The Effects of Morphology on the Oxidation of Ceria by Water and Carbon Dioxide

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Luke J. Venstrom ◽  
Nicholas Petkovich ◽  
Stephen Rudisill ◽  
Andreas Stein ◽  
Jane H. Davidson
Keyword(s):  
Carbon Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Cerium Oxide ◽  
Pore System ◽  
Production Rates ◽  
Ordered Macroporous ◽  
Kinetics Of ◽  
Interconnected Pore ◽  
Low Porosity

The oxidation of three-dimensionally ordered macroporous (3DOM) CeO2 (ceria) by H2O and CO2 at 1100 K is presented in comparison to the oxidation of nonordered mesoporous and sintered, low porosity ceria. 3DOM ceria, which features interconnected and ordered pores, increases the maximum H2 and CO production rates over the low porosity ceria by 125% and 260%, respectively, and increases the maximum H2 and CO production rates over the nonordered mesoporous cerium oxide by 75% and 175%, respectively. The increase in the kinetics of H2O and CO2 splitting with 3DOM ceria is attributed to its enhanced specific surface area and to its interconnected pore system that facilitates the transport of reacting species to and from oxidation sites.

The Oxidation of Macroporous Cerium and Cerium-Zirconium Oxide for the Solar Thermochemical Production of Fuels

2011 ◽  
Author(s):  
Luke J. Venstrom ◽  
Nicholas Petkovich ◽  
Stephen Rudisill ◽  
Andreas Stein ◽  
Jane H. Davidson
Keyword(s):  
Specific Surface ◽  
Production Rate ◽  
Surface Area ◽  
Cerium Oxide ◽  
Specific Surface Area ◽  
Zirconium Oxide ◽  
H2 Production ◽  
Production Rates ◽  
Solar Thermochemical ◽  
Ordered Porous

The H2 and CO productivity and reactivity of three-dimensionally ordered macroporous (3DOM) cerium and cerium-zirconium oxide upon H2O and CO2 oxidation at 1073K is presented in comparison to the productivity and reactivity of non-ordered porous and low porosity cerium oxide. The production of H2 and CO2 constitutes the second step of the two-step solar thermochemical H2O and CO2 splitting cycles. The 3DOM cerium oxide, with a specific surface area of 25 m2 g−1, increases the average H2 and CO production rates over the non-ordered porous cerium oxide with a specific surface area of 112 m2 g−1: the average H2 production rate increases from 5.2 cm3 g−1 min−1 to 7.9 cm3 g−1 min−1 and the average CO production rate increases from 7.7 cm3 g−1 min−1 to 21.9 cm3 g−1 min−1. The superior reactivity of 3DOM cerium oxide is attributed primarily to the stability of the 3DOM structure and also to the improved transport of reacting species to and from oxidation sites realized with the interconnected and ordered pores of the 3DOM structure. Doping the 3DOM cerium oxide with 20 mol% zirconia further stabilizes the structure and increases the average H2 and CO production rates to 10.2 cm3 g−1 min−1 and 22.1 cm3 g−1 min−1, respectively.

The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

1992 ◽  
Vol 57 (11) ◽  
pp. 2302-2308
Author(s):  
Karel Mocek ◽  
Erich Lippert ◽  
Emerich Erdös
Keyword(s):  
Thermal Decomposition ◽  
Liquid Phase ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Sodium Carbonate ◽  
Room Temperature ◽  
Active Form ◽  
The Other ◽  
Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

scholarly journals Carbon Dioxide Absorption and Release Properties of Pyrolysis Products of Dolomite Calcined in Vacuum Atmosphere

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Fei Wang ◽  
Toshihiro Kuzuya ◽  
Shinji Hirai ◽  
Jihua Li ◽  
Te Li
Keyword(s):  
Carbon Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Micropore Volume ◽  
Carbon Dioxide Absorption ◽  
Pyrolysis Products ◽  
Vacuum Atmosphere

The decomposition of dolomite into CaO and MgO was performed at 1073 K in vacuum and at 1273 K in an Ar atmosphere. The dolomite calcined in vacuum was found to have a higher specific surface area and a higher micropore volume when compared to the dolomite calcined in the Ar atmosphere. These pyrolysis products of dolomite were reacted with CO2at 673 K for 21.6 ks. On the absorption of CO2, the formation of CaCO3was observed. The degree of absorption of the dolomite calcined in vacuum was determined to be above 50%, which was higher than the degree of absorption of the dolomite calcined in the Ar atmosphere. The CO2absorption and release procedures were repeated three times for the dolomite calcined in vacuum. The specific surface area and micropore volume of calcined dolomite decreased with successive repetitions of the CO2absorption and release cycles leading to a decrease in the degree of absorption of CO2.

The non-stoichiometry of pink zinc oxide

1975 ◽  
Vol 28 (2) ◽  
pp. 229
Author(s):  
VJ Norman
Keyword(s):  
Carbon Dioxide ◽  
Zinc Oxide ◽  
Specific Surface ◽  
Nitrogen Content ◽  
Surface Area ◽  
Total Nitrogen ◽  
Reactive Oxygen ◽  
Surface Concentration ◽  
Controlled Environment ◽  
Interstitial Zinc

A highly coloured pink zinc oxide, having a total nitrogen content of 0.054%, has been prepared by heating white zinc oxide and ammonium carbamate in an atmosphere of ammonia and carbon dioxide at 200�. The preparation results in a marked increase in the specific surface area of the zinc oxide. ��� The non-stoichiometry of the pink zinc oxide has been determined, and it is shown that the amount of reactive oxygen chemisorbed on the surface increases with time. The maximum chemisorption amounted to 52 p.p.m. by weight (1.1 x 1025 ion m-3) after exposure for 35 days in a controlled environment. The surface concentration of interstitial zinc has been estimated indirectly from the reactive oxygen results. The concentration of the non-stoichiometric species in pink zinc oxide is more than an order higher than that of the white zinc oxide from which it was prepared. The results support the mechanism tentatively proposed by previous workers for the incorporation of nitrogen in zinc oxide.

Study on the Preparing of Nanowhite Carbon Black by Silica Fume

2013 ◽  
Vol 423-426 ◽  
pp. 554-559 ◽  
Author(s):  
Xin Zhi ◽  
Zhan Cheng Guo
Keyword(s):  
Carbon Dioxide ◽  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Silica Fume ◽  
Specific Surface Area ◽  
Particle Diameter ◽  
Complete Response ◽  
High Specific Surface Area ◽  
Precipitated Silica

This research through the study on the properties of silicon dust, put forward in combination with lime kiln tail gas recycling carbon dioxide, preparation of precipitated silica (nanoWhite Carbon Black) of high value utilization technology, and studied and summarized process of the dissolution and precipitation by carbon dioxide. The silica fume is in amorphous form, and it has some special powder properties such as ultra fine grain size and high specific surface area and high chemical activity, these provide favorable foundation for low energy consumption process of recycling the powder. In the dissolution stage, the optimization reaction time is about 40 minutes, this time to complete the process of the reaction more than 90%. And the reaction is the fastest in the first 20 minutes, complete response 75% of the reaction. In the stage of carbonization, with increase of the concentration of the precursor, the particle diameter becomes larger, but the specific surface area of the powder will reduce, the porosity and the surface activity of it will reduce corresponding.

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