Effect of Process Condition in Plasma Electrolysis of Chloralkali Production

Abstract

Chlor-alkali is one of the most important processes in chemical industry. This process produces chlorine and caustic soda that becomes the main feedstock of daily needs products. In this study, the process condition on chlorine gas production by electrolysis plasma is examined. Plasma electrolysis can increase the chlorine gas production up to 24 times in single compartment reactor and can reach up to 59 times in double compartment reactor compared to electrolysis process. In reactor with single compartment, high voltage results high current then cause high-energy consumption. The highest chlorine gas production is at 0.5 M and 300 V that results 4.63 mmol within 15 minutes. On the other hand, using double compartment reactor, current is lower due to its higher distance between two electrodes that makes the higher resistance. In this case, the highest chlorine gas production is at 0.5 M NaCl and 700 V that results 11.25 mmol within 15 minutes. The use of ion selective membrane can keep the movement of charge from one electrode to other. Ion selective membrane can separate side product of NaOH, but side reaction of chlorine ion still exists. NaCl, will be decomposed in the solvent and form ions in the solution. Positive discharge electrode is called anode and the negative one is cathode. Each electrode bonds ions which have different discharge, so that ions with negative discharge will go to anode and the positive ions will go to cathode. Nevertheless, electrolysis of NaCl solution (brine electrolysis) used in chlor-alkali production has significant weaknesses, those are low conversion resulted by the electrolysis process and the use of high electric current when the electrolysis process occur (4). Hence, it is needed to observe other possible technologies that can be applied in the production of chlor-alkali to reduce the energy consumption. One of the technologies that can reduce the energy consumption is plasma electrolysis. The plasma electrolysis process is similar with electrolysis process, but it is done with high enough voltage until the electric spark is formed producing the plasma on the electrolyte solution. The plasma will produce reactive species such as radicals on large amount which are accelerated by the sharp potential gradient and have enough kinetic energy to induce unique chemical changes in aqueous solutions, so it is able to increase the formation of products in solution several more times than the Faraday electrolysis process (5), (6). Using this technology may reduce the energy consumption several times than conventional electrolysis so the productivity is more effective (6).