Abstract
Pt/γ-Al2O3 catalysts coated on honeycomb-shaped stainless STS-444 steel substrates with a γ-Al2O3 intermediate layer were prepared using a conventional washcoating method. The intermediate layer was formed on the substrate surface through oxidation using pack cementation. The monolithic catalysts with the intermediate layer were fabricated for potential applications to pre-turbocharger catalysts, which suffer from severe conditions such as vibrations of the engine and high flow rates of exhaust gas. Adhesive strength tests and simultaneous oxidation reactions of CO and C3H6 were carried out for the Pt/γ-Al2O3 monolithic catalysts with and without the intermediate layer. The catalysts with an intermediate layer showed much stronger adhesion than the catalysts without an intermediate layer. Thus, the formation of a γ-Al2O3 intermediate layer by surface oxidation through pack cementation facilitated a significant enhancement of the catalyst adhesion strength without catalytic performance degradation.
Highlights
Hazardous gas pollutants, such as carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx), emitted from gasoline and diesel engines have caused severe environmental problems [1]
In the X-ray diffraction (XRD) pattern of Pt/γAl2O3, the Pt peak could not be confirmed because the Pt content was as low as 2 wt% in the mixture, and nano-sized Pt particles were well dispersed on γ-Al2O3 [19,20]
Monolithic Pt/γ-Al2O3 catalysts coated on honeycomb-shaped stainless STS-444 steel substrates with a γ-Al2O3 intermediate layer were successfully prepared for potential preturbocharger catalyst applications
Summary
Hazardous gas pollutants, such as carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx), emitted from gasoline and diesel engines have caused severe environmental problems [1]. The adhesive strength of the catalyst to the metallic substrates on PTC, might not be strong enough to be durable under very fast flow of the exhaust gas and vibration between engine and turbocharger, resulting in catalyst detachment problems. An intermediate layer with strong adhesion to both the metallic substrate and catalyst layer is adapted to reduce detachment of the catalyst on PTC. We developed Pt/γ-Al2O3 catalyst with the γ-Al2O3 intermediate layer with strong adhesion through the oxidation of Fe2Al5 on the STS-444 substrate. The adhesion strengths of Pt/γ-Al2O3 catalysts on the STS-444 substrate were compared with and without an intermediate layer. CO and C3H6 oxidation reaction tests were performed using Pt/γ-Al2O3 catalysts on STS-444 substrates before and after adhesion tests to evaluate their catalytic activities and the effects of the intermediate layer. The reactions were tested under very high gas hourly space velocity (GHSV) conditions mimicking the PTC circumstances
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