Multi-tube Pd–Ag membrane module for pure hydrogen production: Comparison of methane steam and oxidative reforming

Abstract

The results of steam and oxidative reforming of methane carried out through a membrane system are being compared in this work. The capability of the experimental setup to produce ultra-pure hydrogen has been evaluated in terms of hydrogen yield under different operating conditions.The reforming reactions took place over a Pt on Al2O3 catalyst in a traditional high temperature reformer, while the hydrogen produced has been removed by selective permeation in a membrane module containing an array of 19 defect-free Pd–Ag tubes (length 250 mm, diameter 10 mm and wall thickness 0.150 mm).The reformer has been tested in the temperature range of about 570–720 °C while the membrane module temperature has been maintained at 350 °C and the reaction (lumen) pressure has been ranged between 100 and 500 kPa. Methane feed flow rates from about 0.4 × 10−3 to 1.1 × 10−3 mol s−1 have been fed into the reformer with methane/water molar ratios of 1/4 and methane/water/oxygen of 1/3/0.33 for the steam and the auto-thermal reforming, respectively.A maximum hydrogen yield value of 2.8 corresponding to a hydrogen flow rate of 1.20 × 10−3 mol s−1 has been measured during the methane steam reforming at pressure of 350 kPa, GHSV of 864 L(STP) kg−1 h−1 and reformer temperature of 700 °C.