气体吸附理论及应用概论.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,2003,Quantachrome Instruments,*,多孔物质,气体吸附,理论及应用概论,内容简介,公司介绍,物理吸附和化学吸附的基本理论和方法,各种吸附仪的特点和选择原则,2003,Quantachrome Instruments,颗粒特性分析测定仪器,英国马尔文公司,激光衍射粒度分析仪,0.02 3500 微米,500/1000,Hz,扫描速率,激光动态光散射分析仪,1 5000纳米/,ZETA,电位,干粉/喷雾粒度分析仪,在线粒度分析仪,高浓度超声粒度分析仪,绝对分子量分布测定仪,100 1,e 12 Daltons,美国康塔公司,全自动比表面及孔隙度分析仪,(分析站数可选 1/2/3/6),0.0005,m2/g,3.5 5000,埃,压汞仪,3.6纳米 426 微米孔径,化学吸附仪,(,TPR/TPD),流动法快速比表面测定仪,全自动真密度计,自动堆密度分析仪,2003,Quantachrome Instruments,粉体比表面和孔隙度分析,_,经典文献来自,QUANTACHROME,2003,Quantachrome Instruments,粉体比表面和孔隙度分析,_,经典文献来自,QUANTACHROME,2004,年出版发行,2003,Quantachrome Instruments,QUANTACHROME,-,1968,年由纽约长岛大学化学家,Dr.S.Lowell,教授建立,-著名的当代颗粒技术开创者，革新了比表面和孔隙度测量 技术并设计了相应的仪器-康塔(,Quantachrome),的仪器不仅受到科学界的青睐,而且已经向全世界的工业实验室发展。-被公认是对样品权威分析的优秀供应商,它可为实验室提供全套装备及完美的粉体分析技术,及最佳的性能价格比。-康塔(,Quantachrome),公司,开发粉体及多孔材料特性仪器的世界领导者,向中国用户提供全面服务。,2003,Quantachrome Instruments,Founded 1968 by Dr.S.Lowell,Professor of Physical Chemistry,Long Island University,New York,First product:,Quantasorb,Surface Area Analyzer based of dynamic flow method.,Competitor:In 1968 Micromeritics(founded 1963)was producing manually operated vacuum volumetric instrument which produced data very slowly(many hours).,Quantasorb,reduced surface area analysis time to as little as 30 minutes enabling measurement to be more effectively used in quality and process control labs.,History of Innovative Developments for characterization of powders and porous solids,1972,Monosorb,first dynamic flow,single point surface area analyzer with direct surface area display,1972,Stereopycnometer,first commercially available gas expansion,pycnometer,1978,Autoscan,Mercury,Porosimeter,first introduction of continuous scanning/pressurization,1982,Autosorb-6 first six-port,high throughput gas sorption analyzer simultaneous and independent analysis of six samples,1990,NOVA Series first high speed surface area analyzers that could perform measurements without helium void volume determination,2001,NLDFT for zeolite and,microporous,silica first full library of advanced micropore models based on statistical mechanics for advanced micropore size measurements,2003,Hydrosorb first,high speed,vacuum volumetric water sorption analyzer reduced analysis times from days to hours!,2004,Quadrasorb,first,benchtop,economically priced multi-station gas sorption analyzer with independent stations.,2003,Quantachrome Instruments,Quantachromes Headquarters,Boynton Beach,Florida,USA,Quantachrome Corporation is dedicated to providing the highest quality particle characterization instrumentation while maintaining responsive customer service and support.,Quantachromes Mission,Quantachrome People,Dr.Martin Thomas,Director,Applied Technology,has more than 20 years professional experience in the field of particle characterization,13 with Quantachrome.He gained his PhD from the University of Birminghams School of Chemistry(UK)as he did his Masters degree in Analytical Chemistry.His industrial experience prior to joining Quantachrome Instruments in 1991 was at Cookson Groups central research lab and,ICIs,Catalysis Research Center(now Johnson Matthey Catalysts).Dr Thomas has had published 7 peer-reviewed papers and one US patent,plus a number of other articles and posters.He is a joint author of a new book(Characterization of Porous Solids and Powders)to be published August 2004.Dr Thomas is active on a number of ASTM committees and lectures occasionally for the Center for Professional Advancement.,Key Contacts for International Distributor Support:,2003,Quantachrome Instruments,Quantachrome People,Dr.Matthias Thommes,Director,Applied Science,:,Doctoral Thesis in Physical Chemistry at Ruhr-University Bochum(1989-1991)and Technical University Berlin,Germany (1992/93).More than 30 publications(and invited review-articles)in ref.journals such as,Journal of Physical Chemistry B,Langmuir,Journal of Chemical Physics,Applied Surface Science,Carbon,Studies in Surface Science and Catalysis et.,Since 2001,more than,33 presentations,(at least 28 oral presentations)and,invited seminars,at international conferences,symposia and universities all over the world,Professional Affiliations:,International Adsorption Society,American Institute of Chemical Engineers,Amercian,Chemical Society,American Society for Testing and Materials(ASTM),Member of the US-delegation,to work in the,ISO(International,Standard Organization)Committee,2003,Quantachrome Instruments,Quantachrome People,Mr.Jeff Dixon,International Sales Manager,Over 10 years professional experience in particle/porous materials characterization.Joined Quantachrome in October 2003 after 8+years with PMI(also in porous materials characterization),Involved in the design and engineering of new porous materials characterization technologies/instruments including gas flow techniques,diffusion,permeametry,water vapor sorption,water intrusion,porosimetry,membrane characterization.,At Quantachrome:responsible for International sales network,application support,new product design and engineering.,Professional Affiliations:,ASTM,EDANA,TAPPI,INDA(papers,nonwovens).,2003,Quantachrome Instruments,Quantachrome People,Dr.Jacek Jagiello,Manager,Application Support and Training,.,Adsorption specialist with special interest in understanding and characterization of activated carbons.Doctorate from M.Curie-,Sklodowska,University,Lublin,Poland(1994.Postdoctoral research associate at CNRS,Mulhouse,France from 1998 to 1990.Postdoctoral research associate at Syracuse University,New York from 1990-1996.From 1996-2000 in the Carbon,Research Group of Westvaco Corporation(Charleston,South Carolina),Author and co-author of more than 80 scientific publications with numerous international presentations and four US patents.,2003,Quantachrome Instruments,Quantachrome People,Mark Contessa,Service Manager,Mark began his career with a 4 year term in the US Navy where he gained experience in electronics.,Mark worked for 10 years for a major US defense contractor.,Joined Quantachrome over 12 years ago,and has held the position of Service Manager.,Mark is responsible for all areas of service,and manages a team of field service engineers.,Mark has traveled extensively,including 2 trips to China.,2003,Quantachrome Instruments,Quantachrome,Firsts,Quantachrome has several achievements which are:,a)Development of the,Monosorb,the first single-point,dynamic flow B.E.T.surface area instrument,b),Development of a“continuous scan porosimetry”,utilized in the,Poremaster,pore size analyzers,c)Development of the first“commercially viable”,gas,pycnometers,d)Development of the,Autosorb-6,the first multi-station,surface area and pore size analyzer with the ability,to conduct simultaneous and independent,measurements,2003,Quantachrome Instruments,Development of the first“commercially viable”gas-expansion pycnometers!,A Quantachrome,First!,Development of the,Monosorb,the first single-point,dynamic-flow BET instrument with direct surface area readout!,A Quantachrome,First!,Development of the patented continuous-scanning mercury porosimeters utilized in the Quantachrome,PoreMaster,pore size analyzers!,A Quantachrome,First!,Development of the,Autosorb-6,the first multi-station surface area and pore size analyzer with the ability to conduct independent and simultaneous measurements!,A Quantachrome,First!,NOVA,e,系列,全自动,比表面及孔隙度分析仪,时尚流线型外观设计,操作空间加大,歧管死体积减小1.7,ml,杜瓦工作时间延至30小时/次,4个脱气站和4个分析站，可同时进行8个样品的处理和分析,符合美国,FDA,21 CFR Part 11,标准,2003,Quantachrome Instruments,QUADRASORB,SI,全自动,4,站比表面和孔隙度分析仪,2003,Quantachrome Instruments,Autosorb-1MP,微孔型,高端比表面和孔隙度分析仪,具有五个压力传感器和一个液位传感器,极限真空达,10,-10,mmHg,BET,比表面,微孔,介孔和大孔的孔径分布,微孔体积和面积,氪吸附测超低比表面,CO2 and H2,吸附研究,蒸汽吸附,2003,Quantachrome Instruments,Rifflers,Rotary Micro Riffler,Instruments for Representative Sampling,Spinning,rifflers,for accurate representative sampling of powders and granular material.,Operator selectable feed rate and collector rotation speed.,Maximum capacity:,Rotary Micro Riffler/120 cc,Sieving Riffler/2500 cc,Sieving Riffler,多孔材料的物理吸附理论分析,背景知识,吸附理论,孔隙度测量,评注及结论,2003,Quantachrome Instruments,多孔材料的应用,2003,Quantachrome Instruments,孔隙度,2003,Quantachrome Instruments,什么是表面积,?,Surface Area what is it?,“,表面是固体与周围环境,特别是液体和气体相互影响的部分,;,表面的大小即表面积,.”,“Surface Area is the means through which a solid interacts with its surroundings,especially liquids and gases.”,表面积可以通过颗粒分割,(,减小粒度,),和生成孔隙而增加,.,Surface area is,created,by division of particles(size reduction)and the generation of porosity.,表面积可以通过烧结,熔融和生长而减小,.,Surface area is,destroyed,by sintering(exceeding T,g,),melting and,Ostwald,ripening.,2003,Quantachrome Instruments,为什么表面积如此重要,?,Surface Area Importance?,请记住,:,表面积是固体与周围环境,特别是液体和气体相互作用的手段和途径,.,Remember that surface area is the means through which a solid interacts with its surroundings.,考虑下列三种作用,:,Consider the following three interactions:,固体,-,固体,:,自动粘结,流动性,(,流沙,),压塑性,Solid-Solid:auto,hesiveness,(cohesiveness),eg,flow,compactibility,etc.,固体,-,液体,:,浸润,非浸润,吸附能力等,Solid-Liquid:wetting,non-wetting,adsorption capacity etc.,固体,-,气体,:,吸附,催化等,Solid gas:adsorption,catalysis,etc.,2003,Quantachrome Instruments,孔的类型,交联孔,(,开孔,),闭孔,盲孔,(,开孔,),通孔,(,开孔,),2003,Quantachrome Instruments,孔形的分类,筒形孔,筒形孔,锥形孔,裂隙孔,球形孔,(,墨水瓶孔,),2003,Quantachrome Instruments,孔径的分类,(IUPAC Standard),2003,Quantachrome Instruments,表面积测定方法,Suitable methods of determination,气体吸附法是测量所有的表面,包括不规则的表面和开孔内部的面积,.,Gas adsorption allows probing of entire surface including irregularities and pore interiors.,吸附量是温度,压力和亲和力或作用能的函数,.,The amount adsorbed is a function of temperature,pressure and the strength of attraction or interaction potential.,物理吸附一般是弱的可逆吸附,.,固体必须被冷却,并且确定一种方法从可能的单分子覆盖中计算表面积,.,Physisorption is generally weak and reversible.The solid must be cooled and a method used to estimate the monolayer coverage from which surface area can be calculated.,2003,Quantachrome Instruments,孔隙度测定方法,-,气体吸附法,仅测量开孔,有效范围,:0.4-50nm,容易操作,成熟技术,2003,Quantachrome Instruments,孔隙度测定方法,-,压汞法,类似于气体吸附,仅测量开孔,有效范围,:3.6nm,容易操作,成熟技术,2003,Quantachrome Instruments,孔隙度测定方法,-,透射电镜,提供有关孔交联信息,如果材料含有有序孔,则可正确反映孔径,几乎不用于孔分析,2003,Quantachrome Instruments,孔隙度测定方法,-,扫描电镜,孔径,:5nm,几乎不用于孔分析,2003,Quantachrome Instruments,孔隙度测定方法,-,小角,X-,射线扫描法,任何孔径,用于开孔,+,闭孔的孔分析,2003,Quantachrome Instruments,孔隙度测定方法,-,小角中子散射法,(SAN),任何孔径,用于开孔,+,闭孔的孔分析,价格昂贵,2003,Quantachrome Instruments,吸 附 原 理,2003,Quantachrome Instruments,固体材料对气体的吸附现象,1、,化学吸附-是气体分子与材料表面的化学键合过程,只发生单层吸附,选择性吸附(特定气体主要,H,2,CO,O,2,对体系中各组分的特定吸附),2、,物理吸附-是由范得华力引起的气体分子在固体表面及孔隙中的冷凝过程,可发生单层吸附,多层吸附,非选择性吸附,气体分子在固体表面的吸附机理极为复杂，其中包含化学吸附和物理吸附,2003,Quantachrome Instruments,物理吸附和化学吸附的比较,Copyright Quantachrome Corporation 2000.All rights reserved.,气体吸附过程静态描述,吸附物,吸附物,多层饱和吸附,随机性非饱和吸附,单层饱和吸附,可计算比表面积,可计算总孔容积,2003,Quantachrome Instruments,气体吸附,通过固体表面上气体吸附量多少来计算粉体或多孔固体的比表面积,比表面积的测量包括能够到达表面的全部气体，无论外部还是内部。,Copyright Quantachrome Corporation 2000.All rights reserved.,气体吸附,一般而言，在范德华力作用下，固体吸附气体是弱键作用。,为了使足够气体吸附到固体表面，测量时固体必须冷却，通常冷却到吸附气体的沸点。,通常氮气作为被吸附物，因此固体被冷却到液氮温度,(77.35,K),Copyright Quantachrome Corporation 2000.All rights reserved.,气体吸附过程,4),Copyright Quantachrome Corporation 2000.All rights reserved.,吸附等温线,在密封容器中，某种材料在特定温度下对气体的吸附量与吸附平衡后的压力有其特殊的对应关系,III,0,P/P,0,1.0,IV,0,P/P,0,1.0,V,0,P/P,0,1.0,I,I,0,P/P,0,1.0,I,II,V,V,V,V,0,P/P,0,1.0,V,2003,Quantachrome Instruments,Very Low pressure behavior(micropore filling),2003,Quantachrome Instruments,Low pressure behavior(monolayer),The“knee”,2003,Quantachrome Instruments,Medium pressure behavior(multilayer),2003,Quantachrome Instruments,High pressure behavior(capillary condensation),2003,Quantachrome Instruments,Schematic illustration of the sorption,pore condensation and hysteresis behavior of a fluid in a single cylindrical mesopore,2003,Quantachrome Instruments,具有微孔的氮吸附等温线,2003,Quantachrome Instruments,由国际纯粹与应用化学联合会,（,IUPAC,）,提出的物理吸附等温线分类,2003,Quantachrome Instruments,I,型等温线的特点,在低相对压力区域，气体吸附量有一个快速增长。这归因于微孔填充。,随后的水平或近水平平台表明，微孔已经充满，没有或几乎没有进一步的吸附发生。,达到饱和压力时，可能出现吸附质凝聚。,外表面相对较小的微孔固体，如活性炭、分子筛沸石和某些多孔氧化物，表现出这种等温线。,2003,Quantachrome Instruments,II,型和,III,等温线的特点,II,型等温线一般由非孔或大孔固体产生。,B,点通常被作为单层吸附容量结束的标志。,III,型等温线以向相对压力轴凸出为特征。这种等温线在,非孔或大孔,固体上发生弱的气固相互作用时出现，而且,不常见。,2003,Quantachrome Instruments,IV,型等温线的特点,IV,型等温线由介孔固体产生。,典型特征是等温线的吸附曲线与脱附曲线不一致，可以观察到迟滞回线。,在,p,/,p,0,值较高的区域可观察到一个平台，有时以等温线的最终转而向上结束,(,不闭合,),。,2003,Quantachrome Instruments,V,和,VI,型等温线的特点,V,型等温线的特征是向相对压力轴凸起。,V,型等温线来源于微孔和介孔固体上的弱气固相互作用，而且相对不常见。,VI,型等温线以其吸附过程的台阶状特性而著称。这些台阶来源于均匀非孔表面的依次多层吸附。,这种等温线的完整形式，不能由液氮温度下的氮气吸附来获得。,2003,Quantachrome Instruments,迟滞回线类型,2003,Quantachrome Instruments,迟滞回线类型,按照,IUPAC,13.2,节中的约定，划分出了,4,种特征类型,H1,型迟滞回线可在孔径分布相对较窄的介孔材料，和尺寸较均匀的球形颗粒聚集体中观察到。,2003,Quantachrome Instruments,迟滞回线类型,按照,IUPAC,13.2,节中的约定，划分出了,4,种特征类型,H2,型迟滞回线由有些固体，如某些二氧化硅凝胶给出。其中孔径分布和孔形状可能不好确定，比如，孔径分布比,H1,型回线更宽。,2003,Quantachrome Instruments,迟滞回线类型,按照,IUPAC,13.2,节中的约定，划分出了,4,种特征类型,H3,型迟滞回线由片状颗粒材料，如粘土，或由裂隙孔材料给出，在较高相对压力区域没有表现出任何吸附限制。,2003,Quantachrome Instruments,迟滞回线类型,按照,IUPAC,13.2,节中的约定，划分出了,4,种特征类型,H4,型迟滞回线出现在含有狭窄的裂隙孔的固体中，如活性炭中见到，在较高相对压力区域也没有表现出吸附限制。,2003,Quantachrome Instruments,迟滞环与孔形的关系,2003,Quantachrome Instruments,气体吸附,可见,气体吸附量随着压力的升高而增加，但不是线性的。,如何测量,?,如果,气体充分的覆盖在固体表面(单层)的体积是已知的，就能够精确地计算出比表面积。,Copyright Quantachrome Corporation 2000.All rights reserved.,气体吸附分析仪,分析方法:,在等温条件下，通过测定不同压力下材料对气体的吸附量,获得等温吸附线，应用适当的数学模型推算材料的,比表面积,多孔材料的,孔容积,及,孔径分布,，多组分或载体催化剂的,活性组分分散度,表面积及孔径分布测量可采用多种不同方法，气体吸附法作为一种应用性最广、测量精度最高的方法被普遍接受,2003,Quantachrome Instruments,测量方法,流动法,把30%氮气(被吸附物)和,70%,氦气(载体,),的混合气体不断在样品上进行流动。,当样品冷却到液氮温度时，氮气被吸附，而氦气不被吸附。,吸附过程持续，直到氮气吸附量达到30%浓度。这时，吸附量接近于单层表面覆盖的体积。,Copyright Quantachrome Corporation 2000.All rights reserved.,流动法,Flow,通过用非吸附的氦气稀释氮气,(,吸附质,),获得,P/Po,.,Required P/Po is achieved by diluting nitrogen(adsorbate)with helium(non-adsorbing).,样品被冷却至液氮温度而引起吸附,.,The sample is cooled with liquid nitrogen,to cause adsorption.,吸附,(,及随后的脱附,),过程是由热导检测器监测的,.,The adsorption(and subsequent desorption)process is monitored using a thermal conductivity detector,.,2003,Quantachrome Instruments,动态流动法,Dynamic Flow,信号校正是通过将已知体积的纯氮气注入到气流中进行的,.,The signal is calibrated against a known volume of pure nitrogen injected into the gas stream.,该方法极其快速,特别适用于单点,BET,法对生产过程的监控,.,The method is extremely rapid and ideally suited to manufacturing processes using the single point method.,可用氪吸附作超低比表面,.,Very dilute concentration of krypton at liquid nitrogen temperature is used for extremely low surface areas,.,2003,Quantachrome Instruments,(,经典的,),真空,-,体积测定法,(Classical)Vacuum-Volumetric,需要在降低的温度下,由样品吸附吸附质作为纯吸附作用的函数,.,R,equires that adsorbate be adsorbed by the sample,at some reduced temperature,as a function of pressure of pure adsorptive,P/Po,值,(,相对压力,),是通过制造局部真空做到的,.,P/Po values are achieved by creating conditions of partial vacuum.,在吸附过程中由高精度压力传感器监测压力的改变,.,High precision and accurate pressure transducers monitor pressure changes due to the adsorption process.,2003,Quantachrome Instruments,测量方法,真空法,样品池抽真空,测量空体积,(,样品池空间),A),用氦气测量,B),存储器里存有的校对值,.,样品冷却到液氮温度，然后氮气注入到已知参考体积(歧管)的样品池。,由于氮气注入空体积而膨胀，导致压力下降，而氮气充满空体积时的压力下降是能够计算的。因此通过压力的下降来计算气体吸附量。,Copyright Quantachrome Corporation 2000.All rights reserved.,真空法,-,气体体积测量关键,样品的前处理,(,足够的真空脱气去除微