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Heterogeneous Reaction (heterogeneous + reaction)
Selected AbstractsFlame soot generated under controlled combustion conditions: Heterogeneous reaction of NO2 on hexane sootINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2002M. S. Salgado We used a Combustion Aerosol Standard burner unit that affords controlled and adjustable flame conditions, and adapted it for use with liquid fuel. We prepared samples of hexane soot under different well-defined combustion conditions, and probed the chemical properties of hexane soot by using its heterogeneous interaction with NO2 in a Knudsen flow reactor. Soot generated under conditions of fuel to oxygen ratio near stoichiometry (, = 0.82) produced HONO as the main product. Yields of HONO decreased for soot generated under lean conditions (, = 0.16). Finally, NO was the principal product of the reaction for soot generated under extremely lean conditions (, = 0.09) corresponding to the lower flammability limit. We may conclude that the combustion conditions determined surface properties gauged by the heterogeneous NO2,soot interaction. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 620,631, 2002 [source] Electronic Structure of Binary Phosphoric and Arsenic TriazidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006Zeng Xiaoqing Abstract Two highly explosive binary triazides of the group 15 elements P(N3)3 and As(N3)3 have been obtained in the gas phase through the heterogeneous reaction of PCl3 and AsCl3, respectively with AgN3 at room temperature. The electronic structures of both triazides have been characterized by photoelectron spectroscopy, combined with quantum chemical calculations. This represents the first electronic study of covalent triazides. The first experimental vertical ionization potentials for P(N3)3 and As(N3)3 are 9.74 and 9.98 eV, with the contribution primarily from the lone pairs of the azido moiety and the arsenic atom, respectively. The results indicate the relative "isolation" of azido moieties in triazides and less stability of these highly explosive compounds in comparison to monoazides and diazides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A further study of factors affecting pneumatic-impact ignition of polymersFIRE AND MATERIALS, Issue 6 2006Fu-Yu Hshieh Abstract One likely cause of polymer ignition in high-pressure oxygen systems is the adiabatic-compression heating of polymers caused by pneumatic impact. The previous study showed that pneumatic-impact ignition of polymers could be initiated by a local heterogeneous reaction between the hot oxygen and the oxidation sites of the polymer. This study further investigates other factors that cause pneumatic-impact ignition of polymers in high-pressure oxygen. Because the oxygen concentration has a significant effect on pneumatic-impact ignition, threshold oxygen concentrations for pneumatic-impact ignition of six selected polymers were determined at 20.7 MPa (3000 psia), an expected service pressure in high-pressure oxygen systems. The six polymers investigated were: Teflon PTFE (polytetrafluoroethylene), Neoflon CTFE (polychlorotrifluoroethylene), PEEK (polyetheretherketone), Zytel 42 (nylon 6/6), Buna N (acrylonitrile butadiene rubber), and Viton A (copolymer of vinylidene fluoride and hexafluoropropylene). The results show that PEEK exhibited the highest threshold oxygen concentration (65%) and Zytel 42 exhibited the lowest threshold oxygen concentration (<21%). Copyright © 2006 John Wiley & Sons, Ltd. [source] A Simple and Innovative Route to Prepare a Novel Carbon Nanotube/Prussian Blue Electrode and its Utilization as a Highly Sensitive H2O2 Amperometric SensorADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Edson Nossol Abstract The utilization of iron-based species (mainly metallic iron, hematite and magnetite) encapsulated into multi-walled carbon nanotubes (CNTs) as reactants in an electrochemical synthesis is reported for the first time in this work. Prussian blue (PB) is electrosynthesized in a heterogeneous reaction between ferricyanide ions in aqueous solution and the iron-species encapsulated into CNTs, resulting in novel CNT/PB paste electrodes. This innovative preparation route produces an intimate contact between the PB and the CNTs, which improves the stability and redox properties of PB. The PB formation and the chemical interaction between the PB and the CNTs are confirmed by Raman spectroscopy. The electrode is employed as a hydrogen peroxide amperometric sensor, resulting in a very low limit of detection (1.94,×,10,8,mol L,1) and very high sensitivity (15.3,A cm,2M,1). [source] Modeling of CO2 gasification of carbon for integration with solid oxide fuel cellsAICHE JOURNAL, Issue 4 2009Andrew C. Lee Abstract This modeling study focuses on gasification of carbon by CO2 in a minimally fluidized bed containing a solid oxide fuel cell (SOFC). Kinetic parameters for a five-step reaction mechanism characterizing the Boudouard reaction (C + CO2 , 2CO) were determined thermogravimetrically at 1 atm from 973 to 1273 K. Experimentally determined kinetic parameters are employed in a transport model that predicts velocities and gas concentration profiles established in the carbon bed as a consequence of convection, diffusion, and heterogeneous reaction. The model is used to simulate the effect of an imbedded SOFC, in contact with the carbon bed. Although the model does not assume particular I-V characteristics for the fuel cell, it indicates that current densities in the practical range of 100,1000 mA/cm2 can be supported. Results show that temperature strongly affects the current density, whereas CO2 flow rate has only a weak effect. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Experimental Study and Modelling of Formation and Decay of Active Species in an Oxygen DischargeCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005A.-M. Diamy Abstract A microwave (2.45 GHz) oxygen discharge (3 hPa, 150 W, 50 mL.min,1) is studied by optical emission spectroscopy of O(5P) (line 777.4 nm) and of the atmospheric system of O2(head-line 759.4 nm). Calibration of the spectral response of the optical setup is used to determine the concentrations of O(5P) and O2(b). The concentration of the O(5P) atoms is in the range 108,109 cm,3 and the concentration of the O2(b) molecules is in the range 1014 , 2 × 1014 cm,3 along the discharge tube. An attempt is made to simulate the experimental results by using coupling the Boltzmann equation, homogeneous energy transfer V-V and V-T, heterogeneous reactions on the walls (energy transfer and recombination of atoms) and a kinetic scheme (electronic transfer and chemical reactions). The Boltzmann equation includes momentum transfer, inelastic and superelastic processes and e-e collisions. V-V and V-T transfer equations are obtained from the SSH theory and the kinetic scheme includes 65 reactions with 17 species [electrons e, ions O, and O2,, fundamental electronic neutral species O(3P), O2, O2(X,v), O3 and excited neutral species O2(a), O2(b), O2(A), O(1D), O(1S), O(5P), O(4d 5Do), O(5s 5So), O(3d 5Do) and O(4s 5So)]. A fair agreement between experimental results and modelling is obtained with the following set of fitting values: , heterogeneous deactivation coefficient for O2(b) , = 2.6 × 10,2; , rate constant of reaction [O(1D) + O(3P) , 2 O(3P)] k34 = 1.4 × 10,11 cm3.s,1; , electron concentration in the range 1010 , 1011 cm,3. Modelling shows that the recombination coefficient for oxygen atoms on the silica wall (range 1.4 × 10,3 , 0.2 × 10,3) is of the same order as the values obtained in a previous paper and that the ratio ([O] / 2 [O2]initial) is about 33,50%. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||