HZSM-5 nanocrystals grafted with different alkyl groups (ethyl, butyl, hexyl, dodecyl, and hexadecyl groups) were prepared to study their stable dispersion in the hydrocarbons as well as the quasi-homogeneous catalytic activities. The physical properties of the prepared zeolites were characterized by solid-state nuclear magnetic resonance, X-ray diffraction, N(2) adsorption-desorption, fourier transform infrared spectra of pyridine adsorbed, and dynamic light scattering. The results showed that the ZSM-5 crystal structure were kept without obvious change after grafting alkyl groups, but that their stable dispersions in the hydrocarbon significantly improved with increasing chain length of grafted alkyl groups by reducing aggregate size of HZSM-5 nanocrystals. Quasi-homogeneous catalytic cracking of n-dodecane at 427 degrees C showed that the cracking rates with hydrocarbon dispersible HZSM-5 nanocrystals improved by more than 2 times compared with thermal cracking, wherein the zeolites grafted hexyl group had the best catalytic activity in good agreement with its larger acid amount. 2011 Elsevier B.V. All rights reserved.