| A flow-through ceramic monolithic oxidation catalyst, containingβzeolite, Cerium/Zirconium solid solution and precious metal Pt, was preliminarily developed for diesel exhaust purification. Theβzeolite was coated by in situ synthesis, while Cerium/Zirconium solid solution was deposited through in situ combustion synthesis. The adsorption properties and catalytic oxidation activity of the catalyst were tested by probe technique.Ce0.6Zr0.4O2 solid solutions were prepared by four methods including sol-gel, solution combustion, co-precipitation and surfactant-assisted approach, respectively. The physicochemical properties were characterized by XRD, BET, SEM and TEM technology. The XRD and TEM results showed that a Ce0.6Zr0.4O2 solid solution was formed for samples as-prepared and heat-treated at 900 oC for 2h. The BET surface area of co-precipitation derived Ce0.6Zr0.4O2 was as high as 153.71m2/g; however, it decayed greatly after a thermal treatment in air at 900oC for 2h. The same tendency was also observed for the samples prepared by sol-gel and surfactant-assisted approach. Notable is that the surface area for fresh Ce0.6Zr0.4O2 ignited at 350oC decreased little.The catalytic properties of Ce0.6Zr0.4O2 solid solutions and/orγ-Al2O3 for the combustion of soluble organic fractions (SOF) were studied by DTA/TG method. In this work, a commercial lube was substituted for SOF. It is found that lube evaporation and thermal decomposition (pyrolysis) were observed under nitrogen atmosphere, while under air atmosphere, namely, in the process of lube oxidation, lube evaporation, low temperature oxidation and high temperature oxidation were distinguished. The light-off temperatures and exothermal peak areas of all samples were calculated, the results shows that the all samples calcined at 900oC exhibited relative high catalytic oxidation properties. A computer program was developed by direct non-linear regression model for simulation of TGA curves to determine the thermal processes and kinetic parameters. The results show that there exists synergism between Ce0.6Zr0.4O2 andγ-Al2O3:γ-Al2O3 adsorbs lube retaining it within its pore structure, whereas, Ce0.6Zr0.4O2 solid solution initiates oxidation reactions when light-off temperatures reached. Moreover, the solution combustion derived Ce0.6Zr0.4O2 shows a higher catalytic property than other approaches.Theβzeolite was synthesized on cordierite honeycomb by in situ technology, and then Ce0.6Zr0.4O2 solid solution was coated using in situ solution combustion approach. The presence ofβzeolite and/or Ce0.6Zr0.4O2 solid solution on supports was confirmed by XRD,SEM,BET and pore distribution. SEM characterization clearly showed that zeolite grows both on the surface of the monolith channels and into the cordierite macroporous structure. The TPD spectra of toluene, which was used as probe molecule for unburned HC, showed that the in situβzeolite has higher adsorption amount, and can retard desorption of toluene to higher temperatures. The increase of adsorption amount is due to the more adsorptive surface area compared to bulkβzeolite. CO oxidation probe reactions were carried out on the catalysts supported with 1wt. % Pt. It is found that the catalyst has high oxidation activity.In summary, a diesel oxidation catalyst with high catalytic activity was developed. It can also effectively adsorb hydrocarbons and retain it's desorption to higher temperatures.
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