I am trying to prepare a Ni-based catalyst(Ni/Ce2O3) by co-precipitation method. I was wondering what is the best precipitation agent and PH.
Ammonium hydroxide (NH4OH) and Sodium hydroxide (NaOH) are the most commonly used precipitation agents. The precipitation is usually carried out between 9 and 11 and maintained by adding the chosen precipitation agent (e.g., ammonium hydroxide or sodium hydroxide) gradually and slowly to the metal ion solution while stirring to avoid rapid pH changes that can lead to the formation of large and poorly dispersed particles.
Zakarya Zebiri Hi Thank you so much. I used ammonium carbonate but I got a very amorphous structure!
One issue that I have is I'm not sure how much precipitation agent I have to add as well the the concentration!
Azita Etminan You don't mention the concentration of Ni you require in the final material but the usual route to produce catalysts of this nature with Ni in the 1 - 5 wt% typically is by impregnation of the base material (e.g. Ni/SiO2, Ni/CaCO3 etc) and then subsequent reduction. Simple precipitation of Ni salts with base produces Ni(OH)2 which will calcine to NiO and not Ni.
The preferred route would need a knowledge of the pore volume of the base (do you really mean Ce2O3 and not CeO2?). This knowledge can be obtained by simple titration of a known amount of the dry material or via porosimetry. A solution of the appropriate Ni precursor (nitrate would always be preferred over chloride) would be used to just saturate the pores and produce an x wt% Ni in the final powder. Reduction would then take place (in the dry with H2; in the wet my preferred reductant would be 5 or 10% hydrazine hydrate as the only products are water and N2). This would then produce Ni in the required concentration on the substrate. A further drying process would be needed for wet reduction. I'd avoid borohydride reduction as this always leaves intractable B in the matrix.
Also see the phase diagram of Ce and its oxides (attached from: Article Spectrophotometric Determination of the Oxygen to Metal Rati...
BTW, it's pH and not PH...
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