Abstract This work examines the characteristics and performance of lanthanide-promoted zirconia catalysts for synthesis of isobutene from syngas (isosynthesis). Several mixed-metal-oxide catalysts employing a range of modifier species are considered. The catalysts examined include lanthana-promoted zirconia (La-ZrO 2 ), ceria-promoted zirconia (Ce-ZrO 2 ) and lanthana–ceria–zirconia (LaCe–ZrO 2 ). The addition of metal promoters to zirconia is known to have an effect on the physicochemical properties of the catalyst which in turn affects catalytic performance for isosynthesis. In this work, catalyst properties are characterized via a number of diagnostic techniques including N 2 physisorption, X-ray diffraction, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis following pyridine chemisorption. Isosynthesis activity is evaluated in a packed bed reactor configuration and the results are analyzed in terms of the physicochemical characteristics of the catalysts. Catalyst activity test results indicate that such modifiers have a strong effect on carbon monoxide conversion and selectivity to isobutene.