Recent advances in the field of selective epoxidation of vegetable oils and their derivatives: a review and perspective

Halloysite nanotubes (HNTs) are naturally occurring clay mineral with nanotubular structures and have found increasing potential applications in industrial fields. Here, after a brief introduction of the general structure, main properties and newly emerging applications of HNTs, particular attention is paid to HNT-derived applications in water treatment. We mainly review the recent progress in applications of HNT-derived nanocomposites in heavy metal ion, dye or organic pollutant removal from wastewater and HNT-containing membranes for water filtration. The HNT-derived composites exhibit superior properties for water treatment in various ways and are promising to be used in practical applications. Finally, we summarize the predominant mechanisms acting in the applications of water treatment and future prospects are discussed.

Recent advances in halloysite nanotube derived composites for water treatment

Halloysite nanotubes (HNTs), clay minerals belonging to the kaolin groups, are emerging nanomaterials which have attracted the attention of the scientific community due to their interesting features, such as low-cost, availability and biocompatibility. In addition, their large surface area and tubular structure have led to HNTs' application in different industrial purposes. This review reports a comprehensive overview of the historical background of HNT utilization in the last 20 years. In particular it will focus on the functionalization of the surfaces, both supramolecular and covalent, following applications in several fields, including biomedicine, environmental science and catalysis.

Past, Present and Future Perspectives on Halloysite Clay Minerals.

Functionalization of vegetable oils (VOs) including edible, non-edible, and waste cooking oil (WCOs) to epoxides (EVOs) is receiving great attention by many researchers from academia and industry because they are renewable, versatile, sustainable, non-toxic, and eco-friendly, and they can partially or totally replace harmful phthalate plasticizers. The epoxidation of VOs on an industrial scale has already been developed by the homogeneous catalytic system using peracids. Due to the drawbacks of this method, other systems including acidic ion exchange resins, polyoxometalates, and enzymes are becoming alternative catalysts for the epoxidation reaction. We have reviewed all these catalytic systems including their benefits and drawbacks, reaction mechanisms, intensification of each system in different ways as well as the physicochemical properties of VOs and EVOs and new findings in recent years. Finally, the current methods including titrimetric methods as well as ATR-FTIR and 1H NMR for determination of conversion, epoxidation, and selectivity of epoxidized vegetable oils (EVOs) are also briefly described.

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Catalytic developments in the epoxidation of vegetable oils and the analysis methods of epoxidized products

https://pubs.rsc.org/en/content/articlepdf/2019/gc/c8gc03857k

Highly efficient epoxidation of vegetable oils catalyzed by a manganese complex with hydrogen peroxide and acetic acid

Epoxidation of soybean oil catalyzed by peroxo phosphotungstic acid supported on modified halloysite nanotubes

To granulate halloysite nanotubes (HNTs) into large-size particles, interfacial polymerization and condensation polymerization were combined. The former was used to form surface layer of particles and the latter was used to improve particle strength. Polyethylenimine (PEI) and terephthaloyl chloride were chosen, respectively as hydrophilic monomer and hydrophobic monomer in interfacial polymerization. Condensation polymerization was carried out between PEI and glycerol polyglycidyl ether (GPE). The results show that HNTs particles have sphere shape and its diameters range from 1.7 to 2.5 mm and vary with preparation condition. SEM images show that particles have typical core–shell structure with dense surface layer and porous inner structure and single nanotube is completely encapsulated by polymer material. The characterization of BET shows that because of dense surface layer and encapsulation of nanotubes, the specific surface area of particles determined decreases dramatically.

Preparation and characterization of large-size halloysite nanotubes particles by a combined technique of interfacial polymerization and condensation polymerization

The invention belongs to the technical field of preparation of big-diameter granules, and particularly relates to a method for preparing big-diameter granules from micro and nano powder by means of interfacial polymerization. The method comprises the following steps of: dispersing the micro and nano powder into aqueous solution of polyamine to obtain solution A, preparing aqueous solution B of water-soluble epoxy compound or polyaldehyde, mixing the solution A and B, and adding the mixed solution into solution C drop by drop through a sieve plate with aperture of 0.01 to 12 millimeters to obtain the big-diameter granules, wherein the solution C is supersaturated organic solution of oil-soluble compound containing multiple acyl chloride or isocyanate functional groups, and the diameter of the granules is 0.1 to 10 millimeters. The method is wide in micro and nano powder application range; the prepared granules have wide diameter range, high real spherical degree, uniform diameter distribution, adjustable internal porosity and high mechanical strength (crushing strength, 150N); and the method is quick in granulation, requires simple equipment, and is particularly suitable for small-size operation.

Liwei Yan

Papers

Epoxidation of soybean oil catalyzed by peroxo phosphotungstic acid supported on modified halloysite nanotubes

Preparation and characterization of large-size halloysite nanotubes particles by a combined technique of interfacial polymerization and condensation polymerization

Method for preparing big-diameter granules from micro and nano powder by means of interfacial polymerization