Automotive emission control (two-bed catalyst): A typical two-compartment catalytic converter in automobile exhaust uses noble metals to accomplish which set of conversions in the respective beds?

Introduction / Context:
Automobiles employ catalytic converters to meet emission standards. Modern three-way catalysts integrate oxidation and reduction functions, often arranged in zones or beds to optimize chemistry under varying exhaust conditions.

Given Data / Assumptions:

• Exhaust contains CO, unburnt hydrocarbons (HC), and NOx.
• Catalysts include platinum/palladium (oxidation) and rhodium (reduction), with platinum sometimes present across functions.
• Stoichiometry is near-stoichiometric with oxygen sensors managing air-fuel ratio.

Concept / Approach:
In a dual-bed arrangement, the first bed often promotes NOx reduction to N2 (small NH3 slip may occur under rich conditions). The second bed, supplied with oxygen, oxidizes CO to CO2 and HC to CO2 and H2O. This sequencing minimizes mutual inhibition and manages oxygen availability.

Step-by-Step Solution:
First bed (reduction): NOx + CO/H2/HC → N2 + CO2 + H2O (trace NH3 in rich spikes).Second bed (oxidation): CO + 1/2 O2 → CO2; HC + O2 → CO2 + H2O.All three statements align with this operation → choose “All (a), (b) and (c)”.

Verification / Alternative check:
OBD-equipped vehicles monitor catalyst efficiency via upstream/downstream oxygen sensors; conversion maps confirm reduction first, oxidation second in classic designs.

Why Other Options Are Wrong:
Any subset omits a key function of the two-bed system.

Common Pitfalls:
Assuming a single universal order; some designs integrate washcoats, but the functional trio (NOx reduction, CO oxidation, HC oxidation) remains essential.

Final Answer:
All (a), (b) and (c)