Oxychlorination of CO to phosgene in a three-step reaction cycle and corresponding catalytic mechanism

An improved procedure, three-step reaction cycle procedure, for the continuous preparation of phosgene from CO, air and HCl catalyzed by CuCl2 was reported for the first time. The corresponding catalytic mechanism of each step was preliminarily disclosed with the powder X-ray diffraction (XRD) analysis: the first step is the oxychlorination of CO to phosgene and simultaneous reduction of CuCl2 to CuCl; the second step is the oxidation of CuCl with air to Cu2OCl2, and the third step is the neutralization of Cu2OCl2 with HCl to CuCl2. The regeneration of catalyst consists of steps 2 and 3, which is called the two-step regeneration of catalyst. The no-simultaneous existence of Cu (I) chloride and water in this three-step reaction procedure prevented effectively copper (I) chloride from the disproportionation. The influence of regeneration conditions, including reaction time, pressure of air or HCl on morphologies and recovery degree of catalyst were investigated and discussed. The degree of recovery for the single-run yield and cumulative yield of phosgene from the two-step regenerated oxychlorination agent can reach, respectively, 87.0% and 97.0% whereas the single-run yield and cumulative yield of phosgene with the one-step regenerated catalyst only can be recovered to 58.8% and 80.5%, respectively. The two-step regeneration method also can result in a higher dispersion of CuCl2/KCl on silica gel than that of the one-step regeneration. These results not only can offer a quite promising potential for the industrial use, but also can promote our deeply understanding of this important industrial reaction.

Graphical abstractAn important three-step reaction cycle for oxychlorination of CO to phosgene catalyzed by CuCl2 was proposed, and the corresponding reaction mechanism was probed by the XRD measurements.Figure optionsDownload full-size imageDownload high-quality image (44 K)Download as PowerPoint slide