Electrochemical Oxidation Of Hesigewula Lignite Coal Slurry In Alkaline Medium

The electrochemical oxidation experiments of Hesigewula lignite coal slurry in alkaline medium were investigated in an H-style diaphragm electrolytic reactor with three electrodes. The effects of electrochemical oxidation parameters such as electrode material, anode potential, reaction temperature, response time, coal particle size,coal slurry concentration and the alkaline electrolytic type and concentration on the reaction process and the composition of liquid products at the anode have been examined in order to obtain the relationship between different oxidation conditions and the end products. It turned out that water insoluble acid (WIA) was the main product, while the yield of water soluble acid was low. Based on oxidation efficiency and the yield of oxidation product, the optimal reaction conditions include Ni anodic,1.0V(vs. SCE),60℃,6h, more than150mesh of the granularity,33.33g/L of coal slurry concentration and8wt%of the KOH solution. And the maximum yield of WIA was88.09%(daf coal).The cyclic voltammetry curve demonstrates that Ni as the anode instead of Pt can generate larger oxidation current at the same anode potential. Ni and Pt were adopted as anode and cathode respectively, thus the anode potential of electrochemical oxidation could be significantly reduced. That’s because Ni posses lower oxygen overpotential while Pt posses lower hydrogen overpotential.We conducted the electrochemical oxidation of coal slurry at different anode potential employing the amperometric i-t curve method. It demonstrates that the electrochemical oxidation could proceed well with the anode potential at1.0V, higher potential can promote the coal to access the deep oxidation stage. With the increase of the anode potential, the oxidation current rises up while the oxidation efficiency decrease. The yields of the oxidation products reach the peak at1.0V. With the anode potential set at1.0V, the yields increase with the increment of the reaction temperature and the diminution of the coal coal particle size, and the yield curves firstly ascend then descend with the increase of the response time and coal slurry and alkaline electrolytic concentration. However, the types of alkaline medium do not affect the yields of oxidation product much. The effect of the reaction temperature on the effective current accord with Arrhenius Equation, and the apparent activation energy of electrochemical oxidation of Hesigewula lignite coal slurry is18.683kJ/mol in our experiments.The purity of hydrogen which produced at the cathode was very high, and the hydrogen evolution efficiency was closed to100%. In the early stage of the electrochemical oxidation, there was no gas. In the later period, gases generating speed gradually accelerated result in the decrease of oxidation efficiency, anode gases were mainly oxygen. Anodic oxidation products mainly include WIA and WSA, and given priority to the former. WIA was analyzed by means of infrared absorption spectrum, the result show that WIA was a kind of organic macromolecular compounds which containing a large amount of carbonyl, carboxyl and aromatic ring structure.