Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2019
Thesis Language: Turkish
Student: Gülce AÇIL
Supervisor: Fatma Suna Balcı
Abstract:The disadvantages of HPAs such as low surface area, dissolution in polar environment and temperature limitations can be solved by loading on an suitable support structure. The pillared clays (SK) offer advantages as a support structure and catalyst as their surface properties can be adjusted by synthesis parameters. Both catalytic activities and thermal stabilities can be increased by selecting the appropriate pillared agent. In addition to improvements of these properties, use of Al-Kegging cation with silicatungstic acid (STA) anion with a similar size, as a pillar agent affects the targeted layered structure formation and acidic properties of structure in positive direction. The STA/Al-SK catalysts obtained using HWB (Hançılı White Bentonite) clay with different W/Al ratios (W/Al ratio of 0.25 and 1.0) and acidic and alkaline clay suspension (pH 9 and 4) by changing the addition step of STA to synthesis media were calcined (300, 400 and 500 oC) at different temperatures. XRD showed that the crystal structure did not deteriorate, TEM images indicated that the layered structure was preserved, N2 adsorption/desorption isotherms demonstrated high surface area and homogeneous pore distribution. While ICP, XPS analyses and TEM images showed that W was loaded to the structure, the increase of Lewis and Bronsted acidities by STA loading was determined from FTIR spectra. The activity tests of catalysts synthesized using HWB and Standard Texas STx-1 clay mineral were carried in the ethanol dehydration reaction using differential reactor. The highest conversion values (≈ 93%) were achieved with the catalysts synthesized with STx-1 clay at low W/Al ratio under alkaline clay suspension conditions and with HWB clay with catalyst synthesized under high W/Al under alkaline clay suspension conditions. From FTIR spectra after the reaction, it was seen that the acid regions in the structure decreased and Bronsted acid centers remained in the structure more than Lewis acid centers.