scholarly journals Influence of Irradiance, Flow Rate, Reactor Geometry, and Photopromoter Concentration in Mineralization Kinetics of Methane in Air and in Aqueous Solutions by Photocatalytic Membranes Immobilizing Titanium Dioxide

2008 ◽  
Vol 2008 ◽  
pp. 1-14 ◽  
Author(s):  
Ignazio Renato Bellobono ◽  
Mauro Rossi ◽  
Andrea Testino ◽  
Franca Morazzoni ◽  
Riccardo Bianchi ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Aqueous Solutions ◽  
Flow Rate ◽  
Substrate Concentration ◽  
Unit Length ◽  
Quantum Yields ◽  
Oxygen Donor ◽  
Reactor Geometry ◽  
Kinetics Of

Photomineralization of methane in air (10.0–1000 ppm (mass/volume) of C) at100%relative humidity (dioxygen as oxygen donor) was systematically studied at318±3 K in an annular laboratory-scale reactor by photocatalytic membranes immobilizing titanium dioxide as a function of substrate concentration, absorbed power per unit length of membrane, reactor geometry, and concentration of a proprietary vanadium alkoxide as photopromoter. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC) disappearance, to yield carbon dioxide, were followed. At a fixed value of irradiance (0.30 W⋅cm-1), the mineralization experiments in gaseous phase were repeated as a function of flow rate (4–400 m3⋅h−1). Moreover, at a standard flow rate of 300 m3⋅h−1, the ratio between the overall reaction volume and the length of the membrane was varied, substantially by varying the volume of reservoir, from and to which circulation of gaseous stream took place. Photomineralization of methane in aqueous solutions was also studied, in the same annular reactor and in the same conditions, but in a concentration range of 0.8–2.0 ppm of C, and by using stoichiometric hydrogen peroxide as an oxygen donor. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters,k1andK1,k2andK2, were calculated, which is able to fit the whole kinetic profile adequately. The influence of irradiance onk1andk2, as well as of flow rate onK1andK2, is rationalized. The influence of reactor geometry onkvalues is discussed in view of standardization procedures of photocatalytic experiments. Modeling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photopromoter, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or intermediates leading to mineralization, were considered, and it is paralleled by a second competition kinetics involving superoxide radical anion.

scholarly journals Nonlinear Modelling of Kinetic Data Obtained from Photocatalytic Mineralisation of 2,4-Dichlorophenol on a Titanium Dioxide Membrane

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Ignazio Renato Bellobono ◽  
Roberto Scotti ◽  
Massimiliano D'Arienzo ◽  
Franca Morazzoni ◽  
Riccardo Bianchi ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Kinetic Model ◽  
Unit Length ◽  
Oxygen Demand ◽  
Quantum Yields ◽  
Superoxide Radical Anion ◽  
Series Of Experiments ◽  
Kinetics Of

Photomineralisation of 2,4-dichlorophenol (DCP) in aqueous solutions (10.0–100.0 mg/L of C) was systematically studied at318±3 K, in an annular laboratory-scale reactor, by photocatalytic membranes immobilizing titanium dioxide, as a function of substrate concentration, and absorbed power per unit length of membrane. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC) disappearance, to yield carbon dioxide, were followed (first series of experiments). At a fixed value of irradiance (1.50 W⋅cm−1), other series of mineralization experiments were repeated (second series of experiments) by carrying out only analyses of chemical oxygen demand (COD), in order to compare modelling results of the two sets of experiments. In both sets of experiments, stoichiometric hydrogen peroxide was used as oxygen donor. For the first series of experiments, a kinetic model was employed, already validated in previous work, from which, by a set of differential equations, four final optimised parameters,k1andK1,k2andK2, were calculated. By these parameters, the whole kinetic profile could be fitted adequately. The influence of irradiance onk1andk2could be rationalised very well by this four-parameter kinetic model. Modelling of quantum yields, as a function of irradiance, could also be carried out satisfactorily. As has been found previously for other kinds of substrates, modelling of quantum yields for DCP mineralization is consistent with kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or intermediates leading finally to carbon dioxide, paralleled by a second competition kinetics involving superoxide radical anion. For the second series of experiments, on the contrary, the Langmuir-Hinshelwood model was employed. Uncertainties of COD analyses, coupled with discrepancies of this model and with its inability to reproduce kinetics up to complete mineralization, are underlined.

Semiconductor Mediated Photocatalysed Reaction of Two Selected Organic Compounds in Aqueous Suspensions of Titanium Dioxide

2012 ◽  
Vol 15 (2) ◽  
Author(s):  
Niyaz A. Mir ◽  
M.M. Haque ◽  
A. Khan ◽  
K. Umar ◽  
M. Muneer ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Organic Carbon ◽  
Photocatalytic Degradation ◽  
Organic Compounds ◽  
Substrate Concentration ◽  
Degradation Kinetics ◽  
Irradiation Time ◽  
Aqueous Suspensions ◽  
Kinetics Of

AbstractSemiconductor mediated hydrogen peroxide-assisted photocatalytic degradation of two selected pesticide compounds, chloramben (1) and cyanazine (2) has been investigated in aqueous suspensions under a variety of conditions. The degradation was studied by monitoring the depletion in total organic carbon (TOC) content and decrease in substrate concentration as a function of irradiation time. The degradation kinetics of pesticide compounds 1 and 2 were investigated under different conditions such as type of TiO

scholarly journals Laboratory-scale photomineralisation of n-alkanes in aqueous solution, by photocatalytic membranes immobilising titanium dioxide

2005 ◽  
Vol 7 (2) ◽  
pp. 79-85 ◽  
Author(s):  
Ignazio Renato Bellobono ◽  
Franca Morazzoni ◽  
Riccardo Bianchi ◽  
Emilia Simona Mangone ◽  
Rodica Stanescu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Oxidation ◽  
Point Of View ◽  
Laboratory Scale ◽  
Kinetic Constants ◽  
Quantum Yields ◽  
Oxidation Of Methane ◽  
Oxygen Donor ◽  
Absorbed Power ◽  
Kinetics Of

Kinetics of photocatalytic oxidation of methane, ethane,n-heptane,n-decane, andn-dodecane, to yield intermediates, and photomineralisation of intermediates, to yield carbon dioxide and water, was studied in aqueous solution, by a laboratory-scale photoreactor and photocatalytic membranes immobilizing30±3wt.% ofTiO2, in the presence of stoichiometric hydrogen peroxide as oxygen donor. The whole volume of irradiated solution was4.000±0.005L, the ratio between this volume and the geometrical apparent surface of the irradiated side of the photocatalytic membrane was3.8±0.1cm, and the absorbed power 0.30W/cm (cylindrical geometry). A kinetic model was used, by which mineralisation of substrate toCO2was supposed to occur, by kinetic constantsk1, through one single intermediate, mediating the behaviour of all the numerous real intermediates formed in the path from the substrate toCO2(kinetic constants of formation of the latter beingk2). A competitive Langmuirian adsorption of both substrate and “intermediate” was also supposed to be operative, as expressed by apparent adsorption constantsk1andk2, possessing a, partly at least, kinetic significance. By Langmuir-Hinshelwood treatment of initial rate data, starting values of thekandKcouples were obtained, from which, by a set of differential equations, the final optimised parameters,k1andk1,k2andK2, were calculated, able fit the whole photomineralisation curve, and not only its initial segment, as the Langmuirian parameters do. The parameters of present work are critically compared with those obtained in two preceding set of studies relative ton-alkanoic acids and ton-alkanols. They are interpreted on the basis of a closer behaviour of hydrocarbons to alkanols, from the photocatalytic point of view, than to carboxylic acids are. Discussion of limiting effective quantum yields, and their comparison with maximum, theoretical values, are also carried out.

Study of the Kinetics of Polymerization of Isoprene in Aqueous Solutions of Emulsifiers and in Emulsions

1956 ◽  
Vol 29 (1) ◽  
pp. 121-125 ◽  
Author(s):  
A. P. Sheinker ◽  
S. S. Medvedev
Keyword(s):  
Hydrogen Peroxide ◽  
Aqueous Solutions ◽  
Emulsion Polymerization ◽  
Gaseous Phase ◽  
Water Soluble ◽  
Degree Of Conversion ◽  
Cetylpyridinium Bromide ◽  
Kinetic Measurements ◽  
Kinetics Of Polymerization ◽  
Kinetics Of

Abstract It has been established earlier that polymerization in aqueous solutions of emulsifiers takes place in the water or in the micellae of the emulsifier, depending on the solubility of the monomer and the initiator. The question of the topochemical properties of polymerization in emulsions has not yet been definitively explained. In a number of studies, the hypothesis was advanced that the process of emulsion polymerization takes place in the micellae of the emulsifier, according to the degree of conversion of the micellae into polymer-monomer particles, with the monomer dissolved in the polymer. In order to explain further the mechanism of emulsion polymerization, the kinetics of polymerization of isoprene in water, in solutions of emulsifier and N-cetylpyridinium bromide, and in emulsions in the presence of a water-soluble initiator (hydrogen peroxide) were studied. The dilatometric method was chosen for the kinetic measurements of solutions of emulsifier not saturated with isoprene, and for emulsions. Experiments with solutions of emulsifier saturated with monomer were made during continuous saturation of the emulsifierinitiator solution with isoprene in the gaseous phase. All the experiments were made at 50° C in the absence of oxygen.

ChemInform Abstract: KINETICS OF REACTION OF ETHYL DIXANTHOGEN WITH HYDROGEN PEROXIDE IN ALCOHOL-AQUEOUS SOLUTIONS PART 1 AND 2

1974 ◽  
Vol 5 (24) ◽  
pp. no-no
Author(s):  
TERESA MLODNICKA ◽  
MARIA PALUCH ◽  
ANDRZEJ POMIANOWSKI ◽  
EWA KRAUSS ◽  
BARBARA SIWEK
Keyword(s):  
Hydrogen Peroxide ◽  
Aqueous Solutions ◽  
Kinetics Of Reaction ◽  
Kinetics Of
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