Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve ...Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.展开更多
Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclu sion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown ...Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclu sion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of diacid calix[4]-1,3-crowns-4,5 were synthesized, and their inclusion-extraction parameters were optimized including the calixcrown scaffold （4.4%, by mass） as the carrier/demulsifier, the commercial kero sene as diluent in membrane, sulphonic acid （0.2 mol.L-1） and ammonium carbonate （0.4 mol.L-1） as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed （300 r.min-1）, and initial solute concentration （100 mg.L-1）. The selectivity of membrane over more than ten interfering cations was examined and the re sults reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98%-99%.展开更多
基金supported by the National Key R&D Program of China(2016YFC0203900,2016YFC0203901)National Natural Science Foundation of China(51778619,21577173)~~
文摘Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.
基金supported by Islamic Azad University (Shahreza Branch)Iran Nanotechnology Initiative Council
文摘Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclu sion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of diacid calix[4]-1,3-crowns-4,5 were synthesized, and their inclusion-extraction parameters were optimized including the calixcrown scaffold （4.4%, by mass） as the carrier/demulsifier, the commercial kero sene as diluent in membrane, sulphonic acid （0.2 mol.L-1） and ammonium carbonate （0.4 mol.L-1） as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed （300 r.min-1）, and initial solute concentration （100 mg.L-1）. The selectivity of membrane over more than ten interfering cations was examined and the re sults reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98%-99%.
