Abstract: The mesoporous molecular sieves RS-MCM-41 and RSA-MCM-41 were synthesized using rice straw (RS) or rice straw ash (RSA) as silica source. The differences between these two catalysts and SDS-MCM-41 catalyst synthesized from sodium silicate (SDS) were compared. The acidity of RSA-Al40/MCM-41 and RSA-Al10/MCM-41 were promoted by grafting Al with 40 and 10 of Si/Al mole ratio. After that, they were used as solid acid catalyst for synthesis of geranyl propionate (GP). The structures of the synthesized molecular sieves were characterized by XRD, FT-IR, NH₃-TPD, and N₂ adsorption-desorption. The structure of RS-MCM-41, RSA-MCM-41 and SDS-MCM-41 are shown in similar hexagonal mesoporous structure, good long-range order and crystallinity. However, all the catalysts showed low catalytic activities in synthesis of GP. Aluminum can be introduced into the framework of molecular sieves by grafting method as aluminum oxygen tetrahedron. After grafting, aluminium has negative influence on the crystallization of mesoporous molecular sieves, but it has positive influence on the amount of Brnsted acid sites on MCM-41 surface. The more of aluminium grafted, the stronger catalytic activity of molecular sieves is. The conversion of 54.47% and selectivity of 74.82% in synthesis of GP can be achieved with RSA-Al10/MCM-441 catalyst.

Key words: rice straw, rice straw ash, mesoporous molecular sieves, geranyl propionate