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pubblicazioni - Presentazione

Development of Pd-composites membranes for hydrogen production in membrane reactors

pubblicazioni - Presentazione

Development of Pd-composites membranes for hydrogen production in membrane reactors

Palladium based membrane reactors are widely studied for production of high purity hydrogen in several processes, such as natural gas steam reforming, ethanol stem reforming and WGS of synthesis gas.

Due to the considerable cost of palladium, research effort are focused in obtain low thickness Pd membranes, prepared by deposition on cheaper materials, such as macro-porous metals and ceramics, by various techniques, including magneton sputtering, chemical vapor deposition and electroless plating. Electroless plating, in particular, is an autocatalytic process which allows obtaining thin films with good adhesion characteristics; further it does not require expensive set-up and is relatively easy to scale-up from laboratory to industrial scale. As much as the thickness of Pd layer is lowered, however, obtaining defect-free coatings with adequate adhesion and stability is becoming a critical issue in order to produce high purity hydrogen suitable for feeding PEM fuel cells. In this frame RSE is developing palladium composite membrane prepared by electroless plating on stainless steel tubular macroporous supports. The preparation process involves several steps including mechanical treatment of the support, cleaning, oxidation, activation and deposition by solution. Each step should be properly carried out in order to obtain dense and stable membranes. In this paper preparation process and performances of such a membrane are presented. More in detail performances of a 20 micron thick palladium membrane tested for more than 5000 hours in a laboratory pilot loop, in various operating conditions, will be presented. This membrane has been first extensively tested in pure gases and then in a syngas mixture in 300-400°C temperature range and in the 1-14 bar pressure range, in order to define its performances in terms of permeability and perm-selectivity. The long-term stability in H2 flux has also been assessed. The membrane has been then used for WGS tests and for reforming of bioethanol at 390°C in a membrane reactor. Critical issue for process scale-up and prototype development are also identified and further research need are discussed.

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