The photo-oxidation of cyclohexane on titanium dioxide: an investigation of competitive adsorption and its effects on product formation and selectivity

Almquist, Catherine B.; Biswas, Pratim

doi:10.1016/s0926-860x(01)00495-1

Cited by 148 publications

(97 citation statements)

References 15 publications

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“…The current commercial process is very energetically intensive, and several studies have focused on the direct use of photon energy to selectively oxidize cyclohexane at room temperature using a photocatalyst [1][2][3][4][5][6][7][8][9][10][11]. Although a high ketone over alcohol selectivity is obtained in photocatalytic cyclohexane oxidation, a low conversion (quantum efficiency) and rapid catalyst deactivation prevent application in practice.…”

Section: Introductionmentioning

confidence: 99%

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

et al. 2009

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Gold deposition on Hombikat UV100 was found to negatively affect the activity of this Anatase catalyst in selective photo-oxidation of cyclohexane. By ammonia TPD and DRIFT spectroscopy it was determined that the Au deposition procedure leads to a significant decrease in OH-group density (mol m -2 BET ) on Hombikat, suggesting that the amount of surface OH-groups, rather than the presence or absence of Au, is determining the catalytic performance. The importance of surface OH-groups was demonstrated by comparing the performance of Hombikat (with and without Au deposition) to surface propoxylated TiO 2 , synthesized by a sol-gel method from titanium (IV) isopropoxide. The effect of the deposition recipe of noble metals on the surface composition of TiO 2 should thus be taken into account in evaluating and explaining photocatalytic performance of TiO 2 modified by noble metals (Au), in particular in non-aqueous phase reactions.

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Section: Introductionmentioning

confidence: 99%

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

et al. 2009

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“…In addition, it should be considered that C=C stretching frequency of alkenes lies in the range between 1680-1620 cm −1 [34], therefore it overlaps to the signals due to adsorbed ketones. The formation of cyclohexene was also found in cyclohexane oxidation at low temperatures using copper chloride in pyridine as catalyst [35] and by liquid phase photocatalytic oxidation of cyclohexane on TiO 2 in various solvents [15]. In particular, by using dichloromethane as solvent, the presence of cyclohexene and cyclohexenone was found.…”

Section: Drifts Analysismentioning

confidence: 96%

“…Li et al [11] showed that the quantum size and surface state are key factors governing the selectivity in photoxidation on TiO 2 nanoparticles [12,13]. The photo-oxidation of cyclohexane on titanium dioxide was also investigated in neat cyclohexane and in various solvents showing an influence of the solvent media on the cyclohexane oxidation rate and on the selectivity to cyclohexanol and cyclohexanone [14,15].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Deactivation Phenomena Occurring in the Cyclohexane Photocatalytic Oxidative Dehydrogenation on MoOx/TiO2 through Gas Phase and in situ DRIFTS Analyses

et al. 2013

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Abstract:In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoO x /SO 4 /TiO 2 catalysts with DRIFTS analysis are presented. Analysis of products in the gas-phase discharge of a fixed bed photoreactor was coupled with in situ monitoring of the photocatalyst surface during irradiation with an IR probe. An interaction between cyclohexane and surface sulfates was found by DRIFTS analysis in the absence of UV irradiation, showing evidence of the formation of an organo-sulfur compound. In particular, in the absence of irradiation, sulfate species initiate a redox reaction through hydrogen abstraction of cyclohexane and formation of sulfate (IV) species. In previous studies, it was concluded that reduction of the sulfate (IV) species via hydrogen abstraction during UV irradiation may produce gas phase SO 2 and thereby loss of surface sulfur species. Gas phase analysis showed that the presence of MoO x species, at same sulfate loading, changes the selectivity of the photoreaction, promoting the formation of benzene. The amount of surface sulfate influenced benzene yield, which decreases when the sulfate coverage is lower. During irradiation, a strong deactivation was observed due to the poisoning of the surface by carbon deposits strongly adsorbed on catalyst surface.

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“…Water molecules cover most of the titanium dioxide slurry surface due to their polarity, and the available surface for 1-phenylethanol directly interacts with the catalyst becoming less and the diffusion resistance is increased for both of the reactant and products. Selective adsorption of reactants on the TiO 2 surface was found to account for differences in product selectivity [55]. Solvents such as chloroform strongly inhibit the photooxidation process due to the fact that it could compete with the hydrocarbon for oxidation and with O 2 for reduction.…”

Section: Solvent Effectmentioning

confidence: 99%

Selective Oxidation Using Flame Aerosol Synthesized Iron and Vanadium-Doped Nano-TiO₂

Wang

Sahle‐Demessie

Hassan

2011

Journal of Nanotechnology

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Selective photocatalytic oxidation of 1-phenyl ethanol to acetophenone using titanium dioxide (TiO 2 ) raw and doped with Fe or V, prepared by flame aerosol deposition method, was investigated. The effects of metal doping on crystal phase and morphology of the synthesized nanostructured TiO 2 were analyzed using XRD, TEM, Raman spectroscopy, and BET nitrogen adsorbed surface area measurement. The increase in the concentration of V and Fe reduced the crystalline structure and the anatase-to-rutile ratios of the synthesized TiO 2 . Synthesized TiO 2 became fine amorphous powder as the Fe and V concentrations were increased to 3 and 5%, respectively. Doping V and Fe to TiO 2 synthesized by the flame aerosol increased photocatalytic activity by 6 folds and 2.5 folds, respectively, compared to that of pure TiO 2 . It was found that an optimal doping concentration for Fe and V were 0.5% and 3%, respectively. The type and concentration of the metal dopants and the method used to add the dopant to the TiO 2 are critical parameters for enhancing the activity of the resulting photocatalyst. The effects of solvents on the photocatalytic reaction were also investigated by using both water and acetonitrile as the reaction medium.

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The photo-oxidation of cyclohexane on titanium dioxide: an investigation of competitive adsorption and its effects on product formation and selectivity

Cited by 148 publications

References 15 publications

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

Investigation of the Deactivation Phenomena Occurring in the Cyclohexane Photocatalytic Oxidative Dehydrogenation on MoOx/TiO2 through Gas Phase and in situ DRIFTS Analyses

Selective Oxidation Using Flame Aerosol Synthesized Iron and Vanadium-Doped Nano-TiO₂

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The photo-oxidation of cyclohexane on titanium dioxide: an investigation of competitive adsorption and its effects on product formation and selectivity

Cited by 148 publications

References 15 publications

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

Investigation of the Deactivation Phenomena Occurring in the Cyclohexane Photocatalytic Oxidative Dehydrogenation on MoOx/TiO2 through Gas Phase and in situ DRIFTS Analyses

Selective Oxidation Using Flame Aerosol Synthesized Iron and Vanadium-Doped Nano-TiO2

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Selective Oxidation Using Flame Aerosol Synthesized Iron and Vanadium-Doped Nano-TiO₂