Adsorption and desorption kinetics of hydrocarbons in FCC catalysts studied using a tapered element oscillating microbalance (TEOM). Part 1: experimental measurements

Diffusion and adsorption selectivities of hydrocarbons over FCC catalysts

“…The resulting K i on the compound catalysts are similar to those from Lee et al [6] (not shown) and give additional confidence to the values determined.…”

“…However, if the results obtained in this work are compared against those extrapolated to 250 • C from Lee et al [6], who used a TEOM microbalance to adsorb hexane, toluene and octane at 100-200 • C on a commercial FCC catalyst, similarities and discrepancies can be observed. In effect, even considering that the commercial FCC catalysts can be indeed different, the q i,s are close and the ranking among the various hydrocarbons is the same.…”

“…Again the information about the adsorption of hydrocarbons on Y zeolite at moderate temperatures is limited, and a wide variation of K i values is observed in the literature. For example, for the case of hexane at 250 • C (extrapolated values, in mol (kg psi) −1 ) Denayer et al [13] reported 0.317 on Na-Y and 0.073 on Na-USY, and Lee et al [6] reported 0.065 on RE-USY, while our observation was 0.140 for this RE-Y. Although these catalysts are different, the wide range of constants does not allow to state conclusions.…”

“…Microbalances are commonly used to assess adsorption constants in non-reacting environments. For example, Zhu et al [4] worked with light alkanes over silicalite below 200 • C; Hershkowitz and Madiara [5] adsorbed decane over LaY zeolite below 300 • C; Lee et al [6] contacted various paraffinic and aromatic hydrocarbons with commercial FCC catalysts under non-reacting conditions. Differently, a kinetic approach was applied to the conversion of vacuum gas oil (VGO) in a pulsed fixed-bed reactor, assessing adsorption and kinetics parameters simultaneously [7].…”

“…The results can be expressed on the basis that the adsorption of hydrocarbons is performed only on the zeolite component, considering that adsorption in the matrix component of typical FCC catalysts is negligible in comparison to that in the zeolite [6]. The corresponding zeolite Henry's constants are included in Table 1.…”