Development of a supported tri-metallic catalyst and evaluation of the catalytic activity in biomass steam gasification

A supported tri-metallic catalyst (nano-Ni–La–Fe/γ-Al₂O₃) was developed for tar reduction and enhanced hydrogen production in biomass steam gasification, with focuses on preventing coke deposition and sintering effects to lengthen the lifetime of developed catalysts. The catalyst was prepared by deposition–precipitation method and characterized by various analytical approaches. Following that, the activity of catalysts in biomass steam gasification was investigated in a bench-scale combined fixed bed reactor. With presence of the catalyst, the content of hydrogen in gas products was increased to over 10 vol.%, the tar removal efficiency reached 99% at 1073 K, and more importantly the coke deposition on the catalyst surfaces and sintering effects were avoided, leading to a long lifetime of catalysts.     

Synthesis of γ-cyclodextrin/chitosan composites for the efficient removal of Cd(II) from aqueous solution

The synthesis of chitosan-graft-γ-cyclodextrin (Ch-g-γ-CD) using persulfate/ascorbic acid redox system was done and characterized by FTIR, XRD, TGA and SEM/EDX. The optimum yield of the copolymer was obtained using 16 × 10⁻³ M γ-cyclodextrins (γ-CD), 2.8 × 10⁻² M ascorbic acid (AA), 1.8 × 10⁻² M K₂S₂O₈ and 0.1 g chitosan in 25 mL of 2% aqueous formic acid at 45 ± 0.2 °C. The highest percent grafting samples were evaluated for cadmium metal ion (Cd(II)) removal from the aqueous solutions where the sorption capacities were found proportional to the grafting extent. The sorption was pH and concentration dependent where, pH = 8.5 was found to be the optimum value. The adsorption data were modeled using Langmuir and Freundlich isotherms. The equilibrium data followed the Langmuir isotherm model with maximum sorption capacity of 833.33 mg/g. The influence of electrolytes, sodium chloride (NaCl) and sodium sulphate (Na₂SO₄) on Cd(II) uptake was also studied. Desorption of the cadmium loaded Ch-g-γ-CD was accomplished with 0.01 N H₂SO₄. The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 27% adsorption was feasible.     

Colorimetric estimation of human glucose level using γ-Fe2O3 nanoparticles: An easily recoverable effective mimic peroxidase

This article reports simple, green and efficient synthesis of γ-Fe₂O₃ nanoparticles (NPs) (maghemite) through single-source precursor approach for colorimetric estimation of human glucose level. The γ-Fe₂O₃ NPs, having cubic morphology with an average particle size of 30 nm, exhibited effective peroxidase-like activity through the catalytic oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂ producing a blue-colored solution. On the basis of this colored-reaction, we have developed a simple, cheap, highly sensitive and selective colorimetric method for estimation of glucose using γ-Fe₂O₃/TMB/glucose–glucose oxidase (GOx) system in the linear range from 1 to 80 μM with detection limit of 0.21 μM. The proposed glucose sensor displays faster response, good stability, reproducibility and anti-interference ability. Based on this simple reaction process, human blood and urine glucose level can be monitored conveniently.     

Preparation of solid acid catalyst from glucose-starch mixture for biodiesel production

The aim of this work is to study the catalyst prepared by glucose-starch mixture. Assessment experiments showed that solid acid behaved the highest esterification activity when glucose and corn powder were mixed at ratio of 1:1, carbonized at 400 °C for 75 min and sulfonated with concentrated H₂SO₄ (98%) at 150 °C for 5 h. The catalyst was characterized by acid activity measurement, XPS, TEM and FT-IR. The results indicated that solid acid composed of CS_0.073O_0.541 has both Lewis acid sites and Broˇnsted acid sites caused by SO₃H and COOH. The conversions of oleic acid esterification and triolein transesterification are 96% and 60%, respectively. Catalyst for biodiesel production from waste cottonseed oil containing high free fatty acid (FFA 55.2 wt.%) afforded the methyl ester yield of about 90% after 12 h. The catalyst deactivated gradually after recycles usage, but it could be regenerated by H₂SO₄ treatment.     

Recovery of activated carbon catalyst,calcium, nitrogen and phosphate from effluent following supercritical water gasification of poultry manure

A new method for suspending a fine, activated carbon catalyst in a biomass feedstock used for a supercritical water gasification (SCWG) continuous reactor is proposed. In a previous study, the organic matter in poultry manure was shown to be completely converted into gases such as H₂, CO₂ and CH₄ using SCWG. In practice, however, since the feedstock is not only composed of organic matter, but also contains inorganic material, water and catalyst, products such as gas, solid and liquid are produced during SCWG. The aim of this work was to investigate SCWG by-product utilization. This paper describes fundamental studies on the recovery of materials from SCWG products to develop a novel and simple recycling process that utilizes the by-products. A major portion of the activated carbon, monetite and ammonium sulfate can be isolated from the SCWG effluent.     

Anti-diabetic effects of sodium 4-amino-2,6-dipicolinatodioxovanadium(V) dihydrate in streptozotocin-induced diabetic rats

The evaluation of the anti-diabetic effects of an organic vanadium(V) complex in streptozotocin (STZ)-induced diabetic rats was investigated. The STZ-induced diabetic rats were orally administrated with sodium 4-amino-2,6-dipicolinatodioxovanadium(V) dihydrate (V5dipic-NH₂), a vanadium(V) coordination compound. The compound was administered through drinking water at a concentration of 0.1 mg/mL for 20 days, and then the concentration was increased to 0.3 mg/mL for the following 20 days. At the end of the experiment, V5dipic-NH₂ statistically significantly reduced the levels of blood glucose (P < 0.01), serum total cholesterol (P < 0.01), triglycerides (P < 0.01) and the activities of serum aspartate amino transferase (P < 0.05) and alkaline phosphatase (P < 0.01) compared to untreated diabetic animals. After treatment with 0.3 mg/mL V5dipic-NH₂, the oral glucose tolerance was improved in diabetic animals (P < 0.01). In addition, the daily intake of elemental vanadium was markedly decreased in V5dipic-NH₂-treated diabetic rats compared to vanadyl sulfate (VOSO₄)-treated diabetic rats, which suggested that the anti-diabetic activity of the element vanadium was elevated after being modified with an organic ligand. These results suggested that V5dipic-NH₂, as an organic vanadium compound, is more effective than inorganic vanadium salt at alleviating the symptoms of diabetes.     

The first examples of benzidinium cations templated low-dimensional molybdates

For the first time, use of benzidine as a structure-directing agent has resulted in the crystallization of two novel organic/inorganic hybrid molybdates under hydrothermal condition (180 °C and autogenous pressure). The presence of monoprotonated benzidinium ions in aqueous molybdate solution appears to engineer two new hybrid solids: one-dimensional chains in [H₂NC₁₂H₈NH₃]₂Mo₂O₇, 1 (a = 5.9686, b = 7.0761 and c = 14.3293 Å, α = 77.17°, β = 85.25° and γ = 88.56°; and Z = 2) and two-dimensional step-wise layered molybdate [H₂NC₁₂H₈NH₃]₂Mo₅O₁₆, 2 (a = 5.6843, b = 14.3024 and c = 19.4787Å, α = 108.1°, β = 98.4° and γ = 90.0°; , Z = 2). 1 is an unusual solid wherein the anionic chains are charge compensated by counter cations which also act as ligands to the metal and 2 is a new layered molybdate built of MoO₅ square pyramids and MoO₆ octahedra.     

Enhanced methane and hydrogen production from municipal solid waste and agro-industrial by-products co-digested with crude glycerol

The effects of crude glycerol on the performance of single-stage anaerobic reactors treating different types of organic waste were examined. A reactor treating the organic fraction of municipal solid waste produced 1400 mL CH₄/d before the addition of glycerol and 2094 mL CH₄/d after the addition of glycerol. An enhanced methane production rate was also observed when a 1:4 mixture of olive mill wastewater and slaughterhouse wastewater was supplemented with crude glycerol. Specifically, by adding 1% v/v crude glycerol to the feed, the methane production rate increased from 479 mL/d to 1210 mL/d. The extra glycerol-COD added to the feed did not have a negative effect on the reactor performance in either case. Supplementation of the feed with crude glycerol also had a significant positive effect on anaerobic fermentation reactors. Hydrogen yield was 26 mmole H₂/g VS added and 15 mmole H₂/g VS added in a reactor treating the organic fraction of municipal solid waste and a 1:4 mixture of olive mill and slaughterhouse wastewater. The addition of crude glycerol to the feed enhanced hydrogen yield at 2.9 mmole H₂/g glycerol added and 0.7 mmole H₂/g glycerol added.     

Aerobic oxygenation of organic sulfides using diruthenium activators

Diruthenium compounds supported by carboxylate or mixed carboxylate/carbonate bridging ligands were found to be active catalysts for aerobic oxygenation of organic sulfides. Ru₂(OAc)₃(CO₃) (A), Ru₂(O₂CCF₃)₃(CO₃) (B) and Ru₂(OAc)₄Cl (C) promote the conversion of organic sulfide to sulfoxide, and subsequently sulfone in an oxygen atmosphere at ca. 90 °C. The order of catalytic activity is A > B ? C. Catalytic reactions are operative in a number of 1:1 co-solvent-H₂O combinations, and the highest reactivity was found in aqueous media.     

Pretreatment and enzymic saccharification of water hyacinth cellulose

Water hyacinth was pretreated, under variable conditions, with NaOH, alkaline H₂O₂, peracetic acid and sodium chlorite. Combined pretreatments included sodium chlorite with each of NaOH, alkaline H₂O₂ and peracetic acid. Combined pretreatment with 0.1% NaClO₂ for 1 h at 100 °C and peracetic acid at 100 °C for 15 min afforded the most promising sample. The recovered lignin, cellulose and hemicellulose of this sample was 2.56%, 96.69%, and 81.38%, respectively. The same sample, by cellulase hydrolysis showed the highest cellulose conversion (80.8%) and 90% saccharification using 200 FPU/g substrate. Some ambient factors affecting saccharification of pretreated water hyacinth were investigated. Enzymic saccharification after 6 h was about 50% of that at 48 h, indicating a slow hydrolysis rate by time. Addition of 8% glucose at the beginning of the enzymic hydrolysis decreased the saccharification to about its half while addition of 8% ethanol brought about complete inhibition of the enzyme. Addition of cellobiase to the reaction mixture increased cellulose conversion and saccharification by 10%.     

Influence of carbohydrates and proteins concentration on fermentative hydrogen production using canteen based waste under acidophilic microenvironment

Functional role of biomolecules viz., carbohydrates and proteins on acidogenic biohydrogen (H₂) production was studied through the treatment of canteen based composite food waste. The performance was evaluated in an anaerobic sequencing batch reactor (AnSBR) at pH 6 with five variable organic loading conditions (OLR1, 0.854; OLR2, 1.69; OLR3, 3.38; OLR4, 6.54 and OLR5, 9.85 kg COD/m³-day). Experimental data depicted the feasibility of H₂ production from the stabilization of food waste and was found to depend on the substrate load. Among the five loading conditions studied, OLR4 documented maximum H₂ production (69.95 mmol), while higher substrate degradation (3.99 kg COD/m³-day) was observed with OLR5. Specific hydrogen yield (SHY) vary with the removal of different biomolecules and was found to decrease with increase in the OLR. Maximum SHY was observed with hexose removal at OLR1 (139.24 mol/kg Hexose_R at 24 h), followed by pentoses (OLR1, 108.26 mol/kg Pentose_R at 48 h), proteins (OLR1, 109.71 mol/kg Protein_R at 48 h) and total carbohydrates (OLR1, 58.31 mol/kg CHO_R at 24 h). Proteins present in wastewater helped to maintain the buffering capacity but also enhanced the H₂ production by supplying readily available organic nitrogen to the consortia. Along with carbohydrates and proteins, total solids also registered good removal.     

γ-Fe2O3 nanoparticle in NaY-zeolite matrix: Preparation, characterization, and heterogeneous catalytic epoxidation of olefins

Nano-sized crystals of maghemite iron oxide (γ-Fe₂O₃) were synthesized onto the surface of NaY-zeolite crystals by immobilizing a polynuclear iron complex [Fe₄O₂(O₂CCH₃)₇(bpy)₂](ClO₄) (bpy = 2,2′-bipyridine) and subsequent calcination of the material in oxygen. Superparamagnetic γ-Fe₂O₃ particles with sizes ∼5 nm were formed on the surface of the zeolite matrix. The nano-composite, γ-Fe₂O₃@NaY has been subsequently subjected for thorough characterization with several spectroscopic techniques as well as magnetic and transmission electron microscopic measurements. This confirms the formation of maghemite nanoparticles on a NaY-zeolite surface. γ-Fe₂O₃@NaY shows a remarkable catalytic efficiency in epoxidation reactions with various olefins using tert-BuOOH as oxidant. Notably, styrene shows a remarkable high conversion (90%) as well as epoxide selectivity (95%) while trans-stilbene is completely converted to its oxide with tert-BuOOH over a γ-Fe₂O₃@NaY catalyst.     

In situ preparation of magnetic Fe3O4-chitosan nanoparticles for lipase immobilization by cross-linking and oxidation in aqueous solution

A new and simple method has been proposed to prepare magnetic Fe₃O₄-chitosan (CS) nanoparticles by cross-linking with sodium tripolyphosphate (TPP), precipitation with NaOH and oxidation with O₂ in hydrochloric acid aqueous phase containing CS and Fe(OH)₂, and these magnetic CS nanoparticles were used to immobilize lipase. The effects on the sequence of adding NaOH and TPP, the reaction temperature, and the ratio of CS/Fe(OH)₂ were studied. TEM showed that the diameter of composite nanoparticles was about 80 nm, and that the magnetic Fe₃O₄ nanoparticles with a diameter of 20 nm were evenly dispersed in the CS materials. Magnetic measurement revealed that the saturated magnetisation of the Fe₃O₄-CS nanoparticles could reach 35.54 emu/g. The adsorption capacity of lipase onto nanoparticles could reach 129 mg/g; and the maximal enzyme activity was 20.02 μmol min⁻¹ mg⁻¹ (protein), and activity retention was as high as 55.6% at a certain loading amount.     

Acidogenic fermentation of vegetable based market waste to harness biohydrogen with simultaneous stabilization

Vegetable based market waste was evaluated as a fermentable substrate for hydrogen (H₂) production with simultaneous stabilization by dark-fermentation process using selectively enriched acidogenic mixed consortia under acidophilic microenvironment. Experiments were performed at different substrate/organic loading conditions in concurrence with two types of feed compositions (with and without pulp). Study depicted the feasibility of H₂ production from vegetable waste stabilization process. H₂ production was found to be dependent on the concentration of the substrate and composition. Higher H₂ production and substrate degradation were observed in experiments performed without pulp (23.96 mmol/day (30.0 kg COD/m³); 13.96 mol/kg COD_R (4.8 kg COD/m³)) than with pulp (22.46 mmol/day (32.0 kg COD/m³); 12.24 mol/kg COD_R (4.4 kg COD/m³)). Generation of higher concentrations of acetic acid and butyric acid was observed in experiments performed without pulp. Data enveloping analysis (DEA) was employed to study the combined process efficiency of system by integrating H₂ production and substrate degradation.     

Transesterification of Nannochloropsis oculata microalga’s lipid to biodiesel on Al2O3 supported CaO and MgO catalysts

In this study, we present the activities of Al₂O₃ supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 °C. We found that pure CaO and MgO were not active and CaO/Al₂O₃ catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al₂O₃ catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.     

Water gas shift reaction and nitrobenzene reduction catalysis by tetracarbonyldi-μ-chlorodirhodium(I) complex immobilized on poly(4-vinylpyridine)

The preparation, characterization and catalytic properties of Rh₂(CO)₄Cl₂ immobilized on poly(4-vinylpyridine) are reported. The polymer-immobilized Rh catalyst in contact with 80% aqueous 2-ethoxyethanol is active for the water gas shift reaction and nitrobenzene reduction to azoxybenzene under carbon monoxide at 100 °C. The polymer-immobilized Rh complex was found to be reusable. The Rh complex was coordinatively bonded to the pyridine groups of the organic polymer as suggested by UV-Vis/diffuse reflectance (UV-Vis/DR), Fourier transform infrared (FT-IR), and electron paramagnetic resonance (EPR) spectroscopies. The morphology and the elemental analysis of the immobilized catalyst were studied by scanning electron microscopy-energy dispersive X-ray (SEM-EDX) technique.     

A simple aqueous phase synthesis of high surface area aluminum fluoride and its bulk and surface structure

A simple novel synthesis route to aluminum fluoride, AlF₃, from aqueous phase is reported. Al₂O₃ is dissolved in aqueous hydrofluoric acid, HF, and re-precipitated as AlF₃ · 3H₂O. Thermal decomposition results in thermally stable AlF₃ with high specific surface areas between 120 and 60 m²/g depending on treatment temperatures (up to 450 °C). Bulk and surface structures of the resulting amorphous and crystalline materials were characterized by X-ray powder diffraction, infrared and solid state NMR spectroscopy (²⁷Al, MAS), nitrogen physisorption and adsorption of paramagnetic probe molecules (vanadium complexes).     

Insulin-enhancing activity of a dinuclear vanadium complex: 5-chloro-salicylaldhyde ethylenediamine oxovanadium(V) and its permeability and cytotoxicity

A new insulin-enhancing oxovanadium complex 5-chloro-salicylaldhyde ethylenediamine oxovanadium (V) ([V₂O₂(μ-O)₂L₂]) has been synthesized. The complex was characterized by a variety of physical methods, including X-ray crystallography. The X-ray diffraction analysis show a dinuclear complex of two six-coordinate vanadium centers doubly bridged by the oxygen atoms of the Schiff base ligand with a V₂O₂ diamond core. The complex was administered intragastrically to STZ-diabetic rats for 2 weeks. The biological activity results show that the complex at the dose of 10.0 and 20.0 mg V kg^− 1, could significantly decrease the blood glucose level and ameliorate impaired glucose tolerance in STZ-diabetic rats. That results suggested that the complex exerts an antidiabetic effect in STZ-diabetic rats. Furthermore, the complex ([V₂O₂(μ-O)₂L₂]) had permeability above 10^− 5 cm/s. The experimental results suggested that the vanadium complex permeates via a passive diffusion mechanism. It was also suggested the complex with salen-type ligands has good lipophilic properties and better oral administration. The cytotoxicity of the complex ([V₂O₂(μ-O)₂L₂]) on Caco-2 cells was measured by a decrease of cell viability using the MTT assay suggesting that the chlorine atom at C4 of complex [V₂O₂(μ-O)₂L₂] increased cytotoxicity for vanadium complexes.     

Synthesis, characterization and antioxidant activity of water soluble Mn complexes of sulphonato-substituted Schiff base ligands

Two new Mn^III complexes Na[Mn(5-SO₃-salpnOH)(H₂O)] ⋅ 5H₂O (1) and Na[Mn(5-SO₃-salpn)(MeOH)] ⋅ 4H₂O (2) (5-SO₃-salpnOH = 1,3-bis(5-sulphonatosalicylidenamino)propan-2-ol, 5-SO₃-salpn = 1,3-bis(5-sulphonatosalicylidenamino)propane) have been prepared and characterized. Electrospray ionization-mass spectrometry, UV-visible and ¹H NMR spectroscopic studies showed that the two complexes exist in solution as monoanions [Mn(5-SO₃-salpn(OH))(solvent)₂]⁻, with the ligand bound to Mn^III through the two phenolato-O and two imino-N atoms located in the equatorial plane. The E_1/2 of the Mn^III/Mn^II couple (−47.11 (1) and −77.80 mV (2) vs. Ag/AgCl) allows these complexes to efficiently catalyze the dismutation of , with catalytic rate constants 2.4 × 10⁶ (1) and 3.6 × 10⁶ (2) M⁻¹ s⁻¹, and IC₅₀ values of 1.14 (1) and 0.77 (2) μM, obtained through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. The two complexes are also able to disproportionate up to 250 equivalents of H₂O₂ in aqueous solution of pH 8.0, with initial turnover rates of 178 (1) and 25.2 (2) mM H₂O₂ min⁻¹ mM⁻¹ catalyst⁻¹. Their dual superoxide dismutase/catalase activity renders these compounds particularly attractive as catalytic antioxidants.     

Toward an expanded oxygen atom transfer reactivity scale: Computational investigation of the energetics of oxo transfer reaction couples

The computational prediction of gas phase enthalpy (neutral substrates) and aqueous free energy (anion substrates) changes has been evaluated for the oxygen atom transfer reaction X + 1/2O₂ → XO. Several density functionals (SVWN, BP86, B3LYP) at double- and triple-ζ levels were surveyed, along with one composite ab initio method (G3(MP2)). Results are presented for extensive main group test sets for which experimental thermochemistry is available. In addition, several minimal reaction couples of the type [M^IVOL₂]/[M^VIO₂L₂] (M = Mo, W) have been examined. Overall, the results suggest a computational approach to the energetics of oxo transfer is feasible, potentially affording an expanded oxo transfer reactivity scale.