Effects of catalyst particle size on multiple steady states

Steady-state and dynamic hysteresis effects during lean co-oxidation of CO and C3H6 over Pt/Al2O3 monolithic catalyst

“…The oxidation of CO on Pt has been studied extensively [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The rate of Pt-catalyzed CO oxidation is known to be self-inhibiting due to the high affinity of CO to Pt.…”

“…Complicating this nonlinear kinetic behavior is the potential occurrence of steady state multiplicity and sustained oscillations, particularly for CO oxidation. Processes that cause steady state multiplicity are: (1) high adiabatic temperature rise due to heat generated from the exothermic reaction, a reaction rate that depends exponentially on temperature, and low effective heat Peclet number leading to thermal feedback, (2) non-monotonic (or negative order) kinetics leading to isothermal multiplicity through coupling between the kinetics and mass transfer, and (3) inherent kinetic nonlinearities [2][3][4][5][6][9][10][11][12][13]21]. It has been shown that negative-order reaction systems when coupled with transport resistances, can give rise to isothermal steady-state multiplicity.…”

“…Hegedus et al [4] have shown that the steady-state multiplicity observed in an isothermal, integral reactor can indeed be well interpreted by diffusion-reaction interactions, and that more than two stable steady states can be generated by appropriate manipulations of the time history of the operating conditions. Oh et al [11] studied experimentally the presence of multiple steady states during CO oxidation over Pt catalyst particles with various sizes. They showed that the width of the conversion-temperature hysteresis loop goes through a maximum with an increasing catalyst pellet size.…”

CO oxidation on Pt supported catalysts. Kinetics and multiple steady states

“…T catalysts has been extensively investigated in the last decade due to its importance in both applied and fundamental aspects of heterogeneous catalysts. One of the interesting features of this reaction is the steady-state multiplicity reported in a number of studies (Cutlip et al, 1976;Hawkins 1978;Oh et al 1979;Holliday 1981). This multiplicity may be generated by the interaction between negative-order kinetics and internal or external mass transfer resistances as pointed out by Wei and Becker ( 1975).…”

Hysteresis phenomena in co oxidation over platinum‐alumina catalyst

“…Hegedus et al (1977) found that by increasing the intrapellet diffusion resistances of the Pt/A120, catalyst by aging, the region of multiplicity was significantly broadened. Perhaps the most convincing demonstration of the transport hypothesis is the work of Oh et al (1979) who showed that hysteresis can be eliminated if the catalyst particle size is made very small. It is our thesis that the surface reaction-sorption interference explanation cannot be dismissed.…”