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Gas Reactions (gas + reaction)
Selected AbstractsA Facile, Low-Cost, and Scalable Method of Selective Etching of Semiconducting Single-Walled Carbon Nanotubes by a Gas ReactionADVANCED MATERIALS, Issue 7 2009Hongliang Zhang A facile, scalable, and low-cost gas-treatment method for selectively etching semiconductor single-walled carbon nanotubes (SWNTs) is developed. Using SO3 gas as the etchant at a temperature of 400 °C, semiconductor SWNTs can be selectively and efficiently removed, and after this gas treatment samples enriched with metallic SWNTs can be obtained. [source] Some confusion concerning integral isoconversional methods that may result from the paper by Budrugeac and Segal "Some Methodological Problems Concerning Nonisothermal Kinetic Analysis of Heterogeneous Solid,Gas Reactions"INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2002Sergey Vyazovkin Budrugeac and Segal (Int. J. Chem. Kinet.33, 564, 2001) have generally criticized the integral isoconversional methods for producing a systematic error in the activation energy, whose value varies with the extent of conversion. We stress that this error is practically eliminated in the advanced integral isoconversional methods when using integration over small time segments (Vyazovkin, S. J. Comput Chem.22, 178, 2001) © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 418,420, 2002 [source] A new method of potassium chromate production from chromite and KOH-KNO3 -H2O binary submolten salt systemAICHE JOURNAL, Issue 10 2009Zhi Sun Abstract A new method of chromate production by applying a new reaction system of KOH-KNO3 -H2O (binary submolten salt system) is proposed and proved feasible. Under conditions of temperature 350°C, KOH-to-chromite ore ratio 2:1, stirring speed 700 rpm, KNO3 -to-chromite ore ratio 0.8:1, oxygen partial pressure 50%, and gas flow 1 L/min, chromium conversion ratio obtained is >98% with reaction time around 300 min. The decomposition of chromite ore in the system is a typical process of solid, liquid,gas reaction, which is coordinately controlled by mass diffusion in product layer and interface reaction. Apparent activation energy of decomposition in the temperature range from 280 to 370°C is 55.63 kJ/mol. During reaction, oxygen dissolves into KOH-KNO3 -H2O melt system first and some cluster, e.g. O, is formed and the mass diffusion coefficient of the cluster was calculated. The system can be considered as both a media of oxygen transportation and reactant donator. Potassium nitrate plays a role of catalyst in the oxidation decomposition reaction of chromite ore and potassium hydroxide. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The Reaction-Bonded Aluminum Oxide (RBAO) Process: II, The Solid-State Oxidation of RBAO CompactsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2000Ender Suvaci The oxidation kinetics and the fraction of aluminum that is oxidized via solid,gas reaction in reaction-bonded aluminum oxide (RBAO) compacts are shown to be strongly dependent on the oxidation temperature and the characteristics (size and green density) of the RBAO compact. Based on the Biot number, the oxidation process of RBAO compacts is controlled by convective heat transfer. Low heat transfer from the surface of the compact results in too-rapid oxidation, thermal gradients, and core,shell oxidation of the compacts. Uniform oxidation of RBAO compacts is possible by oxidizing at low temperatures (400°,470°C), where slow surface reaction of the aluminum particles controls the oxidation of the compact. A grain model is presented to cover both linear and nonlinear oxidation regimes during the oxidation of a RBAO compact, and this model predicts the experimental results when surface reaction of the aluminum particles is the rate-controlling mechanism and oxidation of the compact occurs uniformly. [source] Cd2+/NH3 treatment of Cu(In,Ga)(S,Se)2 thin-film solar cell absorbers: a model for the performance-enhancing processes in the partial electrolytePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2005M. Bär Abstract To obtain highly efficient chalcopyrite-based thin-film solar cells where the conventionally used CdS buffer is replaced by a ZnO layer prepared by the ILGAR (ion layer gas reaction) process, the Cu(In,Ga)(S,Se)2 absorber has to be pretreated in a Cd2+/NH3 solution. Based on the measured characteristics of the pH-value in the Cd2+/NH3 solution during the treatment, a model of the processes in the bath can be established. The conclusions are correlated with results from X-ray-photoelectron and X-ray-excited Auger electron spectroscopy of the Cd2+/NH3 -treated Cu(In,Ga)(S,Se)2 surface, giving an explanation for the observed formation of Cd-compounds on the surface of the absorber. Copyright © 2005 John Wiley & Sons, Ltd. [source] Some methodological problems concerning nonisothermal kinetic analysis of heterogeneous solid,gas reactionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2001P. Budrugeac Isoconversional methods, those using only one curve , = ,(T) (, is the conversion degree and T is the temperature), and invariant kinetic parameter method were applied to estimate the kinetic parameters from the following nonisothermal data: (1) simulated TG curves for a single reaction; (2) TG curves for thermal degradation of PVC; and (3) TG curves for the dehydration of CaC2O4·H2O. The results obtained by applying various methods for the same system are compared and discussed. Finally, a procedure of kinetic analysis is suggested. Its application could lead to kinetic parameter values that can be used to predict either , = ,(t) curves for other heating rates or , = ,(T) curves for isothermal conditions. © 2001 John Wiley & Sons, Inc. Int J chem Kinet 33: 564,573, 2001 [source] The influence of Metal Dusting on gas reactionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2004A. T. W. Kempen Abstract Gas composition analysis measurements have been performed in the outlet gas stream of a laboratory metal dusting test furnace in order to study the influence of metal dusting on gas reactions. This analysis has shown that carbon deposition is associated with metal dusting, i.e. the material most severely attacked by metal dusting, catalyses the formation of carbon to the largest extent. Also, metal dusting has not been seen to influence the methanation reactions. A kinetic model has been used to interpret the obtained data with respect to the catalytic activity of several high temperature materials showing that the catalytic activity of the material can vary by orders of magnitude for different reactions. [source] Some safety aspects on the design of sparger systems for the oxidation of organic liquidsPROCESS SAFETY PROGRESS, Issue 4 2006Manfred Weber Abstract This article summarizes all important parameters for a proper and safe design of the sparger system for large bubble columns, used for the oxidation of organic liquids with air or oxygen enriched air. As an example, this is done for the oxidation of cumene (isopropylbenzene), which is worldwide used in phenol processes. Based on data in the literature and newly measured flammability limits at 100° C and 5 barg, the potential hazards from uncontrolled gas reactions can be avoided, ultimately avoiding an explosion in the sparger system. For normal operation, a minimum flow of gas is necessary to ensure a uniform flow through all outlets, which are typically holes with a diameter of several millimeters. All holes should be directed towards the vessel bottom to self-drain the sparger. For start-up, a previous inerting of the sparger with nitrogen is preferable. Nevertheless, a certain amount of organic liquid may still be in the sparger system prior to start up. Therefore, the compressed air/oxygen should have a temperature below the Oxidation Initiation Temperature to avoid any initiation of a liquid phase oxidation within the sparger. In addition, the pressure in the sparger system should be high enough to keep the gas phase concentration of the organic liquid below the Lower Flammability Limit. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006 [source] Guidance on Safety/Health for Process Intensification Including MS Design.CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2010III: Risk Analysis Abstract The new technology of process intensification by multiscale equipment can significantly contribute to achieve a safer design by going from batch/semi-batch to continuous operation combined with a reduction of inventory of hazardous substances in critical stages. On the other hand, the shift to higher space-time-yields comprises new risks such as runaway reactions with hot spot formation, described in Part,I, and handling an explosive atmosphere in the presence of potential permanent ignition sources, described in Part,II. A tool was developed for preliminary risk assessments, called HAZOP-LIKE study, to cover the characteristic features of micro-designed equipment that are relatively unimportant when handling conventional equipment. Two generic cases concerning liquid/liquid and gas/gas reactions were studied to demonstrate the method. [source] | |||||||||||||