ISSN 0036-0244, Russian Journal of Physical Chemistry, 2006, Vol. 80, No. 6, pp. 892–898. © Pleiades Publishing, Inc., 2006.
Original Russian Text © I.B. Borodina, E.B. Pomakhina, Ts.M. Ramishvili, O.A. Ponomareva, A.I. Rebrov, I.I. Ivanova, 2006, published in Zhurnal Fizicheskoi Khimii, 2006,
Vol. 80, No. 6, pp. 1022–1028.
CHEMICAL KINETICS
AND CATALYSIS
The Mechanism of Phenol Methylation
on Acid and Basic Zeolite Catalysts
I. B. Borodinaa, E. B. Pomakhinaa, Ts. M. Ramishvilib, O. A. Ponomarevaa, A. I. Rebrovc,
and I. I. Ivanovaa
a Faculty of Chemistry, Moscow State University, Leninskie gory, Moscow, 119899 Russia
b Melikishvili Institute of Physical and Organic Chemistry, Academy of Sciences of Georgia, Tbilisi, Georgia
c Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, Moscow, 117912 Russia
e-mail: OAPonomareva@phys.chem.msu.ru
Received October 20, 2005
Abstract—The alkylation of phenol with methanol on HY and CsY/CsOH catalysts was studied in situ under
static conditions by 13C NMR spectroscopy. Attention was largely given to the identification of intermediate
compounds and mechanisms of anisole, cresol, and xylenol formation. The mechanisms of phenol methylation
were found to be different on acid and basic catalysts. The primary process on acid catalysts was the dehydra-
tion of methanol to dimethyl ether and methoxy groups. This resulted in the formation of anisole and dimethyl
ether, the ratio between which depended on the reagent ratio, which was evidence of similar mechanisms of
their formation. Subsequent reactions with phenol gave cresols and anisoles. Cresols formed at higher temper-
atures both in the direct alkylation of phenol and in the rearrangement of anisole. The main alkylation product
on basic catalysts was anisole formed in the interaction of phenolate anions with methanol; no cresol formation
was observed. The deactivation of acid catalysts was caused by the formation of condensed aromatic hydrocar-
bons that blocked zeolite pores. The deactivation of basic catalysts resulted from the condensation of phenol
and formaldehyde with the formation of phenol-formaldehyde resins.
DOI: 10.1134/S0036024406060094
INTRODUCTION
reactions to be identified and the pathways of their
transformations determined.
The demand for cresols and xylenols is many times
greater than their resources in coal-tar raw materials
[1]. Synthetic methods for their production therefore
remain an object of interest in current research. One
such method is the alkylation of phenol with metha-
nol. This method can be used to obtain various prod-
ucts of phenol methylation in the aromatic nucleus
and at the functional group depending on the acid–
base properties of the catalyst used. These products
are used as starting materials for the preparation of
phenol resins, antioxidants, dyes, plasticizers, and
perfumes.
The purpose of this work was to study the mecha-
nism of phenol alkylation with methanol on acid and
basic catalysts by 13ë NMR spectroscopy in situ.
EXPERIMENTAL
The catalysts used were zeolites HY and CsNaY
modified with cesium hydroxide (CsY/CsOH). The
degree of sodium ion exchange with protons and
cesium ions was 77 and 65%, respectively. The content
of the modifier recalculated to Cs2é was 34.3 wt % in
CsY/CsOH. A detailed description of the preparation of
catalyst samples and their characteristics was given in
[12–14].
Catalytic experiments on phenol methylation with
methanol were conducted in a flow reactor at atmo-
spheric pressure, 673 K, and weight rate of supplying
reagents 1 g/(g h). The molar ratio between phenol,
methanol, and N2 was 1 : 1 : 3. The conditions of chro-
matographic analyses of liquid and gaseous reaction
products are described in [15].
Zeolites are promising alkylation catalysts. They
have certain advantages over Friedel–Crafts catalysts
currently used in industry and mineral acids [2–5]. The
creation of high-effectiveness heterogeneous catalysts,
perfection of the technology of their preparation, and
prediction of their catalytic properties is, however,
often impeded by the absence of detailed data on the
mechanisms of chemical transformations on these
materials.
In recent years, the method of NMR spectroscopy in
The mechanism of phenol methylation was studied
situ [6–11] has been successfully used to study the in situ by NMR spectroscopy. Air-dry catalyst samples
mechanisms of reactions on the surface of zeolites. This (0.08–0.10 g) were placed into NMR ampules, evacu-
method allows intermediate compounds formed in the ated at 10–5 torr and 673 K, and cooled to 298 K. The
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