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•H3-xSnx/2PMo12O40-catalyzed glycerol etherification was assessed (x = 0.0, 1.0, 2.0, 3.0).•Analyses of TG/DSC, EDS/MEV, BET, DRX characterized Sn(II) heteropoly salts.•NH3-TPD and ...adsorbed pyridine FT-IR showed bifunctional Sn3/2PMo12O40 catalyst.•Annual capacity of 30,000 ton3 with a return on investment (ROI) of 30.7%.
In this work, phosphomolybdic acid salts were synthesized exchanging their protons by the Sn(II) cations (i.e., H3-xSnx/2PMo12O40; x = 0.0, 1.0, 2.0, 3.0), and evaluated in the etherification reactions of glycerol with tert-butyl alcohol (TBA). The catalytic activity of the phosphomolybdate salts containing a variable load of Sn(II) ions was further compared to phosphotungstic and silicotungstic acid salts (i.e., H3-xSnx/2PW12O40; x = 0.0, 1.0, 2.0, 3.0 and H4-xSnx/2PW12O40; x = 0.0, 1.0, 2.0, 4.0, respectively). The integrity of the Keggin anion after the synthesis was confirmed by infrared spectroscopy analysis. Physical properties were determined through thermal analyses, powder X-Rays diffraction patterns, N2 adsorption-desorption isotherms, and scanning electron microscopy. The acidity properties were analyzed by adsorbed pyridine FT-IR spectroscopy, NH3-programmed-temperature desorption, and potentiometric titration. Among all the Sn(II) heteropoly salts tested, the Sn3PMo12O40 was the most active and selective catalyst toward glyceryl ethers. The highest activity of Sn3PMo12O40 was assigned to the greater Lewis acidity strength. Modeling, simulation, and economic analysis allowed to evaluate the viability of the process. An annual capacity of 30,000 metric tons was developed, and the process is feasible with a return on investment (ROI) of 30.7%.
In this work, efficient solid acid catalysts were obtained from the stoichiometric reactions of Keggin heteropolyacids with SnSO4 and evaluated in the etherification reactions of glycerol with ...tert-butyl alcohol (TBA). Among the salts synthesized, the Sn2SiW12O40 catalyst was the most active and selective toward glyceryl ethers. High yields of mono- and di-glyceryl tert-butyl ethers were achieved after 4 h of reaction at 393 K. The impacts of the main reaction parameters such as stoichiometry of the reactants, catalyst load, time, and reaction temperature were assessed. The efficiency of the Sn2SiW12O40 catalyst was also assessed in etherification reactions of ethylene glycol with TBA, and etherification reactions of glycerol with other alcohols (i.e., n- or sec-butyl alcohol, and n- or iso-propyl alcohol). A proposal that describes the reaction pathway including the catalyst participation was also described.
New bone cement type that combines Sr2 + /Mg2 + or Sr2 + /Zn2 + co-substituted nano-hydroxyapatite (n-HAs) with calcium phosphate dibasic and chitosan/gelatin polymers was developed to increase ...adhesion and cellular response. The cements were physicochemically described and tested in vitro using cell cultures. All cements exhibited quite hydrophilic and had high washout resistance. Cement releases Ca2 + , Mg2 + , Sr2 + , and Zn2 + in concentrations that are suitable for osteoblast proliferation and development. All of the cements stimulated cell proliferation in fibroblasts, endothelial cells, and osteoblasts, were non-cytotoxic, and produced apatite. Cements containing co-substituted n-HAs had excellent cytocompatibility, which improved osteoblast adhesion and cell proliferation. These cements had osteoinductive potential, stimulating extracellular matrix (ECM) mineralization and differentiation of MC3T3-E1 cells by increasing ALP and NO production. The ions Ca2 + , Mg2 + , Zn2 + , and Sr2 + appear to cooperate in promoting osteoblast function. The C3 cement (HA-SrMg5%), which was made up of n-HA co-substituted with 5 mol% Sr and 5 mol% Mg, showed exceptional osteoinductive capacity in terms of bone regeneration, indicating that this new bone cement could be a promising material for bone replacement.
Integrated bioprocess strategies may facilitate ethanol production from both C6 and C5 fractions of lignocellulosic feedstocks. We propose a new process concept, SSICF, where sugarcane bagasse is ...hydrolyzed simultaneously with xylose isomerization and the co-fermentation of C6 and C5 sugars. A commercial cocktail was supplemented with our multi-enzymatic system composed of three recombinant enzymes immobilized in Feroxyhyte magnetic nanoparticles: β-glucosidase, β-xylosidase and xylose isomerase. SSICF was performed using non-GMO Saccharomyces at pH 6.0 and 35 °C for 72 h in a synthetic medium containing cellobiose and xylose, and another medium containing pretreated sugarcane bagasse (PSB). The results of ethanol global yields in SSICF were 77.67% and 73.24% for the synthetic medium and PSB, respectively. In a nutshell, this is the first report of a successful proof-of-concept of SSICF with four rounds of enzyme recycling and a non-GMO yeast, an innovative process with high potential for industrial use.
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•A new process concept was proposed for an efficient ethanol production in biorefineries.•The supplementation of immobilized enzymes in the SSICF process was investigated.•Non-GMO Saccharomyces was employed for second-generation ethanol production from PSB in SSICF.•The multi-enzymatic system allowed the yeast to produce ethanol from both C5/C6 sugars.•Ethanol production was achieved in all SSICF cycles with enzyme recycling.
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•Active hematite/magnetite photocatalysts were prepared by a simple method.•Magnetite retards the fast electron/hole recombination in hematite.•Hematite/magnetite catalyst was ...efficient to degrade dyes in water under UV Light.•Direct electron transfer to the valence band in hematite oxidizes the dyes.•The dyes are oxidized by photogenerated OOH radicals on the hematite surface.
Hematite/magnetite photocatalysts were prepared by thermal treatment at 500 and 1000°C of a Fe-rich waste obtained from a niobium mining. Rietveld analysis of XRD data and 57Fe Mössbauer spectroscopy indicated that during the heat treatment magnetite is partially converted into hematite, which was the active photocatalytic phase in the samples. The remaining magnetite in the composites was useful to retard the fast electron-hole recombination in hematite. Zeta potential measurements revealed that the point of zero charge (pzc) of the iron oxides increased due to the thermal treatment, which favored the adsorption of negatively charged dye molecules. Diffuse reflectance measurements indicated that the band gap energies of iron oxides increased after the heat treatment due to a higher amount of hematite in those samples. Moreover, the valence band edges of hematite were more positive after the treatment of samples, which increased its dye photo-oxidation power. The photo-oxidation of neat methylene blue and Congo red in the presence of all samples was more efficient than that of neat methyl orange. On the other hand, it was verified from the competitive studies using the three dyes simultaneously that the photo-oxidation of methyl orange was favored, while the methylene blue and Congo red photo-oxidation decreased due to the methyl orange is replacing Congo red in the active photocatalytic sites of hematite. The proposed mechanism of dyes degradation was based on two main processes: (i) direct electron transfer from the dyes to the valence band of hematite, and (ii) dye oxidation by photogenerated OOH radicals on the hematite surface.
Capture of CO2 by vermiculite impregnated with CaO Simplício Pereira, Matheus Henrique; dos Santos, Cláudio Gouvêa; de Lima, Geraldo Magela ...
Carbon management,
01/2022, Volume:
13, Issue:
1
Journal Article
Peer reviewed
Open access
Vermiculite samples were impregnated with different amounts of calcium oxide by the conventional thermal heating technique and subject to CO
2
capture experiments in thermal analysis equipment. The ...amount of CO
2
captured by calcium oxide increased from 13 g of CO
2
per mol of CaO to 16.8 g of CO
2
per mol of CaO when the experiments were carried out with pure calcium oxide and vermiculite impregnated with CaO (1:1), respectively. Integral isoconversional methods of Kissinger-Akahira-Sunose (KAS) and Osawa-Flynn-Wall (OFW) were used for the kinetic study of the process and good correlation coefficients were achieved. The apparent activation energy values showed that for low conversions (α < 0.3) the controlling step of the process is a mixed step where the chemical reaction and the diffusion of the reagents into the vermiculite have rates of the same order of magnitude (20 kJ < E
a
< 40 kJ). For higher conversions values (α > 0.3) the apparent activation energy values suggest that the slow step is a chemical step (E
a
> 40 kJ).
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•Valorization of biomass derivative levulinic acid over Tin(II) phosphotungstate.•Effect of H+ exchange by Sn2+ cations on the pristine heteropolyacid was assessed.•The Sn1.5PW12O40 ...was a highly active and selective catalyst toward alkyl levulinates.•The catalyst was efficiently recycled up to 3 times without loss in the activity
In this paper, we describe a process to add value to the biomass derivatives (i.e., levulinic acid), converting it to bioadditives over solid Sn(II) exchanged Keggin heteropolyacid salts. These solid catalysts are an attractive alternative to the traditional soluble and corrosive Brønsted acid catalysts. Among Sn(II) heteropoly salts, the Sn1.5PW12O40 was the most active and selective catalyst, achieving high conversions (ca. 90 %) and selectivity (90–97 %) for alkyl esters and angelica lactone, the main reaction products. The impacts of the main reaction parameters (i.e., catalyst load, temperature, and the molar ratio of alcohol to acid) were investigated. The use of renewable raw material, and an efficient and recyclable catalyst are the main positive features of this process. The Sn1.5PW12O40 catalyst was easily recovered and reused without loss activity.
Capture of CO 2 by vermiculite impregnated with CaO Simplício Pereira, Matheus Henrique; dos Santos, Cláudio Gouvêa; de Lima, Geraldo Magela ...
Carbon management,
01/2022, Volume:
13, Issue:
1
Journal Article
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