Gurkan Karakas

Characterization and temperature-programmed studies over Pd/TiO2 catalysts for NO reduction with methane

Abstract Characterization and temperature-programmed studies were performed over Pd/titania catalysts to examine their activity in the reduction of NO with methane. The catalyst was prepared using a wet impregnation technique and Pd-acetate was used as a precursor for palladium. Techniques such as BET surface area measurements, X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were used for the characterization of the catalyst before and after the reaction. Temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) were also used to probe the surface to understand its adsorption/desorption characteristics and reducing capabilities. The results obtained from these studies together with the reaction investigations have given some important insight into the functionality of this catalyst.

In situ DRIFTS characterization of wet-impregnated and sol–gel Pd/TiO2 for NO reduction with CH4

Abstract The adsorption/desorption behavior of 2%Pd/TiO2 catalysts synthesized by wet-impregnation and modified sol–gel techniques were examined in NO–CH4–O2 reaction using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalyst prepared by the modified sol–gel method showed significantly higher resistance toward oxygen while maintaining a 100% NO conversion. Under NO+CH4+O2 flow, the main adsorbed NO species was identified as the linearly adsorbed NO on metallic palladium (Pd0–NO) at high temperatures. On the oxidized sample, the major NO species was found to be a bridged nitrate species. Pd0–NO species was suggested to react with CHx to form surface NHx species. Over the sol–gel catalyst, the peak intensity for Pd0–NO species was much higher than that over the impregnated catalyst. The DRIFTS data seem to suggest that this species could play a role in reduction of NO with CH4 over Pd/TiO2 catalysts.

Partial oxidation of C5 hydrocarbons to phthalic and maleic anhydrides over suboxides of vanadia: Use of dicyclopentadiene as a probe molecule

Publisher Summary This chapter discusses the suboxides of vanadia catalysts used in pentane, pentene, dicyclopentadiene, and cyclopentane oxidation reactions. The role of alkali promoters on the catalyst selectivity has also been discussed. The catalysts were reduced in situ at different temperatures and the effect of prereduction temperature was investigated. Controlled-atmosphere characterization of prereduction, postreduction, and postreaction catalysts were performed, using X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, and temperature programmed desorption experiments. The objectives of this study were to determine the activity and selectivity of different suboxides of vanadia in maleic and phthalic anhydride formation reactions and to examine the effect of alkali promoters on the product distribution. The chapter discusses the results from the transient response and temperature programmed desorption experiments performed, using dicyclopentadiene and phthalic anhydride, as probe molecules. Dicyclopentadiene was used as a probe molecule in this phase of the study. Although an optimization procedure was not followed to maximize the yield, a prereduction temperature of 400°C, coupled with a reaction temperature of 400°C, gave the best results with a combined anhydride yield (maleic+phthalic) of about 22% under the conditions used in these experiments.

Antimicrobial Properties of Titanium Nanoparticles

In the present study, nanostructured titania particles were synthesized using hydrothermal processing and their photocatalytic antimicrobial activities were characterized. Sol-gel synthesized TiO2 samples were treated with a two step hydrothermal treatment. The first stage treatment was the alkaline treatment with 10 M of NaOH for 48 h at 130°C, followed with the second step which applied with distilled water for 48 h at 200°C. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields lamellar structure particles from the sol-gel synthesized anatase. Further treatment of nanoplates with distilled water results in crystal growth and the formation of nano structured thorn like particles. The photocatalytic antimicrobial activities of samples were determined against Escherichia coli under solar irradiation for 4 h. It was observed that the samples treated under alkaline conditions have higher antimicrobial activity than the untreated samples.