Method for the production of cyclopentanone

A process for preparing cyclopentanone comprising the following steps (i) to (iii):

• (i) providing a mixture G(i) comprising cyclopentene;
• (ii) providing liquid or supercritical N2O or a liquid or supercritical gas mixture G(ii) comprising at least 20% by volume of N2O, based on the total volume of the mixture G(ii);
• (iii) contacting the mixture G(i) with the liquid or supercritical N2O or with the liquid or supercritical mixture G(ii) to obtain a mixture G(iii) comprising cyclopentanone,
• wherein the mixture G(i) contains at least 25% by weight and at most 95% by weight, of cyclopentene, based on the total weight of the mixture G(i),
• wherein the gas mixture G(ii) used is at least one dinitrogen monoxide containing offgas of a chemical process, and said mixture G(ii) has an N2O content in a range from 20 to 97 percent by volume,
• and wherein, in step (iii), the mixtures G(i) and G(ii) are contacted in a continuous reactor at temperatures in the range from 200 to 290° C. and pressures in the range from 10 to 400 bar, wherein the residence time of the reaction mixture in the continuous reactor is in a range from 0.3 to 2.5 hours.