Catalysis research

What can Timegated® Raman spectrometer do that a conventional Raman system cannot?

Quite often the fluorescence emission is the big problem that prevents the detection of Raman signal. With many inorganic materials the use of longer excitation wavelengths does not help, because that causes the intensity of Raman scattering to decreases significantly. In these cases, Timegated® Raman can offer a solution. With pulsed excitation and gated detection, the TimeGated® system can efficiently reject the fluorescence without losing the intensity of Raman scattering.

Many reactions and processes are carried out at high temperatures. In these cases, the thermal background can prevent the use of Raman for Operations research. With Timegated® Raman, you are able to follow your reactions even well above 1500°C degrees.

Fluorescence lifetime is an average time for a molecule to remain in the excited state before emitting a photon. Time-resolved fluorescence provides more information about the molecular environment of the fluorophore than steady- state fluorescence measurements. Therefore it is commonly used for elucidating the changes in the viscosity, pH, polarity and solvation; to study the molecular interactions, inter‐ and intramolecular distances as well as the kinetic and dynamic rates. Together with molecular structure specific Raman spectra, the time-resolved fluorescence data gives complementary information to catalysis research.

The chemical nature of catalysts is as diverse as catalysis itself. Raman spectroscopy has been utilized to study the bulk and surface chemistry of catalysts occurring during catalyst preparation and under their operation – including the characterization of all types of catalytic materials such as bulk and supported metals, bulk mixed metal oxides, supported metal oxides, bulk and supported metal sulfides, zeolites and molecular sieves, heteropolyoxo anions, and clays. Raman is also used to study chemisorption. There is also a strong driving force leading research toward the study of catalysts under reaction conditions (operando methodology) because such information could lead to the development of molecular structure-reactivity relationships and help the molecular engineering of new catalytic materials. Raman spectroscopy (amongst some others) is ideally suited for in situ molecular characterization of catalysts; because it can provide real-time analysis data, as an optical technique it does not require any sample pretreatment, and most of all it gives specific information on the molecular structures of studied materials.

Pros and Cons to Use Raman Spectroscopy in Catalysis Reseach

 

Advantages of Raman

  • Gives fundamental, molecular specific information about:
    • catalytic, active surface sites
    • surface reaction intermediates, and
    • Influence of different environmental conditions on these species
  • crystallinity of material can also be determined
  • In situ characterization in the real reaction conditions
  • Can be used for aqueous samples and water can be used as solvent

Disadvantages of Raman

  • Fluorescence which covers Raman signal and prevents the characterization TIMEGATED® SOLVES THIS PROBLEM
  • Photochemical effects
  • Thermal background covering the Raman signal in-situ reaction when reaction temperature exceeds 300-400°C TIMEGATED® SOLVES THIS PROBLEM