| Cyclohexanone and cyclohexanol as industrial raw material,are employed to be oxidized to produce adipic acid,as an important aliphatic dicarboxylic acid which is widely used in the manufacture of nylon-66,plasticizer,fiber and food additive.How to greenly produce adipic acid is to gain the attention of chemical industries.Herein,we proposed a method,i.e.constant piezoelectric electrodeposition to prepare a nano-Pt loading porous Ti membrane electrode（Pt/Ti）,which is used as a cathode to construct an electrocatalytic membrane reactor（ECMR）for the electrochemical oxidation of cyclohexanone and cyclohexanol to produce sodium adipate（SA）and cyclohexanone/SA.Porous titanium membrane as the substrate,the chloroplatinic acid as the raw material,Pt catalyst was coated onto the surface and inside pore of Ti membrane（average pore size 7.0μm）by constant piezoelectric electrodeposition to fabricate nano-Pt/Ti membrane electrode.The morphology and electrochemical performance of Pt/Ti electrode was optimized by controlling the electrodeposition time and other factors.The morphology structure and electrochemical activity of the Pt/Ti electrode was characterized by field-emission scanning electron microscopy（FESEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray diffraction（XRD）,X-ray diffraction spectrometer（XPS）,high performance liquid chromatography（HPLC）,gas chromatograph（GC）and electrochemical workstation.The results show that the Pt/Ti electrode with 18.1 nm of Pt nanoparticles and 1.15 cm2 of electrochemical active area was successfully prepared under the electrodeposition time of 600 s and the operating voltage of-0.2 V.The electrode also displayed the best electrochemical performance.The Pt/Ti electrode as an anode and a stainless steel mesh as a cathode was employed to constitute ECMR to produce sodium adipate from cyclohexanone oxidation.It could be found that 81.1%conversion of cyclohexanone and 99.0%selectivity of sodium adipate were obtained under the optimum operating conditions:a concentration of cyclohexanone of 30.0 m M L-1,reaction temperature 30.0°C,a residence time of 50.0 min,a constant current density of 2.17 m A cm-2.The interaction of ECMR operating parameters was explored by response surface methodology（RSM）.These results indicated that 88.3%conversion of cyclohexanone and 99.0%selectivity of sodium adipate were obtained under the ECMR optimum operating conditions such as a reaction temperature of 30.8°C,a concentration of cyclohexanone of 22.5 m M L-1,a residence time of 50.0 min,a constant current density of 2.07 m A cm-2.It is noted that the sequence of the effect on the conversion of cyclohexanone was residence time>cyclohexanone concentration>reaction temperature>constant current density.The interaction of the residence time and reaction temperature was the most significant.In addition,the selectivity of sodium adipate was consistently higher than 99.0%.Besides,the relationship between the predicted value and the actual value can be estimated through diagnostic mapping.The results illustrated that the actual value obtained under the simulation conditions was a good agreement with the predicted value,indicating that the regression model has a good fitting degree.The results of chronoamperometry show that enhanced convective mass transfer is an important reason for the high efficiency of ECMR.Further,the Pt/Ti electrode as an anode and a stainless steel mesh as a cathode were employed to constitute ECMR to produce cyclohexanone and SA from the oxidation of cyclohexanol.It is found that 55.7%conversion of cyclohexanol and36.9%and 62.1%selectivity to cyclohexanone and SA were obtained under the optimum operating conditions:a concentration of cyclohexanol of 30.0 m M L-1,a room temperature（25.0°C）,a residence time of 50.0 min,a constant current density of2.17 m A cm-2.In sum,the green and controllable production of cyclohexanone and SA can be achieved from the oxidation of cyclohexanone and cyclohexanol by our ECMR. |
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