一种双光束红外光谱及其在气固相多相催化反应实时原位表征中的应用（英文）

单光束红外光谱技术(原位傅立叶透射变换红外、原位漫反射红外和衰减全反射红外光谱技术)虽然已经用于气固相多相催化反应的原位表征中,但这些光谱在真实反应条件下会受到气体分子振动光谱和加热条件下产生的发射光谱的严重影响,不能实时获得催化剂表面的真实信息.另外,由于在真实的气固相多相催化反应过程中,催化剂本底的信息会随着反应时间的延长而发生变化,因此单光束红外光谱技术在扣除本底信息方面存在误差.为了实现在反应条件下,实时、原位表征催化剂表面的状态,我们报道了一种双光束红外光谱表征技术.该技术包括双光束红外光谱系统及双光束红外反应池.其特征在于:实时双光束原位红外光谱系统由两台完全相同的红外光谱仪和双光束红外反应池组成.双光束红外反应池由完全相同的样品池和参考池连接而成,样品池和参考池处于同一水平线上分别对应于样品光谱仪和参考光谱仪,由计算机同步控制两台红外光谱仪,排除实时状态下的气体分子振动光谱干扰和加热条件下产生的发射光谱干扰.该技术可以对真实反应条件下的气固相多相催化反应进行实时原位表征.通过应用程序的关联可以实时、同步采集样品光束和背景光束谱图来得到催化剂表面物种随反应时间变化的真实信息.该技术克服了单光束红外光谱在原位多相催化反应表征方面的缺陷,使表征结果变得更加精确可靠.该技术还可以在变化的气相组分条件下,获得不同温度下、实时的催化剂表面活性中心、活性相和中间物种的信息.采用上述双光束红外光谱仪对丁烯在纳米HZSM-5催化剂上芳构化反应过程进行了实时、原位观测,首次在实际反应条件下,观察到了异丁烯在纳米HZSM-5沸石的表面Br?nsted酸中心上经历吸附、活化、聚合、环化等反应步骤生成芳烃的过程.     

新型高温高压(真空)原位红外光谱气固样品池的研制

无论是均相或是多相催化反应,由于受各种参数的影响,整个催化过程是极为复杂的。尽管如此,利用各种近代物理测试方法,人们仍有可能从分子水平乃至原子水平上来研究催化反应,指导催化剂的制备,选择最佳反应条件。反应状态下的原位红外光谱测试方法,是近年来发展较为迅速的测试方法之一,而实现原位红外光谱测试的关键设备,是能耐高温高压的红外光谱样品池。几年前,作者曾经报导了加温加压原位红外光谱液体样品池的研制工作,该样品池已在均相络合催化反应机理的研究中得到了应用。为了研究多相催化及均相固相化反应体系,新近又研制了高温高压(真空)原位红外光谱气固样品池。     

电化学原位扫描显微红外反射光谱及其对铂表面CO吸附的红外成象

利用Fourier变换红外光谱仪 ,红外显微镜和X Y扫描平台 ,通过设计和研制原位红外显微池和计算机接口及控制软件 ,建立了电化学原位扫描显微红外反射光谱 .研究工作显示 ,这一新的空间分辨原位红外反射光谱技术不仅可以获得固 /液界面环境中表面微区振动光谱的信息 ,还可以用于电极表面红外成象 .获得的CO在Pt多晶电极表面吸附性能的化学图象在 10 -2 cm尺度上给出电极表面微区反应性能的不均一性及其分布 .     

高低温环境下红外光谱原位表征系统的研制

研制的高低温环境下红外光谱原位表征系统将红外光谱同高低温原位红外体系组合起来,为高低温原位红外反应机理的深入研究提供有效信息,同时为构建高效稳定的原位红外研究提供新的技术支撑.高低温环境下红外光谱原位表征系统通过液氮制冷与加热调控,在真空或常压的状态下为光谱测量提供低温恒温环境,并可在一定的温度范围内提供可进行原位预处理或原位反应的高温环境.高低温环境下红外光谱原位表征系统可以适用于任何物质研究,尤其适用于液氮环境下气体吸附研究,比如反应中间体的过程捕捉、探针分子弱吸附方面的研究、单原子催化剂的鉴定以及探针分子吸附表征等.因而高低温环境下红外光谱原位表征系统在这些领域具有极高的通用性和实用性.     

多相催化时空演变的全生命周期表征策略

可持续发展的化学工业需要新型高效的催化材料和催化过程,尤其需要生态友好、本质安全的新催化过程,其本质是提高合适反应器内催化剂的选择性、活性和稳定性.因此,通过原位技术实时表征反应状态下的催化剂结构并同步测试催化性能,有助于全面研究真实反应条件下催化剂及其表面物种随时间的演变过程,深入理解催化剂构效关系的本质,为开发新一代催化技术提供科学依据.迄今,在实际催化体系中实现催化剂从活化、运行到失活的全生命周期表征仍存在巨大挑战.本文综述了分子筛、金属、金属氧化物三类典型催化剂在甲醇制烯烃、费托合成、丙烷脱氢等催化反应中的全生命周期时空演变,分析了所采用的表征研究策略,以期为新型工业催化的应用基础研究提供启示.据文献报道,甲醇制烯烃反应案例主要利用了原位紫外-可见光谱和固态核磁共振光谱等获得SAPO-34分子筛催化剂从诱导期、自催化期到失活期的表面烃池物种性质和动态演变;费托合成反应案例主要利用了同步辐射X射线衍射计算机断层扫描和X射线吸收光谱等技术研究单个毫米级Co/γ-Al2O3催化剂颗粒在还原条件和费托合成条件下的催化剂结构演变;丙烷脱氢反应案例主要结合原位的紫外-可见和拉曼光纤探头分析了CrOx/Al2O3催化剂在700 ml固定床反应器中不同床层积炭的时空演变.这些研究案例表明,因受限于表征仪器的时空分辨率和适用工况,多数重要的催化反应尚未完全实现工业条件下的全生命周期表征;但通过合理简化非关键变量,可以获得近似工业条件下的多相催化时空演变规律,这些原位表征研究拓展了多相催化的新认识新发现.着眼未来,近似工业反应条件的原位表征、多尺度的原位表征装置设计、反应条件下的计算模拟等策略将在催化研发中发挥重要作用.这些全生命周期表征策略反映了催化研究范式的转变,但将其应用于工业实践仍面临许多科学和工程的挑战.从实际应用角度看,还需综合考虑原位表征技术的成本、安全性和准确性,重视催化剂颗粒及反应器尺度的原位表征,不断推进新型催化剂的研发.     

原位衰减全反射表面增强红外光谱实验技术

介绍了原位研究电极,溶液界面反应的技术--衰减全反射表面增强红外光谱实验技术(ATR-SEIRAS)的产生背景和工作原理,重点描述了ATR-SEIRAS实验技术的关键:光谱电化学池的构造和薄膜电极的制备.与IRAS相比,ATR-SEIRAS技术可以更容易消除溶剂的背景吸收,获得较高的表面灵敏度,而且允许物质在电极表面自由扩散.与循环伏安相结合,利用ATR-SEIRAS技术可以实时监测电极,溶液界面问的反应.选择了利用ATR-SEIRAS实验技术原位研究功能表面的构造和性质、分子识别和反应中间体的形成等方面的应用实例,分析了ATR-SEIRAS实验技术的研究方向.     

高温高压(真空)气固原位红外光谱样品池的研制

为研究多相催化和均相固相化反应体系,中国科学院兰州化学物理研究所研制了GS-II型高温高压(真空)气固原位红外光谱样品池,该池实为带红外光     

原位漫反射红外光谱技术用于气固催化反应机理的研究

漫反射傅立叶变换红外光谱技术是一种对固体粉末样品进行直接测量的光谱方法,是近年来发展起来的一项较理想的原位表征技术。原位漫反射红外技术由于可直接对催化剂表面的吸附态物种给出红外信号,可方便地跟踪鉴定反应中间态和产物,从而为催化反应体系反应机理的考察给出直接的证据。本文对于原位漫反射红外技术用于低温水煤气变换反应和水汽逆变换反应、醇类的水蒸汽重整、含CO₂的合成气制取甲醇、低碳烃制合成气、CO催化氧化以及其他烃类和含氧化合物的氧化等方面进行了综述,认为该技术可很好地剖析气固相催化反应机理。     

HZSM-12分子筛催化剂的化学吸附和程序升温脱附

自从Amenomiya和Cvetanovic在闪脱基础上发展了程序升温脱附技术(简称TPD)以后,由于它能够在接近反应条件下考察催化剂的表面性质,而且设备简单,所以被广泛应用于多相催化研究。它不但能考察金属和氧化物催化剂,而且也能考察分子筛催化剂。本文用吸附等压线和TPD技术表征了HZSM-12分子筛催化剂的表面     

新型两亲性HZSM-5沸石催化剂对环己烯水合相界面反应的催化研究

采用三甲基氯硅烷对HZSM-5沸石样品进行外表面修饰,制得两亲性沸石样品,该类两亲性沸石能分布于水、油两相界面处.改性后样品的红外光谱中末端硅羟基峰的强度明显降低,并出现CH₃基团的C_H伸缩振动吸收峰,证实部分亲水性表面硅羟基被亲油性硅烷基团取代.这类两亲性样品在不加共溶剂及静置条件下,对环己烯水合相界面催化反应的催化活性远远高于改性前的HZSM-5沸石.由于该相界面反应是以孔道内为主的反应,三甲基氯硅烷经改性制备出的亲油性HZSM-5沸石也呈现出较高的活性.     

Responses to the comments of Prof. Frederic Meunier

正Dear Prof. Frederic Meunier,Thanks for your straightforward comments and constructive suggestions on our recent study on dual-beam FT-IR spectroscopy published in Chin. J. Catal., 2017, 38, 13.19. We are glad to reply your questions and to give some supplementary remarks concerning the dual beam FT-IR spectrometer, its usage and application progress.     

Charge-remote fragmentation in a hybrid (BEqQ) mass spectrometer to determine isotopic purity in selectively polydeuterated surfactants

The combination of fast atom bombardment with charge-remote fragmentation using a hybrid (BEqQ) mass spectrometer was used successfully to assess and localize the extent of selective deuterium isotope labeling of tetradecyItrimethylammonium bromides. Spectral details reveal a new reaction that can give rise to ions isobaric with those formed by chargeremote fragmentation.     

质谱在线连续检测系统的建立及应用实例

设计和建立了一种质谱在线连续检测系统。该系统响应迅速,操作灵活。可直接与反应系统或与色谱等联机使用,对所有的气相反应和有可挥发组分的液相反应进行在线检测。在ＺｒＯ２－Ａ１２Ｏ３上进行了ＮＨ３吸脱附和ＣＯ脉冲反应的研究,获得了重现性很好的结果。     

Magnetic molecularly imprinted polymers for the determination of β‐agonist residues in milk by ultra high performance liquid chromatography with tandem mass spectrometry

A simple, accurate, and highly sensitive analytical method was developed in this study for the determination of nine β‐agonists in milk. In this method, a new magnetic adsorbent of molecularly imprinted polymers/magnetic nanoparticles prepared by simple physical blending was adopted, which enabled magnetic solid‐phase extraction. Thus, the resultant material can be separated from the solvent rapidly and conveniently by a magnet. Two kinds of molecularly imprinted polymer/magnetic nanoparticles materials were fabricated, and the characteristics of materials such as the ratio, pH, amount, desorption, and regeneration were investigated. The analytes were quantified by ultra high performance liquid chromatography coupled to an electrospray ionization tandem mass spectrometer operating in multiple reaction monitoring modes. The detection limit of the method was 0.003–0.3 μg/L, and the detection capability was 0.01–0.3 μg/L. The recoveries of these compounds were 65.7–114% at three spiked levels. Reproducibility represented by relative standard deviation was 11.2% or less. The method was successfully applied to the screening of real samples obtained from local markets and confirmation of the suspected target analytes.     

Real time monitoring of accelerated chemical reactions by ultrasonication‐assisted spray ionization mass spectrometry

Ultrasonication has been used to accelerate chemical reactions. It would be ideal if ultrasonication‐assisted chemical reactions could be monitored by suitable detection tools such as mass spectrometry in real time. It would be helpful to clarify reaction intermediates/products and to have a better understanding of reaction mechanism. In this work, we developed a system for ultrasonication‐assisted spray ionization mass spectrometry (UASI–MS) with an ~1.7 MHz ultrasonic transducer to monitor chemical reactions in real time. We demonstrated that simply depositing a sample solution on the MHz‐based ultrasonic transducer, which was placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Singly and multiply charged ions from small and large molecules, respectively, can be observed in the UASI mass spectra. Furthermore, the ultrasonic transducer used in the UASI setup accelerates the chemical reactions while being monitored via UASI–MS. The feasibility of using this approach for real‐time acceleration/monitoring of chemical reactions was demonstrated. The reactions of Girard T reagent and hydroxylamine with steroids were used as the model reactions. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions are readily generated and instantaneously monitored using MS within 1 s. Additionally, we also showed the possibility of using this reactive UASI–MS approach to assist the confirmation of trace steroids from complex urine samples by monitoring the generation of the product ions. Copyright © 2014 John Wiley & Sons, Ltd.     

负载于二氧化硅上的小尺寸氧化亚铜物种促进丙烯选择性氧化生成丙烯醛

氧化物负载的含铜材料是丙烯选择性氧化制备丙烯醛的理想催化剂,一直以来都受到人们的广泛关注.然而,对于该催化体系的结构与性能之间的关系仍不是很清楚.因此,我们以碳酸钠为沉淀剂,通过沉积沉淀法将铜负载于高比表面的二氧化硅载体上,从而得到了均匀分散且小尺寸的Cu/SiO2催化剂.另外,采用浸渍法制得了相同负载量的分散不均匀、大尺寸的Cu/SiO2催化剂.丙烯选择性氧化反应活性测试发现,沉积沉淀法制备的催化剂比浸渍法制备的更有利于丙烯醛的生成,表现出了优异的催化性能:在300℃反应时,丙烯的转化率达到25.5%,丙烯醛的选择性达到66.8%,对应的丙烯醛的生成速率高达10.5 mmol·h^-1·gcat.^-1或111.2 mmol·h^-1·gCu^-1,远远超出了浸渍法制备的催化剂性能(1.7 mmol·h^-1·gcat.^-1或17.2mmol·h^-1·gCu^-1)和文献中报道的结果.结合高角度环形暗场扫描透射电子显微镜(HAADF-STEM)和X射线吸收精细结构(XAFS)技术,对沉积沉淀法制备的催化剂进行表征,发现在反应后铜物种的结构发生了明显的变化,由小尺寸的氧化铜(CuO)团簇转变为氧化亚铜(Cu2O)团簇,并且铜物种的尺寸没有明显的增大.为了进一步探索铜物种在预处理(氢气还原)以及催化反应时(丙烯+氧气)的结构变化,对不同方法合成的两种催化剂进行了原位X射线粉末衍射测试,发现不同尺寸的铜物种在还原和反应时都经历了从氧化铜(CuO)变为金属Cu再到Cu2O的结构变化,并且Cu2O在320 min的反应过程中可以稳定存在,说明它是该催化反应的活性物种.另外,通过原位双光束傅里叶变换红外光谱追踪反应时气体分子在催化剂表面的吸脱附状态,发现丙烯可以有效地吸附在小尺寸Cu/SiO2催化剂表面,随着Cu2O的形成,检测到了烯丙基中间体(CH2=CHCH2*)的产生,该物种可以与邻近Cu2O上的一个氧发生反应,从而生成丙烯醛,因此结合N2O滴定实验,我们可认为,高度分散的小尺寸的Cu2O物种是丙烯进行高效选择性氧化反应生成丙烯醛的活性物种.     

乙苯光氧化产生二次有机气溶胶的化学成分及反应机理分析

在自制的烟雾腔内,研究羟基自由基(OH·)启动的乙苯的光氧化反应和一系列后续反应,产生了二次有机气溶胶. 采用空气动力学直径粒谱分析仪分析了气溶胶粒子的尺寸分布;并用自制的气溶胶飞行时间质谱仪快速、实时地测量了单个二次有机气溶胶粒子的分子组分. 初步探讨了这些组分的可能反应机理.     

Combined time- and space-resolved Raman spectrometer for the non-invasive depth profiling of chemical hazards

A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances under both the lab and the field environments. The system operating principles and performance are discussed along with its advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide a functional platform for in-line or in-field sensing of chemical substances.     

Determination of Rutin with UV-Vis Spectrophotometric and Laser-Induced Fluorimetric Detections Using a Non-Scanning Spectrometer

This study presents a linear charge-coupled device (CCD) spectrometer and its application to quantitative determination of rutin with UV-Vis spectrophotometry and fluorimetry detections. The spectrometer can obtain spectrum with the range of 271.44 nm from one exposure and the 1.7 nm resolution. With the same spectrometer, the determination of rutin in rutin tablet was successfully studied by measuring the absorption and laser-induced fluorescence emission. The data shows that there is no significant difference for determining rutin between the two methods. The result implies that the spectrometer, which realizes two different analytical methods, can be widely used in trace analysis.     

Rheological and thermal behaviours of a hyperbranched polycarbosilane

A hyperbranched polymer, a precursor of silicon carbide (SiC), was successfully synthesized using a hydrosilylation reaction with Karstedt's catalyst. This reaction was optimized with the use of a rheometer coupled with an infrared spectrometer. The polymeric precursor was characterized using NMR and Fourier transform infrared spectroscopies, and dynamic rheology. The polymerization reaction was followed in situ by combined rheological and infrared measurements, indicating a gel‐like behaviour for alkene conversions higher than 0.55. Overall second‐order kinetics was determined for the hydrosilylation reaction. Pyrolysis at 1400 °C led to porous materials with β‐SiC and free carbon.