Is there anyone who specializes in vanadium-tungsten-titanium catalysts who can help answer questions regarding the color of such catalysts after sintering? ? ?
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I have tried to create vanadium-tungsten-titanium catalysts on a ceramic substrate by immersing the ceramic substrate in a pre-prepared impregnation slurry, which mainly consists of ammonium metavanadate, ammonium metatungstate, titanium dioxide, and other substances. After the previous sintering at 450 degrees Celsius, the color was yellow or yellow-green. But why does it turn gray or earthy gray after firing? I know that different valence states of vanadium result in different colors – the divalent state gives a gray color while the trivalent state yields a black color. So why does the color of the sample change, even when the firing conditions and the formula remain unchanged? That is, does the catalytic denitration activity of divalent and trivalent vanadium have a significant impact?
What you need to know is the valence, the structure type, and what level the valence of the active center should be controlled at? Is selective adsorption occurring due to an excessive immersion time? Should one batch be immersed and then baked at a time?
I need the pentavalent version; the catalytic activity of pentavalent vanadium is presumably the best. The impregnation time isn’t long; it’s about ten to fifteen minutes. Once it’s impregnated, it’s ready to be burned. I’m wondering if the sintering atmosphere in the furnace has changed; however, the furnace isn’t damaged and the temperature is sufficient. Before, I could obtain vanadium in the +5 valence state even when working carelessly, but now no matter how I try to sinter it, I can’t get the characteristic color of vanadium in the +5 valence state.
Is the atmosphere during firing reducing?