Reactor conditions during comparisons

REACTOR CONDITIONS DURING COMPARISONS OF TRICKLE AND BATCH OPERATIONS... 

Figure 1. (A) Effect of the titration temperature during Fe-decomplexation exchanged on the N2O decomposition activity using citrate Fe-precursor at ( ) 333 ( ) 353 and (A) 373 K. For comparison, a reference catalyst based on ion-exchange using ferric nitrate (same Fe loading) is included (O). Reaction conditions 4.5 mbar N2O, He balance. (B) Stability test for ( ) in A spot under typical conditions for nitric acid plants in The Netherlands 4.5 mbar N2O + 0.6 mbar NO + 15 mbar H2O + 75 mbar O2. In both cases, total pressure was 3 bar-a and a space time W/F (N20) of 900 kgxsxmoT (W is the catalyst mass and F (N20) the molar flow of N2O in the reactor inlet) was applied.

For the calculation of yields (Y ), the amount of condensed products collected during a time interval (At) is referred to the toluene feed [Eq. 1], Selectivities (S ) are calculated for the condensed products [Eq. 2] For the periodic experiments, an average yield is calculated over the period to allow comparison with steady-state conditions. Finally, the modified residence time is defined as the catalyst mass divided by the toluene molar flow at the inlet of the reactor [Eq. 3]. 

During the start-up of Superphenix, an experiment related to the Doppler effect has been performed, on the CMP core, decreasing slowly the temperature from 400 to 180°C while maintaining isothermal conditions in the reactor. The increase in reactivity was compensated by control rod insertion. The contributions of the expansion reactivity coefficient (linear with respect to temperature) and of the Doppler effect (logarithmic with respect to temperature) have been separated. The model took into account the effective temperature, using the Debye temperature. The comparison of experiment and calculation, using the reference scheme is given in Table 7. 

In comparison to FBRs, MBRs offer a much more favorable catalyst activity distribution along the reactor [3]. The periodical addition of fresh catalyst in MBRs increases the overall HDM and HDAs performance. Contrary to FBRs, the substantial amount of metals and coke deposits on the catalyst particles is removed through the bottom of the reactor during operation. This feature of MBRs allows for operating at higher pressures (200 MPa) and temperatures (400-430° C) than those in typical FBR units [2]. Thus, MBRs are more tolerant to metals and other contaminants than the FBR, even with the same type of catalyst and under more severe conditions. However, the catalysts used in MBRs should have improved mechanical properties in order to resist severe grinding and abrasion effects during replacement. 

Fig. 11.14 Comparison of N2O evolved obtained during the temperature programmed desorption (TPD) after catalyst was exposed to four different reaction conditions at 180 °C. A temperature ramp of 10 °C/min was applied evolve the N2O from the catalyst. The Fast SCR experiments involved a feed mixture containing 500 ppm NO, 500 ppm NO2, 1,000 ppm NH3, 5 % O2 fed to the reactor for durations of 30 min, 1, and 2 h. The NO2 CR experiments involved a feed mixture of 1,000 ppm NO2, 1,000 ppm NH3, and 5 % O2 for a duration of 2 h...

Figure 6.9.21 Comparison of measured and modeled temperature profiles in a technical fixed bed reactor MIRO refinery, Karlsruhe, Germany) during regeneration (conditions see Tables 6.9.2 and 6.9.3, 20 bar, = 0.9 vol.%, Ue = 0.26m s ...

Figure 7.4 shows the comparison of instantaneous and overall conversion and free monomer during the seeded semibatch emulsion copolymerizations of n-butyl acrylate/ methyl methacrylate (BA/MMA) calculated online from calorimetric measuranents and off-line by gravimetry [29]. These results show that calorimetry predicts overall conversion well but that the prediction of instantaneous conversion and free monomer is less accurate, especially when the polymerization is carried out under starved conditions and/or the monomer concentrations are very low in the reactor, as for the MMA in Figure 7.4d. Under these polymerization conditions, other more accurate techniques (but less robust and more expensive) such as Raman spectroscopy might be better suited for monitoring free monomer concentration [29].

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