N-METHYLATION OF p-ANISIDINE ON THE CATALYSTS BASED
353
most active sample is CuAl-1 (Table 2). This may be surface of the CuAl-2 sample prepared with a carbon-
due to the difference in the size of copper particles
present on the surface of the samples.
The morphology of the CuAl-1, CuAl-2, and
CuAl-4 samples reduced at 300°C in a flow of hydro-
gen was studied by TEM. The TEM images of the
CuAl-4 sample show both small particles, 7–10 nm in
size, and large copper clusters up to 200 nm in size
2−
3+
ate concentration [CO ] = 1.73[Al ], sodium atoms
3
are present, which affect the catalytic activity of this
sample. In the case of the CuAl-1 sample, which was
2
3
−
3+
prepared with the [CO ] = 0.86[Al ] ratio, sodium
ions were not found on the surface. The conversion of
p-anisidine on the CuAl-1 sample was 50%, which is
significantly higher than the conversion on the CuAl-2
sample (16%). Thus, it is necessary to study in more
detail the effect of the concentration of the precipitat-
ing agent used in the synthesis of layered double
hydroxides on p-anisidine N-methylation.
(
Fig. 6a), which can adversely affect the catalytic
activity of the sample in the target reaction. It is possi-
ble that larger copper particles carry out the methanol
steam reforming more actively. Therefore, its conver-
sion is 68% (Table 2), which is higher than on other
catalysts. The CuAl-1 and CuAl-2 samples contain
The effect of reaction conditions on the course of
particles that have an average size of 5.5 and 3.3 nm, p-anisidine N-methylation was also studied. CuAl-1
respectively (Figs. 6d and 6e). However, a narrower was chosen as a catalyst, since it is more active at a
particle size distribution was found in the CuAl-1 temperature of 200°C, a pressure of 4 bar, and a meth-
sample compared to the CuAl-2 sample. It can be anol concentration of 0.9 mol/L. A decrease in tem-
assumed that the main factor in determining the cata- perature leads to a decrease in the conversion of p-ani-
lytic activity of these two samples is the presence of sidine. Varying the pressure is also favorable for the
sodium ions on the surface, since with almost the decrease in the conversion, which may be due to side
same particle size, the conversion of p-anisidine dif- reactions in which methanol is consumed. A decrease
fers by 3 times. The measured interplanar distances in the amount of catalyst leads to a decrease in the
indicate the presence of the following phases in the conversion of p-anisidine, while an increase in the
CuAl-1, CuAl-2, and CuAl-4 samples: Cu O(111), reaction time contributes to its increase, and the selec-
2
tivity to N-methyl-p-anisidine remains almost
unchanged. Thus, in the future, it is possible to vary
the preparation conditions of the CuAl-LDH-1 sam-
ple with a Cu : Al ratio of 1 : 1 to obtain a more active
catalyst with its less loading in p-anisidine N-methyl-
ation at an optimum temperature of 200°C and a pres-
sure of 4 bar. It is also possible to promote this sample
with zinc ions to increase the conversion of p-anisi-
dine. It is also possible to use copper-containing lay-
ered double hydroxides in the N-methylation reac-
tions of other aniline derivatives.
Cu O(110); Cu(200), Cu O(111); and Cu(111),
2
2
respectively (Fig. 6). The presence of copper(I) oxide
Cu O on the surface of the sample is apparently
2
caused by the interaction of the sample with atmo-
spheric oxygen when the sample is transferred to the
TEM measurement chamber, because it was shown
previously by XPS that copper in the reduced samples
is only in the metallic state. The conversion of p-anisi-
dine in the N-methylation reaction on the CuAl-2
sample is only 16%, while this value reaches 50% on
CuAl-1. At this stage of work, it is difficult to say what
is the reason for such a difference in the catalytic activ-
ity of the two samples with the same Cu : Al ratio.
Apparently, the main reasons are the presence of
sodium on the surface of CuAl-2, different particle
sizes, and different concentrations of precipitation
agent during the synthesis of samples, which can affect
the degree of deposition of layered double hydroxides.
FUNDING
The work was performed as part of the state task of
the Institute of Catalysis, Siberian Branch, Russian
Academy of Sciences (projects 0303-2016-0004 and
АААА-А17-117041710083-5).
REFERENCES
CONCLUSIONS
1
. RF Patent 2472774, 2011.
Thus, the catalytic properties of samples based on
Cu-containing layered double hydroxides in p-anisi-
dine N-methylation reaction of were studied. The
p-anisidine conversion is shown to change nonlinearly
with decreasing Cu : Al ratio. The partial substitution
of zinc ions for copper ions contributes to an increase
in the catalytic activity of the synthesized samples.
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agent concentration on the catalytic activity of sam-
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increased content of carbonate ions in the precipita-
tion agent leads to stronger binding of sodium ions to
layered double hydroxide. Based on XPS data, on the
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KINETICS AND CATALYSIS Vol. 60 No. 3 2019