Deactivation catalyst data

The catalyst deactivation can be calculated with equation (27). Figure 3.5 shows that the slope of the plot of In(l-x) vs. reaction time is 0.0138 at the beginning of the reaction. If there is no catalyst deactivation, the data of In(l-x) vs. time should follow a straight line. The deviation from this straight line indicates that the total catalyst concentration decreases as the reaction progresses. Using equation (27), the value for a, proportional to total catalyst concentration, can be determined from the conversion X and reaction time. As shown in this figrrre, the value for a becomes 0.0054 at the end of the reaction. 

The coke deactivation exponent n, is typically estimated from riser pilot plant experiments at varying catalyst contact time for different catalyst types. A value of n of 0.2 was found for REY catalyst data base. For USY and RE-USY catalysts n was estimated to be 0.4. 

In a recent study of deactivated resid hydroprocessing catalysts [14] it was concluded that resid catalysts in some situations deactivate under coke control. In this study it was shown that predominantly coke deactivated catalysts had residual activities that were in line with what was expected from the data in Fig. 8, e.g, 12.4% C ( 18.3% on a fresh catalyst basis) reduces the HDS activity to 35%, and 17,5% C (25% C on a fresh catalyst basis) gave a reduction of HDS activity to 22% of fresh catalyst activity. 

Whether the deactivation is separable or non-separable, one normally gets some measure of the activity of a deactivating catalyst by comparing the conversion at zero time to the conversion at some later time. The utility of this type of activity depends in part upon the goal of the study and how fundamentally the data are to be interpreted. For example, the integral reactor shown in Figure 1 is frequently used in pilot plant scale operations and can often produce data of value to interpret and... 

This difficulty too can be obviated by decreasing the flow rate to just compensate for the decrease in activity owing to catalyst deactivation. To accomplish this, it is necessary to incorporate some device to sense conversion in a recycle reactor as shown in Figure 3. The signal from this sensor is then fed back to a motor valve and positions it to follow a flow rate profile in time so that the conversion is maintained constant. This type of reactor provides data on a deactivating catalyst in which the catalyst is exposed to reactant and product concentrations for a particular reaction and temperature that are constant in both space and time. In principle, then, the... 

Kinetic data for Fischer-Tropsch synthesis on unsupported iron catalysts have been obtained as part of an overall study of the deactivation of iron catalysts. Data for unpromoted and potassium-promoted catalysts reacted at 1 aim total pressure are reported. At the reaction conditions used in this study, kinetic parameters for the potassium-promoted catalyst cannot be obtained without effects of deactivation. Reaction o ers in the power-law expression for the unpromoted catalyst are 1.4 and 0.60 for Ph2 and Pco> respectively. The unpromoted catalyst exhibits a deactivation order of 1 when the generalized power-law expression is used. 

Sulfur tolerances of Cu- and H-mordenite zeolite catalysts prepared by ion-exchange were examined in a fixed-bed flow-reactor system. Rates of reduction of NO over HM or CuHM with C2H4 and CuNZA with C3H6 are decreased by SO2 included in the feed gas stream. Surface areas and sulfur contents of the deactivated catalysts, their TGA and TPSR patterns and observations by XPS and Raman suggest the formation of a sulfur species on the catalyst surface in the form of sulfate (SO/ ) which causes the loss of NO removal activity of the catalysts. Data from Cu K-edge absorption spectra suggest sulfur electrostatically interacts with Cu ions on the catalyst surface. 

The activity for oxidative methanol reforming (OMR) as a function of time-on-stream was determined for CuO catalysts supported on ZnO or Zr02- The ZnO-supported samples deactivated more quickly than the Zr02-supported samples during 18 hour reactions at 225 °C. X-ray diffraction characterization showed that copper oxide particle size increases during the reaction, which implied that loss of CuO surface area is a cause of deactivation. The data suggested that the increase in CuO particle size was accompanied by sintering of the support, which was facilitated by the presence of water vapor at elevated temperatures. 

Our study also showed that the catalyst deactivates with time-on-stream even at low conversions. The activity dropped 30% from its initial value over a few hours. The present work further investigates this deactivation phenomenon in order to evaluate more thoroughly the potential application of copper oxide catalysts for OMR. Experiments were conducted to determine the cause of deactivation and the effect of the support on deactivation rate. Zirconia has been explored as an alternative support to ZnO and/or alumina. Reaction and deactivation rate data for 18-hour OMR reactions are reported for these catalysts. 

Fig. 2. Activity of Au/AbOj in CO oxidation at room temperature. Data show that a deactivated catalyst can be regenerated repeatedly by treatment with H2.

Effect of Pressure Figure 3 shows the effect of pressure on product sulfur. In the 400-800 psig range, doubling the pressure reduces the product sulfur by about one third. Pressure also has an effect on catalyst life. In general, as the pressure is increased the catalyst deactivates at a lower rate. However, beyond a certain point, further increases in pressure have only a small effect on deactivation rate. An example of this is for atmospheric resids typical data... 

Table 3 shows the performance of the promoted-catalysts for the decomposition of methane to hydrogen at 5, 60, 120 and 180 min of time on stream. The results in Table 3 revealed that the activity of the parent catalyst and MnOx-doped catalyst remained almost constant until 120 min of time on stream. The activity of the other promoted-catalysts, on the other hand, decreased with an increase in the time on stream. The data for the CoO-doped catalyst and 20 mol%NiO/Ti02 could not be recorded at 120 min and 180 min, respectively because of the pressure build-up in the reactor. This finding indicates that adding MnOx enhances the stability and the resistibility of the NiO/Ti02 catalyst towards its deactivation. 

This data also suggests that operating at 100% CO conversion could only provide transient data, and provide no information on the deactivation of the catalyst. As Figure 1 shows, the catalyst has a high enough activity at the low space velocity of... 

Figure 2 shows the CO conversion as a function of time on stream in the absence of CO2 in the feed on the 5%Au/Co304 at a space velocity of 60,000 hr . In contrast to the data shown in Figure 1, the catalyst showed an initial CO conversion of about 80% and showed considerable deactivation over eight hours. Figure 3 shows the CO conversion as a function of time at 25°C in the presence 5%Au/Co304, and 1%Au/Ti02 catalysts at a space velocity... 

All of the Au/metal oxide catalysts deactivate quickly, under the conditions shown in Figure 4. In addition, the deactivation of the Au/metal oxide catalysts appears to be enhanced in the presence of COj. In support of the theory that increased basicity of the metal oxides leads to lower stability, we carried out COj temperature programmed desorption experiments on the various catalysts. The COj TPD data also confirmed that an increase in the basicity of the metal oxides leads to an increase in the amount of COj adsorption on the catalysts. 

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