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- Bifunctional intimacy and its interplay with metal-acid balance in shaped hydroisomerization catalystsPublication . Mendes, Pedro; Silva, João M; Ribeiro, M Filipa; Daudin, Antoine; Bouchy, ChristopheThe combined impact of platinum location and metal-acid balance on the catalytic performances of HUSY zeolite alumina-shaped bifunctional catalysts was evaluated inn-hexadecane hydroconversion reaction. For well-balanced catalysts, the deposition of Pt in the alumina resulted in lower isomerization selectivity as compared to when platinum was located in the zeolite. In the latter case, the maximal distance between Pt and acid sites was found to be in the nanometric scale (high intimacy) whereas in the former it was in the micrometric scale (low intimacy), particularly due to the presence of large clusters of HUSY zeolite. Nevertheless, whenever proper balance between functions was not ensured in high-intimacy catalysts, the low-intimacy and well-balanced catalysts were shown to perform better. The requirement for nanometric metal-acid sites intimacy must be hence combined with an adequate metal-acid balance to achieve optimal catalytic performance.
- Bridging the gap between academic and industrial hydrocracking: on catalyst and operating conditions' effectsPublication . Mendes, Pedro S. F.; Silva, João M; Ribeiro, M Filipa; Daudin, Antoine; Bouchy, ChristopheThis work aims at bridging the knowledge gap between the well-studied Pt/zeolite catalysts and the industrially-employed NiMoS/(Al2O3+ zeolite) ones. To do so, catalyst series based on HUSY zeolite were evaluated in the hydroconversion of n-hexadecane under similar operating conditions, but the industrially-relevant H2S and NH(3)contaminants were added when evaluating the latter. The intrinsic performance of Pt/HUSY and NiMoS/(Al2O3+ HUSY) catalysts was noticeably similar, when well-balanced, with the catalytic activity being however much lower in the latter (temperature gap of 125 K). Ammonia inhibition of more than 99% of the protonic sites was revealed to be the origin of such low activity. On the other hand, the metal-acid balance was only reached at sufficiently low reaction temperatures (ca.593 K),i.e.when the NH(3)inhibiting effect increased the metal to acid site ratio in NiMoS/(Al2O3+ HUSY) to values five orders of magnitude larger than those in the Pt/HUSY one. In addition to the understanding achieved on the role of metal-acid balance in industrial-like catalysts and its key controlling parameters, these findings also point to the need to develop better hydrogenating functions to improve the efficiency, and consequently the sustainability of liquid fuel production.
- 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.