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RSC Advances
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DOI: 10.1039/C6RA16093J
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ARTICLE
was added with stirring followed by solvent evaporation at 90 mixture of freshly prepared 10 % ascorbic acid : 0.004 M
°C. It was then dried at 120 °C for 4 h and calcined initially at antimony potassium tartrate solution) was added to get
330 °C for 3 h and then at 560 °C for 10 h. To remove water intense blue color. After 10 min, optical density (OD) was
soluble phosphates, the calcined sample was cooled to room measured at 890 nm in Perkin Elmer UV-Vis
temperature and stirred in water at 80 °C for 12 h (mentioned spectrophotometer. Similar method was followed to make
as water treatment), then filtered, dried and calcined at 500 °C NH4H2PO4 standard solutions and phosphorus was estimated in
for 4 h.18
the catalyst samples using 5 point calibration curve obtained
from standard solutions. Morphology of the catalysts were
studied with FESEM. In a typical procedure, a small amount of
catalyst was smeared on carbon tape glued to the stage,
Catalyst characterization
X-ray diffraction studies were performed with Bruker D2 degassed in vacuum for 24 h, sputtered with gold for 1 min
Phaser diffractometer equipped with Cu Kα source. X-ray and image was collected in Zeiss instrument with different
diffraction data collected was from 5 to 50° Bragg angle with magnifications.
steps of 0.02 with an interval of 0.5 sec. Framework FTIR was
measured by KBR wafer technique. About 0.5 mg of zeolite Catalyst evaluation: acylation of 2-methoxynaphthalene
was thoroughly mixed with 500 mg of KBR and pressed into a
transparent pellet. Data was collected as an average of 32
In a typical experimental procedure, 5 mmol of 2-
scans with 4 cm-1 resolution. Pyridine FTIR was measured by methoxynaphthalene (2MN), 5 mmol of acetic anhydride
adsorbing pyridine on self-supporting wafers. In a typical ((Ac)2O) were taken in a 2-necked glass reactor along with 3 g
procedure, about 30 mg of catalyst was pressed in a hydraulic of chlorobenzene as a solvent and 1 mmol of nitrobenzene as
press to get self-supporting wafers. These wafers were internal standard. To this solution, 400 mg of catalyst pre-
calcined at 550 °C for 2 h and cooled in a desiccator. Pyridine activated at 500 °C was added. Glass reactor was fitted with a
drops were placed on wafer in a perfectly ventilated fume condenser and whole setup was evacuated and maintained
hood. After evaporation of added pyridine in fume hood, with nitrogen blanket throughout the reaction time to avoid
wafers were placed in an oven for 30 min maintained at 200 °C the decomposition of acetic anhydride by moisture. Reaction
to remove all physisorbed pyridine. Data was collected as an was carried out at 130 °C for catalyst screening. After 6 h of
average of 32 scans with 4 cm-1 resolution. Nitrogen sorption reaction time, reaction mixture was cooled to room
measurements were carried out over Autosorb-1C temperature and 10 g of ethanol as diluent was added. This
(Quantachrome, USA) unit. The isotherms were measured at mixture was analyzed by gas chromatograph equipped with
77 K after degassing samples below 10-3 torr at 300 °C for 4 h. FID detector and RTX-5 capillary column. Products were
The BET specific surface area was estimated using adsorption identified by GCMS and quantified by internal standard
data as per the ASTM method 4365 applicable for microporous method using software provided with gas chromatograph.
solids. The total pore volume was estimated from the amount Yield (wt%) was calculated by the formula
adsorbed at a relative pressure of about 0.95. The acidity of
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the catalysts was measured by temperature programmed
desorption (TPD) of NH3. In a typical procedure, 0.1 g of
sample was taken in a quartz tube of ¼ inch packed with silica
wool from both sides to remove dead volume and sample was
dehydrated at 550 °C for 1 h. The temperature was decreased
to 100 °C and NH3 was adsorbed by passing a stream of 10%
NH3 in He through catalyst for 1 h. Physisorbed NH3 was then
purged by dry He for another 1 h. The desorption of NH3 was
carried out in He flow (30 ml min−1) by increasing the
temperature to 550 °C at 10 °C min−1 using TCD detector. Solid
state nuclear magnetic resonance with magic angle spinning
(MAS NMR) was performed in VARIAN Mercury Plus 300MHz
using standard procedure. Sample was placed in a 5 mm probe
and was spun at 5 KHz. Chemical shifts were plotted with
respect to reference standards, NH4H2PO4 and Al(NO3)3 for 31P
and 27Al nuclei respectively. Phosphorus content in the
modified catalyst was estimated by colorimetry.[18] In a typical
procedure, catalyst was digested with a mixture of 1 g of HCl,
0.5 g HF and 1 g HNO3. The mixture was then neutralized with
H3BO3 and this mixture was diluted to 200 ml. 2 ml of this
solution was taken in 50 ml volumetric flask and 5 ml of 2M
H2SO4 was added followed by 5 ml of 0.01 M ammonium
paramolybdate. To this solution, 4 ml of mixed reagent (1 : 1
100
Acknowledgements
Janardhan L. Hodala acknowledges AMEF Bangalore for a
fellowship and Manipal University for permitting this research
as a part of the PhD programme. Authors gratefully thank
Sophisticated Instrument Facility, IIT Mumbai for collecting
MAS NMR experimental data and Centre for Nanoscience and
Engineering, IISc, Bangalore for SEM images.
References
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Hodala, Janardhan L.
