The synthesis of a new mesoporous support based on high surface area silicon nitride and its use as a solid superbase is reported. The 2,3-dimethylbut-1-ene isomerization is used as a test reaction to compare the activity of individual catalysts depending on the synthesis conditions of the support. Various impregnation methods and different metal loadings are studied. In particular, potassium catalysts, obtained by impregnation from ammoniacal solution, show high catalytic activity for alkene isomerization. Heat treatments of the support at 1273 K and potassium loadings up to 30% are beneficial for high conversion at low temperature.