Gazi University Faculty of Engineering and Architecture Department of Chemical Engineering ChE 341 Chemical Reaction Engineering Dr. Çiğdem GÜLDÜR Assist. Saliha KILIÇARSLAN (İ.Ö-02) PROBLEM SET-2 Batch Reactors 2R takes place at 40oC and 3 atm in batch reactor. Initially, there are 1. The reaction A 85%A and inert. Time,s Volume, ml 0 200 30 251 60 276 120 302 240 324 Show that the reaction is second order and find the rate constant. 2. Dimethylether in a gaseous phase decomposes according to the following reaction. CH3OCH3 (A) CH4+CO+H2 (B) (C) (D) Data were obtained from isothermal constant volume batch reactor at 552oC. Time, sec Total pressure, mmHg 0 420 57 584 85 662 114 743 182 891 261 1013 299 1054 Show that the reaction is first order according to the reactant and find the rate constant. 3. The reaction A+B C was studied in a constant volume batch reactor. The reaction is believed to be first order in each reactant and second order overall. The following data were reported for their experiments at 20oC. The initial concentration of B was 0.123 kmol/m3. CA,kmol/m3 0.106 t,sec 0 0.099 150 0.087 480 0.076 870 0.062 1500 0.050 2280 Are these data consistent with the proposed rate expression? If so, determine the reaction rate constant. 4. Data for the dimerization 2A solution at 40oC follow: CA (mmol/dm3) t (min) 68.0 0 50.2 40 A2 of a certain nitrile oxide(compound A) in ethanol 40.3 80 33.1 120 28.4 160 22.3 240 18.7 300 14.5 420 Find the reaction order using the half- life method. 5. Determine the reaction order for the gas-phase deposition of di-tert-butl peroxide, (CH3)3COOC(CH3)3 C2H6 + 2CH3CCH3 O The reaction was carried out in the laboratory in an isotermal batch system in which the total pressure was recorded at various times during the reaction the data given in table apply to this reaction. Only pure di-tert-butly peroxide was initially present in the reactin vessel. Time (min) 0.0 2.5 5.0 10.0 15.0 20.0 Total Pressure (mmHg) 7.5 10.5 12.5 15.8 17.9 19.4 6. Problems 3.15&3.25 The textbook: Levenspiel O., “Chemical Reaction Engineering”,3rd ed.(1999). 7. The rate of decomposition of nitrogen pentaoxide in the inert solvent CCl4 can be followed by measuring the volume of the O2 evolved at a given temperature and pressure since the unreacted N2O5 and the other products of the decomposition remain in solution. Some results at 45oC from batch reactor are as follows: t(sec) O2 evolved(cm3) 162 3.41 407 7.78 1721 23 3400 29.33 32.6 Show that the reaction is first order find the first order rate constant. N2O5 N2O4+1/2O2. Assume reaction goes to completion. 8. Neyens has studied the bromination of metaxylene at 17oC. the reaction is carried out by introducing small quantities of iodine and bromine into pure liquid xylene and the following the rate of disappearance of bromine by titrating samples removed from the liquid to determine their bromine content. The iodine serves as a catalyst for the reaction. Since the concentration of xylene and catalyst remain essentially unchanged during the course of reaction, it may be assumed that the rate expression is of the form r=kCBrm=-dCBr/dt where k is pseudo rate constant that will depend on the iodine and xylene concentrations. Determine the order of the reaction and reaction rate constant t(min) 0.00 4.5 8.0 12.0 17.85 27.0 38.0 45.0 Bromine 0.3335 0.2660 0.2255 0.1910 0.1500 0.1160 0.0830 0.0705 concentration(mol/L) 9.The following gas phase reaction was studied in a constant volume batch reactor at 1030K. A B a)Find the order of the reaction and the reaction rate constant at 1030K. The data as follows: PAO(mmHg) t1/2(s) 82.5 860 139 470 296 255 360 212 b)Calculate the activation energy by using the folowing data. Temperature(K) 1085 1030 967 PA0(mmHg) 345 360 294 t1/2(s) 53 212 1520 10. The reaction 2NO+2H2 N2+2H2O was studied in a constant volume batch reactor with equimolar quantities of NO and H2 at various initial pressures: PO(kPa) t1/2(s) 47.2 81 45.5 102 50.0 95 38.4 140 33.5 180 32.4 176 26.9 224 Calculate the over all order of the reaction. CSTR&PFR 11. The liquid phase irreversible reaction A B+C İs carried out in a CSTR . the volumetric flow rate 0(hence =V/0) is varried to determine the rate law and the effluent concentrations of species A recorded as a function of the space time . Pure A enters the reactor at a concentration of 2 mol/L. Steady state conditions exist when the measurements are recorded. Run (min) CA (mol/L) 1 15 1.5 2 38 1.25 3 100 1.0 4 300 0.75 5 1200 0.5 Determine the reaction order and specific reaction rate. 12. Balasubramanian, Rihani and Doraiswamy have studied the reaction of ethylene and chlorine in liquid ethylene dichloride solution in a CSTR. The stoichiometry of the reaction is C2H4+Cl2 C2H4Cl2 Equimolar flow rates of ethylene and chlorine were used in the following experiment, which was carried out at 32oC. 0 (sec) Effulent chlorine 0.0117 concentration(moles/cm3) 300 0.0095 600 0.0082 900 0.0072 1200 0.0065 1500 0.0060 a) Determine the overall order of the reaction and the reaction rate constant. b) Determine the space time necessary for 75% conversion in CSTR. c)What would be the conversion in PFR having the space time determined in part b. 1800 0.0057 In part b and c assume that the operating temperature and the initial concentrations are the same as in part a. 13. A chemical reaction is being studied in a laboratory scale steady-state flow system.the reactor is a well-stirred 1000cm3 flask containing an aqueous solution. The reactor contents (1000cm3 of solution) are uniform troughout. The stochiometric equation and data are given below. What is the expression for the rate of the this reaction?Determine the reaction order and the activation energy? Diacetal+H2O Aldehyde+2Alcohol Feed Rate(cm3/sec) Run 1 2 3 0.5 3.0 3.0 Temperature,T(OC) 10 10 25 Concentration of Aldehyde in effluent(kmoles/m3) 0.75 0.5 0.75 Feed concentration of diacetal is 1 kmole/m3. (Data are hypothetical. The reaction may be assumed to be zero-order in aldehyde and alcohol and apparently zero order in water) 14. Decomposition reaction (CH3CHO(g) CH4(g)+ CO(g)) of acetaldehyde was investigated at 518 OC and 1 atm. pressure in a plug flow reactor by changing feed rate. The reactor has 3.3 cm inner diameter and 80 cm length. Data are given below for the reaction: Feed rate(g/L) Conversion of acetaldehyde 130 0.05 50 0.13 21 0.24 10.8 0.35 Show the reaction is second order and find reaction rate constant.(molecular weigh of acetaldehyde:44 g/mole) 15. Problem 5.19 The textbook: Levenspiel O., “Chemical Reaction Engineering”,3rd ed.(1999).