Analysis of the systematic force-transmission error of the magnetic-suspension coupling in single-sinker densimeters and commercial gravimetric sorption analyzers

Reiner Kleinrahm, Xiaoxian Yang, Mark O. McLinden, Markus Richter

Research output: Contribution to journalArticle

Abstract

Here we present an analysis of the force-transmission error for a commercial gravimetric sorption analyzer that applies equally to single-sinker densimeters. Gravimetric sorption analyzers are commonly used for the investigation of gas adsorption on porous materials (e.g., zeolites) with a simultaneous density measurement of the sample gas. The key component of the instrument is a magnetic-suspension coupling; this coupling transmits, without contact, the weight of the “density sinker” and of the sample container with the porous sample (which are both inside a pressurized measuring cell) to a balance at ambient pressure. However, since neither the coupling housing nor the sample gas are magnetically neutral, a small, systematic force-transmission error (FTE) occurs. For the correction of this FTE, an empirical correction model was developed. We show that the FTE can be subdivided into two parts: an apparatus contribution, and a fluid contribution. In the current paper we describe the effect of the FTE on the accuracy of the density measurements; the effect of the FTE on the accuracy of sorption measurements on porous and non-porous materials will be presented in a companion paper. The magnitude of the FTE in case of density measurement is shown by comparing the results of density measurements of four pure gases with values calculated from reference equations of state. The apparatus contribution of the FTE is typically (0.23 kg m−3 + 50 × 10−6·ρfluid), and the fluid contribution can reach values up to 500 × 10−6·ρfluid for diamagnetic fluids; for oxygen-containing gas mixtures it can be much greater.

Original languageEnglish
Pages (from-to)717-735
Number of pages19
JournalAdsorption
Volume25
Issue number4
DOIs
Publication statusPublished - 15 May 2019

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magnetic suspension
densimeters
sorption
Sorption
analyzers
Suspensions
Gases
porous materials
gases
Fluids
fluids
Zeolites
Gas adsorption
Error correction
containers
Equations of state
Gas mixtures
zeolites
Containers
gas mixtures

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@article{94324e11eb964b9eac9744a83a8b481c,
title = "Analysis of the systematic force-transmission error of the magnetic-suspension coupling in single-sinker densimeters and commercial gravimetric sorption analyzers",
abstract = "Here we present an analysis of the force-transmission error for a commercial gravimetric sorption analyzer that applies equally to single-sinker densimeters. Gravimetric sorption analyzers are commonly used for the investigation of gas adsorption on porous materials (e.g., zeolites) with a simultaneous density measurement of the sample gas. The key component of the instrument is a magnetic-suspension coupling; this coupling transmits, without contact, the weight of the “density sinker” and of the sample container with the porous sample (which are both inside a pressurized measuring cell) to a balance at ambient pressure. However, since neither the coupling housing nor the sample gas are magnetically neutral, a small, systematic force-transmission error (FTE) occurs. For the correction of this FTE, an empirical correction model was developed. We show that the FTE can be subdivided into two parts: an apparatus contribution, and a fluid contribution. In the current paper we describe the effect of the FTE on the accuracy of the density measurements; the effect of the FTE on the accuracy of sorption measurements on porous and non-porous materials will be presented in a companion paper. The magnitude of the FTE in case of density measurement is shown by comparing the results of density measurements of four pure gases with values calculated from reference equations of state. The apparatus contribution of the FTE is typically (0.23 kg m−3 + 50 × 10−6·ρfluid), and the fluid contribution can reach values up to 500 × 10−6·ρfluid for diamagnetic fluids; for oxygen-containing gas mixtures it can be much greater.",
keywords = "Force-transmission error, Gravimetric sorption analyzer, Magnetic-suspension coupling, Single-sinker densimeter, Tandem-sinker densimeter",
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Analysis of the systematic force-transmission error of the magnetic-suspension coupling in single-sinker densimeters and commercial gravimetric sorption analyzers. / Kleinrahm, Reiner; Yang, Xiaoxian; McLinden, Mark O.; Richter, Markus.

In: Adsorption, Vol. 25, No. 4, 15.05.2019, p. 717-735.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Analysis of the systematic force-transmission error of the magnetic-suspension coupling in single-sinker densimeters and commercial gravimetric sorption analyzers

AU - Kleinrahm, Reiner

AU - Yang, Xiaoxian

AU - McLinden, Mark O.

AU - Richter, Markus

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N2 - Here we present an analysis of the force-transmission error for a commercial gravimetric sorption analyzer that applies equally to single-sinker densimeters. Gravimetric sorption analyzers are commonly used for the investigation of gas adsorption on porous materials (e.g., zeolites) with a simultaneous density measurement of the sample gas. The key component of the instrument is a magnetic-suspension coupling; this coupling transmits, without contact, the weight of the “density sinker” and of the sample container with the porous sample (which are both inside a pressurized measuring cell) to a balance at ambient pressure. However, since neither the coupling housing nor the sample gas are magnetically neutral, a small, systematic force-transmission error (FTE) occurs. For the correction of this FTE, an empirical correction model was developed. We show that the FTE can be subdivided into two parts: an apparatus contribution, and a fluid contribution. In the current paper we describe the effect of the FTE on the accuracy of the density measurements; the effect of the FTE on the accuracy of sorption measurements on porous and non-porous materials will be presented in a companion paper. The magnitude of the FTE in case of density measurement is shown by comparing the results of density measurements of four pure gases with values calculated from reference equations of state. The apparatus contribution of the FTE is typically (0.23 kg m−3 + 50 × 10−6·ρfluid), and the fluid contribution can reach values up to 500 × 10−6·ρfluid for diamagnetic fluids; for oxygen-containing gas mixtures it can be much greater.

AB - Here we present an analysis of the force-transmission error for a commercial gravimetric sorption analyzer that applies equally to single-sinker densimeters. Gravimetric sorption analyzers are commonly used for the investigation of gas adsorption on porous materials (e.g., zeolites) with a simultaneous density measurement of the sample gas. The key component of the instrument is a magnetic-suspension coupling; this coupling transmits, without contact, the weight of the “density sinker” and of the sample container with the porous sample (which are both inside a pressurized measuring cell) to a balance at ambient pressure. However, since neither the coupling housing nor the sample gas are magnetically neutral, a small, systematic force-transmission error (FTE) occurs. For the correction of this FTE, an empirical correction model was developed. We show that the FTE can be subdivided into two parts: an apparatus contribution, and a fluid contribution. In the current paper we describe the effect of the FTE on the accuracy of the density measurements; the effect of the FTE on the accuracy of sorption measurements on porous and non-porous materials will be presented in a companion paper. The magnitude of the FTE in case of density measurement is shown by comparing the results of density measurements of four pure gases with values calculated from reference equations of state. The apparatus contribution of the FTE is typically (0.23 kg m−3 + 50 × 10−6·ρfluid), and the fluid contribution can reach values up to 500 × 10−6·ρfluid for diamagnetic fluids; for oxygen-containing gas mixtures it can be much greater.

KW - Force-transmission error

KW - Gravimetric sorption analyzer

KW - Magnetic-suspension coupling

KW - Single-sinker densimeter

KW - Tandem-sinker densimeter

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DO - 10.1007/s10450-019-00071-z

M3 - Article

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