Synthesis and Characterization of 12-Tungstosilicic Acid Anchored to MCM-41 as well as Its Use as Environmentally Benign Catalyst for Synthesis of Succinate and Malonate Diesters

Comparing Cs+ binding affinity of Keggin type polyoxometalate and sodium Tetrakis(4-florophenyl)borate in solution and from Cs-doped pure phase vermiculite

We assessed the aptitude of cesium (Cs⁺) binding by Keggin type polyoxometalates (POMs) and compared the results with the Cs⁺ binding by sodium tetrakis(4-fluorophenyl)-borate (Na-TFPB). In this work, we aimed to establish a system to treat radioactive Cs⁺ contaminated soil with POMs economically. We evaluated the effect of initial Cs⁺ concentration (0.1M) and precipitant (POMs and TFPB) concentrations (0.01M) on Cs⁺ precipitation. Our comparison of Cs⁺ precipitation by three different POMs and TFPB was obtained by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). We synthesized POMs molybdovanadophosphoric acid, H₅PMo₁₀V₂O₄₀ (MVPA), and silicotungstic acid, H₄SiW₁₂O₄₀ (STA), and used commercially available phosphotungstic acid, H₃PW₁₂O₄₀ (PTA), and TFPB. Cs-doped pure phase vermiculite was also used to demonstrate the extraction potential of Cs⁺ by TFPB, STA, and PTA. All the POMs and corresponding Cs-bound POMs were characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray powder diffraction (XRD). In this simulation study, we demonstrated that the Cs⁺ removal by POMs is much more effective than TFPB and could be a promising method for the treatment of radiocesium contaminated soil.

Microwave-assisted catalytic conversion of chitin to 5-hydroxymethylfurfural using polyoxometalate as catalyst

The key challenges for converting chitin to 5-hydroxymethylfurfural (5-HMF) include the low 5-HMF yield. Moreover, the disadvantages of traditional acid-base catalysts including complex post-treatment processes, the production of by-products, and severe equipment corrosion also largely limit the large-scale conversion of chitin to 5-HMF. In this view, herein we have demonstrated a microwave aided efficient and green conversion of chitin to 5-HMF while using polyoxometalate (POM) as a catalyst and DMSO/water as solvent. Chitin treated with H2SO4 followed by ball-milling (chitin-H2SO4-BM) was selected as the starting compound for the conversion process. Four different POMs including H3[PW12O40], H3[PMo12O40], H4[SiW12O40] and H4[SiMo12O40] were used as catalysts. Various reaction parameters including reaction temperature, amount of catalyst, mass ratios of water/DMSO and reaction time have been investigated to optimize the 5-HMF conversion. The H4[SiW12O40] catalyst exhibited the highest catalytic performance with 23.1% HMF yield at optimum operating conditions which is the highest among the literature for converting chitin to 5-HMF. Significantly, the disadvantages of the state of the art conversion routes described earlier can be overcome using POM-based catalysts, which makes the process more attractive to meet the ever-increasing energy demands, in addition to helping consume crustacean waste.

Microwave-Assisted Homogeneous Acid Catalysis and Chemoenzymatic Synthesis of Dialkyl Succinate in a Flow Reactor

Two new continuous flow systems for the production of dialkyl succinates were developed via the esterification of succinic acid, and via the trans-esterification of dimethyl succinate. The first microwave-assisted continuous esterification of succinic acid with H2SO4 as a chemical homogeneous catalyst was successfully achieved via a single pass (ca 320 s) at 65–115 °C using a MiniFlow 200ss Sairem Technology. The first continuous trans-esterification of dimethyl succinate with lipase Cal B as an enzymatic catalyst was developed using a Syrris Asia Technology, with an optimal reaction condition of 14 min at 40 °C. Dialkyl succinates were produced with the two technologies, but higher productivity was observed for the microwave-assisted continuous esterification using chemical catalysts. The continuous flow trans-esterification demonstrated a number of advantages, but it resulted in lower yield of the target esters.

Magnetic nanoparticles-supported tungstic acid (MNP-TA): an efficient magnetic recyclable catalyst for the one-pot synthesis of spirooxindoles in water

This paper reports the preparation, characterization and catalytic application of a novel, magnetically separable catalyst consisting of tungstic acid supported on silica coated magnetic nanoparticles.