Vapor phase methylation of m-Cresol over Ce-impregnated Cd1-xCrxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) ferrospinels

Article abstract of DOI:10.14233/ajchem.2017.20362

Cd-Cr ferrospinels prepared by co-precipitation method were impregnated with cerium as promoter. Ce-impregnated ferrospinels were tested for the vapor phase alkylation of m-cresol with methanol. It has been observed that with increase in value of 'x' in C

Full text of DOI:10.14233/ajchem.2017.20362

Asian Journal of Chemistry; Vol. 29, No. 4 (2017), 905-907
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2017.20362
Vapor Phase Methylation of m-Cresol over Ce-Impregnated
Cd1-xCrxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) Ferrospinels
*
MALVIKA KADIAN and R.K. GUPTA
Department of Chemistry, Guru Jambheshwar University of Science & Technology, Hisar-125 001, India
*Corresponding author: E-mail: malvikadian@gmail.com
Received: 20 October 2016;
Accepted: 3 December 2016;
Published online: 31 January 2017;
AJC-18270
Cd-Cr ferrospinels prepared by co-precipitation method were impregnated with cerium as promoter. Ce-impregnated ferrospinels were
tested for the vapor phase alkylation of m-cresol with methanol. It has been observed that with increase in value of ‘x’ in Ce-impregnated
Cd1-xCrxFe2O4 ferrospinels, the selectivity of 2,5-dimethyl phenol increases considerably. The reason for the improved catalytic selectivity
may be due to the preferential adsorption, the strong synergistic effects among the different metal components and the relative changes in
the redox nature of catalysts.
Keywords: Impregnated ferrospinels, Alkylation, m-Cresol.
INTRODUCTION
EXPERIMENTAL
Alkylated phenol derivatives find numerous industrial
applications for the synthesis of several intermediates [1,2].
2,5-Dimethyl phenol (2,5-DMP) is used as an intermediate
for the synthesis of antiseptics, antioxidants and dyes. 2,3,6-
Trimethyl phenol (2,3,6-TMP) is used as a starting material
for the synthesis of vitamin E. Starting from m-cresol and
methanol as the alkylating agent, 2,5-dimethyl phenol can be
selectively synthesized.
The increasing demands for catalyst materials with desired
properties in the field of environmental legislation continues
to prompt the researchers worldwide for developing better and
environmentally safe catalysts. Ferrospinels possessing spinel
structure acts as an efficient catalyst for the large number of
industrially important alkylation reactions [3-6]. Supported
metal particles also play a vital role in heterogeneous catalysis
[7,8]. In order to further enhance the catalytic effectiveness,
the catalysts have been modified by impregnated with suitable
metal ion. Impregnation consists in contacting a solid catalyst
with the solution containing the components to be deposited
on the surface of the catalyst. Impregnated ferrospinels shows
improved catalytic activity due to preferential absorption,
strong synergistic effects and relative redox changes in the
catalyst [9]. In the present investigation, an attempt has
been made to synthesize and characterise Ce-impregnated
Cd1-xCrxFe2O4 ferrospinels in order to study their catalytic role
in the vapor phase alkylation of m-cresol with methanol.
Synthesis of Ce-impregnated CrFe2O4 (Ce-CC-5): A
series of Cd1-xCrxFe2O4 ferrospinels prepared by low temperature
co-precipitation method were impregnated with 0.2 mol Ce by
wet impregnation method. Co-precipitated CrFe2O4 (CC-5)
ferrospinels were impregnated with aqueous solutions containing
0.2 mol cerium chloride heptahydrate in 50 mL of water. After
standing at room temperature for 24 h, water was evaporated by
heating the samples at 393 K for 24 h in oven. Subsequently the
dried solids were calcined at 773 K for 16 h. Finally, the product
was sieved through a sieve of 6/10 mesh size [10].
Similarly, Ce-impregnated CdFe2O4 (Ce-CC-1), Ce-impreg-
nated Cd0.75Cr0.25Fe2O4(Ce-CC-2), Ce-impregnated Cd0.5Cr0.5Fe2O4
(Ce-CC-3) and Ce-impregnated Cd0.25Cr0.75Fe2O4 (Ce-CC-4)
were synthesized.
Catalyst characterization: The synthesized Ce-impreg-
nated Cd1-xCrxFe2O4 ferrospinels were characterized by X-ray
diffraction (XRD) technique primarily used for the phase
determination of crystalline materials. The XRD diffractogram
were recorded on a Rigaku X-ray diffractometer in the 2θ range
of 10-80° using CuKα radiations (λ = 1.54 Å) at a scan rate of
2 °/min as shown in Fig. 1. The peak intensities were found to
be almost same as those of the parent sample thus revealing the
crystalline nature of Ce-impregnated Cd1-xCrxFe2O4 ferrospinels.
Catalytic activity studies: The vapor phase methylation
of m-cresol was carried out on 9 g of 6/10 mesh sized Ce-
impregnated Cd1-xCrxFe2O4 ferrospinels placed between two

906 Kadian et al.
Asian J. Chem.
finally analyzed by gas chromatography with flame ionization
detector.
Ce-CC-5
Ce-CC-4
RESULTS AND DISCUSSION
The vapor phase alkylation of m-cresol with methanol
as the alkylating agent has been carried out over Ce-imp-
regnated Cd1-xCrxFe2O4 ferrospinels. A mixture of O- and C-
alkylated products i.e. 3-methyl anisole (3 MA), 2,5- and 2,3-
dimethyl phenols (DMP) and 2,3,6-trimethyl phenol (2,3,6-
TMP) and various other alkylated phenols were obtained as
represented in Fig. 2. Furthur, position 5 of the aromatic ring
is favoured because in order to minimize the steric hinderance,
methyl group of m-cresol will settle in opposite direction. As
a result, the selectivity of 2,5-dimethyl phenol increases.
The effect of Ce-impregnated Cd1-xCrxFe2O4 ferrospinels on
the vapor phase alkylation of m-cresol with methanol was studied
at 598 K, weight hour space velocity (WHSV) of 0.4 h-1 and m-
cresol to methanol molar ratio of 1:3 and the results obtained are
reported in Table-1 and shown by Fig. 3. It can seen that with
increase in ‘x’ values in Ce impregnated ferrospinels, the m-
cresol conversion decreases but the selectivity of the desired
product 2,5-dimethyl phenol increases considerably. Over Ce-
CC-5 catalyst, the maximum selectivity of 82.57 % of 2,5-
dimethyl phenol with 63.23 % m-cresol conversion was obtained.
This enhanced selectivity upon Ce impregnation may be
attributed to preferential adsorption, strong synergistic effects
between the different metal components and modified redox
properties of Cd1-xCrxFe2O4 ferrospinels.
Ce-CC-3
Ce-CC-2
Ce-CC-1
20
40
60
80
2θ (°)
Fig. 1. X-ray diffractogram of Ce-impregnated Cd1-xCrxFe2O4 ferrospinels
plugs of glass wool in a continuous fixed bed down-flow reactor.
The catalyst was activated at 773 K in a flow of dry air for 2 h
and then brought down to the desired reaction temperature by
cooling in a current of N2 gas of 30 mL/min. The reactant
mixture containing m-cresol and methanol was fed through a
10 mL pressure equalizing funnel into the reactor and the
products were condensed with the help of an ice-cold trap at
the bottom of the reactor. The phenolic products obtained were
OH
OH
OH
OH
CH H C
3
3
C-Alkylation
CH3OH
+
+
+
CH
CH
CH
3
3
CH
3
3
CH
3
m
-cresol
2,3-DMP
methanol
2,5-DMP
Major product
3,4-DMP
O-Alkylation
Furthur alkylation
OCH
3
OH
H C
CH
3
3
CH
3
CH
3
3-MA
2,3,6- TMP
Fig. 2. Probable reaction for the methylation of m-cresol

Vol. 29, No. 4 (2017)
Vapor Phase Methylation of m-Cresol over Ce-Impregnated Cd1-xCrxFe2O4 Ferrospinels 907
TABLE-1
PERFORMANCE OF Ce-IMPREGNATED Cd1-xCrxFe2O4 FERROSPINELS IN THE ALKYLATION OF m-CRESOL
WITH METHANOL AT 598 K, WHSV 0.4 h-1 AND m-CRESOL/METHANOL MOLAR RATIO OF 1:3
Catalyst
Ce-CC-1
Ce-CC-2
Ce-CC-3
Ce-CC-4
Ce-CC-5
m-Cresol conversion (%)
2,5-DMP yield (%)
51.67
2,3,6-TMP yield (%)
2,5-DMP selectivity (%)
Others yield (%)
3.170
72.34
71.48
65.97
63.49
63.23
17.50
17.27
12.51
12.47
10.31
71.43
73.84
77.08
79.49
82.57
52.80
50.86
50.48
52.21
1.413
2.602
0.544
0.707
significantly upon Ce impregnation. On a large scale appli-
cation, selectivity of desired product is more important than
activity. A maximum selectivity of 82.57 % of 2,5-dimethyl
phenol with 63.23 % m-cresol conversion was obtained over
Ce-CC-5 at 598 K, WHSV of 0.4 h-1 and m-cresol/methanol
molar ratio of 1:3.
80
70
60
50
40
30
20
10
0
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