Metandan direkt metanol eldesinde mezo-gözenek ilaveli küçük-gözenekli zeolit tasarımı

Methane is the main component of natural gas, a useful feedstock and an abundant material. Therefore, valorization of the methane can be considered as an important field of research. Selective conversion of methane to valuable materials such as methanol is a highly desired, yet challenging process due to the high activation energy (439 kJ mol-1) of C–H bonds in methane and weak acidity of methane. Zeolites that are exchanged with copper and iron could activate methane at low temperatures and allow selective formation of partial oxidation products using a non-catalytic 3-step process. To provide a commercial methanol production; however, selective methanol production in a continuous process should be achieved at meaningful methanol formation rates. Continuous methanol production systems using Cu-zeolites remain largely unexplored, and practical applications necessitate fundamental understanding for catalyst and process improvement. In this study, to perform the methane to methanol reaction at high yield and methanol selectivity and at mild temperatures, we have developed different type of zeolites such as Mordenite, SSZ-13, SSZ-39 and Omega with different concentration of active Cu-centers. We also introduced mesoporosity to increase methanol selectivity. Catalytic experiments were conducted with altered feed gas compositions and optimization of the partial pressure of the reactants was performed. At 573 K, microporous SSZ-39 and Mordenite showed the best methanol production rates (90.6 µmol g-1 h-1 and 54.7 µmol g-1 h-1) and plausible selectivities of 44% and 54% respectively. Mesopore addition resulted in increased methanol selectivity only for SSZ-39 with shortened crystal sizes. Increasing N2O partial pressure (to 15 kPa) have caused increased methanol production rates and selectivity values up to 52% and 130 µmol g-1 h-1 for SSZ-39. In the same way, incerasing methane partial pressure (to 40.4 kPa) resulted in incresed methanol production rates up to 90.6 µmol g-1 h-1 for SSZ-39 and 54.7 µmol g-1 h-1 for Mordenite. In addition, increasing partial pressure of water has showed increased methanol selectivity values with similar methanol production rates on SSZ-39 (311 µmol g-1 h-1) and Mordenite (116 µmol g-1 h-1).