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In this research, the effects of process variables on the efficiency and mechanism of dibenzothiophene oxidation in formicacid/H2O2 system for deep desulfurization of a light hydrocarbon model were systematically studied by statistical modelling and optimization using response surface methodology and implementing the central composite design. A quadratic regression model was developed to predict the yield of sulfur oxidation as the model response. The model indicated that temperature was the most significant effective factor and suggested an important interaction between temperature and H2O2/sulfur ratio; at temperatures above 56°C, more excess oxidant was necessary because of instability of active peroxo intermediates and loss of H2O2 due to thermal decomposition. In contrast, the water hindrance effect of H2O2 aqueous solution in desulfurization progress was more significant at temperatures bellow 56°C. In the optimization process, minimizing H2O2/sulfur ratio and catalyst consumption for maximum yield of desulfurization was economically considerable. The optimal condition was obtained at temperature of 57 °C, H2O2/sulfur ratio of 2.5 mol/mol and catalyst dosage of 0.82 mL in 50 mL solution of DBT in n-hexane leading to a maximum oxidation yield of 95% after 1 hour reaction. Good agreement between predicted and experimental results (less than 4% error) was found.

The drive toward greater application of membrane has resulted in its rapid development in natural gas processing industry. In this work, amine-mediated membranes were tailored for C02 removal from C02/CH4 stream. The effects of various parameters such as amine concentration, microporous support, feed pressure and composition were examined to study the permeation behavior of pure and mixed gases. Generally, C02 transport through the DEA-PVA membranes was higher than that of MEA-PVA membranes for approximately 70%. The membrane containing 15 wt% DEA and 35 wt% MEA revealed higher permselectivity. C02 permeance enhancement of amine-PVA membranes in comparison with neat PVA membrane, confirmed that C02-amine reaction was the dominant transport mechanism. Additionally, with increasing feed pressure, C02/CH4 permselectivity decreased due to carrier saturation. However, lower partial pressure of C02 was in favor of reaction mechanism in pure and mixed gas tests. On the other hand, CH4 is not significantly affected by feed pressure confirming that solution-diffusion is the governing transport mechanism. Additionally, PTFE support with higher wettability showed better performance (+8%) regardless of amine type, concentration and feed pressure. DEA-PVA membrane has exhibited good stability during 2 weeks, unlike MEA-impregnated membrane, which was probably due to carrier degradation over time. POLYM. ENG. SCI., 54:1268-1279, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION C[O.sub.2] removal from gas mixtures plays an important role in industries such as C[O.sub.2]/[N.sub.2] separation (C[O.sub.2] capturing from off-gas or flue gases for greenhouse gas emissions control) and C[O.sub.2]/C[H.sub.4] [...]