Low-cost, heated, and/or cooled flow-through cell for transmission x-ray absorption spectroscopy

Abstract

A transmission x-ray absorption spectroscopy cell that can be used for air-sensitive samples with in situ treatment is described. The cell is designed with a relatively small size for use with air-sensitive powdered catalyst samples that must be loaded in a glove box. Samples can be treated in situ with gas flow or vacuum and temperature control up to 500 °C. The cell is constructed of stainless steel and designed for durability as well as ease of repair. The cells are vacuum tight and equipped with beryllium windows sealed with vacuum O-ring flanges for easy loading. Each cell, with all parts excluding the windows, costs about $2700.

X-ray Absorption Fine Structure Analysis of the Local Environment of Fe in Fe/Al−MFI

“…Prior to X-ray absorption measurements, the sample was pressed into a rectangular slot of a sample holder. The sample holder was then mounted in a cell, similar to that described by Jentoft et al 27 Beryllium windows mounted at both ends of the cell permitted passage of the X-ray beam through the cell, while allowing the cell to be filled with gas or evacuated. After purging the cell in He, the samples were pretreated by heating in He at 773 K for 2 h 20 min and cooled to room temperature.…”

Transmission and fluorescence X-ray absorption spectroscopy cell/flow reactor for powder samples under vacuum or in reactive atmospheres

“…8 Modern flow XAS cells address the issues of fluid flow and accommodate powder samples, and in some instances the flow distribution is approximated as plug flow, which is advantageous for quantifying catalyst performance based on analysis of reaction products. 9,10 Typically, the meshed sample is pressed into the cell and held in the fluid flow path with glass/quartz wool.…”

“…Characterization of stable states of catalysts is often carried out with cells designed for low-temperature (e.g., liquid nitrogen temperature) static 8 or dynamic (cryostat) vacuum operation. The sample is typically pressed into a pellet or wafer.…”

Imine Metathesis Catalyzed by a Silica-Supported Hafnium Imido Complex

“…16,17 A comparison of these distances indicates that hafnium is strongly bonded to the support. The result that this distance is less that the Hf-O distance characterizing HfO 2 is not surprising; there are examples of hafnium complexes with Hf-O distances determined by EXAFS spectroscopy that are similar to the value determined in our work and markedly less that the value characterizing bulk HfO 2 .…”

“…16 Various plausible models of the supported species were investigated in the data fitting, which is summarized in the SI. The number of statistically justified EXAFS fitting parameters was calculated on the basis of the Nyquist criterion to be 16, corresponding to at most four shells.…”