多维气相色谱法测定催化裂化气体组成

１引言 催化裂化气体组成测定是炼油厂中重要的分析项目之一,其组成除含有Ｃ１～Ｃ５等轻烃组分外,还含有Ｈ２、Ｏ２、Ｎ２、ＣＯ、ＣＯ２等永久性气体,常规方法是利用３台气相色谱仪,一个样品３次进样,达到全组分分离,操作繁琐且准确度差。本文介绍的多维气相色谱法测定催化裂化气体组成,一个样品只需一次进样就能达到全组分的分离检测,操作简便,且重复性好,准确度高。２实验部分２．１仪器和色谱柱 ＨＰ５８９０Ⅱ型气相色谱仪;ＨＰ３３９６Ⅱ型积分仪（美国惠普公司）。癸二腈（柱１Ａ０．６ｍ×３．２ｍｍｉ．ｄ．：柱１Ｂ …     

毛细管多维气相色谱法分析炼厂气

用ＨＰ６８９０气相色谱仪,使用多孔层空心毛细管柱（ＰＬＯＴ）,选用ＨＰ－ＰＬＯＴ／Ｐｏｒａｐａｃｋ Ｑ色谱柱测定ＣＯ２;ＨＰ－ＰＬＯＴ ５Ａ分子筛柱测定Ｏ２,Ｎ２,ＣＨ４;ＨＰ－ＰＬＯＴ／Ａｌ２Ｏ３柱测定有机烃类。采用３阀４柱色谱运行系统,用ＦＩＤ及ＴＣＤ分别检测烃类及无机气体组分。用色谱工作站控制气动切换阀切换气样走向及两种检测器数据的转换校正和归一化定量计算,用已知物对照法定性,测定了炼厂气中     

用二维色谱技术测定聚合反应气体组成

介绍一种无阀切换的二维气相色谱分析方法。采用两根不同性质的色谱柱并联连接，样品分别经两根色谱柱分离后汇合在一起进入同一检测器。一次进样可同时测定Ｈ２、Ｏ２、Ｎ２及Ｃ１～Ｃ３的组分。     

倒数示波计时电位法在合金样品测定中的应用

应用倒数示波计时电位法，在含有吸附络合物的溶液中，采用桂汞电极作为极化电极，测定了Ｃｕ＾２＋、Ｎｉ＾２＋、Ｃｄ＾２＋、Ｐｂ＾２＋等几种金属离子的检测下限，并通过沿（ｄＥ／ｄｔ）－１￣Ｅ曲线上的峰高对合金样品进行定量分析，得到满意结果。实现了示波分析由常量到微量的飞跃。     

CO2选择性氧化甲烷制C2烃催化剂La2O3/ZnO的氧化还原和CO2吸附性能

Ｌａ２Ｏ３／ＺｎＯ催化剂体系在以二氧化碳作为氧化剂的甲烷氧化偶联反应中具有很高的Ｃ２烃选择性和稳定性．采用ＣＯ２－ＴＰＤ－ＭＳ和ＴＰＲ技术考察了Ｌａ２Ｏ３／ＺｎＯ对ＣＯ２的吸附性质及其氧化还原行为．结果表明：（１）Ｌａ２Ｏ３／ＺｎＯ催化剂体系存在着强、弱两种碱中心，其中弱碱中心数量随样品中Ｌａ２Ｏ３含量增加而减少，强碱中心强度随样品中Ｌａ２Ｏ３含量增加而增强．（２）由于组分相互作用，高温下，Ｌａ２Ｏ３／ＺｎＯ易产生晶格氧空位，使之对ＣＯ２的吸附增强，吸附后的ＣＯ２与晶格氧作用形成立方晶型Ｌａ２Ｏ２ＣＯ３．（３）Ｌａ２Ｏ３／ＺｎＯ表面的Ｌａ３＋和Ｚｎ２＋可以部分被还原，由于组分间的相互作用，使得二者的还原都较单一组分存在时更难．（４）Ｈ２－ＣＯ２－Ｈ２氧化还原循环实验表明，Ｌａ２Ｏ３／ＺｎＯ表面被部分还原后，ＣＯ２可以将部分被还原的表面再氧化．在此基础上对Ｌａ２Ｏ３／ＺｎＯ催化剂上甲烷与ＣＯ２转化为Ｃ２烃的机制也进行了讨论．     

分析变压器油的新型柱和转化炉

一种新型的变压器分析柱及微型转化炉,可用一根柱,一次进样完成Ｈ２、ＣＯ、ＣＨ４、ＣＯ２、Ｃ２Ｈ４、Ｃ２Ｈ６和Ｃ２Ｈ２的全分析。而研制成功的微型转化炉有较高的转化率,且寿命长,可降低仪器成本 。     

超细粒子K-Co-Mo催化剂中钴含量对催化剂结构及其合成低碳醇性能的影响

采用溶胶－凝胶法,制备了不同钴含量的钴钼超细粒子氧化物,将其与Ｋ２ＣＯ３干混后进行硫化。使用Ｘ－射线衍射（ＸＲＤ）和扩展Ｘ光吸收精细结构（ＥＸＡＦＳ）对样品进行结构表征,同时测试硫化态样品的ＣＯ加氢合成低碳混合醇性能。结构表征结果表明,不含钴的氧化态样品,主要以颗粒度较大的ＭｏＯ２物种存在;添加钴后,样品粒子的颗粒度大幅度降低,钴钼组分主要以ＣｏＭｏＯ３物种的形式存在,当钴含量增加时,ＣｏＭｏＯ３     

双柱串联色谱一次分析甲烷部分氧化制合成气产物

采用ＰｏｒａｐａｋＮ色谱柱，延迟空管和１３Ｘ分子筛色谱柱串联方法，用一个ＴＣＤ，通过ＡｎａＳｔａｒ色谱工作站实时采集信号进行在线分析，可成功地一次性和分析ＰＯＭ产品气听ＣＨ４，ＣＯ，ＣＯ２，Ｏ２等几处可能组分，消除了两台色谱仪无法同时取样分析和在两个不同ＴＣＤ检测器上采集数据引起的实验误差，提高了分析的可靠性。     

罗布泊地貌地质遗迹中某些元素的分析

用中子活化分析法测试了新疆罗布泊地区地质样品中的某些痕量、微量及常量元素含量,特别是对样品中放射性元素作了检测。结果表明,该地区的地质遗迹样品中,痕量、微量及常量元素的含量与中国大陆地壳中的含量相当,无明显的放射性异常;把这些样品当作建筑材料的原材料来使用,是安全的;通过对这些样品的检测分析,为该地区的化探普查提供了可靠的依据。     

甲烷在SrO－La_2O_3／CaO催化剂上的氧化偶联──IV．热点温度效应和反应气中添加CO_2的影响

研究了甲烷在ＬＣ和ＳＬＣ催化剂体系上氧化偶联反应过程的热效应现象和反应气中添加ＣＯ２对催化剂反应行为的影响．在不使用稀释气的情况下，当反应温度由８７３升至９２３Ｋ时，反应活性存在一个突变点．这主要是由ＣＨ４燃烧反应放出大量热使催化剂床层的局部温度很高，形成一个局部过热区，因此引发甲烷氧化偶联．此即所谓热点温度效应，它严重影响催化剂活性评价结果的可靠性和重复性．在反应气中添加ＣＯ２对ＬＣ几乎无影响；由于ＳＬＣ中各组分与ＣＯ２作用生成碳酸盐，使催化剂表面氧浓度显著减少，导致催化剂的反应活性大大降低和严重失活．     

Plasma chromatography of n-alkyl acetates

Plasma chromatography is a technique which permits characterization and analysis of trace constituents in a gaseous mixture at atmospheric pressure. It is especially well suited as a gas chromatographic detector. Operating at atmospheric pressure, the instrument uses either air or nitrogen carrier gas into which the sample is injected directly or through a gas chromatograph. The compounds are identified by their characteristic positive and negative mobility spectra, which consist of simple molecular and dissociative ions. Quantities as low as 10⁻⁶ to 10⁻¹² g are detectable. For use as a gas chromatographic detector, reference mobility spectra of compounds are needed. Those of n-alkanes, alcohols, ketones, halogenated aromatics, substituted nitrobenzenes, polychlorinated biphenyls, alkyl halides, aliphatic N-nitrosamines and isomeric phthalic acids have been previously reported. This study reports the reference mobility spectra produced by n-alkyl acetates. These compounds display strong positive mobility spectra but no negative mobility spectra. The spectra all show characteristic MH⁺, M(H₂O)_nH⁺ and (M₂)H⁺ along with the alkyl fragment ions.     

Gas chromatographic analysis of trace gas impurities in tungsten hexafluoride

Highly reactive fluorinated gaseous matrices require special equipment and techniques for the gas chromatographic analysis of trace impurities in these gases. The impurities that were analysed at the low-microg/l levels included oxygen, nitrogen, carbon dioxide, carbon monoxide, sulfur hexafluoride and hydrogen. This paper describes the use of a system utilising backflush column switching to protect the columns and detectors in the analysis of trace gas impurities in tungsten hexafluoride. Two separate channels were used for the analysis of H2, O2, N2, CO, CO2 and SF6 impurities with pulsed discharge helium ionisation detection.     

六氟化硫中痕量一氧化碳和二氧化碳的气相色谱检测及其在断路器故障分析中的应用

为了准确分析高浓度SF₆中痕量的CO及CO₂,发展了可靠的气相色谱-火焰离子化检测器（GC-FID）方法。通过双Porapak Q色谱柱结合阀切换将SF₆从待测样品中分离并排出检测系统,从而避免SF₆可能造成的在线转化柱中毒现象,同时实现CO和CO₂的完全分离;通过在线镍催化将CO和CO₂的检测转化为对CH₄的检测,极大地提高检测灵敏度。结果显示,该方法对CO和CO₂的检测互不干扰,两者都可在2~500 μL/L范围内呈现良好的线性相应,测定重复性好（RSD小于2%）,准确度高。建立的GC-FID方法可直接用于SF₆高压断路器中痕量CO及CO₂的检测,为SF₆相关电气设备潜伏性故障诊断提供了研究手段。     

A Low Cost Gas Sampling Valve and Gc Set-Up for Analysis of Low Concentration Gas Mixtures

Abstract

A gas sampling valve suitable for on-line injection of low pressure (< 0.5 torr) gas mixtures is described. Its advantages over the commercially available valves are enumerated. An error of < 3 per cent due to non-reproducibility in sample injection was observed. A simple arrangement of column and hot wire detector together with this valve enabled quantitative separation of CO and O₂ with a lower limit of ～ 1 × 10^?7 moles for each component.     

The effect of two gases forming supercritical fluids (Xe and CO2) on the spectral characteristics and analytical capabilities of microwave induced plasmas

A comparative study of the effect of CO₂ and Xe added along with the plasma gas to He and Ar microwave induced plasmas (MIPs), simulating possible conditions to be used when a MIP is employed as specific detector for supercritical fluid chromatography (SFC), has been carried out. The proportions of CO₂ and Xe to the plasma gas investigated are comparable to the typical percentages used for SFC-MIP couplings. The study has been performed with two different MIP systems: an atmospheric pressure discharge held in a Beenakker cavity TM₀₁₀ and a reduced pressure surfatron-MIP.The influence of CO₂ and Xe addition on the spectrochemical properties of the discharge has been studied by using the atomic emission of mercury and some typical non-metals (chlorine, carbon and sulfur) at different wavelengths (atomic and ionic lines). Results showed that ion line emission intensities are always reduced more significantly than atom line emissions by both dopant gases on study, whatever the pressure. In general terms, however, the effect of adding Xe is less severe, both for atom and ion lines, than that of CO₂; in most cases the detection limits (DLs) observed are better for Xe than for CO₂ as dopant gas. In fact, the DLs obtained for the selected lines of mercury measured were practically unaltered by the addition of 0.2% Xe to atmospheric pressure Ar or He MIPs. CO₂ addition (0.2%) produced about 1.5 times worsening of the observed DLs for mercury. For non-metal analyses better DLs were also obtained, in general terms, with Xe than with CO₂ as dopant gas.     

Ammonia monitoring at trace level using photoacoustic spectroscopy in industrial and environmental applications

An ammonia traces analyser based on photoacoustic spectroscopy is described. The system uses a CO(2) laser and a properly designed resonant photoacoustic cell to achieve ammonia detection at sub-parts-per-billion (ppb) level. The instrument features unattended automatic on-line monitoring of ammonia with a detection limit of 0.1 ppb. Interferences from atmospheric CO(2) and H(2)O are efficiently suppressed by a careful selection of the laser wavelength and a compensation of the water vapour signal made with a high-precision hygrometer. The cell design enables continuous measurement at high flow rates (up to 5 l/min), which guarantees a fast response time of the system for the monitoring of ammonia, a sticky polar molecule that adheres to most surfaces. Various examples of applications of the instrument in the semiconductor industry and for atmospheric pollution monitoring are presented. They demonstrate the excellent performances of the system and its suitability for these applications.     

Development of an on-line low gas pressure cell for laser ablation-ICP-mass spectrometry.

An on-line low gas pressure cell device has been developed for elemental analysis using laser ablation-ICP-mass spectrometry (LA-ICPMS). Ambient gas in the sample cell was evacuated by a constant-flow diaphragm pump, and the pressure of the sample cell was controlled by changing the flow rate of He-inlet gas. The degree of sample re-deposition around the ablation pit could be reduced when the pressure of the ambient gas was lower than 50 kPa. Produced sample aerosol was drawn and taken from the outlet of the diaphragm pump, and directly introduced into the ICP ion source. The flow rate of He gas controls not only the gas pressure in the sample cell, but also the transport efficiency of the sample particles from the cell to the ICP, and the gas flow rate must be optimized to maximize the signal intensity of the analytes. The flow rates of the He carrier and Ar makeup gas were tuned to maximize the signal intensity of the analytes, and in the case of (238)U from the NIST SRM610 glass material, the signal intensity could be maximized with gas flow rates of 0.4 L/min for He and 1.2 L/min for Ar. The resulting gas pressure in the cell was 30 - 35 kPa. Using the low gas pressure cell device, the stability in the signal intensities and the resulting precision in isotopic ratio measurements were evaluated. The signal intensity profile of (63)Cu obtained by laser ablation from a metallic sample (NIST SRM976) demonstrated that typical spikes in the transient signal, which can become a large source of analytical error, were no longer found. The resulting precision in the (65)Cu/(63)Cu ratio measurements was 2 - 3% (n = 10, 2SD), which was half of the level obtained by laser ablation under atmospheric pressure (6 - 10%). The newly developed low-pressure cell device provides easier optimization of the operational conditions, together with smaller degrees of sample re-deposition and better stability in the signal intensity, even from a metallic sample.     

Hydrogen Isotope Exchange Reactions in an Atmospheric Pressure Discharge Utilizing Water as Carrier Gas

Allowing water/hydrogen or water/hydrogen/He gas mixture to flow through micro- hollow type of electrodes and applying 60 Hz AC power between the electrodes made it possible to sustain large area and atmospheric pressure discharge. The electrode assembly was constructed by sandwiching a dielectric spacer with two thin metal sheets and boring an array of micro holes through them. Another variation of the assembly was prepared by stacking thin metallic sheets so that the stack functions as an electrode through which the gas mixture flows for generating dielectric barrier discharge. A large volume of the gas mixture, while producing plasma, underwent instantaneous hydrogen isotope exchange reactions between H₂O and D₂O or between D₂O and H₂ gas molecules. The efficiency of the atmospheric pressure discharge was assessed by measuring the extent of the exchange reactions at a given flow rate of the gas mixture.     

Laser induced and controlled chemical reaction of carbon monoxide and hydrogen

Bimolecular chemical reaction control of gaseous CO and H(2) at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO(2)(+), C(2)H(2)(+), CH(+), and CH(3)(+) were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO(2) is shown to be dependent on laser intensity, irradiation time, and on the presence of H(2) in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.     

Hydrogen analysis in solid samples by utilizing He metastable atoms induced by TEA CO2 laser plasma in He gas at 1 atm

A TEA CO₂ laser (350 mJ–1.5 J, 10.6 μm, 200 ns, 10 Hz) was focused onto a metal sub-target under He as host gas at 1 atmospheric pressure with a small amount of impurity gas, such as water and ethanol vapors. It was found that the TEA CO₂ laser with the help of the metal sub-target is favorable for generating a strong, large volume helium gas breakdown plasma at 1 atmospheric pressure, in which the helium metastable-excited state was then produced overwhelmingly. While the metal sub-target itself was never ablated. The helium metastable-excited state produced after the strong helium gas breakdown plasma was considered to play an important role in exciting the atoms. This was confirmed by the specific characteristics of the detected H emission, namely the strong intensity with low background, narrow spectral width, and the long lifetime. This technique can be used for gas and solid samples analysis. For nonmetal solid analysis, a metal mesh was introduced in front of the nonmetal sample surface to help initiation of the helium gas breakdown plasma. For metal sample, analysis can be carried out by combining the TEA CO₂ laser and an Nd–YAG laser where the Nd–YAG laser is used to ablate the metal sample. The ablated atoms from the metal sample are then sent into the region of helium gas breakdown plasma induced by the TEA CO₂ laser to be excited through the helium metastable-excited state. This technique can be extended to the analysis of other elements, not limited only to hydrogen, such as halogens.