250+ TOP MCQs on Synthetic Organic Chemical – Phthalic Anhydride and Answers

Chemical Industry Question Bank on “Synthetic Organic Chemical – Phthalic Anhydride”.

1. How is phthalic anhydride manufactured?
a) Dehydrogenation of ethyl benzene
b) Hydrogenation dehydration of acetophenone
c) Benzene sulphurated process
d) Oxidation of naphthalene

Answer: d
Clarification: 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. How is the heat of reaction removed during the manufacture of phthalic anhydride?
a) Aqueous salt
b) Molten salt
c) NaOH
d) KCl

Answer: b
Clarification: 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. Can manufacture of phthalic anhydride from oxidation of naphthalene be improved?
a) Yes
b) No

Answer: a
Clarification: 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. Increasing the contact time in oxidation of naphthalene yields better quality of phthalic anhydride.
a) True
b) False

Answer: a
Clarification: 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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