Background: commercial TWC catalysts system with PGM, Ce-Zr, Al2O3 etc
Target reaction HC-light off (HC means most likely C8 to C5)
The question is too general, more information is needed. At what residence time do you observe the conversion of AHC? Exactly which PGM do you use and what is the mass content of this PGM? What do you mean by "showed... oxidation" - non-zero or 100% conversion? Why do you think that the reaction rate is controlled by kinetics and not by diffusion limitations?
3%Pd/Ce-Zr, usually shows the toluene oxidation at around 300C. As per my understanding, Oxidation reaction are exothermic, so it must be kinetic control. At the temp below 300C, diffusion will not be issue (we did many experiments). Heat transfer from gas to solid play role. Higher temp then pore diffusion and bulk diffusion plays role. so my question how can we improve the activity as this situation??
Not enough information to understand the catalyst activity. What is the residence time or GHSV? What is toluene conversion at 300C?
In general - try Pt instead of Pd or try to optimize the Pd dispersion.
Note: It will help only if the reaction is under kinetic control, but for 3% Pd at 300C the kinetic control is rather doubtful.
PS: mass and heat transfer limitations does not depend at all upon the exothemic/endothermic character of the reaction.
Your correct Pt works better, it is quit expensive, I am looking to improve the Pd dispersion. My GHSV around 70,000h-1 and My catalysts aging temp 1100C/12h with Lean/Rich condition (Lean means air, rich means 95% N2, 5%H2/CO 1:3)....I am also working on support modification (SMSI) and Dopants. if you have any idea let me now any ideal dopants?
Well, ceria and zirconia seem to be good oxygen mobility promotors. You can also try other rare earth oxides - there's a lot of publications about it during last years.
What is the activity of ceria oxides ? What are their general behavior in heterogenous catalysis
Ceria in general is not too active in oxidation reactions, but it helps to increase the mobility of the lattice oxygen in the catalyst support thus improving the activity of the main active component (e.g. noble metal).
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