Kinetic modeling of catalytic conversion of methylcyclohexane over USY zeolites: Adsorption and reaction phenomena

Abstract

Catalytic conversion of cycloparaffins is a complex process involving competing reaction steps. To understand this process, FCC experiments using methylcyclohexane (MCH) on USY zeolite catalysts were carried out in the mini-fluidized CREC riser simulator. Runs were developed under relevant FCC process conditions in terms of partial pressures of MCH, temperatures (450-550 C), contact times (3-7 s), catalyst-oil mass ratios (5), and using fluidized catalysts. MCH overall conversions ranged between 4 to 16 wt %, with slightly higher conversions obtained using the larger zeolite crystallites. Moreover, it was found that MCH undergoes ring opening, protolytic cracking, isomerization, hydrogen transfer and transalkylation. A heterogeneous kinetic model for MCH conversion including thermal effects, adsorption and intrinsic catalytic reaction phenomena was established. Adsorption and kinetic parameters were determined, including the heat of adsorption (À40 kJ/mol), as well as thermal and primary catalytic intrinsic activation energies, which were in the range of 43-69 kJ/mol, and 50-74 kJ/mol, respectively. V

Selectivity of the Formation of the Ring-Closed Products and Methylcyclohexenes in the Dehydrogenation of Methylcyclohexane to Toluene

“…At atmospheric pressure, as shown in Figure 3(a), the yield of RCPs first increases with the MCH conversion and then virtually leveled off with the horizontal. Similar behavior was observed by Al-Sabawi and de Lasa [10] for the combined p = 5 bar T w = 634. Figure 2 may be used to explain the phenomenon.…”

Correlating the Process Variables and Products Involved in the Fluid Catalytic Cracking of Waste Feeds

“…The FCC runs were carried out in a CREC (Chemical Reactor Engineering Centre) riser simulator, using reaction condition resembling those of industrial FCC units [49]: T, 500-530-560 °C; CO, 3-5-7 g g -1 ; t, 3-6-12 s. A detailed schematization of the reactor is described in a previous work [24]. Once the reaction time was completed, the products were withdrawn from the reactor by triggering a valve which connects the reactor with a vacuum chamber in order to avoid side reactions.…”

Kinetic Analysis of the Hydrocarbon Total Oxidation Using Individually Measured Adsorption Isotherms

“…Thus, the physical meaning of the adsorbed constants can be increased while the estimated 95 % confidence intervals of the kinetic parameters are decreasing. Corma et al [41] and Al-Sabawi et al [42] determined adsorption parameters and heat of adsorption of long chain hydrocarbons for zeolite-supported catalysts in the range from 400 to 500°C and 450 to 550°C, respectively. Based on the adsorption equilibrium different reactant concentration on the catalyst surface can occur [31].…”

“…For that reason, Denayer and Baron [40] investigated several chain lengths and branched paraffins, as possible reactants, for the adsorption behavior in a broad temperature range. Corma et al [41] and Al-Sabawi et al [42] determined adsorption parameters and heat of adsorption of long chain hydrocarbons for zeolite-supported catalysts in the range from 400 to 500°C and 450 to 550°C, respectively.…”

“…Additionally a catalyst species transformation based on the different temperatures can occur. Hence, the adsorption measurements cannot reflect the adsorption behavior at reaction conditions [42].…”