Liquid film reaction first order

We present an analysis for absorption and reaction of a pulse of reactant gas moving along a column containing a stationary liquid phase. For first order homogeneous reaction in the liquid film, measured moments of the effluent curve can be used to evaluate rate constants for gas-liquid reactions. This model has been applied to experimental data obtained for the absorption and reaction of carbon dioxide in aqueous Na GO - NaHCO, solutions. ... [Pg.341]

V Table 4.4.2 Equations for gas-liquid reactions A(g) + B(l) C(l) according to the two-film theory (first order in A, high excess of liquid reactant B). [Pg.225]

First-Order or Pseudo-First-Order Reaction in a Liquid Film. 23-42... [Pg.2068]

FIRST-ORDER OR PSEUDO-FIRST-ORDER REACTION IN A LIQUID FILM... [Pg.2108]

A pure gas is absorbed into a liquid with which it reacts. The concentration in the liquid is sufficiently low for the mass transfer to be covered by Fick s Law and the reaction is first-order with respect to the solute gas. It may be assumed that the film theory may be applied to the liquid and that the concentration of solute gas falls from the saturation value to zero across the film. The reaction is initially carried out at 293 K. By what factor will the mass transfer rate across the interface change, if the temperature is raised to 313 K ... [Pg.630]

Show that in steady-state diffusion through a film of liquid, accompanied by a first-order irreversible reaction, the concentration of solute in the film at depth r below the interface is given by ... [Pg.854]

Example 11.12 Solve Equations (11.31) and (11.32) for the simple case of constant parameters and a pseudo-first-order reaction occurring in the liquid phase of a component supplied from the gas phase. The gas-phase film resistance is negligible. The inlet concentration of the reactive component is... [Pg.407]

Liquid phase oxidation reaction of acetaldehyde with Mn acetate catalyst can be considered as pseudo first order irreversible reaction with respect to oxygen, and the reaction occurred in liquid film. The value of kinetic constant as follow k/ = 6.64.10 exp(-12709/RT), k2 = 244.17 exp(-1.8/RT) and Lj = 3.11.10 exp(-13639/RT) m. kmor. s. The conversion can be increased by increasing gas flow rate and temperature, however the effect of impeller rotation on the conversion is not significant. The highest conversion 32.5% was obtained at the rotation speed of 900 rpm, temperature 55 C, and gas flow rate 10" m. s. The selectivity of acetic acid was affected by impeller rotation speed, gas flow rate and temperature. The highest selectivity of acetic acid was 70.5% at 500 rpm rotation speed, temperature of 55 C... [Pg.224]

The reaction (Eqn. 5.4-65) takes place in the liquid phase. The molecules are transferred away from the interface to the bulk of the liquid, while reaction takes place simultaneously. Two limiting cases can be envisaged (1) reaction is very fast compared to mass transfer, which means that reaction only takes place in the film, and (2) reaction is very slow compared to mass transfer, and reaction only takes place in the liquid bulk. A convenient dimensionless group, the Hatta number, has been defined, which characterizes the situation compared to the limiting cases. For a reaction that is first order in the gaseous reactant and zero order in the liquid reactant (cm = 1, as = 0), Hatta is ... [Pg.284]

Equations 9.2-28 and -29, in general, are coupled through equation 9.2-30, and analytical solutions may not exist (numerical solution may be required). The equations can be uncoupled only if the reaction is first-order or pseudo-first-order with respect to A, and exact analytical solutions are possible for reaction occurring in bulk hquid and liquid fdm together and in the liquid film only. For second-order kinetics with reaction occurring only in the liquid film, an approximate analytical solution is available. We develop these three cases in the rest of this section. [Pg.248]

Fast first-order or pseudo-first-order reaction in liquid film only. If the... [Pg.250]

A reagent in solution can enhance a mass transfer coefficient in comparison with that of purely physical absorption. The data of Tables 8.1 and 8.2 have been cited. One of the simpler cases that can be analyzed mathematically is that of a pseudo-first order reaction that goes to completion in a liquid film, problem P8.02.01. It appears that the enhancement depends on the specific rate of reaction, the diffusivity, the concentration of the reagent and physical mass transfer coefficient (MTC). These quantities occur in a group called the Hatta number,... [Pg.814]

Research with pilot scale units has shown that the major resistances to mass transfer of reactant to catalyst are within the liquid film surrounding the wetted catalyst particles and also intraparticle diffusion. A description of these resistances is afforded by Fig. 14. Equating the rate of mass transfer across the liquid film to the reaction rate, first order in hydrogen concentration... [Pg.195]

A reactant in liquid will be converted to a product by an irreversible first-order reaction using spherical catalyst particles that are 0.4cm in diameter. The first-order reaction rate constant and the effective diffusion coefficient of the reactant in catalyst particles are 0.001 s and 1.2 X 10 ( ii s , respectively. The liquid film mass transfer resistance of the particles can be neglected. [Pg.129]

In a first approximation a pseudo-first order reaction rate is often assumed. This must be checked against what really happens in the reactor. In semi-batch or nonsteady state oxidation, the concentration of the pollutants as well as the oxidants can change over time. A common scenario initially a fast reaction of ozone with the pollutants occurs, the reaction is probably mass transfer limited, the direct reaction in the liquid film dominates, and no dissolved ozone is present in the bulk liquid. As the concentration of the pollutants decreases, the reaction rate decreases, less ozone is consumed, leading to an increase in the dissolved ozone concentration. Metabolites less reactive with ozone are usually produced. This combined with an increase in dissolved ozone, may also shift the removal mechanism from the direct to the indirect if radical chain processes are initiated and promoted (see Chapter A 2). These changes are often not observed in waste water studies, mostly because dissolved ozone is often not measured. [Pg.137]

Ratcliff and Holdcroft (Rl), 1961 Mass transfer into liquid film flowing on sphere with first-order chemical reaction (theory and experiment). [Pg.225]

From Fig. 4.3 it may be seen that this value, although smaller than that in Example 4.2, is still sufficiently large for all the reaction to occur in the film. Also the concentration of dissolved C02 at the interface in contact with the incoming gas containing C02 at a partial pressure of 0.001 bar will be only 0.001/., i.e. 0.001/25 4 x 10"5 kmoi/m3 which is much less than 0.05 kmol/m3, the concentration of the OH- ion, so that the reaction will still behave as nseudo first-order. The enhanced liquid-side mass transfer coefficient kl will thus be k[ V(9.5 x 103 x 0.05 x 1.8 x 10 9) 0.925 x 10 3 m/s. [Pg.221]

The individual mass transfer and reaction steps outlined in Fig. 4.15 will now be described quantitatively. The aim will be firstly to obtain an expression for the overall rate of transformation of the reactant, and then to examine each term in this expression to see whether any one step contributes a disproportionate resistance to the overall rate. For simplicity we shall consider the gas to consist of just a pure reactant A, typically hydrogen, and assume the reaction which takes place on the interior surface of the catalyst particles to be first order with respect to this reactant only, i.e. the reaction is pseudo first-order with rate constant A ,. In an agitated tank suspended-bed reactor, as shown in Fig. 4.20, the gas is dispersed as bubbles, and it will be assumed that the liquid phase is well-mixed , i.e. the concentration CAL of dissolved A is uniform throughout, except in the liquid films immediately surrounding the bubbles and the particles. (It will be assumed also that the particles are not so extremely small that some are present just beneath the surface of the liquid within the diffusion film and are thus able to catalyse the reaction before A reaches the bulk of the liquid.)... [Pg.235]

The upper curve of Fig. 6 represents a pseudo-first-order reaction, at which the concentration of B is the same in the film as in the bulk of the liquid. For values of Ha greater than 3, kl for pseudo-first-order reactions is given by... [Pg.12]

A pure gas is absorbed into a liquid with which it reacts. The concentration in the liquid is sufficiently low for the mass transfer to be governed by Fick s law and the reaction is first order with respect to the solute gas. It may be assumed that the film theory may be applied to the liquid and that the concentration of solute gas falls from the saturation value to zero across the film. Obtain an expression for the mass transfer rate across the gas-liquid interface in terms of the molecular diffusivity, D, the first-order reaction rate constant ft, the film thickness L and the concentration Cas of solute in a saturated solution. The reaction is initially carried out at 293 K. By what factor will the mass transfer rate across the interface change, if the temperature is raised to 313 K Reaction rate constant at 293 K = 2.5 x 10 6 s 1. Energy of activation for reaction (in Arrhenius equation) = 26430 kJ/kmol. Universal gas constant R = 8.314 kJ/kmol K. Molecular diffusivity D = 10-9 m2/s. Film thickness, L = 10 mm. Solubility of gas at 313 K is 80% of solubility at 293 K. [Pg.248]

As discussed in Sec. 7, the factor E represents an enhancement of the rate of transfer of A caused by the reaction compared with physical absorption, i.e., Kq is replaced by EKq. The theoretical variation of E with Hatta number for a first- and second-order reaction in a liquid film is shown in Fig. 19-25. The uppermost line on the upper right represents the pseudo first-order reaction, for which E = Ha coth (Ha). Three regions are identified with different requirements of liquid holdup 8 and interfacial area a, and for which particular kinds of contacting equipment may be best ... [Pg.40]

Reaction is first order in gas reactant. 3. Gas and liquid stream are in plug flow. 4. Reactor is isothermal. 5. Gaseous reactant concentration in the gas phase is constant throughout the reactor. 6. A fraction of the catalyst external surface (tice) is covered by a flowing liquid film while the rest is exposed to a thin stagnant liquid film. Assumption 2 was verified by already reported kinetic studies. A water cooled reactor with low feed concentrations of a-methylstyrene operated between 15°C and 20°C satisfies assumptions 1 and 4 due to low volatility of the liquid reactant and due to small overall heat effects, respectively. [Pg.426]

Reactor capacity per unit volume appears to depend on four resistances in series the gas-phase transfer resistance, two liquid-phase transfer resistances, and the kinetic resistance. The highest resistance limits the capacity of the reactor. The four resistances have the unit of time and each one individually represents the time constant of the particular process under study. For example, 1 lkjigl is the time constant for the transfer of A from the bulk of the gas through the gas film to the gas-liquid interface. The same holds for the three other resistances. For a first-order reaction in a batch reactor, for example, the concentration after a certain time is given by C/C0 = exp(-r/r), in which r = 1/ A is the reaction time constant. For processes in series the individual time constants can be added to find the overall time constant of the total process. [Pg.64]

These equations are applicable for a reaction proceeding under pseudo-first-order conditions, i.e. when the concentration of the solute species is constant right up to the gas/liquid interface. It is thus possible to examine the possibility that reaction may occur in a film for the catalyst reoxidation and reduction reactions separately, if the two-stage redox mechanism is appropriate. The penetration theory leads to a series of coupled nonlinear partial differential equations which have to be solved numerically with appropriate boundary conditions. For example, if y is the distance from the melt surface, the equation governing the concentration of species B in time and space is given in (15). [Pg.132]

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