Method of producing unsaturated acid in fixed-bed catalytic partial oxidation reactor with high efficiency

A process for producing unsaturated acids from unsaturated aldehydes or alkanes by fixed-bed catalytic partial oxidation in a shell-and-tube heat exchanger-type reactor, wherein the reactor comprises a reaction zone for producing the unsaturated acids;

• the reaction zone is divided into two or more shell spaces by at least one partition;
• each of the divided shell spaces is independently heat-controlled;
• a heat transfer medium in the first shell space has a temperature ranging from the lowest active temperature of a catalyst layer packed in a reaction tube corresponding to the first shell space to the lowest active temperature of the catalyst layer plus 20° C., wherein the two or more shell spaces are sequentially referred to as the first shell space, the second shell space, . . ., the nth shell space;
• and the first shell space is controlled in such a manner that it provides an unsaturated aldehyde or alkane conversion contribution per length as defined in a following equation of 1.2 to 2.5:
• unsaturated aldehyde or alkane conversion contribution per length =(mole number of unsaturated aldehydes or alkanes that have reacted in the relevant catalyst layer zone/mole number of the total unsaturated aldehydes or alkanes supplied to the reaction zone)/volumetric ratio of the relevant catalyst layer zone to the total catalyst layer of the reaction zone.