Coal gasification chemistry: At higher gasification temperatures, which product distribution is favored in the equilibrium between CO2 and CO in the presence of steam and carbon?

Introduction / Context:
In coal gasification, reactions such as the Boudouard reaction (C + CO2 ⇌ 2 CO) and the water–gas reaction (C + H2O ⇌ CO + H2) govern the CO/CO2 balance. Temperature strongly shifts these equilibria. Understanding the temperature dependence helps control syngas composition for downstream uses (e.g., Fischer–Tropsch, power generation).

Given Data / Assumptions:

• Key equilibria: C + CO2 ⇌ 2 CO; C + H2O ⇌ CO + H2.
• Operating at elevated temperatures typical of entrained-flow or fixed-bed gasifiers.
• Equilibrium trends considered; real systems also involve kinetics and transport.

Concept / Approach:

The Boudouard reaction is endothermic in the forward direction (forming CO). According to Le Châtelier’s principle and equilibrium thermodynamics, raising temperature favors the endothermic direction, increasing CO at the expense of CO2. Similarly, the steam–carbon (water–gas) reaction is endothermic; higher temperature drives it forward to produce more CO and H2.

Step-by-Step Solution:

Verification / Alternative check:

Equilibrium constant K increases with T for endothermic reactions (d ln K / dT ∝ ΔH/R). Reported equilibrium charts show CO fractions rising with temperature, consistent with practice.

Why Other Options Are Wrong:

“High CO2” contradicts endothermic equilibria trends. “Neither affected” is false; temperature is a key lever. Selecting both “low CO2” and “high CO” correctly captures the shift.

Common Pitfalls:

Ignoring the effects of steam-to-carbon ratio and pressure; overlooking water–gas shift (CO + H2O ⇌ CO2 + H2) which can alter CO/CO2 downstream at lower temperatures with catalysts.

Final Answer:

Both (b) and (c)