Effects of instrumental configuration, sample preparation, and pretreatment on the IR spectra of silicalite-1

Abstract

Abstract Infrared spectroscopy (IR) is an important tool to investigate the structure of silicalite-1, but the reported spectra vary considerably depending on the instrumental configuration, sample preparation methods, and pretreatment conditions. This inconsistence makes the investigation of the structure-property correlations difficult. Herein, we investigate the effects of different optical modes (attenuated total reflectance, transmission, diffuse reflectance), different detectors (Mercury Cadmium Telluride and Deuterated Triglycine Sulfate, MCT and DTGS), different sample preparation methods (powder, silicalite-1/KBr wafer, pure silicalite-1 wafer), and different pretreatment temperatures (RT–400°C) on the spectral shapes of the skeletal and hydroxyl region IR spectra of silicalite-1. Then the appropriate measurement conditions to obtain reproducible and intrinsic spectra were determined. For the skeletal region IR spectra of silicalite-1, the suitable conditions are the transmission mode with a DTGS detector and 1:500 silicalite-1/KBr wafers. For the hydroxyl region IR spectra, an in-situ transmission cell with pure sample wafers and pretreatment at 400°C are appropriate. Under these suitable measurement conditions, spectral changes can reflect the changes in the silicalite-1 structure to facilitate the elucidation of the structure-property correlations of silicalite-1 by IR spectroscopy.