Quantitative In-situ Monitoring of Parahydrogen Fraction Using Raman Spectroscopy

TY - JOUR

T1 - Quantitative In-situ Monitoring of Parahydrogen Fraction Using Raman Spectroscopy

AU - Parrott, Andrew J.

AU - Dallin, Paul

AU - Andrews, John

AU - Richardson, Peter Michael

AU - Semenova, Olga

AU - Halse, Meghan Eileen

AU - Duckett, Simon

AU - Nordon, Alison

N1 - © The Author(s) 2018. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

PY - 2019/1/1

Y1 - 2019/1/1

N2 - Raman spectroscopy has been used to provide a rapid, noninvasive, and nondestructive quantification method for determining the parahydrogen fraction of hydrogen gas. The basis of the method is the measurement of the ratio of the first two rotational bands of hydrogen at 355 cm −1 and 586 cm −1 corresponding to parahydrogen and orthohydrogen, respectively. The method has been used to determine the parahydrogen content during a production process and a reaction. In the first example, the performance of an in-house liquid nitrogen cooled parahydrogen generator was monitored both at-line and on-line. The Raman measurements showed that it took several hours for the generator to reach steady state and, hence, for maximum parahydrogen production (50%) to be reached. The results obtained using Raman spectroscopy were compared to those obtained by at-line low-field nuclear magnetic resonance (NMR) spectroscopy. While the results were in good agreement, Raman analysis has several advantages over NMR for this application. The Raman method does not require a reference sample, as both spin isomers (ortho and para) of hydrogen can be directly detected, which simplifies the procedure and eliminates some sources of error. In the second example, the method was used to monitor the fast conversion of parahydrogen to orthohydrogen in situ. Here the ability to acquire Raman spectra every 30 s enabled a conversion process with a rate constant of 27:4 * 10 -4 s −1 to be monitored. The Raman method described here represents an improvement on previously reported work, in that it can be easily applied on-line and is approximately 500 times faster. This offers the potential of an industrially compatible method for determining parahydrogen content in applications that require the storage and usage of hydrogen.

AB - Raman spectroscopy has been used to provide a rapid, noninvasive, and nondestructive quantification method for determining the parahydrogen fraction of hydrogen gas. The basis of the method is the measurement of the ratio of the first two rotational bands of hydrogen at 355 cm −1 and 586 cm −1 corresponding to parahydrogen and orthohydrogen, respectively. The method has been used to determine the parahydrogen content during a production process and a reaction. In the first example, the performance of an in-house liquid nitrogen cooled parahydrogen generator was monitored both at-line and on-line. The Raman measurements showed that it took several hours for the generator to reach steady state and, hence, for maximum parahydrogen production (50%) to be reached. The results obtained using Raman spectroscopy were compared to those obtained by at-line low-field nuclear magnetic resonance (NMR) spectroscopy. While the results were in good agreement, Raman analysis has several advantages over NMR for this application. The Raman method does not require a reference sample, as both spin isomers (ortho and para) of hydrogen can be directly detected, which simplifies the procedure and eliminates some sources of error. In the second example, the method was used to monitor the fast conversion of parahydrogen to orthohydrogen in situ. Here the ability to acquire Raman spectra every 30 s enabled a conversion process with a rate constant of 27:4 * 10 -4 s −1 to be monitored. The Raman method described here represents an improvement on previously reported work, in that it can be easily applied on-line and is approximately 500 times faster. This offers the potential of an industrially compatible method for determining parahydrogen content in applications that require the storage and usage of hydrogen.

KW - Raman spectroscopy

KW - gas analysis

KW - hydrogen

KW - in situ monitoring

KW - parahydrogen

KW - quantitative analysis

UR - http://www.scopus.com/inward/record.url?scp=85059345575&partnerID=8YFLogxK

U2 - 10.1177/0003702818798644

DO - 10.1177/0003702818798644

M3 - Article

SN - 0003-7028

VL - 73

SP - 88

EP - 97

JO - APPLIED SPECTROSCOPY

JF - APPLIED SPECTROSCOPY

IS - 1

ER -