Synthesis of 2-methylpyrazine on ternary oxide catalysts

Article abstract of DOI:10.1007/s11167-005-0456-z

Synthesis of 2-methylpyrazine by cyclocondensation of ethylenediamine with 1,2-propylene glycol in the presence of zinc-molybdenum-chromium catalysts was studied.

Full text of DOI:10.1007/s11167-005-0456-z

Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1093 1095. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
005, pp. 1114 1116.
Original Russian Text Copyright
2
2005 by Kagarlitskii, Krichevskii, Balpanov.
CATALYSIS
Synthesis of 2-Methylpyrazine on Ternary Oxide Catalysts
A. D. Kagarlitskii, L. A. Krichevskii, and D. S. Balpanov
Institute of Phytochemistry, Ministry of Education and Science of the Kazakhstan Republic,
Karaganda, Kazakhstan
Received July 20, 2004; in final form, April 2005
Abstract Synthesis of 2-methylpyrazine by cyclocondensation of ethylenediamine with 1,2-propylene glycol
in the presence of zinc molybdenum chromium catalysts was studied.
2
-Methylpyrazine (MP) is used as an intermediate
stage of the process is the reaction of 1,2-PG adsorbed
on the catalyst surface with EDA supplied with the
gas phase to form MP (387 C) [8]. The system EDA
1,2-PG is more complicated than that described by
the reaction equation, since synthesis of MP is ac-
companied by formation of by-products [9].
in synthesis of pyrazine-2-carboxamide (the basis of
Pyrazinamide antituberculous drug [1]), but the exist-
ing procedures of its preparation are not perfect.
MP can be prepared by the reaction of propylene
oxide with ethylenediamine (EDA) in methanol in the
presence of zinc molybdenum chromium oxide cata-
lyst (yield 63%) [2]:
Initially this process was studied in the presence of
granulated binary zinc molybdenum oxide catalysts.
The highest yield (75%) was obtained with the cata-
Me
NH2
lyst of the composition ZnO : MoO = 1.0 : 0.3 (gran-
CH
3
N
N
Me
H C
Cat.,
ule size 1.0 2.0 mm) [10].
2
.
+
HO
(1)
H C
2
CH2
EXPERIMENTAL
NH2
The similar process was developed by the Priklad-
naya Khimiya Russian Scientific Center [3]. An im-
portant draw-back of this process is the use of highly
explosive initial products (propylene oxide and hy-
drogen) and of toxic methanol as a solvent.
To increase the yield of the target product through
decreasing the amount of polymeric deposits at the
catalyst surface, it was suggested to add chromium(III)
oxide to binary oxide systems, since Cr O has high
oxidation and dehydrogenation power. In addition, it
was assumed that, owing to its characteristics, it will
enhance the mechanical strength of the catalyst gran-
ules during thermal drying.
2
3
From the viewpoint of industrial safety and avail-
ability of fairly cheap starting compounds, the
catalytic dehydrocyclization of EDA with 1,2-propyl-
ene glycol (1,2-PG) is a more promising route to MP:
Table 1 shows how the ratio of components of
H
NH2
NH2
H2
Me
HO
N
Me
Table 1. Yield of MP at various catalyst compositions.
Temperature 460 C, contact time 3.3 s
H C
CH
Cat.,
2
+
2
H O
2
H C
CH2
N
H
2
HO
Molar ratio
Catalyst operation Yield of MP,
ZnO : MoO : Cr O
time, h
%
3
2 3
N
N
Me
N
N
Me
.
(2)
1
.00 : 0.30 : 0.05
7
9
67
78
69
73
82
76
71
76
64
2
H2
1.00 : 0.30 : 0.10
1
1
1
1
1
1
.00 : 0.30 : 0.15
.00 : 0.40 : 0.10
.00 : 0.40 : 0.15
.00 : 0.40 : 0.20
.00 : 0.50 : 0.15
.00 : 0.50 : 0.20
10
23
27
21
17
22
24
The attempts to use Al O as a catalyst of this
2
3
process failed due to its low selectivity [4]. However,
the purity of alkylpyrazines was improved and the
yield of MP was increased to 64% with zinc oxide
catalysts [5 7].
In dehydrocyclization of EDA with 1,2-PG on the
Pd/Zn Cr O catalyst (Zn : Cr = 1 : 3), the limiting
1.00 : 0.50 : 0.25
1
070-4272/05/7807-1093 2005 Pleiades Publishing, Inc.

1094
KAGARLITSKII et al.
and molybdenum(III) oxides in these catalysts corre-
Y, %
sponded to the molar ratio of 1.0 : 0.3, they lost their
activity and selectivity in 7 10 h, whereas at the
molybdenum(III) oxide content of 0.4 and 0.5 mol per
mole of zinc oxide they operated without regeneration
for a period from 21 to 27 h depending on the amount
of chromium(III) oxide added.
The best result were obtained with the cata-
lyst of the composition ZnO : MoO : Cr O =
3
2 3
1
.00:0.40:0.15.
The yield of MP exceeding 70% is reached on this
catalyst in a wide temperature range, from 370 to
4
3
30 C, and the highest yield (80 90%), at 380
95 C, which is a relatively low temperature for these
reactions (see figure).
T, C
As regards contact time, it can be varied in a wide
range (from 1.5 to 7.5 s), and in this case the yield of
MP can be no less than 65% due to decreasing content
of polycondensation products (PCPs) in the catalyzate
Yield in synthesis of MP Y as a function of the process tem-
perature T at a contact time of 4.2 s. (1) EDA, (2) 1,2-PG,
(
3) MP, and (4) PCPs.
(
Table 2). In the range 4.4 6.0 s, the yield of the
mixed zinc molybdenum chromium oxide granulated
catalyst affects the MP yield.
target product reaches 80 88%.
Evaluation of the working time of the catalyst
showed that the catalyst is able to operate for 55 57 h
without noticeable variation of selectivity with respect
to the target product, ensuring its yield as high as
85 90% (Table 3).
The yield of the target product on the catalysts
tested was from 65 to 82%. When the content of zinc
Table 2. Yield of MP at various contact times c. Tem-
perature 390 C
The ZnO : MoO : Cr O = 1.0 : 0.4 : 0.15 catalyst
3
2 3
Unchanged, wt %
Yield, %
PCPs MP
was prepared by mixing zinc, molybdenum(III), and
chromium oxides to obtain a homogeneous mass.
Granules were prepared from this mixture on a pan
granulator with adding 5% NaOH and 10% aqueous
polyvinyl alcohol for strengthening. The granules
were sifted through a sieve, and a 1.0 2.0-mm frac-
tion was collected. Then, the granules were dried for
3 h at 105 C. Dry granules were promoted with 3%
aqueous MnSO and 1% H PO . After promotion,
c,
1
s
EDA
1,2-PG
2
15
10
3
3
18
12
5
4
2
1
5
65
77
88
85
72
55
1
3
4
6
7
9
.5
.0
.4
.0
.5
.0
4
2
4
10
21
32
2
5
4
3
4
1
2
the granules were subjected to air calcination for 5 h
with a stepwise increase in temperature in the range
1
00 150, 150 250, 250 350, and 350 600 C. The
Table 3. Yield of MP at various time . Temperature
90 C, contact time 4.4 s
final catalyst consists of greenish porous granules.
3
MP was synthesized on an installation equipped
with a stainless steel flow-type tubular reactor (tube
diameter 20 mm, length 80 cm), in which 150 cm of
the catalyst was placed. An equimolar mixture of
EDA with 1,2-PG, diluted with water (20 vol %) and
preliminarily passed through a vapor heater with a
temperature of 280 300 C, was fed to the reactor.
The experiments were carried out for 1 h. The reaction
products were cooled in a trap system. In a typical
synthesis, a mixture containing 67 ml of EDTA
Unchanged, wt %
Yield, %
PCPs MP
c,
s
3
EDA
1,2-PG
1
2
3
4
5
6
0
16
8
2
3
5
3
77
86
90
87
85
74
0
0
0
0
0
4
5
1
2
2
8
1
9
5
10
5
11
(1 mol), 73 ml of 1,2-PG (1 mol), and 28 ml of water
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005

SYNTHESIS OF 2-METHYLPYRAZINE ON TERNARY OXIDE CATALYSTS
1095
(
1.56 mol) was fed into the reaction mixture with a
regeneration reaches 50 55 h, and the total working
life of the catalyst is 400 450 h.
1
dosing pump at a rate of 0.79 ml min . MP was iso-
lated from the reaction mixture by distillation on a
column in the form of an azeotropic mixture with
water (bp 97 C/737 mm Hg, MP content 45% [11]),
from which the target product was extracted with
chloroform or diethyl ether. After drying and removal
of the solvent, MP was extracted by distillation on a
column; a fraction with bp 133 135 C was collected.
After the second distillation, MP had the following
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3
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2-methylpyrazine, St. Petersburg: Prikladnaya Khi-
miya Russia Scientific Center, 1994.
characteristics: bp 135 C, n2 1.5050, d4 1.030,
which is in good agreement with published data [12].
0
20
D
4
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6
7
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1
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nitrile as internal reference.
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CONCLUSION
The catalyst Zn : MoO : Cr O = 1.00 : 0.40 : 0.15
3
2 3
was developed. The use of this catalyst in cyclocon-
densation of ethylenediamine with 1,2-propylenegly-
col allows preparation of 2-methylpyrazine in 85 90%
yield. The working life of the new catalyst before
12. Bader, A., Harvey, D., and Nagarkatti, G., Aldrich
Handbook of Fine Chemicals, Milwaukee, Wisconsin:
Aldrich Chem., 1990, p. 1113.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005