Hydrogen generation of conventional fuels over mesoporous mixed oxide catalysts under time interrrupted reaction conditions

Can, Mukaddes
In this study, catalytic activity of the Co and/or Pb-SBA-15 mesoporous catalysts in methane partial oxidation reaction was investigated. By using sol-gel, incipient wetness impregnation and post grafting method, SBA-15 samples are incorporated with Co and/or Pb at different weight loadings to provide a controlled geometry in nanometer scale. The characterization of the synthesized samples was done by XRD, N2 adsorption isotherms, FTIR, TEM images, Raman and XPS analysis. In the present study also, gas phase methane partial oxidation modeling and the synthesizing of mesoporous SBA-15 silica with different pore sizes were investigated. For the samples prepared by sol-gel method, XRD analysis showedthat cobalt exists in the form of Co3O4and Pb exist in the form of PbO. BET surface areas of the Co loaded catalysts are in the range of 479.5-640.1 m2/g. However, in Pb loaded samples, higher metal loading decrease the surface area up to 4.63 m2/g. Considering the both Co and Pb containing bi-metallic samples, TEM and BET results revealed that the ordered hexagonal mesostructure was fully destroyed. The samples prepared by incipient wetness impregnation and post grafting method characterized by using BET, TEM, Raman and XPS analysis. According to the BET results all the samples show ordered mesostructure in agreement with TEM results for all Co and/or SBA-15 mesoporous samples. TEM results also revealed that, the Co(5%) Pb(5%)-SBA-15 catalyst prepared by incipient wetness impregnation method possess big cobalt and lead oxide crystallines on the mesoporous structure. Raman analysis results indicated that cobalt exist in Co3O4 form. According to XPS results all samples containing cobalt include Co3O4. The partial oxidation of methane was carried out in a fixed bed flow-type reactor in a temperature range of 50–850°C under atmospheric pressure.According to the reaction test results, the 0.5%Rh-Co-SBA15 catalyst shows the highest methane conversion (82%) and H2 selectivity. The non-precious metal show lower reactivities, addition of Pb to the Co-SBA-15 catalyst increases the catalytic activity and decrease the H2 production temperature.


Combustion kinetics of oil shales by reaction cell experiments
Kök, Mustafa Verşan; Bagci, S. (Estonian Academy Publishers, 2008-01-01)
In this study, kinetics parameters of combustion reaction of Seyitomer and Beypazari oil shales were determined using Weijdema's model of reaction kinetics. The analysis of reaction kinetics experiments showed two different reaction regions at combustion of Beypazari oil shale sample. Only one reaction region was observed at combustion of Seyitomer oil shale. CO2/CO ratios increased gradually at low and medium temperatures and stabilized at high temperatures, especially after complete combustion. A decrease...
Üner, Deniz; GERSTEIN, BC; KING, TS (Elsevier BV, 1994-04-01)
The interaction of hydrogen on potassium promoted catalysts prepared by both sequential and co-impregnation methods was studied by proton NMR spectroscopy. Potassium addition decreased the amounts of both hydrogen adsorbed on the metal (site blocking) and the support hydroxyl groups. No evidence for a ruthenium-mediated (through-metal) electronic interaction between potassium species and adsorbed hydrogen was found. During catalyst preparation, potassium was incorporated on the support by an exchange with t...
Hydrogen generation from hydrolysis of sodium borohydride using Ru(0) nanoclusters as catalyst
Özkar, Saim (Elsevier BV, 2005-12-08)
Sodium borohydride is stable in aqueous alkaline solution, however, it hydrolyses in water to hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. Generating H-2 catalytically from NaBH4 solutions has many advantages: NaBH4 solutions are nonflammable, reaction products are environmentally benign, rate of H-2 generation is easily controlled, the reaction product NaBO2 can be recycled, H-2 can be generated even at low temperatures. All of the cata...
Hydrogen generation from the hydrolysis of ammonia-borane using intrazeolite cobalt(0) nanoclusters catalyst
Rakap, Murat; Özkar, Saim (2010-04-01)
Previously being used as highly active catalyst in the hydrolysis of sodium borohydride, intrazeolite cobalt(0) nanoclusters were also employed as catalyst in the hydrolysis of ammonia-borane (H(3)NBH(3)). Intrazeolite cobalt(0) nanoclusters were found to be active catalyst in this hydrolysis reaction of ammonia-borane providing 5450 total turnovers at room temperature before deactivation. The results of the kinetic study shows that the catalytic hydrolysis of AB is first order with respect to the catalyst ...
Partial oxidation of methane on the SiO2 surface - A quantum chemical study
Ozturk, S; Onal, I; Senkan, S (2000-02-01)
Reaction pathways for methane partial oxidation (MPO) on silica were theoretically investigated using the semiempirical MOPAC-PM3 molecular orbital method. The surface of SiO2 was modeled by a helical Si6O18H12 molecular cluster that also exhibits a strained siloxane bridge defect. First, a bond energy analysis was performed on the silica cluster with isolated 3- and 4-coordinated Si surface atoms. Calculated bond dissociation energies for Si-H, SiO-H, and SI-OH were comparable to H-CH3, H-OH, and O-O. In t...
Citation Formats
M. Can, “Hydrogen generation of conventional fuels over mesoporous mixed oxide catalysts under time interrrupted reaction conditions,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.