A detailed study of n-butane oxidation over vanadium phosphate catalysts derived from in situ activation of VOHPO4 . 0.5H(2)O modified with group 13 compounds or 2-norbonanemethanol is described and discussed. Two methods of preparation of VOHPO4 . 0.5H(2)O were studied: (a) the VPO method, in which V2O5 is reacted with H3PO4 in isobutanol, and (b) the VPD method, in which VOPO4. 2H(2)O is reacted with isobutanol. Group 13 additives (B, Al, Ga, In) were found to change the morphology of the VPO catalyst precursor from platelet-like to the rosette morphology usually associated with the VPD type of preparation. Although all act as structural modifiers, the In- and Ga-doped materials give improved catalyst performance for the synthesis of maleic anhydride from the selective oxidation of n-butane. The Al, Ga and In additives were added as acetylacetonates and it was found that addition of 1% acetylacetonate also enhances the catalyst performance, but does not act as a structural promoter. In view of this, the addition of 2-adamantanol and 2-norbonane methanol was investigated for the VPD-type preparation method. The addition of 2-norbonanemethanol was found to enhance the catalyst surface area of the activated catalyst, but the catalyst performance, with respect to both n-butane conversion and maleic anhydride selectivity, was not improved and this is considered to be due to the alcohol being strongly adsorbed on the catalyst surface.