Integration of a Modified Synchrotron Radiation Photoionization Time-of-Flight Mass Spectrometer with a Residual Gas Analyzer for Complementary Detection of Catalytic Products with Different Ionization Energies

In situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) is a powerful tool for detecting gas-phase species including intermediates and products in gas–solid catalytic reactions. However, achieving sensitive and more comprehensive monitoring of gas-phase compounds with different ionization energies in a single measurement remains a significant challenge. In this work, a multiphysics ion trajectory simulation integrating a coupled computational fluid dynamics-direct simulation Monte Carlo (CFD-DSMC) method for continuum-rarefied flow was carried out for tracing the ion motion within the ionization region. The simulation results were applied to the design of the cage lens assembly of a modified SR-PIMS, and a limit of detection (LOD) of 0.67 ppbv ( S / N ≥ 3) was achieved under Kr-lamp calibration conditions for toluene. Furthermore, a residual gas analyzer (RGA) was coupled to the SR-PIMS for the complementary detection of organic products with low ionization energies (IEs, generally lower than 11 eV) and H 2, CO, CO 2 etc. with higher IEs, thereby reducing the need for separate measurements at multiple photon energies. The optimized SR-PIMS setup combined with RGA was successfully applied to probe the intermediates and products generated during the methanol-to-hydrocarbons (MTH) reaction over ZnO/HZSM-5 catalysts, and the time-evolved profiles for major species under different ZnO loadings were obtained and analyzed.