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CATALYTIC SYNTHESIS OF PYRIDINE DERIVATIVES AND THEIR
CORROSION INHIBITION PROPERTIES
1
Choriyev R.E.,
2
Mukhiddinov B.B.,
2
Turobjonov S.M.,
1
Kadirov Kh.I.
1
Tashkent Institute of Chemical Technology, Tashkent
2
Tashkent State Technical University named after Islam Karimov, Tashkent
https://doi.org/10.5281/zenodo.15526041
Abstract.
The study established that acetaldehyde reacts with ammonia in
an autoclave in the presence of a catalyst with a mass fraction of 1-20% for 3
hours at 130-160°C, at a mol ratio of CH
3
CHO:NH
3
= 1:3, 2-methyl-5-ethylpyridine
is formed as the main product.
Keywords:
ammonia, acetaldehyde, catalyst, alkylpyridines, catalytic
synthesis, heterocycles, heterocycles, carbonyl compounds
Foreign synthetic industrial processes for obtaining pyridine bases are
based on the catalytic gas-phase cyclocondensation of aldehydes and/or ketones
with ammonia in the presence of amorphous aluminosilicates promoted by Ni, Cr,
Cd, Zn or Th compounds. The yield of pyridine bases in these processes is 40-60%
[1]. In these processes, zeolite ZSM-5 was used as a catalyst in the synthesis of N-
heterocycles, including pyridines.
The author [2] investigated catalytic compositions for the synthesis of
pyridine and pyridine bases on hierarchically porous zeolites (micro/meso;
micro/macro; micro/meso/macro) and showed that the condensation of
carbonyl compounds with ammonia proceeds with a high yield in the presence of
4 zeolite catalysts. It was also established that the reaction of acetaldehyde with
ammonia in an autoclave in the presence of 1-20% by mass of the catalyst for 3
hours at a temperature of 130-160 °C, in a molar ratio of CH
3
CHO:NH
3
= 1:3, leads
to the formation of 2-methyl-5-ethylpyridine as the main product.
These studies also showed that the MEP yield in the micro-meso-macro-
porous structure sample was 1.5 times higher than in the initial micro-porous
sample H-ZSM-5, which indicates the influence of mesoporousness formation on
catalytic properties and increased selectivity towards heterocycles.
In the case of N-Yh zeolite samples with different (0.70; 0.87; 0.95) showed
that the selectivity for MEP increases somewhat with the increase in αNa and
reaches 93% in the sample 0.95H-Yh, and it was concluded that the MEP yield also
changes equally from 58% (0.70H-Yh) to 63% (0.95H-Yh). Optimal conditions for
changing the decationization stage of H-Yh zeolite were established, along with
an increase in the number of high-molecular-weight compounds (up to 10 wt.%),
which ensured an increase in the MEP yield by 63%:150 C, with a 3-mol ratio of
CH3CHO:NH
3
= 1:3.
To date, methods for the technical synthesis of alkylpyridines from various
organic compounds have been developed. All alkylpyridine production plants in
the world use only carbonyl compounds and ammonia as raw materials..
The process of obtaining a mixture of pyridine and 3-methylpyridine from
carbonyl compounds and ammonia is well-studied. "Navoiazot" JSC launched
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production of 20 thousand tons of formaldehyde per year and 7 thousand tons of
formaldehyde per year. In this regard, the process of jointly obtaining pyridine
and 3-methylpyridine from acetaldehyde, formaldehyde, and ammonia was of
interest.
The heterocyclization reaction of carbonyl compounds with ammonia (and
amines) includes complex parallel-sequential reactions, including nucleophilic
addition reactions of ammonia, isomerization, dehydrocyclization, and others. All
these processes can be combined in the vapor phase using catalysts with
multifunctional properties. Based on this, the role of each component in the
pyridine and methylpyridine formation reaction was considered when selecting
the catalyst composition.
The heterocyclization reaction of the croton fraction with aniline and o-
aminofenol in the presence of mixed polyfunctional catalysts was investigated,
composition, wt.%: Cd - 3.0-5.0; ZnO - 5.0-10.0; Cr
2
O
3
- 3.0-5.0; Fe
2
O
3
- 3.0-5.0; -
Al
2
O
3
- 75.0-86.0.
Composition of the croton fraction, wt.%: croton aldehyde - 57.4 - 66.95;
paraldehyde - 13.45 - 29.47; acetone - 0.63 - 10.56; the rest - water.
Catalysts were prepared by methods of suspension, molding, washing,
drying, and purification. Aluminum oxide (PPP-33%) was used as a hydrate
carrier. 3-5% solutions of fluic and acetic acids were used as peptizers. The
textural properties of the developed catalysts were determined (Table 1).
Table 1
Physicochemical and operational properties of the developed catalysts
№
Composition,
% by mass..
Relative
surface
area, mg/h
Mechanical
strength, MPa
Service life until
regeneration,
hour
Output,
g/kg*time*h
1.
CdF
2
– 3,0
ZnO – 5,0
Cr
2
O
3
– 5,0
Al
2
O
3
– 87,0
225
6,8
68,0
81,0
2.
CdF
2
– 5,0
ZnO – 5,0
Cr
2
O
3
– 3,0
Fe
2
O
3
– 3,0
Al
2
O
3
– 84,0
240
7,8
96,0
101,0
3.
CdF
2
– 5,0
ZnO – 5,0
Cr
2
O
3
– 5,0
Fe
2
O
3
– 3,0
Al
2
O
3
– 82,0
225
7,3
72,0
98,0
4.
CdF
2
– 5,0
ZnO – 10,0
Cr
2
O
3
– 3,0
Fe
2
O
3
– 5,0
196
8,0
120
122
5.
CdF
2
– 5,0
ZnO – 5,0
184
8,2
184
130
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Cr
2
O
3
– 5,0
Fe
2
O
3
– 5,0
Al
2
O
3
– 80,0
The condensation reaction of the croton fraction with ammonia and amines
was carried out in a stainless steel reactor with dimensions δl = 25×1000 mm
under flow conditions with external electric heating and a catalyst volume of 100
cm3. The analysis of liquid products was carried out by the GJX method (LXM-
8MD chromatograph, I-modification, heat conductivity modification, detection,
mobile phase - zelit 545, column temperature - 120, absolute calibration).
Table 2
Influence of temperature on the yield of target products
croton fraction: ammonia = 1: 2; Gav. = 200 h-1, catalyst No. 6
№ Tempera-
ture, °C
Amount in the catalyst, %
by-
products
Croton
fraction
conver-
sion
2-
methylpyri
-dine
4-methyl-
pyridin
2-methyl-5-
ethylpyridine
1.
370
18,0
12,0
11,0
14,0
56,0
2.
380
22,0
16,0
14,0
18,0
64,0
3.
390
32,0
22,0
20,0
26,0
85,0
4.
400
38,0
25,0
25,0
12,0
95,0
5.
410
36,0
24,0
26,0
14,0
98,0
6.
420
37,0
23,0
25,0
15,0
98,0
7.
430
33,0
22,0
20,0
25,0
99,0
The reaction of the croton fraction with ammonia was carried out at a
temperature of 360 - 420 C in the presence of catalyst No. 6. The main products
of the reaction were a mixture of 2 and 4 - methylpyridine (up to 50%), 2-methyl-
5-ethylpyridine 360 - 420 C (up to 26%). As byproducts, acetonitrile, a mixture of
di- and trimethylpyridine, resins, and water are formed.
The influence of temperature, volumetric velocity, the ratio of initial
reagents, the height of the catalyst layer, etc., on the yield of target products and
the conversion of the croton fraction was studied. The influence of temperature
was studied in the range of 360-420C (Table 2).
As can be seen from the table, the reaction does not proceed at
temperatures below 360°C. With an increase in temperature to 400°C, the yield
of the target products gradually increases and reaches its maximum at 400°C. This
leads to a decrease in the output of the target product.
The study of the volumetric rate of target products, crotone fraction
conversion, and process selectivity showed that with an increase in the
volumetric rate of ammonia from 150 to 300 h-1 and an increase in the crotone
fraction from 0.1 to 0.7 h-1, the pyridine yield gradually decreases. This indicates
that the process occurs in the region of internal diffusion.
To improve solubility, extraction phosphoric acid was added to the
obtained mixtures in a ratio of 1:0.25. The obtained products were tested as
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corrosion inhibitors in a hydrochloric acid environment. To study the inhibitory
properties, compounds No. 2 and No. 3 were selected, which ensure maximum
yield of heterocyclization products. The influence of the inhibitor concentration
on the corrosion rate of St.20 steel in 15% hydrochloric acid (t = 50°C; τ = 42
hours) was studied.
Table 3
Influence of inhibitor concentration on the corrosion rate of St.20 steel grade
Inhibitor concentration,
%
Corrosion rate, g/m2.h
Protection level, %
Mix № 6
No additions
13
-
0,8
2,0
41,0
1,0
1,4
43,3
1,2
2,4
47,8
1,6
3,2
63,7
2,1
4,2
83,6
2,2
4,4
87,5
Mix № 7
0,8
2,0
51,0
1,0
1,4
52,2
1,2
2,4
53,6
1,6
3,2
71
2,1
4,4
98
2,2
4,46
99,5
Table 4
Influence of temperature on corrosion rate and degree of inhibitory protection
during corrosion of St.3 steel in 15% HCl in 3% hydrochloric acid. The inhibitor
concentration is 2.2%.
№
HCl acid solution
Corrosion rate, g/m
2
h
Protection efficiency,
%
Room temperature, τ=24 hours
1
No additions
4,7
-
Inhibitory
1,4
71,0
Temperature 40°C, τ=4 hours
2
No additions
46,2
-
Inhibitory
0,5
99,0
Temperature 80°C, τ=4 hours
3
No additions
131,0
-
Inhibitory
2,0
98,0
Temperature 100
C, τ=1 hours
4
No additions
1020
-
Inhibitory
4,9
99,5
As can be seen from the table data, "mixture No. 7" is a more effective
corrosion inhibitor at a concentration of 0.8-2.2% for 42 hours, protecting the
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metal from corrosion up to 99.5%, and the protective effect of "mixture No. 6" is
less than 90%.
To obtain stable and highly effective corrosion inhibitors, compositions
based on a more effective heterocyclization product - "mixture No. 7" were
prepared:
1)"mixture No7" (0.6%) + urotropin (0.3%) + acrylic emulsion (0.1%) -
"composition 1."
2)"mixture No7" (0.5%) + thiourea (0.3%) + copper salt (0.2%) -
"ingredient2."
* In brackets, the mass percentage of the inhibitor added to 12% hydrochloric
acid is indicated.
HCl (1); HCl "mixture No7"
(2); HCl "Mixture 1" (3).
Figure 1. Dependence of
corrosion rate on temperature
It should be noted that only those inhibitors of hydrochloric acid corrosion
that have a raw material base and are not scarce have been studied. In addition,
the possibility of reducing the corrosive activity of hydrochloric acid by
emulsifying it in a hydrocarbon medium was studied.
As can be seen from Figure 1, the most effective of the investigated
corrosion inhibitors in the temperature range from 20 to 100 C is "Composition
1." The corrosion coefficient with "Composition No. 7" in a 12% hydrochloric acid
medium at 90°C is 130 g/m
2
.h (or 76.9%), and with "Composition 1" is 17 g/m2.h
(or 91.0%). Compared to "No7 Mixture," the composition consisting of "No7
Mixture," urotropin, and acrylic emulsion has several advantages, the main one
being that the latter does not clog the lower plaster zone during treatment.
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HCl (1); HCl mixture No7
(2); Mixtures of HCl 2 (3).
Figure 2. Temperature
dependence of corrosion
rate 20
As can be seen from Figure 2, the corrosion rate of 20% HCl acid in a
hydrophobic emulsion medium with a phase ratio of 75/25 decreased 4 times
compared to the corrosion rate in a 12% HCl acid medium at the same
temperature for "mixture No7."
Thus, the corrosive activity of "mixture No. 7," inhibited by hydrochloric
acid, decreases 20 times compared to the addition of urotropin and acrylic
emulsion at 100C.
We are conducting targeted research on the development of new highly
effective methods for obtaining pyridine and quinoline bases based on local raw
materials.
At Navoiazot JSC, the production of acetylene, acetaldehyde, methanol,
ammonia, and other potential raw materials for the production of synthetic
pyridine bases has been mastered. Previously, the processes of obtaining pyridine
and its homologs based on acetylene and ammonia (methanol) were studied.
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Figure 3. Technological
scheme for the production
of pyridine and pyridine
bases: G - gas holder for
ammonia; E2, E3 - croton
fraction capacities; T4 -
evaporator; R5 - reactor;
T6 - cooler; E7 - Catalyst
Capacity
The working amount of ammonia from the gas holder (pos. G) and the
croton fraction from the container (pos. E2) enter the mixer-evaporator (position.
T4), where the mixture is heated to a temperature of 100-120 °C. Further, the
mixture enters the upper part of the reactor (pos. P5). The steam-gas mixture
exiting the reactor is cooled in a cooler (pos. T6) and is collected in a container
(pos. E7).
The work is devoted to obtaining pyridine bases based on a large amount of
acetaldehyde production waste - croton fraction.
Individual products are separated by rectification in a rectification column. The
cubic volume of the rectification column is 1.9 m3, the column height is 6000 mm,
the diameter is 200 mm, and the nozzles are made of Rashig rings measuring 20
x 20 mm.
Thus, we studied the heterocyclization reactions of the croton fraction with
ammonia and acetylene. The optimal parameters of the studied processes have
been established, and a flexible technology for obtaining pyridine bases has been
developed.
REFERENCES
1. Filippova N.A. Sintez piridinov podpadayet pod kristallicheskiye i
amorfnyye alyumosilikaty. Avtoreferat dissertatsii na poisk uchenoy stepeni
kandidata khimicheskikh nauk. Ufa. 2022. S.8-20.
2. N.G. Grigor'yeva. Mezoporistyye alyumosilikaty v sinteze N-
geterotsiklicheskikh soyedineniy/ N.G. Grigor'yeva, M.R. Agliullin, S.A. Kostyleva,
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S.V. Bubennov, V.R. Bikbayeva, N.A. Filippova, B.I. Kutepov, N. Narender //
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