Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi University, Turkey
Approval Date: 2019
Thesis Language: Turkish
Student: Derya Erkal Uslu
Supervisor: NURAY OKTAR
Abstract:Dimethyl ether (DME) is considered as a highly promising green diesel fuel alternate, which can be produced directly from synthesis gas, using hybrid catalyst pairs having methanol synthesis and dehydration sites. The aim of this study is direct DME synthesis from syngas over mesoporous alumina supported tungstophosphoric acid (TPA) based catalysts. In this work, mesoporous alumina (SMA) was synthesized following a sol-gel route. 5, 10 and 25% by mass of TPA was incorporated into SMA following impregnation and one-pot route. These catalysts were characterized by XRD, N2 physisorption, pyridine adsorbed FTIR, SEM-EDS, ICP-MS, TGA and TPR techniques. Activity tests were performed in a fixed bed tubular reactor and at pressure range of 30-50 bar, temperature range of 200-300°C with CO/H2=1/1 feed ratio. Besides the reaction pressure and temperature, the effect of mass ratio of methanol synthesis and methanol dehydration catalysts (1:1, 1:2, 2:1) on the product distribution was investigated. According to the characterization results, catalyst structures were successfully synthesized. Among the synthesized TPA-containing SMA catalysts, the highest catalytic activity in the direct synthesis of DME was obtained by the 25TPA@SMA catalyst synthesized by impregnation method. On the other hand, SMA600 and 25TPA@SMA catalysts gave 44,8% and 56,5% CO conversions respectively. Therefore, it was concluded that TPA heteropolyacid added to alumina structure had a positive effect in the study. DME selectivity of the 25TPA/SMA catalyst synthesized by one-pot method (54,4%) was obtained higher than the selectivity of 25TPA@SMA (52,6%). Also, it was observed that the mass transfer limitation of TPA due to low pore diameter was exceeded by using alumina support material. The optimum reaction conditions were determined as 50 bar and 275°C. When methanol synthesis and methanol dehydration catalysts were used at a mass ratio of 2/1, 23,6% increase in CO conversion was obtained compared to the 1/1 ratio. Finally, in this thesis, DME with superior combustion performance, environment-friendly properties, easy storage and transport characteristics was produced in a single reactor economically