Experimental and Theoretical Study of Deactivated HDT Catalysts by Si Species Deposited on their Surfaces: Models Proposition, Structural and Thermodynamic Analysis

•Study combining 29Si and 13C CP/MAS NMR experiments and DFT calculations.•It has been investigated the poisoning process of HTD catalysts by silicon species.•It has been made a appropriate assignment of the resonances found in NMR spectra.•It has been identified the probable species that are present in the contamination.•The amorphous silica formation process on the γ-2O3 surface is spontaneous.