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M. Cadenas et al. / Applied Catalysis A: General 485 (2014) 143–148
Table 1
Properties of sulfonic macroreticular resins.
Nomenclature
Resin
A-35
5.32
A-46
0.87
CT-275
A-35
A-46
macroreticular ion-exchange resin Amberlyst 35
macroreticular ion-exchange resin Amberlyst 46
−1
Acid capacity (meq g
Specific surface area (m2 gd−r1y
Mean pore diameter (nm)
)
5.20
22
dry
)
29
57
CT-275 macroreticular ion-exchange resin Purolite CT 275
GC–MS gas chromatograph with mass detector
23.6
0.51
423
19.2
–
393
32.9
0.72
418
Mean particle diameter (mm)
Maximum temperature (K)
Ammonia adsorption enthalpy
−ꢀHads (kJ/mol)
no1-hex
nj
Sj
t
initial mole of 1-hexene (mol)
mole of component j (mol)
selectivity to product j (%)
time (min)
117
108
119
Porosity (%)
24
23
39
X1-hex
conversion of 1-hexene (%)
of olefin. The results could be interesting for refiners to reduce
olefins content in naphtha with high aromatics contents.
Subscripts
DAT
Dim
di-alkyl toluene
dimers
2. Experimental
1-hex
2-hex
j
MAT
TAT
1-hexene
2-hexene
component j
mono-alkyl toluene
tri-alkyl toluene
2.1. Chemicals and catalysts
Toluene (99.5%) and 1-hexene (99%) were obtained from
Sigma–Aldrich and used without further purification. Reaction
mixtures were prepared with toluene and 1-hexene at four initial
toluene/1-hexene weight ratios: 0, 0.125, 0.25 and 0.5.
Amberlyst 46 (A-46) (Rohm and Haas) and Purolite CT-275 (CT-275)
on the external surface. Some properties of these resins are listed
in Table 1 [17]. Pore volume and surface area in dried state were
calculated from nitrogen adsorption–desorption isotherms at 77 K.
The adsorption enthalpy of ammonia [18–20] was also included as
a relative measure of the acid strength of the ion exchange resins.
into account since excessive amounts of high molecular weight
oligomers and poly-alkylated aromatics can adversely affect the
gasoline pool blending specifications, particularly the end boiling
point of the corresponding fuel and they can also cause catalyst
deactivation from pore blockage.
As the knowledge of olefin oligomerization reaction can be
and olefin oligomerization are both main reactions some litera-
pylene is excessively abundant, many for butylenes, it is scarce
for pentenes and heavier olefins [8–10]. However, some papers
about oligomerization of biomass-derived C9 alkenes have recently
appeared [11,12]. It is surprising to notice that in the open litera-
ture the majority of the work on alkylations with olefins and olefins
oligomerizations employ mainly zeolites-based materials and solid
phosphoric acid, and only in a much reduced cases use acidic ion-
exchange resins, despite they can show an acid strength similar to
zeolites mentioned above in non-aqueous conditions [13]. In our
previous work [14], some macroreticular ion exchange resins were
active for 1-hexene oligomerization with a negligible amount of
tetramers and cracking products at temperatures lower than 383 K.
Comparatively, alkylation with olefins catalyzed by acidic resins
is a better documented reaction, but again oligomerization is usu-
ally considered as a side-reaction [15] and focused mainly in
benzene alkylation, being the 2-phenyl isomer the most preferred
system such for alkylation reaction with olefins, illustrating in these
kinds of reactions the importance of opening up the microstructure
of gel zone for reactivity. Focusing only on alkylation of toluene
catalyzed by ion exchange resins, a study [16] compared three
macroreticular resins (Amberlyst 35, Amberlyst 15 and Lewatit
SPC112) using 1-octene as alkylating agent under mild reaction
conditions (<383 K) and in toluene excess. Mono- and di-alkylation
products were obtained in different proportions depending on the
resin. Amberlyst 35 showed the highest activity and selectivity in
the formation of mono-alkylated isomers.
2.2. Analysis and procedure
All samples were analyzed by gas chromatography/mass spec-
detector (Agilent 6890 + 5973 GC–MS) was equipped with
a
capillary column (HP 190915-433; 5% phenyl methyl siloxane,
30 m × 250 m × 0.25 m nominal). More detailed information can
be found elsewhere [21].
The reactions were carried out in a 200 mL jacketed batch
reactor at 373 K (Autoclave Engineers). In each experiment, the
autoclave was preloaded with 4 g of dry resin of commercial size
and the calculated amount of toluene. Previously, the resin was
activated by drying at 373 K overnight under vacuum, being the
final content of water less than 3% gwater · g−ca1t (Karl–Fisher titra-
tion). After the system was leak tested with nitrogen at 1 MPa, it was
heated to the required reaction temperature and the stirring speed
was set to 500 rpm to avoid the influence of external mass trans-
fer. To start the experiments, the reactor pressure was lowed to the
atmospheric one and the calculated amount of 1-hexene previously
placed in a calibrated burette was forced into the system by nitro-
gen and then the pressure was readjusted to 2 MPa. After a short
while, the temperature was recovered and that moment was taken
as the starting point of the experiment. The autoclave was equipped
with a sample loop including a sampling valve that injected 0.2 L
of pressurized liquid to the chromatograph. The remaining liquid
into the loop was returned to the reactor by nitrogen which was
then used to clean the loop.
2.3. Calculations
With the aim to make up for the absence of knowledge on
the aromatic alkylation with excess of olefin catalyzed by acidic
macroreticular ion exchange resins, the present paper investigates
the alkylation of toluene with 1-hexene in liquid phase with excess
For each experiment, 1-hexene conversion (X1-hex),
selectivity to mono-alkylated toluene (SMAT), selectivity to
di-alkylated toluene (SDAT), selectivity to tri-alkylated toluene