Reaction simultaneous

Reactors in which simultaneous reactions occur are quite similar to the consecutive reactors case in that yield of the desired product is important. But since the same reactants are involved in both reactions, reactant concentrations cannot be as readily adjusted to affect yield. Yield of the desired product depends primarily on reactor temperature and on the kinetics of the two reactions. 

If the desired product is C, reactor temperature should be selected so that the specific reaction rate k of the desired reaction is large compared to the specific reaction rate k2 of the undesired reaction. If the orders of reactions are different in terms of their dependence on the two reactants, the concentrations can also be adjusted to favor the desired reaction  

To illustrate some of these issues, we take a numerical example with the parameters given in Table 2.4. There are four components, so four component balances can be written as follows  

4 Uses fsolve to find steady-state compositions of simultaneous reactions kratio-lO,ko2 ( (49.3e-6)/kratio) exp(139.4e6/0314/333) vr=20Q tr 340  

Example 13.3 Methanol is mostly produced [1,2] by the simultaneous gas-phase reactions 

The typical reactor feed (synthesis gas) is 15 mol% CO, 8 mol% CO2,74 mol% H2, and 3 mol% CH4 which latter is assumed to be inert in this reaction. Estimate the percent conversion in each of the two reactions, and the mol percent methanol at equilibrium. 

These substitutions in terms of ei and 2 reduce the number of unknowns from five to two. The resulting equations can be simplified algebraically and then solved numerically, giving Cl = 0.176, C2 = 0.038, and ycH,OH = 0.272.  

The hydrogen in the feed gas could react with CO and CO2 not only to form methanol, but also to form methane (see Section 12.4). If the catalyst facilitated those reactions in addition to the methanol reactions, then most of the product would be methane. This synthesis of methanol (which is widely used industrially) is possible only because materials have been found that catalyze the methanol reactions at a temperature low enough that the methane reactions do not occur. 

Suppose that the system under consideration undergoes r simultaneous independent reactions. Then instead of the single stoichiometric equation (1.38) we shall now have a set of r equations 

The symbol d n represents the change in the number of moles ni of component i in the time dt, arising from the pth reaction. The rate of the pth reaction is then given by 

The total change in ni as a result of all the r reactions will be given by dni=dpfii- -d ni- -... - -drni-Zdpni, (1 54) 

Example For the system carborn-oxygen +carbon monoxide + carbon dioxide we have two independent reactions 

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To produce a spandex fiber by reaction spinning, a 1000—3500 molecular weight polyester or polyether glycol reacts with a diisocyanate at a molar ratio of about 1 2. The viscosity of this isocyanate-terrninated prepolymer may be adjusted by adding small amounts of an inert solvent, and then extmded into a coagulating bath that contains a diamine so that filament and polymer formation occur simultaneously. Reactions are completed as the filaments are cured and solvent evaporated on a belt dryer. After appHcation of a finish, the fibers are wound on tubes or bobbins and rewound if necessary to reduce interfiber cohesion. 

Silver Catalyst Process. In early formaldehyde plants methanol was oxidized over a copper catalyst, but this has been almost completely replaced with silver (75). The silver-catalyzed reactions occur at essentially atmospheric pressure and 600 to 650°C (76) and can be represented by two simultaneous reactions ... 

Reduction of sulfur dioxide by methane is the basis of an Allied process for converting by-product sulfur dioxide to sulfur (232). The reaction is carried out in the gas phase over a catalyst. Reduction of sulfur dioxide to sulfur by carbon in the form of coal has been developed as the Resox process (233). The reduction, which is conducted at 550—800°C, appears to be promoted by the simultaneous reaction of the coal with steam. The reduction of sulfur dioxide by carbon monoxide tends to give carbonyl sulfide [463-58-1] rather than sulfur over cobalt molybdate, but special catalysts, eg, lanthanum titanate, have the abiUty to direct the reaction toward producing sulfur (234). 

Complex Clieinical-Reaction Equilibria When the composition of an equilibrium mixture is determined by a number of simultaneous reactions, calculations based on equilibrium constants become complex and tedious. A more direct procedure (and one suitable for general computer solution) is based on minimization of the total Gibbs energy G in accord with Eq. (4-271). The treatment here is... 

Simultaneous reactions. The overall rate is the algebraic sum of the rates of the individual reactions. For example, take the three reactions ... 

Example 2 Analysis of Three Simultaneous Reactions Consider the three reactions... 

Reaction and Separation Some multiphase operations combine simultaneous reaction and separation. A Few examples follow. 

Thus in the presence of an excess of NH4+, which suppresses this forward reaction, and counteranions such as NOa" and C104, which have little tendency to coordinate, complexes such as [Hg(NH3)4] +, [Hg(L-L)2] + and even [Hg(L-L)3] + (L-L = en, bipy, phen) can be prepared. But, in the absence of such precautions, amino, or imino-compounds are likely to be formed, often together. Because of this variety of simultaneous reactions and their dependence on the precise conditions, many reactions between Hg and amines, although first performed by alchemists in the Middle Ages, remained obscure until the application of X-ray crystallography and, still more recently, spectroscopic techniques such as nmr, infrared and Raman. 

Ill these simultaneous reactions, die energy released when the complex molecule AB is broken down is immediately used to build a molecule of adenosine triphosphate (ATP) from a molecule of adenosine diphosphate (ADP) and an inorganic phosphate (P,). ATP is a high energy compound. It is called the energy currency of the body because once it is formed, it provides energy that the body can spend later to drive vital reactions in cells (Figure 1). 

As stated earlier, catalytic cracking involves a series of simultaneous reaction.s. Some of these reactions are endothermic and some are exothermic. Each reaction has a heat of reaction associated with it (Table 4-4). The overall heat of reaction refers to the net or combined heat of reaction. Although there are a number of exothermic reactions, the net reaction is still endothermic. 

The investigations have shown, however, that graft copolymerization carried out according to this method is accompanied with a simultaneous reaction of monomer homopolymerization which, naturally, reduces the effectiveness of the method. This is explained by the presence of hydroxyl radicals in the reaction medium, which are formed as formulated in the above scheme. 

It is concluded that a fully satisfactory system for calculating simultaneous reactions of CO and COo with H2 and H20 will require a schedule of the effect of CO on C02 methanation as a function of temperature. This effect will probably be different with different particle sizes. From a commercial standpoint, the particle size range may be too small to require much difference in the treatment of the data, but in the laboratory very small particle size may lower the CO methanation rate. A simple kinetics system such as that derived from Equation 3 may be satisfactory for all the reactions. It is unlikely that reliable data will be collected soon for the shift reaction (since it is of a somewhat secondary nature and difficult to study by itself), and therefore a more complicated treatment is not justified. 

Gill and Nunge (G 16) solved the equation for diffusion accompanied by simultaneous chemical reaction with a changing concentration of the bulk liquid. They assume a film of thickness / in which the diffusion and simultaneous reaction take place, and suppose the liquid bulk outside this film to be completely mixed and to have a constant and uniform concentration. Their partial differential equation in one dimension is... 

A distinction can be drawn between multiple paths to the same product(s) and simultaneous reactions that partition to different ones. Examples of both will be given. 

The simultaneous reaction of sulfur dioxide and chlorine with paraffins, named sulfochlorination, was discovered by Reed and Horn in the 1930s [9]. The primary products of this reaction are the alkanesulfochlorides [10], which can be saponified to alkanesulfonates by sodium hydroxide solution or treated with substituted phenolates to give plasticisers. In a short time the process was industrially realized to secure detergent production during World War II in Germany [11]. 

There are also other routes to esters of phosphorous acid. Esterification of phosphorous acid is possible but this reaction is not economical. A third route is provided by simultaneous reaction of alcohol, phosphorous, and oxygen, often using different partial pressure of oxygen see Eqs. (24) and (25). 

The final conclusion of this short discussion is that electropolymerization is a fast method (a film of about 5 //mean be obtained by polarization in 1 rnin) that uses a complex mechanism (Fig. 12) in which electropolymerization, cross linking, degradation, and chemical polymerization can coexist to produce a mixed material with a cross-linked and electroactive part and a passive fraction.67-71 However, ifwe control the variables acting on the kinetics of the different simultaneous reactions, the complexity also provides flexibility, allowing us to obtain materials tailored for specific applications. 

Thus, there is no great difficulty in accounting for each of the ions in Table IV the problem which remains is that of characterizing the rates and equilibrium constants of the various simultaneous reactions. 

At 1100°C the borate and the hexaboride are formed simultaneously [reaction (b)]. The observed borates are the aragonite type for La, Ce, Nd and the vaterite type... 

The peroxide-initiated, free radical, dispersion polymerization of the single monomer is assumed to progress according to the simultaneous reactions of initiator decomposition, initiation, propagation and termination with appropriate reaction orders described elsewhere.(2-6)... 

The concentration of PB in the reaction products (Table 1) is too high to be accounted for by dehydrogenation of PCHE, especially in the absence of H2S, since at thermodynamic equilibrium the PCH/PB ratio sho lld be greater than 50 (15) under our experimental conditions. Furthermore, no toluene was observed in the simultaneous reaction of methylcyclohexene and DHQ under the same reaction conditions. Therefore, there must be another reaction path to accoimt for the formation of PB in the HDN products of DHQ. This second reaction path can only be the reaction of DHQ->THQl- OPA-> HC. It has been demonstrated that a relatively high concentration of PB is present in the HDN of OPA due to the direct hydrogenolysis of the C(sp-)-N bond of OPA (16). 

The presence of different catalytic sites for the first C-N bond breaking of DHQ and the hydrogenation of CHE is confirmed by the -ln(l-XDiKj) versus -ln(l-X(niK) plot. In the simultaneous reactions of A and B, in which A and B are both adsorbed on the same catalytic site and follow a Langmvtir-Hinshelwood mechanism, we have... 

A plot of In(l-x.A) hi(l-XB) should restUt in a straight line if the assumption is true. Figure 6 shows the resvilt of simultaneous reactions of DHQ and CHE. The curvature of the In(l-XDHq) In(l-xcHE) plot confirms that the adsorption sites for CHE and DHQ over the NiMo(P)/Al203 catalysts are not the same. 

Figure 6. Simultaneous reaction of DHQ and CHE at 623 K, 3.0 MPa, and H2S/H2 = 3.0x10 (mol/mol) over the NiMoP/AbOs catalyst.

After our success in preparation of the colloidal dispersions of Pt-core/Pd-shell bimetallic nanoparticles by simultaneous reduction of PdCl2 and H2PtCl6 in refluxing ethanol/water in the presence of poly(V-vinyl-2-pyrroli-done) [15,16] several reports have appeared on the formation of the core/shell-structured bimetallic nanoparticles by simultaneous reactions [5,52,68,183]. 

An amino-formaldehyde resin or acetone-formaldehyde resin has the capability to harden in alkaline media, in contact with a cement solution with a pH of 11 to 12. The presence of sintered CaO provides the required conditions for hardening of the methylol groups of the formaldehyde resin with Ca + ions and a further simultaneous reaction of the methylol groups that formed hydrate compounds, resulting in an improved dispersion and plastification of the solution. 

Components A and G react by three simultaneous reactions to form three products, one that is desired (D) and two that are undesired (W and U). These gas-phase reactions, together with their corresponding rate laws, are given below. 

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