The purpose of this study was to investigate the sulphur deactivation mechanism during an industrial methanation process, but also after catalyst regeneration. In the present work we extended our computational investigations to study the adsorption of sulphur poisoning compounds on the Ni/Al(2)O(3) catalyst. The focus was to study possible catalyst changes and thus the modified catalytical behaviour of the nickel particles, as well as to see differences in the poisoning behaviour, when sulphur adsorbs either on the Ni particle or on the support. This was done using Density Functional Theory calculations (StoBe) with cluster model and non-local functional (RPBE) approach. For modelling the catalyst, an Al(15)O(40)H(35) cluster has been selected representing the gamma-Al(2)O(3)(1 0 0) surface, and Ni metal particles of different sizes were cut from a Ni(1 0 0) surface and deposited on the Al(15)O(40)H(35) cluster. Several poisoning agents have been found to be stable on both Ni clusters and alumina support such as COS, H(2)S, or hydrogen thiocarbonates. (C) 2010 Elsevier B.V. All rights reserved.