Intensity Simulation of a Fourier Transform Infrared Spectrometer

This paper introduces an intensity simulation for the Fourier transform infrared spectrometer whose core element is the Michelson interferometer to provide support for the on-orbit monitoring of the instrument and to improve the data processing and application of the Fourier transform spectrometer. The Geostationary Interferometric Infrared Imager (GIIRS) aboard on Fengyun-4B (FY-4B) satellite, which will be launched in 2020, aims to provide hyperspectral infrared observations. An intensity simulation of the Michelson interferometer based on the GIIRS’s instrument parameters is systematically analyzed in this paper. Off-axis effects and non-linearity response are two important factors to be considered in this simulation. Off-axis effects mainly cause the wavenumber shift to induce a large brightness temperature error compared with the input spectrum, and the non-linearity response reduces the energy received by the detector. Then, off-axis effects and a non-linearity response are added to the input spectrum successively to obtain the final spectrum. Off-axis correction and non-linearity correction are also developed to give a full simulation process. Comparing the corrected spectrum with the input spectrum, we can see that the brightness temperature errors have a magnitude of 10−3 K, and this fully proves the reliability and rationality of the whole simulation process.

Transformation of Propane over ZnSnPt Modified Defective HZSM-5 Zeolites: The Crucial Role of Hydroxyl Nests Concentration

A series of ZnSnPt supported defective MFI zeolites with different SiO2/Al2O3 ratios (30, 110, 700, and ∞) and hydroxyl nests concentration were prepared and characterized by multiple techniques including scanning electron microscopy (SEM), nitrogen physisorption, NH3-TPD, transmission electron microscopy (TEM), hydrogen temperature programmed reduction (H2-TPR), and Fourier transform infrared spectrometer (FT-IR). It was found that Brønsted acid sites (Si(OH)Al) with strong acid strength and the hydroxyl nests with weak acid strength coexisted over the defective ZSM-5 zeolites and ZnSnPt Lewis acid sites preferentially located on the hydroxyl nests. The increase in the concentration of hydroxyl nests and SiO2/Al2O3 ratios apparently improved the distribution of ZnSnPt Lewis acid sites. The hydroxyl nest incorporated ZnSnPt Lewis acid sites showed extraordinary dehydrogenation ability. Specially, operando dual beam Fourier transform infrared spectrometer (DB-FTIR) was applied to characterize the propane transformation under reaction conditions. At low SiO2/Al2O3 ratios, the propane efficiently transforms into propene and aromatics (total selectivity of 93.37%) by the cooperation of Brønsted acid sites and ZnSnPt Lewis acid sites. While at high SiO2/Al2O3 ratios, the propane mainly transforms into propene (selectivity of above 95%) and hydrogen. This study provides guidance for the preparation of highly efficient propane dehydrogenative transformation catalyst.