DRIFT study of manganese/ titania-based catalysts for low-temperature selective catalytic reduction of NO with NH3

Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/ TiO2 and Fe(0.1)-Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)-Mn(0.4)/ TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on catalyst could react with NH4+ leading to the reduction of NO. Therefore, it was suggested that the SCR reaction on Fe(0.1)-Mn(0.4)/TiO2 could also take place in a different way from the reactions on Mn(0.4)/TiO2 proposed by other researchers. Furthermore, the SCR reaction steps for these two kinds of catalysts were proposed.     

Enhancement of activity and sulfur resistance of CeO2 supported on TiO2-SiO2 for the selective catalytic reduction of NO by NH3

A series of novel metal-oxide-supported CeO(2) catalysts were prepared via the wet impregnation method, and their NH(3)-SCR activities were investigated. The Ce/TiO(2)-SiO(2) catalyst with a Ti/Si mass ratio of 3/1 exhibited superior NH(3)-SCR activity and high N(2) selectivity in the temperature range of 250-450 °C. The characterization results revealed that the activity enhancement was correlated with the properties of the support material. Cerium was highly dispersed on the TiO(2)-SiO(2) binary metal oxide support, and the interaction of Ti and Si resulted in greater conversion of Ce(4+) to Ce(3+) on the surface of the catalyst compared to that on the single metal oxide supports. As a result of in the increased number of acid sites on Ce/TiO(2)-SiO(2) that resulted from the addition of SiO(2), the NH(3) adsorption capacity was significantly improved. All of these factors played significant roles in the high SCR activity. More importantly, Ce/TiO(2)-SiO(2) exhibited strong resistance to SO(2) and H(2)O poisoning. After the addition of SiO(2), the number of Lewis-acid sites was not decreased, but the number of Br?nsted-acid sites on the TiO(2)-SiO(2) carrier was increased. The introduction of SiO(2) further weakened the alkalinity over the surface of the Ce/TiO(2)-SiO(2) catalyst, which resulted in sulfate not easily accumulating on the surface of the Ce/TiO(2)-SiO(2) catalyst in comparison with Ce/TiO(2).     

DRIFT study on cerium-tungsten/titania catalyst for selective catalytic reduction of NOx with NH3

CeO(2)/TiO(2) and CeO(2)-WO(3)/TiO(2) catalysts prepared by impregnation method assisted with ultrasonic energy were investigated on the selective catalytic reduction (SCR) of NO(x) (NO and NO(2)) by NH(3). The catalytic activity of 10% CeO(2)/TiO(2) (CeTi) was greatly enhanced by the addition of 6% WO(3) in the broad temperature range of 200-500 °C, the promotion mechanism was proposed on basis of the results of in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH(3) was introduced into both catalysts preadsorbed with NO + O(2), SCR would not proceed except for the reaction between NO(2) and ammonia. For CeO(2)/TiO(2) catalysts, coordinated NH(3) linked to Lewis acid sites were the main adsorbed ammonia species. When NO + O(2) was introduced, all the ammonia species consumed rapidly, indicating that these species could react with NO(x) effectively. Two different reaction routes, L-H mechanism at low temperature (<200 °C) and E-R mechanism at high temperatures (>200 °C), were presented for SCR reaction over CeO(2)/TiO(2) catalyst. For CeO(2)-WO(3)/TiO(2) catalysts, the Lewis acid sites on Ce(4+) state could be converted to Br?nsted acid sites due to the unsaturated coordination of Ce(n+) and W(n+) ions. When NO + O(2) was introduced, the reaction proceeded more quickly than that on CeO(2)/TiO(2). The reaction route mainly followed E-R mechanism in the temperature range investigated (150-350 °C) over CeO(2)-WO(3)/TiO(2) catalysts. Tungstation was beneficial for the formation of Ce(3+), which would influence the active sites of the catalyst and further change the mechanisms of SCR reaction. In this way, the cooperation of tungstation and the presence of Ce(3+) state resulted in the better activity of CeO(2)-WO(3)/TiO(2) compared to that of CeO(2)/TiO(2).     

Ce-Ti Amorphous Oxides for Selective Catalytic Reduction of NO with NH(3): Confirmation of Ce-O-Ti Active Sites

The amorphous Ce-Ti mixed oxides were reported to be catalysts for selective catalytic reduction of NO(x) with NH(3), in which Ce and not Ti acts as their solvent in spite of the fact that Ce is low in content. The amorphous catalysts were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) equipped with selective area electron diffraction (SAED). The Ce-Ti amorphous oxide shows higher activity than its crystalline counterpart at lower temperatures. Moreover, the presence of small CeO(2) crystallites as for the impregnated sample is deleterious to activity. The Ce-O-Ti short-range order species with the interaction between Ce and Ti in atomic scale was confirmed for the first time to be the active site using temperature programmed reduction with H(2) (H(2)-TPR), in situ FTIR spectra of NO adsorption, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine-structure (XAFS). Lastly, the Ce-O-Ti structure was directly observed by field-emission TEM (FETEM).     

Alkali metal poisoning of a CeO2-WO3 catalyst used in the selective catalytic reduction of NOx with NH3: an experimental and theoretical study

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 Br?nsted 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.     

采用蒸汽爆破处理技术降低卷烟主流烟气中氨释放量的研究

为降低卷烟主流烟气中氨释放量,采用蒸汽爆破技术对会理地区红大B2F等级烟丝进行处理。考察了在不同压力条件下,蒸汽爆破对烟丝常规化学成分以及主流烟气中氨释放量和感官品质影响。结果表明蒸汽爆破处理可使烟丝主流烟气中氨释放量明显降低,最大降幅为20.54%;当蒸汽爆破压力为0.4 MPa时,在降低烟丝主流烟气中氨释放量之外,卷烟感官品质也得到一定改善。     

氨氮的AOPs实验研究及其反应机理探讨

采用高级氧化技术(AOP3)氧化降解含氨氮的废水,实验研究了不同pH、不同初始氨及H2O2浓度对反应过程的影响.根据H2O2/O3产生自由基@OH机理,推导出含氨氮废水H2O2/O3AOP3氧化降解过程的动力学模型,初步探讨了H2O2/O3产生自由基@OH理和氨氮废水的氧化降解过程.通过实验研究与分析得出的氨氮H2O2/O3氧化过程的结果与理论模型相吻合.     

Photocatalytic reduction of Cr(VI) in the presence of NO3- and Cl- electrolytes as influenced by Fe(III)

Photoreduction of Cr(VI) involving Fe is strongly affected by the presence of organic or inorganic compounds in an acidic environment. In this study, we have found a new pathway of Cr(VI) photoreduction in the presence of Fe-(III) that is influenced by two inorganic electrolytes (i.e., NO3- and Cl-) and the pH. In NO3- and Cl- systems without Fe(III), Cr(VI) photoreduction could occur and was independent of the Cr(VI) concentration. The zero-order rate constant of the photoreduction reaction increased when the solution pH was decreased from 2 to 1; the reaction rate was higher in the NO3- system than in the Cl- system. The higher reaction rate in the NO3- system was attributed to the photolysis of NO3-, which resulted in the formation of NO2- for reduction of Cr(VI). Conversely, the effect of Fe-(III) addition on the increase in Cr(VI) photoreduction rate in the Cl- system was more significant than that in the NO3- system. The addition of Fe(III) to the Cl- system caused the formation of [Fe(OH2)5Cl]2+, the photolysis of which subsequently resulted in the formation of Fe(II) for reduction of the Cr(VI). This study suggests that the photolysis of NO3- and Fe-Cl complex may contribute significantly to Cr(VI) reduction in surface water that receives electroplating wastewater containing high levels of NO3-, Cl-, and Fe-(III). Therefore, under the acidic conditions that are favorable for Fe-Cl complex formation or in the presence of NO3-, the effects of inorganic components on Cr(VI) photoreduction cannot be ignored for the precise evaluation of the transformation of Cr in the environment.     

10℃K+,NH+4//NO-3-CH3OH,H2O混合溶剂体系相平衡研究

文章选择CH3OH作为添加剂,测定10℃条件下不同浓度(0%～60%)的CH3OH对K+,NH+4∥NO-3-H2O体系相平衡的影响,结果表明在无CH3OH加入时,体系中平衡固相有硝酸钾、硝酸铵和硝酸钾铵三种盐;随着CH3OH浓度的增大,硝酸钾结晶区显著增大;当CH3OH浓度大于50%时,体系中的硝酸钾铵混晶区完全消失.     

硝酸铵追肥对生长后期NC89叶片中硝酸还原酶和转化酶活性的影响

采用盆栽试验,研究了硝酸铵追肥量和追肥时期对生长后期NC89叶片中碳氮代谢关键酶———硝酸还原酶(NR)和转化酶(Inv)活性的影响。结果表明:在上、下部叶成熟过程中,NR和Inv活性下降。随追肥时期的推迟和追肥量增加,下部叶NR和Inv活性提高,Inv/NR比值较低且最大值出现时期延后;追氮量小或追肥期早的处理,上部叶NR和Inv活性I、nv/NR较低。移栽后30d追肥,追氮量30%时,烟株上、下部叶成熟过程中碳氮代谢协调,适时地从以氮代谢为主转变为以碳代谢为主。     

不同硝铵比对霞多丽幼苗矿质营养元素吸收利用的影响

为了研究不同氮源对葡萄矿质元素吸收利用的影响,以沙培霞多丽幼苗为试材,设置了硝态氮和铵态氮5种处理比例(100:0,70:30,50:50,30:70,0:100).结果表明,不同硝铵比对不同元素根系吸收和地上部利用的影响不同,较高比例的铵态氮有利于根系中P、K,Ca、Mg、Fe、Mn、Zn等元素的吸收,却抑制了地上部K、Ca、Mg、Fe的积累和利用;硝铵比30:70有利于地上部P元素的积累,而70:30有利于K的积累;叶片中的Ca在全硝时含量最高,但Mg则在含有硝态氮的所有处理中变化不大;对于叶片中的微量元素,Mn、Zn含量在混合氮源(70:30,50:50,30:70)条件下均保持较高水平;而叶片中的Fe以硝态氮较高比例时含量较高;Cu的含量无论根系还是叶片受硝铵比的影响较小.综合认为,单纯的硝态氮或铵态氮不利于葡萄矿质元素的吸收和运输利用.     

Product study of the OH, NO3, and O3 initiated atmospheric photooxidation of propyl vinyl ether

A product study is reported on the gas-phase reactions of OH and NO3 radicals and ozone with propyl vinyl ether (PVE). The experiments were performed in a 405 L borosilicate glass chamber in synthetic air at 298 +/- 3 K using long path in situ FTIR spectroscopy for the analysis of the reactants and products. In the presence of NO(x) (NO + NO2) the main products for the OH-radical initiated oxidation of PVE were propylformate and formaldehyde with molar formation yields of 78.6 +/- 8.8% and 75.9 +/- 8.4%, respectively. In the absence of NO(x) propylformate and formaldehyde were formed with molar formation yields of 63.0 +/- 9.0% and 61.3 +/- 6.3%, respectively. In the reaction of NO3 radicals with PVE propylformate 52.7 +/- 5.9% and formaldehyde 55.0 +/- 6.3% were again observed as major products. The ozonolysis of PVE led to the production of propylformate, formaldehyde, hydroxyperoxymethyl formate (HPMF; HC(O)OCH2OOH), and CO with molar formation yields of 89.0 +/- 11.4%, 12.9 +/- 4.0%, 13.0 +/- 3.4%, and 10.9 +/- 2.6%, respectively. The formation yield of OH radicals in the ozonolysis of PVE was estimated to be 17 +/- 9%. Simple atmospheric degradation mechanisms are postulated to explain the formation of the observed products.     

制革废水氨氮达标和脱氮处理技术分析

从制革废水脱氮机理入手,分析了现有制革废水处理工程难以实现氨氮达标和脱氮的原因,提出了现有制革废水处理工程改造技术和新设计工程技术要点,并列举了制革废水A/O脱氮工艺设计计算方法及运行控制技术要点.     

间接电化学还原染色媒介体系对比研究

以玻碳电极为工作电极,比较了Fe(Ⅲ)-草酸-葡萄糖酸钙与Fe(Ⅲ)-TEA-葡萄糖酸钙媒介体系的循环伏安曲线,探讨了体系的氧化还原性.Fe(Ⅲ)-草酸在碱性条件下不能稳定存在,但在加入葡萄糖酸钙(DGL)后,Fe(Ⅲ)-草酸在pH≥13的强碱性条件下依然能稳定存在,2种体系都表现出受扩散控制的准可逆反应过程.当n(草酸)∶n(Fe3+)∶n(DGL)=2∶1∶1时,电解30 min氧化还原电位能达到-1 019.2 mV.2种体系的染色效果(K/S及CIELab)都与传统保险粉染色效果相当.     

小白菜硝酸盐含量与NO3－/NH4+及氮代谢关键酶的相关性

采用液体培养实验研究了不同NO3－与NH4＋浓度比（分别为50∶50、75∶25和100∶0）对10 个品种小白菜（Brassica chinensis L.）的硝酸盐含量、光合系统参数及氮代谢关键酶活性的影响。结果表明,随着硝铵比的增加,小白菜总干质量逐渐增加（除品种天津小白菜和大头清江白菜的总干质量随硝铵比的增加先降低后升高,品种香港春秀甜白菜（236）和正旺达88的总干质量先升高后降低外）,与c（NO3－）∶c（NH4＋）为50∶50比较,增幅分别为12.66%～76.88%（c（NO3－）∶c（NH4＋）为75∶25）和17.98%～95.07%（c（NO3－）∶c（NH4＋）为100∶0）;小白菜叶和根中的硝酸盐含量增加,而叶柄硝酸盐含量则表现出先增加后下降的趋势,小白菜硝酸盐的含量叶柄（3 882.62～5 448.81 mg/kg）＞叶（2 004.86～4 146.50 mg/kg）＞根（505.39～2 188.68 mg/kg）。小白菜叶片中硝酸盐含量与硝酸还原酶活性成显著负相关,而与亚硝酸还原酶和谷氨酰胺合成酶活性成显著正相关。小白菜叶片中硝酸盐的含量随着净光合速率（Pn）和胞间二氧化碳浓度（Ci）的增加而下降,随蒸腾速率（Tr）的增强而增加。     

还原法与金属盐法结合溶解废旧羊毛的对比研究

针对还原法与金属盐法结合溶解废旧羊毛工艺进行对比性研究,通过不同还原剂、金属盐、表面活性剂的对比试验确定最佳溶剂体系,以羊毛溶解率和大分子量角蛋白回收率为考察对象.结果表明:还原剂NaHSO3/金属盐LiBr/表面活性剂SDS为最佳溶剂体系,羊毛溶解率达94％,角蛋白回收率达50％以上,红外光谱显示角蛋白以α-螺旋构象为主.     

^#3机助留问题分析与对策

介绍了凯丽特种纸公司针对#3纸机字典纸生产留着低问题采取的措施、随后出现的新问题处理以及取得的效果。     

NH3 formation and destruction during the gasification of coal in oxygen and steam

This study was conducted to investigate the formation and destruction of NH3 during the gasification of coal in atmospheres containing O2 and steam. A Victorian brown coal was gasified in a novel bench-scale fluidized-bed/ fixed-bed reactor at 800 degrees C in atmospheres containing 2000 ppm O2, 15% H2O, or 2000 ppm O2 + 15% H2O. A NH3 standard gas was also used to study the destruction of NH3 in the gas phase and through gas-solid interactions. Sand, char, and coal ash were all found to enhance the destruction of NH3. An atmosphere containing O2 alone does not favor the conversion of char-N into NH3 but favors the destruction of NH3 through various mechanisms. The introduction of H2O into the gasification system greatly favors the conversion of char-N into NH3 and inhibits the destruction of NH3. The formation and destruction of NH3 in an atmosphere containing 15% H20 was similar to that in an atmosphere containing 15% H20 and 2000 ppm 02, indicating the dominant effects of steam in the formation and destruction of NH3 in a gasifier.