Direct conversion of methane to methanol over iron-exchanged zeolites

Gökçe, İklim
Methane is the primary component of natural gas and the abundance of methane is increased with increased shale gas production. The extracted methane should be converted to more valuable, liquid products on site such as methanol, which is highly versatile and an important feedstock for many chemicals. Unlike the industrial conversion of methane to methanol, which is via an indirect and highly energy intensive route, alternative routes of direct conversion of methane to methanol at milder conditions are searched for. Iron loaded zeolites are promising catalysts for catalytic conversion of methane to methanol under milder conditions and should further be investigated. In this study, iron-exchanged zeolites having different frameworks such as MOR, SSZ-13 and SSZ-39 are investigated for catalytic conversion of methane to methanol. MOR, which is a large pore zeolite showed the highest methanol formation rate and selectivity. On the other hand, small pore zeolites (SSZ-13 and SSZ-39) deactivated quickly due to coke formation and even though mesopore addition improved activity for SSZ-39, Fe-MesoMOR showed better activity than Fe-MesoSSZ-39. The effect of iron content on methanol selectivity is optimized over Fe-MOR. Mesopore addition to MOR significantly promoted the methanol selectivity, especially at lower water vapor in feed, and enhanced catalyst lifetime due to shortened diffusion pathway. At the optimized reaction conditions which are 300 °C, 30% CH4, 10% N2O and 24% H2O, Fe-MesoMOR produced 330 μmol/g/h methanol with 47% selectivity. Increasing the water vapor in feed increased methanol selectivity by suppressing secondary reactions and by promoting methanol desorption from the surface and stabilized the methanol production rate. Fe-MesoMOR is compared at the optimized conditions in this study with the best performed Fe-FER and mostly studied Fe-ZSM-5 in literature. Fe-FER exhibited a better performance than Fe-MesoMOR in terms of methanol production rate and selectivity at all temperatures, 300, 320 and 340 °C. The highest methanol formation rate of 958 μmol/g/h with 41% methanol selectivity is achieved over Fe-MesoMOR at 340 °C. The characterization of active sites is carried out using DR UV–Vis spectra of N2O and CH4 treated Fe-zeolites at 300 °C.


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İpek Torun, Bahar (null; 2018-09-12)
Increased production of shale gas motivated using methane as a chemical feedstock. For this reason, an economical process that converts methane into an easily transported and valuable chemical is needed. Direct and selective, on-site, production of methanol is desirable but challenging due to the inherent stability of methane. Selective methanol formation is proven to be possible on copper exchanged zeolites (Cu-ZSM-5 [1] and Cu-mordenite [2,3]) following a 3-step cyclic process: (i) oxidation of the Cu-zeo...
Methane to higher hydrocarbons via halogenation
Degirmenci, V; Üner, Deniz; Yılmaz, Ayşen (Elsevier BV, 2005-10-15)
Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. Th...
Catalytic conversion of methane to methanol on Cu-SSZ-13 using N2O as oxidant
İpek Torun, Bahar (2016-01-01)
Direct catalytic methanol production from methane is achieved on Cu-SSZ-13 zeolite catalysts using N2O as the oxidant. The methanol production rate on Cu-SSZ-13 (on a per gram basis) was more than twice the rate on Cu-mordenite and more than four times the rate on Cu-ZSM-5.
Carbon dioxide reforming of methane on Ni-based bimetallic catalyts
Ay, Hale; Üner, Deniz; Department of Chemical Engineering (2014)
Carbon dioxide reforming of methane is a promising process for the utilization of two important greenhouse gases and the production of synthesis gas with a lower H2/CO ratio which is preferred in Fischer–Tropsch synthesis. Ni catalysts have taken great interest in dry reforming of methane due to their high catalytic activity, easy availability and low cost. However, the main restriction of Ni-based catalysts is the formation of carbon which causes catalyst deactivation. The objective of this thesis was to r...
Oxidative coupling of methane over NbO (p-type) and Nb2O5 (n-type) semiconductor materials
Erarslanoglu, Y; Onal, I; Doğu, Timur; Senkan, S (Springer Science and Business Media LLC, 1996-01-01)
Oxidative coupling of methane to higher hydrocarbons was investigated using two types of semiconductor catalysts, NbO (p-type) and Nb2O5 (n-type) at 1 atm pressure. The ratio of methane partial pressure to oxygen partial pressure was changed from 2 to 112 and the temperature was kept at 1023 K in the experiments conducted in a cofeed mode. The results indicated a strong correlation between C-2+ selectivity performance and the electronic properties of the catalyst in terms of p- vs. n-type conductivity. The ...
Citation Formats
İ. Gökçe, “Direct conversion of methane to methanol over iron-exchanged zeolites,” M.S. - Master of Science, Middle East Technical University, 2022.