Y/MCM-41 composites assembled from nanocrystals

•Y/MCM-41 composites were synthesized via self-assembly of nanocrystals.•The composites with different microstructure can be obtained.•The coordination structure and acidic property of the composites were investigated.•The composite with ordered core-shell structure possesses higher conversion of heavy oil.

Using commercial NaY zeolites as silica–alumina source, Y/MCM-41 composites were synthesized via self-assembly of nanocrystals. The formation of the composites is consistent with overgrowth of mesoporous MCM-41 on zeolite Y. The mesostructures with ordered core–shell and randomly orientated stacks can be shown when the NaY was treated with Na2SiO3 and NaOH solution, respectively. The hydrothermal stability of the sample with randomly orientated stacks is inferior to that of with core–shell structure. The composite with core–shell structure retains an ordered hexagonal structure upon hydrothermal treatment in pure steam environment as well as upon the replacement of Na+ by NH4+ ions in severe conditions. It has higher Si/Al ratio, more acid sites compared with the sample prepared in the presence of NaOH. The order of Al species in the composite prepared with Na2SiO3 solution is superior to that of in the composite obtained with NaOH solution. In addition, the fluid catalytic cracking (FCC) catalyst with Y/MCM-41 of core–shell structure exhibits the higher conversion of vacuum gas oil (VGO) and total liquid yield than catalysts with Y/MCM-41 with randomly orientated stacks and HY zeolite.

Graphical abstractUsing commercial NaY zeolites as silica–alumina source, Y/MCM-41 composites were synthesized via self-assembly of nanocrystals. The mesostructures with ordered core–shell and randomly orientated stacks can be shown when the NaY was treated with different alkaline solution.Figure optionsDownload full-size imageDownload as PowerPoint slide