dos Materiais e MetalurgiaDepartamento de Ciência Cinética e Engenharia de Reatores Lista 6 Professor: Francisco Moura Bibliografia: Fogler, H. S., Elementos de Engenharia das Reações Químicas, 3a edição, Editora LTC, 2002. 1 Sexta Lista de Exercício P5-2 Exercí Exercícios P5-2A The irreversible isomerization A→B was carried out in a batch reactor and the following concentration-time data were obtained: dos Materiais e Metalurgia Departamento de Ciência t (min) 0 5 8 10 12 15 17.5 20 CA (mol/L) 4.0 2.25 1.45 1.0 0.65 0.25 0.06 0.008 Determine the reaction order and specific reaction rate. 2 Sexta Lista de Exercício P5-3 Exercí Exercícios P5-3B GaInAs films are important materials in fiber optic communication and in high-speed microelectronic devices. A preliminary reaction between triethylindium and arisine is carried out to form an intermediate, which is then used in the deposition to form GaInAs. dos Materiais e Metalurgia Departamento de Ciência The reaction is Et3In(g) + AsH3(g) ↔ Adduct (g) The following data were obtained in a plug-flow reactor. [JECS 135 No.6 p.1530 (1988)]. Total pressure (including inerts) = 152.0 Torr. Distance Down Reactor (cm) 0 1.5 2.5 4.0 6.5 9.0 For AsH3 = 1.5 Torr Inlet Et3In (Torr) 0.129 0.075 0.05 0.03 0.018 0.016 For AsH3 = 0.25 Torr Inlet Et3In (Torr) 0.129 0.095 0.085 0.08 0.042 0.04 For AsH3 = 3.0 Torr Inlet 3 Et3In (Torr) 0.129 0.045 0.022 0.01 0.01 0.01 Sexta Lista de Exercício P5-4 Exercí Exercícios P5-4B The following data were reported [C. N. Hinshelwood and P. J. Ackey, Proc. R. Soc. (Lond)., A115, 215 (1927).] for a gas- phase constant-volume decomposition of dimethyl ether at 504°C in a batch reactor. Initially, only (CH3)2O was present. dos Materiais e Metalurgia Departamento de Ciência Time (s) 390 777 1195 3155 ∞ Total Pressure (mmHg) 408 488 562 799 931 Assuming that the reaction (CH3)2O → CH4 + H2 + CO is irreversible and goes to completion, determine the reaction order and specific reaction rate k. 4 Sexta Lista de Exercício P5-5 Exercí Exercícios P5-5B In order to study the photochemical decay of aqueous bromine in bright sunlight, a small quantity of liquid bromine was dissolved in water contained in a glass battery jar and placed in direct sunlight. The following data were obtained: dos Materiais e Metalurgia Departamento de Ciência Time (min) 10 20 30 40 50 60 ppm Br2 2.45 1.74 1.23 0.88 0.62 0.44 temperature = 25oC (a) Determine whether the reaction rate is zero-, first-, or second-order in bromine, and calculate the reaction rate constant in units of your choice. (b) Assuming identical exposure conditions, calculate the required hourly of rate of injection of bromine (in pounds) into a sunlit body of water, 25,000 gal in volume, in order to maintain a sterilizing level of bromine of 1.0 ppm. (Note: ppm = parts of bromine per million parts of brominated water by weight. In dilute aqueous solutions, 1 ppm = 1 milligram per liter.) 5 (California Professional Engineers Exam) Sexta Lista de Exercício P5-6 Exercí Exercícios P5-6C Triaminoguanidine (TAGN) is an important propellent ingredient which is used as an oxidizer. It can be produced from guanidine (GN) and hydrazine in an aqueous solution [Ind. Eng. Chem. Res. 28 p.431 (1989)]. The reaction is dos Materiais e Metalurgia GN + 3N2H4 → TAGN + 3NH3 ↑ Departamento de Ciência The following data give the cumulative ammonia evolved as a function of time. The initial concentrations of GN and hydrazine were 0.5 molar and 2.575 molar, respectively, in a 200 ml batch reactor. Neglect any volume change in the liquid with reaction for this aqueous reaction. At 371K Time (min) 0 5 10 20 30 40 50 60 80 100 150 NH3 (milimoles) 0 38 69 95 116 151 177 213 237 264 279 At 351K Time (min) 0 5 10 20 30 40 50 60 80 100 150 NH3 (milimoles) 0 30 55 97 130 154 174 190 216 234 263 6 Determine as many rate law parameters as possible. Sexta Lista de Exercício P5-7 Exercí Exercícios P5-7C The reactions of ozone were studied in the presence of alkenes [R. Atkinson et al., Int. J. Chem. Kinet. 15(8), 721 (1983)]. The data below are for one of the alkenes studied, cis-2-butene. The reaction was carried out isothermally at 297 K. Determine the rate dos Materiais e Metalurgia law and the values of the rate-law parameters. Departamento de Ciência Ozone Butene Ozone Rate Run Concentration Concentration (mol/s.dm3 x 107) (mol/dm3) (mol/dm3) 1 1.5 0.01 10-12 2 3.2 0.02 10-11 3 3.5 0.015 10-10 4 5.0 0.005 10-9 5 8.8 0.001 10-8 6 4.7 0.018 10-9 7 Sexta Lista de Exercício P5-8 Exercí Exercícios P5-8c Examples of autocatalytic reactions can be found in methanol conversion [Ind. Eng. Chem. Res. 27 p.942 (1988)], the preparation of Raney Nickel Catalysts [Ind. Eng. Chem. Res. 28, p. 33 (1989)], the disproportionation of potassium benzoate, [Ind. Eng. Chem. Res. 27 p.947 (1988)], and in bioreactors. Consider dos Materiais e Metalurgia Departamento de Ciência the following elementary reaction sequence as a model system for autocatalytic reactions: k 1 A →B k2 A + B → 2B The conversion of A as a function of space time in a packed-bed reactor for conversion methanol is τ, seconds 0 0.042 0.062 0.1 χ 0 0.06 0.13 0.38 Pure A enters at a concentration of 0.05 mol/dm3. (a) Estimate k1 and k2. (b) At what conversion and space time is the rate of disappearance of A a maximum. 8 (c) Plot the concentrations of A and B as a function of space time. Sexta Lista de Exercício P5-9 Exercí Exercícios P5-9A Tests were run on a small experimental reactor used for decomposing nitrogen oxides in an automobile exhaust stream. In one series of tests, a nitrogen stream containing various concentrations of NO2 was fed to a reactor and the kinetic data dos Materiais e Metalurgia obtained are shown in Figure P5-9. Each point represents one Departamento de Ciência complete run. The reactor operates essentially as an isothermal backmix reactor (CSTR). What can you deduce about the apparent order of the reaction over the temperature range studied? The plot gives the fractional decomposition of NO2 fed versus the ratio of reactor volume V (in cm3) to the NO2 feed rate, FNO2,0 (g- mol/h), at different feed concentrations of N02 (in parts per million by weight). 9 Sexta Lista de dos Materiais e Metalurgia Exercício P5-9 (continuação) Exercí Exercícios Departamento de Ciência 10 Sexta Lista de Exercício P5-10 Exercí Exercícios P5-10B Penicillin G reacts with hydroxylamine (NH2OH) to form hydroxamic acid, which produces a colored complex with iron (III). To determine the overall reaction order, equal concentrations of penicillin and NH2OH were mixed together in a 250-ml flask [J. dos Materiais e Metalurgia Chem. Educ., 49, 539 (1972)]. Samples were withdrawn every 10 Departamento de Ciência minutes and added to a solution containing iron (III) chloride. With the aid of a colorimeter, the concentration of the colored complex, and hence the concentration of hydroxamic acid, was obtained as a function of time. The absorbance shown in the table below is directly proportional to the hydroxamic acid concentration. Time (min) 0 10 20 30 40 50 ∞ Absorbance 0.00 0.337 0.433 0.495 0.539 0.561 0.685 Determine the overall order of reaction assuming that the reaction is irreversible. (Ans.: Second-order.) 11