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Solid Reaction (solid + reaction)
Selected AbstractsChemInform Abstract: Microwave-Assisted Solid Reaction: Reduction of Esters to Alcohols by Potassium Borohydride,Lithium Chloride.CHEMINFORM, Issue 48 2001Jun-Cai Feng Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] CdS-Nanoparticle/Polymer Composite Shells Grown on Silica Nanospheres by Atom-Transfer Radical Polymerization,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2005T. Cui Abstract In this paper we describe the combined use of surface-initiated atom transfer radical polymerization (ATRP) and a gas/solid reaction in the direct preparation of CdS-nanoparticle/block-copolymer composite shells on silica nanospheres. The block copolymer, consisting of poly(cadmium dimethacrylate) (PCDMA) and poly(methyl methacrylate) (PMMA), is obtained by repeatedly performing the surface-initiated ATRP procedures in N,N -dimethylformamide (DMF) solution at room temperature, using cadmium dimethacrylate (CDMA) and methyl methacrylate (MMA) as the monomers. CdS nanoparticles with an average size of about 3,nm are generated in situ by exposing the silica nanospheres coated with block-copolymer shells to H2S gas. These synthetic core,shell nanospheres were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). These composite nanospheres exhibit strong red photoluminescence in the solid state at room temperature. [source] Fabrication of Large-Scale Single-Crystalline PrB6 Nanorods and Their Temperature-Dependent Electron Field EmissionADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Qin Yuan Zhang Abstract A simple catalysis-free approach that utilises a gas,solid reaction for the synthesis of large-scale single-crystalline PrB6 nanorods using Pr and BCl3 as starting materials is demonstrated. The nanorods exhibit a low turn-on electric field (2.80,V µ-b;m,1 at 10,µ-b;A cm,2), a low threshold electric field (6.99,V µ-b;m,1 at 1,mA cm,2), and a high current density (1.2,mA cm,2 at 7.35,V µ-b;m,1) at room temperature (RT). The turn-on and threshold electric field are found to decrease clearly from 2.80 to 0.95 and 6.99 to 3.55,V µ-b;m,1, respectively, while the emission current density increases significantly from 1.2 to 13.8,mA cm,2 (at 7.35,V µ-b;m,1) with an increase in the ambient temperature from RT to 623,K. The field enhancement factor, emission current density, and the dependence of the effective work function with temperature are investigated. The possible mechanism of the temperature-dependent emission from PrB6 nanorods is discussed. [source] Kinetics of fluid,solid reaction with an insoluble product: zinc borate by the reaction of boric acid and zinc oxideJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2004Aparna V Shete Abstract Mixing parameters influencing the final particle size and conversion of zinc oxide were studied for the formation of zinc borate. Formation of zinc borate was via a fluid,solid reaction. The process was kinetically controlled above the minimum speed for particle suspension, Ns. The reaction kinetics was developed and the rate constant was estimated. Copyright © 2004 Society of Chemical Industry [source] Synthesis of Mo,W carbide via propane carburization of the precursor sulfide: Kinetic analysisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004Tuan-Huy Nguyen Abstract Thermogravimetric analysis (TGA) has been used to investigate the carburization kinetics of Mo,W sulfide using an H2:C3H8 feed mixture. The effect of heating rate over the range 1,10 K min,1 showed that up to four different carburized products may be formed but the critical (peak) temperature for formation of these species and the amount (peak height) of each species formed are highly dependent on the heating rate employed. The critical temperature increased linearly with heating rate for each of the four products. The four TGA peaks corresponding to the four phase transformation species are consistent with XRD identifiable species, namely; ,-Mo2C, ,-Mo2C, W and MoC1,x. Isothermal conversion,time data at three different temperatures are described by a reaction-controlled shrinking core model implicating a first-order dependency on the H2:C3H8 ratio. The reaction exhibited fractional order dependence on the metal sulfide concentration, the associated global activation energy estimated as 227 kJ mol,1 is representative of a non-catalytic gas,solid reaction. Copyright © 2004 Society of Chemical Industry [source] Encapsulation of nanoparticles by polymerization compounding in a gas/solid fluidized bed reactorAICHE JOURNAL, Issue 9 2009Babak Esmaeili Abstract For the first time, a fluidized bed reactor was used for encapsulating nanoparticles by the polymerization compounding approach using Ziegler,Natta catalysts. The polymerization reaction was carried out using a solvent-free process in a gas-phase reactor. This direct gas,solid reaction greatly simplified collecting the particles of interest after polymerization because none of the extra steps often found in encapsulation processes, such as filtering and drying, were performed in this work. The grafting of the catalyst to the original surface of particles was confirmed by X-ray photoelectron spectroscopy. Micrographs obtained by transmission electron microscopy confirmed the presence of a thin layer of polymer, in the order of a few nanometers, around the particles. The thickness of this coating was affected by the operating conditions of the process. The characterization of the modified particles with electron microscopy also revealed that zirconia nanoparticles tend to be coated in an agglomerated state, whereas aluminum particles were mostly individually encapsulated by the polymer. In addition, the effects of temperature and pressure were studied on the encapsulation process and a kinetic analysis was presented based on the available models in the literature. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Al3BC3 Powder: Processing and Synthetic MechanismJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Sea-Hoon Lee The processing parameters for the synthesis of Al3BC3 powder were optimized, and the synthetic mechanism was investigated. The mechanical mixing of the raw powders promoted the formation of secondary phases due to mechanical alloying effect and contamination. Nearly X-ray pure Al3BC3 powder was obtained after the calcination of the raw powder mixture at 1800°C for 2 h in Ar by suppressing the vaporization of aluminum. During calcination, Al4C3 layer was formed at the surface of aluminum powder by the reaction with carbon, which maintained the morphology of the aluminum powder above its melting temperature. The nucleation and growth of Al3BC3 within aluminum melt began to occur at 1000°C, and became the main synthetic mechanism of Al3BC3 at 1100°C. The Al3BC3 particles synthesized at 1100°C were porous and were composed of fine hexagonal crystals. The main synthetic mechanism of A3BC3 changed into solid,solid reaction above 1100°C, and a gas,solid reaction promoted the densification of the porous Al3BC3 powder above 1340°C. [source] High-temperature sequestration of elemental mercury by noncarbon based sorbentsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Sung Jun Lee Abstract This work is concerned with sequestration of elemental Hg at high temperatures (900,1100 °C) on a sorbent that is mineral based, rather than carbon based. This sorbent consists of an intimate mixture of CaO, CaCO3, and Al2O3,2SiO2, and is manufactured in industrially relevant quantities (metric tons) from residues produced in paper recycling processes. In contrast to activated carbon (AC), this noncarbon based sorbent has special advantages in that, it can actually enhance fly ash utilization for cement manufacture, rather than diminish it, as is the case for AC. Disperse phase experiments have been conducted, using an externally heated quartz tube reactor, with sorbent feeding rates ranging from 1 to 6 g/h. Preliminary results indicate that Hg removal efficiency is sensitive to sorbent feed rates and to furnace temperature. The Hg removal percentage increased with both these variables. Two mechanisms come into play: an in-flight Hg sorption mechanism, and an Hg sorption mechanism related to sorbent deposits on the reactor wall. A maximum total (in-flight plus deposit-related) Hg removal efficiency of 83,90% was obtained at temperatures of 900,1100 °C. There was negligible sorption by either mechanism at temperatures below 600 °C. Results for the in-flight mechanism alone showed a maximum sorption efficiency at ,900 °C, whereas that on the reactor surface increased monotonically with temperature. This suggests that sorbent deactivation can occur in-flight at high temperatures, which is in agreement with other fixed bed results obtained in this laboratory. Deactivation was not apparent for the sorbent-related substance formed on the reactor wall. Raw and spent sorbents were analyzed by X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectrophotometer (SEM-EDS) to identify the sorbent mineral transitions that seem to activate the process. The in-flight mechanisms appear to involve (1) activation of the sorbent, caused most probably by an internal solid,solid reaction, followed by (2) Hg sorption, and (3) possible deactivation, if the temperatures are too high for longer period. Reactor surface mechanisms still remain to be elucidated. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Chemical-looping combustion process: Kinetics and mathematical modelingAICHE JOURNAL, Issue 4 2010Ion Iliuta Abstract Chemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO2 and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600,800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2-4 g CH4/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014-0.14 g CH4/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO2 and H2O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H2 yields increase, whereas the CO2 and H2O concentrations decrease. The kinetics parameter of the gas,solids reactions (reduction of NiO with CH4, H2, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] | |||||||||||||