The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%... more The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%) and o-H 3 PO 4 (30 ml, 85% Aldrich) was refluxed in deionised water (120 ml) for 24 h. The yellow solid was recovered by vacuum filtration, washed with cold water (100 ml) and acetone (100 ml) and dried in air (110 o C, 24 h). Powder X-ray diffraction studies confirmed that the solid was the dihydrate, VOPO 4 .2H 2 O 1. The dihydrate (4 g) was refluxed with isobutanol (80 ml, 99%, Spectrochem) for 21 h, and the resulting hemi hydrate was recovered by filtration, dried in air (110 o C, 16 h), refluxed in deionised water (9 ml H 2 O/solid(g)) for 2 h, filtered hot, and dried in air (110 o C, 16 h).
VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. He... more VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. Herein we explored its catalytic activity towards decolourisation/degradation of organic pollutants. This investigation reports the remarkable photo catalytic activity of tungstate promoted vanadium phosphate (WO 3-VPO) toward photocatalyic decolourisation/degradation of pollutants. The catalyst i.e. 10 wt% WO 3-VPO showed unexpected efficacy i.e. 100% decolourisation of Rhodamine B (RhB) and 60% degradation of phenol under visible light irradiation with a short span of time i.e. 10 min. Several factors involving the significant results of the composite material than the neat sample have been studied in detail. The analysis of photoluminescence (PL) emission spectra, photoelectrochemical measurement and the cyclic voltammeter (CV) measurement of the composite materials greatly support the outstanding results of the catalyst. The remarkable efficiency of VPO materials in photocatalytic decolourisation/degradation would become another trademark in the photocatalysis society.
ABSTRACT AbstractThis paper reports the facile synthesis of vanadium phosphate (VPO) by the decom... more ABSTRACT AbstractThis paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition of VOHPO4·0.5H2O which was prepared by reduction of dihydrate VOPO4·2H2O with isobutanol. The material was promoted with aluminum by impregnation method. The catalysts were unambiguously characterized by N2 adsorption–desorption, XRD, FT-IR techniques, UV–Vis DRS and the total amount of the acidity of the catalysts was estimated by NH3-TPD. The catalytic activities were checked in the heterogeneous catalytic esterification of acetic acid with 1° alcohol (n-butanol) in a solvent free medium. The optimization of reaction was carried out by varying temperature from 75 to 150°C, molar ratio (butanol:acetic acid) from 1:1 to 1:4. Under optimum conditions, the catalytic esterification runs revealed a significant effect of the VPO giving 62% conversion with 100% selectivity to butyl acetate. Graphical AbstractVanadium Phosphate is prepared in aqueous medium by taking vanadium pentoxide, o-phosphoric acid and isobutanol. The catalyst is found to be robust enough to achieve high degree of esterification under solvent free condition. KeywordsEsterification-Vanadium phosphate-Acetic acid- n-Butyl acetate
ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of ca... more ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of carbohydrates to fine chemicals. Herein we describe a catalytic protocol for the synthesis of 5-hydroxymethylfurfural (HMF) from glucose over a Sn-VPO catalyst. The reaction proceeds through two steps involving the isomerization of glucose to fructose and the dehydration of fructose to HMF. The catalysts were unambiguously characterized by various spectral techniques. The presence of both Lewis and Bronsted acid sites in Sn-VPO plays a crucial role in this conversion. The former acid isomerizes glucose to fructose and the latter dehydrates the fructose to HMF. The reaction has been studied by varying various reaction parameters. Under optimum conditions the 20 wt% Sn-VPO exhibits excellent results (73.79% yield). The catalyst can easily be recovered by filtration and reused several times without any appreciable change to its catalytic activity.
VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. He... more VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. Herein we explored its catalytic activity towards decolourisation/degradation of organic pollutants. This investigation reports the remarkable photo catalytic activity of tungstate promoted vanadium phosphate (WO 3-VPO) toward photocatalyic decolourisation/degradation of pollutants. The catalyst i.e. 10 wt% WO 3-VPO showed unexpected efficacy i.e. 100% decolourisation of Rhodamine B (RhB) and 60% degradation of phenol under visible light irradiation with a short span of time i.e. 10 min. Several factors involving the significant results of the composite material than the neat sample have been studied in detail. The analysis of photoluminescence (PL) emission spectra, photoelectrochemical measurement and the cyclic voltammeter (CV) measurement of the composite materials greatly support the outstanding results of the catalyst. The remarkable efficiency of VPO materials in photocatalytic decolourisation/degradation would become another trademark in the photocatalysis society.
ABSTRACT Formaldehyde is an important intermediate in the pharmaceutical, plastic and automobile ... more ABSTRACT Formaldehyde is an important intermediate in the pharmaceutical, plastic and automobile industries which is produced commercially via methanol oxidation. A series of tungstate promoted vanadium phosphate catalysts were prepared and characterised using a combination of XRD, UV-vis spectrometry, XPS and ammonia TPD. The 25 wt% WO3–VPO catalyst exhibited good activity for the selective gas phase oxidation of methanol with >90% conversion at around 250 °C. This is a considerably lower temperature than used in the current industrial process using either silver or iron molybdate catalysts. This increased activity at low temperatures is ascribed to the increase in Brønsted acidity and redox properties of the tungstate doped materials.
The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%... more The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%) and o-H 3 PO 4 (30 ml, 85% Aldrich) was refluxed in deionised water (120 ml) for 24 h. The yellow solid was recovered by vacuum filtration, washed with cold water (100 ml) and acetone (100 ml) and dried in air (110 o C, 24 h). Powder X-ray diffraction studies confirmed that the solid was the dihydrate, VOPO 4 .2H 2 O 1. The dihydrate (4 g) was refluxed with isobutanol (80 ml, 99%, Spectrochem) for 21 h, and the resulting hemi hydrate was recovered by filtration, dried in air (110 o C, 16 h), refluxed in deionised water (9 ml H 2 O/solid(g)) for 2 h, filtered hot, and dried in air (110 o C, 16 h).
ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of ca... more ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of carbohydrates to fine chemicals. Herein we describe a catalytic protocol for the synthesis of 5-hydroxymethylfurfural (HMF) from glucose over a Sn-VPO catalyst. The reaction proceeds through two steps involving the isomerization of glucose to fructose and the dehydration of fructose to HMF. The catalysts were unambiguously characterized by various spectral techniques. The presence of both Lewis and Bronsted acid sites in Sn-VPO plays a crucial role in this conversion. The former acid isomerizes glucose to fructose and the latter dehydrates the fructose to HMF. The reaction has been studied by varying various reaction parameters. Under optimum conditions the 20 wt% Sn-VPO exhibits excellent results (73.79% yield). The catalyst can easily be recovered by filtration and reused several times without any appreciable change to its catalytic activity.
Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To... more Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To date, there has been little interest in carrying out liquid-phase reactions with vanadium phosphate as catalyst. Herein, we report the catalytic activity of vanadium phosphate and aluminum-promoted vanadium phosphate toward liquid-phase isopropylation of toluene to cymene. The catalysts were unambiguously characterized by X-ray diffraction, N2 adsorption–desorption, FT-IR technique, UV–vis DRS, and FE-SEM. ...
A novel solid acid catalyst has been extensively used for the esterification reaction. Herein, tu... more A novel solid acid catalyst has been extensively used for the esterification reaction. Herein, tungstate promoted vanadium phosphate material is fabricated from its precursor, VOHPO(4)·0.5H(2)O and its catalytic activities and structure are investigated in detail. This kind of catalyst is, for the first time, applied for the effective production of biodiesel from fatty acids. Although vanadium phosphate has been extensively used in gas phase oxidation reactions, it has not drawn much attention for its application in liquid phase reactions. Our recent results indicate that vanadium phosphate is an effective, minimally polluting and re-usable catalyst that is highly suited to the production of biodiesel from fatty acids. This work extends the possibility of using VPO in other liquid phase reactions.
Vanadium phosphate (VPO) is an interesting catalytic material because of its ability to catalyze ... more Vanadium phosphate (VPO) is an interesting catalytic material because of its ability to catalyze reactions, such as partial oxidations with high selectivity. Selective gas phase oxidation of methanol to formaldehyde is achieved over simple aluminum promoted vanadium phosphate (Al-VPO) impregnated heterogeneous catalyst. A series of Al-VPO (3, 5, 10, 15 and 20 wt%) catalysts have been synthesized and the catalytic behavior has been studied by carrying out methanol oxidation. The catalytic oxidation runs revealed a significant effect of the vanadium phosphate giving 100% selectivity to formaldehyde at 200 • C. The conversion can be enhanced to 94% with the sacrifice of the selectivity.
This article describes our efforts in developing molybdenum promoted vanadium phosphate (Mo-VPO) ... more This article describes our efforts in developing molybdenum promoted vanadium phosphate (Mo-VPO) catalyst by two distinct methods and its application in liquid phase oxidation reactions. The materials were characterized by various spectral techniques and their catalytic potential has been investigated for the oxidation of cyclohexene. The influences of various reaction parameters have also been studied. Under optimum reaction conditions excellent to higher yield of epoxide (91%) was obtained by Mo-VPO* prepared by impregnation method. The promoting effect of Mo on VPO solids was found to be a function of the way the ion was added during the preparation of the VOHPO 4 •0.5H 2 O phase. XPS analysis of the catalysts showed the presence of couple V 4+ /V 5+ on the surface of Mo-VPO which facilitates the reaction. The catalyst showed its recapability more than four times without any appreciable change in conversion and selectivity. The synergetic effect between Mo and V, to the contrary, made the active phase, VPO, more stable.
A series of tungstate promoted β-SiC catalysts was synthesized by a wetness impregnation method. ... more A series of tungstate promoted β-SiC catalysts was synthesized by a wetness impregnation method. The as synthesized catalysts were unambiguously characterized by XRD, Raman, FTIR, XPS, UV-Vis DRS, TEM, BET surface areas and FE-SEM, and simultaneously the total amount of the acidity of the catalysts was estimated by NH(3)-TPD. The catalytic activities of the synthesized materials were tested in the liquid phase esterification of acetic acid with n-butanol in a solvent free medium. The reaction parameters were optimized to a temperature of 120 °C, molar ratio of butanol and acetic acid of 1:2 and a reaction time of 6 h after performing a number of experiments. Under the optimum conditions, the catalytic esterification revealed a significant effect of 88% conversion with 100% selectivity to butyl acetate in 20 wt% WO(3)/β-SiC. This is the first report on the effective utilization of β-SiC as a catalyst support for liquid phase esterification of acetic acid.
Composite materials have revealed remarkable activities in various catalytic applications. Howeve... more Composite materials have revealed remarkable activities in various catalytic applications. However, choosing an appropriate material to enhance the catalytic activity and stability is a major challenge in the field of catalysis. In this article, we reported vanadium phosphorus oxide (VPO)/β-SiC as a stable composite material with good catalytic activity. VPO/β-SiC composite materials with different compositions were fabricated by the impregnation technique to investigate the catalytic activity and stability of these materials in liquid-phase reactions. The physiochemical characteristics of the prepared catalysts were analyzed by several spectroscopic methods. The catalytic activities of VPO/β-SiC composites were studied in a solvent-free oxidation of methanol using tert-butyl hydroperoxide (TBHP) as an oxidant. The reaction conditions were optimized by changing various reaction parameters. Under optimized reaction conditions, the 10 wt % VPO/β-SiC composite showed 100% conversion with 89.8% selectivity to formaldehyde.
Vanadium phosphate (VPO) is well known as a heterogeneous catalyst in gas phase oxidation reactio... more Vanadium phosphate (VPO) is well known as a heterogeneous catalyst in gas phase oxidation reactions. Till date, this material has not drawn much attention for its application in liquid phase reactions. This paper briefly highlights our recent research on vanadyl metaphosphate concerning its fabrication, characterization and application towards liquid phase oxidation of benzyl alcohol to benzaldehyde using tert-butyl hydroperoxide (TBHP) as the oxidant. In our preliminary catalytic studies, we find that the VO(PO 3) 2 exhibits extraordinarily high activity and selectivity in oxidation of benzyl alcohol under mild conditions. The benzyl alcohol conversion is largely increased but the selectivity for benzaldehyde is slightly decreased with the increase in reaction period or temperature. The present catalyst VO(PO 3) 2 showed remarkable catalytic activity with respect to other catalytic system; conversion and selectivity with respect to aldehyde is 97 and 99%, respectively.
Abstract This paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition... more Abstract This paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition of VOHPO4·0.5H2O which was prepared by reduction of dihydrate VOPO4·2H2O with isobutanol. The material was promoted with aluminum by impregnation method. The catalysts were unambiguously characterized by N2 adsorption–desorption, XRD, FT-IR techniques, UV–Vis DRS and the total amount of the acidity of the catalysts was estimated by NH3-TPD. The catalytic activities were checked in the heterogeneous catalytic esterification of acetic acid with 1° alcohol (n-butanol) in a solvent free medium. The optimization of reaction was carried out by varying temperature from 75 to 150 °C, molar ratio (butanol:acetic acid) from 1:1 to 1:4. Under optimum conditions, the catalytic esterification runs revealed a significant effect of the VPO giving 62% conversion with 100% selectivity to butyl acetate. Graphical Abstract Vanadium Phosphate is prepared in aqueous medium by taking vanadium pentoxide, o-phosphoric acid and isobutanol. The catalyst is found to be robust enough to achieve high degree of esterification under solvent free condition.
The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%... more The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%) and o-H 3 PO 4 (30 ml, 85% Aldrich) was refluxed in deionised water (120 ml) for 24 h. The yellow solid was recovered by vacuum filtration, washed with cold water (100 ml) and acetone (100 ml) and dried in air (110 o C, 24 h). Powder X-ray diffraction studies confirmed that the solid was the dihydrate, VOPO 4 .2H 2 O 1. The dihydrate (4 g) was refluxed with isobutanol (80 ml, 99%, Spectrochem) for 21 h, and the resulting hemi hydrate was recovered by filtration, dried in air (110 o C, 16 h), refluxed in deionised water (9 ml H 2 O/solid(g)) for 2 h, filtered hot, and dried in air (110 o C, 16 h).
VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. He... more VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. Herein we explored its catalytic activity towards decolourisation/degradation of organic pollutants. This investigation reports the remarkable photo catalytic activity of tungstate promoted vanadium phosphate (WO 3-VPO) toward photocatalyic decolourisation/degradation of pollutants. The catalyst i.e. 10 wt% WO 3-VPO showed unexpected efficacy i.e. 100% decolourisation of Rhodamine B (RhB) and 60% degradation of phenol under visible light irradiation with a short span of time i.e. 10 min. Several factors involving the significant results of the composite material than the neat sample have been studied in detail. The analysis of photoluminescence (PL) emission spectra, photoelectrochemical measurement and the cyclic voltammeter (CV) measurement of the composite materials greatly support the outstanding results of the catalyst. The remarkable efficiency of VPO materials in photocatalytic decolourisation/degradation would become another trademark in the photocatalysis society.
ABSTRACT AbstractThis paper reports the facile synthesis of vanadium phosphate (VPO) by the decom... more ABSTRACT AbstractThis paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition of VOHPO4·0.5H2O which was prepared by reduction of dihydrate VOPO4·2H2O with isobutanol. The material was promoted with aluminum by impregnation method. The catalysts were unambiguously characterized by N2 adsorption–desorption, XRD, FT-IR techniques, UV–Vis DRS and the total amount of the acidity of the catalysts was estimated by NH3-TPD. The catalytic activities were checked in the heterogeneous catalytic esterification of acetic acid with 1° alcohol (n-butanol) in a solvent free medium. The optimization of reaction was carried out by varying temperature from 75 to 150°C, molar ratio (butanol:acetic acid) from 1:1 to 1:4. Under optimum conditions, the catalytic esterification runs revealed a significant effect of the VPO giving 62% conversion with 100% selectivity to butyl acetate. Graphical AbstractVanadium Phosphate is prepared in aqueous medium by taking vanadium pentoxide, o-phosphoric acid and isobutanol. The catalyst is found to be robust enough to achieve high degree of esterification under solvent free condition. KeywordsEsterification-Vanadium phosphate-Acetic acid- n-Butyl acetate
ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of ca... more ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of carbohydrates to fine chemicals. Herein we describe a catalytic protocol for the synthesis of 5-hydroxymethylfurfural (HMF) from glucose over a Sn-VPO catalyst. The reaction proceeds through two steps involving the isomerization of glucose to fructose and the dehydration of fructose to HMF. The catalysts were unambiguously characterized by various spectral techniques. The presence of both Lewis and Bronsted acid sites in Sn-VPO plays a crucial role in this conversion. The former acid isomerizes glucose to fructose and the latter dehydrates the fructose to HMF. The reaction has been studied by varying various reaction parameters. Under optimum conditions the 20 wt% Sn-VPO exhibits excellent results (73.79% yield). The catalyst can easily be recovered by filtration and reused several times without any appreciable change to its catalytic activity.
VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. He... more VPO materials are extensively used the in gas phase oxidation of n-butane to maleic anhydride. Herein we explored its catalytic activity towards decolourisation/degradation of organic pollutants. This investigation reports the remarkable photo catalytic activity of tungstate promoted vanadium phosphate (WO 3-VPO) toward photocatalyic decolourisation/degradation of pollutants. The catalyst i.e. 10 wt% WO 3-VPO showed unexpected efficacy i.e. 100% decolourisation of Rhodamine B (RhB) and 60% degradation of phenol under visible light irradiation with a short span of time i.e. 10 min. Several factors involving the significant results of the composite material than the neat sample have been studied in detail. The analysis of photoluminescence (PL) emission spectra, photoelectrochemical measurement and the cyclic voltammeter (CV) measurement of the composite materials greatly support the outstanding results of the catalyst. The remarkable efficiency of VPO materials in photocatalytic decolourisation/degradation would become another trademark in the photocatalysis society.
ABSTRACT Formaldehyde is an important intermediate in the pharmaceutical, plastic and automobile ... more ABSTRACT Formaldehyde is an important intermediate in the pharmaceutical, plastic and automobile industries which is produced commercially via methanol oxidation. A series of tungstate promoted vanadium phosphate catalysts were prepared and characterised using a combination of XRD, UV-vis spectrometry, XPS and ammonia TPD. The 25 wt% WO3–VPO catalyst exhibited good activity for the selective gas phase oxidation of methanol with >90% conversion at around 250 °C. This is a considerably lower temperature than used in the current industrial process using either silver or iron molybdate catalysts. This increased activity at low temperatures is ascribed to the increase in Brønsted acidity and redox properties of the tungstate doped materials.
The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%... more The VPO precursor was prepared according to the procedure as follows: V 2 O 5 (5.0 g, SBMC, 98.5%) and o-H 3 PO 4 (30 ml, 85% Aldrich) was refluxed in deionised water (120 ml) for 24 h. The yellow solid was recovered by vacuum filtration, washed with cold water (100 ml) and acetone (100 ml) and dried in air (110 o C, 24 h). Powder X-ray diffraction studies confirmed that the solid was the dihydrate, VOPO 4 .2H 2 O 1. The dihydrate (4 g) was refluxed with isobutanol (80 ml, 99%, Spectrochem) for 21 h, and the resulting hemi hydrate was recovered by filtration, dried in air (110 o C, 16 h), refluxed in deionised water (9 ml H 2 O/solid(g)) for 2 h, filtered hot, and dried in air (110 o C, 16 h).
ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of ca... more ABSTRACT There are very few heterogeneous catalysts which have been used for the conversion of carbohydrates to fine chemicals. Herein we describe a catalytic protocol for the synthesis of 5-hydroxymethylfurfural (HMF) from glucose over a Sn-VPO catalyst. The reaction proceeds through two steps involving the isomerization of glucose to fructose and the dehydration of fructose to HMF. The catalysts were unambiguously characterized by various spectral techniques. The presence of both Lewis and Bronsted acid sites in Sn-VPO plays a crucial role in this conversion. The former acid isomerizes glucose to fructose and the latter dehydrates the fructose to HMF. The reaction has been studied by varying various reaction parameters. Under optimum conditions the 20 wt% Sn-VPO exhibits excellent results (73.79% yield). The catalyst can easily be recovered by filtration and reused several times without any appreciable change to its catalytic activity.
Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To... more Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To date, there has been little interest in carrying out liquid-phase reactions with vanadium phosphate as catalyst. Herein, we report the catalytic activity of vanadium phosphate and aluminum-promoted vanadium phosphate toward liquid-phase isopropylation of toluene to cymene. The catalysts were unambiguously characterized by X-ray diffraction, N2 adsorption–desorption, FT-IR technique, UV–vis DRS, and FE-SEM. ...
A novel solid acid catalyst has been extensively used for the esterification reaction. Herein, tu... more A novel solid acid catalyst has been extensively used for the esterification reaction. Herein, tungstate promoted vanadium phosphate material is fabricated from its precursor, VOHPO(4)·0.5H(2)O and its catalytic activities and structure are investigated in detail. This kind of catalyst is, for the first time, applied for the effective production of biodiesel from fatty acids. Although vanadium phosphate has been extensively used in gas phase oxidation reactions, it has not drawn much attention for its application in liquid phase reactions. Our recent results indicate that vanadium phosphate is an effective, minimally polluting and re-usable catalyst that is highly suited to the production of biodiesel from fatty acids. This work extends the possibility of using VPO in other liquid phase reactions.
Vanadium phosphate (VPO) is an interesting catalytic material because of its ability to catalyze ... more Vanadium phosphate (VPO) is an interesting catalytic material because of its ability to catalyze reactions, such as partial oxidations with high selectivity. Selective gas phase oxidation of methanol to formaldehyde is achieved over simple aluminum promoted vanadium phosphate (Al-VPO) impregnated heterogeneous catalyst. A series of Al-VPO (3, 5, 10, 15 and 20 wt%) catalysts have been synthesized and the catalytic behavior has been studied by carrying out methanol oxidation. The catalytic oxidation runs revealed a significant effect of the vanadium phosphate giving 100% selectivity to formaldehyde at 200 • C. The conversion can be enhanced to 94% with the sacrifice of the selectivity.
This article describes our efforts in developing molybdenum promoted vanadium phosphate (Mo-VPO) ... more This article describes our efforts in developing molybdenum promoted vanadium phosphate (Mo-VPO) catalyst by two distinct methods and its application in liquid phase oxidation reactions. The materials were characterized by various spectral techniques and their catalytic potential has been investigated for the oxidation of cyclohexene. The influences of various reaction parameters have also been studied. Under optimum reaction conditions excellent to higher yield of epoxide (91%) was obtained by Mo-VPO* prepared by impregnation method. The promoting effect of Mo on VPO solids was found to be a function of the way the ion was added during the preparation of the VOHPO 4 •0.5H 2 O phase. XPS analysis of the catalysts showed the presence of couple V 4+ /V 5+ on the surface of Mo-VPO which facilitates the reaction. The catalyst showed its recapability more than four times without any appreciable change in conversion and selectivity. The synergetic effect between Mo and V, to the contrary, made the active phase, VPO, more stable.
A series of tungstate promoted β-SiC catalysts was synthesized by a wetness impregnation method. ... more A series of tungstate promoted β-SiC catalysts was synthesized by a wetness impregnation method. The as synthesized catalysts were unambiguously characterized by XRD, Raman, FTIR, XPS, UV-Vis DRS, TEM, BET surface areas and FE-SEM, and simultaneously the total amount of the acidity of the catalysts was estimated by NH(3)-TPD. The catalytic activities of the synthesized materials were tested in the liquid phase esterification of acetic acid with n-butanol in a solvent free medium. The reaction parameters were optimized to a temperature of 120 °C, molar ratio of butanol and acetic acid of 1:2 and a reaction time of 6 h after performing a number of experiments. Under the optimum conditions, the catalytic esterification revealed a significant effect of 88% conversion with 100% selectivity to butyl acetate in 20 wt% WO(3)/β-SiC. This is the first report on the effective utilization of β-SiC as a catalyst support for liquid phase esterification of acetic acid.
Composite materials have revealed remarkable activities in various catalytic applications. Howeve... more Composite materials have revealed remarkable activities in various catalytic applications. However, choosing an appropriate material to enhance the catalytic activity and stability is a major challenge in the field of catalysis. In this article, we reported vanadium phosphorus oxide (VPO)/β-SiC as a stable composite material with good catalytic activity. VPO/β-SiC composite materials with different compositions were fabricated by the impregnation technique to investigate the catalytic activity and stability of these materials in liquid-phase reactions. The physiochemical characteristics of the prepared catalysts were analyzed by several spectroscopic methods. The catalytic activities of VPO/β-SiC composites were studied in a solvent-free oxidation of methanol using tert-butyl hydroperoxide (TBHP) as an oxidant. The reaction conditions were optimized by changing various reaction parameters. Under optimized reaction conditions, the 10 wt % VPO/β-SiC composite showed 100% conversion with 89.8% selectivity to formaldehyde.
Vanadium phosphate (VPO) is well known as a heterogeneous catalyst in gas phase oxidation reactio... more Vanadium phosphate (VPO) is well known as a heterogeneous catalyst in gas phase oxidation reactions. Till date, this material has not drawn much attention for its application in liquid phase reactions. This paper briefly highlights our recent research on vanadyl metaphosphate concerning its fabrication, characterization and application towards liquid phase oxidation of benzyl alcohol to benzaldehyde using tert-butyl hydroperoxide (TBHP) as the oxidant. In our preliminary catalytic studies, we find that the VO(PO 3) 2 exhibits extraordinarily high activity and selectivity in oxidation of benzyl alcohol under mild conditions. The benzyl alcohol conversion is largely increased but the selectivity for benzaldehyde is slightly decreased with the increase in reaction period or temperature. The present catalyst VO(PO 3) 2 showed remarkable catalytic activity with respect to other catalytic system; conversion and selectivity with respect to aldehyde is 97 and 99%, respectively.
Abstract This paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition... more Abstract This paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition of VOHPO4·0.5H2O which was prepared by reduction of dihydrate VOPO4·2H2O with isobutanol. The material was promoted with aluminum by impregnation method. The catalysts were unambiguously characterized by N2 adsorption–desorption, XRD, FT-IR techniques, UV–Vis DRS and the total amount of the acidity of the catalysts was estimated by NH3-TPD. The catalytic activities were checked in the heterogeneous catalytic esterification of acetic acid with 1° alcohol (n-butanol) in a solvent free medium. The optimization of reaction was carried out by varying temperature from 75 to 150 °C, molar ratio (butanol:acetic acid) from 1:1 to 1:4. Under optimum conditions, the catalytic esterification runs revealed a significant effect of the VPO giving 62% conversion with 100% selectivity to butyl acetate. Graphical Abstract Vanadium Phosphate is prepared in aqueous medium by taking vanadium pentoxide, o-phosphoric acid and isobutanol. The catalyst is found to be robust enough to achieve high degree of esterification under solvent free condition.
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