Synthesis of Al-pillared layered clays as catalyst and catalyst support and characterization studies

Ill SYNTHESIS OF Al-PILLARED LAYERED CLAYS AS CATALYST AND CATALYST SUPPORT AND CHARACTERIZATION STUDIES (Ph.D. Thesis) Funda TURGUT BAŞO?LU GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY December 2004 ABSTRACT In recent, research on the application areas of pillared layered clays as catalyst and catalyst support became important due to their catalytic and molecular sieve properties. The basis of pillared layered clay production is to insert voluminous foreign agents between clay layers so that natural sheets of clay become seperated from each other and in this way pore size can be increased. In our study, by using sample taken from bentonite supply (Hançıh region) having more montmorillonite content (Hançıh white, HB) and pillared layered solution having base/metal ratios of 2.0 and 2.5, the Al-PDLC's were produced as support material and Cu and Ag catalytic sites were inserted to the PILC structure to obtain Cu-AI- and Ag-Al-PILC's. Another method was applied to synthesize the catalyst having porous structure while catalytic properties are improved in production to obtain Cu/Al-mixed PELC's. Characterization studies were performed with the products calcined at different temperatures. Metal sites being inserted were analyzed by x-ray diffraction. For samples calcined at 300°C, dmi value of Al-PILC having B/M ratio of 2.5 increased to 1.898nm after interaction step (Original clay has 0.987 nm dooi value). Almost 0.35 nm decrease was observed in dooi value of Cu/Al-mixed and metal impregnated Al- PILC samples when compared to Al-PILC. From nitrogen adsorption/desorption isotherms, BET surface area and micropore volume of A1-PILC2.5 calcined at 300°C were 296 m2/g and 0.1399 cm3/g respectively.IV After silver impregnation, those values became as 188 m2/g and 0.0863 cm3/g respectively. Decrease in surface area became more clear after copper impregnation. BET surface areas of Cu/Al-mixed PILC's calcined at 300°C changed between 210-287m2/g. No big change in average mesopore diameters were observed after metal impregnation and using mixed metal pillared solution(~3,80 nm). Decrease in BET surface area and micropore volumes, small increase in pore diameters were observed with increase in calcination temperatures. FTIR spectrums showed that for all samples, peak showing Bi ousted (chemical) acid site and Lewis (physical) acid site positions were not affected by increase in calcination temperature, metal impregnation and mixed metal pillared solution. After 150°C desorption process, no change in chemical acidity peak intensity but decrease in physical acidity peak intensity were observed. As a result of temperature programmed reduction experiments, Cu as a form of CuO in Cu-ion exchange Al-PILC was observed. Hydrogen reduction activation energy value was found as 2.765 kcal/mole for Cu-ion exchange Al- PILC having base/metal ratio of 2.5. H2 reduced Ag-Al-PILC catalyst gave 22 % CO conversion at 75°C and 100 % CO conversion at 275°C for 2 % CO feed. With II2 reduced Cu/Al-mixed PILC, 100% CO conversion were obtained at 300°C. Science Code : 603.02.01 Key Words : Pillared layered clay, catalyst, pore structure, active site, activity Page Number : 237 Adviser : Prof. Dr. Suna BALCI