Reactant Feed

2 Reactant Feed - The theoretical work of Reyes et al. leads us to expect that when comparing reactant feed PBMR with the co-fed PFR for partial oxidation or similar reactions, the PBMR can give higher yields, but only in a much larger reactor. When equal size reactors are compared, the decrease in conversion due to the lower reaction rate in the PBMR offsets the increase in selectivity due to the favorable kinetics. This has been shown in general and for OCM specifically.  

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The thermal catalytic route proposed involves heating the fresh reactant feed plus recycle up to 790°C and feeding this material into a M0S2 catalyst fixed-bed reactor operating at 0.1 MPa (1 atm). The route yields a production of H2 almost 50% higher than the decomposition of H2S route. 

Interlock reactant feed charge ed via feed totalizer or weight comparison in charge tank... 

The term V/F for flow reactors is used to evaluate the size of the reactor required to achieve the conversion of a reactant feed rate F. It is the numher of reactor volumes of feed at specified conditions that can he treated in unit time, where F is the molar flowrate (uC q) and V is the volume of the reactor. 

Procedural The same reactor described in Example 3 above, but without the 5 psig high pressure interlock. Instead, the operator is instructed to monitor the reactor pressure and stop the reactant feeds if the pressure exceeds 5 psig. There is a potential for human error, the operator failing to monitor the reactor pressure, or failing to stop the reactant feeds in time to prevent a runaway reaction. 

The effects of reactant feeding methods on toluene nitrations were studied by Yamasue et al (Ref 70) in a 15 liter nitrator with a 500rpm agitator. Production of pu re MNT or DNT was favored by addition of acid to the toluene or MNT, while in the production of TNT the addition of oil to acid is to be preferred, provided sufficient cooling and agitation is available. Purest TNT was produced when the MA contained free S03... 

As stated in the previous section, the major reactant feed was chosen as the manipulated variable. In the trial this feed was subjected to a pseudo-random binary sequence (PRBS) signal in an open loop operation of the process. The results of the trial, plotted in Fig. 2, show a strong -- but delayed -- cross-correlation between the manipulated feed rate and the reactor temperature. Using techniques described by Box and Jenkins (2), a transfer function relating the manipulated variable to the control variable of interest can be developed. The general form of this transfer function is... 

Membranes in catalysis can be used to improve selectivity and conversion of a chemical reaction, improve stability and lifetime of the catalyst, and improve the safety of operation. The most well-known example is in situ removal of products of an equilibrium-limited reaction. However, many more ways of application of a membrane can be thought of [1-3], such as using the membrane as a reactant distributor to control the reactant concentration levels in the reactor, or performing catalysis inside the membrane and having control over reactant feed and product removal. 

Fig. 4. Reformer outlet profile with reactant feed rate change by 10% at 1 sec.

The inlet methanol molar concentration was determined by the mass of catalyst, S/C ratio, and W/F ratio. Here, steam-to-carbon (S/C) ratio is defined as the ratio of steam molecules per carbon atom in the reactant feed and W/F ratio as the amount of catalyst loading into the channel divided by the amount of methanol molar flow rate. For more information on the design parameters, physical properties, and operating conditions, refer to Jung et al. [12]. 

Run Amount of reactants Feed time Batch Temperature Feed-rate... 

There are many parameters influencing the size-related performance of a reactor where feed mixing is important concentrations of reactants, feed flow rate, feed pipe velocity, geometry and size of both reactor and stirrer, and stirrer rotational speed. The following remarks should be kept in mind when composing an experimental program for engineering studies ... 

For the instantaneous reaction, the rate is equal to the reactant feed rate. The energy balance then becomes... 

Figure 3 suggests that an unsymmetrical cycle with the duration of air flushing twice the duration of reactant feed would provide even greater reduction of S02 emissions. The drawback of unsymmetrical cycling is that more than two catalyst beds in parallel are needed. An alternative would... 

The split-fractions for the reactants can be calculated directly from the percentage conversion. The conversion may be dependent on the relative flows of the reactants (feed composition) and, if so, iteration may be necessary to determine values that satisfy the feed condition. 

In these equations, x is the instantaneous value of any control variable at any space or time t.x0 is the initial value and xF is the final value of the control variable. In principle, x can be any control variable such as temperature, reactant feed rate, evaporation rate, heat removed or supplied, and so on. tfotai is the total distance or time for the profile. The convexity and concavity of the curves are governed by the values of a and a2. Figures 3.14a and b illustrate typical forms of each curve. 

In principle one can treat the thermodynamics of chemical reactions on a kinetic basis by recognizing that the equilibrium condition corresponds to the case where the rates of the forward and reverse reactions are identical. In this sense kinetics is the more fundamental science. Nonetheless, thermodynamics provides much vital information to the kineticist and to the reactor designer. In particular, the first step in determining the economic feasibility of producing a given material from a given reactant feed stock should be the determination of the product yield at equilibrium at the conditions of the reactor outlet. Since this composition represents the goal toward which the kinetic... 

The effect of mass velocity on the conversion rate was studied by using a tube of fixed diameter that was filled with a sample of a given catalyst diameter to give beds with volumes of either 10 or 20 cm3. At a constant ratio of catalyst weight to reactant feed, this method of varying the bed volume has the effect of varying the mass velocity through the bed. 

Figure 5.3. Basic flow-sheets of a) a conventional, homogeneously catalyzed process and b) an aqueous-biphasically, homogeneous catalytic process. 1, Reactor 2 Separators) 3, Catalyst separator 4, Make-up 5, Further purification and processing, Gas recycles) 7, Catalyst recycle 8, Reactant feed 9, Withdrawal of high...

Generally, the absolute magnitude of Q is not as important as the ratio leak rate to the total flow rate Qieaf/QtotJ. The leakage rate given by Equation (5.4) is the volume flow rate at the temperature and pressure of the leakage flow, and must be corrected to standard conditions for comparison with reactant feed rates. The total required flow rate of fuel or air to the stack is proportional to the stack current, which increases with the electrochemically active area and is inversely proportional to the cell area specific resistance (R"). 

The comparison of catalytic properties was made under identical reaction conditions, among three important candidate catalysts, namely, the Pt/y-Al203, Au/a-Fe203, and Cu Ce, x02 y systems [50], The catalytic tests were performed in the reactant feed containing CO, H2, C02, and HzO — the so-called reformate fuel. The effects of the presence of both C02 and H20 in the reactant feed on the catalytic performance (activity and selectivity) of these catalysts as well as their stability with time under reaction conditions have been studied. The composition of the prepared samples and their BET specific surface areas are presented in Table 7.6. The results obtained with the three catalysts in the presence of 15 vol% COz and of both 15 vol% COz and 10 vol% H20 in the reactant feed (with contact time wcat/v = 0.144 g sec/cm3 and X = 2.5) are shown in Figure 7.12. For comparison, the corresponding curves obtained under the same conditions but without water vapor in the feed are also shown in Figure 7.12. 

Figure 7.12 Variation of the CO and 02 conversion and of the selectivity with the reaction temperature for the selective oxidation of CO at mcat/v = 0.144 g sec/cm3 and A = 2.5 over the Au/a-Fe203 (A), CuO-Ce02 (O), and Pt/y-AI203 ( ) catalysts in the presence of 15 vol% C02 (solid lines) and in the presence of both 15 vol% C02 and 10 vol% H20 in the reactant feed (dotted lines). (Reprinted from [50], With permission from Elsevier.)...

Too much, and the cell will flood too little, and the cell membrane will dehydrate. Both will severely degrade cell performance. The proper balance is achieved only by considering water production, evaporation, and humidification levels of the reactant gases. Achieving the proper level of humidification is also important. With too much humidification, the reactant gases will be diluted with a corresponding drop in performance. The required humidification level is a complex function of the cell temperature, pressure, reactant feed rates, and current density. Optimum PEFC performance is achieved with a fully saturated, yet unflooded membrane (47). 

Figure 19. Battelle s methanol specific reforming catalyst. Reactor conditions atmospheric pressure, reactant feed 50 50 by weight methanol and water mixture, 24 000— 50 000 ii GHSV. The conversion was reported as moles methanol reacted/moles methanol fed. (Reprinted with permission from ref 91. Copyright 2002 Elsevier.)...

Figure 11, Time on stream dependence of (a) phenol conversion and 2-ethyl phenol selectivity and (b) 2-ethyl phenol yield at 3750C on Cul -xCoxFe204 (x = 0.0, 0.5 and 1.0). Reactant feed ratio of EtOFI PhOH = 5 1 was used with a WHSV = 0.869 h-1. Conversion and selectivity is denoted by open and solid symbols, respectively. Note an increase in 2-ethyl phenol selectivity with increasing TOS on all catalyst compositions.

Crystallization of magnesium hydroxide by a continuous mixed suspension mixed product removal crystallizer was conducted to make clear the characteristics of reactive crystallization kinetics of magnesium hydroxide, which was produced by the precipitation from magnesium chloride with calcium hydroxide. The following operating factors were investigated affecting the crystallization kinetics the initial concentration of feeds, residence time of reactants, feed ratio of reactants, and concentrations of hydroxide and chloride ions. 

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