Question

Which compound is formed on catalytic hydrogenation of carbon monoxide at high pressure and high temperature in presence of \(ZnO-Cr_2O_3\) catalyst? 
 

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Methanol is industrially prepared by catalytic hydrogenation of carbon monoxide: \[ CO+2H_2\rightarrow CH_3OH \] using \(ZnO-Cr_2O_3\) catalyst under high temperature and pressure.

Answer 1

The Correct Option is A

Step 1: Identify the reactant and conditions.
The starting material is carbon monoxide (CO). The reaction is a catalytic hydrogenation with hydrogen gas ($H_2$) at high pressure and high temperature, using ZnO-Cr$_2$O$_3$ as the catalyst.
Step 2: Recall the industrial synthesis of methanol.
This is the classic industrial process for methanol synthesis. The balanced equation is: \[ CO + 2H_2 \xrightarrow{ZnO\text{-}Cr_2O_3,\, \Delta,\, high\, P} CH_3OH \] One mole of CO reacts with two moles of $H_2$ to give one mole of methanol ($CH_3OH$).
Step 3: Understand the role of the catalyst.
ZnO-Cr$_2$O$_3$ (zinc oxide-chromium oxide) is the heterogeneous catalyst used in the industrial methanol synthesis. It operates at temperatures around 300-400$^\circ$C and pressures of 200-300 atm. The catalyst activates both CO and $H_2$ on its surface.
Step 4: Confirm methanol as the product.
In the reaction, two $H_2$ molecules add across the C=O bond of CO: one $H_2$ reduces C=O to C-OH and another $H_2$ adds a second hydrogen to carbon. This gives methanol $CH_3OH$, the simplest primary alcohol.
Step 5: Rule out other products.
Under these specific conditions (ZnO-Cr$_2$O$_3$ catalyst, CO + $H_2$), only methanol is produced. Higher alcohols or hydrocarbons would require different catalysts or conditions (e.g., Fischer-Tropsch synthesis gives hydrocarbons).
Step 6: Match with options and confirm.
Option 1 shows methanol ($CH_3OH$), which is the correct product. The answer is option 1.
\[ \boxed{CO + 2H_2 \xrightarrow{ZnO\text{-}Cr_2O_3} CH_3OH} \]