Methane Steam Reforming in a Pd Membrane Reactor

Methane Steam Reforming in a PdPt Membrane Reactor

Stephen N. Paglieri¹, Hani Abu El Hawa²,  Aadesh X. Harale³,  J. Douglas Way²

¹TDA Research, Inc., Wheat Ridge, CO 80033-1916, USA

²Department of Chemical & Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA

³Saudi Arabian Oil Company, Dhahran, 31311, KSA

Competitively priced, widely available hydrogen is crucial for the transition to a hydrogen economy. The distributed production of hydrogen from abundant, domestic natural gas resources by methane steam reforming (MSR) currently requires very high temperature catalytic reactors coupled with bulky purification equipment. Demonstrable gains in efficiency for MSR in a membrane reactor can be obtained by the withdrawal of product hydrogen, which enables operation at much lower temperatures instead of the 750-900 °C that is required in conventional MSR reactors.

Thin film Pd and PdPt membranes (~5 µm thick)[1] supported on porous yttria-stabilized-zirconia/stainless steel substrates (ZrOD AccuSep, Pall Corp.) were used to carry out MSR over a commercial Ni-based reforming catalyst at temperatures up to 600 °C and pressures up to 2.9 MPa. Methane conversion was significantly higher than the thermodynamic equilibrium predicted for the feed composition; >90% conversion was  obtained at 600 °C, a steam-to-carbon ratio (H₂O/CH₄) of 5 and a gas-hourly space velocity (GHSV) of 360 h^-1 when the permeate hydrogen was evacuated, as shown in Fig. 1. For comparison, the equilibrium conversions at these conditions are <20% . The effect of parameters such as space velocity, steam-to-carbon ratio, membrane hydrogen permeance, temperature and pressure on methane conversion and hydrogen recovery will be discussed.

Reference

1.         Lewis, A.E., et al., Pd–Pt/YSZ composite membranes for hydrogen separation from synthetic water–gas shift streams. J. Membr. Sci., 2013. 437: p. 257-264.

 

Figure 1. Methane conversion vs. pressure at 600 °C, H2O/CH4 = 5 and GHSV = 360 h-1 in the conventional reactor (CR) and the palladium membrane reactor (PMR). The permeate H2 was evacuated in some runs (PMR vacuum). Thermodynamic equilibrium conversions are shown for comparison.