The invention provides a preparation method of 2-pentyl-2-
cyclopentenone, and belongs to the technical field of
organic synthesis. The preparation method comprises the following steps: carrying out a first-stage
isomerization reaction on 2-pentylidene
cyclopentanone and a first composite catalyst in a first
atmosphere to obtain an intermediate, carrying out a second-stage
isomerization reaction on the intermediate and a second composite catalyst in a second
atmosphere, and controlling the volume ratio of
nitrogen to
hydrogen in the first
atmosphere and the second atmosphere to obtain the 2-pentylidene
cyclopentanone. In the first-stage
isomerization reaction, the conversion rate of converting 2-pentylidene
cyclopentanone into 2-pentyl-2-
cyclopentenone is increased, and in the second-stage isomerization reaction, the use amount of
hydrogen in the second atmosphere is reduced, the temperature of the second-stage isomerization reaction is increased, generation of by-products is inhibited, and the yield of 2-pentylidene cyclopentanone is increased. Further, the yield and the purity of the 2-pentyl-2-
cyclopentenone can be improved. According to the preparation method, the first-stage isomerization reaction and the second-stage isomerization reaction are continuous reactions, intermittent reactions are not needed, and the preparation method is more suitable for industrial application.