Fraction conversion

In fact, the fractional conversion of the waste s nitrogen to NO decreases with increa sing nitrogen content (see Fig. 8) (29), as can be understood from the reaction pathway (see Fig. 7). 

Oxidation of cumene to cumene hydroperoxide is usually achieved in three to four oxidizers in series, where the fractional conversion is about the same for each reactor. Fresh cumene and recycled cumene are fed to the first reactor. Air is bubbled in at the bottom of the reactor and leaves at the top of each reactor. The oxidizers are operated at low to moderate pressure. Due to the exothermic nature of the oxidation reaction, heat is generated and must be removed by external cooling. A portion of cumene reacts to form dimethylbenzyl alcohol and acetophenone. Methanol is formed in the acetophenone reaction and is further oxidized to formaldehyde and formic acid. A small amount of water is also formed by the various reactions. The selectivity of the oxidation reaction is a function of oxidation conditions temperature, conversion level, residence time, and oxygen partial pressure. Typical commercial yield of cumene hydroperoxide is about 95 mol % in the oxidizers. The reaction effluent is stripped off unreacted cumene which is then recycled as feedstock. Spent air from the oxidizers is treated to recover 99.99% of the cumene and other volatile organic compounds. 

Equimolal proportions of the reactants are used. Thermodynamic data at 298 K are tabulated. The specific heats are averages. Find (1) the enthalpy change of reaction at 298 and 573 K (2) equilibrium constant at 298 and 573 K (3) fractional conversion at 573 K. 

The temperature T and the time t will be found in terms of fractional conversion x when UA/V = 0 or 150. 

In terms of the fractional conversion and the ideal gas law, the rate equation becomes... 

Example (h) In terms of fractional conversion,/ = 1 — C/Cj, the material and energy balances for a first-order CSTR are ... 

This case includes most liquid reactions and also those gas reactions that operate at both constant temperature and pressure with no change in the number of moles during reaction. The relationship between concentration C and fractional conversion is as follows ... 

Nc = 0.0 gmol, Nq = 0.0 gmol, respectively. A mixture of A and B is charged into a 1-liter reactor. Determine the holding time required to achieve 90% fractional conversion of A (X = 0.9). The rate constant is k = 1.0 X 10 [(liter) /(gmoP min)] and the reaction is first order in A, second order in B and third order overall. 

Since the volume depends on conversion or time in a constant pressure batch reactor, consider the mole balance in relation to the fractional conversion X. From the stoichiometry. 

The mean residence time is evaluated in terms of the fractional conversion as defined by Ca = Caq(1 X )-... 

The fractional conversion is determined from Equation 5-167 in terms of the mean residence time f = (V /u) to yield... 

For a cascade of N CFSTRs of equal volume, Vr, in which the first order forward reaction A—occurs with a throughput u, show that the system fractional conversion is... 

In the above reactions, the fractional conversion is defined as loss of reactant... 

Figure 6-6. Temperature versus fractional conversion profiles for various rates of heat input in a batch reactor.

The first order reaction is represented by (-r ) = kC, and applying the mass balance Equation 6-120 and the heat balance Equation 6-121, respectively, gives the fractional conversion in terms of the mass balance equation ... 

The fractional conversions in terms of both the mass balance and heat balance equations were calculated at effluent temperatures of 300, 325, 350, 375, 400, 425, 450, and 475 K, respectively. A Microsoft Excel Spreadsheet (Example6-ll.xls) was used to calculate the fractional conversions at varying temperature. Table 6-7 gives the results of the spreadsheet calculation and Eigure 6-24 shows profiles of the conversions at varying effluent temperature. The figure shows that die steady state values are (X, T) = (0.02,300), (0.5,362), and (0.95,410). The middle point is unstable and die last point is die most desirable because of die high conversion. 

Fractional conversions (mass and heat balances) at effluent temperatures... 

Using the same values of the kinetic parameters as in Type 1, and given C o = 0-1 mo 1/1, it is possible to solve Equation 6-155 with Equations 6-127 and 6-128 simultaneously to determine the fractional conversion X. A computer program was developed to determine the fractional conversion for different values of (-iz) and a temperature range of 260-500 K. Eigure 6-30 shows the reaction profile from the computer results. 

Fig ure 6-32. Fractional conversion versus T pt for a first order reversible reaction A R. 

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