Solar Syngas Production from H2O and CO2via Two-Step Thermochemical Cycles Based on Zn/ZnO and FeO/Fe3O4Redox Reactions: Kinetic Analysis

2010 ◽  
Vol 24 (4) ◽  
pp. 2716-2722 ◽  
Author(s):  
A. Stamatiou ◽  
P. G. Loutzenhiser ◽  
A. Steinfeld
Keyword(s):  
Kinetic Analysis ◽  
Thermochemical Cycles ◽  
Syngas Production

Solar Syngas Production via H2O/CO2-Splitting Thermochemical Cycles with Zn/ZnO and FeO/Fe3O4Redox Reactions†

2010 ◽  
Vol 22 (3) ◽  
pp. 851-859 ◽  
Author(s):  
A. Stamatiou ◽  
P. G. Loutzenhiser ◽  
A. Steinfeld
Keyword(s):  
Thermochemical Cycles ◽  
Syngas Production

Solar Syngas Production From H2O and CO2 via Two Step Thermochemical Cycles Based on FeO/Fe3O4 Redox Reactions: Kinetic Analysis

2010 ◽  
Author(s):  
Anastasia Stamatiou ◽  
Peter G. Loutzenhiser ◽  
Aldo Steinfeld
Keyword(s):  
Redox Reactions ◽  
Active Sites ◽  
Thermochemical Cycle ◽  
Thermochemical Cycles ◽  
Simultaneous Reduction ◽  
Syngas Production ◽  
Diffusion Controlled ◽  
Shrinking Core ◽  
Arrhenius Kinetic Parameters ◽  
Reduction Of Co2

Syngas production via a two-step H2O/CO2-splitting thermochemical cycle based on FeO/Fe3O4 redox reactions is considered using highly concentrated solar process heat. The closed cycle consists of: 1) the solar-driven endothermic dissociation of Fe3O4 to FeO; 2) the non-solar exothermic simultaneous reduction of CO2 and H2O with FeO to CO and H2 and the initial metal oxide; the latter is recycled to the first step. The second step was experimentally investigated by thermogravimetry for reactions with FeO in the range 973–1273 K and CO2/H2O concentrations of 15–75%. The reaction mechanism was characterized by an initial fast interface-controlled regime followed by a slower diffusion-controlled regime. A rate law of Langmuir-Hinshelwood type was formulated to describe the competitiveness of the reaction based on atomic oxygen exchange on active sites, and the corresponding Arrhenius kinetic parameters were determined by applying a shrinking core model.

scholarly journals A Dual Reactor for Isothermal Thermochemical Cycles of H2O/CO2 Co-Splitting Using La0.3Sr0.7Co0.7Fe0.3O3 as an Oxygen Carrier

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1018
Author(s):  
Tatiya Khamhangdatepon ◽  
Thana Sornchamni ◽  
Nuchanart Siri-Nguan ◽  
Navadol Laosiripojana ◽  
Unalome Wetwatana Hartley
Keyword(s):  
Oxygen Carrier ◽  
Active Species ◽  
Oxidation Temperature ◽  
Oxygen Storage ◽  
Feed Ratio ◽  
Optimal Time ◽  
Thermochemical Cycles ◽  
Syngas Production ◽  
Oxidation Step ◽  
Reduction And Oxidation

Catalytic performance of La0.3Sr0.7Co0.7Fe0.3O3 (LSCF3773 or LSCF) catalyst for syngas production via two step thermochemical cycles of H2O and CO2 co-splitting was investigated. Oxygen storage capacity (OSC) was found to depend on reduction temperature, rather than the oxidation temperature. The highest oxygen vacancy (Δδ) was achieved when the reduction and oxidation temperature were both fixed at 900 °C with the feed ratio (H2O to CO2) of 3 to 1, with an increasing amount of CO2 in the feed mixture. CO productivity reached its plateau at high ratios of H2O to CO2 (1:1, 1:2, and 1:2.5), while the total productivities were reduced with the same ratios. This indicated the existence of a CO2 blockage, which was the result of either high Ea of CO2 dissociation or high Ea of CO desorption, resulting in the loss in active species. From the results, it can be concluded that H2O and CO2 splitting reactions were competitive reactions. Ea of H2O and CO2 splitting was estimated at 31.01 kJ/mol and 48.05 kJ/mol, respectively, which agreed with the results obtained from the experimentation of the effect of the oxidation temperature. A dual-reactors system was applied to provide a continuous product stream, where the operation mode was switched between the reduction and oxidation step. The isothermal thermochemical cycles process, where the reduction and oxidation were performed at the same temperature, was also carried out in order to increase the overall efficiency of the process. The optimal time for the reduction and oxidation step was found to be 30 min for each step, giving total productivity of the syngas mixture at 28,000 μmol/g, approximately.

CO2Splitting via Two-Step Solar Thermochemical Cycles with Zn/ZnO and FeO/Fe3O4Redox Reactions II: Kinetic Analysis

2009 ◽  
Vol 23 (5) ◽  
pp. 2832-2839 ◽  
Author(s):  
P. G. Loutzenhiser ◽  
M. E. Gálvez ◽  
I. Hischier ◽  
A. Stamatiou ◽  
A. Frei ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Thermochemical Cycles ◽  
Solar Thermochemical

Kinetic Aspects of the Interaction of Blood Clotting Enzymes

1965 ◽  
Vol 13 (01) ◽  
pp. 155-175 ◽  
Author(s):  
H. C Hemker ◽  
P.W Hemker ◽  
E. A Loeliger
Keyword(s):  
Kinetic Analysis ◽  
Enzyme Kinetics ◽  
Blood Clotting ◽  
Enzyme System ◽  
Enzyme Kinetic ◽  
Clotting Time ◽  
Standard Methods

SummaryApplication of the methods of enzyme-kinetic analysis to the results of clotting tests is feasible and can yield useful results. However, the standard methods of enzyme kinetics are not applicable without modifications imposed by the peculiarities of the blood-clotting enzyme system. The influence of the following complicating circumstances is calculated :1. Substrate is not present in excess.2. Only relative measures exist for concentrations of substrate or enzymes.3. Enzymes and substrates are often added together.4. Reagents are not pure.5. Clotting-time is our only measure for clotting-velocity.Formulas are deduced, which makes it possible to recognize the effect of these complications.

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