Selective catalytic reduction of NOx from exhaust of lean-burn engine over Ag-Al2O3/cordierite catalyst

A highly effective Ag-Al₂O₃ catalyst was prepared using the in-situ sol-gel method, and characterized by surface area using nitrogen adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The catalyst performance was tested on a real lean-burn gasoline engine. Only unburned hydrocarbons and carbon monoxide in the exhaust were directly used as reductant (without any external reductant), the maximum NO _x conversion could only reach 40% at 450°C. When an external reductant, ethanol was added, the average NO _x conversion was greater than 60%. At exhaust gas temperature range of 350–500°C, the maximum NO _x conversion reached about 90%. CO and HC could be efficiently oxidized with Pt-Al₂O₃ oxidation catalyst placed at the end of SCR converter. However, NO _x conversion drastically decreased because of the oxidation of some intermediates to NO _x again. The possible reaction mechanism was proposed as two typical processes, nitration, and reduction in HC-SCR over Ag-Al₂O₃.     

氨氧化菌混培物在微量NO2气氛下的氨代谢特性

用普通活性污泥经120d富集,得到氨氧化菌混培物,氨氧化菌浓度提高300倍.在NO2/O2混合气氛下进行氨氧化试验,结果表明,无分子氧时,氨氧化菌能以NO2为电子受体氧化氨,并产生NO;加入氧气后,氨氧化速率明显提高,最高速率[33(mol NH4 -N/(g MLSS(h)]发生在混合气体中NO2和O2浓度分别为1.79(mol/L和9.38mmol/L时;在NO2浓度为0.89～1.79(mol/L范围内,O2能够强化基于NO2的氨氧化反应,当NO2浓度增大至6.71(mol/L时,氨氧化速率却降低.部分NO被O2氧化,使得反应器出口气体中NO2浓度高于进口.试验过程中产生约20%氮损失,这与氨氧化和厌氧氨氧化相互耦合产生气态含氮产物(N2、NO、N2O)有关.     

HNO_3催化氧化煤系硫铁矿生产聚铁工艺研究

提出一种以HNO3氧化煤系硫铁矿后产物FeSO4 、H2 SO4 以及补充的FeSO4 和H2 SO4 为原料 ,放出NO为催化剂 ,O2 为氧化剂 ,生产无机净水剂聚铁的生产方法 ,并讨论其工艺条件     

二冲程摩托车尾气净化催化剂的制备与评价

采用分步浸渍法制备了二冲程摩托车尾气净化催化剂Pt Co Cu/γ -Al2 O3。运用XRD、BTT法、气相色谱、分光光度法等手段进行结构表征及活性评价。结果表明 ,催化剂中的活性非贵金属的高分散金属态和周期性转化的氧化态是催化作用的活性中心 ,微量贵金属在催化剂中是必需的 ,并且该催化剂冷起性能好 ,对净化二冲程摩托车尾气有较显著的效果 ,能氧化绝大部分HC ,对CO也有一定的氧化作用 ,且能还原一定的NOx。     

Summer air quality over an artificial lake

In the summer of 1998, the air quality (indicators: CO, NO, NO₂, O₃) above the water surface of the Lake Balderey (Essen, Ruhr area, North Rhine-Westphalia, Germany), an artificial lake used for recreation purposes, was measured using the Fourier transform infrared spectroscopy (FTIR) and differential optical absorption spectroscopy (DOAS) remote measurement methods. The lake, with an area of 3 km² was created by damming the Ruhr and is surrounded by higher ground. In calm, bright weather conditions, this location results in a low-exchange situation (formation of temperature inversions, cold air dynamics) with a sustained impact on pollutant concentrations over the lake. The results of trace substance measurements (1/2 h mean values) were compared with values from comparison stations (suburban, high traffic and forest) located outside the area of the lake. In general, it was found that mean CO and NO concentrations over the lake were very low (0.3 ppm and 7.5 ppb, respectively). NO₂ values (15 ppb) were some 3.5 times higher than those recorded at the forest station and O₃ values, at 27 ppb, almost reached the same level as at the forest station (30 ppb). Mass flow densities as a function of wind direction, diurnal courses, differences between weekdays and weekends and comparisons with air quality standards are presented for the lake station.     

Cu/海泡石催化剂上NOx催化还原的研究

以天然海泡石为原料,经酸改性后作载体.采用浸渍法制成了用于NOx由CO还原的Cu基催化剂.在稀薄燃烧条件下,考察了它对汽车尾气中NOx的还原性能.实验结果表明,Cu/海泡石催化剂在富氧条件下具有良好的耐湿热稳定性和催化活性,当转化率达到90%时,反应温度＜400 ℃.当掺入稀土元素Ce和Sm后,由于与活性组分Cu之间的协同效应,催化剂的抗氧能力进一步提高了.     

CuO/γ-Al2O3烟气联合脱硫脱氮技术研究进展

燃烧等带来的SO2 和NOx 是酸雨的主要来源 ,开发能联合控制SO2 与NOx 污染的技术具有极大的应用前景。本文对国内外研究的干法CuO/γ Al2 O3烟气联合脱硫脱氮技术的研究历史与现状进行了详细的评述 ,并指出了该项技术在实际运行中存在的问题     

北京、上海两地2004和2005年大气污染特征对比分析

为了解北京、上海两市大气污染的变化及其影响因素之间的关系,根据2004、2005年大气质量监测数据,分析了北京、上海两地大气污染特征和两地主要大气污染物的变化规律.结果表明,2004、2005年北京市的PM10最大值是最小值的63.7倍,北京市的变化幅度较上海市的变化幅度大;2004、2005年北京市的SO2最大值是最小值的46.7倍,上海市的SO2最大值是最小值的13.1倍,上海市的SO2污染的因素变化幅度较小;两市的NO2浓度都较高,且季节变化不太明显;两市NO2浓度年平均值满足国家空气质量二级标准,但质量浓度都较高,这与两市的机动车尾气污染有关;两市SO2浓度年平均值除上海市2005年外均满足国家空气质量二级标准,上海市SO2污染严重与上海市消耗大量煤炭有关,北京市SO2污染物浓度年度变化剧烈与冬季取暖烧煤有关;两市可吸入颗粒物污染比较严重,北京市PM10浓度年平均值超过国家空气质量二级标准,上海市PM10浓度年平均值达到国家空气质量二级标准.总体上上海市的大气质量要好于北京市.两地大气主要污染物随时间的变化规律与两地的污染物来源、地理、气候等条件有关.     

Fe2+EDTA络合-铁屑还原连续脱除烟气中NO

研究了铁屑塔式反应器连续脱除烟气中NO的过程,建立了该过程的数学模型,并对其主要影响因素进行了讨论.结果表明,铁屑塔式反应器可连续稳定地脱除烟气中NO,进气NO浓度的变化对脱硝效率没有影响,脱硝效率随烟气流量的增加而下降,随脱硝溶液流量和填料层高度的增加而增加.所建模型的计算值和实测值能够很好地吻合,该模型可用于预测脱硝过程参数对脱硝效率的影响.     

嗜热膜生物反应器烟气同时脱硝脱汞研究

采用嗜热膜生物反应器(TMBR)同时处理含NO和Hg0的烟气,结果发现,该反应器可实现100 d的长期稳定运行,NO和Hg0去除效率分别可达87.9%、82.4%.适宜运行条件为:喷淋量为60 m L·min~(-1),p H为6.5~8.0,气体停留时间GRT为9.3 s,COD/TN为2~4.同时,采用16S r DNA分析了TMBR微生物群落.结果表明,在属类别上优势菌种是Ureibacillus和Pseudoxanthomonas.Pseudoxanthomonas、Hydrogenophaga、Thauera、Bacillus、Paracoccus、Comamonas、Pseudomonas、Nitrosovibrio、Ochrobactrum属于脱硝类菌属;Pseudomonas和Halomonas与Hg2+转化有关.Pseudomonas同时具有反硝化和还原汞化合物能力.