Recent Progress on Functionalized Nanoporous Heteropoly Acids: From Synthesis to Applications

Functionalized nanoporous heteropoly acids (HPAs) have garnered significant attention in recent years due to their enhanced surface area and porosity, as well as their potential for low-cost regeneration compared to bulk materials. This review aims to provide an overview of the recent advancements in the synthesis and applications of functionalized HPAs. We begin by introducing the fundamental properties of HPAs and their unique structure, followed by a comprehensive overview of the various approaches employed for the synthesis of functionalized HPAs, including salts, anchoring onto supports, and implementing mesoporous silica sieves. The potential applications of functionalized HPAs in various fields are also discussed, highlighting their boosted performance in a wide range of applications. Finally, we address the current challenges and present future prospects in the development of functionalized HPAs, particularly in the context of mesoporous HPAs. This review aims to provide a comprehensive summary of the recent progress in the field, highlighting the significant advancements made in the synthesis and applications of functionalized HPAs.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.

Ionic liquid immobilized on modified magnetic FSM-16: an efficient and magnetically recoverable nanocatalyst

In the present article, a nanocomposite was prepared by immobilizing ionic liquid on the magnetic mesoporous FSM-16 with a core-shell structure (Fe3O4@FSM-16-SO3/IL). Subsequently, the structural properties of the synthesized nanocatalyst were characterized and analyzed by various techniques such as XRD, FT-IR, TEM, FE-SEM, BET, VSM, TGA, and EDS. Fe3O4@FSM-16-SO3/IL was used as a recoverable and efficient nanocatalyst for the synthesis of polyhydroquinoline derivatives. The magnetic nanocatalyst showed remarkable stability and reusability and was reused six consecutive times without considerable loss of its activity.

Recent Advances in Imidazolium-Based Dicationic Ionic Liquids as Organocatalysts: A Mini-Review

Imidazolium-based dicationic ionic liquids (DILs) are gaining considerable space in the field of organocatalysis mainly due to the opportunities in offering new possible applicable structural variations. In addition to the well-known variables which made the ionic liquids (ILs) famous as the type of cation and anion used, the nature of the molecular spacer moiety turns out a further possibility to improve some physicochemical properties, for example, solubility, acidity, electrochemical behavior, and so on. For this reason, this class of ionic liquids has been considered as possible competitors to their corresponding monocationic salts in replacing common catalysts in organic synthesis, particularly in cases in which their bidentate nature could positively affect the catalytic activity. This mini-review is intended to highlight the progress carried out in the last six years in the field of organocatalysis, including DILs as such and as hybrids with polymers, nanomaterials, and composites.

Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40 supported on amine-functionalized MCM-41

Supported catalysts with Keggin type heteropoly acids (H5PMo10V2O40) loaded onto amine-functionalized MCM-41 for the catalytic hydroxylation of benzene to phenol with H2O2 were prepared by a wet impregnation method. The effects of the preparation conditions on the properties and activity of the supported catalysts were fully investigated. The results showed that the catalyst retained the mesoporous structure of MCM-41 and H5PMo10V2O40 was dispersed uniformly on the surface of the amine-functionalized MCM-41. Meanwhile, the reusability and catalytic performance of the catalyst were affected by two key factors, i.e., the interaction between the heteropoly acid and the surface of MCM-41, and the hydrophobicity of the catalyst since they decide the leaching of H5PMo10V2O40 and the adsorption of benzene. The catalyst with H5PMo10V2O40 loaded onto amine-functionalized MCM-41, which was prepared using ethanol as the solvent, exhibited the highest phenol yield (20.4%), a turnover frequency value of 20.3 h-1 and good reusability. We believe this work offers an effective and facile strategy for the preparation of a new catalyst for hydroxylation of benzene to phenol.

A study on biofuel produced by catalytic cracking of mustard and castor oil using porous Hβ and AlMCM-41 catalysts

Biofuel is the only novel solution to the increase in the greenhouse effect and bursting energy demand. The catalytic cracking of non-edible vegetable oils, namely castor and mustard was studied to yield gasoline range (C5-C9) hydrocarbons. Hβ (Microporous; pore size <2 nm) and AlMCM-41 (Mesoporous; pore size 2 nm-50 nm) materials with different Si/Al ratios were used as catalysts for cracking purposes. Characterization of these catalysts was done by X-ray diffraction, Surface area analyzer, nitrogen sorption studies, TPD and inductively coupled plasma techniques. Used mustard oil was cracked over AlMCM-41 catalysts in a fixed bed catalytic cracking unit at optimized reaction condition (400 °C, 4.6 h^-1) obtained over Hβ. The liquid and gaseous products were analyzed using gas chromatograph (Shimadzu GC-9A). Among the mesoporous catalysts AlMCM-41 (27) was able to convert 75% of mustard oil into 48% of bioliquid and 30.4% selectivity towards BG. Pongamia, neem, castor, fresh coconut and used coconut oil was also cracked using AlMCM-41 (27) catalyst. The major products of cracking reactions were Castor Bioliquid (CBL) comprising of bio gasoline (BG), bio kerosene (BK) and bio diesel (BD) with less yield of gaseous products. AlMCM-41 converted 98% of castor oil into 85% of CBL and it was tested with ASTM 6751 standard procedures for its calorific value, viscosity and flash point. The sulphur emission from CBL run engine reached lower index. The results exhibited the commercial utility of the CBL in the near future.