Fulya Dogan

From Grey Lab Page

My research is on catalysis and zeolites.Zeolites are microporous crystalline aluminosilicates, composed of SiO4-4 and AlO4-5 tetrahedra with O atoms connecting the neighboring tetrahedral. As the Si/Al ratio of the framework increases, the hydrothermal stability and hydrophobicity increases.The presence of Al also effects the formation of Bronsted acid sites in zeolites. Since the presence of Al results in negative charge in the framework extraframework cations are needed to keep the framework neutrality. If the extraframework cations are protons, they are always coordinated to one of these framework oxygens forming Bronsted acid sites. Because of the properties of zeolites such as pore structure, thermal stability or acidity, zeolites have wide range of application as industrial catalysts, molecular sieves, drying agents and ion exchange materials.In this study I have been working on the zeolites to form basic solid catalysts. Solid base catalysts have various advantages compared to liquid bases as they are easily separated from the reaction mixture; they are easily regenerated after the reaction and are non corrosive to the reactor system. Zeolites have been potential candidates for solid base catalysis due to their shape selective properties, their ability to concentrate reactants inside their pores and their high thermal stability. Basic molecular sieve catalysts can be prepared by nitrogen substitution for oxygen following treatment with NH₃ at high temperature. These nitrogen substituted zeolites have been shown to be nearly twice as strong as traditional zeolite bases. By the substitution nitrogen over oxygen, that the Lewis basicity of the framework increases due to the lower electronegativity of nitrogen with respect to oxygen. So, nitrogen-incorporated zeolites may thus become candidates of catalysts for a new set of base catalytic reactions.In this research, (NH) for O substitution in different zeolites and mesoporous materials is performed under ammonia flow at high temperatures. For the structural characterization, I have been using powder X-ray diffraction and Solid State MAS NMR spectroscopy techniques. X-ray Diffraction (XRD) is generally used to check for the possible crystallinity loss that may have occurred during the ammonia treatment of the zeolitic materials. Solid-state NMR is used to confirm the changes in composition that company the nitridation process inside the network structure as well as providing information about the coordination environment of the framework atoms such as Si, Al ordering, quantitative data of Si, Al and H sites as well as the determination of the position and mobility of exchangeable cations and identification of the catalytic sites.

Related Publications:

Fulya Dogan, Karl D. Hammond, Geoffrey A. Tompsett, Hua Huo, W. Curtis Conner, Jr., Scott M. Auerbach and Clare P. Grey J. Am. Chem. Soc., Articles (ASAP) [[1]]

Karl D. Hammond, Fulya Dogan, Geoffrey A. Tompsett, Vishal Agarwal, W. Curtis Conner, Jr., Clare P. Grey and Scott M. Auerbach J. Am. Chem. Soc., 2008, 130 (45), pp 14912–14913 [[2]]