Catalytic gas phase oxidation of propene to acrylic acid involves passing over two reaction zones containing different fixed bed catalysts comprising multi-metal oxide active components

摘要

Catalytic gas phase oxidation of propene to acrylic acid involves using two different fixed bed catalysts, in different reaction zones, with active components comprising multi-metal oxides of different composition and containing iron, molybdenum and optionally bismuth. Catalytic gas phase oxidation of propene to acrylic acid comprises: (i) reacting O2 and propene in a ratio of at least 1 and an inert gas; (ii) passing over a fixed bed catalyst (FBC) (FBC1), comprising a multi-metal oxide containing at least Mo, Fe and Bi, in a reaction zone (RZ) (A), the propene conversion and the subsequent acrolein and acrylic acid product formation being at least 90 mol.%, optionally in the presence of oxygen and/or inert gas in a ratio of O2:propene of at least 0.5; and (iii) passing over a second FBC (FBC2), comprising a predischarge active component(s) comprising a multi-metal oxide(s) containing at least Mo and Fe and a postdischarge active component(s) comprising a multi-metal oxide(s) containing at least Mo and V at least one of which also contains an amount of Bi that is smaller than in the first FBC, where the amount of Fe in a postdischarge component(s) is lower than in a predischarge component(s), in a second RZ (B), which is at a lower temperature than RZ (A), to give an acrolein conversion in RZ (B) of at least 90 mol.% and an acrylic acid selectivity over both reaction zones of at least 80 mol %.