催化剂制备及表征课件：Chapter 1-catalysis and physical properties-20150317.ppt

1、Preparation & Characterization of CatalystState Key Laboratory for Heavy Oil ProcessingThe Key Laboratory of Catalysis, CNPCCollege of Chemical Engineering, CUPl sustainable mobility l the rational use of resourcesl quality of life and health protectionl environment protectionAll ProcessesCatalytic

2、ProcessesCatalyticProcesses85 %HeterogeneousCatalysts80 %Source: Winnacker, Kchler, Chemische Technik, Vol. 1, 2004BASF estimatesRole of Catalysis RefiningLiquid Fuel and ChemicalsCatalystCatalystCoupling化学工程学分析测试技术金属有机化学 配位化学表面科学无机材料固体化学物理化学催化催化传热传质 反应器设计 过程经济评价 工程放大技术 吸附、脱附 表面分析 催化晶面 结构模型催化剂表征原料、产

3、物分析催化剂载体助催化剂 配位催化 均相催化剂制金属离子的配位 反应热力学分析 反应动力学分析 表面现象物化分析汽油汽油柴油柴油芳香环环烷环烷基侧链硫193619421964196819761983活性白土活性提高2-3倍RON提高合成硅酸铝汽油收率增加7-10% 焦炭降低40%焦炭降低5-10%轻油收率增加3%机械强度提高3倍焦炭降低10-20%RON提高2个单位X，Y分子筛SiO2-Al2O3凝胶Y分子筛白土和粘结剂USY Preparation and characterization of a catalyst is crucial to innovate a novel cataly

4、st. Catalyst is usually not the same with other chemicals, especially pure chemicals. Catalyst usually bears complicated composition and structure, especially for heterogeneous catalyst. Know-how in catalyst preparation is key to develop optimum catalyst.1909年哈伯在实验室内成功研发了合成氨铁催化剂。经过三年的努力，在小试的基础上完成了工程

5、化放大，并由BASF建成了世界上第一个合成氨厂，日产30万吨。1913年投产，1914年达到设计水平。PreparationPhysical PropertiesCharacterizationDesignCharacters & RoleEvaluationCharacters of the catalyst Type of catalyst Properties of catalyst Component of catalyst Ostwald (德国）的观点 催化剂是一种能够改变化学反应的速度，而它本身又不参与最终产物的 物质。 （流行） IUPAC定义： 催化剂能够加速反应速率而不改变

6、反应的标准Gibbs自有焓变化。 国内新近定义 催化时加速反应速度、控制反应方向或产物构成，而不影响化学平衡的一类作用。起这种作用的物质称为催化剂，它不在主反应的化 学计量式中反映出来，即在反应中不被消耗。 Boudart (Nature,1994) A catalyst is a substance that brings about a chemical reaction by providing a cyclic path along which reactants become products, while the catalyst is recovered at the end o

7、f the cycle.Keck Professor of Chemical Engineering, EmeritusA catalyst is a substance that increases the rate at which a chemical reaction approaches equilibrium without itself becoming permanently involved in the reaction. Two words can sum up the role of the catalyst. Contact and mediumRecycle of

8、catalysis 参与化学反应 改变化学反应速度( ); 不改变化学反应平衡 ( ); 反应结束后状态与数量保持不变( ); 催化剂可以多次再生使用( ); 不介入化学计量反应式 (); 催化剂量明显少于反应物料量 ( ); 催化剂对反应应具有选择性 ( )。Selectivity to the Reaction Types非催化反应催化反应ABAB催化剂找到从反应物到产物的低能路径催化剂找到从反应物到产物的低能路径IntermediateReactantBy product EnergyProduct1. 改变反应历程；2. 降低活化能；3. 改变反应速度。分类方法 （1）根据化学键分类（

9、2）按元素周期律分类(3) 按催化剂组成及其使用功能的分按催化剂组成及其使用功能的分类类 Organization of Catalysis（4）按工艺与工程特点分类）按工艺与工程特点分类 Heterogeneous catalysis Enzyme catalysis Homogeneous catalysis Types of catalyst Heterogeneous catalyst Homogeneous catalyst Enzyme catalyst The reactants and catalyst exist in different phase. Most common

10、ly, solid catalysts are used with gaseous or liquid reactants, sometimes both. Interfacial phenomena become important. Diffusion, adsorption, desorption all play critical roles in establishing the rate. These additional steps become difficult to separate from surface reactions.Heterogeneous Catalyti

11、c Reaction Process Heterogeneous mechanism is difficult to investigated in the laboratory. Disappearance of reactants and appearance of products are easily followed, but important features such as the rates and energetic of adsorption, structure of active sites, the nature of active intermediates, r

12、equire separate experimentation using a constantly changing arsenal of techniques. Heterogeneous catalysts are convenient to use commercially. Easily prepared solid catalyst pellets, packed in tubes through which reactants flow, satisfy process requirements for simple operation.Defects and dislocati

13、on on surface crystalline structureuA perfect crystal can be made in a controlled wayuSurface defectsterracestepkinkadatom / vacancyuDislocationscrew dislocation Heterogeneous Catalysts Metals (Transition metals, IB metals); Fe Co Ni Ru Rh Cu Ag Au Pd Os Ir Pt used in hydrogenation and dehydrogenati

14、on processes Supported transition metal salts and/or complexes; PdCl2, CuCl2 used in partial oxidation processes Transition metal oxides and/or sulfides; V2O5, Cr2O3, Fe3O4, MnO2, ZnO, used in oxidation, hydrogenation and dehydrogenation ZnS, PdS, CdS MoS, WS, used in hydrogenation, dehydrogenation

15、, isomerization poreporous solidActive site Heterogeneous Catalysts Solid acids and/or bases; acids: Al2O3, SiO2-Al2O3, rare earth metal salts, etc. bases: alkaline earth metal oxide, supported alkaline metals, etc. Non-metal oxides or mixed oxides; P2O5, B2O3, SiO2 , etc. Zeolites (Natural and/or s

16、ynthesized); A, X, Y, ZSM-5, SAPO, MCM41SPolymers; ion-exchanged resins红宝石(Cr3+) 蓝宝石(Fe3+,Cr3+) 黄玉/黄晶(Fe3+)刚玉自然界- Al2O3Al2O3 Usually, the liquid phase is most common, with both catalyst and reactants in solution. Catalysis occurs through complexing and rearrangement between molecules and ligands of

17、the catalyst. Reactions can be very specific, with high yields of desired products. Since the mechanisms involve readily identified species, these reactions are easily studied in the laboratory with the techniques of organometallic chemistry. They are, however, difficult to operate commercially.The

18、catalyst must be separated from the products, imposing additional difficulties.Homogeneous catalysis is found only in limited industrial use, appearing usually in the manufacture of specialty chemicals, drugs, and food.类固醇-1 , 4-二烯-3-酮制备类固醇-4烯-3-酮某抗生素的制备过程中Commercial Processesu Wacker Process: CH2=C

19、H2 CH3CHO (PdCl2-CuCl2)u OXO Synthesis: R-CH=CH2 + CO + H2 RCH2CH2CHO (Co,RhLx)u Monsanto Process: CH3OH + CO CH3COOH (Co, RhLx)Homogeneous Catalysis Catalystu Lewis acid and/or base: AlCl3, BF3, Pyridine, NH3u Bronsted acid, Base: H2SO4, H3PO4, NaOH, KOH, etc u Soluable transition metal salts: PdCl

20、2, CuCl2, etc. u Soluable transition metal complexes: Co(CO)4, Rh(CO)4, etc Enzymes are the driving force for biochemical reactions. Present in life processes, they are characterized by tremendous efficiencies and selectivities. There is great approach in harnessing enzyme catalysis for industrial u

21、se. Much depends on increasing the ability to withstand sever conditions and developing techniques for anchoring enzymes substrates for use in packed beds. 酶的化学组成 由碳（55）、氢（ 7）、氧（20）、氮（18）、以及少量硫（2）元素和金属离子组成。 性质 从物理结构和聚积态看，酶都是胶体状的、不能透析的、在水中和缓冲溶液中有不同溶解度的两性电解质。 在高温下固化变性、在浓溶液中比在稀溶液中稳定、可用盐类溶液等沉淀剂将其沉淀（或盐析）

22、出来。 分类 单纯酶：由单纯蛋白质组成. 结合酶：蛋白质部分（酶蛋白）和非蛋白质部分（酶的辅助因子）组成。 酶蛋白和酶的辅助因子分别单独存在时均无催化活性，只有二者有机结合成全酶时，才具有催化活性。 辅助因子由金属离子和辅酶或辅基组成。 辅酶与辅基是一些有机物分子，其中大多数是B族维生 素的衍生物 全酶 酶蛋白 辅助因子 辅酶或辅基、金属离子 结构 结构复杂，由四种层次不同的结构组成一级结构：肽链或多肽链二级结构：螺旋、褶片 和氢键三级结构：一二级结构进一 步卷曲、折叠成 的三维空间结构四级结构：酶分子。 酶的四级结构还能进一步集聚成分子量高达十至上百万的超结构高聚物，其大小可以用高倍电子显微

23、镜中直接观察到。 酶分子从四级结构解离成单体时其性质发生改变，（例失去对反应的专一性）甚至完全失去催化活性。但单体重新组合成原来的四级结构其活性恢复。 与均相催化剂相似，目前酶催化剂和反应物多是溶于液体形成均相。Preparationu Homogeneous catalyst as the active componentu Select suitable support; such as polymers, silica gel, zeolitesu Maintain active phase structure; impregnation, chemical adsorption, ch

24、emical bond, anchored etc.Advantages 具有非常裸露的表面u 金属表面原子是周期性排列的端点，至少有一 个配位不饱和位，即悬挂键（Dangling Bond)。这预示着金属催化剂具有较强的活化反应物分子的能力;u 金属表面原子位置基本固定，在能量上处于亚稳态。这表明金属催化剂活化反应物分子的能力强，但选择性差； 金属原子之间存在凝聚作用u金属原子之间的化学键具有非定域性，因而金属表面原子之间存在凝聚作用。这要求金属催化剂具有十分严格的反应条件，往往是结构敏感性催化剂；u金属原子显示催化活性时，总是以相当大的集团，即以“相”的形式表现。如金属单晶催化剂，不同晶面

25、，催化活性明显不同。但同时，其适应性也易于预测； 空的d轨道参与催化反应(1s)2(1s*)2(2s)2(2s*)2(2p)4(2px)2(2p*)0(2p*)0给予金属的未充满的轨道给予金属的未充满的轨道接受金属的接受金属的d电子电子CO的分子轨道的分子轨道 一方面，一方面，CO把一对电子填入把一对电子填入Ni的未充满的轨道中形成的未充满的轨道中形成键，一方面又以空的键，一方面又以空的2p*轨道接受来自轨道接受来自Ni d轨道的电子，轨道的电子，形成形成键，削弱了键，削弱了CO内部成键，活化内部成键，活化CO分子。分子。State Key Laboratory for Heavy Oil P

26、rocessingThe Key Laboratory of Catalysis, CNPCCollege of Chemical Engineering, CUP 形状与粒度 (Shape & Particle size); 密度(Density); 比表面(Specific Surface Area) ; 孔结构(Pore structure); 机械强度(Mechanical Strength);Chemical PropertiesPhysical Properties 活性(Activity); 选择性(Selectivity); 稳定性 (Stability & Lifetime)

27、;形状 (Shape) 表观形状(Apparent Shape)u 球状(Reforming)、条状、片状、柱状(Adsorbent)、网状(Furnace)、粉末状(Hydrogenation)、微球状(FCC)、蜂窝状(Exhaust Gas);u 选用规则 固定床反应器：片状、球状、柱状； 流化床反应器：20150m微球状； 移动床反应器：24mm球状； 悬浮床反应器：粉末级(50m);车轮状与拉西环状烃类水蒸气转化催化剂性能比较车轮状与拉西环状烃类水蒸气转化催化剂性能比较 形状形状 尺寸尺寸/mm 相对热传递相对热传递 相对活性相对活性 相对压力降相对压力降 传统拉西环传统拉西环 16

28、 6.4 16 100 100 100 车轮状车轮状 17 17 126 130 83拉西环七筋车轮状 Reaction O2 + 4H+ + 4e H2OEnrique Herrero , J. Am. Chem. Soc. 2010, 132 (16), pp 56225624A. Baiker et al., J. Am. Chem. Soc. 2009, 131 (16), pp 12385 形成 原子、离子或分子(0.051nm) 单元晶胞(10500nm) 晶粒(一次粒子)(0.1m) 颗粒(二次粒子)(1200m) 成型催化剂(颗粒聚集体, 16mm); 选择u 反应器的结构u

29、单元设备的生产能力；u 催化反应动力学的控制； 检测u 筛分法：20500m ；u 显微镜法：光学 0.8150m; TEM 0.1100nm; SEM 1nm10m; 日立公司日立公司H800H800透射电子显微镜透射电子显微镜u沉降法重力沉降是颗粒在悬浮介质中依靠自身的重力作用自然沉降；离心沉降是在悬浮介质中的颗粒借助离心力作用而沉降；两种方式都是根据大颗粒沉降快、小颗粒沉降慢的规律，从颗粒的沉降速度测定粒径。测量范围： 5500m )(180gdu光散射法当光束照射到颗粒时，光向各个方向散射， 光的散射与颗粒的粒度有一定关联，利用散射光强分布可以测定粒子的尺寸分布；光的散射现象示意图适用

30、性广，可以测固体颗粒、液滴、气泡的尺度； 测试范围：0.012000mu电感应法 基本原理：使悬浮在电解质中的颗粒通过一小孔，在小孔两边各浸有一个电极，颗粒通过小 孔时电阻变化而产生电压脉冲，其振幅与颗粒的体积成正比； 适合于由不同材料组成的混合物的粒度测试，但对带孔颗粒的测试存在较大的误差。测量范围：0.052000m Of particular importance for chemistry, surface energies and surface morphologies of catalyst are size dependent, and this translates to e

31、nhanced intrinsic surface reactivity. Heterogeneous catalysis is dependent on particle size because the particle size can contribute to the electronic effects, support effects, shape effects, and so on.3 nm iron particle has 50% of its atoms on the surface, whereas a 10nm particle has just 20% on th

32、e surface, and a 30nm particle only 5%.Number of shells12345Number of atoms in cluster1355147309561Percentage of surface atom9276635245(1) Changes from cubic to polyhedral shapes,(2) The surface concentration of edges and corner sites goes up considerablyuElectronic effects Electron density changes

33、at catalytic sites can vary due to particle size. However, this concept is rather ill-defined and difficult to separate from electronic effects of the catalyst support present. Nevertheless, there is certainly convincing evidence that ionization energy do change with metal particle size. For example

34、: gas phase nickel cluster for Ni3 to Ni90 exhibit above phenomena. The ionization energy do not smoothly approach the work function as the number of atom increases, but show an oscillation as a function of particle size.u Support effects (Electronic effect and Decoration effects) Small metal partic

35、les bound to a metal oxide surface( the catalyst support ) can most assuredly be affected electronically by the nature of the metal oxide. Smaller metal cluster bound to more electron-donating support would be more significantly altered in electronic density than would larger cluster. Particle size

36、Another interesting phenomena is the tendency of some supports to form deposit on the catalytic metal particles, thereby forming catalytically active interface sites. This interface site could also be sensitive to metal particle size through electronic or geometric effects. Model of Pt/TiO2 catalyst

37、 where a TiO2 patch “decorates” the Pt nanoparticleParticle sizeuShape effects Shape effects have several manifestations. First of all, certain chemical reactions are structure-sensitive. For example: hydrogenolysis of cyclopropane. Another manifestation is the smallness of catalytic particle can af

38、fect crystal shape and therefore surface concentration of edge/corners. Indeed, the edge/corners are the active sites for adsorption and catalytic reaction. Particle sizeExampleuThe aerogel prepared nanocrystalline ZrO2-SO4 was capable of butane isomerization, and relative activity was dependent on

39、SO4 loading. In fact nanocrystalline ZrO2 required about a 2530% loading of sulfur to attain maximum activity, whereas microcrystalline ZrO2 required only about 10%.uThe nanocrystalline ZrO2 was capable of taking on large sulfur loadings, even more than monolayers, and still retain good catalytic ac

40、tivities. Conventional microcrystalline samples were more sensitive to sulfur loading, and when monolayer coverage was exceeded, a precipitous drop in activity resulted.DPCP*+25303540452 Theta14nm3nmThe effect of particle size on the reduction temperature of methanol synthesis catalyst(a) Cu/Ga2O3/Z

41、rO2DPCP00.000010.000020.000030.000040.000050.000060.000070.000080.000090.0001050100150200250300350400Temperature / 0CWeight loss rate /mg.min-1The effect of particle size on the reduction temperature of methanol synthesis catalyst (b) CuO/B2O3/ZrO2DPCP00.000010.000020.000030.000040.000050.000060.000

42、070.000080.00009050100150200250300350400Temperature / 0C Weight loss rate /mg.min-1CatalystCO2 Conv./%CO Select. /%MeOH Select. /%Yield of MeOH /mmol.g-1h-1Cu/Ga2O3/ZrO2DP13.7124.4175.591.93CP-a-0.14Cu/B2O3/ZrO2DP15.8332.7467.261.80CP0.00.00.00.0Bulk volume (VB) VB= Vsk+ Vsp + Vpou Space volume(Vsp)

43、u Pore volume(Vpo) u Skeletal volume(Vsk)u Particle Volume(Vp) VP=Vsk + Vpo校园催化剂 堆密度(Bulk Density)ur = m/VB (VB: 堆体积)；u 用于测算催化剂装量及价格；u测量方法 假密度(Pseudo-Density)u r = m/VP (VP: 催化剂颗粒所占 体积)；u 用于测量催化剂的大孔孔容和 孔隙率；u 测量方法 真密度(Skeletal Density)u r = m/VSk (VSk: 催化剂骨架 所占体积)；u 用于测量催化剂微孔孔容 和孔隙率；u测量方法催化裂化催化剂 堆密度：

44、0.50.8g/cm3 颗粒密度：0.91.2g/cm3 骨架密度：2.02.3g/cm3 用水和所用浸润液体在测定温度下对比重瓶进行温度校正；称重并分别记作B、C; 将待测样品放入比重瓶，称出样品重量，并记作D； 把比重瓶套在加料装置上，抽真空，同时在加料装置中加入所用浸润液体。 样品压力小于1mmHg时，将浸润液体加入待测样品中；称重，记作E； （D-A）/(C-A-E+D) * (C-A)/(B-A)* w A：空容量瓶重 Definition 单位质量催化剂所具有的总表面积(外表面+内表面)； Characters 多相催化剂上进行的催化转化一般是在催化剂表面上 进行的； Method

45、 to testu Static volumetric methods (静态容量法) 静态低温氮气吸附容量法； 低温Kr吸附容量法；u Static gravimetric methods (静态重量法) u Dynamic volumetric methods)(动态容量法(色谱法)； 动态低温氮气吸附容量法(色谱法)gWnmANmlNVWVWANVSmmmmmg/162. 0:/:/36. 41022400228：样品质量氮分子的最大横截面积：阿弗加德罗常数单分子层吸附量ASAP 2010 adsorption instrumentSchematic arrangement of vol

46、umetric adsorption experiment 在吸附过程中，由较低压力下的单分子层吸附转变成较高压力下的多层吸附，最终气体吸附质凝聚下来，形成液体； 在脱附的过程中，脱附时弯月面的蒸发压力与吸附时的饱和压力不同，在吸附时，r=，P=Ps；但脱附时由于 r 变小，P 小于 Ps。因此吸附分支曲线与脱附分支曲线不相重合，形成了滞后回环。吸附与脱附时的孔道模型 测试方法：选择性化学吸附法 该方法是在活性组分的表面原子上吸附一种分子，这种分子在表面上能与活性组分原子进行完全反应，形成化学吸附单层。由吸附物质的化学吸附量计算活性表面积或活性组分的分散状态。 NS = * NA* n 化学吸

47、附气体的体积， VM VM吸附气体的摩尔体积 Sm = NS * S S一个金属原子占据的面积 n化学吸附反应的化学计量数 n的物理意义是指n个金属原子与一个气体分子进行反应，该值大小取决于气体的性质以及所测定的金属。Surface area of active componentExample: （线型吸附态 ） （桥式吸附态） 氢滴定法 Example: Pt/Al2O3 , Pt-H， H H H2 + 2Pt PtPt OCNin=1OCNiNin=2Surface area of active component 氧滴定法 O O O2 + 2Pt PtPt 氢氧滴定法 先吸附氧，然

48、后吸附氢。氢和吸附的氧化合生成水，水被吸收。由消耗的氢量，进而依据O/Pt1算出Pt的表面积。 O O O2 + 2Pt PtPt O O H H PtPt + 3H2 PtPt 2H2OSurface area of active component CO滴定法 Example: Fe, Pt, Pd, Ni, Co, etc, 镍表面积的测定 硫容法： Ni + H2S Ni-S +H2孔产生的根源挤压粉末成型中的孔胶体中的孔稳定晶体中的孔热过程和化学过程产生的孔Pore structure比孔容(Specific Pore Volume) 定义：单位质量催化剂内部所有孔体积的总和； 单位

49、: ml/g孔径(Pore Diameter) 将所有催化剂内部孔道近似为圆柱毛细孔，孔容除以比表面即为孔径；孔径分布 (Pore Distribution)u 50nm macropore u 测试:气体吸附法和压汞法 气体吸附法（低温N2吸附容量法） 测试范围：0.45300nm微孔、中孔分布 原理：填充理论 微孔微孔的孔填充是一个的孔填充是一个连续连续的过程；而的过程；而中孔中孔的填充的填充 则是气体在孔内的则是气体在孔内的凝聚凝聚过程，它表现为一级过程，它表现为一级气气-液相转移液相转移。 微孔测试p计算方法： Horvaih-Kawazoe(H-K)法， Dubinin-Radush

50、kevich(D-R)法 tPlot法 MP法等p局限性：仅致力于描述微孔填充而不能应用于中 孔分析。 介孔测试 以Kelvin 方程为基础，与孔内毛细管凝聚现象相关。 毛细凝聚 当吸附质的蒸气与多孔固体表面接触时，在表面吸附力场的作用下形成吸附质的液膜，在孔内的液膜则随孔径的不同而发生不同程度的弯曲，而在颗粒外表面上的液膜相对比较平坦。蒸气压力增加时吸附液膜的厚度也增加。当达到某一时刻，弯曲液面分子间的引力足以使蒸气自发的由气态转变成液态，并完全充满相应的毛细孔，这种现象称为毛细凝聚。 Kelvin 方程 2VMCOS ln(p/ps) = - RT rk -吸附质的表面张力 VM-吸附质液