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Del Arco, M.; Holgado, M. J.; Martin, C.; Rives, V. Effect of Thermal Treatments on the Properties of VP05/TiOpand Mo03/TiOz Systems. J. Catal. 1986, 99, 19-27. De Lasa, H. Application of the Pseudo-Adiabatic Operation to Catalytic Fixed Bed Reactors. Can. J. Chem. Eng. 1983, 61, 710-721. De Virgilis, A.; Gerunda, A. Optimize Energy Usage in Phthalic Anhydride Units. Hydrocarbon Process. 1982,61, 173-175. Froment, G. F. Fixed Bed Catalytic Reactors. Technological and Fundamental Design Aspects. Chem.-Ing.-Tech. 1974, 46, 374-386. Gasior, M.; Grzybowska, B. Oxidation of o-Xylene on VzO5-TiOZ Catalysts. 11. Effect of Formation of Solid Solutions of V in TiOz on Catalytic Properties. Bull. Poll. Acad. Sci. Ser. Chim. 1979, 27, 835-841. Haber, J. The Role of Surfaces in the Reactivity of Solids. Pure Appl. Chem. 1984,56, 1663-1676. Hausinger, G.; Schmelz, H.; Knozinger, H. Effect of the Method of Preparation on the Properties of Titania-Supported Vanadia Catalysts. Appl. Catal. 1988,39, 267-283. Hoffman, H. L.; Riddle, L. 41-HPIS Role in Chemical's Future. Hydrocarbon Process. 1988, Feb, 41-45. Kerschenbaum, L. S.; Lopez-Isunza, F. Dynamic Behaviour of an Industrial Scale Fixed-Bed Catalytic Reactor. Chemical Reaction Engineering, 7th International Symposium, Boston, MA, Oct 44,1982; American Chemical Society: Washington, DC, 1982; pp 109-120. Kuzin, V. A. Matematicheskie Metodi Rascheta Khimicheskovo Protsessa v Nepodvizhnom Sloe Katalizatora s Uchetom Prodol'novo i Radial'novo Perenosov. In Modelirouanie i optimizatsiya kataliticheskikh protsessou; Slin'ko, M. G., Ed.; Nauka: Moscow, 1965; pp 68-73 (in Russian). Nakamura, M.; Kawai, K.; Fujiwara, Y. The Structure and the Activity of Vanadyl Phosphate Catalysts. J. Catal. 1974, 34, 345-355. Nikolov, V. A.; Klissurski, D. G.; Hadjiivanov, K. I. Study of the Change of a Vanadia-Titania Catalyst for the Oxidation of 0-
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Particle Formation by NH3-S02Reactions at Trace Water Conditions Hsunling Bai, Pratim Biswas,* and Tim C. Keener Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0071
Particle formation from NH3-S02 reactions a t trace water vapor concentrations has been studied experimentally and theoretically. Three possible solid products-NH3S02, (NH3)2S02,and (NH4)2S205-were considered, and calculations were carried out to predict equilibrium concentrations of the reactants. A gas to particle conversion model for the NH3-S02 system was developed, considering simultaneous chemical reaction, nucleation, condensation, and coagulation. Potential applications of this system of reactions are also discussed.
Introduction The gas to particle conversion process associated with the reaction of sulfur dioxide and ammonia has attracted the attention of many researchers. It has application in the areas of ammonium sulfate production and for enhanced capture of sulfur dioxide in flue gas desulfurization processes (Hartley and Matteson, 1975; Scargill, 1971). The direct reaction of these two gases may also be prevalent in the lower stratosphere where an aerosol layer is expected to form (Scott et al., 1969). Various reaction products have been proposed in the literature depending on the reactant concentrations, reaction time, moisture content, and reaction temperature. Different products of the anhydrous reaction between NH3 and SO2 have been reported in studies dating to the nineteenth century (Divers and Ogawa, 1900; Scott et al.,
* To whom correspondence should be addressed. 0888-5885/92/2631-0088$03.00/0
1969, historical review). Badar-ud-Din and Aslam (1953) were the first to conclusively report that the products of the reaction were amidosulfurous acid (",SO2) and ammonium amidosulfite ( (NH3)2S02)below a temperature of 10 "C in the absence of water vapor. Hartley and Matteson (1975) conducted room temperature experiments of NH3 and SO2 and found by X-ray diffraction that the most likely producta were " $ 0 2 and (NHJZSO2 at water vapor concentrations approaching those of NH3 and SO2. Ammonium sulfate was found to be the product under excess moisture conditions. Vance and Peters (1976a) studied the anhydrous reactions in a concentric flow reactor and stated that (NH3)2S02being less volatile is the favored solid reaction product, except under excess SO2 concentrations. They also measured size distributions using an impactor and a diffusion battery, with particle sizes in the range of 0.01-7.5 pm. Size distributions were also reported by Carabine et al. (1971) with a mean size of around 0.12 pm. 0 1992 American Chemical Society
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A
a Mass flow controller Bypass either outlet stream Pressure gauge/regulator e Filter Rotameter
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Studies in the literature thus indicate that the products of the anhydrous reaction are primarily ",SO2 and (NH3)2S02.However, Hartley and Matteson (1975) and Vance and Peters (1976a) also reported that water vapor acts as a catalyst during the initial particle formation process. Trace quantities of water vapor (
