循环流化床燃煤过程NO、N2O和SO2的排放行为研究

在30kW循环流化床装置上进行了中国西部三种煤的燃烧实验，考查了燃烧温度、空气分级、空气过剩系数、固体颗粒循环料率和煤种等因素对NO、N2O、SO2污染物排放的影响。结果表明，强化空气分级可显著降低高挥发分煤种NO的生成量，但对N2O影响不大；增加空气过剩系数同时增加了NO与N2O的排放；增加固体循环料率显著降低NO生成量，但N2O排放略有增加；高阶煤燃烧生成较多N2O，低阶煤生成较多NO。燃烧温度1120K、过剩空气系数1.25下约85%燃料中N转化为N。实验范围内改变操作参数不影响SO2与CO排放量。     

氮肥管理对夏玉米土壤CH4和N2O排放的影响

通过设置四个不同的氮肥管理措施, 即氮肥施用量300 kg N/ha (N300)和250 kg N/ha (N250)、改进的施肥模式(Optimized)以及施用缓释肥(SRU), 研究华北平原夏玉米生长季土壤与大气之间CH₄和N₂O的交换通量及相应措施的减排潜力. 结果表明, 在2008年整个夏玉米生长季, 土壤都是大气CH₄的净吸收库和N₂O的排放源. 夏玉米生长季土壤氧化吸收的CH₄总量从大到小依次为Optimized > N250 > SRU > N300, 对应的吸收总量依次为624.16、590.07、487.89以及316.02 g CH₄-C/ha, 各处理间氧化吸收的CH₄总量无显著差异. 与N300和N250这两个处理相比, 依据夏玉米对氮肥的需肥规律以及玉米根层土壤速效氮的供给能力而确定氮肥施用量, 同时再平衡施用磷肥和钾肥的改进施肥模式能够显著降低夏玉米生长季N₂O的排放. 施用聚乙烯包膜的尿素也能够显著降低夏玉米季N₂O的排放. 夏玉米生长季土壤排放的N₂O总量从大到小依次为N300 > N250 > Optimized > SRU, 对应的排放总量依次为3462.18、2340.07、1680.00以及911.91 g N2O-N/ha, 相应的N₂O排放系数分别为1.15%、0.94%、0.91%以及0.30%.     

对流层夜间化学研究

NO3自由基与N2O5是对流层夜间化学的关键物种.一方面NO3与O3等组分是夜间大气中的重要氧化剂,与它们的反应是生物排放挥发性有机物(VOCs)的主要汇;另一方面NO3与N2O5和雨滴或气溶胶颗粒物发生的异相反应则是大气中氮氧化合物NOx(NO,NO2)的主要清除过程,从而可以减轻对流层臭氧污染.研究它们的化学反应性质及对其进行实地测量,对深入理解大气氧化过程和全面了解区域乃至全球大气自净能力有重要意义.本文总结了近年来有关夜间化学的研究成果,介绍了以NO3和N2O5为中心的基本夜间化学过程、对流层中NO3与N2O5的源与汇以及外场测量技术的最新研究进展,并提出了尚待解决的一些问题.     

冬季平原河网水体溶存甲烷和氧化亚氮浓度特征及排放通量

以长江三角洲上海地区和海河流域天津地区水网为研究对象,对冬季河网表层水体溶存甲烷（CH4）和氧化亚氮（N2O）浓度、饱和度及水-气界面排放通量进行了研究.结果表明,冬季我国平原河网水体溶存CH4和N2O的浓度值都很高,呈高度过饱和状态：CH4浓度均值为0.86mol/L（饱和度：758%）,范围在（0.043±0.001）～（25.3±9.32）μmol/L之间;N2O浓度均值为86.8nmol/L（饱和度：488%）,范围在（9.71±0.41）～（691±35.2）nmol/L之间变化.天津排污河水体CH4和N2O浓度显著高于其他河流（均值分别为38.4mol/L和88.9nmol/L）.水体溶存CH4和N2O浓度、饱和度存在很大的地区差异,上海河网的CH4和N2O浓度和饱和度均值高于天津河网.河网水体水-气界面CH4和N2O排放通量变化范围很广,CH4通量在（1.35±0.22）～（665±246）mol/m2h之间,平均值为24.1mol/m2h,N2O通量在（0.19±0.02）～（22.6±5.05）mol/m2h之间,平均值为2.28mol/m2h.相关分析发现,河网水体溶存CH4浓度与DO显著负相关,与NH4＋显著正相关;N2O浓度则与NH4＋和NO3＋NO2显著正相关.河网水-气界面CH4和N2O排放通量均呈现出市区高郊区和农村低的空间分布规律,污染严重的河流已显然成为大气CH4和N2O的潜在排放源.     

长江三角洲平原河网水体溶存CH4和N2O浓度及其排放通量

以上海市黄浦江上游和崇明岛河网为代表,对长江三角洲平原河网夏季表层水体溶存甲烷（CH4）和氧化亚氮（N2O）浓度、饱和度及其水-气界面排放通量进行了研究.结果表明,河网水体溶存CH4浓度在（0.30±0.03）～（6.66±0.14）μmol·L^-1之间,N2O浓度在（13.8±2.33）～（435±116）nmol·L^-1之间,CH4和N2O溶存浓度处于高度过饱和状态（饱和度分别为（468±49.0）%～（11560±235）%和（175±29.5）%～（4914±1304）%）.水体中溶解氧（DO）含量是控制溶存CH4浓度的主要因素,而水体溶存N2O的浓度同硝酸根（NO3-）、亚硝酸根（NO2-）、化学需氧量（CODcr）浓度呈显著正相关,同盐度和pH呈显著负相关关系.河道水体中溶存CH4和N2O主要产生于河底沉积物中的甲烷化过程和反硝化过程,并扩散到水体中,进而排放到大气.夏季7月上海市河网水体-大气界面CH4和N2O排放通量达到（778±59.8）和（236±63.6）μmol·m^-2·h^-1,平原地区河网的富营养化使其成为大气CH4和N2O的一个重要潜在排放源.     

长江三角洲平原河网水体溶存CH_4和N_2O浓度及其排放通量

以上海市黄浦江上游和崇明岛河网为代表,对长江三角洲平原河网夏季表层水体溶存甲烷(CH4)和氧化亚氮(N2O)浓度、饱和度及其水-气界面排放通量进行了研究.结果表明,河网水体溶存CH4浓度在(0.30±0.03)～(6.66±0.14)μmol·L-1之间,N2O浓度在(13.8±2.33)～(435±116)nmol·L-1之间,CH4和N2O溶存浓度处于高度过饱和状态(饱和度分别为(468±49.0)%～(11560±235)%和(175±29.5)%～(4914±1304)%).水体中溶解氧(DO)含量是控制溶存CH4浓度的主要因素,而水体溶存N2O的浓度同硝酸根(NO3-)、亚硝酸根(NO2-)、化学需氧量(CODcr)浓度呈显著正相关,同盐度和pH呈显著负相关关系.河道水体中溶存CH4和N2O主要产生于河底沉积物中的甲烷化过程和反硝化过程,并扩散到水体中,进而排放到大气.夏季7月上海市河网水体-大气界面CH4和N2O排放通量达到(778±59.8)和(236±63.6)μmol·m-2·h-1,平原地区河网的富营养化使其成为大气CH4和N2O的一个重要潜在排放源.     

新型磷酸硅铝分子筛SAPO-56的合成与表征

以 N ,N ,N′,N′-四甲基 -1 ,6-己二胺 ( TMHD)为模板剂 ,采用水热法在 Al2 O3 -P2 O5-Si O2 体系中合成了 SAPO-56分子筛 .固定模板剂和水 ,得到 Al-Si-P三元体系相图 .当原料物质的量比为 0 .5相似文献   

对流层夜间化学研究

NO3自由基与N2O5是对流层夜间化学的关键物种。一方面NO3与O3等组分是夜间大气中的重要氧化剂,与它们的反应是生物排放挥发性有机物(VOCs)的主要汇;另一方面NO3与N2O5和雨滴或气溶胶颗粒物发生的异相反应则是大气中氮氧化合物NOx(NO,NO2)的主要清除过程,从而可以减轻对流层臭氧污染。研究它们的化学反应性质及对其进行实地测量,对深入理解大气氧化过程和全面了解区域乃至全球大气自净能力有重要意义。本文总结了近年来有关夜间化学的研究成果,介绍了以NO3和N2O5为中心的基本夜间化学过程、对流层中NO3与N2O5的源与汇以及外场测量技术的最新研究进展,并提出了尚待解决的一些问题。     

生物质气再燃减少流化床N_2O排放的实验研究

以生物质气化气作为再燃燃料,在小型流化床反应器内进行了N2O脱除的实验研究。研究了生物质气化气投入位置、料层高度、再燃燃料比、烟气含氧量和反应温度对N2O排放的影响。结果表明,距布风板200 mm的B喷口较离布风板较近的A喷口(距布风板100 mm)对应的N2O转化率高;反应温度为850℃、按照N2O/N2配置模拟烟气的情况下,B口喷入生物质气量为1%,床料CaO高度为10 mm时N2O接近完全分解;反应温度为850℃,床层高度大于20 mm时,从B口喷入大于0.4%比例的生物质气对应N2O分解率高于95%。     

多胺钴氧合配合物的室温固相合成、表征及性质

用室温固相法分别合成了以二乙三胺、三乙四胺为配体、以钴为中心离子的配合物.室温下，每摩尔配合物消耗2 mol O2，其中1 mol O2用来和钴离子配位形成超氧配合物，另外消耗的1 mol O2则是由于配体被活化氧氧化所致.采用混合溶剂法分离出两种固态氧合配合物[Co(NH2CH2CH2N=CHCH2NH2)2O2](Ac)2•2H2O和[Co(NH2CH2CH2N=CHCH2NHCH2CH2NH2)2O2](Ac)2•2H2O.通过元素分析、红外光谱、电导、XRD、NMR、热分析等测试手段研究了该配合物的性质，确定了该配合物的组成，初步探讨了相关机理.     

钾促进的Co-Mn-Al混合氧化物催化剂上模拟废气中N2O的分解减排

Intrinsic data of N2O catalytic decomposition over a K-promoted Co-Mn-Al mixed oxide prepared by the thermal treatment of a layered double hydroxide was used for the design of a pilot reactor for the abatement of N2O emissions from the off-gases in HNO3 production.A pseudo-homogeneous one-dimensional model of an ideal plug flow reactor under an isothermal regime(450°C)was used for reactor design.A catalyst particle diameter of 3 mm is a compromise size because increasing the size of the catalyst particle leads to a decrease in the reaction rate because of an internal diffusion limitation,and particles with a smaller diameter cause a large pressure drop.A catalyst bed of 11.5 m 3 was estimated for the target N2O conversion of 90%upon the treatment of 30000 m 3 /h of exhaust gas(0.1 mol%N2O,0.005 mol% NO,0.9 mol%H2O,5 mol%O2)at 450°C and 130 kPa.     

Zn取代类水滑石衍生复合氧化物上N2O的催化分解

恒定二价与三价阳离子比为3((nZn+nMg)/nAl=3), 采用共沉淀法制备不同Zn含量的系列类水滑石前驱物ZnxMg3-xAl-HT (x=0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0), 经焙烧得到其衍生复合氧化物催化剂ZnxMg3-xAlO, 用于N2O的直接催化分解. 采用X射线衍射(XRD)、比表面积分析(Brunauer-Emmett-Teller)、热分析(TG-DSC)和傅里叶变换红外(FT-IR)光谱等表征手段考察了Zn含量对材料前驱物及其衍生复合氧化物组成和结构的影响, 研究了系列ZnxMg3-xAlO催化剂的N2O催化分解性能, 同时探讨了反应条件, 如N2O浓度、空速、O2和H2O等因素对催化剂活性的影响. 结果表明, 所有前驱物材料均能形成完整的层状水滑石结构; 经高温焙烧后形成了以Zn-Al尖晶石为主相的复合氧化物, 且Zn掺杂有助于促进尖晶石相的生成; Zn含量对材料的热稳定性、比表面积和N2O催化分解活性有显著的影响; 随着Zn含量增加, 催化剂比表面积下降, 但其不是影响催化剂活性的主要因素; 650 ℃焙烧后的Zn2.0Mg1.0AlO催化剂具有较好的N2O催化分解活性; N2O浓度、空速及O2对催化剂活性的影响较小, 而H2O则对活性有较大的影响.     

Molecular beam measurements and Monte Carlo simulations of the kinetics of N2O decomposition on Rh(111) single-crystal surfaces

The kinetics of N2O decomposition on Rh(111) single-crystal surfaces were investigated both experimentally by isothermal molecular beam measurements and theoretically using a Monte Carlo algorithm. The present work was directed to the understanding of two unusual observations derived from our previous work on this system, namely, (1) the lower rates for N2O decomposition seen at higher reaction temperatures, and (2) the lower total nitrogen yields and final oxygen surface coverages that accompany that behavior. Experimentally, it was determined here that after the rhodium surface is rendered inactive by N2O decomposition at high (520 K) temperatures, significant activity is still possible at lower (350 K) temperatures. The Monte Carlo simulations explain these observations by assuming that the surface sites required for the activation of adsorbed N2O increase in size with increasing reaction temperature.     

N_2O在Cu_xFe_(1-x)Fe_2O_4和Ni_xFe_(1-x)Fe_2O_4复合氧化物催化剂上的分解反应

用共沉淀法制备了一组具有尖晶石结构的Cu-Fe和Ni-Fe复合氧化物,用于有氧条件下催化分解N2O,考察了催化剂组成对催化活性的影响.用N2物理吸附(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等技术对催化剂进行了结构表征.结果表明:在不同组成的Cu-Fe、Ni-Fe系列复合氧化物催化剂中,Cu Fe2O4和Ni Fe2O4对于N2O分解反应的初活性较高,这是因为Cu Fe2O4和Ni Fe2O4的比表面积较高、晶粒较小,而且其表面氧物种与金属(Cu2+、Fe3+)的化学作用较弱,氧物种易脱除、脱氧量较高.相比较而言,Ni Fe2O4催化剂上的N2O分解活化能低于Cu Fe2O4,Ni Fe2O4的初活性优于Cu Fe2O4.500℃连续反应100 h,Cu Fe2O4上的N2O转化率降至84.9%,而Ni Fe2O4上的N2O转化率一直保持99%,Ni Fe2O4有较高的催化稳定性.     

Thermal decomposition of energetic materials. 5. reaction processes of 1,3,5-trinitrohexahydro-s-triazine below its melting point

Through the use of simultaneous thermogravimetry modulated beam mass spectrometry, optical microscopy, hot-stage time-lapsed microscopy, and scanning electron microscopy measurements, the physical and chemical processes that control the thermal decomposition of 1,3,5-trinitrohexahydro-s-triazine (RDX) below its melting point (160-189 degrees C) have been identified. Two gas-phase reactions of RDX are predominant during the early stages of an experiment. One involves the loss of HONO and HNO and leads to the formation of H2O, NO, NO2, and oxy-s-triazine (OST) or s-triazine. The other involves the reaction of NO with RDX to form NO2 and 1-nitroso-3,5-dinitrohexahydro-s-triazine (ONDNTA), which subsequently decomposes to form a set of products of which CH2O and N2O are the most abundant. Products from the gas-phase RDX decomposition reactions, such as ONDNTA, deposit on the surface of the RDX particles and lead to the development of a new set of reaction pathways that occur on the surface of the RDX particles. The initial surface reactions occur on surfaces of those RDX particles in the sample that can accumulate the greatest amount of products from the gas-phase reactions. Initial surface reactions are characterized by the formation of islands of reactivity on the RDX surface and lead to the development of an orange-colored nonvolatile residue (NVR) film on the surface of the RDX particles. The NVR film is most likely formed via the decomposition of ONDNTA on the surface of the RDX particles. The NVR film is a nonstoichiometric and dynamic material, which reacts directly with RDX and ONDNTA, and is composed of remnants from RDX and ONDNTA molecules that have reacted with the NVR. Reactions involving the NVR become dominant during the later stage of the decomposition process. The NVR reacts with RDX to form ONDNTA via abstraction of an oxygen atom from an NO2 group. ONDNTA may undergo rapid loss of N2 and NO2 with the remaining portion of the molecule being incorporated into the dynamic NVR. The dynamic NVR also decomposes and leads to the formation of H2O, CH2O, N2O, NH2CHO, (CH3)2NCHO, (CH3)2NNO, C2H2N2O, and (CH3)3N or CH3NCH2CH3. The competition between reaction of the dynamic NVR with RDX and its own thermal decomposition manifests itself in a rapid increase in the rate of evolution of the NVR decomposition products as the amount of RDX remaining in the sample nears depletion. The reactions between the NVR film and RDX on the surface of the RDX particles leads to a localized environment that creates a layer of molten RDX on the surface of the particles where reactions associated with the liquid-phase decomposition of RDX may occur. The combination of these reaction processes leads to an acceleration of the reaction rate in the later stage of the decomposition process and creates an apparent reaction rate behavior that has been referred to as autocatalytic in many previous studies of RDX decomposition. A reaction scheme summarizing the reaction pathways that contribute to the decomposition of RDX below its melting point is presented.     

Selective photoreduction of nitric oxide to nitrogen by nanostructured TiO2 photocatalysts: role of oxygen vacancies and iron dopant

Conventional TiO(2)-based photocatalysts oxidize NO(x) to nitrate species, which do not spontaneously desorb and therefore deactivate the catalyst. We show that the selectivity of this reaction can be changed by creating a large concentration of oxygen vacancies in TiO(2) nanoparticles through thermal reduction in a reducing atmosphere. This results in the photoreduction of nitric oxide (NO) to N(2) and O(2), species which spontaneously desorb at room temperature. The activity of the photoreduction reaction can be greatly enhanced by doping the TiO(2) nanoparticles with Fe(3+), an acceptor-type dopant that stabilizes the oxygen vacancies. Moreover, the photoinduced reduction of Fe(3+) to Fe(2+) provides a recombination pathway that almost completely suppresses the formation of NO(2) and thus enhances the selectivity of the reaction for N(2) formation. Gas chromatography confirms that N(2) and O(2) are formed in a stoichiometric ratio, and the activity for NO decomposition is found to be limited by the concentration of oxygen vacancies. A series of internally consistent reaction equations are proposed that describe all experimentally observed features of the photocatalytic process. The observed influence of oxygen vacancies on the activity and selectivity of photoinduced reactions may lead to new routes toward the design of highly selective photocatalysts.     

Nitrous oxide decomposition over Fe-ZSM-5 in the presence of nitric oxide: a comprehensive DFT study

A number of experimental studies have shown recently that ppm-level additions of nitric oxide (NO) enhance the rate of nitrous oxide (N(2)O) decomposition catalyzed by Fe-ZSM-5 at low temperatures. In the present work, the NO-assisted N(2)O decomposition over mononuclear iron sites in Fe-ZSM-5 was studied on a molecular level using density functional theory (DFT) and transition-state theory. A reaction network consisting of over 100 elementary reactions was considered. The structure and energies of potential-energy minima were determined for all stable species, as were the structures and energies of all transition states. Reactions involving changes in spin potential-energy surfaces were also taken into account. In the absence of NO and at temperatures below 690 K, most active single iron sites (Z(-)[FeO](+)) are poisoned by small concentrations of water in the gas phase; however, in the presence of NO, these poisoned sites are converted into a novel active iron center (Z(-)[FeOH](+)). These latter sites are capable of promoting the dissociation of N(2)O into a surface oxygen atom and gas-phase N(2). The surface oxygen atom is removed by reaction with NO or nitrogen dioxide (NO(2)). N(2)O dissociation is the rate-limiting step in the reaction mechanism. At higher temperatures, water desorbs from inactive iron sites and the reaction mechanism for N(2)O decomposition becomes independent of NO, reverting to the reaction mechanism previously reported by Heyden et al. [J. Phys. Chem. B 2005, 109, 1857].     

Co—MgO催化剂上NO—程序升温表面反应和NO—CH4反应

ＮＯ，程序升温表面反应（ＴＰＳＲ），ＮＯ－ＣＨ４反应，Ｃｏ－ＭｇＯ     

低温等离子体转化NO/O2/N2气氛中NO的实验研究

通过建立低温等离子体实验系统, 研究了介质阻挡放电型低温等离子体反应器作用于NO/O2/N2混合气体系时, NO, O2初始浓度对NO的转化效率的影响以及NOx, O3浓度随能量密度的变化关系. 低温等离子体作用于NO/O2/N2混合气体系时, NO同时发生氧化还原反应, 氧化反应占主导地位, 大部分NO转化为NO2; NO转化率随O2, NO初始浓度增大而降低, 能量密度在450～600 J/L时转化率较高; 产生的O3浓度随能量密度的增大呈先增后减的趋势.