Investigation On Better Catalyst Preparation Via Cold Plasma Treatment

Plasma is the forth state of matter. It has been extensively applied in materialfabrication and modification, ozone synthesis, waste treatment, displayer and manyothers. Plasma green chemistry and chemical processing recently attract a greatattention worldwide. Catalyst preparation using various plasmas is one of the hottopics with it. The objectives of this work are to measure gas temperature of glow dischargeplasma for catalyst treatment; to prepare, using cold plasma treatment, the bettercatalysts for methane aromatization and for NO reduction by methane. The gas temperature measurement was conducted using an IR camera. Themeasurement demonstrates that, during glow discharge treatment of catalyst particlesor powder, the gas temperature remains below 50 °C. This confirms that the thermaleffect can be ignored during the glow discharge plasma treatment of catalyst. The catalyst for methane aromatization was prepared only using the glow dischargeplasma treatment, without further calcination thermally, in order to get as much aspossible the amount of Br?ndsted acid sites of the catalyst. The experimentalinvestigation confirms that the Fe-Mo/HZSM-5 catalyst prepared this way exhibits abetter low-temperature activity and an improved selectivity of aromatics. For example,at 673 K, the plasma treated catalyst shows a methane conversion of 8.43% with aselectivity of aromatics of 70.29%, while the methane conversion is only 3.85% overthe conventional prepared catalyst with a 29.71% of selectivity of aromatics. Inaddition, the plasma treatment reduces the amount of coke significantly. This meansthe cold plasma treatment induces an enhanced anti-carbon deposit performance. During our investigations of the mechanism of better catalyst preparation usingcold plasma treatment, we observed a novel self-assembled "corona zeolite" crystal,formed during calcination, under the flowing methane, of cold plasma treated zeolitecatalyst. There is no observed difference in phase structure and composition betweencorona and conventional zeolites. However, the reactivity towards methanearomatization is very different for the two catalysts based upon these two kinds ofzeolites. A novel catalyst preparation for NO reduction by CH4 has also been conductedusing the developed glow discharge plasma treatment following by calcinationsthermally. Such plasma prepared Pt/NaZSM-5 catalyst exhibits a highly dispersion ofmetal active species. A remarkable improvement in the activity and stability,compared to the catalysts prepared conventionally, has been achieved. Especially, anexcellent low temperature activity over the plasma treated Pt/NaZSM-5 catalyst hasbeen obtained. For example, the conventional 0.1wt%Pt/NaZSM-5 catalyst shows noactivity at temperatures below 673 K, while at 673 K, the NO conversion to nitrogenreaches 88.5% over the plasma treated 0.1wt%Pt /NaZSM-5 catalyst. The initiatedtemperature for the plasma treated 0.1wt%Pt/NaZSM-5 catalyst can be as low as 548K.