Michel Deeba

In situ high temperature FTIR studies of NOx reduction with propylene over Cu/ZSM-5 catalysts

High temperature in situ FTIR has been used to investigate the surface species present on Cu/ZSM-5 during the reduction of NOx with propylene in a lean environment. Parallels have been observed between adsorbed surface species and catalytic activity for this reaction. Species detected at low temperatures are not representative of those detected at high temperatures where the catalyst is active. An oxidized nitrogen-containing species has been observed at 2580 cm−1 on Cu during reaction conditions (400°C). In contrast, at low temperatures, where the catalyst is less active, coke and Cu+-CO predominated. The effects of Cu weight loading, C/NO ratio, reaction temperature, and catalyst deactivation by steaming have been investigated with IR.

Lean NOx reduction with hydrocarbons over Ga/S-ZrOx and S-GaZr/Zeolite catalysts

Abstract Ga/S-ZrO x and sulfated GaZr/Zeolite catalysts were found to be very effective for the reduction of NO x in a lean environment with hydrocarbons.Ga/S-ZrO x was much more active than S-ZrO x orGa/ZrO x as well as a wide variety of Ga supported amorphous super acids. Incorporating ZSM-5 into the catalyst formulation, i.e.S-GaZr/ZSM-5, increased NO x reduction activity particularly at low temperatures. The effects of zeolite support, sulfation, and mono vs. bimetallic supported samples were investigated. For ZSM-5, sulfation and the combination of Ga with Zr proved to be most active.Ga/S-ZrO x andS-GaZr/ZSM-5 were investigated with C 3 H 8 , C 3 H 6 , CH 4 , and CO as reductants and compared toCu/ZSM-5. UnlikeCu/ZSM-5 which was most active with C 3 H 6 , Ga/S-ZrO x andS-GaZr/ZSM-5 were more active with C 3 H 8 than with C 3 H 6 .S-GaZr/ZSM-5 was also active with CH 4 . All three catalysts were inactive with CO and did not catalyze the NO x decomposition reaction. BothGa/S-ZrO x andS-GaZr/ZSM-5 were more hydrothermally stable thanCu/ZSM-5. However, their activities decreased significantly with increasing space velocity or in the presence of water in the feed making them impractical catalysts for mobile or stationary sources.

Stabilization of platinum on silica promoted with lanthanum oxide and zirconium oxide

Abstract A broad range of ZrO 2 loadings on silica were found to be effective in stabilizing SiO 2 against sintering. The combination of La 2 O 3 and ZrO 2 on SiO 2 was most effective in stabilizing platinum against sintering in an oxidizing environment. This catalyst is a promising candidate for improved sulfuric acid catalyst since platinum and SiO 2 have both been stabilized.

Lean NOx: dual sites for NOx reduction on Pt/H-ZSM-5

Abstract Pt/H-ZSM-5 contains independent sites for the reduction of NO x , (1) acidic sites associated with H-ZSM-5 which selectively reduce NO x to N 2 via stored hydrocarbons at low temperatures and (2) conventional Pt sites which reduce NO x to N 2 and N 2 O at higher temperatures. Propylene is trapped on acid sites, undergoes polymerization but retains activity for NO x reduction provided both NO and O 2 are present. Neither O 2 or NO will individually react with the adsorbed polymer but together NO x reduction occurs readily supporting the mechanism of enhanced conversion of NO x via NO 2 . This phenomenon has also been demonstrated with diesel fuel as the added reductant. This understanding suggests a novel strategy for diesel engines in which fuel is pulsed into the exhaust at the conditions where the acidic sites are active (i.e. 185°C) giving enhanced NO x conversion. After aging in the automobile exhaust, deactivation by de-alumination of the acidic sites occurs with a loss of hydrocarbon trapping and low temperature NO x reduction. Thus, improved hydrothermally stable materials are still needed to satisfy the mobile source applications.

Amination of olefins by zeolites

Abstract Direct addition of ammonia to olefins is catalyzed by acidic zeolites such as H-offretite, H-clinoptilolite, H-Y, and rare earth-exchanged Y. Selectivity to the corresponding amines is high (at least 97%). Conversions are controlled by temperature-dependent equilibria between the starting materials and product amines. Olefin ami nation occurs via Markownikoff addition. Reaction is believed to involve a carbocationic intermediate which is formed by interaction of the olefin with a surface proton or ammonium ion. Catalyst activity is proportional to the total number of strongly acidic sites as measured by ammonia chemisorption. Highest activities are obtained with small to medium pore acidic zeolites, such as H-clinoptilolite, H-erionite, and H-offretite.

Design Criteria of Catalyst Substrates for NOx Adsorber Function

Against the background of the current discussions on the reduction in CO2 emissions, the development of lean-burn engines is acquiring increasing importance. In order to meet future emissions limits, new strategies are required, especially for NOx conversion. One technique developed in recent years for the conversion of NOx in lean exhaust gases is the NOx adsorber catalyst, which stores NOx in lean operating conditions and must periodically be regenerated with rich exhaust gas. In this paper, the influence of catalyst substrate design on NOx conversion is described. In addition NOx conversion measurements with NOx adsorbers of various cell densities, variable diameter/length ratios as well as smooth and structured channel walls are carried out.

Progress in the development of NOx adsorber catalysts for DI gasoline engines

In this article by Engelhard Technologies, recent progress in NOx trap emission control for lean-burn gasoline engines is described on the basis of defined performance criteria. The influence of different ageing conditions on the maximum temperature stability of NOx adsorbers is presented. The maximum temperature stability and the operating temperature range of current NOx adsorbers require the use of a close-coupled pre-catalyst. For series application, the maximum temperature load of the adsorbers must be limited in order to guarantee durability.

Entwicklungsfortschritte bei NOx-Adsorberkatalysatoren für DI-Ottomotoren

Entwicklungsfortschritte bei der Abgasnachbehandlung fur Ottomotoren im Magerbetrieb mittels NOx-Speicherkatalysatoren werden im vorliegenden Beitrag von Engelhard Technologies anhand von Beurteilungskriterien beschrieben. Hinsichtlich der maximalen Temperaturstabilitat wird der Einfluss unterschiedlicher Alterungen auf den NOx-Adsorber dargestellt. Die zur Zeit vorhandene Temperaturstabilitat und der Arbeitstemperaturbereich aktueller Adsorber bedingen den Einsatz eines krummernahen Vorkatalysators. Fur aktuelle Serienanwendungen ist die maximale Temperaturbelastung der Adsorber zu begrenzen, um die Dauerhaltbarkeit zu gewahrleisten.