Pluronic P-123 is one of the popular non ionic surfactants to synthesize ordered mesoporous catalysts like Ni on Al2O3, SBA-15 etc. The synthesis process is straightforward and simple. We've been doing it over 2.5 years. Recently we're facing a problem regarding P-123 calcination to remove it by burning.
It is leaving grey to black residue (carbonaceous material) after calcination. We never faced this. Our heating rates are also low, 1deg C/min. Temperature is between 500-650 deg C with 8-11 h soaking time. There's no change in the recipe. We tried muffle furnace with sample on combustion boats, tube furnace with flowing air and sample on combustion boats, fixed bed reactor where air flows down through the sample. The air flow rate is between 45-65 mL/min for 24 h (during ramping and soaking).
Before calcination the solvent etc is removed by 48h drying at 60C. The dried sample containing co-polymer and aluminum iso-propoxide and/or nickel precursor is calcined.
I'm not sure what is causing carbonization of P-123 in all of the above setups. Why the carbonaceous material doesn't burn.
I even tried re-calcination after crushing, they are still there practically untouched.
Is anyone facing this issue? Thanks for your time and help.
You need to do a chemical analysis of the old Pluronic and the problem. It is possible that the problem Pluronic contains remains of inorganic substances. Organic matter, as you know, completely burn.
You may perform thermogravimetric analysis (TGA) of P123 to determine the temperature required to remove the template and an inorganic content in P-123, if any.
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