The Influence of preparation method on the behavior of NOx Storage and Reduction Catalysts

HIDAYAT, Arif, Ir. Suryo Purwono, MA.Sc.,Ph.D

2006 | Tesis | S2 Teknik Kimia

Lean burn engines operate with oxygen excess, which results in lower emissions of both carbon monoxide and unburned hydrocarbons. However, the conventional three-way catalyst (TWC) is unable to reduce the NOx efficiently. The NOx storage technology is a potential method to reduce nitrogen oxides in lean exhaust. In this method the NOx is stored in the catalyst during a lean period (oxygen excess). To regenerate the catalyst, fuel rich exhausts are used for a short period of time where the NOx is released and reduced. The aim of this study is to investigate the influence of the preparation method on the behavior of NOx storage and reduction catalysts. The storage and reduction have been investigated by means of transient flow reactor experiments for three different catalysts: Pt/BaO/Al2O3, Ba/Pt/Al2O3 and Pt/ Al2O3. Two types of Al2O3 slurries are used in this study, one with a coarse alumina powder and one which is finely grained. The experiments were performed in a plug flow reactor consisting mainly of a horizontal quartz tube equipped with a heating coil, a gas mixer, devices for outlet gas analysis, temperature controller to monitor the gas phase temperature and computers to monitor and display the signals. The gases which are analyzed were NO, NO2, NH3, and N2O. The catalysts were tested at different temperature (200, 300 and 400oC). The total flow of gases in this experiment was 3500 mL/minute. The Pt/Ba/Al2O3, Ba/Pt/Al2O3 and Pt/Al2O3 catalysts with finely grained alumina powder store more NOx than the Pt/Ba/Al2O3, Ba/Pt/Al2O3 and Pt/Al2O3 catalysts with a coarse alumina powder. At 200oC, the Pt/Ba/Al2O3 catalyst with fine γ-Al2O3 slurry (CAT 14) has the best storage capacity compared the other catalysts. However, the Ba/Pt/Al2O3 catalyst with fine γ-Al2O3 slurry (CAT 19) stores a large amount of NOx at 300 and 400oC. It can be observed the Pt/Ba/Al2O3 and Ba/Pt/Al2O3 catalyst show different characteristics. At 200 and 300oC, the Pt/Ba/Al2O3 catalyst shows the best NOx storage capacity compare to Ba/Pt/Al2O3 catalyst. On the other hand, at 400oC the Ba/Pt/Al2O3 catalyst stores more NOx compare to the Pt/Ba/Al2O3 catalyst. Based on the statistical analytic by the student t test, it can be observed that the kinetic model of NOx oxidation on all of the catalysts can be described on the Eley-Rideal (E-R) mechanism and the Langmuir- Hinshelwood (L-H) mechanism.

Kata Kunci : Reduksi Katalis,Oksidasi NOx, NOx Storage, Reduction catalyst, lean burn, NO oxidation, NOx storage