Engineering Questions with Answers - Multiple Choice Questions

Chemical Industry MCQ’s – Synthetic Organic Chemical – Phthalic Anhydride

1 - Question

How is phthalic anhydride manufactured?
a) Dehydrogenation of ethyl benzene
b) Hydrogenation dehydration of acetophenone
c) Benzene sulphurated process
d) Oxidation of naphthalene
View Answer Answer: d
Explanation: Naphthalene mixture are melted and vaporized later it undergoes conversion in a fixed bed converter. Dehydrogenation of ethyl benzene and Hydrogenation dehydration of acetophenone is used for the manufacture of styrene.

2 - Question

How is the heat of reaction removed during the manufacture of phthalic anhydride?
a) Aqueous salt
b) Molten salt
c) NaOH
d) KCl
View Answer Answer: b
Explanation: The exothermic heat of reaction is removed from the outside of the tubes by a molten salt circulating system. The condition for oxidation within the converter is 380 degree Celsius.

3 - Question

Can manufacture of phthalic anhydride from oxidation of naphthalene be improved?
a) Yes
b) No
View Answer Answer: a
Explanation: A process modification which competitive is a substitution of a fluid bed catalytic reactor for the fixed bed multi tubular reactor. Conditions at the head end are somewhat different.

4 - Question

Increasing the contact time in oxidation of naphthalene yields better quality of phthalic anhydride.
a) True
b) False
View Answer Answer: a
Explanation: A longer contact time of 10 seconds in a fluid bed catalytic reactor yields better product than a contact time of 0.1 – 0.4 seconds in a fixed bed multi tubular reactor. The yields are equivalent and almost no maleic acid if produced, thus giving very high purity phthalic anhydride product.

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