Journal of Catalysis 217 (2003) 107–116
Selective N,N-methylation of aniline over cocrystallized zeolites RHO
and zeolite X (FAU) and over Linde type L (Sr,K-LTL)
and S.L. Suib
Institute of Materials Science, University of Connecticut, Storrs, CT 06269, USA
Department of Chemistry, U-60, University of Connecticut, Storrs, CT 06269-3060, USA
Department of Chemical Engineering, University of Connecticut, Storrs, CT 06269, USA
Department of Chemical Engineering, Northeastern University, 342 Snell Engineering, Boston, MA 02115, USA
Received 9 September 2002; revised 27 January 2003; accepted 29 January 2003
Alkylation of aniline (PhNH
) with methanol (MeOH) over cocrystallized zeolite RHO–zeolite X (FAU) and over zeolite Linde type L
(Sr,K-LTL) as catalysts has been studied. Cocrystallized zeolite RHO–zeolite X (FAU) favors the formation of N,N-dimethylaniline
(NNDMA) with high selectivity > 90%, having an advantage over pure zeolite X (FAU) of staying active even after 10 h of reaction.
Activity of cocrystallized RHO–zeolite X (FAU) is higher than that for Sr,K-LTL in terms of the production of N,N-dimethylaniline.
2003 Published by Elsevier Science (USA).
Keywords: Aniline; Methylation; Cocrystallized zeolites; Zeolite RHO; Zeolite LTL; Zeolite X; N,N-Dimethylaniline
Synthesis of N,N-dimethylaniline (NNDMA) is an indus-
trially important process due to its use as a raw material in
organic syntheses as well as its role as an intermediate in
dye-stuff production and in the pharmaceutical and agro-
chemical industries . The gas-phase reaction involving
the alkylation of aniline (PhNH
) with methanol (MeOH)
has been previously studied using several different kinds of
materials such as clays, zeolites, and composites. Layered
double hydroxides (LDH) known as hydrotalcites (HT) con-
taining magnesium and aluminum have also been studied
for this reaction with the formation of only a single product
(N-methylaniline) . In the case of ZSM-5, the extent of
conversion using this material increases with increasing alu-
minum content . This reaction has been catalyzed using
AlPO4-5, AlPO4-11, CoAPO-5, CoAPO-11, ZAPO-5, and
ZAPO-11 with the formation of N-methylaniline (N-MA),
N,N-dimethylaniline, and N-methyltoluidine (N-MT) where
the product distribution has been found to be inﬂuenced by
the space velocity and the aniline to methanol ratio as well
as the acidity of the catalyst .
E-mail address: firstname.lastname@example.org (S.L. Suib).
N-methylation products have been reported as being pre-
dominant over Al-HMS mesoporous molecular sieves .
Oxides such as γ -alumina have also been used with N-
methylation being the predominant reaction product .
Vanadium-incorporated aluminophosphate molecular sieves
(VAPO-5 and VAPO-11) lead to the selective formation of
N-methylanilineand N,N-dimethylaniline . High selectiv-
ity to N-methylaniline is obtained over metallosilicates .
N-Methylation of aniline with methanol over MgO catalysts
has also been reported . Zeolites X and Y ion-exchanged
with Li, Na, K, Rb, and Cs also have been used for this re-
action. NNDMA is produced mainly over zeolite X. NMA
is produced over zeolite Y. A mixture of N and C methyl-
ated products can be obtained over the more acidic form of
the zeolites. A rapid deactivation of zeolite X (completely
deactivated in 6 h) has been reported .
In this work the synthesis of N,N-dimethylaniline from
methanol and aniline over cocrystallized RHO and X (FAU)
zeolites and over Linde type L (Sr,K-LTL) zeolite is re-
ported. We have studied effect of the different zeolite X to
zeolite RHO ratios on the activity and selectivity of the gas-
phase reaction involving alkylation of aniline with methanol.
To the best of our knowledge there are no previous reports of
the use of cocrystallized zeolites and Sr, K-LTL as catalysts
for this reaction.
0021-9517/03/$ – see front matter 2003 Published by Elsevier Science (USA).