Ag／TiO2光催化氧化还原反应脱除水体中无机氮

采用光催化还原法制备了高活性的载银二氧化钛光催化剂，并用XRF、TEM、XRD及XPS、UV-Vis方法对催化剂进行了表征．考察了负载舨的含量、催化剂制备时间、搅拌气体的种类以及Fe^2＋的添加等条件对该催化剂光催化水体脱氮活性的影响．结果表明：载银量1．0％时去除效果最佳；制备催化剂时光照时间不充分会使催化剂失去还原效力；氮气保护下催化剂反应活性更高；Fe^2＋的加入利于光催化反应；2h光催化含氨氮和亚硝基氮的水样。总脱氮率达到了63．9％．     

烟气脱氮技术现状及展望

氮氧化物是大气主要污染物之一。近年来,烟气脱氮技术的研究一直是环保领域的新技术前沿研究热点之一。由燃煤而产生的大量低浓度NOx烟气是导致大气污染、酸雨和光化学烟雾危害严重的主要原因。研究烟气脱氮具有十分重要的意义。目前主要的烟气脱氮技术有选择性催化还原法、非催化选择性还原法、等离子体活化法、生物法以及微波法等。     

先进再燃脱硝机理与添加剂增效机理

先进再燃是将再燃和喷入氨剂相结合的脱硝技术.添加剂可以改善先进再燃脱硝反应,进一步提高脱硝效率.主要阐述了先进再燃脱硝技术的进展和脱硝机理,综述了先进再燃脱硝添加剂及其增效机理.添加剂可对同相和异相还原反应起促进作用,可同时利用一种或几种添加剂以改善再燃和氨剂还原NOx的反应,其中碱金属化合物是先进再燃的良好添加剂.有必要筛选制备合适高效的添加剂,进一步研究添加剂对再燃、氨剂还原NOx的增效机理及其协同反应条件.     

小氮肥生产中节能技术改造的应用研究

经过多年发展,我国氮肥工业的生产工艺技术装备、生产能力已经位居世界首位。但受制于能源构成,我国氮肥工业多以煤焦作为主要原料,从而导致严重的水、气污染,因此我国氮肥工业属于重污染行业。在国家大力倡导节能减排,绿色发展的今天,氮肥工业探索节能减排之路势在必行。就小氮肥生产中节能技术改造的应用,展开了研究分析,以供参考。     

海绵铁还原微污染源水中硝酸盐氮的影响因素研究

饮用水源的硝酸盐氮污染是目前急需解决的重要环境问题。以人工配水为研究对象,通过静态试验研究了各因素对海绵铁去除水中NO_3~--N效果的影响。结果表明:酸洗预处理可有效提高海绵铁对NO_3~--N的去除;pH越低,NO_3~--N去除率越高;原水中NO_3~--N初始浓度越高,被还原NO_3~--N的量越多。产物分析表明:海绵铁还原NO_3~--N是产碱耗酸的反应,主要产物是氨氮,占NO_3~--N还原量的68%~83%。     

Reduction of nitrogen dioxide by propene over acidic mordenites: influence of acid site concentration, formation of by-products and mechanism

The reduction of nitrogen dioxide to nitrogen by propene was studied over a variety of acidic mordenite zeolites differing in their Si : Al ratio and thus, in their concentration of acid sites. The formation of by-products was monitored applying an ion–molecule reaction (IMR) mass spectrometer. It was found that at fixed conditions the yield of nitrogen increases with increasing concentration of acid sites, confirming that acid sites are the active catalytic centres in the reaction. Apart from nitrogen and nitric oxide, acrylonitrile and ammonia are formed as nitrogen containing gas-phase products in the reaction. In separate experiments, it was shown that acrylonitrile is hydrolysed by water over the acidic zeolites to yield ammonia and acrylic acid. When acrylonitrile is used as reducing agent for nitrogen dioxide, formation of nitrogen is strongly enhanced in the presence of water. Water also has a promoting effect on the formation of nitrogen in the reaction between nitrogen dioxide and propene. Acrylonitrile and its product of hydrolysis, ammonia, are considered to be intermediates of nitrogen dioxide reduction to nitrogen by propene over acidic zeolites.     

Selektive Reduktion von Stickoxiden in Rauchgasen – Stand der Technik und neue Wege

Selective reduction of nitrogen oxides in flue gas–state of the art and trends . The selective reduction of nitrogen oxides by ammonia may be catalyzed by different substances. The suitable choice of the catalyst is determined largely by where the reduction step is placed in the overall process. The technical problems and the required catalyst properties are demonstrated and discussed. A new process, based on a periodically operated reactor, avoids some of the difficulties otherwise encountered.     

烧结烟气中NO x 和二英的减排现状及发展趋势

烧结工序是钢铁工业生产链的重要环节,同时也是大气中二氧化硫（SO₂）、氮氧化物（NO _x ）和二英的主要排放源。随着烧结烟气脱硫技术日趋成熟,氮氧化物和二英的减排成为烟气污染物减排的重中之重。本文介绍了钢铁工业烧结烟气超低排放的新法规和相关标准,并从源头控制、过程减排和末端治理三个方面综述了国内外关于烧结烟气中NO _x 和二英减排的最新研究进展及相关技术工业应用现状,提出了采用全流程多技术耦合方式是实现烧结烟气多污染物低成本减排的发展方向。结合钢铁工业“碳减排”新发展要求,指出烧结烟气低温脱硝/二英催化剂的研究挑战,并对其抗水、抗硫性能提升研究进行了展望。     

TiO_2光催化还原去除饮用水中硝酸盐的实验研究

在间歇式反应器中,以TiO2为催化剂,进行了光催化还原去除饮用水中硝酸盐的实验,考察了空穴清除剂种类、甲酸用量、催化剂用量和硝酸盐浓度对去除硝酸盐效率的影响。结果表明,在TiO2作用下,硝酸盐能被有效地还原去除,去除率可达35.16%;与甲醇、甲酸钠和EDTA相比,甲酸作空穴清除剂时硝酸盐去除效果最佳;甲酸和硝酸盐的浓度对光催化反应的影响显著,催化剂最佳用量为100 mg。探讨了反应机理,认为光催化还原硝酸盐是一分步反应。     

光（电）催化氮气还原合成氨研究进展

光（电）催化氮气还原技术利用天然太阳能作为能源,具有成本低、反应条件温和等众多优势,可解决传统工业合成氨Haber-Bosch工艺的高能耗以及高CO₂排放等问题,被认为是目前最具前景的新兴合成氨技术之一。由于氮气为非极性分子,在水中溶解度极低,且本身呈现化学惰性,难以被活化,使得整体的氮气还原转化合成氨效率较低。同时,光生载流子的利用率也显著影响整体的催化效率。为此,光（电）催化氮气还原技术的关键在于催化剂的设计和催化反应体系的优化。本文在介绍光（电）催化氮气还原合成氨反应过程以及机理的基础上,主要从促进氮气溶解扩散、氮气吸附和活化以及强化载流子分离和传输等具体反应过程出发,重点综述近期国内外在光（电）催化氮气还原合成氨领域基于上述反应过程强化的最新研究现状。最后,指出了目前光（电）催化氮气还原合成氨研究领域面临的挑战,并对此领域的未来发展趋势进行了分析与展望。     

浮法生产线空分设备增产降耗改造

通过对现有空分设备进行改造,提高氮气产量,并对相关管道进行联网,用二线一套制氮机组供应浮法一线锡槽用氮气,用二线另一套制氮机组再加上原一线一套制氮机组供应二线锡槽用氮气,与改造前相比少开启一套制氮机组.以达到节约氮站电耗和备件消耗,同时提高二线氮气提取率的目的.     

利用全自动定氮仪测定硝化棉的含氮量

采用自行研制的全自动定氮仪测定硝化棉的含氮量,研究了样品前处理条件、全自动定氮仪实验参数对检测结果的影响;讨论了实验的准确性与重复性,对全自动定氮仪法与传统合金还原法进行了比较。结果表明,样品前处理采用石墨炉加热,梯度升温的皂化模式;最佳实验参数为:蒸汽体积分数80%、预热30s、还原反应7min、硼酸体积35mL、蒸馏时间8min;与传统合金还原法相比,采用全自动定氮仪检测硝化棉含氮量的方法用时少、操作简单,自动化程度高,减少了人为误差的影响,可保证结果的精度和准确性。     

Oxygen reduction activity of pyrolyzed polypyrroles studied by 15N solid-state NMR and XPS with principal component analysis

New analytical method for characterizing the nitrogen sites in N-doped carbon catalysts is proposed by employing ¹⁵N solid-state NMR. ¹⁵N labeled polypyrrole is prepared as a precursor of N-doped carbon catalysts and is pyrolyzed at several different temperatures in a nitrogen atmosphere. The oxygen reduction reaction is evaluated by rotating disk electrode experiments, and solid-state ¹⁵N NMR and XPS spectra are measured. The relationship between oxygen reduction activity and the chemical structure, combined with principal component analysis is discussed. The iron-free pyrolyzed polypyrrole samples display quite poor catalytic activity for oxygen reduction, whilst the iron-containing pyrolyzed polypyrrole samples display better oxygen reduction activity. ¹⁵N solid-state NMR spectra show that the pyrolyzed polypyrroles contain pyridinic, quaternary, pyrrolic nitrogens at edges or at defects in graphitic sheets. This is the first observation of quaternary nitrogens at edges or defects in graphitic sheets using ¹⁵N solid-state NMR. Using principal component analysis of the XPS and ¹⁵N solid-state NMR spectra, it is found that most pyridinic, quaternary, and pyrrolic nitrogen atoms are not related to oxygen reduction reaction. However, the samples which contain a larger proportion of some particular type of pyridinic nitrogen atoms show a higher activity for the oxygen reduction reaction.     

氮掺杂科琴黑碳材料的制备及 电催化氧还原性能研究

氮掺杂碳材料是一种有应用前景的电催化氧还原催化剂。以尿素和三聚氰胺作为氮源,在氮气气氛下高温焙烧,制得两种氮掺杂科琴黑碳材料并将其用于电催化氧还原反应。使用X射线衍射仪（XRD）、X射线光电子能谱仪（XPS）、场发射扫描电子显微镜（FESEM）、比表面物理吸附分析仪等对氮掺杂前后的科琴黑的结构和形貌进行了分析。结果表明：氮掺杂之后科琴黑仍保持石墨结构,其形貌和比表面积均无明显改变。在XPS谱图上,氮掺杂后科琴黑上存在氮元素,其中以三聚氰胺为氮源比以尿素为氮源更容易得到吡啶氮。通过循环伏安法和线性扫描伏安法研究了3个样品的电催化氧还原性能。结果表明：氮掺杂能明显提高科琴黑的电催化氧还原性能,未掺杂的 科琴黑（AC）的半波电位为0.746 V,而以尿素和三聚氰胺为氮源掺杂后的科琴黑碳材料的半波电位分别提高到了 0.756 V（尿素-N/AC）和0.786 V（三聚氰胺-N/AC）。     

Aluminothermic combustion of chromium oxide based systems under high nitrogen pressure

The aluminothermic reduction of some oxide systems in the solid-state combustion mode in nitrogen in a high-pressure reactor has been studied for the purpose of obtaining nitridecontaining composites. The properties of the synthesis products obtained at various nitrogen pressures were determined.     

The influence of nitrate reduction strategies on the temporal development of the nitrate pollution of soil and groundwater throughout Germany - a regionally differentiated case study

A GIS-based area-differentiating model has been used to analyze the nitrate pollution of soil and groundwater throughout Germany. The results of the calculations based on the model for the current situation show that a high potential for high nitrate pollution of the soil and groundwater (> 50 mg NO₃/l) is to be expected in all regions of Germany subject to intensive agricultural use. In order to achieve a sustainable use of water resources, effective strategies to reduce the nitrogen surpluses from agriculture must be developed and analyzed with respect to their spatial and temporal impact on the nitrate pollution of soil and groundwater, taking into consideration the various agricultural land usages as well as the different hydrological, hydrogeological and agricultural conditions.The effects of three different nitrate reduction strategies on the resulting N-surpluses and the nitrate concentration in the leachate were investigated: firstly, a stocking rate limitation, secondly, a limitation of both organic and mineral fertilizers and thirdly, a combination of three reduction measures consisting of a stocking rate limitation, an improvement of the nitrogen utilization factor by livestock and a higher utilization factor of nitrogen bound in organic fertilizers by crops. The analysis showed that separate application of each of these nitrogen reduction measures would only lower the nitrogen surpluses in a few regions. In order to achieve a considerable reduction of nitrate concentrations both in leachate from land under agricultural use and in the groundwater a combination of area-covering and regionally effective measures (scenario III) turned out to be most promising.     

燃煤蒸汽锅炉联合脱硝技术改造探讨

对燃煤蒸汽锅炉烟气脱硫脱硝采用低氮燃烧技术(ROFA)结合选择性非催化还原(Rotamix)和选择性催化还原(SNCR+SCR)的联合脱硝工艺进行改造,使烟气排放达到氮氧化物含量不超过100 mg/m3。     

Entfernung von Stickstoffoxiden aus Sauerstoff enthaltenden Automobil‐Abgasen

The most important systems for downstream reduction of NO_x under lean conditions of exhaust gases are discussed. The systems operate either continuously under direct chemical reduction of NO_x to nitrogen, or discontinuously with prior adsorption. The selective catalytic reduction (SCR) of nitrogen oxides using ammonia (processed in an NH₃ generator) or ammonia‐forming substances (urea as solution or solid) as reducing agents is almost at the application stage in trucks, while hydrocarbons as reducing agents (so‐called HC‐SCR) are not sufficiently selective for NO_x reduction because the hydrocarbons are themselves predominantly oxidized. The principle of NO_x storage as nitrates followed by regeneration and reduction to nitrogen requires no separate or external reducing agents and claims therefore to meet future emission standards as long as problematic sulfur incorporation is avoided. The common characteristics of all these NO_x abatement systems is that they are all based on the principle »oxidation before reduction« and involve the key molecule NO₂.     

基于铁基载氧体的煤化学链气化还原过程中氮元素迁移行为

采用热重-质谱-红外联用技术（TG-MS-FTIR），Ar气氛下对煤进行化学链气化实验，实时分析还原过程热解阶段和水蒸气气化反应阶段的过程中固体质量变化和生成气体成分。使用X射线光电子能谱对固相产物进行表面元素分析，探究化学链气化还原过程不同阶段固相产物中氮赋存形态的变化。研究结果表明：载氧体对化学链气化还原过程不同阶段含氮气体释放均有影响。热解阶段载氧体促进自由基的生成，加速了一次热解阶段含氮气体的释放，高温下，载氧体促使NH₃转化为HCN；气化阶段载氧体的加入使半焦的石墨化程度降低，含氮气体释放速率增加。对固相产物中氮的赋存形态而言，载氧体会抑制热解阶段吡咯型氮的分解与转化，高温下，半焦的石墨化和有序化程度降低的同时，镶嵌在煤大分子里面的质子化吡啶裸露出来，质子化吡啶含量降低，吡啶型氮和吡咯型氮的含量大大提升。     

掺杂炭黑电催化剂氧还原性能研究

碳纳米材料由于其良好的结构和功能特性,常做为氧还原反应中电催化剂的载体或直接做为氧还原反应的电催化剂。本文从具有良好导电性和高比表面积的炭黑(BP2000)出发,在对其进行表面氧化的基础上分别通过高温氨化和Fe(NO3)3溶液浸渍/高温煅烧进行了掺氮(N-BP2000)和掺铁(Fe-BP2000),对比考察了掺氮和掺铁对所得催化剂氧还原性能的影响。结果表明,所制备的掺氮炭黑(N-BP2000)和掺铁炭黑(Fe-BP2000)电催化剂的氧还原活性均较BP2000电催化剂提高显著。其中,Fe-BP2000电催化剂,表现出了最佳的氧还原活性,其半波电位为0.774 V,分别比N-BP2000与BP2000电催化剂正22、108 mV,同时其也表现出最佳的长程稳定性。