Effect of Si-Doping on Thermal Stability and Diesel Oxidation Activity of Pt Supported Porous γ-Al2O3 Monolithic Catalyst

Abstract

A series of different contents of Si-stabilized aluminas with high thermal stability were synthesized by the coprecipitation method and were used as the support of Pt diesel oxidation catalysts. The physicochemical properties of SiO 2 -Al 2 O 3 (SA) and the catalytic performance of Pt/SiO 2 -Al 2 O 3 (Pt/SA) were characterized in detail by TG-DTA, XRD, infrared spectroscopy, N 2 adsorption, NMR, CO-TPD, and the catalytic activity evaluation of CO and C 3 H 6 oxidations as well as NO reduction in simulating diesel exhaust. The results indicate that the presence of Si can remarkably enhance the thermal stability and phase transition temperature of alumina. It was also found that the catalytic activity is virtually independent of surface area, and only appropriate amount of Si doping can improve the diesel oxidation activity, as compared to pure Pt/Al 2 O 3 under the same conditions as a result of the better dispersion of Pt on SA-W supports.

Ultrathin γ-Al2O3 nanofibers with large specific surface area and their enhanced thermal stability by Si-doping

“…First, NaAlO 2 solution (80 g L À1 , a k ¼ 1.42) was prepared by adding Al(OH) 3 into 300 mL NaOH solution (62 g L À1 ) at 100 C. And then, the resultant NaAlO 2 solution and Al 2 (SO 4 ) 3 solution (342 g L À1 ) were together dropped into distilled water at 60 C slowly under vigorous magnetic stirring. The white precipitation formed at the required pH value (6)(7)(8)(9)(10)(11) and aged for 2 h at 90 C under strong stirring. The solid product was collected by lter and washed by hot water (90 C) for several times, following dried at 110 C, which are marked as B-x (x ¼ the corresponding pH value).…”

“…[1][2][3][4][5][6][7] For some specific applications, such as catalytic conversion of automotive emission gas, 8 diesel catalytic oxidation, 9 catalytic decomposition of propellants for space propulsion, 10 the ability of γ-Al2O3 to maintain large specific surface area and abundant catalytically active surface sites at 1100~1200 °C or even higher temperature is of vital importance, which will allow for well-dispersion of active precious metal catalytic components and the enhanced catalytic activity. [1][2][3][4][5][6][7] For some specific applications, such as catalytic conversion of automotive emission gas, 8 diesel catalytic oxidation, 9 catalytic decomposition of propellants for space propulsion, 10 the ability of γ-Al2O3 to maintain large specific surface area and abundant catalytically active surface sites at 1100~1200 °C or even higher temperature is of vital importance, which will allow for well-dispersion of active precious metal catalytic components and the enhanced catalytic activity.…”

“…Gamma alumina (g-Al 2 O 3 ) and its related transition forms (such as d-Al 2 O 3 , q-Al 2 O 3 ), as a group of important industrial materials, are widely used in catalysis, adsorption and separation technology and automobile industries because of their desirable textural properties and surface acid-base properties. [1][2][3][4][5][6][7] For some specic applications, such as catalytic conversion of automotive emission gas, 8 diesel catalytic oxidation, 9 catalytic decomposition of propellants for space propulsion, 10 the ability of g-Al 2 O 3 to maintain large specic surface area and abundant catalytically active surface sites at 1100-1200 C or even higher temperature is of vital importance, which will allow for well-dispersion of active precious metal catalytic components and the enhanced catalytic activity. However, g-Al 2 O 3 is metastable phase and likely to sinter and convert irreversibly into the thermodynamically stable a-Al 2 O 3 via d-Al 2 O 3 and q-Al 2 O 3 intermediate phases at elevated temperature.…”

Facile synthesis of mesoporous Si-containing γ-Al2O3 nanofiber with enhanced thermal stability

“…However, γ-Al 2 O 3 can be sintered easily and can transform to thermodynamically stable Al 2 O 3 under high temperatures, resulting in the loss of surface area. In order to solve this problem, many additives, such as lanthanum nitrate [12,13] , cerium nitrate [14] , zirconium nitrate [14] , phosphoric acid [15] and tetraethyl orthosilicate(TEOS) [16] have been added to γ-Al 2 O 3 by conventional impregnation, precipitation or sol-gel method. The introduction of lanthanum can convert the pentacoordinated aluminum ions of γ-Al 2 O 3 into octahedral ones and improve the thermal stability of γ-Al 2 O 3 [17] .…”

Enhanced Sulfur Resistance of Pt-Pd/CeO₂-ZrO₂-Al₂O₃ Commercial Diesel Oxidation Catalyst by SiO₂ Surface Cladding

“…Although it was reported that ZrO2, TiO2, SiO2, and their mixed oxides show good sulfur tolerance, [21][22][23][24][25] few attempts have been done on improving sulfur resistibility of recent extensively used CeO2-ZrO2-Al2O3 based commercial DOCs. Due to the fact that SiO2 shows good sulfur tolerance and texture properties, the purpose of this work is to enhance the sulfur resistance of Pt-Pd/CeO2-ZrO2-Al2O3 commercial DOC using surface cladding of SiO2.…”