復(fù)試復(fù)習(xí)化反新課件第3、4章

1、第三章 速度定律和化學(xué)計量方程 Rate Laws and Stoichiometry1、反應(yīng)速率常數(shù)和反應(yīng)級數(shù)2、基元反應(yīng)和非基元反應(yīng) 3、可逆（對行）反應(yīng)4、摩爾數(shù)的變化5、膨脹因子Reaction order is determined from experimental observation:The reaction in eq (S3-1) is order with respect to species A and order with respect to species B, whereas the overall order is + . Reaction order is

2、 determined from experimental observation. If =1 and =2, we would say that the reaction is first-order with respect to A, second-order with respect to B, and overall third-order.Summary2. In addition to the reaction order, the following terms were defined:a、Elementary reactionb、Reversible and irreve

3、rsible reactionsc、Homogeneous and heterogeneous reactions3. The temperature dependence of a specific reaction rate is given by the Arrhenius equation，Where A is the frequency factor and E the activation energy.4. The stoichiometric table for the reaction The relative rates of reaction areBeing carri

4、ed out in a flow system is :5. In the case of ideal gases, Equations(S3-3）through (S3-6) relate volume and volumetric flow rate to conversion.Batch variable volume:Batch constant volume ：Flow systems:Where the change in the number of moles per mole A fed is. and the change in the number of moles per

5、 mole A reacted is.6. For the ideal gas-phase reaction the volumetric flow rate isUsing the stoichiometric table along with the definitions of concentration (e.g., ), the concentrations of A and C are:7.When the reaction and products are pressible liquids, the concentrations of species A and C in th

6、e reaction given Equation（2-2）can be written as Equations（S3-11) and (S3-12) also hold for gas-phase reactions carried out at constant volume in batch systems. 8.When using measures other than conversion for reactor design, the mol balances are written for each species in the reacting mixture：The mo

7、le balances are then coupled through their relative rates of reaction. If Concentration can also be expressed in terms of the number of moles (batch) in molar flow rates (flow) P3-l6A (p120)The gas-phase reaction 2A + 4B 2Cwhich is first-order in A and first-order in B is to be carried out isotherma

8、lly in a plug-flow reactor The entering volumetric flow rate is 2.5 dm3/min, and the feed is equi-molar in A and B. The entering temperature and pressure are 727oC and 10 atm, respectively. The specific reaction rate at this temperature is 4 dm3/gmol. min and the activation energy is l5,000 cal/gmol

9、. (a) What is the volumetric flow rate when the conversion of A is 25%? (Ans.:v = 1 .88 dm3/min.) (b) What is the rate of reaction at the entrance to the reactor?(i.e., X = 0)? (Ans.: -rA = l.49l0 -2 g mol/dm3min.)(c) What is the rate of reaction when the conversion of A is 40%?(Hint. First express

10、-rA as a function of X alone.)(Ans.-rA = 4.95l0 -3 g mol/dm3min.)(d) What is the concentration of A at the entrance to the reactor?(Ans.: CA0 = 6.0910 -2 g mol/dm3.)(e) What is the concentration of A at 40% conversion of A?(Ans.: CA = 6.09l0-2 g mol/dm3.)(f) What is the value of the specific reactio

11、n rate at l227oC?(Ans.: k = 49.6 dm3/g molmin.)Additional problem:Calculate for following reactions:A B pure A as a feedstockA 2B pure A as a feedstock2A B 70% A and 30% inertA 2B 60% A and 40% inert 第四章 等溫反應(yīng)器的設(shè)計 Chapter 4 Isothermal Reactor DesignIn this chapter we bring all the material in the pre

12、ceding three chapters together to arrive at a logical structure for the design of various types of reactors. By using this structure, one should be able to solve reactor engineering problems through reasoning rather than memorization of numerous equations together with the various restrictions and c

13、onditions under which each equation applies (i.e., whether there is a change in the total number of moles, etc.).This chapter focuses attention on reactors that are operated isothermally.In perhaps no other area of engineering is mere formula plugging more hazardous; the number of physical situation

14、s that can arise appears infinite, and the chances of a simple formula being sufficient for the adequate design of a real reactor are vanishingly small. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR.After illustrati

15、ng the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semi-batch r

16、eactors. Example 4-1 Determining k from Batch DataIt is desired to design a CSTR to produce 200 million pounds of ethylene glycol （乙二醇）per year by hydrolyzing （水解）ethylene oxide（環(huán)氧乙烷）. However, before the design can be carried out, it is necessary to perform and analyze a batch reactor experiment to

17、 determine the specific reaction rate constant（反應(yīng)速率常數(shù)）.Since the reaction will be carried out isothermally（等溫進(jìn)行）, the specific reaction rate will need to be determined only at the reaction temperature of the CSTR. At high temperature there is a significant by-product formation, while at temperature

18、below 40 the reaction does not proceed at a significant rate; consequently, a temperature of 55 has been chosen. Since the water is usually present in excess（過剩）, its concentration may be considered constant during the course of the reaction. The reaction is first-order in ethylene oxide. In the lab

19、oratory experiment, 500 mL of a 2 M solution (2 kmol/m3) of ethylene oxide in water was mixed with 500 mL of water containing 0.9 wt % sulfuric acid（硫酸）, which is a catalyst. The temperature was maintained at 55. The concentration of ethylene glycol was recorded as a function ( Table E4-1.1). From t

20、his data, determine the specific reaction rate at 55. P132 例題41 從間歇反應(yīng)器的數(shù)據(jù)確定反應(yīng)速率常數(shù)k (Determining k from Batch data)在CSTR反應(yīng)器內(nèi)由環(huán)氧乙烷水解生成乙二醇，年產(chǎn)量2億磅。在設(shè)計之前，必須進(jìn)行間歇反應(yīng)器實驗，以確定反應(yīng)速率常數(shù)k。由于反應(yīng)將在等溫下進(jìn)行，僅需確定在CSTR反應(yīng)溫度下的反應(yīng)速率值。在高溫下有大量副產(chǎn)物生成，而低于40時反應(yīng)很慢。因此，溫度選55。由于水過量，水濃度在反應(yīng)中被視為常數(shù)。反應(yīng)對環(huán)氧乙烷為一級。在實驗室內(nèi)，500mL濃度為2M(2kmol/m3)的環(huán)氧乙烷水

21、溶液與500mL含有0.9wt%硫酸水溶液混合，硫酸為催化劑。溫度恒定在55。乙二醇的濃度作為時間的函數(shù)被記錄（見表E4-1.1）。利用這些數(shù)據(jù)，確定55時反應(yīng)速率常數(shù)k。時間（min）乙二醇濃度（ kmol/m3）0.00.0000.50.1451.00.2701.50.3762.00.4673.00.6104.00.7156.00.84810.00.957Table E4-1.1 乙二醇濃度隨時間的關(guān)系數(shù)據(jù)A：環(huán)氧乙烷，B：水，C：乙二醇（產(chǎn)物）t(min)CC(kmol/m3)0.00.0001.0000.50.1450.8551.00.2700.7301.50.3760.6242.00

22、.4670.5333.00.6100.3904.00.7150.2856.00.8480.15210.00.9570.043Reaction Rate EquationIntegration of Rate EquationA reacted = C producedExample 4-2 Producing 200 Million Pounds per Year in a CSTRClose to 5.2 billion pounds of ethylene glycol were produced in 1995, which ranked it the twenty-sixth most

23、 produced chemical in the nation that year on a total pound basis. About one-half of the ethylene glycol is used for antifreeze while the other half is used in the manufacture of polyesters. In the polyester category, 88% was used for fibers and 12% for the manufacture of bottles and films. The 1997

24、 selling price for ethylene glycol was $0.38 per pound. It is desired to produce 200 million pounds per year of ethylene glycol. The reactor is to be operated isothermally. A 1 lb mol/ft3 solution of ethylene oxide in water is fed to the reactor together with an equal volumetric solution of water co

25、ntaining 0.9 wt % of the catalyst H2SO4. If 80% conversion is to be achieved, determine the necessary reactor volume. How many 800-gal reactors would be required if they are arranged in parallel? What is the corresponding conversion? How many 800-gal reactors would be required if they are arranged i

26、n series? What is the corresponding conversion? The specific reaction rate constant is 0.311 min-1, as determined in Example 4-1.P142 例題4-2 用CSTR反應(yīng)器年產(chǎn)2億磅乙二醇（ Producing 200 million pounds per year in a CSTR） 1995年生產(chǎn)了近5.2109磅的乙二醇，在美國生產(chǎn)的化工品中排26位。約一半的乙二醇被用作防凍劑，而另一半被用于制造聚酯。在聚酯中，88%被用于合成纖維，而12%用于制造瓶子和膠片。乙

27、二醇1997年的售價為每磅0.38美元。 希望每年生產(chǎn)200百萬磅乙二醇，反應(yīng)器等溫操作。濃度為1 lb mol/ft3的環(huán)氧乙烷水溶液A與等體積含有0.9 wt% 硫酸催化劑的水溶液一起進(jìn)入反應(yīng)器。如果達(dá)到80%的轉(zhuǎn)化率，確定反應(yīng)器體積。如果反應(yīng)器并聯(lián)排布，需要多少個800加侖的反應(yīng)器？相應(yīng)的轉(zhuǎn)化率為多大？如果反應(yīng)器以串聯(lián)方式排布，需要幾個800加侖的反應(yīng)器？相應(yīng)的轉(zhuǎn)化率又為多少？反應(yīng)速率常數(shù)為0.311 min-1，與例題4-1測定的一致。SolutionAssumption: Ethylene glycol is the only reaction product formed.The

28、specified production rate in lb mol/min isFrom the reaction stoichiometry We find the required molar flow rate of ethylene oxide to be 1 lb = 454gWe can now calculate the reactor volume using the following equations:l. Design equation for CSTR2. Rate law3. Stoichiometry. Liquid phase ( = o =0) 4. Co

29、mbining The entering volumetric flow rate of stream A, with before mixing, isFrom the problem statement BO =AOThe total entering volumetric flow rate of liquid is1 ft3 = 28.32 dm35. Substituting in Equation (E4-2.4), recalling that k = 0.311 min -1, yieldsA tank 5 ft in diameter and approximately l0

30、 ft tall is necessary to achieve80% conversion. 6. CSTRs in parallel. For two 800-ga1 CSTRs arranged in parallel with 7.67ft3/min (0/2 ) fed to each reactor, the conversion achieved can be calculated from7. CSTRs in series. If the 800-ga1 CSTRs are arranged in series, the conversion in the first rea

31、ctor isWhere The same result could have been obtained from equation (4-11) Example 4-3 Neglecting Volume Change with ReactionThe gas phase cracking reaction: A 2B + C is to be carried out in a tubular reactor. The reaction is second-order and the parameter values are the same as those used to constr

32、uct Figure 4-7. If 60% conversion is desired, what error will result if volume change is neglected in sizing the reactor? ( 本來有體積變化，但忽略體積變化，取 = 0) Solution In Figure E4-3.1 (taken from Figure 4-7), we see that a reactor length of 1.5 m is required to achieve 60% conversion for = 0However, by correct

33、ly accounting for volume change = (1)(2+1-1)= 2 , we see that a reactor length of 5.0 m would be required. If we had used the 1.5-m-long reactor, we would have achieved only 40% conversion. P149 例4-3 反應(yīng)膨脹性對體積的影響（Neglecting volume change with reaction)氣相裂解反應(yīng)：A 2B + C 在管式反應(yīng)器內(nèi)進(jìn)行，反應(yīng)為二級，有關(guān)參數(shù)同圖4-7，如果轉(zhuǎn)化率為6

34、0%，在計算反應(yīng)器體積時，如果忽略反應(yīng)過程的體積變化（即認(rèn)為 = 0），計算誤差有多大？對于該反應(yīng)，反應(yīng)過程的膨脹因子為： = 2。考慮膨脹因子時 計算出的反應(yīng)器體積為5m。不考慮膨脹因子時 計算出的反應(yīng)器體積為1.5m。兩者相差三倍多。P148 圖4-7：膨脹因子對反應(yīng)器體積的影響P149 圖E4-3.1：膨脹因子對反應(yīng)器體積影響Example 4-4 Producing 300 million pounds per year of ethylene in a PFR: Design of a full-scale tubular reactorEthylene ranks fourth i

35、n the United States in total pounds of chemicals produced each year and it is the number one organic chemical produced each year.Over 35 billion pounds were produced in 1997 and sold for $0.25 per pound. Sixty-five percent of the ethylene produced is used in the manufacture of fabricated plastics （塑

36、料）, 20% for ethylene oxide （環(huán)氧乙烷）and ethylene glycol （乙二醇）, 5% for fibers （纖維）, and 5% for solvents （溶劑，如乙醇、乙醚等）.Determine the PFR volume necessary to produce 300 million pounds of ethylene a year from cracking a feed stream of pure ethane. The reaction is irreversible and follows an elementary rate

37、 law. We want to achieve 80% conversion of ethane, operating the reactor isothermally at 1100K （827）at a pressure of 6 atm.A B + C 當(dāng)轉(zhuǎn)化率為80%時，為了生產(chǎn)0.34 lb mol/s的乙烯，所需的乙烷進(jìn)料摩爾流率： 活化能為82kcal/g mol。 決定采用直徑為2英寸長度為40英尺的80號管子平行排布，管子的橫截面積為0.0205平方英尺。需要的管子數(shù)目為：最后，取100根管子用于實際生產(chǎn)。轉(zhuǎn)化率和濃度隨反應(yīng)器長度變化的關(guān)系曲線4.4 Pressure dr

38、op in the reactorsIn liquid phase reactions, the concentration of reactant is insignificantly affected by even relatively large changes in the total pressure. Consequently, we can totally ignore the effect of pressure drop on the rate of reaction when sizing liquid phase chemical reactors. However,

39、in gas phase reactions, the concentration of the reacting species is proportional to the total pressure and consequently, proper accounting for the effects of pressure drop on the reaction system can, in many instances, be a key factor in the success or failure of the reactor operation.CAPT關(guān)系：考慮壓降時，

40、PBR填充床反應(yīng)器等溫操作時，催化劑重量W與轉(zhuǎn)化率X之間的關(guān)系:Please see p161, eq (4-37)W = catalyst weightthe other parameters were used before.is from following eq(p158-159) P0 = pressure at entrance of reactor = porosity 空隙率Dp = diameter of catalyst particleViscosity of gas passing through the bedc = gas density氣體密度，lb/ft3G=

41、c u=superficial mass velocity 單位橫截面積 的質(zhì)量流率Ac = cross sectional area反應(yīng)過程組合(p175)乙烯在美國每年生產(chǎn)的化學(xué)品名列第四，并且占據(jù)每年生產(chǎn)的有機(jī)化學(xué)品的第一位。1997年的乙烯產(chǎn)量超過350億磅，售價為每磅0.25美元。生產(chǎn)的乙烯中65%用于制造塑料，20%用于生產(chǎn)環(huán)氧乙烷和乙二醇，5%用于生產(chǎn)纖維，5%用作溶劑。通過純乙烷裂解每年生產(chǎn)3億磅的乙烯，確定所需的活塞流反應(yīng)器體積。反應(yīng)為不可逆反應(yīng)，遵循基元反應(yīng)速率方程。希望獲得80%的乙烷轉(zhuǎn)化率，反應(yīng)器在6大氣壓，1100K的條件下等溫操作。P149 例4-4 乙烷裂解制乙烯

42、管式反應(yīng)器設(shè)計4.6 Spherical packed bed reactorsWhen small catalyst pellets are required, the pressure drop can be significant. In example 4-6, we saw that significant design flaws can result if pressure drop is neglected or if steps are not taken to minimize pressure drop. One type of reactor that minimize

43、s pressure drop and is also inexpensive to build is the spherical reactor, （還有一個優(yōu)點(diǎn)是反應(yīng)器受力均勻）shown in Figure 4-8. In this reactor, called an ultra-former(重整), dehydrogenation （脫氫） reaction such as paraffin aromatic + 3 H2 is carried out. 圖4-8 球形重整反應(yīng)器（得到Amoco石油公司的許可），該反應(yīng)器為Amoco公司用于石腦油重整的六個串聯(lián)反應(yīng)器中的一個，K.

44、R. Renicker, Sr. 攝影。球型填充床反應(yīng)器4.6.2 Membrane ReactorsBy having one of the products pass throughout the membrane, we drive the reaction towards completion.有利于可逆反應(yīng)的進(jìn)行完全Catalytic membrane reactors can be used to increase the yield of reactions that are highly reversible over the temperature range of inte

45、rest. (some refer to this type of reaction as being thermodynamically limited) The term membrane reactor describes a number of different types of reactor configurations that contain a membrane. The membrane can either provide a barrier to certain components, while being permeable to others, prevent

46、certain components such as particulates from contacting the catalyst, or contain reactive sites and be a catalyst in itselfLike reactive distillation, the membrane reactor is another technique for driving reversible reactions to the right in order to achieve very high conversions.These high conversi

47、ons can be achieved by having one of the reaction products diffuse out a semipermeable membrane surrounding the reacting mixture. As a result, the reaction will continue to proceed to the right toward completion.Membrane Reactor膜反應(yīng)器 據(jù)能源部估算，對諸如乙苯脫氫生產(chǎn)苯乙烯和丁烷生產(chǎn)丁烯的脫氫反應(yīng)，如果用催化膜反應(yīng)器替代傳統(tǒng)的反應(yīng)器，每年將節(jié)約10萬億Btu的能量。

48、1. Mole Balance2、速率方程3.通過反應(yīng)器壁的擴(kuò)散速率3. Stoichiometry 化學(xué)計量學(xué) 聯(lián)立求解上述方程組，四個方程，四個未知數(shù)（FA, FB, FC, FT, ），V是自變量Semibatch Reactors 半間歇反應(yīng)器 For A it is a batch reactor, for B it is a continues reactorMole balance for A：流入速率流出速率+產(chǎn)生速率=積累速率 (For liquid)Mole balance for B：求解微分方程組，可得到CAt和CBt 關(guān)系例題4-11 進(jìn)行二級反應(yīng)的等溫半間歇反應(yīng)器甲

49、基溴的生產(chǎn)為一個遵循基元反應(yīng)速率方程的不可逆液相反應(yīng)。反應(yīng)：在一個半間歇反應(yīng)器中等溫進(jìn)行。將濃度為0.025 g mol/dm3的甲胺（B）水溶液，以0.05dm3/s的流率加入到一個玻璃襯里的反應(yīng)器中的溴化氰（A）水溶液里。反應(yīng)器中流體的初始體積為5dm3，該流體是濃度為0.05 mol/dm3的溴化氰。指定的反應(yīng)速率常數(shù)為：求解作為時間函數(shù)的溴化氰濃度、甲胺濃度和反應(yīng)速率。Recycle Reactors 循環(huán)反應(yīng)器 1)對于自催化反應(yīng)，即產(chǎn)物有催化作用2）為了維持反應(yīng)器接近等溫操作3）為了達(dá)到一定的選擇性時需要使用循環(huán)反應(yīng)器，它們也被廣泛地應(yīng)用于生化反應(yīng)過程中 Reactive Dist

50、illation 反應(yīng)精餾The distillation of chemically reacting mixtures has e increasingly common in chemical industry. Carrying out these two operations, reaction and distillation, simultaneously in a single unit results in significantly lower capital and operation costs. Reactive distillation is particularl

51、y attractive when one of the reaction products has a lower boiling point, resulting in its volatilization from the reacting liquid mixture. An example of reactive distillation is the production of methyl acetate:By continually removing the volatile reaction product, methyl acetate, from the reacting

52、 liquid-phase reaction, the reverse reaction is negligible and the reaction continues to proceed towards completion in the forward direction.Although reactive distillation will not be treated in detail, it is worthwhile to set down the governing equations. We consider the elementary reaction 在該反應(yīng)中A和

53、B被等摩爾加入，且組分D不斷地被蒸發(fā)出來。組分A的摩爾衡算方程為： （4-75）對于前面介紹的四種反應(yīng)器（membrane, semibatch, recycle, Reactive Distillation）, We can use general mole balance to get the design equation:Unsteady state operation of reactorsIn this chapter we have already discussed the unsteady operation of one type of reactor, the batch

54、 reactor. In this section we discuss two other aspects of unsteady operation. First, the startup of a CSTR is examined to determine the time necessary to reach steady-state operation. Next semi-batch reactors are discussed. In each of this cases, we are interested in predicting the concentration and

55、 conversion as a function of time. Closed-form analytical solutions to the differential equations arising from the mole balance of these reaction types can be obtained only for zero- and first-order reactions. (a)CSTR連續(xù)操作時的開工階段，CA隨時間是變化的，過一段時間后CA將不再變化，達(dá)到某一常數(shù)，此后便為穩(wěn)態(tài)操作。(b)A事先一次性加入，B連續(xù)地進(jìn)入反應(yīng)器，A不斷減少，反應(yīng)器內(nèi)

56、物料不斷減少，直到A完全消失，整個過程對A為非穩(wěn)態(tài)操作。(c)反應(yīng)物A、B一次性加入，但產(chǎn)物不斷地連續(xù)離開反應(yīng)器，反應(yīng)器內(nèi)的物料不斷減少，直至完全消失，這也屬于非穩(wěn)態(tài)操作。以上具體計算時，利用Mole Balance Eq.: in out + generated = accumulated用ts表示達(dá)到穩(wěn)態(tài)濃度=99% CA時所需要的時間，穩(wěn)態(tài)濃度CAS為：當(dāng)CA=0.99CAS時重新整理方程（4-46）得到： HomeworkP4-7A The elementary gas-phase reaction（今年不布置）(CH3)3COOC(CH3)3 C2H6 + 2CH3COCH3is c

57、arried out isothermally in a flow reactor with no pressure drop. The specific reaction rate at 50oC is 10-4 min-1 (from preciosity data) and the activation energy is 85 kJ/mol. Pure di-tert-butyl peroxide enters the reactor at 10 atm and l27oC and a molar flow rate of 2.5 mol/min. Calculate the reac

58、tor volume and space time to achieve 90% conversion in:(a) a CSTR (b) a PFR (c) If this reaction is to be carried out isothermally at l27oC and an initial pressure of l0 atm in a batch mode with 90% conversion, what reactor size and cost would be required to process (2.5 mol/min60 min/h24 h/day)3600

59、 mol of di-tert-butyl peroxide per day? (Hint: Recall Table 4-1.)（不考慮裝料、卸料、清洗的時間）（只計算reactor size, 不考慮cost，只做a),b),c)）(d) Assume that the reaction is reversible with Kc = 0.025 mol2/dm6 and calculate the equilibrium conversion and then redo (a) through (c) to achieve a conversion that is 90% of the

60、equilibrium conversion.(e) What CSTR temperature would you mend for a 500-dm3 CSTR to obtain the maximum conversion if HRx = - l00, 000 cal /mol?(Hint: Remember that the equilibrium conversion will be different for a flow reactor and a constant-vo1ume batch reactor for a gas-phase reaction that has