This paper focuses on understanding the electrolyte flow characteristics in a typical packed-bed electrochemical reactor using Residence Time Distribution (RTD) studies. RTD behavior was critically analyzed using tracer studies at various flow rates, initially under nonelectrolyzing conditions. Validation of these results using available theoretical models was carried out. Significant disparity in RTD curves under electrolyzing conditions was examined and details are recorded. Finally, a suitable mathematical model (Modified Dispersed Plug Flow Model (MDPFM)) was developed for validating these results under electrolyzing conditions.

The present work focuses on the effective utilization of discarded Lead dioxide particles as particulate electrodes in a carefully designed packed bed electrolyser. It is known that particulate electrodes provide a large electrode area in proportion to conventional flat electrode configuration. Consequently, this packed bed electrolyser, will be exceptionally useful when dealing with slow reactions. This design entirely avoids the necessity of expensive valve metals as substrates and associated noble metal oxide undercoating. In the present study, an optimized design of a packed bed electrochemical reactor setup using peeled off electro deposited Lead dioxide particles was carried out. The above electrolyser was used for studying its effectiveness in the electrochemical oxidation of Sodium Chlorate to Sodium Perchlorate, which is the starting raw material for the manufacture of rocket propellant oxidizers. Effect of certain parameters like electrolyte flow rates, current density and thickness in the desired current efficiencies for the formation of perchlorates were estimated. Results indicate that this electrolyser proves to be a potential method for improving the reaction rates of slow reactions like perchlorate formation, utilizing cheaper discarded Lead dioxide particles.

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Background: Sodium Perchlorate is one of the major starting intermediate product for the manufacture of various Perchlorates viz, Ammonium perchlorate as solid oxidizer and Strontium Perchlorate as Secondary Injection Thrust Vector Control (SITVC) in launch vehicles. This critical product is manufactured industrially by electrochemical oxidation of Sodium Chlorate solution at the anodic surface. Lead dioxide is preferred in various perchlorate cells because of its low cost. Infrequent detachment of Lead dioxide deposits from the substrate during electrolysis is a grave issue confronted by associated electrochemists in bulk manufacture of chemicals. Moreover, a cheaper alternative for continuous manufacture of Sodium Perchlorate using Lead dioxide electrodes has been an onus among various industrial electrochemists. Objective/ Benefits: Development of a suitable compact flow through electrochemical cell using superfluous or detached Lead dioxide crystals as ‘particle’ electrodes is the major objective of this paper. This compact bed electrochemical cell, is extraordinarily helpful when confronting with lesser reactant concentration or time consuming reactions. Besides, this proposal adds on flexibility in trimming the size of cells when compared with bulky design of conventional cells. Another objective was to demonstrate continuous electrosynthesis of Sodium perchlorate using Lead dioxide without resorting to expensive Platinum. Method: A suitable single bed and a dual bed compact electrochemical cell was made using HDPE body, perforated Poly Propylene distributor, detached Lead dioxide particles, nylon mesh, etc. Four such dual bed cells were made for final demonstration for continuous electro synthesis application. Results: From various experimental trials, an optimum values for temperature, flow rate and current load were determined as 600°C, 800 mL/min and 80 A respectively, in single bed system. Inorder to avoid current penetration issue, dual bed cells were employed. Subsequently, critical operational strategy and systematic configuration for arrangement of dual bed cells were made for demonstrating continuous bed electrochemical cells. Conclusion An average current efficiency of about 78.5% could be achieved which is 20-25 % higher than conventional parallel plate electrode system.