Abstract: The Cr-SZ/Al₂O₃ series solid superacid catalysts were prepared first by supporting Cr promoted SO₄^2-/ZrO₂(SZ) solid superacid catalysts, Cr-SZ, on γ-Al₂O₃ support. The variation rules of their superacidities, medium strong acidities and weak acidities were investigated by using model reactions. The surface area, sulfur content and zirconia crystallization as well as the catalytic activity of samples for n butane isomerization at low temperature were also studied in detail. It was shown that the both introducing Cr species and supporting Cr-SZ on γ-Al₂O₃ were beneficial to stabilize the tetragonal ZrO₂ crystal phase that are supposed to be one of the basic conditions of superacidity. Moreover the SO₃ contents of the supported samples were much larger than those of both Cr-SZ and SZ sample. The catalytic activities of some Cr-SZ samples for n butane isomerization were improved greatly after supporting them on γ-Al₂O₃. The improvement of both acidity and dehydrogenation ability of samples containing Cr makes contribution to the increasing of their catalytic activities for n butane isomerization. Cr-SZ/Al₂O₃ sample with proper acidity and dehydrogenation ability shows a high activity for n butane isomerization.

Key words: SO₄^2-/ZrO₂, γ-Al₂O₃, Cr promoted superacid, Supported superacid