Activated Carbon Modified with Oxalic Acid as a Loader for Co(II)@AC Catalyst in the Oxidation of 1‐(4‐Chlorophenyl)‐pyrazolidin‐3‐one to 1‐(4‐Chlorophenyl)‐1 <i>H</i> ‐pyrazol‐3‐ol by Air

Abstract The production of 1‐(4‐chlorophenyl)‐1 H ‐pyrazol‐3‐ol by oxidizing 1‐(4‐chlorophenyl)‐ pyrazolidin‐3‐one with H 2 O 2 suffers from some shortcomings. The oxidation of 1‐(4‐chlorophenyl)‐pyrazolidin‐3‐one to 1‐(4‐chlorophenyl)‐1 H ‐pyrazol‐3‐ol can be realized by air catalyzed with Co(II)@AC (prepared by supporting cobalt(II) on activated carbon). Air is a good substitute for H 2 O 2 because it can minimize the cost, hazards, and pollution, which is beneficial to the improvement of the production process for pyraclostrobin. In this study, activated carbon has been modified by H 2 C 2 O 4 solution to improve the catalytic performance of Co(II)@AC. The experiments indicate that the best carbon is made by heating the carbon at 300 °C for 3 h with a heating rate of 5 °C/min in N 2 after being soaked in 0.4 mol/L H 2 C 2 O 4 solution at 50 °C for 12 h with an L/S ratio of 40/1 mL/g. The 1‐(4‐chlorophenyl)‐1 H ‐pyrazol‐3‐ol concentration obtained by Co(II)@AC immobilized on the optimized carbon is 39.39% over that catalyzed by Co(II)@AC loaded on the original carbon. Characterization results reveal that modification with H 2 C 2 O 4 increases the specific surface area and enhances the acidity on the carbon surface. The oxidation rate of 1‐(4‐chlorophenyl)‐pyrazolidin‐3‐one is primarily determined by the physical structure. The selectivity toward 1‐(4‐chlorophenyl)‐1 H ‐pyrazol‐3‐ol is mainly influenced by the chemical characteristics.