The hydrodesulfurization (HDS) of thiophene was studied over Ni2P/MCM-41 by in situ Fourier transform infrared (FTIR) spectroscopy and X-ray absorption near-edge structure (XANES) measurements at atmospheric pressure and 393-723 K (120-450 degrees C). FTIR showed the presence of adsorbed molecular thiophene principally on the MCM-41 support. In the presence of hydrogen new bands in the aliphatic CH stretching region (2953, 2918, and 2876 cm(-1)) and the CH2 scissoring region (1464 cm(-1)) appeared and grew with temperature up to 553 K (280 degrees C). These were assigned to a tetrahydrothiophene surface intermediate, whose presence is consistent with the high hydrogenation activity of nickel phosphide. XANES measurements between 353 and 573 K (180-300 degrees C) also showed growth of a signal (8330.9 eV) attributed to Ni-S interactions of either the adsorbed tetrahydrothiophene or a surface phosphosulfide. Transient XANES measurements showed that the sulfur species responded dynamically at the same rate as the steady-state rate, indicating that it was associated with an intermediate in the reaction. (c) 2009 Elsevier Inc. All rights reserved.