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Reaction regime

In the Godrej-Lurgi process, olefins are produced by dehydration of fatty alcohols on alumina in a continuous vapor-phase process. The reaction is carried out in a specially designed isothermal multitube reactor at a temperature of approximately 300°C and a pressure of 5—10 kPa (0.05—0.10 atm). As the reaction is endothermic, temperature is maintained by circulating externally heated molten salt solution around the reactor tubes. The reaction is sensitive to temperature fluctuations and gradients, hence the need to maintain an isothermal reaction regime. [Pg.440]

There are obviously many reactions that are too fast to investigate by ordinary mixing techniques. Some important examples are proton transfers, enzymatic reactions, and noncovalent complex formation. Prior to the second half of the 20th century, these reactions were referred to as instantaneous because their kinetics could not be studied. It is now possible to measure the rates of such reactions. In Section 4.1 we will find that the fastest reactions have half-lives of the order 10 s, so the fast reaction regime encompasses a much wider range of rates than does the conventional study of kinetics. [Pg.133]

Two reaction regimes are recognised, an induction period , when little is observed to take place, followed by a reaction period , which is rapid. The... [Pg.90]

Figures 3 and 4 illustrate how G( r) changes with Keq in the fast reaction regime (tc -C to). For both figures, k and the equilibrium constant A e( = l Figures 3 and 4 illustrate how G( r) changes with Keq in the fast reaction regime (tc -C to). For both figures, k and the equilibrium constant A e( = l<i /k, are taken to vary as k, = 104/Aeq s 1 so that k = 104 s 1. Hence, the chemical relaxation time, r c, varies from 0.9 x 10-5 to 8x 10-5 s as Keq varies from 0.1 to 5. If there is a sufficiently large difference in fluorescence between A and B, a term in G(r) that varies as exp(—r/tc) can provide a direct readout of the kinetics of...
Figures 1 shows the catalytic performance of the Fe-BEA catalysts in the temperature range of 250-550 °C. It is clear from the figure that propylene yield depends on particle size of the parent BEA zeolite. Effect of the N20 concentration has been analyzed under reaction regimes RS-1 and RS-2. Increase in N20 concentration resulted in the same propene yields but increased the N20 conversion and decreased the selectivity toward propylene. At higher temperature has been obtained increases in the formation of the molecular oxygen which further accelerates production of the undesired carbon oxides. Thus, at lower feed concentration of N20, i.e. at 1 1 feed ratio of reactants (RS-1), formation of carbon oxides is suppressed and the selectivity of ODHP reaction is... Figures 1 shows the catalytic performance of the Fe-BEA catalysts in the temperature range of 250-550 °C. It is clear from the figure that propylene yield depends on particle size of the parent BEA zeolite. Effect of the N20 concentration has been analyzed under reaction regimes RS-1 and RS-2. Increase in N20 concentration resulted in the same propene yields but increased the N20 conversion and decreased the selectivity toward propylene. At higher temperature has been obtained increases in the formation of the molecular oxygen which further accelerates production of the undesired carbon oxides. Thus, at lower feed concentration of N20, i.e. at 1 1 feed ratio of reactants (RS-1), formation of carbon oxides is suppressed and the selectivity of ODHP reaction is...
These complexes are not effective hydroformylation catalysts. A reaction regime in which this phenomenon is minimized was disclosed.[33]... [Pg.30]

Figure 11.15 Plot of ln[kn] vs. 1/T displaying the three different reaction regimes. Figure 11.15 Plot of ln[kn] vs. 1/T displaying the three different reaction regimes.
Figure 26b shows the impedance predicted by eqs 8 and 9. As previously discussed, this function is known as the Gerischer impedance, derived earlier in section 3.4 for a situation involving co-limited adsorption and surface diffusion (in the context of Pt). As with the surface-mediated case, the present result corresponds to a co-limited reaction regime where both kinetics and transport determine the electrode characteristics (as reflected in the dependency of 7 chem and Qs on both fq and T eff)- The essential difference between this and the Pt case is that here the kinetics and diffusion parameters refer to a bulk-mediated rather than surface-mediated process. [Pg.572]

Compared to the base-catalyzed synthesis of biodiesel, fewer studies have dealt with the subject of acid-catalyzed transesterification of lipid feedstocks. Among acid catalysts, sulfuric acid has been the most widely studied. In the previously mentioned work of Freedman et al., the authors examined the transesterification kinetics of soybean oil with butanol using sulfuric acid. The three reaction regimes observed (in accordance with reaction rate) for base-catalyzed reactions were also observed here. A large molar ratio of alcohol-to-oil, 30 1, was required in this system in order to carry out the reaction in a reasonable time. As expected, transesterification followed pseudo-first-order kinetics for the forward reactions (Figure 2), while reverse reactions showed second-order kinetics. [Pg.67]

Recently, a set of correlations including the effect of channel shape has been proposed by Ramanathan et al. (2003) on the basis of solution of the Navier-Stokes equations in the channel, with different solutions derived for ignited-reaction and extinct-reaction regimes. The comparison of various empirical and theoretical correlations with experimentally evaluated mass transfer coefficients is given by West et al. (2003). The correlations by Ramanathan et al. (2003) or Tronconi and Forzatti (1992) have been used in most simulations presented in this chapter. [Pg.116]

Note that the advection velocity, vx, no longer appears in this expression. Therefore, this situation is called the diffusion-reaction regime. [Pg.1014]

There is practically nothing about the high-pressure liquid-side-mass transfer coefficient, ku in TBR in the open literature. The only paper published was that of Lara-Marquez et al. [57], The values of kia are determined by using the following chemical absorption systems in the slow reaction regime ... [Pg.293]

In our opinion, this book demonstrates clearly that the formalism of many-point particle densities based on the Kirkwood superposition approximation for decoupling the three-particle correlation functions is able to treat adequately all possible cases and reaction regimes studied in the book (including immobile/mobile reactants, correlated/random initial particle distributions, concentration decay/accumulation under permanent source, etc.). Results of most of analytical theories are checked by extensive computer simulations. (It should be reminded that many-particle effects under study were observed for the first time namely in computer simulations [22, 23].) Only few experimental evidences exist now for many-particle effects in bimolecular reactions, the two reliable examples are accumulation kinetics of immobile radiation defects at low temperatures in ionic solids (see [24] for experiments and [25] for their theoretical interpretation) and pseudo-first order reversible diffusion-controlled recombination of protons with excited dye molecules [26]. This is one of main reasons why we did not consider in detail some of very refined theories for the kinetics asymptotics as well as peculiarities of reactions on fractal structures ([27-29] and references therein). [Pg.593]

Referring to Fig. 4.3, it can be seen that with this value for ft the system will lie in the fast reaction regime, Region I, and that the packed column will be a suitable reactor. Also, fi in equation 4.13 is sufficiently large for tanh 0 to be effectively 1, so that equation 4.14 applies ... [Pg.206]

First of all the value of /) = VH QshDco,/ will be calculated in order to check that the fast-reaction regime will apply. [Pg.221]

In the second paper (17a), by taking into account the heat transfer to the vessel walls, a stable reaction regime is discovered which cannot be obtained by continuous variation of the external conditions. These features of the equations of combustion theory and the basic patterns of exothermic reaction in a jet studied by Ya.B. have recently been used widely in, for example, the modern theory of chemical reactors. [Pg.22]

In the case of a classical isothermic reaction (see Fig. 1), for any residence time, we find one and only one solution corresponding (as will be seen from the criteria given below) to a stable reaction regime the concentration of the original substance in the jet leaving the vessel monotonically decreases as the residence time is increased. We now consider a typical case of non-isothermic reaction [equation (17), Fig. 4]. [Pg.237]

Fig. 5.28 Procedure to diagnose reacting phase and reaction regime. Fig. 5.28 Procedure to diagnose reacting phase and reaction regime.
For Ha > 0.02, there is a considerable scope for process intensification. If a reaction is intrinsically fast (a large reaction rate constant) the design aim is to provide sufficiently intense mixing to move it into the slow reaction regime (Ha < 0.02) such that the reaction is limited by the intrinsic reaction rate rather than the mass transfer rate. [Pg.256]

In order to establish the reaction regime and to design equipment, the following need to be known ... [Pg.256]

Exploration of Novel Reaction Regimes by Micro-space Operation... [Pg.414]

Figure 3.58 shows the results of the numerical calculation of the temperature distribution for this well in an isothermal reaction regime. Isothermal conditions were realized by applying appropriate heat sinks close to the well. [Pg.464]


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See also in sourсe #XX -- [ Pg.289 ]




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Catalytic reactions kinetic regimes

Chemical reaction controlled regime

Controlling Regime in Simple Reactions

Diffusion regime of reaction

Diffusive transport/reaction regime

Fast reaction regime

Growth regime reaction controlled

Interface reaction regime

Reaction Limited Regime-Uniqueness

Reaction rate regimes

Reaction-controlled regime

Reaction-diffusion regime

Reaction-diffusion regime mass transfer time

Reaction-limited regime

Reaction-limited regime estimation

Reaction-sheet regime

Reaction-sheet regime premixed

Realization of fast chemical reactions in tubular regime

Surface reaction controlled regime

Transfer, mass with chemical reaction, regime

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