NEW COMPOSITE CATALYSTS FOR THE SYNTHESIS OF ACETONITRILE
415
mono- and dialuminates in the ratio СаAl2O4/
СаAl4O7 = 0.25–0.35. Sample 1, double copper calcium
aluminate, was prepared by thermal decomposition of
ammonia–carbonate copper solution (ACCS) at 90°С
in the presence of Talyum. Catalyst 2 was prepared
from sample 1 by adding 30% Talyum, stirring the
mechanical mixture, and its forming into pellets 25 mm
in diameter under a pressure of 2 t cm–2. This pressure
is two times lower than that commonly used (4 t cm–2),
so as to obtain higher porosity of the pelletized sample.
The subsequent treatment of these pellets with water
at 90°С leads to heterogeneous ion exchange and to
enhancement of the mechanical strength of the pellets
owing to the Talyum hydration. Catalyst 3 was prepared
from sample 1 by adding 40% Talyum, similarly to
catalyst 2. Sample 4 was prepared for comparison by
thermal decomposition of ACCS on the surface of
pseudoboehmite (Al2O3·H2O) produced by Sasol under
trade name Disperal. Sample 5 was prepared using as
starting components mixed Cu–Zn hydroxocarbonate
(double salt) synthesized by thermal decomposition
of an ammonia–carbonate solution of copper and zinc
with the preset Cu/Zn ratio and Talyum. A small amount
of the forming solution containing aqueous ammonia
was added to the initial mechanical mixture, and the
components were thoroughly mixed to obtain a plastic
mass. Then, this mass was formed to obtain extrudates,
which was subjected in succession to treatment with
humid air (25–35°С) and hydrothermal treatment
(90°С, 2 h) and was dried at the preset temperature.
Sample 6 was prepared similarly to sample 5 using as
starting component the modified double salt into which
a part of Talyum was introduced as modifying additive
in the course of synthesis. Catalyst 7 was prepared by
introducinghydratedzirconiumoxidealongwithTalyum
into the ammonia–carbonate solution of copper and
zinc. Sample 8 was prepared by thermal decomposition
of ACCS on the surface of the support prepared by
heterogeneous ion exchange between basic zinc
carbonate (BZC) and Talyum in water. Copper calcium
aluminate sample 9 was prepared by mixing basic copper
carbonate (BCC, malachite) with Talyum in water (S :
L ratio 10 : 1, 70°С, 4 h), followed by drying at 120°С.
Sample 10 was synthesized by the reaction of mixed
copper magnesium hydroxocarbonate with Talyum in
distilled water. The mixed salt itself was prepared by
mixing BCC with basic magnesium carbonate (BMC) in
aqueous ammonia. Catalyst 11 was prepared by thermal
decomposition of ACCS on the surface of the support
prepared by heterogeneous ion exchange between BMC
of the formula 4MgCO3·Mg(OH)2·5H2O, Talyum, and
СаО in water. Calcium oxide was added to bind all the
СО32– ions from BMC, which is “too rich” in СО32– ions
compared to the other basic carbonates, e.g., to those of
copper and zinc.
The quantitative decomposition of the samples
prepared was determined analytically. The method for
determining the weight fraction of copper (counting
on CuО) is based on the reduction of bivalent copper
into univalent copper with potassium iodide in a weakly
acidic solution. The iodine released in the process
is titrated with a sodium thiosulfate solution in the
presence of starch. Determination of the weight fraction
of zinc (counting on ZnO) is based on titration of zinc
with Na2EDTA in a weakly alkaline solution (pH 8–9)
in the presence of Methylthymol Blue indicator. The
interfering ions are masked with ammonium fluoride
and thiourea. Determination of the weight fraction of
aluminum (counting on Al2O3) is based on binding
of aluminum and interfering ions with Na2EDTA, the
excess of which is titrated with a solution of zinc chloride
at pH 6 in the presence of Xylenol Orange indicator.
After that, the aluminum complexonate is broken down
with ammonium fluoride, and Na2EDTA released in the
amount equivalent to the aluminum amount is titrated
withazincchloridesolution. Determinationoftheweight
fraction of magnesium (counting on MgO) is based on
complexometric determination of magnesium at pH
10.0 in the presence of Methylthymol Blue indicator.
The interfering ions are masked with triethanolamine
and thiourea. Determination of the weight fraction of
zirconium (counting on ZrO2) is based on titration of
zirconium with Na2EDTA in a strongly acidic solution
(0.3–0.6 M HCl) in the presence of Xylenol Orange
indicator.
X-ray diffraction analysis was performed with a
DRON-3M diffractometer equipped with a graphite
monochromator, using CuKα radiation. The phases were
identified in accordance with the JCPDC file. Complex
thermal analysis was performed with and OD-103 optical
derivatograph at a heating rate of 5 deg min–1. The total
porosity was determined by the pycnometric method,
and the specific surface area, by the BET method from
the low-temperature nitrogen adsorption.
The chemical composition of samples 1–11 is given
in Table 1. The specific surface area is of the order of 80 ±
20 m2 g–1 and depends on the composition of Talyum-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 3 2016