Processes for producing an α,β-unsaturated carboxylic acid, such as acrylic acid, or a salt thereof, using treated solid oxides are disclosed. The treated solid oxides can be calcined solid oxides, metal-treated solid oxides, or metal-treated chemically-modified solid oxides, illustrative examples of which can include sodium-treated alumina, calcium-treated alumina, zinc-treated alumina, sodium-treated sulfated alumina, sodium-treated fluorided silica-coated alumina, and similar materials.