ABSTRACT
Octafluorocyclobutane (C4F8) with a GWP100 (global warming potential) of 10,000 times of CO2 is listed as potent greenhouse gas. Therefore, development of effective control technologies for reducing C4F8 emissions has become an emerging issue to be addressed. In this study, decomposition of C4F8 was investigated via three systems including catalytic hydrolysis, non-thermal plasma, and plasma catalysis, respectively. Decomposition of C4F8 achieved with catalytic hydrolysis reaches the highest efficiency of 20.1%, being obtained with γ-Al2O3 as catalyst in the presence of 10% H2O(g) and operating temperature of 800 °C. For plasma-based system, the highest C4F8 conversion obtained with non-thermal plasma is 62% at a voltage of 23 kV. As for the plasma catalysis system, 100% C4F8 conversion efficiency can be achieved at an applied voltage of 22-23 kV. The effects of various parameters such as gas flow rate and C4F8 concentration on plasma-based system show that the plasma catalysis also has better resistivity for the high gas flow rate. The highest energy efficiency of 0.75 g/kWh is obtained for the gas flow rate of 500 mL/min, with the C4F8 conversion of 41%. The highest conversion 89% was achieved with the O2 content of 0.5%. Addition of Ar improves the performance of plasma-based system. When Ar is controlled at 20%, C4F8 conversions obtained with plasma catalysis reach 100% at applied voltage of 22-23 kV even in the presence of 5% O2. The main products of the C4F8 conversion include CO2, NOx, and COF2 when O2 is added into the system. As water vapor is added, HF is also formed. This study has confirmed that combined non-thermal plasma with catalyst system to convert C4F8 is indeed feasible and has good potential for further development.
Subject(s)
Air Pollution , CatalysisABSTRACT
Surface Ag+ ions forming complexes with the amino (selenoamino) acids compounds have been studied at a silver nitrate-modified carbon paste electrode (AgNO3/CPE). The carboxyl, amidogen and selenium of selenoamino acids could coordinate with Ag+. The coordinating sites of Ag+-SeCys and Ag+-SeMet on electrode surface have been studied in the range of pH value from 1.0 to 12.0. The coordinating sites of Ag+-SeCys and Ag+-SeMet are due to the different configuration and electronegative charge of amino acids in different acidity. Increase of the coordination number of adsorbed species increases the average lifetime of these species on the surface, and hence causes that stronger bonded molecules more effectively prevent the depletion of the surface layer from the Ag+ ions. The voltammetric signals of Ag+-selenoamino acid and Ag+-sulfur-containing amino acid are stronger than those of Ag+-alanine due to the coordinating sites of AgS and AgSe bonds. Moreover, the adsorption of Ag+-selenoamino acid on electrode surface relates to different acidity.
