Multinuclear solid-state NMR characterization of fluid catalytic cracking catalysts containing AlPO4 as active matrix

Fluid catalytic cracking (FCC) is a remarkable and profitable conversion process in oil refineries as it turns heavy and low-priced feedstock into more valuable products, mainly gasoline and liquefied petroleum gas. The main FCC catalyst constituents are the Y zeolite in its ultra-stable form (USY), often exchanged with lanthanum (REUSY), and the matrix, typically composed of clay, alumina and silica. The development of new matrices can improve the hydrothermal stability of fluid catalytic cracking catalysts, provide better selectivity to cracking products and reduce coke yields. In this work, amorphous, mesoporous and stoichiometric aluminum phosphate (AlPO4) were investigated as active matrix to achieve these purposes.1
NMR experiments reveal the positive effect of AlPO4 synthesized at stoichiometric Al/P ratio at low pH, when mixed with REUSY, since framework dealumination is attenuated, according to 27Al and 29Si MAS. This effect is related to the migration of polyphosphate species to the zeolite in the calcined (fresh) composite, as evidenced by 1H and 31P MAS. The interaction between AlPO4 and Y zeolite improves zeolite stabilization under steaming, preserving more Brönsted acid sites. Mutually, it avoids AlPO4 crystallization, ensuring its catalytic properties for gasoil pre-cracking. Results suggest that FCC catalysts containing AlPO4 are potential alternative materials for increasing liquid yields and isoparaffins fractions. Besides, they can be attractive materials for reactions involving more easily crackable feedstock, such as renewable sources.1
[1] E.C. de Souza, M.M. Pereira, Y.L. Lam, E. Morgado Jr., L.S. Chinelatto Jr., Appl. Catal. A Gen. 619 (2021) 118156.