MFI-type zeolites from natural materials: a comparative study of MFI-type zeolites generated from different diatomite species (part I)

Comparative Study between Direct and Pseudomorphic Transformation of Rice Husk Ash into MFI-Type Zeolite

“…In accordance with MFI-type zeolites obtained from other biomass materials, e.g., diatomite [ 15 ], all zeolite samples synthesized in this study exhibit type I isotherms with an additional uptake step for nitrogen in the p/p 0 region of 0–0.25. The isotherms show a horizontal plateau at p/p 0 between 0.25 and 1 as a further feature.…”

“…Figure 5 a–c show the nitrogen physisorption isotherms for initial RHA, MCM-41, and MFI-type zeolites samples after different hydrothermal treatment times. The industrial MFI-type reference zeolite (NH 4 -ZSM27) ( Figure 5 d) shows a nitrogen isotherm of type I [ 24 ], which is due to the sole presence of micropores [ 15 ].…”

“…The use of different pre-shaped biogenic silica species, such as diatomite or RHA, as an amorphous silica precursor for the preparation of various types of zeolites, such as ZSM-5 [ 15 , 16 , 17 ], NaA, and NaY [ 18 ] has already been reported. MFI-type zeolites exhibit a unique pore structure composed of intersecting straight and zig-zag channels of 0.5–0.6 nm width [ 19 ].…”

“…MFI-type zeolites exhibit a unique pore structure composed of intersecting straight and zig-zag channels of 0.5–0.6 nm width [ 19 ]. The hydrothermal transformation of RHA into ZSM-5 using TPABr [ 20 , 21 ] or TPAOH [ 15 , 17 , 22 ] as template in the presence of NaOH has also been reported. In these studies, RHA was first transformed into a sodium silicate solution, which was then used as the silica precursor for zeolite synthesis [ 17 ].…”

“…Other studies have investigated the influence of heterogeneous phases (impurities) in biogenic silica, i.e., diatomite [ 14 ] and RHA [ 22 ], on the synthesis of MFI-type zeolites. Recently, we reported the one-step transformation of diatomite into MFI-type zeolite with tetrapropylammonium hydroxide (TPAOH), which combines two functions (the dissolution and reorganization of silica) in one molecule [ 15 ]. In the present work, the partial and total transformation of amorphous RHA particles into zeolite was investigated.…”