The SOx uptake of second generation sulfur trapping materials was studied by in situ IR spectroscopy under lean-rich cycling conditions. The combination of advanced chemometric methods including generalized 2D correlation analysis, 2D sample-sample correlation analysis, and multivariate curve resolution with alternating least squares allowed the detection of the species involved in the storage process. The formation of the bulk sulfate species was always accompanied by the consumption of carbonates. The reduction of a transient surface sulfate species was identified as the key parameter in the storage process under dynamic conditions. Three distinct reaction regimes were differentiated on the industrial materials under SOx trapping conditions being imperceptible from conventional spectra.