Feed partial pressure

Fig. 12. Temperature-swing cycle (4). Loading at and feed partial pressure A2 at the higher and the lower needed in the product (1).

Figure 4.41. Effect of Ag/YSZ catalyst potential, work function and feed partial pressure of dichloroethane on the selectivity to ethylene oxide (a) and to acetaldehyde (b). T=270°C, P=500 kPa, 8.5% 02,7.8% C2H4.77 Reprinted with permission from Academic Press.

For the complete vapor-phase oxidation of methane over a palladium alumina catalyst, conversion-space-time data were taken at 350°C and 1 atm total pressure the fractional factorial design of Table X (Hll) specified the settings of the feed partial pressures of the reacting species. 

The coke content of the catalyst in all experiments was observed to increase with temperature as expected, but at high temperatures and high feed partial pressures,... 

Activity. The differences found in activity of the catalyst are caused by two effects the definition of the catalyst-to-oil (CTO) ratio and the feed partial pressure in both reactors. The CTO is time averaged over the reaction time and is not clearly defined in the MST. The contact between the catalyst and oil is not constant throughout the experiment. At the beginning of the MST experiment fresh feed encounters fresh catalyst. However, after some time fresh feed meets a partially deactivated catalyst with coke already deposited on it. At the end of the experiment the situation is the opposite of the contact between catalyst and oil in an industrial unit. This makes the definition of the CTO not unambiguous in the case of the MST and can lead to over- or underestimation of the CTO. However, the most important effect is the difference in partial pressure of the feed in both sets of equipment the nitrogen carrier gas lowers the partial pressure in the MR. A lower partial pressure results in a lower conversion. With these two effects a higher activity for the MST can be expected. 

Figure 24. (a) Peimeadon flux of n-butane (u) through a silicalite-1 membrane as a function of the feed partial pressure of n-butane (T=300 K, Ptot=100 kPa). Included are the calculated Fickian (T) (eq.2) and Maxwell-Stefen (v) (eq.l3) difiusivities. 

FIGURE 10.16 n-Cnji-Cn separation performance of a SIL-1 membrane as a function of (a) temperature and (b) 11-C4 feed partial pressure. 

Fig. 1. Thiophene HDS over CoMo/Al O. - feed partial pressure of thiophene...

Tabic 3.3 Kcacting mixture compositions and reaction rates at different points along the reactor tube for the case of steam feed partial pressure that lies on the negative order branch of the rate dependence curve (temperature =. 900 K, total pressure = 2.105 MPa, S/M = 6.0) (From Elnashaie et aJ., 1990). 

The model is used to compute the change of methane conversion at the exit from the reformer tube at different partial pressures of steam in feed to determine the optimum steam feed partial pressure as shown in Figure 3.10. This optimum value is found at a steam partial... 

FIGURE 3.10 Methane conversion at the exit of the reformer tube at different steam feed partial pressure (using the non-isothermal model), partial pressure of methane in feed 0.3 MPa, feed temperature = 900 K, tube skin temperature = 1300 K, Fch = 3kmol/h (case of table 3.6). 

FIGURE 3.11 Proliie of rate of methane disappearance dependence upon steam feed partial pressure and the corresponding exit methane conversion predicted by a one-dimensional heterogeneous model, operating conditions are given as follows tube length/O.D./LD. 11.95/ 0.102/0.0795 m feed composition for point a (mol%) 12.98,... 

It is of interest and practical importance to show the situation where different feeds are introduced to the model with different steam partial pressures while the feed partial pressures of the other components are kept constant, which means of course, a change of the total pressure. The steam reformer tube chosen for simulation is 5 m long to illustrate the kinetic effects rather than the thermodynamic equilibrium effect since the assumption of constant temperature along the tube causes a fast approach to thermodynamic equilibrium of the mixture. 

The methane conversion at the exit of the 5 m reformer tube is obtained for each feed and plotted versus the corresponding steam partial pressure in feed as shown in Figure 3.9. In this figure it is clear that an optimum methane overall conversion can be obtained at a steam feed partial pressure of 0.9 MPa (which corresponds to S/M = 3 and P (total) - 1.205 MPa), although this feed composition does not give maximum reaction rate at the entrance. 

From the above discussion it can be concluded that the close approach to the maximum rate point on the rate dependence curve at the entrance of the reformer tube gives higher initial rate of reaction but at the same time gives faster approach to the positive order region where the order of reaction drops sharply. This means that there is always an optimum steam feed partial pressure that gives maximum reactor performance (expressed in terms of methane conversion) and this optimization problem is a result of the non-monotonic dependence of the rate of reaction upon steam partial pressure. 

The optimum feed partial pressure of steam that gives maximum onfniit conversion is higher than that giving maximum rate of... 

The non-isothermal case gives optimum steam feed partial pressure which is lower than the isothermal case this optimum feed partial pressure of steam does exist for industrial steam reformers. 

Fig. 8 Coke weight percentage for all reactants at 10% feed partial pressure...

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