Strict environmental regulations and declining quality of petroleum feedstocks have made sulfur removal one of the most important current problems in refining. A novel, high-activity Ni2P/SiO2 catalyst with exceptional activity in deep hydrodesulfurization (HDS) was studied by in situ extended X-ray absorption fine structure (EXAFS). The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) and were made possible by the use of a low-volume cell with cubic boron nitride windows. The spectra thus obtained reveal that the bulk Ni2P structure is stable at reaction conditions, but that the active surface has Ni-S bonds. (c) 2006 Elsevier Inc. All rights reserved.