Grantee Research Project Results
Final Report: Knudsen Cell Reactor for Catalyst Research Related to Hydrogen Technologies
EPA Grant Number: SU832475Title: Knudsen Cell Reactor for Catalyst Research Related to Hydrogen Technologies
Investigators: Glawe, Diana , Chandler, Bert , Pursell, Chris
Institution: Trinity University
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 30, 2005 through May 30, 2006
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2005) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Chemical Safety , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
Hydrogen has been identified as a viable sustainable alternative to fossil fuels. Hydrogen–powered technologies are predicted to have minimal direct impact on the planet and its inhabitants as compared to the devastating impact of pollution caused by burning fossil fuels. As an energy source, hydrogen is ecologically feasible, socially desirable, and with continued research and development promises to become economically viable. However, the economic viability of hydrogen energy systems will require substantial advances in tuning catalyst selectivity, developing poison resistant catalysts, and reducing the reliance on expensive Platinum Group Metals (PGMs). Bimetallic nanoparticle-based catalysts have been theoretically predicted to meet these three criteria.
The faculty advisors listed in this proposal have formed an interdisciplinary research team to develop and characterize new bimetallic nanoparticle catalysts for use in evolving hydrogen technologies. The P3 Phase I Award was both ideally suited and timely to enable a student design group to contribute to this interdisciplinary research effort. The tangible product of the students’ contribution in Phase I was an overall design for a full-scale multi-sample Knudsen cell reactor along with the fabrication and testing of the first technologic challenge of the design, a multiple sample holder and its associated components. The construction and application of a Knudsen cell reactor will allow careful measurement of the temperature dependence of gas uptake coefficients, activity coefficients, surface coverages, and reaction rate constants, all of which are necessary to validate theoretical predictions and develop the new bimetallic nanoparticle catalysts proposed for use in hydrogen technologies.
A P3 Phase II Award will enable implementation of the Knudsen cell reactor by a new group of select undergraduate students under the guidance of the three faculty advisors involved in Phase I. The new students will extend the overall Knudsen cell reactor design from Phase I to include the auxiliary equipment and gas handling system necessary to operate the reactor. During this process, the students must evaluate alternatives and select combinations that best meet the design criteria and realistic design constraints such as operator safety and system sustainability. Spatial limitations will be a challenge in determining the optimal configuration in which to attach the auxiliary equipment to the test chamber. The students’ analysis and decisions will be evaluated on a continuous basis by the faculty advisors through informal weekly meetings and formal reporting.
Once the Knudsen cell reactor is fabricated and the auxiliary equipment is acquired, the students in Phase II will assemble, test, and calibrate all subsystems of the reactor. Students will develop test procedures to ensure the integrity of the following operations: controlled heating and cooling of the sample, isolation of the sample from the surrounding chamber environment, gas exchange, accurate temperature and pressure measurements, and accurate spectral measurement. Once the integrity of the system is guaranteed, the students will initiate testing of nanoparticle catalysts in the reactor.
Successful completion of the Knudsen cell reactor will provide the foundation for the experiments necessary to characterize and develop new catalysts to support a sustainable hydrogen economy that will ultimately benefit the planet and its inhabitants.
Summary/Accomplishments (Outputs/Outcomes):
The two primary design challenges for the student group in Phase I were the overall system configuration and thermal isolation of the test sample heating and cooling mechanism. The group developed and analyzed numerous options for the overall system configuration, which resulted in the requirement for three separate chambers. The first chamber contains the test specimen under ultra high vacuum (13.3 μPa) conditions. The second chamber contains the liquid nitrogen Dewar and cooling device under vacuum (13.3 mPa) conditions. The third chamber encases the two vacuum chambers and the optical system used to direct the laser beam from a Fourier Transform Infrared (FTIR) spectrometer through samples inside high-vacuum chamber. This outermost chamber is nitrogen or dry-air purged to eliminate ambient water vapor from the optical path of the FTIR beam. The optical system was constructed on a rail system to move two mirrors, one on each side of the test sample, in unison along the length of the test chamber to address each of the four samples in sequence.
The requirement for the sample to reach temperatures spanning from cryogenic (-200° C) to extremely high (300° C) without heating or cooling the chamber walls required innovation. The extension of the cooling mechanism from the liquid nitrogen vacuum chamber into the high vacuum sample chamber required a pressure seal design that withstands both temperature extremes and insulates the chamber walls from the cooling, and attached heating, mechanism. A successful design was achieved using a combination of spring loaded Teflon-like seals along with ceramic spacers for structural support. The two vacuum chambers and the integrated pressure seal design will require custom manufacturing, which is planned for Phase II.
The completed optical system as well as prototypes of a sample holder and associated components (i.e. retractable cup, motion actuator, and cup seal) has been tested. Based on prototype testing, suggested improvements for the final design include: smaller sample holders to minimize interference with mass spectroscopy measurements, pneumatic rather than manual retracting mechanisms, and additional optical components to facilitate optical alignment. These changes are planned for fabrication of the final reactor in Phase II.
Conclusions:
The student team’s multi-sample Knudsen cell reactor design resulting from Phase I promises to be a valuable tool to characterize the kinetic properties of bimetallic nanoparticle catalyst. From a design standpoint, most of the major required systems have been conceptualized. Prototype components were fabricated and tested. Recommended improvements will be incorporated into the final design allow for the rapid and reliable testing of multiple samples. P3 Phase II Funding will allow for the complete fabrication, testing, and implementation of the Knudsen cell reactor. This will subsequently provide new catalyst research and development opportunities for facultyguided student research teams.
Supplemental Keywords:
Energy, pollution, nanotechnology, renewable, clean technologies, measurement methods, transportation, hydrogen initiative, hydrogen technologies, RFA, Scientific Discipline, Sustainable Industry/Business, POLLUTION PREVENTION, Environmental Chemistry, Sustainable Environment, Energy, Technology for Sustainable Environment, Environmental Engineering, Knudsen cell reactor, hydrogen fuels, hydrogen technologies, catalysts, energy efficiency, energy technology, alternative energy sourceThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.