a) Suppose a reactant A undergoes liquid-phase reactions according to the follow
ID: 554146 • Letter: A
Question
a) Suppose a reactant A undergoes liquid-phase reactions according to the following kinetics scheme Reaction Desired?Rate law Activation ener AB 2 A C A3 i) Does a favorable product distribution result from relatively high or relatively low Ca? Explain. ii) Does a favorable product distribution result from relatively high or relatively low T? Explain. ii) Does a favorable (i.e., small) reactor size result from high or low CA? Explain iv) Does a favorable reactor size result from high or low T? Explain. v) Which type of reactor, PFR or single-staged CSTR, should be chosen for this situation, and should it be operated at high, low, or optimal T to achieve favorable product distribution consistent with small size of reactor? Explain. b) For the kinetics scheme in (a), and regardless of the proper choice of reactor, suppose a CSTR of volume 10 m3 is available to process 0.5 m /min of a feed stream with a concentration (Ca) of 3000 mol/m3. If the temperature is such that k1 = 0.001 (1/sec), and k2= 5*105 m3/mol/sec, calculate the fractional conversion of A and the product distribution (Ca, Cs, C) in the exit stream at steady stateExplanation / Answer
1) The equation for the desired product goes like r = K * Ca2 , the one for the undesired one goes like r = K * Ca, as you can see you have a squared term for Ca for the desired product so if you double the concentration of Ca the rate of reaction for the desired product will be multiplied by 4 (which is good) so a high concentration of Ca favors the products
2) as we can see the energy of activation of the undesired products is higher than the one of the desired products, this is that the reaction of the undesired products need more energy to acomplish the reaction, if you increase the temperature the number of molecules that can carry the energy required also increases, for this particular case if you put too much temperature into the system the undesired reaction will start, so for this one you will be favored by a relaitively low Temperature.
3) a favorable size of reactor results from a high Ca
the volume of reactor for a cstr goes like this:
V = Fao*X / -ra , since ra = KCa2 , the volume mathematically will decrease as the denominator (-ra) increases
for a plug flow reactor the equation is similar the ra is a denominator
4 . the rate constant K increases as the temperature goes up, this is because the number of molecules with the energy of activation increases and the reaction is easier to start the reaction also it will be faster, so the rate of reaction ra also increases, the the analysis is very similar to the one made in the last point, since the ra is a denominator, the volume will be decreased as the K increases so the size of the reactor will be favorable with a hight Temperature
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.