Raman spectroscopy of impurities in hydrogen relevant to ISO 14687 using a 450 nm laser diode

To prove the high potential of Raman spectroscopy as a tool for gas analysis this study focuses on the standard ISO 14687 – one of the main standards for defining the purity of hydrogen. ISO 14687 lists possible contaminants in hydrogen, which must be monitored for the purpose of quality control. While currently, different methods are employed to monitor all possible contaminants in hydrogen Raman spectroscopy holds the potential to streamline this process. In this study a transportable Raman system has been investigated to record the spectra of all constituents (except Ar and He) listed in ISO 14687. The setup utilizes a 450 nm laser diode, which brings the benefits of robustness and small size while at the same time being capable of recording spectra with high sensitivity due to the low wavelength. The spectra have been recorded at various concentrations to demonstrate the proof of concept. While the main spectra are shown and discussed for low pressure, Raman spectra generated at higher pressure have been used for shifting the detection limits to higher sensitivities. To examine the consequences of elevated pressure the spectrum hydrogen at 35 MPa is presented and discussed.