Chemical reaction liquid-phase

The gas-phase rate coefficient fcc is not affecded by the fact that a chemic reaction is taking place in the liquid phase. If the liquid-phase chemical reaction is extremely fast and irreversible, the rate of absorption may be governed completely by the resistance to diffusion in the gas phase. In this case the absorption rate may be estimated by knowing only the gas-phase rate coefficient fcc of else the height of one gas-phase transfer unit Hq =... 

Propeller mixers are used for mixing liquids with viscosities up to 2,000 cp. They are suitable for the formation of low-viscosity emulsions, for dissolving applications and for liquid-phase chemical reactions. For suspensions, the upper limit of particle size is 0.1 to 0.5 mm, with a maximum dry residue of 10%. 

The kinetics of a liquid-phase chemical reaction are investigated in a laboratory-scale continuous stirred-tank reactor. The stoichiometric equation for the reaction is A 2P and it is irreversible. The reactor is a single vessel which contains 3.25 x 10 3 m3 of liquid when it is filled just to the level of the outflow. In operation, the contents of the reactor are well stirred and uniform in composition. The concentration of the reactant A in the feed stream is 0.5 kmol/m3. Results of three steady-state runs are ... 

The behavior of ion radicals in the mass spectrometer chamber opens up principal venues for their alteration. The liquid-phase chemical reaction, however, has many peculiarities, and mass spectrometric methods of ion radical transformation are not inevitably reproducible. This is quite evident and needs no further comment. 

Here ng is the density of the gas molecules, c is the average thermal velocity and 7 is the mass accommodation coefficient This is the maximum flux of gas into a liquid. In many circumstances, however, the actual gas uptake is smaller. It may be limited tty several processes, the most important of which are gas phase diffusion and Henry s Law saturation. The treatment of Henry s Law saturation in turn involves liquid phase diffusion and, in some cases, liquid phase chemical reactions. 

Most chemical and chemical technological processes, including most synthetic and all biochemical reactions, take place in the liquid phase. The solvent often plays a central role in determining the kinetics and outcome of liquid-phase chemical reactions, and the present chapter describes theoretical and computational methods that may be used to understand such effects in terms of continuum solvation models. 

Stirred tanks. These are mechanically stirred vessels, which are advantageous when absorption is accompanied by a slow liquid-phase chemical reaction. As discussed earlier (Section II), this application is considered a chemical reactor rather than an absorber. Stirred tanks provide high liquid residence times but are limited to low gas flow rates. 

When liquid-phase chemical reactions are extremely slow, the gas-phase resistance can be neglected and one can assume that the rate of reaction has a predominant effect upon the rate of absorption. In this case the differential rate of transfer is given by the equation... 

Potential reactant trace gases may, as in the stratosphere, include molecules possessing large proton affinities or large gas phase acidities. A major difference, however, arises from the fact that trace gases which can be depleted by heterogeneous interaction with aerosols may have small and possibly strongly variable abundances. Such interactions may involve condensation, dissolution, or surface as well as liquid phase chemical reactions. 

A liquid-phase chemical reaction A B takes place in a well-stirred tank. The concentration of A in the feed is Cao (mol/m ), and that in the tank and outlet stream is Ca (mol/m ). Neither concentration varies with time. The volume of the tank contents is K(m ) and the volumetric flow rate of the inlet and outlet streams is v (m /s). The reaction rate (the rate at which A is consumed by reaction in the tank) is given by the expression... 

A liquid-phase chemical reaction with stoichiometry A B takes place in a semibatch reactor. The rate of consumption of A per unit volume of the reactor contents is given by the first-order rate expression (see Problem 11.14)... 

Mass Transfer Effects on Liquid-Phase Chemical Reaction Rates... 

The rate of liquid-phase chemical reactions involving transfer of reactants from another phase depends on the homogeneous liquid-phase kinetics, physical mass transfer rates of reactants, and their thermodynamic equilibria at the phase boundaries. The interaction among these phenomena produces four distinct types of behavior depending on chemical reaction velocity. These will be examined in this paper. 

Example 9,2 Valuable product V is produced in a semibatch reactor where the following simultaneous, liquid-phase chemical reactions take place. 

Example 9.5 Autocatalytic reactions are chemical reactions where a product of the reaction affects its rate. For such reactions, a recycle reactor provides better performance. This example examines the use of a recycle reactor to carry out an autocatal5fiic reaction. Consider the liquid-phase chemical reaction... 

You are asked to design a semibatch reactor to be used in the production of specialized polymers (ethylene glycol-ethylene oxide co-polymers). The semi-batch operation is used to improve the molecular-weight distribution. Reactant B (EG) and a fixed amount of homogeneous catalyst are charged initially into the reactor (the proportion is 6.75 moles of catalyst per 1000 moles of Reactant B). Reactant A (EO) is injected at a constant rate during the operation. The polymerization reactions are represented by the following liquid-phase chemical reactions ... 

A model has been developed for oxidation of calcium sulfite in a three-phase, semibatch reactor, The overall rate of conversion to sulfate depends on the rates of solid dissolution and liquid phase chemical reaction. In this first treatment of the problem, gas-liquid mass transfer resistance did not affect the overall rate of oxidation. 

Photodissociation and recombination reactions of halogens are very fundamental to the studies of liquid-phase chemical reactions. Harris and co-workers [113, 114] carried out Dens.G experiments to study photodissociation reactions of 12, Cl2 and Br2. The photodissociation and recombination of these halogens were directly monitored from the tens of... 

Thus, W S x) cannot drive typical liquid phase chemical reactions, as is required for the validity of the Kramers model. 

Fast variable physics underlies many processes other than typical liquid phase chemical reactions. In fact, this physics is expected to be important for most condensed phase molecular processes governed by the motion of internal solute degrees of freedom, that is, those other than molecular translational and rotational coordinates. 

We have emphasized in this chapter that Arrhenius principle implies that liquid phase chemical reactions occur in a nonclassical fast variable near sudden limit timescale regime rather than in the slow variable near adiabatic regime of standard irreversible statistical mechanics. Despite this, the traditional theories of liquid phase reaction dynamics [7-10] are of the slow variable type. 

From the standpoint of liquid phase chemical reaction dynamics, the key points discussed so far are as follows ... 

Let us now consider direct pulse GC methods for determining the kinetic characteristics of liquid-phase chemical reactions. 

For a particular liquid-phase chemical reaction, the kinetic rate law is zeroth order ... 

One liquid-phase chemical reaction occurs in an isothermal configuration of PFRs. The chemical kinetics are second order and irreversible [i.e., lEt = 2(Ca) ], and the characteristic chemical reaction time constant A. is 5 min. Rank the configurations listed in Table PI-3 from highest final conversion of reactant A in the exit stream of the last PFR in series to lowest final conversion in the exit stream of the last PFR. In each case, the volumetric flow rate is 10 L/min and Ca, miet is the same. Calcnlate the final conversion of reactant A in the exit stream of the third PFR in series for case 7. 

The elementary reversible liquid-phase chemical reaction is... 

Now that one has obtained the basic information for the molar density of reactant A within the liquid-phase mass transfer boundary layer, it is necessary to calculate the molar flux of species A normal to the gas-liquid interface at r = l bubbie, and define the mass transfer coefficient via this flux. Since convective mass transfer normal to the interface was not included in the mass transfer equation with liquid-phase chemical reaction, it is not necessary to consider the convective mechanism at this stage of the development. Pick s first law of diffusion is sufficient to calculate the flux of A in the r direction at r = /fbubbie- Hence,... 

Illustrative Problem. Consider a spherical solid pellet of pure A, with mass density pa, which dissolves into stagnant liquid B exclusively by concentration diffusion in the radial direction and reacts with B. Since liquid B is present in excess, the homogeneous kinetic rate law which describes the chemical reaction is pseudo-first-order with respect to the molar density of species A in the liquid phase. Use some of the results described in this chapter to predict the time dependence of the radius of this spherical solid pellet, R(t), (a) in the presence of rapid first-order irreversible liquid-phase chemical reaction in the diffusion-limited regime, and (b) when no reaction occurs between species A and B. The molecular weight of species A is MWa. 

Numerical integration of the following equation yields R(t) in the absence of any liquid-phase chemical reaction, once again subject to the condition that R = Rq... 

Alternative Approach in the Absence of Liquid-Phase Chemical Reaction. The previous scaling law for the dissolution of spherical solid particles in a surrounding quiescent liquid can be addressed by performing an unsteady-state macroscopic mass balance on the liquid solution, with volume Viiquid- The accumulation of species A is balanced by the rate of interphase mass transfer (MT) when no chemical reaction occurs. Hence,... 

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