S. Ghosh et al.
Catalysis Today xxx (xxxx) xxx–xxx
the esterification of biomass derived LA with EtOH. EL has received a
huge attention because it can be utilized up to 5 wt% as an additive to
diesel and can be blended with most of the petroleum-based fuels
[
41–44].
In this context it is pertinent to mention that phosphate-based
porous nanomaterials are largely explored in lithium-ion batteries [45],
ion-exchange [46], proton conducting material [47] etc. Whereas, there
are only few reports on the catalytic potential of these materials [48].
For designing a suitable phosphate based material as heterogeneous
catalyst controlled synthesis of tiny metal phosphonate particles with
uniform morphology, considerably good dispersion of active metal
centres and large micropores together with high BET surface area are
required. Due to the presence of abundant surface phosphonate groups
in the metal-phosphonate synthesized from a multidentate phosphonate
precursor it may offer good catalytic activity for a wide range of solid
acid catalyzed reactions. Thus, here we have synthesized Fe-phospho-
nate nanomaterials HPFP-1(NP) through the chemical reaction of hex-
amethylenediamine-N,N,N′,N′-tetrakis-(methylphosphonic acid) and
Scheme 1. Schematic representation of the synthesis of HPFP-1(NP) nanomaterial.
aqueous solution of FeCl
its catalytic potential in the CO
3
under hydrothermal conditions and explored
fixation to epoxide and esterification of
2
yellowish precipitate after pouring the solution of HDTMP. In a re-
presentative synthesis, a 25% aqueous solution of HDTMP (5.1 g,
.5 mmol) was added slowly in an aqueous FeCl (10 mmol, 1.64 g)
3
levulinic acid. The HPFP-1(NP) nanoparticles showed very good cata-
lytic activity for the production of organic cyclic carbonates from a
wide range of epoxides in the presence of CO under atmospheric
2
2
solution. Then the mixture was vigorously stirred with a magnetic
stirrer for 30–40 min and treated under the hydrothermal conditions in
a Teflon steel-lined autoclave. After the hydrothermal treatment for
pressure maintaining eco-friendly reaction conditions. This nanocata-
lyst also exhibited excellent catalytic activity for the conversion of le-
vulinic acid into alkyl levulinates under mild reaction conditions.
24 h at 423 K finally we got the porous iron-phosphonate nanomaterial
HPFP-1(NP).
2
. Experimental section
.1. Materials
FeCl was procured from E-Merck. Hexamethylenediamine-
2
2.4. Typical procedure for synthesis of cyclic carbonates at 1 atmospheric
pressure of CO
2
3
N,N,N′,N′-tetrakis-(methylphosphonic acid) HDTMP and levulinic acid
was purchased from Sigma-Aldrich. All epoxides and amines were also
bought from Sigma-Aldrich. All solvents and reagents were distilled
through standard process and dried up.
Catalyst HPFP-1(NP) (50 mg), Bu NBr (26.7 mg, 0.083 mmol) and
styrene oxide (5 mmol) were placed in a 100 mL round bottom flask
fitted with a magnetic stirrer. The flask was fitted with a stopper of
4
2
rubber pierced by a CO containing balloon under 1 atmosphere. The
solution of reaction mixture was stirred at room temperature for 12 h.
The conversion of epoxide to the respective cyclic five-membered car-
bonate was monitored from the 1H NMR data. The products were iso-
lated through column chromatography. All products were characterized
from their respective spectroscopic data ( H NMR) and identified
through the comparison with those reported in the literature.
2
.2. Characterization techniques
Transmission electron microscopy (TEM) images of the nanoma-
1
terials were obtained with the help of a JEOL JEM 2010 transmission
electron microscope operating at 200 kV. Powder X-ray diffraction
(
PXRD) patterns of the HPFP-1(NP) material was analyzed by using a
Bruker D8 Advance X-ray diffractometer using the Ni-filtered Cu Kα
λ = 0.15406 nm) radiation. Using a Perkin-Elmer FT-IR 783 spectro-
2.5. General procedure for synthesis alkyl levulinates from levulinic acid
(
photometer the FT-IR spectra of the samples were recorded on KBr
pellets. UV–vis spectra of the solid samples were taken using a
Shimadzu UV-2401 PC doubled beam spectrophotometer having an
integrating sphere attachment. Scanning electron microscopy (SEM)
measurements of the nanomaterials were performed with a JEOL JEM
Esterification of levulinic acid was carried out in a 50 mL round
bottom flask equipped with a reflux condenser. In a typical catalytic
reaction the catalyst (40 mg) was added to a mixture of levulinic acid
and ethanol with the molar ratio of LA: alcohol = 1:8 (ethanol acts as
reagent cum solvent) and the mixture was magnetically stirred at 333 K
for 2 h. A portion of the reaction mixture was separated after the
scheduled reaction time through filtration and the filtrate was then
analyzed through the gas chromatography (GC) equipped with a flame-
ionized detector and a capillary column. All compounds were char-
6700F field-emission scanning electron microscope. Thermogravimetric
analysis (TGA) of the material was performed by using Mettler-Toledo
TGA-DTA 851e. After completion of the reactions, the reaction products
were analyzed through a Varian 3400 gas chromatograph equipped
with a 30 m CP-SIL 8CB capillary column and a flame ionization de-
tector. The products were identified by Trace DSQ II GC–MS equipped
1
acterized on the basis of their spectroscopic data ( H NMR) and by
comparison with those reported in the literature.
1
with a 60 m TR-50MS capillary column. H NMR spectra were recorded
on a Bruker DPX-200, DPX-300, DPX-400 and DPX-500 instruments.
3. Results and discussion
2.3. Synthesis of iron phosphonate nanomaterial
3.1. Characterization of HPFP-1(NP) material
The outline for the synthesis of HPFP-1(NP) nanomaterial is shown
3.1.1. Powder X-ray diffraction (PXRD) and nanostructure analysis
The powder X-ray diffraction pattern of as-synthesized organic-in-
organic hybrid iron phosphonate material HPFP-1(NP) using 4:1 molar
ratio of Fe(III) to HDTMP in the synthesis gel is shown in Fig. 1. As
noticed from the Figure there is only two noticeable diffraction peaks,
in Scheme 1. We have synthesized three HPFP-1 samples using FeCl
hexamethylenediamine-N,N,N′,N′-tetrakis-(methylphosphonic acid)
HDTMP) molar ratios of 4:1, 6:1 and 2:1. In a typical synthesis HDTMP
3
to
(
was poured into aqueous FeCl
3
solution. We had obtained a pale
2