Question

Convert Propyne to Propene.

Answer 1

While adding $H_2$ to alkyne, if the reduction is to be stopped at the alkene, the catalyst needs to be poisoned with $CaC{O}_3$/Quinoline.
${\mathrm{CH}}_{3}C\equiv {\mathrm{CH}}^{}+H_2\underset{\mathrm{Quinoline}}{\overset{\mathrm{Pd}/{\mathrm{CaCO}}_3}{\to }}{\mathrm{CH}}_3\mathrm{CH}={\mathrm{CH}}_2$