Reactor performance series reactions

Example 4.10 Consider a reactor train consisting of a CSTR followed by a piston flow reactor. The total volume and flow rate are fixed. Can series combination offer a performance advantage compared with a single reactor if the reaction is autocatalytic The reaction is... 

Another advantage of Liquid Recycle is that multiple reactors may be arranged in series with the effluent from one passing on to the next. The alkene concentration is less in the downstream reactors, but reaction conditions can be adjusted to optimize each reactor s performance. In back mixed reactors in continuous operation, the effluent from the reactor is the same as the catalyst solution throughout the reactor. By placing reactors in series, the first reactor can be optimized for high rates and later reactors for high conversion. 

The continuous polycondensation process consists of four main process units, i.e. (1) slurry preparation vessel, (2) reaction unit, (3) vacuum system, and (4) distillation unit. The molar EG/TPA ratio is adjusted to an appropriate value between 1.05 and 1.15 in the slurry preparation vessel. In most industrial processes, the melt-phase reaction is performed in three up to six (or sometimes even more) continuous reactors in series. Commonly, one or two esterification... 

An automated H-Cube platform was designed, constructed and validated by Clapham et al. [26], to perform deprotection reactions and produce compound libraries. This special instrument includes 48 starting material vials for automated injection into the flow reactor. In producing the Cbz deprotected library, complete conversions and a 93% average crude yield were obtained over Pd/C catalyst at 60°C using full hydrogen mode. For the second library, 4-benzyloxy benzoic acid was coupled with a series of amides. The deprotection performed in H-Cube resulted in eomplete conversions to the products and 88% average crude yield. 

With Eqs. 6b and 7 we can compare performance of N reactors in series with a plug flow reactor or with a single mixed flow reactor. This comparison is shown in Fig. 6.5 for first-order reactions in which density variations are negligible. 

To investigate the behaviour of the present reactor, a series of steady state and dynamic experiments were performed, consisting of reactor start-up, step changes in feed composition and ramp changes in feed and jacket temperature. Heat transfer experiments without reaction were also performed. Some of the results are compared with model simulations, using, whenever possible, a priori values of model parameters. 

Conventional technology, which has been employed for over 25 years, uses three or four fixed bed reactors in series, these operating under adiabatic conditions. They are preceeded by heating furnaces that compensate for the overall endothermicity of the reaction. Catalyst performance was investigated separately in a pilot plant under isothermal conditions, employing ca. 300-400 g of catalyst. 

An RTD, however, does not represent the mixing behavior in a vessel uniquely, because several arrangements of the internals of a vessel may give the same tracer response, for example, any series arrangements of reactor elements such as plug flow or complete mixing. This is a consequence of the fact that tracer behavior is represented by linear differential equations. The lack of uniqueness limits direct application of tracer studies to first-order reactions with constant specific rates. For other reactions, the tracer curve may determine the upper and lower limits of reactor performance. When this range is not too broad, the result can be useful. Tracer data also may be taken at several representative positions in the vessel in order to develop a realistic model of the reactor. 

Heavy Oil Preparation and Separation. Hydrogenation of Hiawatha, Utah, coal [C 72.0 H 5.6 N 1.7 S 0.90 O 19.8 dry, ash-free (DAF) %] was performed at a reaction temperature of 510°C and 12.4-MPa hydrogen pressure with ZnCl2 impregnated on the coal as catalyst in an entrained-flow, tubular coil reactor (10). The reaction products were trapped in three reservoirs connected to the reactor in series and were separated according to their condensability. Heavy-oil products collected in the first reservoir, nearest to the reactor, were used in this study. 

Next, we consider series (consecutive) chemical reactions. These are reactions where the product of one reaction reacts to form undesirable species. In such cases, it is important to consider the amount of desirable and undesirable products formed in addition to the conversion of the reactant. In many instances, the yield of the desirable product provides a measure of the reactor performance. 

Computational fluid dynamics (CFD) has emerged as a very valuable tool in modeling the real flow patterns in chemical reactors. It represents a quantum leap from the idealized reactor models or their modifications, such as the tanks-in-series or axial-dispersion models to account for nonidealities. It has the potential to account for flow and reactions inside a reactor in their entirety. CFD has been used successfully to predict the flow patterns and reactor performance in the case of reactions involving macro-mixing effects. 

The flexibility of enzyme gel layer reactors is fully exploited when multi-enzymatic reactions are to be performed. It may happen that enzymes involved in a given transformation cannot be subjected to the same immobilization procedure. Sequential enzyme gel layers can then be built up on the surface of a membrane in the proper sequence. Series reactions can be performed in such a set-up products from one enzymatic layer being fed to the following ones for further transformation.28 41... 

The influence of dispersion on the yield of an intermediate produced in a series of consecutive reactions has also been studied. When Tt /uL is less than 0.05, Tichacek s results (22) indicate that the fractional decrease in the maximum amount of intermediate formed relative to plug flow conditions is approximated by T) /uL itself. Results obtained at higher dispersion numbers are given in the original article. Douglas and Bischoff (23) considered the influence of volumetric expansion effects on the yields obtained with dispersion. Illustration 11.6 indicates how the longitudinal dispersion model may be used to predict reactor performance. 

Thomas, S., Pushpavanam, S. and Seidel-Morgenstem, A., 2004. Performance Improvements of Parallel-Series Reactions in Tubular Reactors Using Reactant Dosing Concepts. Industrial ... 

In the case of known formal kinetics, the reactor performance can be determined directly from the RTD. We can imagine, for example, that the RTD in the reactor under consideration can be represented by a series of ideal plug flow reactors of different lengths arranged in parallel through which the reaction mass flows at equal rates (see Figure 3.17). 

The global transformation rate of a gas-liquid reaction catalyzed by a solid catalyst is influenced by the mass transfer between the gas-liquid and the liquid-solid. The two mass transfer processes and the surface reaction are in series and for fast chemical reactions, mass transfer will influence the reactant concentration on the catalytic surface and, as a consequence, influence the reactor performance and the product selectivity. Compared to gas-solid catalytic reactions as discussed in Section 2.5, an additional resistance in the liquid must be considered (Figure 8.5). 

More recently, Hooper and Watts [9] investigated the incorporation of deuterium labels into an array of small organic compounds via the base-mediated acylation of primary amines. Unlike the previous examples described here, the use of acetic-ds anhydride proved undesirable as it led to the generation of acetic-ds add as the byproduct, a problem that was circumvented through the use of acetyl-d3 chloride (Scheme 3.6). To perform a reaction, the authors employed two borosilicate glass microreactors coimected in series (reactor 1 = 201 pm wide x 75 pm deep x 2.0 cm... 

After extracting the kinetic parameters, selected results for CO oxidation over were used to analyze the effect of non-uniform temperature and velocity distributions on the conversion of CO. In order to determine the optimum number of multiple CSTR s to capture the behavior of a PFR, the rate law of Oh and Carpenter (14) for the NO+CO reaction was used to model a monolith channel as a CSTR in series. The results indicated that it was sufficient to use 5 reactors in series to capture the performance of the PFR behavior in the NO+CO reaction The cells of a monolith reactor were taken as independent parallel reactors ignoring the mass transfer and diffusion through the ceramic pores. The axial and radial temperature and velocity profiles collected from the literature(4,5) are used to calculate the... 

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