中红外痕量乙烷传感器设计与稳定性分析

根据乙烷气体分子在3.3 μm处的基频吸收特性,使用中心波长为3.337 μm室温连续带间级联激光器(ICL)和有效光程为54.6 m密集光斑多通气体吸收气室(600 mL)研制了基于波长调制光谱技术(WMS)的乙烷传感器。详细介绍了基于WMS和二次谐波(2f)探测技术的光谱吸收法气体检测原理,给出了目标乙烷气体吸收线的遴选细节。此项技术的使用减小了光功率漂移对系统的影响,使得系统最低检测下限(MDL)和稳定性能得到提升。结合原理框图,通过光学和电学两个模块分别详细介绍了乙烷传感系统设计方案,描述了自主研制的软、硬件单元和商用仪器的使用及其型号供他人参考,并给出传感器光学配置实物图。而且,为匹配激光波长调制与基于压力的吸收线宽,对气压和调制深度进行优化,研究了调制幅度对应2f信号峰值及调制幅度与调制深度的关系,最终确定最优气压和调制深度分别为100 Torr和0.074 cm-1,对应的调制信号幅度为~0.026 V。此外,基于优化后的气压和调制深度,使用136.8 nmol·mol-1 乙烷标准气体进行了系统灵敏度估算。详细介绍了ICL扫描调制信号、锁相放大及数据采集单元的参数设置,并给出示波器记录的扫描调制信号及2f信号波形图片。通过对比DAQ采集的2f信号和背景噪声信号,估算系统最低检测下限为33 nmol·mol-1。最后,使用9个不同浓度乙烷标准气体(20～400 nmol·mol-1)分别进行~5 min系统标定测试,并列出了拟合曲线和拟合相关度等信息。而且,使用浓度为48 nmol·mol-1乙烷气体样品开展连续2 h系统稳定性测试并进行Allan-Werle 方差分析。结果显示,该系统工作稳定,积分时间为4 s时,乙烷气体检测灵敏度为~0.81 nmol·mol-1。通过增加系统积分时间至63 s,系统灵敏度可被提高至~0.36 nmol·mol-1。     

取代环戊二烯锆、铪络合物光解活泼自由基的ESR研究

本文用自旋捕捉术技与ESR相结合的方法,研究取代环成二烯锆、铪络物(RC₅H₄)₂ZrCl₂(R=H,CH₃,C₃H₇,C₄H₉,C₅H₁₁,C₆H₁₁)及(RC₅H₄)₂HfCl₂(R=CH₃,C₂H₅,C₃H₇)光解的活泼自由基。结果表明,取代环成二烯锆、铪络合物与取代环戊二烯钛结合物光解机理相同,即光解初级过程是M-(RC₅H₄)(M=Ti,Zr,Hf)π键的均裂。其差别在于RCpMCl₂(M=Zr,Hf)可为PBN及ND捕获,并后者的加合物表现出氯核的分裂。     

(C_5H_(11)N_2)~+和(C_7H_(12)N_2)~(2+)的NMR研究

结合1H NMR,13C NMR谱,分别对钨、钼配合物{WO2(C10H6O2)2(C5H11N2)2[H2N(CH2)3NH2]}3(1),{(C5H11N2)2[H2N(CH2)3NH2][MoO2(C10H6O2)2]}(2),{(C7H12N2)2[MoO2(C10H8O2)2]}(3)晶体结构中小分子环进行了归属.其中,配合物1和2中(C5H11N2)+的NMR研究证实了六元环由1,3-丙二胺和乙腈化合而成,配合物3中(C7H12N2)2+的NMR谱图证实了七元环由乙二胺和乙酰丙酮化合而成,并且推导出这些亲核加成-消除反应的反应机理.配合物1~3中的小分子环的合成在其它体系中尚未见报导,而在合成它们的反应中作为新产物随主体晶体析出,并由晶体结构解析和NMR得到了证实.     

取代环戊二烯钛络合物光解活泼自由基的研究

本文用自旋捕捉技术与ESR相结合的方法,研究取代环戊二烯钛络合物(RC₅H₄)₂TiCl₂(R=H,CH₃,C₂H₅,C₃H₇,C₅H₁₁,C₆H₁₁)光解的活泼自由基。结果表明,光解初级过程是Ti-(RC₅H₄)π键均裂,以生成(RC₅H₄)^·和(RC₅H₄) TiCl₂。(RC₅H₄)^·可为ND捕捉,并生成两种自由基加合物,其浓度比约为1:1。     

2,4,6-三吡啶基三嗪-芳香羧酸镝配合物的合成及其荧光性能

分别以2,4,6-三吡啶基三嗪( TPTZ)、对羟基苯甲酸和对苯二甲酸为配体,以Dy3+为中心合成了不同组成的5种配合物.对其进行了元素分析、紫外光谱、红外光谱、荧光激发和发射光谱的测定.推测配合物的组成分别为:(1)Dy(TPTZ)(NO3)3(C2H5OH)·H2O; (2) Dy (TPTZ)2 (NO3)3 (...     

便携式FTIR的机动车尾气检测方法

随着汽车排放标准的提高,相关VOC标准从总烃检测变为非甲烷碳氢化合物(NMHC)检测;随着含氧燃料的增加,增加了非甲烷有机气体(NMOG)测量。针对国内汽车尾气分析仪分析组分单一、精度有限、VOCs检测过程复杂等问题,提出了基于便携式FTIR的机动车尾气检测方法,基于立体角镜优化FTIR光学系统结构,提高动镜扫描速度,设计便携式且满足抗振动需求的快速FTIR光谱仪。FTIR红外光源输出波段范围为2～20 μm,分辨率为0.5 cm-1,扫描速度1 Hz,气体池光程为10 m,采用斯特林探测器,其光谱响应范围为600～6 000 cm-1。选择CH₄,C₂H₂,C₂H₄,C₂H₆,C₃H₆,n-C₅H₁₂,i-C₅H₁₂,C₇H₈,HCHO,C₂H₅OH,CH₃CHO这些典型HC化合物作为VOC气体检测的替代物。通过标准谱确定尾气成分的波段为900～1 100和2 700～3 100 cm-1,涵盖所有待测气体吸收波段。基于AVL台架测试,开展NEDC和WLTC工况实验测试,测试车辆为丰田威驰,测试油品为92号国五。便携式FTIR采用抽取方式进行尾气测量,原始的废气样本来自安装在排气管延长部分的多孔探头,前端安装样气取样装置,主要包括颗粒物过滤和除水汽装置,以防止污染FTIR光学系统。实验表明FTIR可以有效快速测量汽车尾气中CO,CH₄,NO和主要HC化合物,在FTIR检测限0.5 μmol·mol-1下会引入噪声信号,浓度可信度降低。通过分析可以看出输出气体平均浓度降级排列依次是：CO,C₂H₄,CH₄,NO,i-C₅H₁₂,C₂H₆,C₇H₈,n-C₅H₁₂,C₂H₅OH,CH₃CHO。从3个循环的NEDC工况可以看出,每种气体排放呈现一致的规律性变化。针对CO进行了SEMTECH-DS与FTIR测量数据的时间序列比较,结果呈现了较好的规律一致性,但是由于FTIR和SEMTECH-DS测量技术和取样稀释系统不同导致二者浓度差异较大。与传统尾气检测技术相比,便携式FTIR测量系统对瞬态事件有良好的响应,可以在线进行多组分浓度实时测量获取机动车的瞬时排放数据,在满足新规测试要求下,也可以为后期的机动车在实际道路上的排放特征分析和模拟提供可靠的数据支持。     

ArF laser-induced discharge interruption in a mixture of C2H3Cl/CF4/CH4, CF4/CH4, and C2H3Cl/He

The ArF-laser (193-nm)-induced discharge interruption is comparatively described in a mixture of C₂H₃Cl/CF ₄/CH₄, CF₄/CH₄, and C₂ H₃Cl/He using a hollow-cathode-type discharge tube. The unfocused ArF laser (typically 27 mJ/cm² and 10 ns duration) illuminated both the negative glow inside the hollow cathode and the column between the two electrodes. With a 1.8-torr mixture of C₂ H₃Cl/CF₄, the discharge current of 1 mA was decreased rapidly with a current-decay time constant of 1 μs and a current-decay rate of 1 kA/s. With a 1.5-torr mixture of CF₄/CH₄, 2.2 μs and 450 A/s were obtained. With a 1.5-torr mixture of CH₂H₃Cl/He, a time constant of over 3 μs and a rate of less than 300 A/s were obtained. An analysis of the discharge interruption induced by ArF-laser irradiation is given in terms of photon-plasma kinetics. The current peak induced by ArF irradiation is also explained for a mixture of C₂H₃ Cl/He in terms of photoionization and photodetachment processes     

Reactions of π-allyl with atomic oxygen and hydroxyl on Ag(110)

The oxidation of the adsorbed π-allyl (η³-C₃H₅), prepared on atomic oxygen- and hydroxyl-covered Ag(110) by dissociation of allyl chloride (C₃H₅Cl), is investigated with temperature-programmed desorption and high-resolution electron energy loss spectroscopy. Allyl chloride adsorbs molecularly on oxygen-covered Ag(110) at 110 K. Upon heating to 180 K, some allyl chloride dissociates to form π-allyl and atomic chlorine, and the remainder desorbs molecularly. The π-allyl undergoes combustion to form hydroxyl or carbonate until all of the free oxygen is consumed by 200 K. Migratory insertion of hydroxyl into excess π-allyl commences near 220 and finishes by 250 K, forming adsorbed allyl alcohol (C₃H₅OH), which reacts either with excess hydroxyl near 240 K to form allyl alkoxy (η¹(O)-C₃H₅O) and water, or with π-allyl at 250 K to form allyl alkoxy and propylene (C₃H₆). Th allyl alkoxy evolves acrolein (C₃H₄O) by β-hydrogen elimination near 285 K, and propylene is evolved concurrently as the hydrogen released by this reaction rapidly scavenges π-allyl. Finally, the remaining π-allyl dimerizes to form 1,5-hexadiene (C₆H₁₀), which desorbs at 315 K. The gross observations of reaction pathways and temperatures are used to evaluate important aspects of the thermochemistry of these reactions.     

乙基苯低压预混火焰动力学模型研究

本文报道了我们发展的一个包含176个物种和806个反应的乙基苯火焰模型,用于模拟4.0 kPa压力下的富燃乙基苯火焰（φ=1.90）。结果表明本模型可以很好地预测各种产物及中间体的摩尔分数曲线。通过生成速率分析得到了乙基苯在富燃条件下的反应路径。分析结果显示,乙基苯在富燃条件下的主要分解路径为C₆H₅C₂H₅→C₆H₅CH₂→C₇H₆→C₅H₅4→C₃H₃→C₃H₂,产生的C₃H₂再经过氧化反应序列生成主要产物CO。此外,乙基苯支链上一系列的脱氢/β-断键反应也对乙基苯的分解具有不可忽视的作用。本模型为发展长链芳香烃模型打下了基础,有助于对未来实用燃料和航空替代燃料中长链芳香烃燃烧持性进行预测。     

Defect induced surface chemistry: A comparison of the adsorption and thermal decomposition of C2H4 on Rh{111} and Rh{331}

The adsorption and thermal decomposition of C₂H₂ on Rh{111} is compared to the atomically stepped Rh{331} surface over a temperature range of 300 to 800 K. Using X-ray photoelectron spectroscopy (XPS) we find that the C 1s spectra as a function of C₂H₄ exposure exhibit a shift in binding energy (E_b) from 283.5 eV at 1 L C₂H₄ exposure on both surfaces to 283.8 eV on Rh{33 and to 284.1 eV on Rh{111} at saturation coverage (4 L). Careful analysis of the C 1s E_b value and full width at half maximum as a function of surface temperature after a 10 L exposure of C₂H₄ at 300 K reveals that a species consistent with a C₂H adsorbate composition is formed between 400 and 450 K on Rh{111}. This species is also observed on Rh{331} although at the lower temperature of 375 K. Computer peak deconvolution of the C 1s spectra between 500 and 700 K suggests that a CH_ads or C_ads surface fragment is formed and increases in concentration at the expense of the C₂H species as the surface temperature increases. Above 750 K a graphite overlayer is formed on both surfaces. This overlayer, however, exhibits a low degree of carbon π-character bonding on Rh{331}. The adsorption and decomposition mechanisms suggest that the 300 K C₂H₄ adsorbate on Rh{331} is ethylidyne and that the stepped surface is more thermally reactive than the flat Rh{111} surface.     

Auger electron spectroscopy and electron energy loss spectroscopy studies on carbonization of Si(100) and (111) surfaces with ethylene

The reactions of Si(100) and Si(111) surfaces at 700 °C (973 K) with ethylene (C₂H₄) at a pressure of 1.3×10⁻⁴ Pa for various periods of time were studied by using Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS). For a C₂H₄ exposure level, the amount of C on the (111) surface was larger than that on the (100) surface. The formation of β-SiC grain was deduced by comparing the C_KLL spectra from the sample subjected to various C₂H₄ exposure levels, and from β-SiC crystal.     

Large-scale synthesis of polyynes with commercial laser marking technology

The space-confined synthesis method has been an efficient way for the preparation of linear carbon chains. However, the large-scale preparation of linear carbon chains still faces many challenges due to the lack of methods for the large-scale synthesis of precursors, such as short carbon chains (polyynes), and regulation technology for the transport of reactants in one-dimensional space. Here, we report a facile method for the rapid preparation of polyynes in large quantities using a commercial laser marking machine. Spectroscopic characterizations show that a large number of polyynes, such as C₈H₂, C₁₀H₂, C₁₂H₂, and C₁₄H₂, can be produced by ablating the graphite plate immersed in the organic liquid using a laser marking machine. The results of in situ Raman spectroscopy investigation of C_2nH₂-filled single-walled carbon nanotubes further confirm that a variety of polyyne molecules are synthesized. Meanwhile, in situ Raman spectroscopy also shows that the local heating treatment can accelerate the filling process of C_2nH₂ into one-dimensional channels. This work provides new insights into the study of linear carbon chains and space-confined synthesis methods.     

PVP在水/丙酮混合溶剂中分子运动行为的研究

通过对粘度、自旋-自旋弛豫时间以及1H NMR谱的测定,研究了PVP在不同体积配比的水/丙酮溶液中的特性粘数变化和分子运动规律,并讨论了引起这些变化的原因.结果表明:随着丙酮的不断加入,PVP的特性粘数[η]先增加后减小,而T2H先减小后增大.[η]出现最大值也是T2H出现最小值的时候,丙酮的体积百分数为40%.丙酮的加入破坏了水分子间自身氢键相互作用形成的网状结构,解离出来的水分子被PVP优先吸附到大分子链上,部分与羰基形成氢键,另一部分以自由水的形式被包裹在大分子线团内.水分子的不断进入以及与水形成新的氢键使PVP链逐渐伸展,引起特性粘数的增大,分子运动受阻.当丙酮含量增加到一定程度时,水的含量不足以使大分子链继续膨胀,故链呈卷缩状态,使大分子运动逐渐恢复自由.1H NMR谱中各质子的化学位移变化也证实了此过程中的氢键变化规律.     

关于N-苯基-萘胺的光分解过程

采用ESR方法研究了α-和β-N-苯基取代萘胺在苯溶液中的分解过程及其反应中间体.结果表明,有三种自由基被检测到,即H,C₁₀H·₇和C₆H·₅(H)N·自由基.其中值得注意的是萘自由基的生成,这意味着在一定的光解条件下,苯基萘胺分子中的C-N键可发生断裂,萘基可从氮原子上断裂下来.同时,通过调节自旋捕捉剂的浓度与添加光敏剂,可以明显地改变三种自旋捕获物的相对生成比例,借此得到三种自由基结构与光稳定性的信息.此外,本文还结合量子化学的计算讨论了此光解过程各种自由基生成的可能性.     

沸石类咪唑骨架材料吸附分离天然气的分子模拟

采用巨正则蒙特卡洛方法研究C₂H₆, CO₂和CH₄三种气体在两种沸石类咪唑骨架材料 (ZIF)-ZIF-2和ZIF-71中的吸附与分离性能. 考察了C₂H₆, CO₂和CH₄三种气体在ZIF-2和ZIF-71中的单组分吸附等温线、吸附热; C₂H₆-CH₄, CO₂-CH₄ 与C₂H₆-CO₂等摩尔二元混合物的分离; 以及C₂H₆-CO₂-CH₄三元体系的分离性能. 研究结果表明: 低压下不同气体的吸附量大小与其吸附热关系紧密; 而高压下因有限的孔空间, 尺寸较小的气体分子吸附量增长趋向更快; 多组分吸附分离中, 低压下能量效应通常占据主导, ZIF优先吸附作用力较强的组分; 高压下堆积效应影响显著, ZIF会优先吸附尺寸较小的组分. ZIF-2和ZIF-71对这3种二元体系的分离性能良好. 对于三元混合物吸附分离, 在常温下3000-4000kPa范围内, ZIF-2具有良好的天然气净化性能, 可有效地分离出天然气中的C₂H₆和CO₂. 关键词： 巨正则蒙特卡洛模拟 天然气分离 沸石类咪唑骨架     

光声光谱多组分气体分析仪的交叉干扰特性研究

设计了一套基于红外热辐射光源的光声光谱多组分气体分析仪.通过分析多组分气体间交叉干扰的主要因素以及特征气体的红外吸收谱线,确定了中红外带通滤光片的参数.利用标准气体对设计的光声光谱仪进行标定,研究了待测气体之间交叉干扰的定量关系,并利用湿度发生器对装置受到水气干扰情况进行分析.实验结果表明,C2H2对CH4、CH4对C...     

多组分传质过程的Maxwell-Stefan方法模拟

为定量研究多组分系统在多孔介质内传质过程中组分之间的交互作用现象,本文基于Maxwell-Stefan模型对CH₄/Ar/H₂混合气体在单个直孔道内的纯扩散过程和C₂H₆/C₃H₈/N₂混合气体在活性炭上的吸附扩散过程进行了模拟,定量地描述和分析了多组分系统中组分之间在传质过程中的交互作用。研究表明:对于扩散过程,组分之间的交互作用表现为大分子对小分子的拖带;对于吸附过程,这种作用表现为强吸附质能够替代已被吸附在吸附剂表面的弱吸附质;主体扩散为主要的传质形式。     

Investigation of the role of oxygen in NO reduction by C2H4 on the surface of stepped Pt(3 3 2)

The influence of pre-dosed oxygen on NO–C₂H₄ interactions on the surface of stepped Pt(3 3 2) has been investigated using Fourier transform infrared reflection–absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). The presence of oxygen significantly suppresses the adsorption of NO on the steps of Pt(3 3 2), leading to a very specific adsorption state for NO molecules when oxygen–NO co-adlayers are annealed to 350 K (assigned as atop NO on step edges). An oxygen-exchange reaction also takes place between these two kinds of adsorbed molecules, but there appears to be no other chemical reaction, which can result in the formation of higher-valence NOx.

C₂H₄ molecules which are post-dosed at 250 K to adlayers consisting of ¹⁸O and NO do not have strong interactions with either the NO or the ¹⁸O atoms. In particular, interactions which may result in the formation of new surface species that are intermediates for N₂ production appear to be absent. However, C₂H₄ is oxidized to C¹⁸O₂ by ¹⁸O atoms at higher annealing temperature. This reaction scavenges surface ¹⁸O atoms quickly, and the adsorption of NO molecules on step sites is therefore quickly restored. As a consequence, NO dissociation on steps proceeds very effectively, giving rise to N₂ desorption which closely resembles that following only NO exposure on a clean Pt(3 3 2), both in peak intensity and desorption temperature. It is concluded that the presence of ¹⁸O₂ in the selective catalytic reduction (SCR) of NO with C₂H₄ on the surface of Pt(3 3 2) does not play a role of activating reactants.     

Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry–Perot tunable filter

Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating(FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C_2H_2 detection can be applied in practical applications.