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- Investigation of cooperative effects between Pt/zeolite hydroisomerization catalysts through kinetic simulationsPublication . Mendes, Pedro; Silva, João; Ribeiro, M Filipa; Daudin, Antoine; Bouchy, ChristopheA kinetic dual-function model was employed to simulate the performance of binary mixtures of Pt/zeolite catalysts (so-called hybrid catalysts) in the hydroconversion of n-paraffins. The catalytic activity and the maximal yield in feed isomers were simulated for mixtures of catalysts with distinct characteristics to investigate the conditions in which cooperative effects based on metal-acid balance may arise. Superior performances of the hybrids compared to both individual catalysts could be achieved in most of the simulated systems, particularly when mixing Pt-catalysts containing zeolites with dissimilar characteristics. A careful choice of the proportion and metal-acid balance of individual catalysts is, nevertheless, necessary. Moreover, the cooperation in the hybrid catalysts was rationalized based on the performance of the individual catalysts being mixed. The more alike the individual catalysts, to a certain extent, the broader the range of metal to acid sites ratio over which hybrids perform better than both individuals. On the other hand, the relative gain in performance arising from the cooperative effect would decrease. This study unveils hence the influence of each one of the preparation parameters of hybrid catalysts on its behaviour shedding light into the complexity of such catalytic systems.
- Elucidation of the zeolite role on the hydrogenating activity of Pt-catalystsPublication . Mendes, Pedro; Gregório, André F. C.; Daudin, Antoine; Bouchy, Christophe; Silva, João; Ribeiro, M FilipaToluene hydrogenation was studied over model catalysts with a fixed hydrogenating function (Pt/Al2O3) mechanically mixed with either HUSY or HBEA zeolites. Such mechanical mixtures showed improved platinum turnover frequencies compared to single Pt/Al2O3. Comparing to Pt-impregnated zeolite catalysts, the mechanical mixtures have lower activities per site showing that the contribution of acid sites decreases (and so the hydrogenating activity) with increased distance between Pt clusters and acid sites. Therefore, toluene hydrogenation can be used as a powerful tool to evaluate Pt-acid site intimacy in bifunctional catalysts.
- Quantification of the available acid sites in the hydrocracking of nitrogen-containing feedstocks over USY shaped NiMo-catalystsPublication . Mendes, Pedro; Silva, João; Ribeiro, M Filipa; Bouchy, Christophe; Daudin, AntoineThe inhibition of Brensted acid sites by nitrogen -containing molecules was quantified under industrially relevant hydrocracking conditions. This was achieved by testing bifunctional catalysts based on HUSY zeolite in cyclohexane hydroconversion. For ammonia partial pressures within 0.2-2.8 kPa, the percentage of inhibited Brensted sites was superior to 98% at 623 K. Significant reduction in the ammonia content caused rather moderate variations on the number of available sites. Conversely, a temperature raise from 600 to 640K triplicated the vacant Brensted sites due to the significant endothermicity of ammonia desorption. The inhibiting effect of ammonia can be therefore easily modulated by temperature. (C) 2018 The Korean Society of Industrial and Engineering Chemistry.