Chemistry of Materials
Article
filtered, and dried, providing 18.3 g (69%) of the desired ammonium
salt as a white powder.
acidity of these SAPO-42 has not been reported. Moreover,
SAPO-42 materials prepared using the bulky triquad OSDA
were not stable after calcination treatments.12
The spectral data. 1H NMR (DMSO-d6, 300.0 MHz): δH 8.0 (d, J =
9 Hz, 2H, Ar−H), 7.6 (t, J = 9 Hz, 2H, Ar−H), 7.5 (d, J = 9 Hz, 2H,
Ar−H), 5.0 (s, 4H, 2×CH2), and 3.2 (s, 6H, 2×NCH3). 13C NMR
(DMSO-d6, 75.5 MHz): δC 132.1, 128.6, 126.6, 124.9, 124.8, 124.3
(Ar−C), 63.4 (2×CH2), and 51.1 (2×NCH3). Anal. Calcd for
C14H16IN: C, 51.71; H, 4.96; N, 4.31. Found: C, 52.2; H, 5.17; N,
4.35.
In past years, we have worked on the synthesis of small pore
SAPOs with large cavities and controlled silicon distributions as
catalysts for the selective catalytic reduction (SCR) of NOx.13
Particularly, we have shown that the use of bulky self-assembled
aromatic molecules as OSDAs (MTPQ, see Figure 1) has
allowed the efficient synthesis of the small pore SAPO STA-6
with an excellent Si distribution, so the presence of large Si-rich
domains was avoided.14 Having in mind that the pure silica
LTA zeolite was achieved using the same bulky self-assembled
aromatic molecule (MTPQ, see Figure 1), it could be
envisioned that related OSDAs would show adequate proper-
ties to allow the synthesis of the small pore SAPO-42 zeotype
with proper Si distributions.
Herein, we describe the synthesis of SAPO-42 using two
aromatic organic molecules (MTPQ and DDBQ, see Figure 1),
which are able to form soluble dimers in the synthesis media
through π−π interactions. Self-assembled paired MTPQ
molecules allow the synthesis of SAPO-42 only when fluoride
anions are present in the synthesis media, while self-assembled
paired DDQB molecules are able to direct the crystallization of
SAPO-42 only under fluoride-free conditions. We will also
show that the presence of fluoride anions in the synthesized
SAPO-42 zeotypes with LTA structure clearly influences the
framework silicon distribution and, consequently, their acid
properties.
To obtain the hydroxide form of the organic cation, 9 g of the
iodide salt was dissolved in water, and thus, 30 g of resin Dower SBR
was added. The mixture was maintained overnight under stirring, and
after filtration, the hydroxide form of the organic cation was obtained.
4-Methyl-2,3,6,7-tetrahydro-1H,5H-pyrido[3.2.1-ij]quinolinium
(MTPQ). The synthesis of MTPQ has been described previously.4 To
prepare the corresponding hydroxide form of the organic cation, 8.52 g
of the iodide salt was dissolved in water, and 27 g of resin Dower SBR
was added. The mixture was maintained under stirring overnight. The
solution was filtered, and the hydroxide form of the organic cation was
obtained.
2.2. Synthesis of the Silicoaluminophosphate Materials. In a
typical zeotype synthesis procedure, the required amount of
orthophosphoric acid (85 wt %, Aldrich) was added to the aqueous
solution of the hydroxide form of the OSDA. Then, the alumina
source (75 wt %, Condea) was introduced, keeping the gel under
stirring for 5 min. A silica source (Ludox AS40, 40 wt %, Aldrich) was
also introduced into the synthesis gel, leaving the mixture under
stirring for 20 min. If required, HF was finally added to the gel, and the
resultant mixture was stirred for 20 min. The gel was transferred to a
Teflon-lined stainless steel autoclave with a free volume of 3 mL and
heated at the appropriate temperature under static conditions for 5
days. Crystalline products were filtered and washed with abundant
water and dried at 100 °C overnight. The samples were calcined in a
tube furnace following the next temperature program: the samples
were heated at 600 °C using a 1 °C/min ramp under flowing N2. The
temperature was held for 8 h under flowing air, and finally, the samples
were cooled to room temperature under flowing N2.
2. EXPERIMENTAL SECTION
2.1. Synthesis of the Organic Structure Directings Agents
(OSDAs). 2,2-Dimethyl-2,3-dihydro-1H-benzo[de]isoquinoline-2-
ium (DDBQ). A total of 21.7 g (109.6 mmol) of commercial 1,8-
naphthalic anhydride was heated under reflux in an aqueous solution
of N-methylamine (40 wt %) for 72 h. The mixture was cooled at
room temperature, and the white solid obtained was filtered and dried
under a vacuum to give N-methyl-1,8-naphthalimide (23.1 g, 100%).
The spectral data were fully coincident with those described in the
literature.15
2.3. Characterization. Powder X-ray diffraction (PXRD)
measurements were performed with a multisample Philips X’Pert
diffractometer equipped with a graphite monochromator, operating at
45 kV and 40 mA, and usig Cu Kα radiation (λ = 0.1542 nm).
The chemical analyses were carried out in a Varian 715-ES ICP-
Optical Emission spectrometer, after solid dissolution in HNO3/HCl/
HF aqueous solution. The organic content of the as-made materials
was determined by elemental analysis performed with a SCHN
FISONS elemental analyzer. Thermogravimetrical analysis was
performed using a Mettler Toledo thermo-balance.
1H NMR (CDCl3, 300.0 MHz): δH 8.5 (d, J = 9 Hz, 2H, Ar−H), 8.1
(d, J = 9 Hz, 2H, Ar−H), 7.7 (t, J = 9 Hz, 2H, Ar−H), and 3.5 (s, 6H,
2xNCH3). 13C NMR (CDCl3, 75.5 MHz): δC 164.5 (2×CO), 133.9,
131.6, 131.2, 126.9, 122.6 (Ar−C), and 27.0 (NCH3).
Then, 23.4 g (111.0 mmol) of N-methyl-1,8-naphthalimide was
added in small portions to a stirred solution of 14.8 g (388.0 mmol) of
LiAlH4 and 100.0 mL of AlCl3 THF complex (0.5 M in THF; 50.0
mmol) in 600 mL of anhydrous THF, cooled in an ice bath, and
maintained under N2. The mixture was stirred for 30 min at room
temperature before being refluxed for 7 h, and then, it was stirred at
room temperature overnight. The temperature was decreased with an
ice bath, and the excess of LiAlH4 was quenched by the slow addition
of 10 mL of H2O. After 30 min, the formed salts were filtered and
washed with THF and ethyl acetate, providing 14.9 g (73%) of the
desired amine as yellow oil after evaporation under a vacuum. The
spectral data were fully coincident with those described in the
literature.15
The morphology of the samples was studied by scanning electron
microscopy (SEM) using a JEOL JSM-6300 microscope and by field
emission scanning electron microscopy (FESEM) using a ZEISS Ultra-
55 microscope.
MAS NMR spectra were recorded at room temperature with a
Bruker AV 400 spectrometer. 29Si NMR spectra were recorded with a
spinning rate of 5 kHz at 79.459 MHz with a 55° pulse length of 3.5 μs
and repetition time of 180 s. 29Si chemical shift was referenced to
tetramethylsilane. 19F was measured at 376.28 MHz using a Bruker
probe with 2.5-mm-diameter zirconia rotors spinning at 25 kHz. The
19F spectra were collected using pulses of 4.5 μs corresponding to a flip
angle of Π/2 rad and a recycle delay of 100 s to ensure the complete
recovery of the magnetization.
1H NMR (CDCl3, 300.0 MHz): δH 7.7 (d, J = 6 Hz, 2H, Ar−H), 7.4
(t, J = 6 Hz, 2H, Ar−H), 7.2 (d, J = 6 Hz, 2H, Ar−H), 3.9 (s, 4H,
2×CH2), and 2.6 (s, 6H, 2×NCH3). 13C NMR (CDCl3, 75.5 MHz):
δC 133.5, 133.1, 127.9, 126.1, 125.6, 121.9 (Ar−C), 58.7 (2×CH2),
and 45.6 (NCH3).
NH3-TPD experiments were carried out in a Micromeritics 2900
apparatus. A calcined sample (100 mg) was activated by heating to 400
°C for 2 h in an oxygen flow and for 2 h in an argon flow.
Subsequently, the samples were cooled to 176 °C, and NH3 was
adsorbed. The NH3 desorption was monitored with a quadrupole mass
spectrometer (Balzers, Thermo Star GSD 300 T) while the
temperature of the sample was ramped at 10 °C/min under a helium
flow. Total ammonia adsorption was measured by repeated injection of
calibrated amounts of ammonia at 176 °C until saturation. Ammonia
Finally, 50.0 mL (803.2 mmol) of methyl iodide was slowly added
to a solution of 14.9 g (81.4 mmol) of 2-methyl-1,3-dihydrobenz-
[d,e]isoquinoline in 75 mL of MeOH. The mixture was stirred for 1
week, and no precipitate was observed. The solution was concentrated
to dryness, and the resulting solid was washed with acetonitrile,
2982
Chem. Mater. 2015, 27, 2981−2989