Ceramic Microreactors for on-Site Hydrogen Production
Christian
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https://hdl.handle.net/2142/82391
Description
Title
Ceramic Microreactors for on-Site Hydrogen Production
Author(s)
Christian
Issue Date
2006
Doctoral Committee Chair(s)
Kenis, Paul J.A.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical and Biomolecular Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
The development of microreactors has been growing rapidly in recent years. The advantages of using microreactors over macroscale reactors make them useful for various applications, including catalyst development and optimization, on-site synthesis of hazardous chemicals and reactive intermediates, and the study of dangerous reactions under relatively safe conditions. At the same time, fuel cell technology has started to emerge as an attractive option to obtain electrical power sources for the operation of portable electronic devices, vehicles, and electrical equipment in remote locations. The development of polymer electrolyte membrane (PEM) fuel cells, however, has been hindered by safety issues related to storage and distribution of highly flammable H 2. Microreactors, on the other hand, show promise for efficient catalytic reforming of liquid hydrocarbons at high temperatures for on-board generation of H2 for fuel cell applications, thereby avoiding the need for H2 storage and transport. The present challenges encountered in the reforming of hydrocarbons, such as propane, diesel, or JP-8, are: (i) to avoid coking of the catalyst surface by operating at temperatures above 800°C; (ii) to achieve high conversion in a small reactor volume; and (iii) to have a low, sustainable pressure drop across the reactor. A suitable microreactor, to meet these challenges, must be compatible with high temperatures, have a large surface area-to-volume ratio, and have a high porosity. This study focuses on the synthesis, characterization, and design optimization of ceramic microreactors composed of high surface area, inverted beaded silicon carbide (SiC) or silicon carbonitride (SiCN) porous monoliths integrated within high-density alumina reactor housings. Subsequent characterization of these novel ceramic microreactors for on-site H2 production was performed using the decomposition of ammonia and the steam reforming of propane at temperatures as high as 1000°C. As much as 50 sccm of H2 can be produced per cm3 reactor, equivalent to 9.8x104 sccm H2 per cm3 of monolith or approximately 7 kWe power output per cm3 of monolith from a typical PEM fuel cell operating at 50% efficiency.
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