LABORATORY EVALUATION OF FCC CATALYSTS: ISOBUTANE YIELD

FRANCISCO PASSAMONTI; GABRIELA DE LA PUENTE; ULISES SEDRAN

Río de Janeiro, Brasil

Congreso; EMPROMER, 4th Mercosur Congress on Process Systems Engineering, 2nd Mercosur Congress on Chemical Engineering; 2005

Universidad Federal de Río de Janeiro

The process of catalytic cracking of hydrocarbons (FCC) plays a key role in the refineries, that is expanding in the near future as a consequence of two main factors: the increasing demand for petrochemical raw materials and the need to convert resid feedstocks. Isobutane is one of the main raw materials that is derived from FCC. It is known that hydrogen transfer reactions play an important role in the control of the relative amounts of product isobutane and olefins. Three equilibrium FCC catalysts of different types (conventional, octanes), with unit cell sizes of the zeolite components from 24.23 to 24.31 Å, were evaluated in the conversion of a vacuum gas oil commercial feedstock in a Riser Simulator laboratory reactor. Reaction temperatures were 500 and 550 ºC, catalyst to oil ratio was 6.1 and reaction times were from 3 to 15 s. Results allowed to observe the main characteristics of the catalysts in terms of various indexes, such as activity, gasoline yield, gasoline quality and delta coke. It was observed that the yield of isobutane, which is typically considered an index to show catalytic cracking activity, was the highest in the most active catalyst and the lowest in an octane catalyst. As expected, the higher the temperature, the less isobutane is formed at the same conversion, due to the lower incidence of hydrogen transfer reactions. In all the cases, isobutane is a primary product and the overall selectivity decreases with the reaction temperature. The proportion of isobutane among C4 paraffins is constant, while its relation with LPG products decreases with reaction temperature. The approach showed to be a proper tool to evaluate different properties in commercial FCC catalysts, in this case, in the search for the optimum isobutane yield.