Gasoline and automobile catalysts 

Natural petroleum consists of organic sulfur compounds that must be eliminated before further processing, like they block active sites in a few catalysts and so act like poisons. While burnt they also provide the environmental pollutant SO₂.

 Hydrodesulfurization is the reaction where organic sulfur is converted to H₂S that is simply removed. Catalysts based on mixed Co-Mo sulfides are employed. Consequent processing of petroleum includes catalytic cracking and re-forming where long-chain hydrocarbons are reduced to shorter ones, along with isomerization processes providing a more desirable mixture of compounds. Bifunctional catalysts for these types of reactions consist of metals like Pt which are active for hydrogenation and zeolites like acid catalysts giving H⁺ to provide carbocations which are readily isomerize.

Catalysts for automobile exhaust systems are intended to eliminate environmental pollutants like unburned hydrocarbons, CO created from incomplete combustion and oxides of nitrogen. Three-way catalysts are derived from Pt and Rh jointly with several additives which together carry out a complex series of reactions, that are including removal of hydrocarbons through oxidation and steam reform, and

2CO + 2NO → 2CO₂ +N₂

Their operation relies on the nonexistence of poisons such like lead compounds, and on a fuel injection system that gives an approximately perfect stoichiometric ratio of fuel and oxygen to the engine: this is attained through a feedback system by using a sensor which observes the O₂ content of the exhaust gases, that are based on an electrochemical cell by using the ionic conductor ZrO₂ like a solid electrolyte.