In this work, the catalytic activities of several single metallic oxides were studied for the treatment of propylene, a component in motorcycles’ exhaust gases, under oxygen deficient conditions. Amongst them, CeO2 is one of the materials that exhibit the highest activity for the oxidation of C3H6. Therefore, several mixtures of CeO2 with other oxides (SnO2, ZrO2, Co3O4) were tested to investigate the changes in catalytic activity (both propylene conversion and CO2 selectivity). Ce0.9Zr0.1O2, Ce0.8Zr0.2O2 solid solutions and the mixtures of CeO2 and Co3O4 was shown to exhibit the highest propylene conversion and CO2 selectivity. They also exhibited good activities when tested under oxygen sufficient and excess conditions and with the presence of co-existing gases (CO, H2O).
Different compositions of Co 3 O 4 catalysts on CeO 2 -ZrO 2 solid solution (Ce 0.9 Zr 0.1 O 2 and Ce 0.8 Zr 0.2 O 2 ) have been studied for the oxidation of propylene. The optional amount of Co 3 O 4 active phase on CeO 2 -ZrO 2 support of 30 wt% was found. The mixed Co 3 O 4 -CeO 2 -ZrO 2 with the same composition of the optimal supported ones showed approximately the same activity, which was not higher than the activity of the mixed Co 3 O 4 -CeO 2 catalyst. Catalytic activities of mixed Co 3 O 4 -CeO 2 with different loading contents supported on high surface area supports (Al 2 O 3 , SiO 2 ) were then measured. The optimal composition of active phase was still 30 wt% but the minimum temperature of the highest activity increased to above 300 ∘ C due to the inert nature influence of the support.
This paper compares different coating methods (in situ solid combustion, hybrid deposition, secondary growth on seed, suspension, double deposition of wet impregnation and suspension) to deposit Ce0.2Zr0.8O2 mixed oxides on cordierite substrates, for use as a three way catalyst. Among them, the double deposition was proven to be the most efficient one. The coated sample shows a BET (Brunauer–Emmett–Teller) surface area of 25 m2/g, combined with a dense and crack free surface. The catalyst with a layer of MnO2–NiO–Co3O4 mixed oxides on top of the Ce0.2Zr0.8O2/cordierite substrate prepared by this method exhibits good activity for the treatment of CO, NO and C3H6 in exhaust gases (CO conversion of 100% at 250 °C, C3H6 conversion of 100% at 400 °C and NO conversion of 40% at 400 °C).
Waste cutting fluids are considered as hazardous wastes because they contain numerous different components causing environmental problems. Normally, a flocculation method is applied to treat preliminarily. However, the output wastewater still needs treating further to meet the national standards of industrial wastewater before disposal. So, this research reports the secondary treatment stage of the waste cutting fluid collected from an industrial factory in Vietnam using zero valent iron (ZVI) catalyst. This catalyst was synthesized via a redox reaction between sodium borohydride (NaBH4) and ferric chloride (FeCl3). Key factors affecting the quality of the ZVI particles such as the concentration of the NaBH4 reductant, reaction temperature, and dropping rate were investigated systematically. At the optimum synthesis conditions, viz. the NaBH4 concentration of 0.2 M, reaction temperature of 25 oC and the dropping rate of 3 ml/min, the synthesized ZVI exhibited a narrow range of particle size distribution with a mean size of 3.9 μm, followed by a high surface area, and good catalytic activity. As a catalyst for secondary treatment of the waste cutting fluid, the synthesized ZVI demonstrated a moderate chemical oxygen demand (COD) removal performance of 49%, corresponding to COD reduction for from 4023 mg/l to about 2059 mg/l.
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