Photocatalytic carbon dioxide reduction in liquid media

Download

index.pdf

Date

2011

Author

İpek, Bahar

Metadata

Show full item record

Item Usage Stats

250
views

98
downloads

The aim of this study is to investigate and reveal challenges in photocatalytic CO2 reduction tests performed in liquid media. Effect of test conditions in photocatalytic studies are often underestimated with an assumption of negligible mass transfer limitations in observed rate results. In this study, effect of mass transfer limitations in liquid phase photocatalytic tests was revealed with stirring rate and gas hold-up time experiments performed with Pt/TiO2 and Cu/TiO2 catalysts. In addition, apparent activation energies of 12 and 19.5 kJ/mol found with Pt/TiO2 and Cu/TiO2 catalysts respectively indicate diffusion limitations which favor back oxidation reactions resulting in low reduction yields. Photocatalytic CO2 reduction reaction is named as Artificial Photosynthesis even though present artificial system does not have sophisticated transport and membrane systems which natural systems have. Similarities and differences between artificial and natural photosynthesis are studied in order to present ideas to improve present photocatalytic rates. Kinetic and microkinetic modeling of catalytic methanol production from CO2 hydrogenation on Cu surfaces were performed in order to have an idea about kinetic limitations at photocatalytic systems. Calculations were performed at temperatures and pressures at which photocatalytic studies are conducted. The results indicated that water has an inhibitory effect on methanol formation rates and higher pressures could be implemented in photocatalytic systems for higher rates. Another implication drawn from degree of rate control calculations is that H formation step plays an important role underlying the importance of water splitting in CO2 reduction reactions.

Subject Keywords

Chemical engineering., Photosynthesis.

URI

http://etd.lib.metu.edu.tr/upload/12613183/index.pdf
https://hdl.handle.net/11511/20552

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Enzyme immobilization on titania-silica-gold thin films for biosensor applications and photocatalytic enzyme removal for surface patterning Çınar, Merve; Bakır, Ufuk; Department of Chemical Engineering (2009) The aim of this study was to investigate the viability of patterning by immobilization, photocatalytic removal, and re-immobilization steps of the enzyme on photocatalytically active thin films for biosensor fabrication purposes. For this aim, TiO2-SiO2-Au sol-gel colloids were synthesized and deposited on glass substrates as thin films by dip coating. Cysteamine linker was assembled on gold nanoparticles to functionalize thin films with amine groups for immobilization of model enzyme invertase. Effect of i...
Photocatalytic and photoelectrochemical water splitting over ordered titania nanotube arrays Karslıoğlu, Osman; Üner, Deniz; Department of Chemical Engineering (2009) The objective of this study was to investigate photocatalytic water splitting over ordered TiO2 nanotube arrays. Synthesis of ordered nanotube arrays of titania, as a micron thick film on a titanium foil was accomplished by electrochemical anodization methods defined in the literature. Effect of two types of electrolyte (aqueous and organic) on the micro-morphology was observed by scanning electron microscopy. Optimum anodization times for the TiO2 nanotube electrodes, synthesized in ethylene glycol electro...
Kinetic studies for the production of tertiary ethers used as gasoline additives Boz, Nezahat; Doğu, Timur; Department of Chemical Engineering (2004) In the present study, the kinetics studies for etherification reactions were investigated in detail. In the first phase of present study, different acidic resin catalysts were prepared by the heat treatment of Amberlyst-15 catalysts at 220°C at different durations of time and also by the synthesis of sulfonated styrene divinylbenzene cross-linked resins at different conditions. A linear dependence of reaction rate on hydrogen ion-exchange capacity was in 2M2B+ethanol reaction. However, in the case of 2M1B+e...
Artifical photosynthesis : dye assisted photocatalytic reduction of carbon dioxide over pure and platinum containing titania Özcan, Özlem; Üner, Deniz; Department of Chemical Engineering (2005) The aim of this study is to test the limits of photocatalytic reduction of CO2 over Pt and light harvesting dye promoted TiO2 films under UV and visible light. Thick and thin TiO2 film catalysts are coated onto 1 cm long glass beads via a common sol-gel procedure and dip coating technique. TiO2 thin films were promoted by Pt and three different light harvesting molecules: RuBpy (Tris (2,2̕ ا bipyridyl) ruthenium (II) chloride hexahydrate) , BrGly (1,7-dibromo-N,N̕-(t-butoxycarbonyl-methyl)-3,4:9,10-perylene...
Comparison of Fenitrothion and Trifluralin Adsorption on Organo-Zeolites and Activated Carbon. Part II: Thermodynamic Parameters and the Suitability of the Kinetic Models of Pesticide Adsorption LÜLE ŞENÖZ, Güzide Meltem; Atalay, Mustafa Ümit (Informa UK Limited, 2014-07-04) The suitability of two kinetic models and the thermodynamic parameters of pesticide adsorption were investigated based on obtained data of previous studies. Kinetic evaluation indicated that the pesticides adsorption on adsorbents followed the pseudo-second-order model. Gibbs free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (Delta S degrees) were calculated for thermodynamic parameters by using linearized Arrhenius equation. The results indicated that the sorption process of fenitrothi...

Citation Formats

B. İpek, “Photocatalytic carbon dioxide reduction in liquid media,” M.S. - Master of Science, Middle East Technical University, 2011.