Page 102 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

c. the yield of styrene.

Suggest one strategy to increase the yield of styrene, and sketch any changes to the PFD that this
strategy would require.

There are two technically viable routes to the production of a hydrocarbon solvent, S, starting with
feed material A. Route 1 uses a disproportionation reaction, in which feed material A is converted to
the desired solvent S and another solvent R, both of which are marketable products. Route 2 starts
with the same chemical A, but uses a hydrodealkylation reaction to produce the desired solvent. The
reaction schemes for each process are shown below.

11.
Route 1 2A → S + R
Route 2 A + H → S + CH
2 4

Assuming that pure A is fed to the process, the solvents S and R are separable by simple distillation,

and both are much less volatile than either methane or hydrogen, sketch PFDs for Routes 1 and 2.
Which process do you think will be more profitable? Explain your reasoning and assumptions.

When considering the evolution of a process flowsheet, it was noted that there are three forms of
recycle structure for unused reactants, given as a–c below. For each case, carefully explain under
what conditions you would consider or implement each strategy.

12. a. Separate, purify, and recycle.

b. Recycle without separation and use a purge.

c. Recycle without separation and do not use a purge.

Acetaldehyde is a colorless liquid with a pungent, fruity odor. It is primarily used as a chemical
intermediate, principally for the production of acetic acid, pyridine and pyridine bases, peracetic
acid, pentaeythritol, butylene glycol, and chloral. Acetaldehyde is a volatile and flammable liquid
that is miscible in water, alcohol, ether, benzene, gasoline, and other common organic solvents. In
this problem, the synthesis of acetaldehyde via the dehydrogenation of ethanol is to be considered.
The following reactions occur during the dehydrogenation of ethanol:

(1)

(2)