Batch reactors about

Figure 6.17.13 shows the results of the simulation of a batch reactor. About 215 h are needed to reach 99% of the equilibrium concentration of menthol. 

Eigure 2 shows that even materials which are rather resistant to oxidation ( 2/ 1 0.1) are consumed to a noticeable degree at high conversions. Also the use of plug-flow or batch reactors can offer a measurable improvement in efficiencies in comparison with back-mixed reactors. Intermediates that cooxidize about as readily as the feed hydrocarbon (eg, ketones with similar stmcture) can be produced in perhaps reasonable efficiencies but, except at very low conversions, are subject to considerable loss through oxidation. They may be suitable coproducts if they are also precursors to more oxidation-resistant desirable materials. Intermediates which oxidize relatively rapidly (/ 2 / i — 3-50 eg, alcohols and aldehydes) are difficult to produce in appreciable amounts, even in batch or plug-flow reactors. Indeed, for = 50, to isolate 90% or more of the intermediate made, the conversion must... 

The differential reactor is the second from the left. To the right, various ways are shown to prepare feed for the differential reactor. These feeding methods finally lead to the recycle reactor concept. A basic misunderstanding about the differential reactor is widespread. This is the belief that a differential reactor is a short reactor fed with various large quantities of feed to generate various small conversions. In reality, such a system is a short integral reactor used to extrapolate to initial rates. This method is similar to that used in batch reactor experiments to estimate... 

The rate of polymerization with styrene-type monomers is directly proportional to the number of particles formed. In batch reactors most of the particles are nucleated early in the reaction and the number formed depends on the emulsifier available to stabilize these small particles. In a CSTR operating at steady-state the rate of nucleation of new particles depends on the concentration of free emulsifier, i.e. the emulsifier not adsorbed on other surfaces. Since the average particle size in a CSTR is larger than the average size at the end of the batch nucleation period, fewer particles are formed in a CSTR than if the same recipe were used in a batch reactor. Since rate is proportional to the number of particles for styrene-type monomers, the rate per unit volume in a CSTR will be less than the interval-two rate in a batch reactor. In fact, the maximum CSTR rate will be about 60 to 70 percent the batch rate for such monomers. Monomers for which the rate is not as strongly dependent on the number of particles will display less of a difference between batch and continuous reactors. Also, continuous reactors with a particle seed in the feed may be capable of higher rates. 

Two additional results were noted during this series of experiments. It was found that plugging of the reactor occurred when the conversion reached about 60%. No satisfactory explanation or cause for the plugging was determined. It was also noted that, regardless of the rate of polymerization, no further reaction occurred after a period of about 60 to 75 minutes. This is in contrast to reaction times of up to three hours for the same recipe used in a batch reactor. 

OS 41a] ]R 19] ]P 30] Ten different substrates (C4-C8 alcohols) were reacted with rhodium(I)-tris(fn-sulfophenyl)phosphane [110]. The variance in conversions (ranging from about 1-62%) determined was explained by differences in the solubility of the alcohols in the aqueous catalytic layer and by their different intrinsic activities. Chain length and steric/electronic effects of the different alcohols affected their reactivity in a well-known pattern (Figure 4.63). The results obtained correspond to the conversions achieved in a well-mixed traditional batch reactor (40 cm ). They further agreed with data from mono-phasic processing. 

We now consider operation of the batch reactor under adiabatic conditions. We will assume that we need not worry about reaching the boiling point of the liquid and that the rate of energy release by reaction does not become sufficiently great that an explosion ensues. 

The liquid hydrocarbon stream to be treated may be a crude oil, heavy crude oil, bitumen, or a refined fraction of the crude oil. The hydrogen gas stream is added to the mixture of the hydrocarbon stream with the organic solvent. The reactor, which is fed upflow, is a packed bed of biocatalyst dispersed on a support and is operated at about 74°C. Alternatively, the reactor can also be a batch reactor under stirring conditions. 

The kinetics results of the batch reactor runs lead to the following qualitative observations At low CO pressures (less than about 1 atm) the catalysis appears to be first order in ruthenium over the range 0.018 M to 0.072 M and also in Pco as illustrated by the log Pco vs time plots of Fig. 2 and also shown by the method of initial rates. Changes in the sulfuric acid and water concentrations over the respective ranges 0.25 M to 2.0 M and 4 M to 12 M have relatively small effects on the catalysis rates, although the functionalities are complicated and show concave rate vs concentration curves with maximum rates... 

Ford et al.60 also made a significant contribution to the metal carbonyl catalyzed shift reaction in acidic medium. A solution of Ru3(CO)i2 (0.006-0.024 M with 0.25-2.0 M H2S04 4.0-12.0 M H20) in 5 ml of diglyme had good catalytic activity at 100 °C. They used a batch reactor with Pqo = 0-9 atm. Typical H2 turnover activity was reported to be about 50 turnovers per day. Their in situ spectroscopic studies show that the principal component was HRu2(CO)8-. They found that, at low CO partial pressures (< 1 atm), the catalysis was first order in Ru. However, at high CO partial pressures, the rate was inhibited. On the basis of their studies, they proposed the catalytic cycle outlined in Scheme 15. 

This system was studied by Schwartz. Toluene at 10 ppm, nitric oxide at 1 ppm, and nitrogen dioxide at 1.2 ppm were irradiated with ultraviolet lamps in a 17-m batch reactor for 270 min. Collected aerosols were successively extracted with methylene chloride and then methanol. The methylene chloride extract was fractionated into water-soluble and water-insoluble material, and the latter fraction was further divided into acidic, neutral, and basic fractions. The acidic and neutral fractions were analyzed by gas chromatography and chemical-ionization mass spectrometry the compounds identified are shown in Figure 3-7. The two analyzed fractions represented only about 5.5% of the total aerosol mass. It is noteworthy that classical nitration of an aromatic ring appears to... 

For an autocatalytic reaction in a batch reactor some product R must be present if the reaction is to proceed at all. Starting with a very small concentration of R, we see qualitatively that the rate will rise as R is formed. At the other extreme, when A is just about used up the rate must drop to zero. This result is given in Fig. 3.9, which shows that the rate follows a parabola, with a maximum where the concentrations of A and R are equal. 

Make a material balance for any component A. For such an accounting we usually select the limiting component. In a batch reactor, since the composition is uniform throughout at any instant of time, we may make the accounting about the whole reactor. Noting that no fluid enters or leaves the reaction mixture during reaction, Eq. 4.1, which was written for component A, becomes... 

The following data on an irreversible reaction are obtained with decaying catalyst in a batch reactor (batch-solids, batch-fluid) What can you say about the kinetics... 

Berset J.D., T. Kupper, R. Etter, and J. Tarradellas (2004). Considerations about the enantio-selective transformation of polycyclic musks in wastewater and sewage sludge and analysis of their fate in a sequencing batch reactor plant. Chemosphere 57 987-996. 

Introductory textbooks in kinetics or chemical engineering describe how to determine the reaction order of a reaction from experimental data. Typically an assumption about reaction order is made, and this assumption is subsequently tested. Imagine that experimental data for the consumption of reactant A as function of time is available from experiments in a batch reactor. Initially we assume that A is consumed according to a first-order reaction,... 

This type of segregation, which may be considered as a microscale segregation, appears to be a state which in itself does not say anything about the concentration in the dispersed particles nor about their age. In a batch reactor, for instance, in which all the dispersed particles have the same size, there may be complete segregation (no interaction) and still all the particles will always have the same concentration. 

In calculating the volume required for a batch reactor, we shall be specifying the volume of liquid which must be processed. In designing the vessel itself the heights should be increased by about 10 per cent to allow freeboard for waves and disturbances on the surface of the liquid additional freeboard may have to be provided if foaming is anticipated. 

In another example of differential heating, a two-phase water/chloroform system (1 1 by volume) was heated in a microwave batch reactor (MBR)65. About 40 s after commencement, the temperatures of the aqueous and organic phases were 105 and 48°C, respectively, because of the differences in the dielectric properties of each solvent. A sizeable differential could be maintained for several minutes before cooling was begun. Differential heating is particularly advantageous for Hofmann eliminations. In a typical example,... 

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