Selective Catalytic Oxidation over Ordered Nanoporous Metallo‐Aluminophosphates

Reaction Mechanisms of the Initial Oligomerization of Aluminophosphate

“…Microporous aluminophosphates (AlPO 4 - n ) are an important class of zeolitic materials, which were first reported by Wilson and co-workers in 1982. , Since then, more than 200 different structures, including one-dimensional, two-dimensional layered, and three-dimensional open-framework aluminophosphates, have been synthesized under hydro-, solvo-, and iono-thermal conditions. , These materials have potential applications in catalysis, chromatographic separations, and gas adsorption. For example, silicon-doped AlPO 4 -34 with chabazite topology (SAPO-34) is an important catalyst for the methanol-to-olefins process. − Thus, it is of practical importance to design and synthesize porous aluminophosphate frameworks with tailored architectures and properties, which requires a clear understanding of their formation and crystallization mechanisms.…”

Uniform Mesoporous Silicoaluminophosphate Derived by Vapor Phase Treatment: Its Catalytic and Kinetic Studies in Hydroisomerization of 1-Octene

“…Heterogeneous catalysis has advantages over homogeneous catalysis, since it can overcome the catalyst recyclability problem associated with the latter. In this regard, it is worth mentioning that aluminophosphate (AlPO) molecular sieves are structurally analogous to zeolites, have better framework flexibility with structural diversity, and are potential catalysts for isomerization, alkylation, and disproportionation reactions. − …”

“…An enormous number of aluminophosphate molecular sieve-based materials have been synthesized over the past few decades. − Uneven substitution of aluminum and phosphorus, by heteroatoms such as silicon and other transition metal ions, introduces extreme structural diversity in aluminophosphate materials . Substitution of silicon in the aluminophosphate framework (SAPO) produces materials with unique combinations of channel size and variable acidity. − SAPOs with mild acidity show enhanced selectivity and reduced deactivation rates in several organic transformations such as oligomerization of lighter olefins, dehydrocyclization, hydroisomerization, xylene isomerization, and the methanol-to-olefins process. − Compared to conventional microporous SAPOs, hierarchical mesoporous SAPOs and nano-sized SAPOs have advantages of shorter channels, higher surface area, and a larger number of exposed active sites that exhibit excellent catalytic activity and improve the resistance to coke deposition. − Although mesoporous silicoaluminophosphates and aluminosilicates are also promising catalysts, their structural instability limits their applications.…”

“…Several researchers have adopted various in situ and ex situ synthesis techniques to develop thermally and mechanically strong mesoporous materials. − Within the domain of aluminosilicate mesophase materials, surfactants employed in “bottom up” approaches were extensively explored to prepare meso/microcomposite materials by utilizing microporous molecular sieve seeds. , These amendments enhanced the thermal/mechanical stability and also provided excellent catalytic activity in several organic transformations such as esterification, cracking, acylation, and synthesis of α-tocopherol . These established landmarks in the field of aluminosilicate mesoporous materials motivated researchers to focus on the synthesis of framework materials similar to silicoaluminophosphate. − ,, Numerous methods like the liquid crystal templating (LCT) mechanism, cooperative self-assembly, , acid–base pair, sol–gel, and solvent-free synthetic routes have been used to synthesize mesoporous AlPO. Nevertheless, the lack of long-range order, owing to imperfect crystallization and poor condensation of inorganic moieties like Al, P, and Si around micelle aggregates of the surfactant makes the AlPO-based mesophase lamellar.…”

“…1−5 Uneven substitution of aluminum and phosphorus, by heteroatoms such as silicon and other transition metal ions, introduces extreme structural diversity in aluminophosphate materials. 5 Substitution of silicon in the aluminophosphate framework (SAPO) produces materials with unique combinations of channel size and variable acidity. 1−13 SAPOs with mild acidity show enhanced selectivity and reduced deactivation rates in several organic transformations such as oligomerization of lighter olefins, dehydrocyclization, hydroisomerization, xylene isomerization, and the methanol-to-olefins process.…”