Modeling and performance assessment of Pd- and Pd/Au-based catalytic membrane reactors for hydrogen production

Abstract

A mathematical steady-state modeling framework for the isothermal operation of a membrane reactor for methane steam reforming is developed, and a comparative performance assessment of the catalytic membrane reactor (CMR) versus a conventional packed bed reactor (PBR) is accordingly conducted. A detailed literature benchmarking suggests that the models developed in the present study predict total methane conversion levels within 99% of the experimental values reported in the literature. The proposed Pd-and Pd/Au-based CMR model is utilized for the aforementioned performance analysis under a broad range of reactor operating conditions such as temperature (350-750 C), pressure (2-30 bars), steam to methane ratio (1-15), membrane thickness (1-50 mm), and permeate-side sweep ratio (1-100). In all simulation runs conducted, the superior performance of both the Pd-and Pd/Aubased CMR over the PBR was amply demonstrated. Furthermore, within the proposed CMR modeling framework, an index-based analysis is conducted that concretely quantifies progress towards the attainment of key process intensification objectives. In particular, by appropriately defining the D-index, which explicitly captures potential performance and process intensification benefits associated with attainable total CH 4 conversion levels under different reactor operating conditions, it is shown that the optimum CMR performance is achieved at high pressure and low temperature operating conditions, which was particularly suitable for the attainment of key process intensification objectives as well as optimum performance target levels.

Experimental and simulation studies of the production of renewable hydrogen through ethanol steam reforming in a large-scale catalytic membrane reactor

“…Furthermore, there is an overall increase in the gold content of the membrane, which can significantly influence the solubility of H 2 in the active sites of the membrane, as reported by Sonwane et al [41]. Nonetheless, the H 2 permeance of the membrane is in agreement with the values presented in the literature for Pd and Pd/Au membranes [9,10,42] and with 20 lm free standing foils, which have a theoretical permeance of 15 and 23 Nm 3 m À2 h À1 bar À0.5 at 350°C and 450°C, respectively. Notice that the resistance of the support is not taken into consideration for the theoretical calculation of the free standing foils, suggesting that the selective layer of the membrane presented in this work has enhanced properties and/or the resistance of the support is negligible.…”

“…In CMRs, the process of MSR is expected to proceed further when operating at reduced feed flow rates, assuming that the reaction is not kinetically limited but rather controlled by the permeation rate of the membrane. This phenomenon has been previously reported in the literature [42,47], where methane conversion reduces as the space velocity is increased. In Fig.…”

“…The same effect appears to occur for CO 2 , where as the pressure increases, the CO 2 mole fraction of the retentate increases (Notice that the accuracy of the 1-D and 2-D models with respect to CO 2 is of 79% and 95% respectively). In conventional reactors, ESR [2] and MSR [42] show a negative response to pressure as it is thermodynamically unfavorable, as described by Le Chatelier's principle. Nonetheless, the removal of H 2 from the reaction zone changes the composition of the reaction zone, improving the overall performance of the reactions.…”

Mathematical Modeling of an Integrated Membrane Reactor for Methane Steam Reforming

“…Isothermal operation is generally assumed, but there are few other works that use also energy balances, simulating the non-isothermal operation [7,53]. However, the existing models are one dimensional, so they are not capable to describe the heat and mass transfer processes inside the reactor [50,54,55,56,57,58,59]. In addition, this kind of model, are not able to study the influence of the structural and textural properties of membrane on the system [60].…”

Sweep gas flow effect on membrane reactor performance for hydrogen production from high-temperature water-gas shift reaction

“…The pseudo-homogeneous mathematical model is used to formulate the steady-state operation of the MR[43,44], À2πR R J H 2 ; for i ¼ H 2 ðA2Þ R q R À h m ðT R À T P Þ;i ¼ CO; H 2 O; H 2 ; CO 2ðA4Þ…”