This set of Unit Processes Multiple Choice Questions & Answers (MCQs) focuses on “Factors Controlling Alkylation”.
1. Which one of the following is a physical property?
a) Heat of formation
b) Vapour pressure
c) Heat of vaporization
d) All of the mentioned
View Answer
Explanation: The physical properties in a reaction are vapour pressure, viscosity, PVT relationship etc.
2. Carbon alkylations are generally endothermic.
a) True
b) False
View Answer
Explanation: Carbon alkylations are generally exothermic reaction.
3. Which catalyst is/are used when aromatic hydrocarbons are alkylated with olefins?
a) Protonic acid
b) Anionic acid
c) Both protonic and anionic acid
d) None of the mentioned
View Answer
Explanation: Either Friedel-Crafts or protonic acid catalysts are often used when liquid isoparaffins or aromatic hydrocarbons are alkylated with olefins.
4. What is the role of hydrogen chloride when used with aluminium chloride?
a) Increase basicity
b) Decreases acidity
c) Increase acidity
d) None of the mentioned
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Explanation: The role of hydrogen chloride when used with aluminium chloride is to increase the acidity of the catalyst and hence make it more effective.
5. What side reactions occur during the catalytic alkylation of isoparaffins?
a) Polymerization
b) Isomerization
c) Hydrogen transfer
d) All of the mentioned
View Answer
Explanation: Side reactions such as polymerization, isomerization, hydrogen transfer, and destructive alkylation occur during the catalytic alkylation of isoparaffins and aromatics with olefins.
6. Polymerization can be minimized by using large excesses of isoparaffins.
a) True
b) False
View Answer
Explanation: Polymerization is minimized by using relatively large excesses of isoparaffins or aromatics. Normal paraffins are not generally alkylated satisfactorily using catalysts.
7. Paraffins can be alkylated at what temperature?
a) Low
b) Moderate
c) High
d) None of the mentioned
View Answer
Explanation: Paraffins can be alkylated in the absence of catalysts at sufficiently high temperatures, about 500°C, so that a small amount of the paraffins will decompose into free radicals.
8. What happens when high temperatures used in thermal alkylation?
a) Cracking
b) Dehydrogenation
c) Isomerization
d) All of the mentioned
View Answer
Explanation: Because of the relatively high temperatures used in thermal alkylation, some cracking, dehydrogenation, and isomerization of the hydrocarbons occur in most cases.
9. Why do we need to dilute energetic alkylating agents?
a) Fast reaction
b) Control reaction
c) High temperature
d) All of the mentioned
View Answer
Explanation: For certain energetic alkylating agents, it is advantageous frequently to dilute them in order better to control the reaction.
10. For which alkylating agent high temperature is needed?
a) Methanol
b) Ethyl alcohol
c) Alkyl halides
d) All of the mentioned
View Answer
Explanation: When such alkylating agents as methanol, ethyl alcohol, or the alkyl halides are employed, a much higher temperature is necessary than that required with dimethyl sulphate or diethyl sulphate or even methyl p-toluenesulfonate.
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