The catalytic activities of Al-ZSM-22 (Al in the framework) and Fe-ZSM-22 (Fe in the framework) were compared in the skeletal isomerization of 1-butene to isobutene. The catalysts synthesized in the laboratory were characterized by means of XRD, FTIR spectroscopy, SEM and surface area measurements. The activity of the zeolites was investigated using a fixed-bed microreactor system. Al-ZSM-22 demonstrated higher activity in 1-butene transformation compared to Fe-ZSM-22, while the selectivity to isobutene, on the other hand, was higher over Fe-ZSM-22. Coke formation was monitored using a microbalance and the results showed that the weight gain of Fe-ZSM-22 was slightly higher compared to Al-ZSM-22.