Question

An industrial method for the preparation of methanol is:
(A) by catalytic reduction of carbon monoxide
(B) by reacting methane with steam in the presence of a catalyst
(C) by reduction of $HCHO$ with $LiAl{{H}_{4}}$
(D) by reduction of $HCHO$ with aqueous $NaOH$

Answer 1

Hint: Think about what methanol is and which functional group is present in it. Take a look at the given option and think which process is the most feasible one which yields methanol in a good amount. Industrial or commercial methods are generally the ones which give good yields with limited resources and extreme conditions unless necessary so apply this context to each option and draw a conclusion.

Complete step by step solution:
-Methanol is an organic compound having the functional group alcohol (-OH). Its molecular formula is, $C{{H}_{3}}OH$.
-Methanol is a liquid compound at room temperature but it is volatile in nature. Its boiling point is $64.7{}^\circ C$.
-Commercially, methanol is prepared by catalytic reduction of carbon monoxide.
-In the process of synthesis of methanol, water gas is used. Water-gas is an equimolar mixture of carbon monoxide, CO and hydrogen, ${{H}_{2}}$.
-The reaction takes place in the presence of zinc oxide, ZnO and chromium oxide, $C{{r}_{2}}{{O}_{3}}$ as the catalyst and at 573K temperature.
-The reaction is represented as follows:
\[CO+{{H}_{2}}\xrightarrow{\text{ZnO-C}{{\text{r}}_{\text{2}}}{{\text{O}}_{\text{3}}},\,\,\text{573K}}C{{H}_{3}}-OH\]
-Water-gas is converted to methanol at high temperature due to the presence of a catalyst.
-Let’s see the other options.
-Methane in reaction with steam in the presence of a catalyst gives hydrogen gas, carbon dioxide and carbon monoxide. This is Haber's process for the synthesis of hydrogen.
-Reduction of formaldehyde in the presence of $LiAl{{H}_{4}}$ does yield methanol but this process is not used commercially because formaldehyde has strong tendency to get oxidized in the presence of oxygen in the air to form formic acid and products obtained will be a mixture of methanol and formic acid.
-Formaldehyde reacts with strong alkali to undergo Cannizzaro reaction to yield formic acid and methanol.
-Therefore, since the catalytic reduction of carbon monoxide yields only one product and it is economically efficient, this process is used in the commercial synthesis of methanol.

Therefore, the answer is option (A).

Note: Remember water gas is an equimolar mixture of carbon monoxide and hydrogen gas. Methanol is commercially synthesized by catalytic reduction of carbon monoxide. The catalyst used is zinc oxide and chromium oxide. This reaction is endothermic and is carried out at 573K temperature.