Application scenario of VOC catalyst in automobile exhaust

The mechanism of action of VOC catalyst in automobile exhaust treatment mainly includes the following aspects:
Adsorption, including surface adsorption and selective adsorption.
Surface adsorption: The VOC catalyst has a large specific surface area and a special pore structure, and when the VOCs molecules in the tail gas contact the catalyst surface, they will be adsorbed to the active site of the catalyst. For example, organic pollutants such as benzene and toluene in automobile exhaust will be adsorbed to the surface of the catalyst, so that the reactants will be enriched on the surface of the catalyst, increasing the probability of collision between reactant molecules, and creating conditions for subsequent reactions.
Selective adsorption: Some VOC catalysts also have selective adsorption properties that preferentially adsorb specific types of VOCs molecules. For example, some zeolite-based catalysts have high adsorption selectivity for VOCs containing benzene rings, which can be preferentially adsorbed to the catalyst surface to improve the treatment efficiency of these pollutants.
Catalytic oxidation, including the reduction of reaction activation energy, reactive oxygen species participate in the reaction.
Reduction of reaction activation energy: The oxidation reaction of VOCs usually requires a high energy to occur, but under the action of VOC catalysts, the activation energy of the reaction will be significantly reduced. For example, precious metal catalysts (such as platinum, palladium, etc.) can interact with VOCs molecules to relax or break the chemical bonds of VOCs molecules, making it easier to react with oxygen and achieve oxidation at relatively low temperatures.
Reactive oxygen species participate in the reaction: In the catalytic oxidation process, the reactive oxygen species on the catalyst surface play a key role. The catalyst can activate oxygen in the air to produce oxygen atoms or oxygen ions with high reactivity. These reactive oxygen species react with VOCs molecules adsorbed on the surface of the catalyst, oxidizing VOCs into carbon dioxide and water. Taking ethanol as an example, under the action of reactive oxygen species on the catalyst surface, the carbon-hydrogen bonds and carbon-oxygen bonds in ethanol molecules break and combine with oxygen to form carbon dioxide and water.
Formation of intermediates: In the catalytic oxidation process, VOCs molecules are first oxidized into some intermediates, such as aldehydes, ketones, acids, etc., which are further oxidized, and finally carbon dioxide and water are generated. For example, in the treatment of propylene, propylene is first oxidized to acrolein, which is further oxidized to carbon dioxide and water.