The conversion of pure 1-butene over WO3-TiO2 catalysts has been studied in a flow microreactor at 693 K and at 723 K. For comparison, experiments have also been carried out on the bare TiO2 support. Significant activity in the skeletal isomerization has been found, together with double bond migration, cis-trans isomerization, hydrogenation and cracking. By increasing time-on-stream the conversion of 1-butene is increasingly limited due to the formation of carbon residues on the catalyst surfaces. Working with tau = 6.44 h at 723 K (9.33 % WO3 by weight), the selectivity to products different from n-butenes decreases from nearly 75% after 15 min time-on-stream to less than 6% after 3 h. Initial selectivity to isobutene also decreases from nearly 14% to less than 2% after 3 h. A Fourier transform infrared study suggests that catalyst deactivation is due to the oligomerization of butenes on the surface Bronsted acid sites. Carbon residues formed are largely constituted of aromatized butene polymers anchored to the surface through carboxylate and alcoholate groups. Burning of the carbon residue occurs at 623-723 K and restores catalytic activity. The activity and the deactivation of the bare commercial TiO2 SUPPort is attributed to the weaker Bronsted acidity arising from silica impurities observed on the surface.