Page 101 - The engineering of chemical reactions

Problems 85
2.20 Nitric acid is made from methane by first reacting CH4 with Hz0 to form syngas. Water is added
to the CO + Hz mixture to form Hz and CO* which is easily separated. Hydrogen is reacted
with N2 from a liquid air plant. Ammonia is oxidized to NO over a Pt catalyst, and additional
air is added to form N02, and the product is dissolved in water.
(a) Write out the reactions in this process.
(b) Sketch a flowsheet of a nitric acid plant.

2.21 Polyacrylonitrile is an important polymer for carpets and for vapor barrier films in food
packaging.
(a) Until approximately 1975 most acrylonitrile was made by reacting acetylene with HCN.
Acetylene is made by dehydrogenation of ethane. HCN is made by reacting CH4, NHs, and
air over a Pt catalyst. Write out these reactions.
(b) In the 1970s Sohio (now British Petroleum) discovered a process by which propylene and
NH3 react over a bismuth molybdate catalyst in a process called ammoxidation to make
acrylonitrile in one step in a fluidized bed reactor. Now nearly 100% of acrylonitrile is made
by this process. Write out this reaction.
2.22 Alpha olefins with typically 12 C atoms have wide use as detergents, polymer additives, and
many other chemicals. These a-olefins (linear molecules with the double bond only at the
end carbon) can be made by the oligomerization (dimerization) of smaller olefins starting with
ethylene or by successive carbonylation of smaller a-olefins. Write out these reactions, showing
why they do not produce branched alkyls or double bonds at other than the end position.

2.23 An irreversible aqueous reaction gave 90% conversion in a batch reactor at 40°C in 10 min and
required 3 min for this conversion at 50°C.
(a) What is the activation energy for this reaction?
(b) At what temperature can 90% conversion be obtained at 1 minute?
(c) Find the rate coefficient assuming first order kinetics.
(d) Assuming first order kinetics, find the times for 99% conversion at 40 and at 50°C.
(e) Assuming first order kinetics, find the temperature to obtain 99% conversion in a time of 1
minute.
(l) Assuming second order kinetics, find the times for 99% conversion at 40 and at 50°C.
(g) Assuming second order kinetics, find the temperature to obtain 99% conversion in a time
of 1 minute.