A Method for the Accurate Quantification of Gas Streams by Online Mass Spectrometry

Abstract

The accuracy of the online quantification of gaseous effluents from catalytic reactors by mass spectrometry (MS) is rarely addressed by researchers despite the extensive use of the technique. MS results are strongly sensitive to both the operation conditions of the reactor and to the state of the instrument. Therefore, most studies use them as qualitative descriptors of the performance of catalytic reaction systems. The purpose of this work was to develop an accurate method for the quantification of gaseous effluents from catalytic reactors. For this purpose, the mathematical expressions from the so-called external and internal standard calibration methods for MS were coupled to the typical metrics used for studying catalytic reactions, namely, conversion, selectivity, and carbon mass balances. The catalytic combustion of methane was selected as a model reaction to test the developed approach. The accuracy of the developed method was validated by comparison with results obtained in a separate reaction system coupled online to a gas chromatograph. The closure of the carbon mass balance was used as control metrics allowing for the assessment of the physical meaning of the method. In general, the internal standard method of calibration was found to be best for the accurate quantification of gaseous streams by online mass spectrometry. In general, the results of this investigation may be of use to researchers in the field of catalysis as well as to research workers using mass spectrometry for various purposes.

Accurate Concentration Measurement Model of Multicomponent Mixed Gases during a Mine Disaster Period

“… 49 , 55 − 57 Velasco-Rozo analyzed the advantages of the internal standard and the external standard for the related experimental setup. 49 To tackle the effect that the concentration and nature of the components of the effluent change over time due to the catalytic reaction, the corresponding mathematical models based on the internal standard and the external standard were established. 48 In addition, Ghasemi established the optimal fitting model for determining the results of multiple mixtures based on multiple linear regression and partial least-squares projections to latent structures, providing a sound theoretical basis.…”

“…Compared with experiments of other studies of mixing gases’ determination, most of them used an internal standard or external standard calibration instrument and correlated the reaction signal with the known gas concentration to accurately quantify the mixed gases via the least-squares method. ,− Velasco-Rozo analyzed the advantages of the internal standard and the external standard for the related experimental setup . To tackle the effect that the concentration and nature of the components of the effluent change over time due to the catalytic reaction, the corresponding mathematical models based on the internal standard and the external standard were established .…”

“…The external standard estimates the sensitivity factors by correlating MS signals to known gas concentrations via least-squares regressions. 49 Ghasemi used the GC/ECD method to study the QSRR of 38 diverse mixing substances; multiple linear regression and partial least-squares methods were used with leave-one-out cross-validation for developing the regression model. Comparing the regression analysis parameters, the two methods fit the results equally well.…”

“…In Alexander’s research, the internal standard led to a highly accurate quantification. The external standard estimates the sensitivity factors by correlating MS signals to known gas concentrations via least-squares regressions . Ghasemi used the GC/ECD method to study the QSRR of 38 diverse mixing substances; multiple linear regression and partial least-squares methods were used with leave-one-out cross-validation for developing the regression model.…”

Quantitative analysis of reaction gases or exhaust using an online process mass spectrometer

“…Most online quantitative analysis methods with mass spectrometers are based on the formulation of the standard gas associated with the reaction gas or exhaust to detect ion abundances and pressures. These calibration parameters are then linearly fitted to establish a mathematical model for the software system to achieve online quantitative analysis of the reaction gas or exhaust [9][10][11][12][13][14][15].…”