A pilot-plant unit, namely, Multicrackex, for the catalytic cracking of hydrocarbons with the riser and regenerator units under direct heat exchange conditions was developed in the course of the present study. A two-levels pseudofactorial experimental program was designed using the synthetic gas oil SF-135 (CANMET) and a commercial equilibrium catalyst (Akzo Octaboost). Using the experimental temperature profile inside the riser, the reaction rate constants and activation energies were evaluated for the four lump model. These parameters were precisely estimated (±7% average), and the adequacy of the model was tested by statistical analysis, showing model predictions inside the ±15−20% error range. The experimental results and model predictions indicate that endothermic effects of the cracking reactions and gas oil vaporization are neutralized by the heat transfer from the regenerator to the riser.

Catalysts, so-called FCCT (catalysts for fluid catalytic cracking (FCC) with "in situ metal traps"), were developed to achieve high dispersion of passivators. These FCCTs were extensively tested and demonstrated experimentally. The catalyst, steamed to achieve equilibrium conditions, was artificially impregnated with a tin compound (0-3750 ppm) and with nickel and vanadium naphthenates. Experimental runs were performed in a microcatalytic fixed bed reactor using different carrier gas flows (120-150 std mL/min) and different temperatures (510-550 °C). The unsteady state pulse technique, gas oil pulses reacting with FCC catalyst, was used to study the effects of metal traps in a FCC catalyst contaminated with 3000 ppm of Ni and 4500 ppm of V. The four-lump model featuring gas oil, gasoline, light gases, and coke was used to evaluate the kinetic constants. The equations developed for the four-lump model were also used to evaluate the adsorption constants for gas oil, gasoline, and light gases. These parameters are of special importance for the simulation of industrial scale FCC risers. Experimental results demonstrated that gas oil conversion recovered significantly with FCCTs. It was also proven that the effects of the addition of the in situ metal traps were beneficial on gasoline yield, gasoline selectivity, and research octane number. A major contribution of the in situ metal traps was an important reduction in coke yield. Consistent with this result a reduced catalyst deactivation was observed with FCCTs.

This study shows the ability of the riser simulator, a novel internal fluidized bed, to determine the heats of gas oil cracking. With this goal, a gas oil feedstock is cracked using both Octacat and GX-30 catalysts. The experimental conditions studied include a catalyst-to-oil ratio of 4.85, typical reaction times of 3, 5, and 7 s, and temperatures in the 500-550 °C range. The heats of cracking are calculated from stoichiometric considerations and following a methodology consistent with classical thermodynamics. Stoichiometric coefficients for the product spectrum are estimated from the GC-FID chromatogram of the cracked products. The significance of estimations of the heats of cracking is demonstrated, in the present study, using a model for the FCC plant. These calculations are based on overall enthalpy balances applicable to the riser cracker and to the catalyst regenerator.

The present study considers a "Multicrackex" unit constituted by a riser reactor with an upflow catalyst suspension exchanging heat with a surrounding fluidized-bed regenerator. A statisticalbased analysis is developed to establish a semiempirical correlation able to describe the heat transport phenomena between a bundle of riser reactor tubes and a fluidized-bed regenerator. The proposed correlation is tested and developed under reaction and realistic conditions for fluidized catalytic cracking (FCC) units, and this adds special value to the study developed. In this respect, the present study provides data that may be of particular interest for the design of novel FCC processes.