Catalytic conversion of microcrystalline cellulose to nanocellulose using iron oxide catalysts

265-270Catalytic conversion of microcrystalline cellulose (MCC) to nanocellulose involves a one-pot homogeneous reaction carried out by the cleavage of β-1,4-glycosidic bonds within the cellulose network. Through this work, the synergistic combination of ultrasonication and catalyst has been proved to be effective in the controlled depolymerisation process of cellulose. Iron oxide being a Lewis acid catalyst has been used to abstract the single electron from the electron-rich C-O bond in cellulose. The iron oxide, maghemite (γ-Fe2O3) shows the highest activity as determined by the increase of crystallinity index (CrI%) from 80.62% to 85.63%. The other phases of iron oxide also showed catalytic activity with hematite (Fe2O3) at 84.05% and magnetite (Fe3O4) at 83.39%. Morphology and particle size analysis clearly show that the nanocellulose have been obtained in the range 78 nm to 220 nm due to the structural dimension measurement of both thickness (diameter) & length. Spectroscopy analysis via Fourier transform infrared and Raman shows no changes to the functional group, hence the chemical composition and integrity of cellulose remains intact. Nanocellulose suspension obtained using maghemite exhibited the highest colloidal stability and surface tension making it more suitable for application

Influence of solution pH on the formation of iron oxide nanoparticles

Iron oxide phase orientation were highly influenced by solution pH, crystalline structure, purity, surface enrichment, particle size, and morphology. This paper investigates the influence of pHchanges by varying the precursor anions of chloride (FeCl2) and sulphate (FeSO4) on the formation of iron oxide nanoparticles using one step controlled precipitation technique. The obtained titration curve provided vital information on the reaction mechanism whereby different hydrolysis rate of precursor leads to different iron oxide phases. It was determined that at pH 4, goethite (α-FeOOH) was obtained. Continuous addition of hydroxyl ions (OH−) then forms iron hydroxides (Fe(OH)2) which will then subsequently react with the goethite precipitating magnetite (Fe3O4) nanoparticles (35–45 nm) atpH 10 with ferromagnetic behavior. By the use of Cl− anion, the slower hydrolysis process induced requires more hydroxyl ions to reach pHequilibrium leading to larger maghemite nanoparticles (50–60 nm). Spectroscopic analysis via Raman and FTIR analysis confirms the phases obtained. SEM andTEMimaging shows the correlation of structure orientation anisotropy which influenced the magnetic properties. Spherical magnetite nanoparticles strong dipolar interaction have higher coercivity (117G) and remanence (12 emu g−1) compared to the synthesised maghemite spinel needle-like structure nanoparticles. The understanding of the iron oxide structure directing effect by complex pH solution mechanism was essential for not only to prepare different forms of iron oxide and hydroxides but also controlled synthesis reproducibility

Catalytic conversion of microcrystalline cellulose to nanocellulose using iron oxide catalysts

265-270Catalytic conversion of microcrystalline cellulose (MCC) to nanocellulose involves a one-pot homogeneous reaction carried out by the cleavage of β-1,4-glycosidic bonds within the cellulose network. Through this work, the synergistic combination of ultrasonication and catalyst has been proved to be effective in the controlled depolymerisation process of cellulose. Iron oxide being a Lewis acid catalyst has been used to abstract the single electron from the electron-rich C-O bond in cellulose. The iron oxide, maghemite (γ-Fe2O3) shows the highest activity as determined by the increase of crystallinity index (CrI%) from 80.62% to 85.63%. The other phases of iron oxide also showed catalytic activity with hematite (Fe2O3) at 84.05% and magnetite (Fe3O4) at 83.39%. Morphology and particle size analysis clearly show that the nanocellulose have been obtained in the range 78 nm to 220 nm due to the structural dimension measurement of both thickness (diameter) & length. Spectroscopy analysis via Fourier transform infrared and Raman shows no changes to the functional group, hence the chemical composition and integrity of cellulose remains intact. Nanocellulose suspension obtained using maghemite exhibited the highest colloidal stability and surface tension making it more suitable for application

One step facile synthesis of ferromagnetic magnetite nanoparticles

The ferromagnetic properties of magnetite (Fe3O4) were influenced by the nanoparticle size, hence importance were given to the synthesis method. This paper clearly shows that magnetite nanoparticles were successfully synthesized by employing one step controlled precipitation method using a single salt (Iron(II) sulfate) iron precursor. The acquired titration curve from this method provides vital information on the possible reaction mechanism leading to the magnetite (Fe3O4) nanoparticles formation. Goethite (α-FeOOH) was obtained at pH 4, while the continuous addition of hydroxyl ions (OH−) forms iron hydroxides (Fe(OH)2). This subsequently reacts with the goethite, producing magnetite (Fe3O4) at pH 10. Spectroscopy studies validate the magnetite phase existence while structural and morphology analysis illustrates cubic shaped magnetite with an average size of 35 nm was obtained. The synthesized magnetite might be superparamagnetic though lower saturation magnetization (67.5 emu/g) measured at room temperature as compared to bulk magnetite. However the nanoparticles surface anisotropy leads to higher remanence (12 emu/g) and coercivity (117.7 G) making the synthesized magnetite an excellent candidate to be utilized in recording devices. The understanding of the magnetite synthesis mechanism can not only be used to achieve even smaller magnetite nanoparticles but also to prepare different types of iron oxides hydroxides using different iron precursor source

Catalytic dehydration of glycerol to acrolein over M2.5H0.5PW12O40 (M = Cs, Rb and K) phosphotungstic acids: Effect of substituted alkali metals

Catalytic conversion of glycerol into value-added chemicals, particularly acrolein via acid-catalyzed dehydration route has received much attention due to the potential uses of acrolein. This work reports the synthesis of various alkaline metal substituted phosphotungstic acid (H3PW12O40, HPW) catalysts, namely M2.5H0.5PW12O40 (M = Cs, Rb and K) using a controlled precipitation method. A systematic structural, morphology, and chemical characterization were conducted using various analytical techniques. XRD studies revealed that the incorporation of alkaline metals in H3PW12O40 leads to decreased crystallite size and enhanced lattice strain. N2 adsorption–desorption studies show that the specific surface area of H3PW12O40 is significantly improved from 5 to 82 (K2.5H0.5PW12O40), 103 (Rb2.5H0.5PW12O40), and 94 m2/g (Cs2.5H0.5PW12O40). XRD, Raman, and FT-IR studies confirm the Keggin structure of all the alkaline metal substituted HPW catalysts. The acidity strengths estimated by NH3-TPD analysis were obtained in the following order: H3PW (2654.91 μmole/g) > K2.5H0.5PW (1060.10 μmole/g) > Rb2.5H0.5PW (762.08 μmole/g) > Cs2.5H0.5.5PW (461.81 μmole/g). Although alkaline metal substituted H3PW12O40 catalysts exhibit higher specific surface area and smaller crystallite size compared to parent H3PW12O40 low glycerol conversions were found for substituted H3PW12O40 catalysts. As well, the parent H3PW12O40 catalyst shows an excellent acrolein selectivity (95%) which is much higher than that of Cs2.5H0.5.5PW (81.9%) and very close to the selectivities obtained over Rb2.5H0.5PW (95.1%) and K2.5H0.5.5PW (95.6%) catalysts. The catalytic performance of H3PW12O40 and M2.5H0.5PW12O40 materials is directly proportional to their acidic strengths, indicating that the catalyst acidity is a key factor for achieving better results in glycerol dehydration. Graphical Abstract Catalytic conversion of glycerol into value-added chemicals, particularly acrolein via acid-catalyzed dehydration route has received much attention due to the potential uses of acrolein. This work reports the synthesis of various alkaline metal substituted phosphotungstic acid (H3PW12O40, HPW) catalysts, namely M2.5H0.5PW12O40 (M = Cs, Rb and K) using a controlled precipitation method. A systematic structural, morphology, and chemical characterization were conducted using various analytical techniques. XRD studies revealed that the incorporation of alkaline metals in H3PW12O40 leads to decreased crystallite size and enhanced lattice strain. N2 adsorption–desorption studies show that the specific surface area of H3PW12O40 is significantly improved from 5 to 82 (K2.5H0.5PW12O40), 103 (Rb2.5H0.5PW12O40), and 94 m2/g (Cs2.5H0.5PW12O40). XRD, Raman, and FT-IR studies confirm the Keggin structure of all the alkaline metal substituted HPW catalysts. The acidity strengths estimated by NH3-TPD analysis were obtained in the following order: H3PW (2654.91 μmole/g) > K2.5H0.5PW (1060.10 μmole/g) > Rb2.5H0.5PW (762.08 μmole/g) > Cs2.5H0.5.5PW (461.81 μmole/g). Although alkaline metal substituted H3PW12O40 catalysts exhibit higher specific surface area and smaller crystallite size compared to parent H3PW12O40 low glycerol conversions were found for substituted H3PW12O40 catalysts. As well, the parent H3PW12O40 catalyst shows an excellent acrolein selectivity (95%) which is much higher than that of Cs2.5H0.5.5PW (81.9%) and very close to the selectivities obtained over Rb2.5H0.5PW (95.1%) and K2.5H0.5.5PW (95.6%) catalysts. The catalytic performance of H3PW12O40 and M2.5H0.5PW12O40 materials is directly proportional to their acidic strengths, indicating that the catalyst acidity is a key factor for achieving better results in glycerol dehydration

Facile synthesis of magnetite iron oxide nanoparticles via precipitation method at different reaction temperatures

The nano-scale magnetite iron oxide particles have been synthesised by a facile precipitation method. Magnetite iron oxide nanoparticles were synthesised in a bath with electrolytes composed of 0·10 M of iron (II) chloride with 0·45 M of sodium hydroxide at different reaction temperatures under oxidising environment. In the present study, the influence of reaction temperatures (30, 45 and 80°C) on the morphology, particle size and crystallinity of the iron oxide particles were investigated in detail. Based on the Malvern Zetasizer analysis, the iron oxide particles with variable size from ∼250 to ∼70 nm could be achieved when increasing the reaction temperature up to 80°C. The magnetite phase of iron oxide particles was determined by using X-ray diffraction analysis. In addition, field emission scanning electron microscopy micrographs were further affirmed that our synthesised iron oxide particles were in nano-scale with a spherical shape. It was found that the high reaction temperature is helpful in controlling the formation of uniform magnetite iron oxide nanoparticles