1.
Alkali metal poisoning of a CeO2-WO3 catalyst used in the selective catalytic reduction of NOx with NH3: an experimental and theoretical study.
Peng, Y, Li, J, Chen, L, Chen, J, Han, J, Zhang, H, Han, W
Environmental science & technology. 2012;(5):2864-9
Abstract
The alkali metal-induced deactivation of a novel CeO(2)-WO(3) (CeW) catalyst used for selective catalytic reduction (SCR) was investigated. The CeW catalyst could resist greater amounts of alkali metals than V(2)O(5)-WO(3)/TiO(2). At the same molar concentration, the K-poisoned catalyst exhibited a greater loss in activity compared with the Na-poisoned catalyst below 200 °C. A combination of experimental and theoretical methods, including NH(3)-TPD, DRIFTS, H(2)-TPR, and density functional theory (DFT) calculations, were used to elucidate the mechanism of the alkali metal deactivation of the CeW catalyst in SCR reaction. Experiments results indicated that decreases in the reduction activity and the quantity of Brønsted acid sites rather than the acid strength were responsible for the catalyst deactivation. The DFT calculations revealed that Na and K could easily adsorb on the CeW (110) surface and that the surface oxygen could migrate to cover the active tungsten, and then inhibit the SCR of NO(x) with ammonia. Hot water washing is a convenient and effective method to regenerate alkali metal-poisoned CeW catalysts, and the catalytic activity could be recovered 90% of the fresh catalyst.
2.
Effect of carbon source and COD/NO₃⁻-N ratio on anaerobic simultaneous denitrification and methanogenesis for high-strength wastewater treatment.
Xie, L, Chen, J, Wang, R, Zhou, Q
Journal of bioscience and bioengineering. 2012;(6):759-64
Abstract
The effect of carbon source and COD/NO(3)(-)-N ratio on denitrification and methanogenesis in mixed methanogenic matrix was investigated in this study. Industrial wastewater, anaerobic treated cassava stillage (CS) and glucose synthetic wastewater were used as carbon sources respectively for comparison. Experimental results showed that denitrification was the main nitrate reduction pathway for all COD/NO(3)(-)-N ratios tested in two substrates. Simultaneous denitrification and methanogenesis occurred at COD/NO(3)(-)-N higher than 7 regardless of carbon sources. Incomplete denitrification was observed at COD/NO(3)(-)-N ratio below 7 in both the anaerobic effluent of CS and glucose-fed cultures due to the insufficient available organic carbon. The nature of carbon sources was observed to play a key role in the nitrate and organic carbon utilization rates. COD/NO(3)(-)-N ratio had a strong effect on the organic matter utilization pathways. Methanization consumed more organic matter than denitrification with further increase of COD/NO(3)(-)-N ratio above 7 in two substrates. Results of VFA variation suggested that propionate and butyrate were preferably utilized by the denitrifiers than acetate.
3.
Pharmacokinetics of three organic nitrates in Chinese healthy male volunteers.
Chen, J, Jiang, XG, Cai, L, Lu, W, Gao, KP, Shi, ZQ, Zhang, QZ
Arzneimittel-Forschung. 2004;(4):203-6
Abstract
Eighteen Chinese male subjects completed a single-blind, randomized, three-treatment, three-period, cross-over study. In each treatment phase, subjects received a single dose of 20 mg isosorbide dinitrate (CAS 87-33-2, ISDN) intravenous infusion, 20 mg isosorbide 5-mononitrate (CAS 16051-77-7, 5-ISMN) tablet or 20 mg isosorbide 5-mononitrate intravenous infusion. Each consecutive dosing was separated by a washout period of 7 days. Following each dosing, venous blood samples were collected over a period of 16 h. Plasma concentrations of ISDN and its two active metabolites isosorbide 2-mononitrate (2-ISMN), 5-ISMN had been measured by a validated gas chromatographic method. Various pharmacokinetic parameters including AUC0-t, AUC0-infinity, Cmax, tmax, t1/2, Kelm and MRT were determined for the three formulations and found to be in good agreement with literature values. AUC0-t and AUC0-infinity of 5-ISMN tablet and intravenous infusion were 2694 +/- 496 ng x ml(-1) x h vs. 2548 +/- 556 ng x ml(-1) x h and 3266 +/- 624 ng x ml(-1) x h vs. 3178 +/- 769 ng x ml(-1) x h, respectively, and the relative bioavailability of 5-ISMN tablet was 105 +/- 20%. As compared with 5-ISMN intravenous infusion, ISDN can rapidly reach the plateau concentration and metabolize to its active metabolites 5-ISMN and 2-ISMN, which both have vasodilator effect. The results of this study suggest that as evaluated from the pharmacokinetic profiles of the three formulations, 5-ISMN tablet and ISDN intravenous infusion are ideal vasodilators and anti-angina drugs especially in acute conditions due to their rapid onset and long duration of action.