材料化學期末試題題庫 Band Theory 1. Define density of state (DOS) ? k-space 中以 DOS(縱軸)對 E(橫軸)做圖時 slope

越大有何意義 ? ANS: (a)DOS(density of state，dn/dE ) = number of levels between E and (E +dE) (b)若斜率越大，表示能階之間的△E 越大，DOS 越小。 2. Please draw the Fermi-Dirac distribution in a semiconductor of (a) Pure solid; (b) n-type; (c) p-type. ANS: 請參閱上課講義 band theory-2 page 15. 3. (a) What is Fermi level? (b)What is the difference of Fermi distribution and the band gap at T>0 for (i) intrinsic semiconductor; (ii) insulator? ANS: 請參閱上課講義 band theory 4. Give a brief introduction of band theory. What’s the difference between insulators and semiconductors? ANS: 請參閱上課講義 5. TiO與NiO的結構均為Rock salt,為何為TiO導體，而NiO卻為絕緣體？ Ans： 因 為Ti的d

orbital ，以dxy, dxz, dyz鍵結，彼此間重疊部分多，形成t2g band，故可導電而Ni的d orbital 以dz2 dx2-y2鍵結，指向氧原子，與其他Ni的orbital 不重疊故導電差

6. Please draw the energy profile of the n-type and p-type semiconductor

ANS: 請參閱上課講義

7. Explain the theory of “P-N Junction” and how can it work as a electrical switch. ANS: 請參閱上課講義

8. What is electro-optic effect? ANS: It is a change in optical properties of materials in response to an electric field that varies slowly compared with the frequency of light. We can achieve the changing by change of the absorption or refractive index. 9. 請利用 energy (band) diagram 解釋在原(分)子狀態與固體狀態的吸收光譜. Ans:

10. Diamond is an insulator while graphite is a moderately good conductor. Explain

these facts in terms of their bonding characters. ANS: 石墨的分子軌域是以 sp2 鍵結，它垂直於結構面的 pi 軌域會形成非定域化的pi 鍵結能帶，電子可以經由 pi 能帶導電，但垂直於結構平面方向則無導電性，因石墨面與面間是凡得瓦而力. 而鑽石的結構是 sp3 鍵結，sigma bond 形成的價帶與導帶之能隙大，電子無法克服能隙，而成為絕緣體. Crystal Growth 1. What is the different between congruent and incongruent melting in binary system? ANS:

The congruent melting: The intermediate compound AB2melts congruently, because at some temperature (the top of the AB2phase boundary line) it coexists with a liquid of the same composition. Incongruent melting is the temperature at which one solid phase transforms to another solid phase and a liquid phase both of different chemical compositions than the original composition. 2. Describe three methods of film formation and their characteristics.

ANS:

a. Dip Coating: 直接將被鍍物浸入鍍膜溶液中，再緩慢將之拉昇脫離液面藉由溶劑

揮發即可形成鍍膜，此法速度較慢且膜厚較厚且不易控制。

b. Spin Coating: 直接將鍍液滴於被鍍物上，再利用離心力將被鍍液均勻地分佈於被

鍍物上，待溶劑揮發即可形成鍍膜，但此法不適用於大面積之鍍膜。

c. Vapor Deposition: 利用蒸氣沉積之方法成膜，於真空氣氛下或加熱下，將欲鍍膜

之成分揮發使成氣態再均勻凝結沉積於被鍍物上。此法可得到薄且均

勻之膜厚，同時適用於大面積之鍍膜。但設備及操作價格昂貴。

4. What factors control the size and purity of single crystal growth? ANS: 1. Nucleation.

2. Growth rate. If nucleation rates are slow and growth is rapid, large crystals will result. On the other hand, if nucleation is rapid, relative to growth, small crystals or even polycrystalline samples will result.

5. Explain three ways to control the nucleation rate ? ANS : (a) slow cooling of melts (b) temperature gradients (c) introduction of seed crystals 6. What can be done to increase the crystal growth rates? ANS: In order to attain the rapid growth rates needed to grow macroscopic crystals, diffusion coefficients must be large. Hence, crystal growth typically occurs via formation of a solid from another state of matter: (a) liquid (Melt) solid (Freezing) (b) gas (vapor) solid (condensation) (c) solution solid (Precipitation) 7. (A) State the variety of crystal growth technologies according to their

development. (B) Which of them is extensively used in the semiconductor industry? What is it advantage? ANS: (A) a.Verneuil’s method b.Czochchralski method c.Kyropoulos method d.Bridgeman method e.Floating Zone method f.Stockbarger method g.Zone melting method (B) Czochchralski method is extensively used in the semiconductor industry. It is that large single crystals can be grown. Solid_synthesis 1. How to prepare ferrofluids? ANS: A. 2 FeCl3+ FeCl2+ 8 NH3+ 4 H2O →Fe3O4 (s)+ 8 NH4Cl (aq) B. Add cis-oleic acid [CH3(CH2)7CH=CH(CH2)7COOH ] in oil C. Remove water 2. What is sol-gel process? What kind of materials can be prepared by sol-gel process? ANS: 請參閱上課講義 3. What is solid state reaction？What are the problems？How to solve them？ ANS: 請參閱上課講義 Area of contact：Powder the product Rate of diffusion：Rise T，add to carbonates or nitrates Rate of nucleation：Crystal structure，use the same structure reactant to rise rate 4. In solid state reaction, how to increase the rate of diffusion？ ANS: Increase temperature and introduce defects by starting with reagents that

decompose prior to or during reaction. 5. 畫圖並解釋 congruent melting 和 incongruent melting (使用 binary system) ANS: 請參閱上課講義 For congruent melting, the end members (A&B) are assumed to melt congruently. The intermediate compound AB2 melts congruently, because at some temperature (the top of the AB2 phase boundary line)it coexists with a liquid of the same composition. ………. 6. Please explane the principle of chemical vapor deposition (CVD)? ANS: (CVD) is a chemical process for depositing thin films of various materials. In a

typical CVD process, the substrate is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber. 7. Explain the following terms in solid synthesis (a) Solid State Metathesis Reactions (b) Hydrothermal Synthesis (c) Intercalation ANS: (a) A metathesis reaction between two salts merely involves an exchange of anions, although in the context we will use there can also be a redox component. If the appropriate starting materials are chosen, a highly exothermic reaction can be devised. (b) Reaction takes place in superheated water, in a closed reaction vessel called a hydrothermal bomb (150 < T < 500 °C; 100 < P < 3000 kbar). Seed crystals and a temperature gradient can be used for growing crystals (c) Involves inserting ions into an existing structure, this leads to a reduction (cations inserted) or an oxidation (anions inserted) of the host. Typically carried out on layered materials (strong covalent bonding within layers, weak van der Waals type bonding between layers, i.e. graphite, clays, dicalchogenides,). Performed via electrochemistry or via chemical reagents as in the n-butyl Li technique. 8. When choosing the precursor compound for Chemical Vapor Deposition process, what factors need to be concerned?

ANS: (1)易揮發 (2)single source 包含多種所需元素 (3)純度 (4)愈低溫愈好

9. 為何固態反應法常會添加助熔劑(flux)來幫助反應進行，試問添加助熔劑之功用

為何？ 試舉例應用助熔劑之固態反應法例子。

ANS: 助熔劑為一種於高溫下呈熔融態的金屬鹽類之溶劑，其可幫助反應物在較

低溫條件下（低於該熔點）變成融熔態，並可增進各反應物之擴散作用，使各反應

物混合均勻。例如：4SrCO3 + Al2O3 + Ta2O5→Sr2AlTaO6 (SrCl2 flux)

10. Explain what advantages and disadvantages the “Precursor route” have in

comparison to “solid state reaction”. ANS: In solid state reaction, stoichiometric amounts of reactants in powder form are mixed and heated at high temperature to react. In the precursor route, a mixture of the solution containing the salts of reactants is used.

• Advantages: Decrease diffusion distances through intimate mixing of cations. Lower reaction temps, possibly stabilize metastable phases, eliminate intermediate impurity phases, produce products with small crystallites/high surface area. • Disadvantages: Reagents are more difficult to work with, can be hard to control exact stoichiometry in certain cases, sometimes it is not possible to find compatible reagents (for example ions such as Ta5+and Nb5+ immediately hydrolyze and precipitate in aqueous solution).

OLED 1. Explain the basic theory of OLED. ANS: OLED 的基本原理為: 加入一外加偏壓，使電子電洞分別經過電洞傳輸層與電子傳輸層後，進入一具有

發光特性的有機物質，在其內發生再結合時，形成一"激發光子"後，再將能量釋放出來而回到基態，而這些釋放出來的能量當中，通常由於發光材料的選擇及電

子自旋的特性，只有 25%（單重態到基態，）的能量可以用來當作 OLED 的發光，其餘的 75%（三重態到基態，）是以磷光或熱的形式回歸到基態。由於所選擇的發光材料能階的不同，可使這 25%的能量以不同顏色的光的形式釋放出來，而形成 OLED 的發光現象 2. How can OLED emit light? Please show at least two kind structure of OLED . ANS: 當電流從 cathode 流向 anode 時,會將 hole transporting layer 的電子打向electron transporting layer，電子在返回的過程中會放出 light. 3. Briefly describe the principle of LED. ANS:

A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction. This effect is a form of electroluminescence. The color of the emitted light depends on the chemical composition of the semiconducting material used.

4. What are the two main directions in OLED? ANS: (1) small molecules:requires vacuum deposition which makes the production process expensive and not so flexible. (2) polymers:No vacuum is required,and the emissive materials can be applied on the substrate by a technique derived from commercial ink-jet printing. 5. Please

(a) compare Organic Light-Emitting Diodes (OLED) with liquid crystal display (LCD)

(b) describe the disadvantages of OLEDs

ANS: (a) Wide viewing angle

Very bright and highly contrast No back-lighting needed (low energy consumption) Fast switching times (video-rate display) Multicolor emission (RGB) Thin and light weight Foldable, very thin screen possible

(b) Engineering Hurdles–OLED’sare still in the development phases of production.Although they have been introduced commercially for alphanumeric devices like cellular phones and car audio equipment, production still faces many obstacles before production.

Color lifetime–The reliability of the OLED is still not up to par.After a month of use, the screen becomes nonuniform.Reds, and blues die first, leaving a very green display.100,000 hours for red, 30,000for green and 1,000 for blue.Good enough for cell phones, but not laptop or desktop displays. Overcoming Commercial development of the technology–LCD’s have predominately been the preferred form of display for the last few decades. Tapping into the multi-billion dollar industry will require a great product and continually innovative research and development. Furthermore, the basics of OLED technology is heavily patented by Kodak and other firms, requiring outside research teams to acquire a license.

6. Explain what is Second Harmonic Generation (SHG)? ANS: The Second Harmonic Generation is the conversion of coherent light of frequency ω into light of frequency 2ω. 7. What is the thin-film transistor? It’s application? ANS: A thin film transistor (TFT) is special kind of field effect transistor made by depositing thin films for the metallic contacts, semiconductor active layer, and dielectric layer. Most TFTs are not transparent themselves, but their electrodes and interconnects can be. The best known application of thin-film transistors is in TFT LCD’s. Transistors are embedded within the panel itself, reducing crosstalk between pixels and improving image stability.

8. Describe the mechanism of the turning of energy gap by donor and accepter in OLED. ANS: 請參閱上課講義 9. Explain the role of Alq3 in OLED. Please enumerate three advantages of Alq3 compound. ANS: 請參閱上課講義 Advantage-

Ball-shaped molecule：Hard to crystallize Six-coordinated metal：Chemical inert Availability：Very easy to synthesis

10. OLEDs 如何產生 Full Color？ ANS: a. Side by Side patterning of RGB emitters

b. Color passband filting of white emitters c. Wavelength down-conversion of blue emitters d. Micro cavity-filtered White emitters e. Cd or tunable stacked emitters

11. Assumed the donor is on HOMO, how does the energy gap change？ If the acceptor is on LUMO, how does the energy gap change？ Please sketch the change of energy level and explain it. Ans：Both of them are red-shifted.

Donor提供電子會使使原本的LUMO與HOMO均上升。但是因為donor on

HOMO，所以HOMO上升幅度比LUMO

大，使得energy gap縮小，因此是

red-shifted。 Acceptor拉電子會使使原本的LUMO與HOMO均下降。但是因為acceptor on LUMO，所以LUMO下降幅度比H大，使得energy gap縮小，因此是red-shifted。 圖示如右上所示。

OMO

12. What is OTI? Why is it an important electrode in flat display?

ANS: Indium tin oxide (ITO, or tin-doped indium oxide) is a mixture of In2O3 and SnO2, typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers. ITO's main feature is the combination of electrical conductivity and optical transparency.

OTI 常用來作為 OLED 的陰極，因為它透明而且可以導電，其還原電與大部分的 OLED 的 HOMO 相差不遠. 13. What is “Polymer poling”?

Ans: This is a process to prepare polymer film containing chromophores for non-linear optics. The polymer is heated above the glass transition temperature and placed in a strong external electric field. The field serves to orient the chromophore with its dipole moment parallel to the applied field. As a result, their structures become non-centrosymmetric and the second-order susceptibility is no longer zero.

14. Please draw the diagram of three layers of Organic Light Emitting Devices and

explain the function of each layer. ANS:

15. Please draw a diagram to describe the luminescence mechanism for fluorescence

and phosphorescence. ANS:

POLYMERS 1. Many commercial polymers are prepared from more than one monomer. These materials are called co-polymers. Please describe the four most common co-polymers.

ANS: 請參閱上課講義

2. Please distinguish between thermoplastic polymer and thermosetting polymers. ANS: Thermoplastic polymer: one that can be softened by heating and then formed into desired shapes by applying pressure. Thermosetting polymer: become permanently hard at elevated temperatures and pressures. 3. Explain the differences between HDPE 和 LDP. ANS: High-density polyethylene (HDPE) consists primarily of linear molecules and has a higher density, greater rigidity, greater strength, and a higher melting point. Low-density polyethylene (LDPE) has branched chains and is a waxy, semi-rigid, translucent material with a low melting point. 4. What is conducting polymer? Explain the mechanism of its electrical conductivity and give examples of its applications. ANS : (a) Conducting polymers are polymeric materials containing conjugated

π-bonds, which have very close spaced π-molecular orbitals and form band structure as that in the metal. The conductivity is enhanced by doping electron-donor or acceptor species.

(b) 經過redox rxn後加入一些e- donor或是accepter； (Pn → Pn+A- → Pn2+2A-) 接著發生 charge transfer complexes 使其可以導電； (Pn．+A- + Pm → (PnPm)．+ + A-) (c) OLED，electroluninescent dieplays for cell phones(手機的顯示器) 5. Show the differences between isotactic, syndiotactic and atactic polypropylene.

ANS: 請參閱上課講義 6. Describe the three reaction steps in synthesis of addition polymerization ANS: 請參閱上課講義 7. Explain the application of conducting polymer? ANS: a.emissive layer in full-color video matrix displays b.electromagnetic shielding of electronic circuits c.electroluminescent displays(mobile telephones) d.antistatic coating material to prevent electrical discharge exposure on photographic emulsions e.field-effect transistors (usage in supermarket checkout) f.absorb microwaves: stealth technique g.hole injecting electrodes for OLED 8. What is composite material? What is the difference between the properties of its

component? ANS: Composite materials are engineering materials made from two or more components. (a) strong fiber- this give the materials tensile strength (b) resin- this bind the fiber together, transferring load from broken fibers to unbroken one and between fibers that are not oriented along lines of tension.

9. Distinguish between (a) addition polymerization and (b) condensation polymerization. ANS: 請參閱上課講義

10. 試解釋何謂 Nonlinear optics? ANS: The interaction of electromagnetic field with various media to produce new electromagnetic fields altered in

(1) phase (2) frequency (3) amplitude

from the incident field. 11. Nafion○R為杜邦公司所開發的隔離膜，其乃一種proton-conducting polymer，

分子結構如下圖所示：

試問如何控制其導電度以及其限制為何？

ANS: Nafion 主要由水合離子的傳遞來導電，故需要在低於 100˚C，有水的環

境下才可使質子藉由磺酸根離子進行傳遞。所以此材料不能用在超過 100˚C 的環

境。

12. Define “Vulcanization” and explain how it is applied in polymer materials. ANS: Vulcanization is a process to crosslink double bonds in between polyisoprene (rubber) chains by sulfur. This process is an irreversible process and make rubber a thermoset instead of a thermoplastic. The hardness is increased with the amount of sulfur added. 13. Distinguish between thermoplastic and thermosetting polymers. Which of them

will be able to be recycled and reused? ANS: • Thermoplastic polymer is one that can be softened by heating and then formed into desired shapes by applying pressure. • Thermosetting polymers usually have polymer chains cross-linked and become permanently hard at elevated temperatures and pressures. • Thermoplastic polymer can be recycled and reused but not thermosetting polymers.

14. Describe three kinds of polymer-clay based composites. Which of them are

considered nanocomposites? ANS:

Nanoporous materials 1. Why the anodic alumina pores form the hexagonal array? ANS: The mechanical stress at the metal/oxide interface is proposed to cause repulsive forces between the neighboring pores which promote the formation of ordered hexagonal pore arrays. 3. Give two examples for the applications of nano-porous materials, and describe

them in details. ANS: (1) Catalysis, (2) Adsorbents & ion-exchangers ………………………….. 3. Distinguish between Zeolites and Molecular Sieves. ANS: Zeolites -crystalline aluminosilicate with open structures Molecular Sieves

-materials which can separate gases based on molecular size 4. IUPAC 把奈米孔洞材料大小分成三類，請寫出其分類的孔洞半徑大小以及其名稱. ANS: 微孔洞 microporus, d

9. 試舉出改變奈米孔洞半徑的方法?

ANS: Change the length of surfactant alkyl chain or add hydrophobic regents to expand the hydrophobic volume of the micelle. 10. Please explain the theory of Anti-reflectance film ANS: 請參閱上課講義 Nanoporous materials 102 11. Describe three purposes for functionalization of surface silanol groups in nanoporous materials. ANS: (a) change the pore size

(b) change surface hydrophilicity (c) anchor catalytic sites

12. Explain the pore characters of the materials in corresponding to the following N2

absorption-desorption isotherms.

ANS: Type I. microporous – microporous condensation occurs at very low pressure Type Ⅱ. standard shape of non-porous Type Ⅲ. nonporous, unusually weak interaction between adsorbate and adsorbent Type Ⅳ. mesoporous – capillary condensation Type Ⅴ. mesoporous, unusually weak interaction between adsorbate CHARACTERIZATION

1. X-ray can help characterization of nano-porous materials. When the size of nano-porous materials increases, does the 2θ measured by XRD increase or decrease? ANS: decrease. 2. What is the correlation between XANES and oxidation state? ANS: oxidation state↑, XANES edge shift toward higher eV. 3. What are the basic theories of XANES and EXAFS and what informations can be obtained from them? ANS: 請參閱上課講義 4. Describe the basic theory of Mercury Intrusion Porosimetry. ANS: Resistance force due to surface tension = force of applied pressure ………………………….. 5. What is “Scherrer’s equation”? Show how it can be used to determine the particle size. ANS: 請參閱上課講義

6. How can you distinguish single crystal and polycrystalline samples?

ANS:

(1). 使用 TEM 方法:

a. 如果是單晶，則其 diffraction pattern 於中心點週遭會呈現單純點狀圖譜。

b. 如果是 polycrystalline，其 diffraction pattern 於中心點週遭會呈現圓形一圈

圈之特性圖譜。

(2). 使用 XRD 方法:

如果是單晶則 XRD 其 diffraction pattern 會僅以該面之特性 2θ角度重複出

現，例如(1.1.0)下一個出現即為(2.2.0) 特性 2θ角度，但 polycrystalline 不

會有此現象。

7. 下圖為由Differential Scanning Calorimetry (DSC)得到之數據，請解釋A、B、C三區域各代表何種現象之發生。

ANS: 請參閱上課講義 Solid_synthesis page 102. 8. Compare the difference in basic theories, design and information gained in TGA and DSC. ANS:

TGA DSC

性質 測重量損失 測溫差, 或熱量補償

原理

在加熱或冷卻過程中, 由於待測物會因反應導致重量的變化,而因溫度變化造成的重量變化

可由高靈敏度之天平量測獲得

將待測物和標準物於溫控系統

測試,由於標準物不會有反應,當待測物發生吸熱(或放熱),系統在待測物端會額外多輸入(或減少)一些熱量, 以保持兩者溫度一致

待測溫度 變溫 變溫

結構示意圖

得到訊息

？ ？

9. Please describe the advantage of X-ray absorption Spectroscopy ANS:

A powerful structural tool for materials in various forms, including crystalline or amorphous solids, liquids, and gases. Sample is not required to have structure if long range order.

XANES reflects effective charge density, electronic structure, and coordinate symmetry of the absorber.

EXAFS provides the information of local (

ANS: (a) absorption spectroscopy in the UV/Visible range (b) UV photoelectron spectroscopy (c) inverse photoelectron spectroscopy (d) X-ray absorption spectroscopy (e) X-ray emission

13. What is “Magic angle spinning”? Explain the reason of using this technique in

solid state NMR. ANS: The contribution of dipolar interaction in solid state samples is about the same magnitude as the chemical shift, which we are interested to find out.

Since the energy due to dipolar interaction is a function of (3cos2θ -1), the interaction will be cancelled if the sample is placed at an angle of 54.44˚ from the magnetic field.

Now-a-day, in solid state NMR, the samples are spinned at an angle of 54.4˚ from the magnetic field.

CATALYTIC MATERIALS

1. What are the three classes of catalysts? ANS: a. Heterogeneous. The catalyst and the reactants are in different phases.

b. Homogeneous. The catalyst and the reactants are in same phases c. Biological. The catalyst are enzymes.

2. Classify the heterogeneous catalysts and explain their functions. ANS: (1)Metals (2)Semi-conducting oxides & sulphides (3)Insulator oxides (4)Acid

Function 請參閱上課講義 3. Explain the support effects in Automotive emission control catalyst for the following supports.

(1) Al2O3 (2) CeO2

ANS: 請參閱上課講義 4. CeO2 was served as an oxygen storage medium. What are the reactions of CeO2 under fuel lean and fuel rich condition, respectively? ANS: p.77 (投影片弄相反了) 1. Fuel lean: O + Ce3+ → Ce4+ (i.e. CeO2) 2. Fuel rich: CeO2 → Ce3+ + O 5. Show the reaction rate of enzyme catalyzed reaction as a function of substrate concentration, enzyme concentration and temperature. ANS: 請參閱上課講義 6. Draw the energy profile for the catalytic reaction on a surface that carried out with chemical adsorption process. Describe the differences between physical and chemical adsorptions? ANS:

請參閱上課講義 7. What is heterogenous catalyst? Many reactions are catalyzed by the surfaces of appropriate solids. What are the steps in heterogenous catalytic reaction? ANS:

Heterogenous: The catalyst and the reactants are in different phases. Steps in heterogenous catalytic reactions:

2. Diffusion to the surface 3. Adsorption of reactants 4. Surface diffusion of reactans 5. Surface reaction 6. Surface diffusion of products 7. Desoprtion of products 8. Diffusion away from the surface

8. Show the reaction mechanism of methanol carbonylation catalyzed by [Rh(CO)2I2]-? ANS: 請參閱上課講義 9. Distinguish the differences between SOFC and PEMFC. ANS: 請參閱上課講義 10. What is SOFC? Explain its components and working condition.

ANS: SOFC 為Solid Oxide Fuel Cell之簡寫，此Fuel Cell 之electrolyte為 solid

oxide 且操作溫度通常大於600℃。如下圖所示:

11. Please (a) explain the demanding and facile reaction

(b) point out which curve is demanding reaction.

Curve A

Curve B

ANS: (a) demanding rxn.–structure-sensitive

The active site may be a single surface atom. facile rxn.–structure-insensitive

The active site may be several surface atoms whose arrangement relative to each other is critical.

(b) Curve B is demanding rxn.

12. Explain the relationship between catalytic activity and adsorption with Volcano curve. ANS: 當吸附過程太弱時，反應物無法吸附觸媒表面，造成催化活性降低，然 而當脫附過程太強時，觸媒表面形成的反應物無法離開，阻擋反應物的吸 附，導致催化活性降低。 13. 何謂光觸媒？簡述原理及在實際生活上有何應用？ 試舉例 ANS: 請參閱上課講義 14. TiO2 is an efficient photocatalyst. Propose the possible pathways for the formation of hydroxyl radical which is the active species for photocatalytic reactions. ANS:

15. In thermal cracking, what are the large amounts of products？ And please explain what is empirical β rule. ANS: The large amounts of products in thermal cracking are ethylene and methane.

Empirical β rule is C-C bond scission at C-C bond βto C atom having unpaired electron.

16. Describe the considerations in supported metal catalysts in terms of (a) metal particle size effect (b) support effect (c) metal-support interaction ANS: 請參閱上課講義 17. What is the advantage of using super acids as the catalyst in n-hexane isomerization? ANS:

因為 isomerization 的目的是為了要得到辛烷值高的多支鏈產物, 而在低溫下多支鏈產物的比例較高, 加上此反應可以利用酸催化,不過,酸在低溫下的解離度會下降,所以可以利用 super acid 克服解離度上的問題. 18. There are two cracking processes: thermal and catalytic. Explain the differences

in their operation condition, reaction mechanism and products. ANS: 請參閱上課講義 19. What are the poisoning and the promoter of catalysis materials? Give an example for each of them. ANS: Poisoning is an impurity in the feed stream alters the surface composition of the metal by stronger chemisorbed than reactants or alloy formation. Most of them are electronegative species. Example: Fe for NH3 synthesis is poisoned by forming metal oxide. Promoter is a small amount of species on the catalyst or in the feed stream to improve the catalytic activity or selectivity. Most of them are electropositive species. Example: In CO hydrogenation, absorbed K increase the rate of CO dissociation on Ni, increase carbon level and increase the rate of formation of higher hydrocarbon. 20. The silver catalyst is widely used for ethylene oxidation formation in industry :

i) Please give the mechanism of this reaction and indicate the by-product

formed? ii) What is the limitation of supports used in this reaction? iii) ANS: (i)

CO2 為副產物 (ii)

21. Please draw a diagram for Proton-Exchange Membrane Fuel Cell (PEMFC).

Give half reaction of each electrode and total reaction. ANS:

22. Describe the methods to determine the (i) total surface are, and (ii) effective surface area of a solid catalyst. ANS: (i) 請參閱上課講義 Charaterization -1 講義第 43-44 頁 (ii) 請參閱上課講義 Catalyst 講義第 51-52 頁 22. 車輛所排放的廢氣中, 對環境危害最嚴重的是哪三種氣體? 目前的汽車安

裝的觸媒轉化器是用何種觸媒來去除這些毒性物質, 請以反應式表示出. ANS: 請參閱上課講義 Catalyst Materials 講義 p. 77