How the Yield of Maleic Anhydride in n-Butane Oxidation, Using VPO Catalysts, was Improved Over the Years

Key patents for the oxidation of n-butane to maleic anhydride (MA) using V/P mixed metal oxides (VPO) have been analyzed to evidence the important parameters needed to optimize the catalytic behaviour. The important aspects for the optimization of the catalyst performance are the preparation of the precursor (VO)HPO₄·0.5H₂0, its activation to form the active catalyst VO₂P₂O₇ and a small amount of VOPO₄, the methodology of the addition of promoters, and the shaping of the catalyst. Even small, sustainable improvements in the MA yield (>1 %) achieved by improved, modified or optimized catalysts are significant on an industrial scale with the world production of MA being a respectable 2.7 Million tons/year. Although substantial improvements in MA yield have been achieved industrially over the past 40 years by improving the VPO catalyst composition and by optimizing process operations; the MA process remains, as practiced today, one of the least efficient industrial selective oxidation processes. Therefore, a huge incentive exists in the field to improve the MA catalyst and process, which led us to search for clues towards this end by analyzing the pertinent patent literature, as reported here.