A wheat straw soda lignin was characterized and converted into gases and liquids under H-2 pressure, at 350 degrees C over a supported NiMo sulfide catalyst, using tetralin as a hydrogen-donor solvent in a batch autoclave. The aim of this work was to evaluate the transformations occurring during the temperature increasing step to reach a pseudo-t(0) and the impact of the catalyst presence in the mixture. A well-developed products separation protocol made possible to isolate and to characterize gases, organic liquid, lignin residue and solids (catalyst and char). A limited quantity of solids (or char) was produced however. As the lignin residue is one of the main intermediates of the lignin conversion pattern, the nature of this material has to be carefully determined. Thanks to several appropriate characterization techniques (GPC, NMR, FTIR), the conversion was followed and the lignin residue was compared to the initial lignin in order to understand the transformations occurring during the process. (C) 2013 Elsevier B.V. All rights reserved.