Infrared spectroscopy isomerisation

New data treatment methods such as 2D correlation infrared spectroscopy (2D-COS) lead to significant improvements for in situ studies. We report here the application of 2D-COS to the in situ infrared study of orthoxylene isomerisation in H-MFI zeoiite in working conditions. This led to improve the quantitative monitoring of xylene isomers in the micropores of the solid and to the detection of traces of coke in the catalyst. A correlation was found between coke and the perturbation of specific hydroxy groups in the solid. 

This behaviour is reminiscent of dynamical averaging seen in NMR spectroscopy, which is treated using a Bloch-equation analysis. Turner and coworkers were the first to use this type of analysis of dynamic infrared spectra to calculate rate constants and self-isomerisation barrier heights in the case of a turnstile -type exchange of CO ligands observed in trigonal bipyramidal [(q -diene)Fe(CO)3] complexes. In a similar fashion, rate constants for electron transfer in the ruthenium cluster dimers were calculated from the lineshapes of the (—1) states. As expected from the electrochemical data, the rate constant was fastest for the most electronically coupled dimer (1) and slowest for the... 

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