An innovative configuration of a Pd-based membrane reactor for the production of pure hydrogen: Experimental analysis of water gas shift

Abstract

Pure hydrogen production is of fundamental interest for its use as feed of proton exchange membrane fuel cells. In this work an innovative configuration for a membrane reactor (MR) was proposed: the membrane is located only in the second part of the catalytic bed. This configuration is of particular importance in all the reactions characterized by low kinetics such as, e.g., water gas shift (WGS). Permeation of hydrogen, in the desired direction, takes place when its partial pressure on the reaction side exceeds that on the permeate side. In an MR where the membrane starts at the reactor entrance there is a part of membrane area giving back permeation to the reaction side. The length used in a bad way depends on the kinetics: for fast kinetics reactions (e.g., methane steam reforming) it is very short but is significantly higher for reactions characterized by low kinetics (e.g., WGS). The innovative configuration proposed allows a good exploitation of the whole membrane area for the permeation. This innovative Pd-alloy (60 μm thick) MR was used to analyse the WGS reaction at 280–320 °C, up to 600 kPa, GHSV ranging from 2000 h −1 to 4500 h −1. A significant reduction of the reaction volume required to achieve the same CO conversion was shown by the novel configuration of the MR with respect to the “typical” one used up to now.