Date of Award

2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Douglas P. Harrison

Abstract

Addition of an inexpensive calcium-based CO2 acceptor (dolomite) to a commercial reforming catalyst resulted in the production of 95+% H 2 from CH4 using sorption-enhanced reaction (SER). The combined reforming, shift, and CO2 separation reactions were sufficiently fast that combined reaction equilibrium was closely approached at 15 atm and 650°C. Process simulations showed that in addition to requiring fewer processing steps, SER permits lower reformer temperature, eliminates the need for shift catalysts, and provides a potential energy savings of 20--25% compared to conventional steam-methane reforming (SMR). An off-gas of pure, sequestration-ready CO2 for greenhouse gas emission control is possible using SER. In a commercial process the acceptor must retain activity through many reaction-regeneration cycles. Multicycle durability tests of the CO2 acceptor and reforming catalyst consisting of as many as twenty-five cycles in a fixed-bed reactor and 150 cycles in an electrobalance reactor were performed. These tests examined the effects of sorbent regeneration temperature and gas composition with the sorbent both mixed with and separated from the reforming catalyst prior to regeneration. In a typical twenty-five-cycle test, there was no decrease in maximum H2 concentration, but a gradual decrease in global reaction rate and fractional carbonation of the sorbent were observed. This gradual decrease in performance is explained on the basis of changes in structural properties of the catalyst and acceptor.

ISBN

9780493071381

Pages

234

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