Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Preparation and Characterization of Nanosized Epoxidation Catalyst

Boehmite catalysts, which are used in liquid phase catalytic epoxidation of alkenes and as a precursor of alumina, have been synthesized by hydrothermal method at various synthesis conditions from aqueous solutions of abundant aluminum salts. At epoxidation reactions, the important step is to synthesize a catalyst which utilizes hydrogen peroxide as oxidant. Catalytic epoxidation of alkenes with hydrogen peroxide, not only from a view point of an organic synthesis but also from a view point of practical greenness, is an interesting challenging problem in comparison to the established epoxidation reactions with carboxylic acids.

Purpose of this study is to investigate the influence of catalyst synthesis conditions on the properties of catalyst and to test the activities of nanocrystalline boehmite catalysts at liquid phase styrene epoxidation reaction. At hydrothermal synthesis of boehmite, effects of changing reaction parameters, such as, pH, aging time, different starting aluminum salts on the powder catalyst samples were studied by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Termogravimetric Analysis (TGA), BET Surface Area. According to the results of these analysis, crystallite size of boehmite powders are found to depend on the aging time.

In the second part of this study, liquid phase styrene epoxidation reaction was performed with prepared boehmite catalysts at 80°C in ethanol as a solvent, using 30% aqueous hydrogen peroxide solution and urea + 30% aqueous hydrogen peroxide solution as oxidants. Samples, which are taken from reaction mixture, were analyzed by Gas Chromatography (GC). Reaction conversions and product selectivities were determined. Boehmite sample, which was prepared from aluminum acetate at pH=10 and for 2 hours aging time, showed higher conversion and selectivity values with only aqueous hydrogen peroxide solution in respect to the styrene conversion and epoxide selectivity values found in the literature. Higher styrene conversion and higher epoxide selectivities were determined in the reactions when urea was addmixed to H2O2 oxidant. In addition to this, boehmite catalyst samples aged for 8 hours resulted in higher epoxide selectivity values.

Fırtına İREM
Danışman : Prof. Dr. İsmail BOZ

Anabilim Dalı : Kimya Mühendisliği

Programı : Proses ve Reaktör Tasarımı

Mezuniyet Yılı : 2008

Tez Savunma Jürisi : Prof. Dr. İsmail BOZ

Prof. Dr. Mehmet Ali GÜRKAYNAK

Doç. Dr. Mehmet MAHRAMANLIOĞLU

Doç. Dr. Cemal ÖZEROĞLU

Yrd. Doç. Dr. Gülin S. POZAN