A Kinetic Study ofn-Heptane Catalytic Cracking over a Commercial Y-Type Zeolite under Supercritical and Subcritical Conditions

Novel Process Options for Application of Zeolites in Supercritical Fluids and Ionic Liquids

“…Wang and Li [40] found that coking in the disproportionation of toluene could be avoided for a macroporous c-Al 2 O 3 catalyst if supercritical conditions were used, whereas this was not possible for the microporous zeolite H-ZSM-5. During the acid-catalyzed cracking of n-heptane, Süer et al [41] and Dardas et al [42] observed a denser phase within the pores of zeolite Y than in its immediate surroundings, which was in accordance with the results of adsorption mentioned in section 2.3. The authors concluded that only coking within the zeolite pores can be reduced by using supercritical conditions, while this is not possible for coke laydown on the outer crystal surface of the zeolites.…”

In‐situ CIR‐FTIR study of the diffusion of supercritical hydrocarbons in zeolite L

“…In most of the cracking reactions that were performed in the supercritical regime, we have consistently shown signifi-cant increases in catalytic activities and paraffin-to-olefin ratios at supercritical conditions relative to subcritical conditions (Suer et al, 1996a, b;Dardas et al, 1996b). Therefore, our objective here was to understand the adsorption and diffusion characteristics of paraffins and especially olefins (i.e., route to coke formation) under subcritical and supercritical conditions.…”

“…In view of the very limited data on intracrystalline diffusion coefficients of hydrocarbons at supercritical conditions inside porous catalysts, the objective of this study was to understand the effects of supercritical media on the transport behavior of hydrocarbons within porous catalysts by using a dynamic infrared technique (CIR-FTIR), which was developed earlier in our laboratories for the in-sifu analysis of homogeneous catalytic reactions (Moser et al, 1985;Moser, 1992), as well as monitoring the progress (i.e., active site concentrations) of hydrocarbon conversion processes (i.e., catalytic cracking) at high temperatures and pressures . Using this technique, detailed mechanisms of hydrocarbon catalytic cracking and catalyst stabilization toward rapid deactivation under supercritical fluid conditions were elucidated for the first time (Suer et al, 1996a, b;Dardas et al, 1996b).…”

Heterogeneous Catalysis in Supercritical Media, Part 3: Other Media

“…While cracking n-heptane, a far higher catalyst activity was measured in the supercritical range [24][25][26]. Other examples of reactions with a reactant also being the supercritical solvent are the disproportionation of toluene to benzene and the three xylenes [27], oxidation of isobutane to tert-butanol with air [28,29], and the Brönsted acid-catalyzed dehydrogenation of supercritical tert-butanol in a microreactor [30].…”