Isto Eilos

Kinetics of catalytic cracking with short contact times

Abstract A novel isothermal pulse reactor was used to study the kinetics of gas oil cracking on a FCC equilibrium catalyst with short contact times. The feed was a lighter gas oil than typically used in FCC-units. Experiments were carried out by varying the catalyst-to-oil ratio, volume of the oil pulse, temperature and residence time. After each hydrocarbon pulse the catalyst was regenerated by introducing several oxygen/nitrogen pulses through the catalyst bed. The amounts of carbon monoxide and carbon dioxide formed were measured and the amount of coke on the catalyst was calculated. The reproducibility of the experiments was excellent. A kinetic model that included five lumps, namely, gas oil, gasoline, liquefied petroleum gas (LPG), dry gas and coke with five cracking reactions was developed first and its kinetic parameters were determined from the experimental results. The data could be best described by the model wherein the rate of cracking of gas oil to gasoline and to LPG were both approximated as second order dependency and the rate of cracking of gas oil to dry gas and to coke as first order dependency on the gas oil concentration. The five-lump model was further enlarged by dividing the gasoline fraction into paraffins, olefins, naphthenes and aromatics resulting in an eight-lump model with eight reactions. In addition, changes in the activity of the catalyst during one experiment was accounted for by using two exponential activity functions, one for catalytic cracking reactions and the other for coke formation. The formation of dry gas was considered to be the product of a thermal reaction only. The kinetic parameters of the Arrhenius’ law and the deactivation parameters were estimated by a non-linear regression program. In the five-lump model 12 parameters and in the eight-lump model 18 parameters (rate coefficients, activation energies and deactivation parameters) were obtained. The kinetic parameters of the Arrhenius’ law were statistically significant in both models.

Kinetics of the regeneration of a cracking catalyst derived from TPO measurements

Abstract Regeneration kinetics of a cracking catalyst was studied by temperature programmed oxidation (TPO) in a microreactor system. The CO and CO2 responses were detected as a function of time while heating the sample at a constant rate. Different oxygen concentrations (0.5–2.0%) and heating rates (5 and 10 K / min ) were applied. Three kinetic models were tested and the parameters were estimated by non-linear regression. The models were capable of describing the experimental data adequately and the parameters were physically acceptable.

A CFB unit for skeletal isomerization of linear c4-c6 olefins on ferrierite catalysts

Abstract Isoolefins can be used for production of environmentally preferred gasoline components. It is possible to increase the available C 4 -C 6 isoolefins by skeletal isomerization of the corresponding linear olefins. High activities and selectivities to isoolefins can be obtained with zeolites. The drawback of the zeolite catalyst is the limited catalyst life due to coke formation. Continuous reaction and catalyst regeneration can be performed in a CFB (Circulating Fluidized Bed) unit. Experiments were made in a pilot unit at 300°C with refinery FCC light naptha feed. Continuous regeneration was made at 400–600°C both with nitrogen and air. Stable conversion of about 40 wt-% and selectivity of 90 wt-% could be maintained during the test. The selectivity was dependent of the carbon content on the catalyst and an optimum yield was reached with about 5-wt% carbon on the catalyst. The CFB unit data was compared to fixed bed unit data.