Carbon dioxide reforming of methane on Ni-based bimetallic catalyts

Ay, Hale
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 reduce carbon formation and improve the life time of Ni based catalysts. Al2O3 supported and CeO2 supported Ni, Co and Ni-Co catalysts were prepared via incipient wetness impregnation method. Al2O3 was used as support material due to its high thermal stability. CeO2 was used as another support material due to its redox Ce4+/Ce3+ sites and ability to exchange oxygen. Co was introduced to the Ni-based catalyst in order to understand the effect of bimetallic catalysts in dry reforming of methane. The catalysts prepared by incipient wetness impregnation method were calcined at two different temperatures (700°C and 900°C) to elucidate the effect of calcination temperature. As an alternative to conventional preparation methods, Ni/Al2O3 catalysts were also prepared by polyol method. Ni/Al2O3 and Ni-Co/Al2O3 catalysts exhibitied comparable activities in terms of CH4 and CO2 conversion; H2 and CO yield. While doing the calcination at 700°C or 900°C did not really affect the catalytic performances of Ni/Al2O3 and Ni-Co/Al2O3, it had significant influence on the performance of Co/Al2O3. Carrying out the calcination at higher temperatures was found to be more preferable in terms of carbon deposition. Higher amount of coke was deposited on Ni-Co/Al2O3 compared to Ni/Al2O3 when the calcination was done at 700°C. DRIFTS and microcalorimetry studies showed that CO2 activation took place on Al2O3 for both Ni/Al2O3 and Ni-Co/Al2O3 catalysts. 13C NMR characterization of deposited coke demonstrated that it not only originated from CH4, but CO2 had also significant role in coke formation. Polyol process was employed to obtain Ni/Al2O3 catalysts in the presence of PVP as stabilizer and ethylene glycol as both solvent and reducing agent. The effect of PVP/Ni ratio was studied. Ni/Al2O3-without-PVP and Ni/Al2O3-PVP/Ni=2.5 catalysts exhibited quite high performance at 600°C and 700°C without making a reduction step before the reaction. The activities of CeO2 supported catalysts decreased with increasing calcination temperature. While Ni/CeO2 and Ni-Co/CeO2 provided comparable high activities, Co/CeO2 was shown to be an inactive catalyst for dry reforming of methane reaction at the specified operating conditions. O2 and CO pulse experiments were done to get information about the redox properties of different kinds of ceria samples, including commercial ceria, coprecipitated ceria and ceria fibers. The ceria fibers having the lowest surface area was shown to have the highest oxygen uptake value. This phenomenon demonstrated that the oxygen storage capacity of the ceria samples depended strongly on the morphology.


Carbondioxide capture by copper oxide nanoparticles decorated supports
Börüban, Cansu; Nalbant Esentürk, Emren; Department of Chemistry (2016)
Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities such as combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation. The amount of CO2 released to the atmosphere can be decreased by using CO2 adsorbing materials. Zeolites and activated carbons outshine with their high surface areas for the purpose of adsorbing gas molecules. Their highly porous, three dimensional structures makes them great host to trap gas molecules and purifying industrial gase...
Methane activation via bromination over sulfated Zirconia/SBA-15 catalysts
Değirmenci, Volkan; Üner, Deniz; Department of Chemical Engineering (2007)
Methane activation with bromine followed by the condensation of the methyl bromide into higher hydrocarbons or oxygenates is a novel route. However, the selective production of monobrominated methane (CH3Br) at high conversions is a crucial prerequisite. A reaction model was developed according to the kinetic data available in the literature and thoroughly studied to investigate the optimum reactor conditions for selective methane bromination in gas phase. It was concluded that at high methane (>90%) conver...
Carbon monoxide hydrogenation on supported manganese-ruthenium catalysts
Tercioglu, T; Akyurtlu, JF (1996-03-14)
CO hydrogenation over a catalyst with the nominal composition of 6.3% Mn-2.5% Ru/Al2O3 was studied in a now system with a differential fixed-bed reactor operating under atmospheric pressure. The temperature was varied between 553-613 K, H-2/CO ratio 1-3 and space velocity 5100-27600 cm(3)/(g h). The presence of manganese caused the product distribution to shift to lower olefins. For this catalyst system, secondary alkene hydrogenation was found to be significant. The activity and selectivity pattern of the ...
Direct conversion of methane to methanol over iron-exchanged zeolites
Gökçe, İklim; İpek Torun, Bahar; Department of Chemical Engineering (2022-8)
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 searc...
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...
Citation Formats
H. Ay, “Carbon dioxide reforming of methane on Ni-based bimetallic catalyts,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.