High resolution transmission electron microscopy and methane catalytic decomposition tests revealed that this encapsulating layer can also exert a significant role in the control of the size distribution (40–140 nm) and catalytic activity of the resultant CENiNPs. By heating non-isothermally different initial amounts of NiAc (100–400 mg) in an argon flow at 10 ☌/min from room temperature to 500 ☌, CENiNPs were readily obtained, in which a thin layer of carbon resulting from the breakdown of the anion protects their metallic core from spontaneous oxidation.
The reaction was conducted inside a thermogravimetric analyzer coupled to a quadrupole mass spectrometer for evolved gas analysis. 4H 2O (NiAc) was possible by varying systematically the initial amount of the precursor during its pyrolysis. In this study, size control of carbon-encapsulated nickel nanoparticles (CENiNPs) synthesized by direct thermal decomposition of Ni(CH 3COO) 2. If the heating rate is high (≥5☌ min −1) and the oxygen partial pressure is low (≤1%), the shape of TPO profiles for highly saturated hydrocarbon coke deposited on cracking catalyst are affected by changes in the rate-determining step with increasing temperature. Because of differences in assumed mechanisms and carbon substrates, calculated preexponential factors and activation energies can not be readily compared with literature values, although some comparisons are made. Evolution rates of CO during TPO are independent of the O 2partial pressure, whereas an order of 0.75 is indicated for CO 2formation. Rate coefficient parameters and O 2reaction orders were then optimized to simulate the TPO profiles recorded over a range of conditions: heating rates of 2, 5 and 10☌ and O 2partial pressures of 0.939, 1.11, and 5.0% in an atmosphere of N 2. Two pathways to CO and two to CO 2evolution, all involving either undissociated or dissociated surface oxide complexes, were assumed.
The reaction kinetics of evolved carbon monoxide and carbon dioxide during the temperature programmed oxidation (TPO) of an industrially spent fluid cracking catalyst have been investigated.
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