Complex metal-oxide catalysts for selective oxidation of propane and derivatives: I. Catalysts preparation and application in propane selective oxidation to acrylic acid

Several parameters involved in preparing the complex metal-oxide (CMO) catalysts (M a V b Te c Nb d O n , M: Mo and W) for the selective oxidation of propane to acrylic acid (AA) were investigated and discussed. These include the role each metal element plays and the effects on the performance of the catalysts exerted by the proper metal ratio, as well as various preparation methods, such as the mixing of starting chemicals to form an aqueous precursor mixture, the solvent removal, and the proper calcination atmosphere and gas flow. It was found that each metal element plays a critical role and while an appropriate MoVTeNb metal ratio is critical to the formation of an effective catalyst, each and every step of the preparation methods also have profound effects on the structures and performance of the resulting catalysts. The preferred preparation method for an effective MoVTeNb oxide catalyst includes the intimate mixing of all starting chemicals to form a precursor solution, drying via rotavap for solvent removal followed by calcination under a non-flow inert atmosphere. Using this preferred preparation method, effective complex metal-oxide catalysts can be prepared which affords up to 73% propane conversion and 42% one-pass yield to acrylic acid, while undesirable preparation methods, in contrast, lead to very ineffective catalysts of the identical composition.