Methodology and Modeling For Correlating Structure and Performance of Vacuum Gas Oil Hydrocracking Catalysts in a Batch Reactor
Résumé
A new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil, 370°C+ using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional mesoporous catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400°C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (2D-GC) respectively to obtain quantitative distributions of linear and branched paraffins, olefins, naphthenes and aromatics. The details of the products distribution provided by the chromatography were analyzed using model kinetic mechanisms of bifunctional catalysis. It has been established that the ratio of the molybdenum to zeolite in the bifunctional catalyst affects its activity and selectivity. The increase of the molybdenum to zeolite ratio provided an improvement of selectivity to middle distillate (150-370°C) and an increase of the total conversion of 370°C+ per gram of zeolite.