Understanding the Manufacture of Methyl Alcohol

The question asks about the catalyst used in the process of making methyl alcohol (methanol) from water gas. Water gas is a mixture of carbon monoxide ($\text{CO}$) and hydrogen gas ($\text{H}_2$). The synthesis of methyl alcohol from water gas is an important industrial process.

The Chemical Reaction for Methyl Alcohol Synthesis

The chemical reaction involved in the synthesis of methyl alcohol ($\text{CH}_3\text{OH}$) from water gas ($\text{CO} + \text{H}_2$) is:

\(\text{CO(g)} + \text{2H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)}\)

This reaction is reversible and exothermic. To shift the equilibrium towards the formation of methyl alcohol and achieve a good reaction rate, a catalyst is essential, along with specific temperature and pressure conditions.

Identifying the Catalyst for Methyl Alcohol Production

Different catalysts have been used historically for methyl alcohol synthesis. Early processes used catalysts containing zinc oxide ($\text{ZnO}$) and chromium(III) oxide ($\text{Cr}_2\text{O}_3$) at high temperatures and pressures.

Modern processes often use copper-based catalysts, but the question likely refers to a common high-pressure synthesis method where the zinc oxide and chromium(III) oxide combination is prominently used.

Let's look at the given options:

1. \(\text{ZnO} + \text{MnO}_2\)
2. \(\text{Cr}_2\text{O}_3 + \text{MgO}\)
3. \(\text{ZnO} + \text{Cr}_2\text{O}_3\)
4. \(\text{CaO} + \text{CrO}_3\)

Comparing these options with the commonly known catalysts for methyl alcohol synthesis from water gas, the combination of zinc oxide ($\text{ZnO}$) and chromium(III) oxide ($\text{Cr}_2\text{O}_3$) stands out as the correct catalyst system used in many industrial processes for producing methyl alcohol.

Role of Catalyst Components

In the \(\text{ZnO} + \text{Cr}_2\text{O}_3\) catalyst system for methyl alcohol synthesis:

• Zinc Oxide (\(\text{ZnO}\)): Zinc oxide acts as the primary catalytic component, facilitating the reaction between carbon monoxide and hydrogen to form methyl alcohol.
• Chromium(III) Oxide (\(\text{Cr}_2\text{O}_3\)): Chromium(III) oxide typically acts as a promoter or stabilizer. It helps in maintaining the surface area and activity of the zinc oxide catalyst over time and under the high-temperature, high-pressure conditions of the synthesis.

This combination of zinc oxide and chromium(III) oxide is effective for the high-pressure synthesis of methyl alcohol.

Therefore, the catalyst used in the manufacture of methyl alcohol from water gas among the given options is \(\text{ZnO} + \text{Cr}_2\text{O}_3\).