The time-on-stream stability of some selected bifunctional nanoporous-based catalysts in n-heptane hydroisomerisation

In this work, some com. nanoporous-based catalysts, such as USY, beta and mordenite zeolites loaded with Platinum metal acting as bifunctional catalysts, were used for hydroisomerisation expts. in a fixed-bed reactor at the atm. pressure and at feed space time 5.12 h-1 to hydroisomerise n-heptane over a temp. range of 210-270 °C. The study aimed to evaluate the changes with time-onstream in the catalytic activity, product selectivity and manner of deactivation of metal-loaded zeolite catalysts, at const. contact time of 5.13 h-1 and a hydrogen-to-n-heptane molar ratio fixed at 9. Various anal. techniques were used to characterize fresh and aged catalysts. Results show that pore architecture is the most important factor affecting coke formation and deactivation in zeolite catalysts, and those catalysts with three-dimensional pore structures lacking cavities or cages were best able to resist deactivation. In addn., it was found that those catalysts with high Si/Al ratios and those which had been acid-leached or steamed showed better activity, higher selectivity towards isomeric products and better time stability. Moreover, the balance between the no. of metal sites and the no. of acid sites played an important role in detg. the activity, selectivity and stability of the bifunctional catalysts. [on SciFinder(R)]