Implementation of the Scanning Multichannel Technique in Raman Spectroscopy and the Application for the Characterization of Oxides

Abstract

The scanning multichannel technique (SMT) has proved to be a good method to compensate for the disadvantages of diode arrays as detectors in Raman spectroscopy. A method is presented for implementation of SMT with a system which is equipped with a conventional MT software package. Additional programs were developed for controlling the MT software and for calculation the SMT spectra from the recorded raw data. Additional functions for filtering defective channels of the diode array and for suppressing defective individual spectra were added to improve the quality of the SMT spectra. Sulfate on γ-Al₂O₃ was investigated as a model system for an intermediate of a proposed transfer catalyst for the removal of SO _x from fluid catalytic cracking (FCC) catalysts. The recorded MT spectra were disturbed by the characteristics of the diode array that was used and by a high (fluorescence-like) background of γ-AL₂O₃. As a consequence, the correction of the spectra by the spectrometer function is complicated. In this case, the application of SMT led to Raman spectra with significantly improved quality. The Raman spectra suggest a tridentate structure of the sulfate on the surface of γ-A1₂O₃ having C, or C_{3 v} symmetry.