This work analyses and compares, under the same operating conditions (220 degrees C and 44 bar with a Ni-La/Al2O3 catalyst), the effects of some of the most common acid (CH3COOH, H2SO4, H3PO4) and basic (KOH and NaOH) biodiesel-derived impurities on the aqueous phase reforming (APR) of a 30 wt.% glycerol solution. The statistical analysis of the results revealed that the impurities did not greatly influence the initial reforming results. Conversely, they significantly influenced the catalyst deactivation, which resulted in different evolutions over time for the glycerol conversion, liquid production and the composition of the gas and liquid phases. Significant decreases over time in the glycerol conversion and liquid production were detected, the severity of the decay being as follows: H3PO4 (KOH = NaOH)> H2SO4 (KOH < NaOH)> CH3COOH (KOH < NaOH). The characterisation of the spent catalyst and the liquid phases revealed that poisoning/fouling, and catalyst active phase or support modification (leaching and crystalline phases alteration), were the major deactivation mechanisms. The proportions of metals (K or Na) deposited on the catalysts with the different acids was as follows: H3PO4 > H2SO4 > CH3 COOH. In addition, S and P were also deposited on the catalyst, while boehmite and other new crystalline phases were detected in the spent catalyst after the APR reaction. (C) 2017 Elsevier B.V. All rights reserved.