TEAOH‐Templated SAPO‐34 Zeolite with Different Crystallization Processes and Silicon Sources: Crystallization Mechanism and MTO Performance

Sapo-34 Obtained from Amazonian Flint Kaolin: Influence of Impurities of “Oxidized Fe/Ti” in Synthesis and Its Application in the Removal of Cationic Dye from Water

Non-processed kaolin (flint kaolin) from a mine located in the Capim area (Amazon region, northern Brazil), usually considered as waste, was selected as a source of silicon and aluminum in the synthesis of SAPO-34. This is a molecular sieve and cationic exchanger chosen for tests focusing on the removal of methylene blue in aqueous solutions, which is a cationic dye widely used by textile industries in Brazil. The results revealed that the SAPO-34 has been successfully synthesized with typical cubic morphology, good crystallinity (>90%), and thermal stability (~998 °C). Although the oxidized Fe/Ti impurities contained in the flint kaolin affect the degree of crystallinity of the zeolitic product, its adsorptive properties are not significantly affected, which demonstrates the excellent adsorption results (pH = 11; % removal > 90%). It proved to be an adsorbent with considerable adsorption capacity (9.83 mg·g−1). The pH test confirmed the acidic surface characteristics (pH solution 2–4; ↓ removal), and the kinetic model that best fitted the experimental data was pseudo-second-order, with R2 = 0.998 (kinetics controlled by chemisorption).

Exclusive SAPO-seeded synthesis of ZK-5 zeolite for selective synthesis of methylamines

ZK-5 zeolite with superior selectivity for monomethylamine (MMA) plus dimethylamine (DMA) is fast synthesized using the exclusive silicoaluminophosphate SAPO-34 seed and K+ and Na+ cations.

Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH₃-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites.

The synthesis of SAPO-34 zeolite for an improved MTO performance: tuning the particle size and an insight into the formation mechanism

Effect of gel systems, additives and crystallization conditions on the size of SAPO-34 and the MTO performance has been studied.