Reactor constant conversion

In using a spreadsheet for process modeling, the engineer usually finds it preferable to use constant physical properties, to express reactor performance as a constant "conversion per pass," and to use constant relative volatiHties for distillation calculations such simplifications do not affect observed trends in parametric studies and permit the user quickly to obtain useful insights into the process being modeled (74,75). 

Figure 9, Effect of the initiator activation energy on the molecular weight distribution of an addition polymer produced in a tubular reactor constant frequency factor and at widely different values of initiator—jacket temperature combination (the conversion is optimized In k/ = 26.492...

Figure 11, Effect of the initiator frequency factor on the initiator usage in an addition polymerization reactor constant activation energy (the conversion is optimized Ea = 32,921 heal/mol)...

GL 21] [no reactor] [P 22] A constant conversion is approached on increasing the reaction rate constant [73]. This shows that liquid transport of hydrogen to the catalyst has a dominant role. In turn, this means that a higher catalyst loading should have not too much effect. 

Using this reactor model, conversions as a fimction o residence time were modeled and compared with experimental data [10]. The model describes qualitatively the behavior of the experiment, showing at first near-constant behavior and then a more notable decrease in conversion with increasing residence time (due to decreasing specific interface). 

When setting the conditions in chemical reactors, equilibrium conversion will be a major consideration for reversible reactions. The equilibrium constant Ka is only a function of temperature, and Equation 6.19 provides the quantitative relationship. However, pressure change and change in concentration can be used to shift the equilibrium by changing the activities in the equilibrium constant, as will be seen later. 

At any time the reactor contains 2 m3 of fluid. The feed and effluent rates remain constant at 3.3 m3/ksec. Does the response of the system approximate that of any simple ideal reactor What conversion level is expected if the reaction has a first-order rate constant of 15 sec -... 

The catalytic tests were carried out in a fixed bed micro-reactor at atmospheric pressure at 540 °C. The feed composition was 2.5 vol.% of propane, 5 vol. % of ammonia and 5 vol.% of oxygen. The weight of catalyst in the reactor was varied in order to keep the number of Fe ions in the reactor constant (9 pmol of Fe atoms). Conversion, selectivity and yields were calculated on the basis of mass balance in dependence on the time of stream. 

The same ligand system was used in the allylic alkylation of allyl trifluoroacetate with sodium diethyl-2-methylmalonate showing a more or less constant conversion over 8 h (20 exchanged reactor volumes). This is in contrast to peripheral functionalized dendrimers (Section 4.4.2), which deactivated at longer reaction times. 

The supramolecular guest—Pd—dendrimer complex was found to have a retention of 99.4% in a CFMR and was investigated as a catalyst for the allylic ami-nation reaction. A solution of crotyl acetate and piperidine in dichloromethane was pumped through the reactor. The conversion reached its maximum ca. 80%) after approximately 1.5 h (which is equivalent to 2—3 reactor volumes of substrate solution pumped through the reactor). The conversion remained fairly constant during the course of the experiment (Fig. 8). A small decrease in conversion was observed, which was attributed to the slow deactivation of the catalyst. This experiment, however, clearly demonstrated that the non-covalently functionalized dendrimers are suitable as soluble and recyclable supports for catalysts. 

The yield structure for this catalyst at 67% conversion to material boiling below 199°C is in Table VII. The catalytic stability was poor inasmuch as the reactor temperature had to be increased approximately 60° C during 50 days to maintain constant conversion. This may be compared with another i2 catalyst containing 1 %w Pd which required a similar temperature increase over 20 days. 

Right Profiles of decrease in F(t)/F(0) for intraparticle diffusion-influenced zero-order reaction with spherical immobilized enzyme particles packed in the reactor operated under a constant conversion policy (x = 0.99). Enzyme activity decays as E(t)/E(0) = exp ( kd t). 

The present model allows the determination of the flow rate at constant conversion and operating time in a fixed-bed reactor. In Figure 19.5 it can be seen that the actually measured deactivation curve is located between the assumed exponential... 

The data given below are results of 25 design points performed at five temperatures and with five different time periods, with the idea of establishing effects of the given factors on conversion in a chemical reactor. To avoid inequality effects, five chemical reactors and five operators were included in the experiment. So, 25 design points were done in five reactors with five operators by design of experiment of a 5x5 Graeco-Latin square in such a way that each operator used each reactor only once at each temperature and for a constant conversion time period. Characters denote reactors and numbers the operators. Do the analysis of variance. 

An examination of the results of Table III suggests a method for determining the dependence of the kinetics on the partial pressure of the reactant. We see that the exponent of c0 exhibits the order of the reaction. Thus, if the value of c0 is varied at constant conversion by changing the pressure in the reactor, we can determine the dependence of the kinetics on the partial pressure of the reactant. This is the procedure used by Corrigan et al. (8). 

Industrially, catalyst activity maintenance is often screened via "temperature increase requirement" (TIR) experiments. In these experiments, constant conversion is established and the rate of temperature increase required to do so is used as a measure of the resistance of the catalyst to deactivation. However, this type of operation may mask the effect of particle size, temperature, temperature profile, and heat of reaction on poison coverage, poison profile, and the main reaction rate. This masking may be particularly important in complicated reactions and reactor systems where the TIR experiment may produce positive feedback. 

This chapter focuses attention on reactors that are operated isotherraally. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR. After iilustrating the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semibatch reactors. 

In many large-scale reactors, such as those used for hydrotreating, and reaction systems where deactivation by poisoning occurs, the catalyst decay is relatively slow. In these continuous-flow systems, constant conversion is usually necessary in order that subsequent processing steps (e.g., separation) are not upset. One w to maintain a constant conversion with a decaying catalyst in a packed or fluidized bed is to increase the reaction rate by steadily increasing the feed temperature to the reactor. (See Figme 10-26.)... 

It is always satisfying when a theory that evolves from the interpretation of data explains an observed phenomenon that was not used in its development Such is the case of using the multiplet theory to explain shape of the characteristic temperature-time curves for constant conversion in an industrial reactor. That is, to compensate for the inevitable decrease in conversion that would result as the catalyst in a reactor deactivates onstream, and operator raises the inlet temperature to maintain constant conversion. These curves are of three types A curve whose slope that monotonically increases with time, a curve whose slope monotonically decreases with time and a curve whose slope decreases with time and then increases after passing through a inflection point. The last shape is very common. An elementary analysis of the problem that follows reveals that it is not easy to explain the inflection point in the curve. 

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