The most suitable reactor for carrying out an auto-thermal reaction is a

The correct answer is:

D. Plug-flow reactor

✅ Explanation:
An auto-thermal reaction is one in which the heat generated by the reaction is sufficient to maintain the reaction temperature without external heating or cooling. These are often highly exothermic reactions (e.g., combustion, partial oxidation, ammonia synthesis).

🔹 Why a Plug Flow Reactor (PFR) is most suitable:
Temperature Gradient Along the Length:

In a PFR, temperature and concentration vary along the reactor length, allowing for better heat management.

The heat released in the initial portion of the reactor can help preheat incoming reactants, supporting an auto-thermal profile.

Efficient Use of Heat:

Heat is not dissipated uniformly, so it can be locally used to maintain the desired reaction temperature.

High Conversion and Selectivity:

Particularly for exothermic reactions, a PFR helps in achieving higher conversions with better control over runaway reactions.

❌ Why other options are less suitable:
A. Batch reactor:

Not continuous and less efficient for managing heat in auto-thermal processes.

B. CSTR:

Has uniform temperature, which can dilute thermal gradients and make auto-thermal operation harder.

C. Semi-batch reactor:

Offers some control, but is still less effective for continuous auto-thermal operations.

✅ Final Answer: D. Plug-flow reactor






You said:
The most suitable reactor for carrying out an auto-thermal reaction is a

A. Batch reactor

B. CSTR

C. Semi-batch reactor

D. Plug-flow reactor


ChatGPT said:
The correct answer is:

D. Plug-flow reactor

✅ Explanation:
An auto-thermal reaction is one that sustains its own temperature due to the exothermic nature of the reaction — meaning external heating is minimal or not needed once the reaction starts.

To carry out such reactions efficiently, the reactor must:

Utilize the heat generated by the reaction.

Manage temperature rise along the reaction path.

Avoid thermal runaway while still benefiting from self-heating.

🔹 Why Plug Flow Reactor (PFR) is ideal:
Temperature gradient along the reactor length: Reactants heat up gradually as the exothermic reaction proceeds.

Efficient heat utilization: The heat released early in the reactor helps maintain temperature downstream.

Controlled conditions: Easier to design heat-exchange zones or insulation based on known progression of the reaction.

Suitable for high-temperature, exothermic gas-phase reactions such as:

Ammonia synthesis

Partial oxidation of hydrocarbons

Combustion reactions

❌ Other Options:
A. Batch reactor:

Poor heat transfer over time; not continuous; hard to maintain steady auto-thermal operation.

B. CSTR (Continuous Stirred Tank Reactor):

Uniform conditions; heat generated is immediately dispersed, making it hard to sustain an auto-thermal profile.

C. Semi-batch reactor:

Better than batch in terms of control, but still less effective for continuous and self-sustaining thermal profiles.

✅ Final Answer: D. Plug-flow reactor

The correct answer is:
D. Plug-flow reactor

Explanation:
An auto-thermal reaction is a reaction that maintains its operating temperature without external heating or cooling by balancing the heat generated and consumed.

Why Plug-Flow Reactor (PFR) is most suitable:
Temperature gradient along the reactor length: In a PFR, heat generated by the reaction can be utilized efficiently along the flow path to maintain the temperature.

High conversion per unit volume: PFRs allow for better heat and mass transfer control in highly exothermic or endothermic reactions.

Better temperature control: Especially important for reactions that can be thermally unstable.

By contrast:

CSTR has uniform temperature but poor heat utilization.

Batch and semi-batch reactors are harder to control continuously for heat balance and are less efficient for large-scale, steady auto-thermal operations.

So, Plug-flow reactor is the most suitable for auto-thermal reactions.