Nine gas-phase reactions that can be accomplished with an inexpensive, commercially-available glass-encased, heterogeneous palladium catalyst tube are described. The catalyzed reactions are suitable for demonstrating gas-phase reactions in the classroom or teaching laboratory. The reactions described include air or oxygen oxidations (CH4 + O2, CO + O2, NH3 + O2), hydrogenation of ethene, thermal decomposition of nitrous oxide, oxidations involving nitrogen dioxide (CH4 + NO2, CO + NO2), and two oxidation reactions involving nitrous oxide (N2O + NH3, N2O + CO). Several of the reactions demonstrate processes that take place in an automotive catalytic converter. In all cases, the products can be tested by simple chemical methods.
This article describes two organic reactions involving gas-phase heterogeneous catalysis suitable for use as an advanced undergraduate synthesis and spectroscopy laboratory experiment. In the first reaction, 2-propanol is converted to propene using heated alumina beads as the catalyst. The product gas is purified with a dry ice–propanol cold trap. In the second reaction, the propene is hydrogenated to propane using a palladium catalyst in nearly 100% yield. Both propene and propane are characterized by proton nuclear magnetic resonance spectroscopy and both give elegant spectra that are ideally suited for interpretation by undergraduate students. Students may use proton decoupling to assign the spectrum and COSY to confirm chemical shift assignments. This laboratory experiment is original in that gas-phase organic reactions are not usually experienced in chemistry laboratory programs. The experiment demonstrates continuous-flow, closed-system gas phase reactions of fundamental importance in chemical industry.
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