Selective radical depolymerization of cellulose to glucose induced by high frequency ultrasound.

The depolymerization of cellulose to glucose is a challenging reaction and often constitutes a scientific obstacle in the synthesis of downstream bio-based products. Here, we show that cellulose can be selectively depolymerized to glucose by ultrasonic irradiation in water at a high frequency (525 kHz). The concept of this work is based on the generation of H˙ and ˙OH radicals, formed by homolytic dissociation of water inside the cavitation bubbles, which induce the cleavage of the glycosidic bonds. The transfer of radicals on the cellulose particle surfaces prevents the side degradation of released glucose into the bulk solution, allowing maintaining the selectivity to glucose close to 100%. This work is distinguished from previous technologies in that (i) no catalyst is needed, (ii) no external source of heating is required, and (iii) the complete depolymerization of cellulose is achieved in a selective fashion. The addition of specific radical scavengers coupled to different gaseous atmospheres and ˙OH radical dosimetry experiments suggested that H˙ radicals are more likely to be responsible for the depolymerisation of cellulose.

The effect of titanium dioxide synthesis technique and its photocatalytic degradation of organic dye pollutants.

Nanostructured mesoporous titanium dioxide (TiO2) particles with high specific surface area and average crystallite domain sizes within 2 nm and 30 nm have been prepared via the sol-gel and hydrothermal procedures. The characteristics of produced nanoparticles have been tested using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy as a function of temperature for their microstructural, porosity, morphological, structural and absorption properties. The as-synthesized TiO2 nanostructures were attempted as catalysts in Rhodamine B and Sudan III dyes' photocatalytic decomposition in a batch reactor with the assistance of Ultra Violet (UV) light. The results show that for catalysts calcined at 300 °C, ∼100 % decomposition of Sudan III dye was observed when Hydrothermal based catalyst was used whiles ∼94 % decomposition of Rhodamine B dye was observed using the sol-gel based catalysts. These synthesized TiO2 nanoparticles have promising potential applications in the light aided decomposition of a wide range of dye pollutants.

Catalyst-Free Synthesis of Alkylpolyglycosides Induced by High-Frequency Ultrasound.

The irradiation of concentrated feeds of carbohydrates in alcoholic solution by high-frequency ultrasound (550 kHz) induces the formation of alkylpolyglycosides (APGs). This work is distinct from previous reports in that it does not involve any (bio)catalyst or activating agent, it takes place at only 40 °C, thus avoiding degradation of carbohydrates, and it selectively yields APGs with a degree of polymerization in a window of 2-7, an important limitation of the popular Fischer glycosylation. This ultrasound-based technology proved successful with a range of different valuable carbohydrates and alkyl alcohols. The elucidation of the structure of all the produced glycosides strongly suggests that 1,6-anhydrosugars formed in situ are key intermediate species.

Determination of optimal conditions for electrodeposition of Tin(II) in the presence of Alizarin Red S.

A detailed physicochemical properties of aqueous solutions of alizarin red S - tin (II) chloride, has been thoroughly investigated by extensively exploring the effect of pH, concentration and temperature on the optimal conditions for the formation of tin (II)-alizarin red S (ARS-Sn II) complex. UV-Vis spectra, electrical conductivity and pH method were also used to characterize the final product. The stoichiometry of the reaction complex formation was determined via different referential methods. It was observed that, the reaction complex was formed when the concentrations were smaller than a certain limit (10-5 M). Adjusting the pH of the reaction (typically from 3.7 to 6.0) also resulted in the formation of the complex. The formed complex was highly stable in dark conditions (absence of sunlight) and at ambient temperature. Without the use of additives and by employing the investigated optimal conditions (i.e. pH: 5.0, i: 6 mA/cm2, t: 5 min, C: 0.1 M, d: 1.273 × 10-4 cm), electrodeposition of tin (II) was demonstrated to be successful.

One-pot transformation of cellobiose to formic acid and levulinic acid over ionic-liquid-based polyoxometalate hybrids.

Currently, levulinic acid (LA) and formic acid (FA) are considered as important carbohydrates for the production of value-added chemicals. Their direct production from biomass will open up a new opportunity for the transformation of biomass resource to valuable chemicals. In this study, one-pot transformation of cellobiose into LA and FA was demonstrated, using a series of multiple-functional ionic liquid-based polyoxometalate (IL-POM) hybrids as catalytic materials. These IL-POMs not only markedly promoted the production of valuable chemicals including LA, FA and monosaccharides with high selectivities, but also provided great convenience of the recovery and the reuse of the catalytic materials in an environmentally friendly manner. Cellobiose conversion of 100%, LA selectivity of 46.3%, and FA selectivity of 26.1% were obtained at 423 K and 3 MPa for 3 h in presence of oxygen. A detailed catalytic mechanism for the one-pot transformation of cellobiose was also presented.