Vapor-phase catalytic dehydration of 1,2-propanediol was investigated over several solid acid catalysts, such as alumina, silica alumina, HY zeolite, and beta-zeolite. These acids catalyzed the dehydration of 1,2-propanediol to produce propanal (Figure 1), while zeolites were particularly deactivated because of deposition of carbonaceous species. An amorphous silica-alumina was modified with metals such as Ag and Cu to stabilize the catalytic activity under hydrogen flow conditions. Ag-modified silica alumina is a promising catalyst for the production of propanal from 1,2-propanediol.