Competitive Parallel Reactions

Competitive Parallel Reactions. Competitive parallel reactions are those in which two or more reactant species compete for yet another reactant for example,... 

Parallel reactions Competition Expansion of analyte spectrum Glucose measurement with low interference of... 

Parallel reaction Competition elimination, New analyte specificity... 

The kinetic mechanisms can contain basically three types of reactions in series, in parallel, and independent [2]. In parallel reactions (competitive reactions), the reagent is consumed by two different reaction paths to form different products ... 

Tipnis, S. K., Penny, W. R., and Fasano, J. B., An experimental investigation to determine a scale-up method for fast competitive parallel reactions in agitated vessels, AIChE Annual Meeting, St. Louis, November 1993. 

The study of relative rates by the competitive method can be useful. The principle was discussed in Section 3.1 in the context of parallel reactions, for which the ratio of the product concentrations is equal to the ratio of rate constants (provided the concentrations are under kinetic control). 

The competitive and non-competitive inhibitors are easily distinguished in a Lineweaver-Burk plot. The competitive inhibitor intercepts on the Mv axis whereas the non-competitive inhibitor intercepts on the 1/5 axis. The reaction of inhibitors with substrate can be assumed as a parallel reaction while the undesired product is formed along with desired product. The reactions are shown as ... 

That the reaction with a lower rate constant is taking place preferentially and that the rate increases during the reaction are phenomena that can also occur with parallel reactions. As an example, Wauquier and Jungers (48), when studying competitive hydrogenation of a series of couples of aromatic hydrocarbons on Raney-nickel, have observed these phenomena for the couple tetraline-p-xylene (Table I). The experimental result was... 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

The second method is termed ad eosdem competition— to the same (products, plural) . Consider the solvolysis of 4-chlorobenzyne by methoxide ions and methanol. The nucleophile adds to one end or the other of the triple bond. Because of the 4-chloro substituent, both meta and para isomers are formed. Thus, there are four parallel reactions ... 

Equation 4.2.27 may be rejected even if it provides a parallel path competitive with the mechanism described above because its presence would require a second-prder term in the experimental reaction rate expression. 

In the case of competitive parallel reactions one has the option of studying each reaction independently by varying the composition of the initial reaction mixture. If a chemical species... 

Illustrations 5.3 and 5.4 indicate how one utilizes the concepts developed in this section in the determination of kinetic parameters for competitive parallel reactions. 

These reactions are competitive parallel reactions that are each first-order in the competitive species. Equation 5.2.61 is applicable. 

The form of equations A and B differs from the competitive parallel reactions considered in Section 5.2.1.2. It will be necessary to derive appropriate equations for use in the course of our analysis. 

Fig. 16. The yield Xg of the product Q of the slower reaction of a set of two competitive parallel reactions in a fed batch reactor plotted vs. impeller speed (in /s). The experimental data are due to Bourne and Yu (1991) the crosses refer to feeding reactant A at the top of the vessel, while the diamonds refer to feeding more closely to the impeller. The various types of lines refer to simulations as specified in the legend. Reproduced with permission from R. A. Bakker (1996).

In order to implement the PDF equations into a LES context, a filtered version of the PDF equation is required, usually denoted as filtered density function (FDF). Although the LES filtering operation implies that SGS modeling has to be taken into account in order to capture micromixing effects, the reaction term remains closed in the FDF formulation. Van Vliet et al. (2001) showed that the sensitivity to the Damkohler number of the yield of competitive parallel reactions in isotropic homogeneous turbulence is qualitatively well predicted by FDF/LES. They applied the method for calculating the selectivity for a set of competing reactions in a tubular reactor at Re = 4,000. 

As briefly discussed in Section 1.2, chemical-reaction engineers recognized early on the need to predict the influence of reactant segregation on the yield of complex reactions. Indeed, the competitive-consecutive and parallel reaction systems analyzed in the previous section have been studied experimentally by numerous research groups (Baldyga and Bourne 1999). However, unlike the mechanical-engineering community, who mainly focused on the fluid-dynamics approach to combustion problems, chemical-reaction... 

Note that the definition of max is different for the competitive-consecutive and parallel reactions. 

The two routes (one is Eqs. 2-37b and 2-37c the other is Eqs. 2-37a and 2-37d) together constitute a complex reaction system that consists simultaneously of competitive, consecutive and competitive, parallel reactions. 

We used for Table I the rate constants (16), no - = 3.9 X 109, ke+ NO — = 9.0 X 109, ke+ HjO+ = 2.0 X 1010 and acetone = 5.2 X 109 M 1sec.-1 (slightly corrected [e.g. see (45) ] for other parallel reactions, when such corrections had been neglected (17,20, 27, 52)). The values (16), of ke ferricyanide needed no correction of that type. These rate constants have been used in combination with competition work to calculate the rate constants in both columns 4 and 5. In column 5, the results have been calculated for zero ionic strength using the expression M1/2... 

Knight CS. Experimental investigation of the effects of a recycle loop/static mixer/ agitated vessel system on fast, competitive-parallel reactions. PhD dissertation, University of Arkansas, 1994. 

According to the works by Bourne et al. [162, 163], the azo coupling reactions between a-naphthol (A) and diazotized sulfanilic acid (B) to produce monoazo dye (R) and bisazo dye (S) are used as the competitive-consecutive (series-parallel) reaction scheme for the determination of micromixing, for which the rate constants have been determined [163], and their values at 298 K are... 

P 35] A reaction system with two competitive parallel reactions was used for mixing characterization [36], The Dushman reaction involves the mixing of iodate, iodide and sodium acetate in one solution and a strong acid such as sulfuric acid or hydrochloric acid in another solution. If mixing is fast, the neutralization of the acid and the base dominates as the faster reaction. The redox reaction of iodide and iodate then is a slow process nearly no iodine is formed as the redox product... 

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