A dynamic electrochemical technique was used for desulfurization of thiophene-containing solutions. First, adsorption of thiophene from an aqueous solution onto a platinum electrode surface and electrooxidative behavior of thiophene were studied using a cyclic voltammetry technique, and then, a square wave potentiometry method was utilized to electrochemically desulfurize the aqueous thiophene solution and a thiophene-containing model fuel. Results indicated that, for thiophene molecules, the best adsorption potential is 0.2 V and the maximum electrooxidation rate occurs at 1.1 V. Also, the optimal square wave frequency was found as 50 Hz. Ion chromatographic measurement of sulfate ion concentration revealed that reaction conversion was 100% in the electrooxidative desulfurization of aqueous thiophene solution. The high desulfurization efficiency can be attributed to excellent electrocatalytic activity of the platinum electrode and performing experiments at the best operating conditions. On the basis of gas chromatographically quantitated thiophene concentration in the hydrocarbon phase, desulfurization reactions reached a conversion of about 88% during electrooxidative desulfurization of a model fuel/aqueous electrolyte emulsion. The lower desulfurization efficiency can be attributed to addition of a mass transfer (from hydrocarbon to aqueous phase) resistance and lessening the overall thiophene concentration. Ion chromatographic analysis of the aqueous phase revealed that only 38% of thiophene molecules were completely oxidized to sulfate ions. Fourier transform infrared spectroscopy studies of the hydrocarbon and the aqueous phases showed that the remaining part of converted thiophene molecules were partially oxidized to a sulfone and an organic sulfate compound. Due to polarity of these components, which results in their aqueous phase solubility, no more steps were required to separate the products of desulfurization from the hydrocarbon phase. On the basis of the obtained results, electrochemical desulfurization can be proposed as an effective alternative for the commercial hydrodesulfurization processes.
La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ nanopowder, synthesized via an autocombustion technique, was pressed into disk-shaped membranes. Results of permeation experiments revealed that oxygen permeation flux increases as temperature, feed side oxygen partial pressure, and feed and sweep gas flow rates increase, while it decreases with membrane thickness and permeate side oxygen partial pressure. A Nernst−Planck based mathematical model, including surface exchange kinetics and bulk diffusion, was developed to predict oxygen permeation flux. Considering nonelementary surface reactions and introducing system hydrodynamics into the model resulted in an excellent agreement (RMSD = 0.0344, AAD = 0.0274 and R 2 = 0.9960) between predicted and measured fluxes. Feed side surface exchange reactions, bulk diffusion, and permeate side surface exchange reaction resistances are in the range of R ex ′ = 7 × 10 3 to 9 × 10 6 , R diff = 1 × 10 5 to 2 × 10 7 , and R ex ″ = 1 × 10 4 to 2 × 10 7 (s/m), respectively. The permeation rate-limiting step was determined using the membrane dimensionless characteristic thickness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.