Ternary catalyst for automobile tail gas treatment

Abstract

The invention relates to a ternary catalyst for automobile tail gas treatment. The ternary catalyst comprises a honeycomb substrate, and is characterized in that a lower Pd coating is adhered to the honeycomb substrate, a middle Pd coating is adhered to the lower Pd coating, and an upper Rh coating is adhered to the middle Pd coating; the lower Pd coating comprises a Pd-loaded cerium-zirconium solid solution and La2O3-doped aluminum oxide (La2O3-Al2O3); the middle Pd coating comprises Pd-loaded La2O3-Al2O3 and a bonding agent; the upper Rh coating comprises an Rh-loaded cerium-zirconium solid solution and La2O3-Al2O3. Since the middle Pd coating contains no CeO2 ingredient, and Pd is loaded on La2O3-Al2O3, so that the catalytic capability of the ternary catalyst is improved, and the oxygen storage capability of the ternary catalyst is improved; compared with a traditional Pd / Rh dual-coating ternary catalyst, the ternary catalyst provided by the invention has relatively high hydrocarbon compound, carbonic oxide and oxynitride treatment capacity, and especially has relatively high oxynitride conversion capacity.

Description

technical field [0001] The invention relates to a three-way catalyst used for the treatment of automobile tail gas, and belongs to the technical field of automobile tail gas purification. Background technique [0002] The main pollutants of automobile exhaust are carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). The catalyst installed in the exhaust system can oxidize carbon monoxide and hydrocarbons into carbon dioxide (CO 2 ), water (H 2 O), and at the same time reduce nitrogen oxides to nitrogen (N 2 ), to achieve the purification of exhaust gas, this kind of catalyst is usually called three-way catalyst. The three-way catalyst consists of two parts: a honeycomb ceramic or metal support, and a catalyst coating attached to the support. Catalyst coatings usually consist of oxide materials with large specific surface area (such as alumina), oxygen storage materials, and noble metal active components (usually Pt (platinum), Pd (palladium) dispersed on the ...

AI Technical Summary

Problems solved by technology

However, under high temperature and oxygen-enriched conditions, the Rh in the upper coating tends to migrate to the lower coating and interact with Pd, which reduces the activity of the catalyst.

In addition, the loading of Rh on the oxygen storage material can greatly improve the oxygen storage capacity, but the oxygen storage and release function of the oxygen storage material makes the loaded Rh more likely to be in an oxidized state, and the oxidized Rh catalyzes the reduction of nitrogen oxides. Very low activity, even in transient conditions where the engine exhaust changes from lean to rich