R. Pourfaraj et al.
Journal of Solid State Chemistry 265 (2018) 248–256
transition metals in order to oxidation of benzyl alcohol. Moreover, a
comprehensive review of catalytic oxidation of alcohols over the LDHs
as a catalyst or supported catalysts has been reported by Crocker et al.
[21]. Compared with the oxidation of alcohols, there is no report on the
catalytic activity of the LDHs and binary metal hydroxides in N-
formylation of amines. Finally, the calcined and rehydrated Mg-Al
LDHs have been extensively applied as effective solid-base catalysts in
aldol condensations such as the Claisen–Schmidt condensation reac-
tion [22,23]. In the recent years, more attention has been paid to the
catalytic activity of LDHs and binary metal hydroxides containing
strument (BELSORP-mini II, BEL, Japan) at 77 K. The BJH pore size
distributions were determined from the adsorption branch of nitrogen
adsorption–desorption isotherms. The micropore size distributions
were determined by micropore analysis (MP method). The basicity of
catalysts was determined by acid-base titration method [26]. In this
method 100 mg of catalysts were vigorously shaken with 10 ml
deionized water for 24 h in room temperature and catalyst was
separated. Then, filtrate was neutralized with 0.05 M of HCl. The
remaining acid was titrated with 0.1 M of standard NaOH.
2.5. Oxidation of benzyl alcohol
2. Experimental section
Benzyl alcohol (1 mmol), catalyst (10 and 30 mg), and TBHP
(2 mmol; 70% in water) were added into a 50-ml two-neck, round-
bottomed flask equipped with a magnetic stirrer, reflux condenser,
thermometer. The reaction was performed in solvent-free and acetoni-
trile conditions at the temperature of 40 °C for 6 h and monitored by
TLC.
2.1. Materials and instruments
Cobalt (II) nitrate hexahydrate, Nickel (II) nitrate hexahydrate, and
ammonia solution (25%, w/v) were purchased from Chem-Lab
Analytical. Benzyl alcohol was purchased from Scharlau. Aniline,
formic acid, acetophenone, tert-butyl hydrogen peroxide (TBHP),
acetonitrile, and urea were obtained from Merck. All chemicals were
of analytical grade and were used without further purification. Purity of
products was checked by
(Electrothermal model IA9300).
model GC 2014 with a flame ionization detector (FID) and Agilent
HP-5 GC Capillary Column (30 m, 0.25 mm, 0.25 µm) was used to
calculate the reaction selectivity.
2.6. N-formylation of aniline
Aniline (1.5 mmol), formic acid (4.5 mmol) and catalyst (10 and
30 mg) were added into a 10-ml vial and the mixture was stirred at
room temperature for an appropriate amount of time. The reaction was
performed in solvent-free and acetonitrile conditions and monitored by
TLC.
a
digital melting point apparatus
Shimadzu gas chromatograph
A
2.7. Claisen–Schmidt condensation
2.2. Synthesis of α-CoNi binary Hydroxide
Benzaldehyde (1 mmol), catalyst (10 and 30 mg), and acetophenone
(1 mmol) were added into a 25-ml two-neck, round-bottomed flask
equipped with a magnetic stirrer, reflux condenser, thermometer. The
reaction was performed in toluene at 40 °C and 90 °C for 8 h and
monitored by TLC.
A facile hydrothermal route under ambient atmosphere was utilized
for synthesizing the catalysts. In a typical experiment, 2.91 g Co(NO3)2·
6H2O, 2.91 g Ni(NO3)2·6H2O and 0.9 g urea in 70 ml of deionized
water were mixed under vigorous stirring for 20 min. The solution
obtained was transferred into a 120 ml, Teflon-lined, stainless steel
autoclave and then was heated at 150 °C for 10 h. Subsequently, the
autoclave was allowed to cool down naturally to room temperature.
Finally, the precipitation obtained was filtered and washed several
times with deionized water and absolute ethanol and dried in an oven
at 60 °C.
2.8. Catalyst recycling
After the reaction, the catalysts were separated by centrifugation,
washed with water and ethanol and then dried at 60 °C. The recovered
catalysts were reused for the next runs under the same conditions
without further purification.
2.3. Synthesis of β-CoNi binary hydroxide
3. Results and discussion
The catalyst was synthesized in a similar way to the above-
mentioned procedure, except that instead of urea, 10 ml of an aqueous
solution containing 50 mmol of NH3·H2O was dropwisely added. In
this case, a suspension was formed by adding the ammonia solution.
3.1. Characterization of catalysts
The typical XRD pattern of the α-CoNi binary H consists of four
broad peaks appearing at 2θ values of 12.27°, 24.72°, 33.29°, and 59.4°
is shown in Fig. 1a. The diffraction peaks are indexed as (003), (006),
(101), and (110) planes, respectively, suggesting that α-Co(OH)2
(JCPDS No.46-0605) and α-Ni(OH)2 (JCPDS No. 38-0715) with weak
crystallinity were synthesized. No impurities originating from β phases
2.4. Characterization of catalysts
The powder X-ray diffraction (XRD) pattern of catalysts was
obtained by a PW 1800 X-raydiffractometer with Cu Kα radiation
(λ = 1.542 Å) at 40 kV and 30 mA current. The surface morphology and
EDX spectra were recorded, using Tescan Mira 3 field emission
scanning electron microscopy (FE-SEM) equipped with energy dis-
persive X-ray analysis system (Accelerating Voltage: 20.0 kV). Fourier-
transform infrared (FT-IR) absorption spectra were recorded at room
temperature with the KBr pellet technique by a Perkin Elmer Spectrum
One spectrophotometer in the range of 4000–450 cm−1. The thermo-
gravimetric analysis (TGA) of catalysts was carried out through a
BAHR STA 503 thermal analyzer in air atmosphere. UV–vis–diffuse
reflectance spectra of catalysts were performed by a Shimadzu UV Mini
1240 spectrophotometer in the region 200–800 nm at room tempera-
ture. The textural properties including BET specific surface area, total
pore volume, and average pore volume were calculated from the
nitrogen adsorption–desorption measurements using BELSORP in-
Fig. 1. XRD patterns of (a) α- and (b) β-CoNi binary Hs.
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