Synthesis and characterization of thermally stable palladium-based composite membranes for high temperature applications

In this thesis, the inert gas leak evolution problem in electroless-plated palladium-based composite membranes has been revisited. Palladium was doped with a higher melting point element such as ruthenium or platinum and the rate of increase of the nitrogen leak in the temperature range of 500-600 ºC was determined. The results showed that doping Pd with Pt or Ru significantly reduces the leak growth rate compared to a pure Pd membrane by almost one order of magnitude. The addition of Ru to Pd was sufficient to lower the leak growth rate, though the hydrogen permeance stability was not improved. The Pd-Pt alloy membrane, despite having a lower hydrogen permeance, had a stable hydrogen flux at higher temperatures. The influence of high temperature annealing (> 640 ºC) on the thermal stability of pure Pd composite membranes was also investigated in order to correlate between thermal stability and microstructural evolution. Pure Pd composite membranes were subjected to different high temperature annealing processes. It was found that employing such heat treatments improved the thermal stability of the membranes when operated at lower temperatures; evidenced by a suppression of the rate at which hydrogen selectivity towards nitrogen declined over time. SEM images of the microstructural evolution as a function of temperature revealed that porosity, which is typically present in as-deposited electroless plated films, is significantly reduced after heat treatment. Thermal stability was also evaluated in actual steam methane reforming (SMR) environments. Thin film (~5.0 µm thick) Pd-Ru and Pd-Au composite membranes were fabricated and used to carry out SMR over commercial Ni or Ru based catalysts at temperatures > 480 °C and pressures up to 2.9 MPa. The conversions obtained (≥ 80%) were significantly higher than the thermodynamic equilibrium predicted (< 35%) for the feed composition at these process conditions. The long term operation (> 500 hours) revealed the potential suitability of these Pd-alloys to be candidates for use in SMR membrane reactors at temperature as high as 600 °C. The permeate hydrogen flux and methane conversion were stable and the hydrogen permeate purity ranged from 93 to 99.7% depending on the operating conditions.

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemical and Biological Engineering

Grantor dc:publisher

Colorado School of Mines. Arthur Lakes Library

Year dc:date.issued

2015

Author dc:creator

• Abu El Hawa, Hani W.

Advisor dc:contributor.advisor

• Way, J. Douglas

Committee members dc:contributor.committeemember

• Tong, Jianhua
• Carreon, Moises A.
• Paglieri, Stephen N.

• electroless plating
• hydrogen separation
• steam methane reforming
• hydrogen production
• catalytic membrane reactor
• palladium-based composite membranes

Statement dc:rights

• Copyright of the original work is retained by the author.

Language dc:language.iso

eng, English

Identifier

T 7856

OAI identifier oai:identifier

oai:repository.mines.edu:11124/20155