skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Simple Flow Through Reaction Cells for in situ Transmission and Fluorescence X-ray Absorption Spectroscopy of Heterogeneous Catalysts

Abstract

We report on the design of both transmission and fluorescence x-ray-absorption spectroscopy cells suitable for in situ characterization of heterogeneous catalysts. The heart of both cells is a quartz tube used to house the catalyst sample. Both cells allow in situ x-ray-absorption fine-structure (XAFS) data to be recorded from -196 to 825 deg. C using a wide range of gas flows at atmospheric pressure. Excellent temperature control is demonstrated with both designs. XAFS data can be recorded over a wide x-ray energy range (2.1-29 keV). These designs are simple, robust, relatively low cost, and, moreover, are reliable and easy to operate. All of the critical components of the transmission reactor can be purchased commercially, with little machining required. The design of the fluorescence reactor requires access to a skilled glass blower.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914186
Report Number(s):
BNL-78754-2007-JA
Journal ID: ISSN 0034-6748; RSINAK; TRN: US200804%%324
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Rev. Sci. Instrum.; Journal Volume: 77
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CATALYSTS; SAMPLE HOLDERS; DESIGN; GAS FLOW; X-RAY FLUORESCENCE ANALYSIS; X-RAY SPECTROSCOPY; HETEROGENEOUS CATALYSIS; national synchrotron light source

Citation Formats

Bare,S., Mickelson, G., Modica, F., Ringwelski, A., and Yang, N.. Simple Flow Through Reaction Cells for in situ Transmission and Fluorescence X-ray Absorption Spectroscopy of Heterogeneous Catalysts. United States: N. p., 2006. Web. doi:10.1063/1.2168685.
Bare,S., Mickelson, G., Modica, F., Ringwelski, A., & Yang, N.. Simple Flow Through Reaction Cells for in situ Transmission and Fluorescence X-ray Absorption Spectroscopy of Heterogeneous Catalysts. United States. doi:10.1063/1.2168685.
Bare,S., Mickelson, G., Modica, F., Ringwelski, A., and Yang, N.. Sun . "Simple Flow Through Reaction Cells for in situ Transmission and Fluorescence X-ray Absorption Spectroscopy of Heterogeneous Catalysts". United States. doi:10.1063/1.2168685.
@article{osti_914186,
title = {Simple Flow Through Reaction Cells for in situ Transmission and Fluorescence X-ray Absorption Spectroscopy of Heterogeneous Catalysts},
author = {Bare,S. and Mickelson, G. and Modica, F. and Ringwelski, A. and Yang, N.},
abstractNote = {We report on the design of both transmission and fluorescence x-ray-absorption spectroscopy cells suitable for in situ characterization of heterogeneous catalysts. The heart of both cells is a quartz tube used to house the catalyst sample. Both cells allow in situ x-ray-absorption fine-structure (XAFS) data to be recorded from -196 to 825 deg. C using a wide range of gas flows at atmospheric pressure. Excellent temperature control is demonstrated with both designs. XAFS data can be recorded over a wide x-ray energy range (2.1-29 keV). These designs are simple, robust, relatively low cost, and, moreover, are reliable and easy to operate. All of the critical components of the transmission reactor can be purchased commercially, with little machining required. The design of the fluorescence reactor requires access to a skilled glass blower.},
doi = {10.1063/1.2168685},
journal = {Rev. Sci. Instrum.},
number = ,
volume = 77,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • We report on the design of both transmission and fluorescence x-ray-absorption spectroscopy cells suitable for in situ characterization of heterogeneous catalysts. The heart of both cells is a quartz tube used to house the catalyst sample. Both cells allow in situ x-ray-absorption fine-structure (XAFS) data to be recorded from -196 to 825 deg. C using a wide range of gas flows at atmospheric pressure. Excellent temperature control is demonstrated with both designs. XAFS data can be recorded over a wide x-ray energy range (2.1-29 keV). These designs are simple, robust, relatively low cost, and, moreover, are reliable and easy tomore » operate. All of the critical components of the transmission reactor can be purchased commercially, with little machining required. The design of the fluorescence reactor requires access to a skilled glass blower.« less
  • Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rathermore » than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.« less
  • Desulfation by hydrogen of presulfated Pt (2 wt %)-BaO(20 wt %)/Al{sub 2}O{sub 3} with various sulfur loading (S/Ba = 0.12, 0.31, and 0.62) were investigated by combining H{sub 2} temperature programmed reaction (TPRX), X-ray photoelectron spectroscopy (XPS), in situ sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved X-ray diffraction (TR-XRD) techniques. We find that the amount of H{sub 2}S desorbed during the desulfation in the H{sub 2} TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates weremore » transformed to a BaS phase and remained in the catalyst rather than being removed as H{sub 2}S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H{sub 2}S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H{sub 2}O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H{sub 2}S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt-BaO/Al{sub 2}O{sub 3} lean NO{sub x} trap catalysts is markedly dependent on the sulfation levels.« less
  • We present a novel in situ reaction cell for heterogeneous catalysis monitored in situ by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). The reaction can be carried out at a total pressure up to 1 atm, a regime that has not been accessible to comparable in situ techniques and thus closes the pressure gap to many industrial standard conditions. Two alternate catalyst geometries were tested: (A) a thin film evaporated directly onto an x-ray transparent membrane with a flowing reaction gas mixture behind it or (B) a powder placed behind both the membrane and a gap ofmore » flowing reaction gas mixture. To illustrate the working principle and feasibility of our reaction cell setup we have chosen ethylene epoxidation over a silver catalyst as a test case. The evolution of incorporated oxygen species was monitored by total electron/fluorescence yield O K-XAS as well as O K-RIXS, which is a powerful method to separate contributions from inequivalent sites. We find that our method can reliably detect transient species that exist during catalytic reaction conditions that are hardly accessible using other spectroscopic methods.« less