ AlíPOp ^ and combinations thereof formed by mixing, where appropriate, furthermore activated above said oxides such as CdO.

In addition to these aluminosilicates, silica-aluminum gel and crystalline zeolite silicates having a content of 12-15% Al2O4 are also mentioned in the patent literature.

The duration of one cycle of catalyst activity is usually 21 to 23 reaction hours, but rarely less, 7 to 9 hours. After this time it has to be regenerated and activated by removing the deposited carbonaceous substances by burning with a mixture of nitrogen with about 3 to 5% oxygen at a temperature above 400 ° C.

It has now been found that said synthesis of pyridine and its derivatives proceeds well on pure alumina itself, both in its alpha and gamma form, and in transitional modifications, such as the eta form, if they have a suitable internal structure. The following alumina was used in laboratory experiments.

1) Al 2 O-gamma modification in the form of 5x5 mm tablets impurity content:

^Fe 2 ° 3 : 0,15 Si ° ₂ : 1,26 K ₂ O, Na ₂ 0: 0.10 n ° ₃ : 1,5% specific surface ....... .200 m ² / g total pore volume 0.51 cm @ 2 / g volume of macropores 0.28 cm @ 2 / g porosita 58.3% 2? Al? O? -Alpha and eta modifications, rings 4, ^Fe 2 ° 3 : 0.05 sieve ₂ : 1,80 CaO : 0,04 Na ₂ O 0.04 NO " : 0,70 specific surface 196 m / g total pore volume 0.56 cm @ 2 / g volume of macropores 0.22 cm ² / g porosity 62,9 3) A ^ Og-alpha-modification, 1.5 mm extrusion, ^Ke 2 ° 3 : 0,03 sieve ₂ : 0,02 Na ₂ O : 0,01 CaO : 0,04 specific surface 173.5 m ² / g total pore volume 0.54 cm @ 2 / g volume of macropores 0.06 cm ² / g porosity 62.9% 4) Al 2 O 3 -alpha-modification, extruded 0 2.8 mm ^Fe 2 ° 3 : 0.020% SiO ₂ : 0,025% Na ₂ O : 0,005% specific surface 162 m ² / g total pore volume 0.45 cn / g volume of macropores 0.05 cm @ 2 / g

porosity%

The experiments were carried out in a stainless steel reactor apparatus. The reactor part itself consisted of a preheating and mixing part, a reactor-filled reactor tube, and a transfer head reactor. The reactor tubes were replaceable and had inner diameters of 18.28 and 51 mm, respectively. The reactor was closed by a head with a thermometer probe and a cooled transducer. A set of efficient glass water coolers, a measuring cup and a glass flask were connected to this. Benzene was added to the flask, heated to ca. 70 ° C and excess ammonia was formed and the product components dissolved in benzene.

Extraction of pyridine bases with benzene facilitated their good separation from water. The temperature in the reactor was measured by a sliding thermocouple housed in the probe, the temperature of the reactor jacket, and thermocouple preheaters soldered directly to the wall of their body. Ammonia was taken in a gaseous state from a steel bottle, acetaldehyde similarly in a special stainless steel vessel, aqueous formaldehyde solution (36%) was added to a calibrated measuring cup and pumped from there by a metering pump and injected into an evaporator. The required amounts of the reaction products were adjusted and controlled by needle valves and rotameters. Total consumption was determined by weight.

The reactor tube was filled with catalyst to fill the fully heated portion of the reactor.

The condensed reaction product was collected in a measuring cup and admitted to the flask with the prescribed benzene at hourly intervals. Most of the dissolved ammonia was formed at 70 ° C and the pyridine bases were extracted into benzene. The crude product was separated into aqueous and organic fractions and the contents of the components were analyzed by gas chromatography. The invention is further illustrated by the following Examples 1 to 8. The results are set forth in the Table.

Table

Example # 1 2 3 4 5 6 7 Reactor mm 18 18 18 28 28 50 50 Reaction m.p. 405 400 405 415 422 429 430 Reaction time hr. 11 37 56 48 14 30 30 Staked mol / hour _t formaldehyde 0.91 - - - 0.81 - 3.02 acetaldehyde 1.01 1.63 1.54 1.84 1.51 3.12 2.40 ammonia 2.61 3.01 2.38 2.14 3.78 5.20 4.49 mol. ratio NH4 / aldehydes tot. 1.36 1.84 1.55 1.16 1.63 1.66 0.83 Catalyst 1 1 3 1 1 4 4 type of treatment tab. tab. print, . tab. tab. vytlač. copies quantity g 185 123 122 270 265 740 740 load cat. g / g Cat. 0.905 0.795 0,886 0.436 0,746 0.300 0.60 Product total moles 4,089 9.98 12,374 24.66 6.61 39.1 18.83 pyridine moles 2.27 1.50 1,25 1.19 3.11 1.81 9.13 2-picoline moles 0.14 3.42 4.63 9.02 0.48 13.00 0.81 3-picoline moles 1.20 - - - 1.89 - 5.87 4-picoline moles - 3.42 4.31 6.38 - 12.30 - number of regenerations 5 3 - 2 1 1 1 total reaction hours of catalyst 185 104 56 132 56 37 37 g prod. hours in the reactor 140.7 82.7 90.5 86.3 81.0 96.4 56.5 flow rate cm / min 26.6 13.71 14.16 5.9 12.74 3.74. 8.7

Example 8 ·

A φ 28 mm reactor was charged with 360 g of type 2 catalyst (N, N-alpha and ethoxy modification) and charged with 1.68 moles of acetaldehyde and 2.94 moles of ammonia per hour at 440 ° C. . The NH 4 / aldehyde molar ratio was 1.75 and the catalyst loading was 0.34 g / g hr. The reaction produced a product containing a total of 24.38 moles of pyridine bases, of which 2.38 moles pyridine, 8.60 moles 2-picoline and 8.45 moles of 4-picoline. After 62 hours of reaction, the catalyst was regenerated and continued in the next experiment up to a total load time of 149 hours. The vapor flow rate of the reactants and nitrogen through the reactor was 6.91 cm / min and the bulk yield was 74.25 g prod./hr. in the reactor.

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of pyridine and pyridine bases by catalytic synthesis from ammonia and aldehydes at a temperature of 350 to 500 ° C, preferably 400 to 420 ° C, characterized in that the catalyst is pure alumina in alpha-gamma or ethanes with porosity of 55 to 65 %, preferably 60% and a volume of 2 macropores of at most 0.22 to 0.25 cm / g, formulated in a suitable form by tabletting or extrusion of tablets, extrudates, spheres, rings or granules.