分子筛催化材料.pptx

1、分子筛催化材料设计与制备,点击添加文本,点击添加文本,点击添加文本,点击添加文本,Background,Definition,Molecular sieve is a kind of material has a uniform pore size, which is equivalent to the average size of the molecule.,Development history,In 1756, people first discovered natural zeolites. In 19th century, people had a further understa

2、nding of the microporous properties, adsorption and ion exchange. In 1940s, zeolite chemist led by Barrer R M firstly synthesis low silica alumina ratio of zeolite molecular sieve.,Development history,Classification,Application,Main properties Adsorption performance Ion exchange performance Catalyti

3、c performance,Main application areas Petroleum processing Petroleum chemical industry Fine chemical Daily chemical industry,Prospects,FCC: Exploit new zeolites similar to ZSM-5 with high selectivity towards produce light olefins HDC: Exploit prolific middle distillates zeolites Aliphatic alkylation

4、Isomerization of alkanes Other varieties development,Structure,TO4 tetrahedron TO4 tetrahedron share one oxygen vertex,Primary structural units,Molecular sieve is composed of three-dimensional four connecting frame by the shared vertex of the TO4 tetrahedron. T usually refers to Si, Al, or P. In rar

5、e cases T refers to B, Ga, Be and so on.,Structure,Aluminosilicate molecular sieve consisted of SiO4 and AlO4 tetrahedron contains backbone anion, the negatively charge of backbone are balanced with additional cations. Aluminosilicate molecular sieves chemistry general formula is Ax/n(SiO2)(AlO2)xmH

6、2O.,Structure,Secondary structural units,The backbone of molecular sieve could be seen as composed of finite element unit or infinite element unit. The picture shows 18 finite element units of tetrahedra backbone.,Structure,Characteristic cage type structure unit,Some characteristics of cage type st

7、ructural units are existed in characteristic cage type structure unit.,Cage type structure unit in molecular sieve backbone,Structure,Features of the chain and layered structure units,In the skeleton structure of molecular sieve, we can find some of the features of the chain structure unit.,Structur

8、e,Features of the chain and layered structure units,Structure of molecular sieve can also be described by two-dimensional three connected network layer. The skeleton structure of three-dimensional four connected could be seen as parallel accumulation two-dimensional three connected layer interconnec

9、ted by upper and lower orientation.,Several common two-dimensional three connected network layer,Characterization,Characterization,The chemical and physical properties of molecular sieves are closely related to the structure of the materials. Scientists studied in synthesis, modification and applica

10、tion of molecular sieve need detailed structure and performance knowledge to achieve their objectives. Therefore, in the study of molecular sieve, the characterization of the structure and performance is very important.,Characterization,Characterization,Diffraction: The most effective method to stud

11、y the long history structure of crystal materials. Types of radiation sources widely used in structure research conclude electron diffraction, diffraction, X ray diffraction and synchrotron radiation sources. Spectrum: Spectroscopic technique is the study of atomic and molecular physics process, whi

12、ch is based on atomic or molecular absorption, emission and scattering of electromagnetic waves. For example IR, Raman spectroscopy ,EELS,IETS,INSS.,Characterization,Microscopic technique: using optical devices to obtain an enlarged image of an object. For example SEM,TEM,STM. Adsorption, desorption

13、, thermal analysis technique: using adsorption and diffusion experiments, program desorption, , thermal analysis, catalytic reaction test of probe molecules to get surface structure information indirectly.,Characterization,Property characterization,Backbone parts: Structure Chemical composition Impu

14、rity Structural defects,Cavity parts: Pore volume Specific surface area Pore size distribution Cavity shape,Bragg Equation,When X-ray (Wavelength ) incident to any lattice plane, In the lattice plane, each lattice point incident wave scattering angle and the reflection angle is equal, the X-ray, X-r

15、ay and anti surface normals in the same plane.When,The lattice plane wave scattering optical path difference is an integer multiple of the wavelength, They have the same phase, the scattering wave superposition reinforce each other, resulting in diffraction.,XRD,XRD,The basic structure diagram of X

16、ray diffraction,A. Aiming device B. Sample C. Slit D. Monochromator E. Detector X. X ray source,XRD,Adsorption,Many properties of cavities are determined by physical adsorption. N2,Ar or O2 was always used as adsorbate so that we can measure pore volume, specific surface area, pore size distribution

17、 of porous material.,点击添加文本,点击添加文本,点击添加文本,点击添加文本,mesoporous materials,type,microporous materials,ultra porous materials,type ,type ,macroporous material,type ,Adsorption,Adsorption,Adsorption equilibrium isotherm,Classification of adsorption isotherms by IUPAC,Adsorption,Hysteresis,If the adsorption

18、-desorption is not completely reversible, the adsorption-desorption isotherms are not coincident. This phenomenon mainly occurred in type adsorption equilibrium isotherm.,Adsorption,Four kinds of hysteresis loop,H1: The hysteresis loop is very steep and almost parallel.Mainly formed by uniform size

19、and shape hole. H2: The adsorption branch of the adsorption isotherm is gradually increasing due to the phenomenon of capillary condensation, the desorption branches suddenly fell under a relatively low relative pressure at the same time. Desorption is suddenly happened in adsorbates,Adsorption,Four

20、 kinds of hysteresis loop,H3H4: Mainly attributed to slit channel.,Capillary condensation of cylindrical pores,Adsorption Desorption,Electron microscopic technique,Optical microscope: The magnification of optical microscopy is several thousand times. Because of the limitation of light wave, its reso

21、lution is not less than 0.2m. Electron microscope: Magnification of the electron microscope can reach a million. The smallest details can be resolved are several .,Electron microscopic technique,Scanning electron microscope,The principle of SEM is that the electronic line is illuminated in the sampl

22、e, and the signal is collected from the surface of the bulk sample. SEM can accurately reflect the morphology of the surface of the specimen. Image has a three-dimensional sense.,Electron microscopic technique,Scanning electron microscope,Observe the structure of the surface of the sample directly.

23、The size of sample can be large as 120mm80mm50mm. Sample preparation process is simple, need not cut into thin slices. Sample can be used for three degrees of space in the sample room for translation and rotation so that we can observe the sample from various angles. Depth of field is large. Image h

24、as a three-dimensional sense,Characteristic,Electron microscopic technique,Scanning electron microscope,The image of a wide range of magnification, resolution is relatively high. It can expand to a dozen times to hundreds of thousands of times. Resolution is between optical microscope and transmissi

25、on electron microscope, about 3nm. Electron beam can little damage and contamination the sample. During the observation of morphology, it can also be used to analyze the other signals from the sample to make the micro area composition analysis.,Characteristic,Electron microscopic technique,Transmiss

26、ion electron microscope,TEM includes lighting system, imaging system, and observation-photo studio. TEM can clearly display the local structure of the crystal. The pore structure of molecular sieve can be observed directly. TEM was used to observe the morphology, size, particle size, particle size d

27、istribution of the powder and so on.,Electron microscopic technique,Transmission electron microscope,Electron diffraction analysis Convergent beam electron diffraction analysis Transmission electron image analysis High resolution image analysis Scanning and energy spectrum analysis system Micro diff

28、raction and micro diffraction analysis,Application,Electron microscopic technique,Other methods of electron microscopy,FEM,Electron probe,FIM,ESCA,LEED,AES,Nuclear magnetic resonance,A tool for qualitative analysis of the composition and structure of organic matter and inorganic matter. An effective

29、 method to analyze and identify the microporous and mesoporous materials. By the application of technologies like cross palarization, magic angle spinning, total sideband suppression and dipolar diphasing, quantitative function can be realized.,Infrared spectrum,Infrared spectrum can be used to char

30、acterize the chemical bonds and to characterize the molecular structure. Infrared spectrum has the advantages of less sample, simple sample processing, quick measurement, convenient operation and so on.,Infrared spectrum,Application in Molecular sieve: Identification of molecular sieve framework Com

31、position analysis of frame elements Cation distribution Surface hydroxyl structure Surface acidity Catalytic performance Object structure of molecular sieve,Thermal analysis,Thermal analysis is the study of material in the process of heating or cooling. This analysis have the advantages of sensitive

32、, fast and accurate. The most of applications are the combination of TGA and DTA. The application of thermal analysis technique in molecular sieve analysis includes determination of the content of molecular sieve, the content of organic template, thermal stability, desorption mechanism and so on.,Th

33、ermal analysis,Thermal analysis technique,Chemical composition and macroscopic properties,ICP: ICP has the characteristics of high precision, low matrix interference, and wide range of calibration curve. It is widely used in the qualitative and quantitative analysis of inorganic elements. It is wide

34、ly used in the qualitative and quantitative analysis of inorganic elements. AAS: The characteristics of high sensitivity, good selectivity, and determination of elements. XRF: The atom is excited by high energy radiation, and its inner electron level transition, emitting characteristic X ray. It can

35、 measure some non metal and make the sample simple.,Methods,Hydrothermal synthesis,Molecular sieve is a kind of compounds with microporous skeletal structure by burning or chemical treatment, extraction, microwave, removing template agent etc; or through the process of backbone modification, ion exc

36、hange, isomorphous replacement with the surface and pore modification secondary synthesis method to obtain a specific pore structure and properties of material.,Hydrothermal synthesis,Hydrothermal and solvent thermal synthesis is the method of a solvent in a certain temperature(100-1000) and pressur

37、e(1-100MPa) conditions occurring a specific chemical reaction.,Synthetic reactions are generally performed in a particular type of closed vessel or autoclave. The reaction is in subcritical and supercritical conditions.,Hydrothermal synthesis,Two main features,The research system is in non ideal and

38、 non equilibrium state so that we can use non equilibrium thermodynamics to solve the synthesis of chemical problems. Hydrothermal and solvent thermal chemical properties are operable and variable.,Hydrothermal synthesis,Five main functions,Due to the change of the reaction properties of the reactan

39、ts and the increase of the activity and the effect of the product. Hydrothermal and solvent thermal methods may be used in the chemical reactions, which are difficult to be used in the synthesis of solid state reaction. The special redox intermediate state, metastable phase and some special phase ca

40、n be easily generated in the hydrothermal and solvent thermal conditions. It can make the substance which has low melting point, high vapor pressure and can not be generated in the melt as well as high temperature decomposition phase crystallize in the hydrothermal and solvent under low temperature

41、conditions.,Hydrothermal synthesis,Five main functions,The reaction conditions like low temperature, pressure and liquid phase of hydrothermal and solvothermal are favorable to the growth of the less defects, the control orientation, the perfect crystal and easy to control the size and morphology pr

42、oducts. Due to the ease of the environmental atmosphere and regulating the oxidation and reduction potential of related materials in the hydrothermal and solvent thermal conditions, the formation of some special low valence state, intermediate valence state and special valence compound can be easily

43、 completed, and can be uniformly doped.,Hydrothermal synthesis,Basic types,Synthetic reaction Crystallization reaction Hydrolysis reaction Single crystal cultivation Heat treatment reaction Transfer reaction,Ion exchange reaction Shrinkage reaction Extraction reaction Oxidation reduction reaction Pr

44、ecipitation reaction Sintering reaction Hydrothermal hot pressing reaction,Hydrothermal synthesis technique,Reaction vessel, reaction control system, water and solvent thermal synthesis program and in-situ characterization technique.,Synthetic route,Route: Generation of hydrated gel and crystallizat

45、ion of hydrated gel,Crystallization,Reactant,Silicon source, aluminum source, metal ion, alkali, other mineral agent, water.,Silicon source: Na2O xSiO2,Na2SiO3 9H2O, silica gel, fumed silica, TEOS, TMeOS,Aluminum source: NaAlO2, AlOOH, Al(OH3), Al(i-OC3H7)3, Al(NO3)39H2O, metal aluminum,Silica-Alumi

46、na ratio,The structure and composition of the final product in the reaction materials are important to the final product. In most cases, molecular sieves of low silicon-aluminum ratio like LTA, SOD, KH, KJ, etc. have been crystallized by high pH value, low silicon-aluminum initial materials. High si

47、lica molecular sieve like MOR, BEA have been crystallized by low pH value, high silicon-aluminum initial materials.,Alkalinity,The synthesis of molecular sieves is carried out under the condition of alkaline. Improving the alkalinity of the synthetic system can conducive to the formation of rich alu

48、minum molecular sieve. When the concentration of alkali concentration increases, the product size becomes smaller and the size distribution becomes narrow.,Ageing,Mix the initial material until the beginning of crystallization. This period is called ageing. The main existence in the synthesis system

49、 is silica-alumina gel and corresponding gel liquid phase. Control the reaction conditions like temperature and time are advantage to the transformation and nucleation of gels.,Crystallization and ageing temperature,The temperature change of crystallization and ageing reaction can trigger the transf

50、ormation of the polymerizing conditions, polymerization, gel formation and dissolution in silicon ions and aluminium ions and polymerization of gels and gels between liquid.,Template removal,High temperature combustion method Chemical reaction method Solvent extraction method,Hydrothermal synthesis

51、method can be used to synthesis a specific backbone, component elements and the structure of the molecular sieve. In addition to part of the zeolites, most of the backbones of the molecular sieve contain organic molecules used as structure directing agent.,Three main methods,Secondary synthesis meth

52、ods,Secondary synthesis: Modification and further processing of molecular sieve structure,Properties and functions of molecular sieve depends on its backbone structure and counterions.,Secondary synthesis methods,Cation exchange,ZA,ZB is valence state charge of exchangeable cation A and B. (M),(S) i

53、s zeolite facies and solution facies respectively.,Reaction can be expressed as,Secondary synthesis methods,Aluminum removal,Dealuminzation ultra stabilization through thermal treatment and hydrothermal treatment route. Chemical dehydration route. SiCl4 route is the most familiar. Optimization group

54、ing of thermal treatment and chemical dehydration.,Secondary synthesis methods,Pore and surface modification,Cation exchange method Channel modification Outer surface modification,Instances,LTA,Dissolve 0.723g NaOH into 80mL deionized water, stirring for 10-20min,mixing until full dissolution. Divid

55、e the solution into two parts, placed in two polypropylene bottles. Add 8.258g Na2Al2O4 into one of the NaOH solutions(a), stirring for 10-20min until full dissolution. Cover the bottle until clarification. Add 15.48g Na2SiO3 into another NaOH solution(b), stirring for 10-20min until full dissolution, Cover the bottle until clarification. Rapidly add solution b to solution a until thick gels formed and carry