Catalytic activity of a mordenite catalyst in alkylation of xylenols with methanol

Article abstract of DOI:10.1007/s11167-005-0370-4

The catalytic activity of a palladium-containing mordenite catalyst in alkylation of 2,6-, 2,4-, 2,5-, 2,3-, 3,4-, and 3,5-xylenols with methanol was studied. The main and by-products of catalysis and the activity of the catalyst in synthesis of individual trimethylphenols were determined.

Full text of DOI:10.1007/s11167-005-0370-4

Russian Journal of Applied Chemistry, Vol. 78, No. 4, 2005, pp. 683 684. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005,
pp. 690 691.
Original Russian Text Copyright
2005 by Agaev, Madatzade.
BRIEF
COMMUNICATIONS
Catalytic Activity of a Mordenite Catalyst in Alkylation
of Xylenols with Methanol
A. A. Agaev and K. M. Madatzade
Sumgait State University, Sumgait, Azerbaijan
Received July 26, 2004; in final form, February 2005
Abstract The catalytic activity of a palladium-containing mordenite catalyst in alkylation of 2,6-, 2,4-,
2,5-, 2,3-, 3,4-, and 3,5-xylenols with methanol was studied. The main and by-products of catalysis and the
activity of the catalyst in synthesis of individual trimethylphenols were determined.
Methyl derivatives of phenol are consumed in con-
siderable amounts because of their being the most im-
portant half-products of small- and medium-tonnage
chemistry. However, the last decade exhibited not
only an absolute increase in the amount of their manu-
facture, but also, and to a greater extent, an expansion
of their assortment [1].
a column (3.6 m 4 mm) packed with dimenthyl-
phthalate (18 wt %) on Chromocorb W and catharom-
eter as detector. Dimenthylphthalate was synthesized
using an accelerated procedure from menthol and
phthalic anhydride.
To reveal the role of noncatalytic transformations,
preliminary experiments were performed under the
reaction conditions, but without a catalyst. In this case,
more than 98% of methanol and 100% of isomeric
xylenols (virtually all the isomers) were recovered in
an unreacted state, which indicated that there was no
reaction in the after-catalyst space [6]. In addition, it
was established that isomeric xylenols are isomerized
and disproportioned over the Pd-H-mordenite catalyst
Catalytic alkylation of phenols with methanol,
which is employed with success in manufacture of
ortho-cresol and 2,6-xylenol [2 4] or recommended
for use in synthesis of other isomers of mono- and
dimethyl derivatives of phenol, virtually has not been
systematically studied in synthesis of individual tri-
methylphenols.
1
under the conditions studied (350 , 0.8 h ) to only
The aim of this study was to examine the catalytic
activity of a mordenite catalyst in alkylation of iso-
meric xylenols with methanol.
a slight extent, because a study of transformations of
2,6-, 2,4-, 2,5-, and 3,5-xylenols in the presence of
Pd-H-mordenite without methanol demonstrated that
their conversion does not exceed 3.2%.
EXPERIMENTAL
Analysis of the results obtained in alkylation of
isomeric xylenols with methanol shows that this reac-
tion occurs by the concurrent-consecutive mechanism.
In this case, the alkylation of isomeric xylenols at
the carbon atom of the benzene ring is far ahead of
the methylation at the hydroxy group of a particular
xylenol. Formation of trimethylphenols via intramo-
lecular conversion of the resulting methyl esters of
the respective xylenols is unlikely at the given tem-
perature. According to the previously obtained data
[5, 7], such a scheme of formation of methyl homo-
logues of phenol in the presence of mordenite and
other zeolite catalysts is accompanied by a low selec-
tivity with respect to the target isomers.
Experiments on alkylation were performed in a lab-
oratory reactor under stationary conditions with a fixed
catalyst bed of volume 10 cm3. Synthetic mordenites
(SiO2 : Al2O3 molar ratio x = 25), containing Pd-H-
mordenite, served as catalysts. The mordenites were
obtained by treating a Na-mordenite (x = 10) with
a 1 N NH4Cl solution, with the subsequent washing
and drying. Palladium was introduced in an amount
of 1.0 wt % into grains of a mixture of a zeolite
and -aluminum oxide with an aqueous solution of
[Pd(NH3)4]Cl2. Before delivering the raw material,
the catalysts were calcined at 450 C in a flow of dry
1
air (1 h, 1000 h ) and then kept for 1 h in a flow
1
of hydrogen (1000 h ) at 410 C and a pressure of
It can be seen from the table that trimethylphenols
are formed rather selectively with respect to some
of the isomers. For example, 2,4,6-trimethylphenol is
0.1 MPa. The products formed were condensed in
a refrigerator-separator and analyzed by gas-liquid
chromatography on a Khrom-5 chromatograph with
1070-4272/05/7804-0683 2005 Pleiades Publishing, Inc.

684
AGAEV, MADATZADE
1
Alkylation of xylenols with methanol in the presence of a Pd-containing mordenite (T = 350 C, v = 0.8 h ,
xylenol : methanol molar ratio 2 : 1)
Con- Yield of tri-
ver- methylphenol
sion of in terms of
Yield of reaction products in terms of reacted xylenol, %
2,4,6-tri- 2,3,6-tri- 2,4,5-tri- 2,3,4-tri- 2,3,5-tri- 3,4,5-tri-
di-
tetra-
methyl- methyl-
xylen- a xylenol methyl- methyl-
methyl-
phenol
methyl-
phenol
methyl-
phenol
methyl-
phenol
ol, %
taken, %
anisole
phenol
phenol
phenols
Xylenol:
2,6-
35
48
40
51
53
58
28
35
32
41
45
40
2
80
73
8
8
11
13
7
10
17
2,4-
0.5
13
3
2,5-
79
80
2,3-
5
45
5
3,4-
40
1
6
3,5-
1
70
the main reaction product in methylation of 2,4- and
2,6-xylenols, mainly 2,4,6-trimethylphenol is formed
in methylation of 2,5- and 2,3-xylenols, and predom-
inant formation of 2,3,6-trimethylphenol is observed
in the catalytic system constituted by 3,5-xylenol and
methanol. In contrast to other xylenols, the 3,4-iso-
meter is methylated less selectively on the mordenite
catalyst. Methylation of 3,4-xylenol yields two iso-
mers, 2,4,5- and 2,3,4-trimethylphenols in a virtually
equimolar ratio. However, the total yield of these
isomers in terms of reacted 3,4-xylenol is rather high
(95%), and the conversion of 3,4-xylenol in a single
pass is practically important (53%).
activity of the Pd-containing mordenite decreases in
the following order: 3,4-xylenol > 2,3-xylenol > 3,5-
xylenol > 2,4-xylenol > 2.5-xylenol > 2.6-xylenol.
Under the conditions of catalysis, methanol is trans-
formed only slightly: it undergoes dehydration, de-
hydrogenation, decarbonylation, and decomposition.
Methyl ether, CO, CO2, and trace amounts of form-
aldehyde and ethylene were found in the gaseous re-
action products.
CONCLUSIONS
(1) A sufficiently high catalytic activity of a Pd-
containing zeolite catalyst in synthesis of individual
trimethylphenols and their mixtures from xylene iso-
mers and methanol was demonstrated.
It can also be seen in the table that the Pd-contain-
ing mordenite exhibits a sufficiently high selectivity
in methylation of isomeric xylenols. The highest se-
lectivity of the reaction with respect to the target
trimethylphenols is observed in the case of methyla-
tion of 2,6- and 2,3-xylenols (80%), and the lowest
(70%), in the case of a 3,5-xylenol. It should be noted
that the yield of trimethylphenols in terms of reacted
methanol is also high (74 88%).
(2) It was shown that, under the conditions studied,
the conversion of xylenols is 35 57% and the yield
of the main trimethylphenol in terms of a reacted xy-
lenol, 70 80%.
REFERENCES
In addition to the main isomers listed above, other
trimethylphenols are also formed under the reaction
conditions, but in a considerably lower yield. The con-
centration of the main trimethylphenol in the mixture
of its isomers varies rather widely (47 82%).
1. Maravek, J., Eur. Chem. News, 1998, vol. 69, no. 18,
p. 10.
2. Novikova, Yu.A., Khim. Prom st. Rubezh., 1979,
no. 9, pp. 47 61.
3. Kharlampovich, G.D. and Churkin, Yu.V., Fenoly
(Phenols), Moscow: Khimiya, 1974.
4. Jpn Patent Application 1148040.
5. Agaev, A.A., Methylation of Phenols on Oxide and
The composition of the tetramethylphenols obtained
is not complex and depends on the starting xylenol
only slightly. The 2,3,5,6-isomer predominates in
the tetramethylphenol fraction obtained in the case of
3,5-xylenol, and mostly 2,3,4,6-tetramethylphenol
is formed in other cases.
Zeoite Catalysts, Doctoral Dissertation, Baku, 1992.
6. Abaev, G.N., Zh. Prikl. Khim., 1965, vol. 38, no. 10,
pp. 2242 2252.
A comparison of the yields of the main reaction
products (trimethylphenols) in terms of a xylenol
taken demonstrated that, on the whole, the catalytic
7. Agaev, A.A., Eminov, G.O., and Pashaev, Z.M., Izv.
Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 1989,
no. 2, pp. 118 120.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 4 2005