Model‐based Analysis of Fixed‐bed and Membrane Reactors of Various Scale

Abstract

A packed‐bed membrane reactor in a distributor configuration is studied theoretically for the oxidative propane dehydrogenation and compared with a fixed‐bed reactor. Based on detailed 2D models considering two different heat and mass transport models the reactor scale‐up including various reactor‐to‐particle diameter ratios (D/dP) is analyzed with respect to reactor performance, heat transfer and hot spot formation. Higher selectivities at lower hot spot temperatures occur in the packed‐bed membrane reactor for the same reaction conditions.

Process Intensification of the Propane Dehydrogenation Considering Coke Formation, Catalyst Deactivation and Regeneration—Transient Modelling and Analysis of a Heat-Integrated Membrane Reactor

“…) and the inlet concentration of propane (x C 3 H 8 ,in ) are constant for all simulations performed [22]. The reactor operating conditions are summarized in Table 1.…”

“…Furthermore, the interaction between the oxygen concentration and the local hot spot formation is analyzed to evaluate the potential of a forced TDH in the tube-side by heat integration in the PBMRint at various oxygen inlet concentrations. To achieve comparability with previous results for the FBR and the PBMR, the wall temperature (T W ), the inlet temperature (T in ), the weight hourly space velocity (WHSV = m cat,ss V ) and the inlet concentration of propane (x C 3 H 8 ,in ) are constant for all simulations performed [22]. The reactor operating conditions are summarized in Table 1.…”

“…Therefore, Comsol ® Multiphysics 5.6 is applied to calculate axial, radial and temporal complex concentration, temperature and velocity fields, which result due to distributed reactant dosing [22]. To model the difficult heat and mass transfer, taking radial convection and dispersion of the dosed oxygen into account, previous studies figured out that the λ(r) heat and mass transfer model [27] fits experimental data of the ODH in a good agreement, since a radial porosity distribution and the laminar boundary layer are considered [22]. To assure comparability between previous results of the FBR and the PBMR, the λ(r) model is also applied for the PBMRint.…”

“…In this contribution, the focus lays on the exothermic (ΔH R 0 = -118 kJ/mol) oxidative propane dehydrogenation with oxygen (ODH), since present oxygen depresses coking. One of the major efforts in the research field of the ODH is to find capable reactor concepts to reach high propene selectivity at high propane conversion [19][20][21], since undesired series oxidations of propene occur, as can be seen in the derived reaction network, presented in Figure 1a [17,22]. The model catalyst used in the performed experiments is VO x /Al 2 O 3 with 1.4% V [23][24][25].…”

“…The model catalyst used in the performed experiments is VO x /Al 2 O 3 with 1.4% V [23][24][25]. In comparison with a conventional fixed-bed reactor (FBR, Figure 1b) a packed-bed membrane reactor (PBMR, Figure 1b) in distributor configuration offers potential by coupling compound dosing (e.g., oxygen) and chemical reaction, since the propene yield can be increased up to 7% due to higher propene selectivity caused by locally lowered oxygen concentrations [22,23]. To combine the advantages of TDH (high selectivity) and ODH (exothermic, high conversion, depressing coke formation), a heat-integrated membrane reactor concept with an internal flow reversal (PBMRint, Figure 1c) is developed, applying process intensification in a new highly integrated multifunctional reactor.…”