In view of the growing energy demand and the current climate problems, renewable energy sources are becoming increasingly popular. The so-called biosyngas obtained from the gasification of dry biomass can be used to synthesize fuels and basic chemicals. Besides gaseous by-products and salts, this gas contains tar which needs to be removed before downstream processing. Catalysts like Mo/V/W-oxides were found to be inert towards the oxidation of CO and H-2 but are able to activate the tar model compound naphthalene highly selective. Unfortunately, besides the total oxidation, the partial oxidation to the undesired intermediates phthalic acid anhydride and maleic acid anhydride takes place. Modification of the catalyst with bases leads to synergetic effects on the catalyst surface, the total oxidation is promoted, and the formation of intermediates decreases.