title: Hydrogen adsorption on two catalysts for the ortho- to parahydrogen conversion: Cr-doped silica and ferric oxide gel.
abstract: Molecular hydrogen exists in two spin-rotation coupled states: parahydrogen and orthohydrogen. Due to the variation of energy with rotational level, the occupation of ortho- and parahydrogen states is temperature dependent, with parahydrogen being the dominant species at low temperatures. The equilibrium at 20 K (99.8% parahydrogen) can be reached by natural conversion only after a lengthy process. With the use of a suitable catalyst, this process can be shortened significantly. Two types of commercial catalysts currently being used for ortho- to parahydrogen conversion are: iron(iii) oxide (Fe2O3, IONEX®), and chromium(ii) oxide doped silica catalyst (CrO·SiO2, OXISORB®). We investigate the interaction of ortho- and parahydrogen with the surfaces of these ortho-para conversion catalysts using neutron vibrational spectroscopy. The catalytic surfaces have been characterized using X-ray absorption fine structure (XAFS) and X-ray/neutron pair distribution function measurements.
authors.affiliation: European Spallation Source ESS, Tunavägen 24, 22363 Lund, Sweden. monika.hartl@esss.se.
authors.forename: Monika
authors.initials: M
authors.lastname: Hartl
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Robert Chad
authors.initials: RC
authors.lastname: Gillis
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Luke
authors.initials: L
authors.lastname: Daemen
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Olds
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Page
authors.affiliation: MAX IV Laboratory, Lund University, P. O. Box 118, 221 00 Lund, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Carlson
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hügle
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Erik B
authors.initials: EB
authors.lastname: Iverson
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Ramirez-Cuesta
authors.affiliation: European Spallation Source ESS, Tunavägen 24, 22363 Lund, Sweden. monika.hartl@esss.se.
authors.forename: Yongjoong
authors.initials: Y
authors.lastname: Lee
authors.affiliation: European Spallation Source ESS, Tunavägen 24, 22363 Lund, Sweden. monika.hartl@esss.se.
authors.forename: Günter
authors.initials: G
authors.lastname: Muhrer