Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2015
Thesis Language: Turkish
Student: Arzu DİNLER
Principal Supervisor (For Co-Supervisor Theses): Fatma Suna Balcı
Co-Supervisor: Timur Doğu
Abstract:In this study, MCM-41 and SBA-15 supports and nmetal/nSi ratios of 0,02, 0,05 and 0,10 of single combinations of Al, Cr, and Fe loaded metal-MCM-41 and metal-SBA-15 catalysts were synthesized using direct hydrothermal synthesis method. According to XRD results, it was observed that highly ordered porous structure was conserved by metal loaded. From EDS results, large amount of incorporated metal was located inside MCM-41 structure, low amount or no incorporated metal located inside SBA-15 structure. For all samples, nitrogen adsorbtion/desorbtion isotherm behaviour was obtained as Type IV isotherm of micro-meso porous structure. BET surface areas of MCM-41 and SBA-15 supports were measured as 1119 and 855 m2/g, respectively. With increase of metal loaded in the synthesis solutions, metal-MCM-41 samples surface area, total pore and mesopore volume values were decreased, however for metal- SBA-15 samples no apparent change was observed. For both supports microporous dimensions were obtained similar (5-6 Å), in mesoporous zones SBA-15 samples (65-70 Å) were 2,5 times more than MCM-41 samples (25-28 Å). From FTIR studies with pyridine, it was seen that Bronsted acid sites were the most distinct for Al and Cr loaded MCM-41 samples, Lewis+Bronsted acid sites were more distinct for Al and Cr loaded SBA-15, and Al and Fe loaded MCM-41 samples, Lewis acid sites were more distinct for Fe loaded SBA-15, and Al and Fe loaded MCM- 41 samples. From lutidine studies, Bronsted acid sites were more distinct for Al and Cr loaded MCM-41 samples. All catalysts synthesized in synthesis solution with metal/Si mole ratio 0,10 were tested for ethanol oxidation to the differential reactor, and for same ratio Al loaded catalysts were tested for dehydration. It was determined from oxidation studies, increasing the temperature increases the ethanol conversion for Fe and Al loaded samples, and the highest value (100%) was obtained at 350oC for Fe10-SBA-15. The conversion was higher at low temperatures (67 % at 150oC) for Cr loaded samples. In addition, dehydration also increased with the conversion temperature amd 0,56 at 400C. The major products of oxidation were acetaldehyde, aceticacid+water mixture (large amount of water), low amount of ethylene, diethyleter, carbondioxide formation, the major products of dehydration were ethylene and diethylether. The selectivity of ethylene and diethyleter are higher for Al loaded catalysts, acetaldehyde selectivity are higher Fe and Cr loaded samples.