Stoichiometry isothermal reactors

Example 7.4 The following data have been obtained in a constant-volume, isothermal reactor for a reaction with known stoichiometry A B - - C. The initial concentration of component A was 2200 mol/m. No B or C was charged to the reactor. 

Isothermal reactor. This example concerns an elementary, exothermic, second-order reversible liquid-phase reaction in a tubular reactor with a parabolic velocity distribution. Only the mole, rate law, and stoichiometry balance in the tubular reactor are required in ihi.s FEMLAB chemical engineering module. 

In the general case of a piston flow reactor, one must solve a fairly small set of simultaneous, ordinary differential equations. The minimum set (of one) arises for a single, isothermal reaction. In principle, one extra equation must be added for each additional reaction. In practice, numerical solutions are somewhat easier to implement if a separate equation is written for each reactive component. This ensures that the stoichiometry is correct and keeps the physics and chemistry of the problem rather more transparent than when the reaction coordinate method is used to obtain the smallest possible set of differential... 

The following data were collected in an isothermal, constant-volume batch reactor. The stoichiometry is known and the material balance has been closed. The reactions are A B and A C. Assume they are elementary. Determine the rate constants kj and kn-... 

This kind of reactor can be used for isothermal constant pressure operations, of reactions having a single stoichiometry. For such systems the volume is linearly related to the conversion, or... 

The design of chemical reactors encompasses at least three fields of chemical engineering thermodynamics, kinetics, and heat transfer. For example, if a reaction is run in a typical batch reactor, a simple mixing vessel, what is the maximum conversion expected This is a thermodynamic question answered with knowledge of chemical equilibrium. Also, we might like to know how long the reaction should proceed to achieve a desired conversion. This is a kinetic question. We must know not only the stoichiometry of the reaction but also the rates of the forward and the reverse reactions. We might also wish to know how much heat must be transferred to or from the reactor to maintain isothermal conditions. This is a heat transfer problem in combination with a thermodynamic problem. We must know whether the reaction is endothermic or exothermic. 

Determine the conversion for an isothermal batch reactor using the stoichiometry of Example 5-1 and the same values of initial concentrations of A, B, C, and D in a reactor volume of 1 liter operating for 4 minutes. The rate constant is k = 105[(liter)2/(gmol2 min)]. 

Catalysis and Catalytic Reactors Chap. 10 Stoichiometry (gas phase isothermal and no pressure drop) ... 

Given the reaction stoichiometry and rate laws for an isothermal system, a simple representation for targeting of reactor networks is the segregated-flow model (see, e.g., Zwietering, 1959). A schematic of this model is shown in Fig. 2. Here, we assume that only molecules of the same age, t, are perfectly mixed and that molecules of different ages mix only at the reactor exit. The performance of such a model is completely determined by the residence time distribution function,/(f). By finding the optimal/(f) for a specified reactor network objective, one can solve the synthesis problem in the absence of mixing. 

After selecting the chromatographic system the operation mode of the batch reactor has to be chosen. High productivities require a high throughput. Therefore, pulsed operation is used (Fig. 8.8). Reactants are supposed to be injected as a rectangle pulse of period tcic le and duration tinj. These parameters are strongly affected by the reaction kinetics, reaction stoichiometry and adsorption isotherm. 

This section analyses the second order reaction A + B P taking place in an isothermal CSTR-Separator-Recycle system. When the reactants are completely recycled, feasible operation is possible only if the ratio of reactants in the feed matches exactly the stoichiometry. For this reason, only one reactant feed may be on flow control (/a,o=1), while the feed flow rate of the second reactant (/b,o) must be used to control its inventory. Two possible control structures are discussed (Fig.13.22) flow control of the recycle stream of one reactant, or of the reactor effluent, respectively. 

Table 1. Laboratory Reactor Simulated Exhaust, Cycled about Stoichiometry (Lightoff and Isothermal Tests)...

With some small loss of generality from the Denbigh scheme, we may consider the first step to be first-order in A only. It is desired now to operate an isothermal batch reactor at a single temperature level to produce a maximum of the intermediate product Q in such a case. Aside from the first step, orders correspond to stoichiometry... 

The reactor described in problem lb, Chapter 4, is to be used for the reaction A + B C + D, with order corresponding to stoichiometry. Predict the conversion at the outlet under isothermal conditions and compare it with that for a PFR of the same average residence time. The following parameters apply... 

E. F. Restelli and J. CouU [AIChEJ., 12, 292 (1966)] studied the transmethylation reaction of dimethylamine in a differential flow reactor using montmoriUonite as a catalyst. They measured initial reaction rates at steady state under isothermal conditions for this heterogeneous catalytic process. The stoichiometry of the initial reaction is... 

Dehydrogenation of ethylbenzene to styrene is normally accomplished in a fixed-bed reactor. A catalyst is packed in tubes to form the fixed bed. Steam is often fed with the styrene to moderate the temperature excursions that are characteristic of adiabatic operation. The steam also serves to prolong the life of the catalyst. Consider the situation in which we model the behavior of this reactor as an isothermal plug flow reactor in which the dehydrogenation reaction occurs homogeneously across each cross section of the reactor. The stoichiometry of the primary reaction is... 

Various parameters must be considered when selecting a reactor for multiphase reactions, such as the number of phases involved, the differences in the physical properties of the participating phases, the post-reaction separation, the inherent reaction nature (stoichiometry of reactants, intrinsic reaction rate, isothermal/ adiabatic conditions, etc.), the residence time required and the mass and heat transfer characteristics of the reactor For a given reaction system, the first four aspects are usually controlled to only a limited extent, if at aH, while the remainder serve as design variables to optimize reactor performance. High rates of heat and mass transfer improve effective rates and selectivities and the elimination of transport resistances, in particular for the rapid catalytic reactions, enables the reaction to achieve its chemical potential in the optimal temperature and concentration window. Transport processes can be ameliorated by greater heat exchange or interfadal surface areas and short diffusion paths. These are easily attained in microstructured reactors. 

Hydrogenation of citral was selected as an example, because it nicely illustrates a case with complex stoichiometry and kinetics, which is typical for fine chemicals. The stoichiometric scheme is displayed in Fig. 4. The reaction system is relevant for the manufacturing of fragrancies, since some of the intermediates, name citronellal and citronellol have a pleasant smell. Thus the optimization of the product yield is of crucial importance. Isothermal and isobaric experiments were carried under hydrogen pressure in the monolith reactor system at various pressures and temperatures (293-373K, 2-... 

The concentration of C when = 0.20mol/l can be calculated from stoichiometry. The total allowable batch time (itot) can be calculated from the requited annual production. The allowable reaction time tieact is ttot — 16. A value of ktjeaci can be calculated fromEqn. (4-12) since die reactor is isothermal and the final value of Ca (0.20 mol/1) is known. Since is known, the necessary value of... 

The process flow sheet for a PFR in Aspen Plus is constructed in the same way as previous examples. In the data browser, specify the feed stream properties. Specify inlet reactions stoichiometry and parameters as shown in Figure 5.48 for the first reaction. For the thermodynamic data, Peng-Robinson is selected. The reactor is considered isothermal. The process flow sheet and stream property table are both shown in Figure 5.49. 

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