Solid reaction system

One goal of our experimental program with the bench-scale unit was to develop the necessary correlations for use in the ultimate design of large commercial plants. Because of the complexity inherent in the three-phase gas-liquid-solid reaction systems, many models can be postulated. In order to provide a background for the final selection of the reaction model, we shall first review briefly the three-phase system. 

Liquid-solid reaction systems, gas- 152 (LPM), liquid-phase methanation 149 LPM process, development of. .. 151... 

Figure 2. Catalytic activities of CsxH3-xPWi2O40 for decomposition of isopropylacetate as a function of the surface acidity. The reaction was carried out at 373 K in liquid-solid reaction system.

Figure 5. Relative catalytic activities of CsxH3-xPWi2O40 (x=2.1,2.2 and 2.5) for various kinds of reactions in liquid-solid reaction system. Molecular size. Pore size. Catalytic activity was estimated fi-om the initial rate of the reaction. The activity of Cs2.5 for each reaction is taken to be unity. The figures in the parentheses are the reaction rates in the unit of mmol g-l h"l.

In order to confirm further the restriction of the adsorption by the pore in the liquid-solid reaction system, the adsorption of the reactants was measiired at 303 K in the liquid- solid system, at which no reaction took place. Figure 6 provides the time courses of the adsorption of Qrclohexylacetate and isopropylacetate on Cs2.2 and Cs2.5. Both isopropylacetate and cyclohexylacetate adsorbed on Cs2.5 (Figure 6a). The ratio of the adsorption amount was about 1.5 times which is... 

Equation (7) shows the reaction temperature corresponds to the reaction pressure in Equation (4) type gas-solid reaction system. Relationship between 1 IT and In K(= Th2o) is linear at a range in which changes of AH and AS are negligible, and is called as a reaction equilibrium line. 

Atherton, J. H. (1993). "Methods for Study of Reaction Mechanisms in Liquid/Liquid and Liquid/Solid Reaction Systems and Their Relevance to the Development of Fine Chemical Processes." Trans. IChemE 71, Part A, (March), 111-18. 

This paper describes the development and operation of a continuous rotating annular chromatographic reactor (CRACR) for gas-solid reaction systems at elevated temperatures. Experimental and numerical simulation results for the dehydrogenation of cyclohexane on a Pt/Al2C>3 catalyst are presented. 

Therefore, neither the appreciable plastic deformation (both in the case of uniform compression and of local fracture) of the solid reaction systems studied nor their static state of high stress is a factor conditioning the critical phenomena and autowave processes observed during the chemical conversion in the systems. In other words, this series of experiments has provided another telling argument for the decisive role of brittle fracture in the mechanism of the phenomena considered. 

Table 1 compares the fluidized-bed reactor with alternative gas-solid reaction systems, i.e. fixed-bed, moving-bed, and entrained-flow reactors. 

In some cases, adsorption of analyte can be followed by a chemical reaction. The Langmuir-Hinshelwood (LH) and power-law models have been used successfully in describing the kinetics of a broad range of gas-solid reaction systems [105,106]. The LH model, developed to describe interactions between dissimilar adsorbates in the context of heterogeneous catalysis [107], assumes that gas adsorption follows a Langmuir isotherm and that the adsorbates are sufficiently mobile so that they equilibrate with one another on the surface on a time scale that is rapid compared to desorpticm. The power-law model assumes a Fre-undlich adsorption isotherm. Bodi models assume that the surface reaction is first-order with respect to the reactant gas, and that surface coverage asymptotically approaches a mmiolayer widi increasing gas concentration. 

Table 1-1 Examples of gas-liquid-solid-reaction systems where all three phases are either reactants or products...

Table 1-3 Examples of gas -liquid solid-reaction systems where only two phases take active parts in the reaction. The third phase is inert...

The heat effects can also be important in gas-liquid-solid reaction systems. Some reactions, such as hydrodesulfurization, hydrocracking, and coal liquefaction are known to be highly exothermic. No analysis of such reactions in the presence of a significant temperature gradient in the liquid phase is presently available. If the heat of solution is negligible, at steady state the heat balance at the catalyst surface would give... 

Gas-liquid ahsorbers which may find suitable applications in gas-liquid-solid reaction systems ... 

T.T. Tsotsis, M. Sahimi, and G. Gavalas, Membrane and Membrane Processes, in Statistical Modeling of Fluid Solid Reaction Systems. Oxford Press, 1997, in press. 

The pulsed reactor consists of a fixed bed of catalyst pellets through which the reacting fluid moves in pulsating flow. Mass-transfer coefficients are increased because of the pulsating velocity superimposed on the steady flow. For viscous liquids, or any fluid-solid reaction system which has a high extemal-mass-transfer resistance, pulsation may be a practical way to increase the global reaction rate. Biskis and Smith measured mass-transfer coefficients for hydrogen in a-methyl styrene in pulsed flow and found increases up to 80% over steady values. Bradford" found similar results based on data for the dissolution of beds of j9-naphthoI particles in water. 

Figure 8-8. Schematic illustration of mainly solid reaction system. Starting material crystals will progressively dissolve, while product crystals will grow, as the enzymic reaction happens in the liquid regions between them.

Table 1-2 (continued) - Examples of gas-liquid-solid-reaction systems where the gas and LIQUID are either REACTANTS OR PRODUCTS AND THE SOLID IS A CATALYST ( TyPE II) ( l)... 

Using the simulation package PARSIM even complex gas-solid reaction systems can be simulated without problems. Many important models (Dusty-Gas-Model, pore models) are provided by PARSIM. It can be stated that the discretization by the OCFE-method is more stable and more accurate compared to the FD-method and thus demands less simulation time at a required accuracy. 

Compare and contrast fluid-fluid and fluid-solid reaction systems for the governing differential equations. 

With these we enlist the two fundamental approaches to the noncatalytic gas-solid reaction systems The shrinking core model and volume reaction model. In the volnme reaction model, the solid is porous, the fluid easily diffuses in or ont of the solid, such that the reaction can take place homogeneously everywhere in the solid. On the other hand, with the shrinking core model (SCM), also called the sharp interface model (SIM), there is a sharp interface between the unreacted core and reacted shell of the particles. 

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