JOURNAL OF CATALYSIS 172, 76–84 (1997)
ARTICLE NO. CA971837
Beta Zeolite as a Catalyst for the Preparation of Alkyl Glucoside
Surfactants: The Role of Crystal Size and Hydrophobicity
1
M. A. Camblor, A. Corma, S. Iborra, S. Miquel, J. Primo, and S. Valencia
Instituto de Tecnolog ´ı a Qu ´ı mica (U.P.V.-C.S.I.C.), Avenida de Los Naranjos s/n 46022, Valencia, Spain
Received January 31, 1997; revised July 21, 1997; accepted July 23, 1997
tive catalysts, it was observed that the adsorption of reac-
Zeolite H-beta is an active and selective catalyst for the acetaliza- tants and products played an important role in the kinet-
tion of the glucose to form alkyl glucoside nonionic surfactants. The ics of the process and therefore determined the conversion
characteristics of size and polarity of reactants, intermediates, and
products determine the strong influence of the textural properties
of the catalyst (crystal size and adsorption properties) on activity,
selectivity, and deactivation. For two series of zeolites with differ-
one (aliphatic alcohol), leading to a product which contains
ent concentrations of Si–O–Si connectivity defects an optimum in
activity is found for intermediate Si/Al ratios, this optimum being
reached at lower Si/Al ratios in the series with the lower defect con-
centration, i.e., in the more hydrophobic series. Thus, the optimum
catalyst of the hydrophobic series is more active than that of the hy-
drophilic series, and it also shows a better resistance to deactivation. being done by a combination of the adequate pore and
and product selectivity. This is not surprising if one takes
into account that the reaction occurs between a highly hy-
drophilic reactant (D-glucose) and a much less hydrophilic
both hydrophilic and hydrophobic moieties. Meanwhile, in
processes in which different-sized reactants and products
intervene, it becomes of paramount importance to control
the diffusion patterns within the pores of the zeolite, this
�
c 1997 Academic Press
crystallite size. Thus, it appeared to us that it should be pos-
sible to strongly affect the catalytic activity of zeolites for
the preparation of aklyl glucosides by changing their tex-
tural and hydrophobic–hydrophilic properties. In this work
we show that beta zeolite, conveniently modified along the
lines presented above, appears as a very adequate catalyst
to produce alkyl glucoside surfactants.
INTRODUCTION
Surfactants are present in many products which are com-
monly and largely used in our society. For instance, they
intervene in the composition of detergents, textile washing,
cosmetic products, and even in food production. Their eco-
nomical and ecological impact is especially important when
used as detergents. In this case a very important property is
the biodegradability which is related to the level of branch-
ing of the alkyl chain (1). This factor strongly determines
the production process and becomes in many cases the con-
trolling factor.
Recently alternative surfactants based on alkyl gluco-
sides with an alkyl chain between C8 and C18 have been
prepared (2). In this case glucosides derived from natural
products can be used as building blocks for the preparation
of nonionic surfactants which present excellent biodegrad-
ability and a low degree of skin and oral toxicity (3, 4).
We have presented in a recent work (5) that it is pos-
sible to prepare butyl glucosides by means of the Fisher
reaction using zeolites as catalysts. These lower glucosides
are fairly well soluble in a fatty alcohol and can be used as
intermediates for the manufacturing of higher glucosides
EXPERIMENTAL
Catalysts
In order to studythe effect ofthe crystallite size, following
the method presented in Ref. (7), we synthesized four beta
zeolites with different crystal sizes (0.05–0.90 �m) and very
similar Si/Al ratios (� 16). Scanning electron microscopy
(
ISI-SS60) was used to determine the crystal size and mor-
phology. The physico-chemical characteristics of each one
of these zeolites are given in Table 1.
In order to determine the role of the framework Si/Al
ratio and of the hydrophilic–hydrophobic properties of the
beta zeolite on the synthesisof glucosides, two series of sam-
ples with differnt Si/Al ratios were prepared. The first series
(
PS series) includes the zeolites obtained by dealumination
of a starting beta zeolite (VALFOR CP 806 B-25) from
PQ corporation, synthesized in the presence of sodium and
tetraethylammonium (TEA) cations. The dealumination of
the zeolite (8) was carried out by dispersing a 2-g sample in
(
6). While large pore acid zeolites were shown to be ac-
2
50 ml of a solution of nitric acid; the concentrations used
1
To whom correspondence should be addressed. Fax: 96-387 78 09.
were 8, 9, 9.2, 9.25, 10, 11, and 11.5 N in order to obtain
76
0021-9517/97 $25.00
Copyright �c 1997 by Academic Press
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