Bavani Pillay - Academia.edu (original) (raw)

Papers by Bavani Pillay

Research paper thumbnail of Coincident isolation of a novel homoisoflavonoid from Resnova humifusa and Eucomis montana (Hyacinthoideae: Hyacinthaceae)

Biochemical Systematics and Ecology, 2006

We report on the first phytochemical investigation of a member of the African genus Resnova (Hyac... more We report on the first phytochemical investigation of a member of the African genus Resnova (Hyacinthoideae: Hyacinthaceae). From the dichloromethane extract of the bulbs of both Resnova humifusa and Eucomis montana (Hyacinthoideae: Hyacinthaceae) a novel 3-...

Research paper thumbnail of The Oxidative Dehydrogenation of n-Hexane over a β-NiMoO4 Catalyst

Catalysis Letters, 2011

The oxidative dehydrogenation of n-hexane over β-NiMoO4 catalysts was performed in a fixed bed co... more The oxidative dehydrogenation of n-hexane over β-NiMoO4 catalysts was performed in a fixed bed continuous flow reactor. Catalytic testing was done below and above the flammability limits for n-hexane and the effect of reaction conditions was examined to optimize hexene selectivity. The contact times (0.61-2.4 s), n-hexane/oxygen molar ratios and nitrogen dilution (31–60%) were varied. The highest selectivity to total hexenes obtained was 54.7% which was made up of 27.4% 1-hexene, 25.0% trans-2-hexene and 2.3% cis-2-hexene. These selectivities were obtained at a fuel/O2 ratio of 2.2, a contact time of 1.0 s and 43% nitrogen dilution.Graphical AbstractThe oxidative dehydrogenation of n-hexane was investigated over β-NiMoO4. Effects of contact time, dilution and fuel air ratios were investigated. The highest selectivity to the hexenes, mainly 1-hexene, was obtained at a contact time of 1 s at a fuel/air ratio of 2.2 and 43% N2 dilution.

Research paper thumbnail of The oxidative dehydrogenation of n-hexane over Ni–Mo–O catalysts

Applied Catalysis A: General, 2009

Abstract The effect of chemical composition on nickel–molybdenum catalysts in the oxidative dehyd... more Abstract The effect of chemical composition on nickel–molybdenum catalysts in the oxidative dehydrogenation of n -hexane was studied. The catalysts consisted of the following phases: nickel oxide, molybdenum trioxide, nickel molybdate (α-NiMoO 4 and β-NiMoO 4 ) and a solid solution of nickel in a lattice of nickel molybdate. Characterization of the catalysts was carried out using ICP-OES, BET, XRD, FTIR, SEM, TPR and XPS techniques. The effect of phase composition of the catalysts on their catalytic activity and selectivity to the products obtained in the temperature range 300–500 °C was also studied. The most selective catalyst for the synthesis of hexenes was the pure β-NiMoO 4 , which gave 25% selectivity to 1-hexene and 10% selectivity to 2-hexenes and 3-hexenes at 9% conversion. The pure phases NiO and MoO 3 , although active in hexane ODH, showed poor selectivity to hexenes, particularly to 1-hexene at comparable conversions suggesting that they are not responsible for the catalytic activity of the NiO–MoO 3 system. The pure β-phase was more selective towards the hexenes than the α-phase with the difference in the molybdenum coordination believed to be the reason for the different activities and selectivities of the two modifications of NiMoO 4 . The α-phase with MoO 3 was more active, suggesting that a synergetic effect plays an important role in modifying catalytic activity.

Research paper thumbnail of A study of nickel molybdenum oxide catalysts for the oxidative dehydrogenation of n-hexane

Nickel molybdenum oxide catalysts with different chemical compositions have been synthesized and ... more Nickel molybdenum oxide catalysts with different chemical compositions have been synthesized and tested for the oxidative dehydrogenation of n-hexane. The co-precipitation method was used for the synthesis and several methods were used to characterize these catalysts. These include inductively-coupled plasma optical emission spectroscopy, Raman spectroscopy, infrared spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, temperature programmed reduction, temperature programmed desorption, X-ray photo-electron spectroscopy and X-ray diffraction spectroscopy techniques as well as the Brauner-Emmet-Teller technique for surface area determination. The phase composition of the catalysts was largely dependent on the chemical composition. Catalyst testing on n-hexane feed was done with a fixed bed continuous flow reactor and experiments were performed with feed/air ratios above and below the flammability limit. Varied reaction conditions were used for the catalytic testing. Prior to the catalytic testing, blank experiments were performed. Analysis of the products were done both online and offline in conjunction with gas chromatography employing FID and TCD detectors. The influence of the catalyst on the conversion of n-hexane and selectivity to dehydrogenation products is reported. Products observed were the carbon oxides (CO and CO 2), isomers of hexene (1-hexene, 2-hexene and 3-hexene), cyclic C 6 products (cyclohexene and benzene), cracked products: alkanes/alkenes (propane/ene, butane/ene) and oxygenates (ethanal, acetic acid and propanoic acid). β-NiMoO 4 was most selective to the hexenes, especially, 1-hexene and a reaction scheme is proposed.

Research paper thumbnail of Extractives from eucomis montana and agapanthus inapertus

1.2. Structure of quinine 2 1.3. Structure of pilocarpine 1.4. Structure of reserpine 4 1.5. Stru... more 1.2. Structure of quinine 2 1.3. Structure of pilocarpine 1.4. Structure of reserpine 4 1.5. Structure of Taxol 4 1.6. Examples of some types of compounds isolated from Hyacinthaceae, (i) homisoflavonoid, (ii) cholestane glycoside, (iii) bufadienolide, (iv) acid, (v) phenolic compound, (vi) spirocyc1ic nortriterpenoid and (vii) cardenolide 1.7. Structure of a (i) saponin and (ii) sapogenin 1.8. Photograph of Eucomis montana inflorescence 1.9. Photograph of Agapanthus inapertus inflorescence 1.10. Compounds isolated from Agapanthus Chapter 2 9 15 16 2.1. Structure of the isoprene unit 2.2. Structure of squalene 2.3. Numbering system for sterols according to the IUPAC-IUB rules: (i) 1967, (ii) 1989 2.4. Structure of eucosterol 2.5. Structure of cyc1oartenol 2.6. Structure of lanosterol 2.7. Structure of (i) glycyrrhetinic acid, (ii) sophoradiol, (iii) maniladiol and (iv) epimaniladiol 2.8. Structure ofpfaffic acid 31 2.9. Numbering system for homoisoflavonoids 32 2.10. The 3-benzyl-4-chromanone type homoisoflavonoids 33 2.11. The 3-benzyl-3-hydroxy-4-chromanone type homoisoflavonoids 33 2.12. The 3-benzylidenyl-4-chromanone type homisoflavonoids 34 VB 2.13. Structure of scillascillin, brazilin and haematoxylin type homoisoflavonoids 2.14. The origin of the A and Brings ofhomoisoflavonoids 2.15. Conversion ofL-phenylalanine to trans-cinnamic acid 2.16. Conversion of 4-coumaric acid to 4-coumaryl CoA 2.17. Formation of 4',6',4-tetrahydroxy-2'-methoxychalcone 2.18. Structures of intricatin and intricatinol Chapter 3 3.1. Structures oflignan precursors 3.2. Examples of the structural diversity in lignans showing Cg-C-g' linkages 3.3. Structures of some biologically important lignans

Research paper thumbnail of Coincident isolation of a novel homoisoflavonoid from Resnova humifusa and Eucomis montana (Hyacinthoideae: Hyacinthaceae)

Biochemical Systematics and Ecology, 2006

We report on the first phytochemical investigation of a member of the African genus Resnova (Hyac... more We report on the first phytochemical investigation of a member of the African genus Resnova (Hyacinthoideae: Hyacinthaceae). From the dichloromethane extract of the bulbs of both Resnova humifusa and Eucomis montana (Hyacinthoideae: Hyacinthaceae) a novel 3-...

Research paper thumbnail of The Oxidative Dehydrogenation of n-Hexane over a β-NiMoO4 Catalyst

Catalysis Letters, 2011

The oxidative dehydrogenation of n-hexane over β-NiMoO4 catalysts was performed in a fixed bed co... more The oxidative dehydrogenation of n-hexane over β-NiMoO4 catalysts was performed in a fixed bed continuous flow reactor. Catalytic testing was done below and above the flammability limits for n-hexane and the effect of reaction conditions was examined to optimize hexene selectivity. The contact times (0.61-2.4 s), n-hexane/oxygen molar ratios and nitrogen dilution (31–60%) were varied. The highest selectivity to total hexenes obtained was 54.7% which was made up of 27.4% 1-hexene, 25.0% trans-2-hexene and 2.3% cis-2-hexene. These selectivities were obtained at a fuel/O2 ratio of 2.2, a contact time of 1.0 s and 43% nitrogen dilution.Graphical AbstractThe oxidative dehydrogenation of n-hexane was investigated over β-NiMoO4. Effects of contact time, dilution and fuel air ratios were investigated. The highest selectivity to the hexenes, mainly 1-hexene, was obtained at a contact time of 1 s at a fuel/air ratio of 2.2 and 43% N2 dilution.

Research paper thumbnail of The oxidative dehydrogenation of n-hexane over Ni–Mo–O catalysts

Applied Catalysis A: General, 2009

Abstract The effect of chemical composition on nickel–molybdenum catalysts in the oxidative dehyd... more Abstract The effect of chemical composition on nickel–molybdenum catalysts in the oxidative dehydrogenation of n -hexane was studied. The catalysts consisted of the following phases: nickel oxide, molybdenum trioxide, nickel molybdate (α-NiMoO 4 and β-NiMoO 4 ) and a solid solution of nickel in a lattice of nickel molybdate. Characterization of the catalysts was carried out using ICP-OES, BET, XRD, FTIR, SEM, TPR and XPS techniques. The effect of phase composition of the catalysts on their catalytic activity and selectivity to the products obtained in the temperature range 300–500 °C was also studied. The most selective catalyst for the synthesis of hexenes was the pure β-NiMoO 4 , which gave 25% selectivity to 1-hexene and 10% selectivity to 2-hexenes and 3-hexenes at 9% conversion. The pure phases NiO and MoO 3 , although active in hexane ODH, showed poor selectivity to hexenes, particularly to 1-hexene at comparable conversions suggesting that they are not responsible for the catalytic activity of the NiO–MoO 3 system. The pure β-phase was more selective towards the hexenes than the α-phase with the difference in the molybdenum coordination believed to be the reason for the different activities and selectivities of the two modifications of NiMoO 4 . The α-phase with MoO 3 was more active, suggesting that a synergetic effect plays an important role in modifying catalytic activity.

Research paper thumbnail of A study of nickel molybdenum oxide catalysts for the oxidative dehydrogenation of n-hexane

Nickel molybdenum oxide catalysts with different chemical compositions have been synthesized and ... more Nickel molybdenum oxide catalysts with different chemical compositions have been synthesized and tested for the oxidative dehydrogenation of n-hexane. The co-precipitation method was used for the synthesis and several methods were used to characterize these catalysts. These include inductively-coupled plasma optical emission spectroscopy, Raman spectroscopy, infrared spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, temperature programmed reduction, temperature programmed desorption, X-ray photo-electron spectroscopy and X-ray diffraction spectroscopy techniques as well as the Brauner-Emmet-Teller technique for surface area determination. The phase composition of the catalysts was largely dependent on the chemical composition. Catalyst testing on n-hexane feed was done with a fixed bed continuous flow reactor and experiments were performed with feed/air ratios above and below the flammability limit. Varied reaction conditions were used for the catalytic testing. Prior to the catalytic testing, blank experiments were performed. Analysis of the products were done both online and offline in conjunction with gas chromatography employing FID and TCD detectors. The influence of the catalyst on the conversion of n-hexane and selectivity to dehydrogenation products is reported. Products observed were the carbon oxides (CO and CO 2), isomers of hexene (1-hexene, 2-hexene and 3-hexene), cyclic C 6 products (cyclohexene and benzene), cracked products: alkanes/alkenes (propane/ene, butane/ene) and oxygenates (ethanal, acetic acid and propanoic acid). β-NiMoO 4 was most selective to the hexenes, especially, 1-hexene and a reaction scheme is proposed.

Research paper thumbnail of Extractives from eucomis montana and agapanthus inapertus

1.2. Structure of quinine 2 1.3. Structure of pilocarpine 1.4. Structure of reserpine 4 1.5. Stru... more 1.2. Structure of quinine 2 1.3. Structure of pilocarpine 1.4. Structure of reserpine 4 1.5. Structure of Taxol 4 1.6. Examples of some types of compounds isolated from Hyacinthaceae, (i) homisoflavonoid, (ii) cholestane glycoside, (iii) bufadienolide, (iv) acid, (v) phenolic compound, (vi) spirocyc1ic nortriterpenoid and (vii) cardenolide 1.7. Structure of a (i) saponin and (ii) sapogenin 1.8. Photograph of Eucomis montana inflorescence 1.9. Photograph of Agapanthus inapertus inflorescence 1.10. Compounds isolated from Agapanthus Chapter 2 9 15 16 2.1. Structure of the isoprene unit 2.2. Structure of squalene 2.3. Numbering system for sterols according to the IUPAC-IUB rules: (i) 1967, (ii) 1989 2.4. Structure of eucosterol 2.5. Structure of cyc1oartenol 2.6. Structure of lanosterol 2.7. Structure of (i) glycyrrhetinic acid, (ii) sophoradiol, (iii) maniladiol and (iv) epimaniladiol 2.8. Structure ofpfaffic acid 31 2.9. Numbering system for homoisoflavonoids 32 2.10. The 3-benzyl-4-chromanone type homoisoflavonoids 33 2.11. The 3-benzyl-3-hydroxy-4-chromanone type homoisoflavonoids 33 2.12. The 3-benzylidenyl-4-chromanone type homisoflavonoids 34 VB 2.13. Structure of scillascillin, brazilin and haematoxylin type homoisoflavonoids 2.14. The origin of the A and Brings ofhomoisoflavonoids 2.15. Conversion ofL-phenylalanine to trans-cinnamic acid 2.16. Conversion of 4-coumaric acid to 4-coumaryl CoA 2.17. Formation of 4',6',4-tetrahydroxy-2'-methoxychalcone 2.18. Structures of intricatin and intricatinol Chapter 3 3.1. Structures oflignan precursors 3.2. Examples of the structural diversity in lignans showing Cg-C-g' linkages 3.3. Structures of some biologically important lignans