Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-040813-171517


Document Typedissertation
Author NameAugustine, Alexander Sullivan
URNetd-040813-171517
TitleSupported Pd and Pd/Alloy Membranes for Water-Gas Shift Catalytic Membrane Reactors
DegreePhD
DepartmentChemical Engineering
Advisors
  • Yi Hua Ma, Advisor
  • Nikolaos K. Kazantzis, Co-Advisor
  • Robert W. Thompson, Committee Member
  • Richard D. Sisson, Committee Member
  • Keywords
  • Pd membranes
  • hydrogen production
  • water-gas shift
  • catalytic membrane reactor
  • Date of Presentation/Defense2013-04-08
    Availability unrestricted

    Abstract

    This work describes the application of porous metal supported Pd-membranes to the water-gas shift catalytic membrane reactor in the context of its potential application to the Integrated Gasification Combined Cycle (IGCC) process. The objective of this work was to develop a better understanding of Pd-membrane fabrication techniques, water-gas shift catalytic membrane reactor operation, and long-term behavior of the Pd-membranes under water-gas shift conditions.

    Thin (1.5 16 um) Pd-membranes were prepared by electroless deposition techniques on porous metal supports by previously developed methods. Pd-membranes were installed into stainless steel modules and utilized for mixed gas separation (H2/inert, H2/H2O, dry syngas, and wet syngas) at 350 450C and 14.5 atma to investigate boundary layer mass transfer resistance and surface inhibition. Pd-membranes were also installed into stainless steel modules with iron-chrome oxide catalyst and tested under water-gas shift conditions to investigate membrane reactor operation in the high pressure (5.0 - 14.6 atma) and high temperature (300 500C) regime. After the establishment of appropriate operating conditions, long-term testing was conducted to determine the membrane stability through He leak growth analysis and characterization by SEM and XRD. Pd and Pd/Au-alloy membranes were also investigated for their tolerance to 1 20 ppmv of H2S in syngas over extended periods at 400C and 14.0 atma.

    Water-gas shift catalytic membrane reactor operating parameters were investigated with a focus on high pressure conditions such that high H2 recovery was possible without a sweep gas. With regard to the feed composition, it was desirable to operate at a low H2O/CO ratio for higher H2 recovery, but restrained by the potential for coke formation on the membrane surface, which occurred at a H2O/CO ratio lower than 2.6 at 400C. The application of the Pd-membranes resulted in high CO conversion and H2 recovery for the high temperature (400 500C) water-gas shift reaction which then enabled high throughput. Operating at high temperature also resulted in higher membrane permeance and less Pd-surface inhibition by CO and H2O.

    The water-gas shift catalytic membrane reactor was capable of stable CO conversion and H2 recovery (96% and 88% respectively) at 400C over 900 hours of reaction testing, and 2,500 hours of overall testing of the Pd-membrane. When 2 ppmv H2S was introduced into the membrane reactor, a stable CO conversion of 96% and H2 recovery of 78% were observed over 230 hours. Furthermore, a Pd90Au10-membrane was effective for mixed gas separation with up to 20 ppmv H2S present, achieving a stable H2 flux of 7.8 m3/m2-h with a moderate H2 recovery of 44%. The long-term stability under high pressure reaction conditions represents a breakthrough in Pd-membrane utilization.

    Files
  • Alex_A_Thesis.pdf

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