Patent ID: 7816559

Claim:
A method of producing unsaturated acids from olefins via fixed-bed catalytic partial oxidation in a shell-and-tube heat exchanger type reactor, wherein the reactor comprises at least one reaction tube; at least one first-step catalyst layer and at least two second-step catalyst layers are packed sequentially into each reaction tube without a layer made of inactive materials between the first-step catalyst layer and the second-step catalyst layer; in the first-step catalyst layer, olefins are oxidized by a first-step catalyst to mainly produce unsaturated aldehydes, and in the second-step catalyst layer, the unsaturated aldehydes are oxidized by a second-step catalyst to produce unsaturated acids; and when the second-step catalyst layers have at least two catalyst layers and the catalyst layer among the second-step catalyst layers, which is disposed right adjacent to the first-step catalyst layer, is named as the first catalyst layer of the second-step catalyst layers, the first catalyst layer of the second-step catalyst layers has an activity corresponding to 5˜30% of an activity of a catalyst layer having a highest activity among the second-step catalyst layers, wherein the first-step catalyst is a composite oxide based on molybdenum and bismuth, and the second-step catalyst is a composite oxide based on molybdenum and vanadium.