Page 98 - The engineering of chemical reactions

82 Reaction Rates, the Batch Reactor, and the Real World

2.6 (a) The previous process was found to have an activation energy of 12 kcal/mole, and we had
been operating at 40°C. What reactor volumes would we need if we can operate at 8O”C?
(b) This hydrolysis reaction is exothermic with AH, = -8 kcal/mole. What must be the
average rate of cooling (in watts) during the reaction to maintain the reaction isothermal?
(c) If we started the batch reactor at 40°C but forgot to turn on the cooling, what would be the
final temperature if the reactor were adiabatic (and the vessel would withstand the pressure)?
Assume the heat capacity of the solution to be that of water, 1 Cal/cm3 K.
(d) What cautions do you recommendations regarding operation at 8O”C?
2.7 An aqueous ester hydrolysis reaction A + B + C has k = 0.02 min-l and an equilibrium
constant of 10 with all concentrations in moles/liter.
(a) Starting with CA0 = 1 mole/liter, and C&, = Cc0 = 0, what is the equilibrium composition?
(b) What is the reverse rate constant in the above reaction?
(c) Find CA(I), C,(t), and Cc(t) in a batch reactor for these initial conditions.

2.8 (a) Sketch the steps, reactions, and flow sheet by which ethylene glycol is produced from ethane
by the direct oxidation process.
(b) Ethylene glycol was made by the chlorohydrin route until the 1960s when Union Carbide
and Shell Oil developed the direct oxidation process. In the chlorohydrin process hypochlor-
ous acid, HOCl, is reacted with ethylene to produce ethylene chlorohydrin. Then HCl is
eliminated and the product is hydrated. Sketch these reactions and the flow sheet, starting
from NaCI, ethane, water, air, and electricity.
(c) If the HCl must be disposed of by reacting it with NaOH, how many pounds of salt must be
disposed of per pound of ethylene glycol produced, assuming all reaction steps have 100%
efficiency?
(d) Write out the ethane to ethylene glycol reactions in our standard notation, c Vij Aj = 0, i =
1,2,. . , R.

2.9 Summarize the argument that all chemical energy sources are derived from solar energy. What
is the single chemical reaction and what is the catalyst by which all of this chemical energy is
produced? [Look it up in your biology text.] What is a reasonable definition of renewable and
nonrenewable energy sources? What is the major reaction by which CO2 is removed from and
added to the biological cycle?

2.10 Before synthetic polymers were developed to produce fibers and sheets, your ancestors found
many natural sources of polymers for clothing, housing, and tools. Make a list of these divided
into soft materials and hard materials and into one-dimensional and two-dimensional polymers.
List the source, uses, and chemical composition for each. Don’t forget violin bows, guitar
strings, writing surfaces, and wine jugs.

2.11 We have a process that reacts 67% Cl& in 02 at 10 atm to form syngas (A HR = -8.5 kcahmole
CH4).
(a) Estimate the adiabatic reactor temperature at completion if we produce 100% syngas with
a feed temperature of 400°C. Assume pC, = i R = 7 Cal/mole K.
(b) Estimate the adiabatic reactor temperature if we suddenly begin producing 100% total
combustion products (A HR = - 192 kcal/mole).