Influence of pyrolysis temperature and time on the cellulose fast pyrolysis products: Analytical Py-GC/MS study

Analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to achieve fast pyrolysis of cellulose and on-line analysis of the pyrolysis vapors. Experiments were performed to reveal the effects of pyrolysis temperature and time on the distribution of the pyrolytic products, especially the formation characteristics of eighteen important products. During the fast pyrolysis process, the cellulose started decomposition to form organic volatile products at the set pyrolysis temperature of 400 °C. The pyrolytic products included various anhydrosugars (dominated by the levoglucosan (LG)), anhydrosugar derivatives (mainly the levoglucosenone (LGO), 1,4:3,6-dianhydro-α-d-glucopyranose (DGP), 1,5-anhydro-4-deoxy-d-glycero-hex-1-en-3-ulose (APP) and 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC)), furan compounds (typically the 5-hydroxymethyl-furfural (HMF), furfural (FF) and furan (F)), as well as light linear carbonyls (mainly the hydroxyacetaldehyde (HAA) and 1-hydroxy-2-propanone (HA)). These products were generated with different characteristics. The LG was the most important product, it was thermally stable, and its formation was favored at elevated pyrolysis temperature and time. Most of the other products were also enhanced at elevated pyrolytic conditions. However, some products, such as the LGO, were favorable to be produced at low temperatures. Based on these characteristics, discussion was performed on the possible pyrolytic pathways for the formation of the important products.     

Characterization of the water-insoluble pyrolytic cellulose from cellulose pyrolysis oil

Water-insoluble pyrolytic cellulose with similar appearance to pyrolytic lignin was found in cellulose fast pyrolysis oil. The influence of pyrolysis temperature on pyrolytic cellulose was studied in a temperature range of 300–600 °C. The yield of the pyrolytic cellulose increased with temperature rising. The pyrolytic cellulose was characterized by various methods. The molecular weight distribution of pyrolytic cellulose was analyzed by gel permeation chromatography (GPC). Four molecular weight ranges were observed, and the M_w of the pyrolytic cellulose varied from 3.4 × 10³ to 1.93 × 10⁵ g/mol. According to the elemental analysis (EA), the pyrolytic cellulose possessed higher carbon content and lower oxygen content than cellulose. Thermogravimetric analysis (TGA) indicated that the pyrolytic cellulose underwent thermo-degradation at 127–800 °C and three mass loss peaks were observed. Detected by the pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), the main pyrolysis products of the pyrolytic cellulose included saccharides, ketones, acids, furans and others. Fourier transforms infrared spectroscopy (FTIR) also demonstrated that the pyrolytic cellulose had peaks assigned to CO stretching and glycosidic bond, which agreed well with the Py-GC/MS results. The pyrolytic cellulose could be a mixture of saccharides, ketones, and their derivatives.     

Catalytic effects of copper(II) chloride and aluminum chloride on the pyrolytic behavior of cellulose

The cellulose without and with catalyst (CuCl₂, AlCl₃) was subjected to pyrolysis at temperatures from 350 to 500 °C with different heating rate (10 °C/min, 100 °C/s) to produce bio-oil and selected chemicals with high yield. The pyrolytic oil yield was in the range of 37–84 wt% depending on the temperature, the heating rate and the amount of metal chloride. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil. The mixing cellulose with both metal chlorides results with a significant decrease of the liquid product. The non-catalytic pyrolysis of cellulose gives the highest mass yield of levoglucosan (up to 11.69 wt%). The great influence of metal chloride amount on the distribution of bio-oil components was observed. The copper(II) chloride and aluminum chloride addition to cellulose clearly promotes the formation of levoglucosenone (up to 3.61 wt%), 1,4:3,6-dianhydro-α-d-glucopyranose (up to 3.37 wt%) and unidentified dianhydrosugar (MW = 144; up to 1.64 wt%). Additionally, several other compounds have been identified but in minor quantities. Based on the results of the GC–MS, the effect of pyrolysis process conditions on the productivity of selected chemicals was discussed. These results allowed to create a general model of reactions during the catalytic pyrolysis of cellulose in the presence of copper(II) chloride and aluminum chloride.     

Pyrolytic behavior of cellulose in presence of montmorillonite K10 as catalyst

Cellulose and cellulose/montmorillonite K10 mixtures of different ratio (9:1, 3:1, 1:1) were subjected to pyrolysis at temperatures from 350 to 500 °C with different heating rate (10 °C/min, 100 °C/s) to produce bio-oil and selected chemicals with high yield. The pyrolytic oil yield was in the range of 46–73.5 wt% depending on the temperature, the heating rate and the amount of catalyst. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil (84 wt%). The blending cellulose with increasing amount of montmorillonite K10 results in significant, linear decrease in bio-oil yield. The great influence of montmorillonite K10 amount on the distribution of bio-oil components was observed at 450 °C with a heating rate of 100 °C/s. The addition of catalyst to cellulose promotes the formation of 2-furfural (FF), various furan derivatives, levoglucosenone (LGO) and (1R,5S)-1-hydroxy-3,6-dioxabicyclo-[3.2.1]octan-2-one (LAC). Simultaneously, the share of levoglucosan (LG) in bio-oil decreases from 6.92 wt% and is less than 1 wt% when cellulose:MK10 (1:1, w/w) mixture at 450 °C is rapidly pyrolyzed. Additionally, several other compounds have been identified but in minor quantities. Their contributions in bio-oil also depend on the amount of catalyst.     

Sc(OTf)3/TsOH: a highly efficient catalytic system for the synthesis of 2,6-dioxabicyclo[3,2,1]octane derivatives

A variety of aldehydes undergo a tandem acetalization and intramolecular Prins cyclization with pent-4-ene-1,2-diol in the presence of 5 mol % scandium triflate and 15 mol % p-toluenesulfonic acid (TsOH) in dichloroethane at 80 °C to produce the corresponding bicyclic ethers, that is, 2,6-dioxabicyclo[3,2,1]octane derivatives in good yields and with high selectivity. The salient features of this methodology are higher yields, lower catalyst loadings, and faster reaction times. The combination of Sc(OTf)₃ and TsOH (1:3) was found to be more effective than either Sc(OTf)₃ or TsOH alone.     

Analytical study on the pyrolytic behaviour of cellulose in the presence of MCM-41 mesoporous materials

The effect of different mesoporous materials of the MCM-41 type on the pyrolytic behaviour of cellulose was evaluated by off-line analytical pyrolysis followed by GC–MS analysis of the evolved products trapped onto a XAD-2 resin. Siliceous MCM-41 (Si-MCM-41) and Me-MCM-41 catalysts containing different metals, namely Al, Mg, Ti, Sn or Zr, were synthesised and investigated utilising the same catalyst/cellulose mass ratio 1:3. The effect of the catalysts was evaluated by quantifying the yields of the following pyrolysis products: (2H)-furan-3-one, 2-furaldehyde, 5-methyl-2-furaldehyde, 4-hydroxy-5,6-dihydro-pyran-2-one, levoglucosenone, 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC), 1,4:3,6-dianhydro-α-d-glucose and levoglucosan. All the examined mesostructured solids decreased the yields of levoglucosan with respect to uncatalysed cellulose, and increased the production of levoglucosenone and LAC. The effect was higher with doped MCM-41 in comparison to Si-MCM-41. The formation of other pyrolysis products was less influenced by the catalyst. The activity of Sn-MCM-41 was further investigated by preparative pyrolysis with a fixed bed quartz reactor. This catalyst gave rise to a pyrolytic liquid enriched in LAC and depleted in levoglucosan, and could be re-used six times after regeneration without apparent loss of activity.     

Investigation of porosity and fractal properties of the pyrolytic MnO2 films in the capacitor structure

The cathode of solid metal oxide-semiconductor capacitors is considered as the semiconductor, MnO₂, obtained by means of impregnation of the anode with Mn(NO₃)₂ solutions within pyrolytic decomposition. Stability range of capacitor structure is mainly determined by the amount of water contained by manganese dioxide, which ensure compaction of contacts between capacitors due to packing of cavities in MnO₂, i.e. depends on open porosity of pyrolytic layer. At the same time it is known that the whole range of differently characterized microporous objects display their fractal properties. Taking all this into account the present paper is concerned on investigation of microporosity and fractal properties of pyrolytic MnO₂ films by small-angle X-ray scattering method. It has been determined that the major contribution to the submicropores volume concentration is made by submicropores not exceeding 8 nm. The MnO₂ layers are fractal structures with the value of volume fractal dimension D = 2.87.     

Self-assembled Li4Ti5O12/TiO2/Li3PO4 for integrated Li–ion microbatteries

This work aims to maximize the number of active sites for energy storage per geometric area, by approaching the investigation to 3D design for microelectrode arrays. Self-organized Li₄Ti₅O₁₂/TiO₂/Li₃PO₄ composite nanoforest layer (LTL) is obtained from a layer of self organized TiO₂/Li₃PO₄ nanotubes. The electrochemical response of this thin film electrode prepared at 700 °C exhibited lithium insertion and de-insertion at 1.55 and 1.57 V respectively, which is the typical potential found for lithium titanates. The effects of lithium phosphate on lithium titanate are explored for the first time. By cycling between 2.7 and 0.75 V the LTL/LiFePO₄ full cell delivered 145 mA h g^− 1 at an average potential of 1.85 V leading to an energy density of 260 W h kg^− 1 at C/2. Raman spectroscopy revealed that the γ-Li₃PO₄/lithium titanate structure is preserved after prolonged cycling. This means that Li₃PO₄ plays an important role for enhancing the electronic conductivity and lithium ion diffusion.     

Characterization of the different fractions obtained from the pyrolysis of rope industry waste

A study of the possibilities of pyrolysis for recovering wastes of the rope's industry has been carried out. The pyrolysis of this lignocellulosic residue started at 250 °C, with the main region of decomposition occurring at temperatures between 300 and 350 °C. As the reaction temperature increased, the yields of pyrolyzed gas and oil increased, yielding 22 wt.% of a carbonaceous residue, 50 wt.% tars and a gas fraction at 800 °C. The chemical composition and textural characterization of the chars obtained at various temperatures confirmed that even if most decomposition occurs at 400 °C, there are some pyrolytic reactions still going on above 550 °C. The different pyrolysis fractions were analyzed by GC–MS; the produced oil was rich in hydrocarbons and alcohols. On the other hand, the gas fraction is mainly composed of CO₂, CO and CH₄. Finally, the carbonaceous solid residue (char) displayed porous features, with a more developed porous structure as the pyrolysis temperature increased.     

Ni–Al hydrotalcite-like material as the catalyst precursors for the dry reforming of methane at low temperature

Nickel–aluminium and magnesium–aluminium hydrotalcites were prepared by co-precipitation and subsequently submitted to calcination. The mixed oxides obtained from the thermal decomposition of the synthesized materials were characterized by XRD, H₂-TPR, N₂ sorption and elemental analysis and subsequently tested in the reaction of methane dry reforming (DRM) in the presence of excess of methane (CH₄/CO₂/Ar = 2/1/7). DMR in the presence of the nickel-containing hydrotalcite-derived material showed CH₄ and CO₂ conversions of ca. 50% at 550 °C. The high values of the H₂/CO molar ratio indicate that at 550 °C methane decomposition was strongly influencing the DRM process. The sample reduced at 900 °C showed better catalytic performance than the sample activated at 550 °C. The catalytic performance in isothermal conditions from 550 °C to 750 °C was also determined.     

L-Glutamic acid loaded collagen chitosan composite scaffold as regenerative medicine for the accelerated healing of diabetic wounds

Diabetic wounds (DWs) are characterized by prolonged inflammation, which poses a significant challenge for clinicians and researchers to promote healing. In this study, we fabricate L-Glutamic acid (LGA) loaded collagen/chitosan (COL-CS) composite scaffold for the accelerated healing of DW. The characterization outcomes of the composite scaffold revealed that a crosslinked scaffold holds optimum porosity, low matrix degradation, and sustained drug release in contrast to a non-crosslinked scaffold. In vitro, LGA composite scaffolds have not exhibited any toxicity on 3T3L1 cell lines. In vivo, the LGA composite scaffold has shown significantly (p < 0.001), higher rates of wound contraction than those in control and COL-CS scaffold treated groups. In addition, MMP-9 levels were also significantly reduced in LGA composite scaffold-treated group compared with those in the control and COL-CS scaffold treated group. Thus, the LGA composite scaffold may serve as a promising therapy in DW due to its unique modulatory effect on inflammatory biomarker MMP-9.     

Li2ZnTi3O8 nanorods: A new anode material for lithium-ion battery

Spinel Li₂ZnTi₃O₈ nanorods were first synthesized using titanate nanowires as a precursor. The synthesized nanorods are highly crystalline and used as an anode material in a rechargeable Li-ion battery. A large capacity of 220 mA h g^? 1 was kept after 30 cycles at a current density of 0.1 A g^? 1, which is close to the theoretic capacity. The electrochemical measurements indicate that the anode material made of spinel Li₂ZnTi₃O₈ nanorods displayed a highly reversible capacity and excellent cycling stability.     

Electrochemical formation of self-organized zirconium titanate nanotube multilayers

The present work reports the formation of multilayers of self-organized zirconium titanate nanotubes by anodizing a Ti–35Zr alloy in 1 M (NH₄)₂SO₄ + 0.5 wt% NH₄F electrolytes. It was found that multilayers consisting of different diameter nanotubes can be produced by repeated anodization steps under different conditions. Formation of new nanotubes starts in the gaps between the existing tubes. The process allows the formation of multilayer stacks consisting of layers of several 100 nm in length and adjustable nanotube diameters in a range from 50 to 180 nm.     

Square-wave voltammetric determination of thallium using surface modified thick-film graphite electrode with Bi nanopowder

Trace analysis of thallium at surface modified thick-film graphite electrode with Bi nanopowder has been carried out using square-wave anodic stripping voltammetry (SWASV) technique. The Bi nanopowder electrode exhibited a well-defined response relating to the oxidation of Tl. From the linear relationship between Tl concentration and peak current, the sensitivity of the Bi nanopowder electrode was quantitatively estimated. The detection limit of Tl was determined to be 0.03 μg/L for 1.0 μg/L Tl solution under 10 min accumulation, which is lower than the reported values for a Bi film electrode. Furthermore, it is confirmed that EDTA addition effectively eliminates the Pb and Cd interferences in the course of Tl determination by forming complexes with Pb²⁺ and Cd²⁺.     

Demetallation of methemoglobin in cellulose nanofibril–TiO2 nanoparticle composite membrane electrodes

Porous composite films containing cellulose nanofibrils (from sisal) and TiO₂ nanoparticles (ca. 6 nm diameter) are obtained in a layer-by-layer assembly process. Each layer consists of ca. 0.18 μg cellulose nanofibrils and ca. 0.72 μg TiO₂ (determined by QCMB) and adds a thickness of ca. 16 nm (by AFM) to the uniform deposit. The TiO₂ nanophase is creating conducting pathways for electrons in a relatively open cellulose structure (ca. 82% open pores) potentially suitable for the immobilization of large redox proteins such as methemoglobin.Methemoglobin is shown to readily adsorb into the cellulose–TiO₂ film. However, electrochemical responses for the immobilized methemoglobin in aqueous 0.1 M phosphate buffer at pH 5.5 suggest that facile demetallation occurs. Experiments with Fe³⁺ in the absence of protein result in voltammetric responses indistinguishable from those observed for immobilized methemoglobin. In the presence of ethylenediamine tetraacetic acid (EDTA) the voltammetric signals for the Fe³⁺ immediately disappear. Complementary experiments conducted in 0.1 M acetate buffer at pH 5.5 demonstrate that methemoglobin can indeed be immobilized in electrochemically active form and without demetallation loss of the voltammetric signal in the presence of EDTA. Demetallation appears to occur (i) in the presence of phosphate, (ii) at pH 5.5, (iii) and in the presence of a charged surface.     

Bismuth nano-powder electrode for trace analysis of heavy metals using anodic stripping voltammetry

In the present work, a more sensitive and conveniently usable electrode sensor for a trace analysis of heavy metal was developed by using Bi nanopowder synthesized by levitational gas condensation (LGC) method. It was observed from the TEM image that the Bi nanopowder is spherical in shape with a size of nearly 50 nm. The XRD pattern revealed intense peaks which can be indexed as a rhombohedral structure of Bi without any other diffraction peaks corresponding to an oxide or an impurity. This indicates that the resulting nanopowder synthesized by the LGC method is a highly crystallized Bi with a high purity. The square wave anodic stripping voltammograms (SWASV), experimentally measured for the Bi nanopowder electrode, showed well-defined and highly reproducible electrochemical responses relating to the stripping of Cd and Pb. The detection limit of the electrode was estimated to be 0.15 μg/l and 0.07 μg/l for Cd and Zn, respectively, on the basis of the signal-to-noise characteristics (S/N = 3) of the response for the 1.0 μg/l solution under a 10 min accumulation.     

Reversible lithium storage in Na2Li2Ti6O14 as anode for lithium ion batteries

The sodium lithium titanate with composition Na₂Li₂Ti₆O₁₄ has been synthesized by a sol–gel method. Thermogravimetric analysis and differential thermal analysis (TG–DTA) of the thermal decomposition process of the precursor and X-ray diffraction (XRD) data indicate the crystallization of sodium lithium titanate has occurred at about 600 °C. Electrochemical lithium insertion into Na₂Li₂Ti₆O₁₄ for lithium ion battery has been investigated for the first time. These results indicate the discharge and charge potential plateaus are about 1.3 V. The initial discharge capacity is much higher than the charge capacity and irreversible capacity exists in the voltage window 1–3 V. Subsequently, the discharge capacity decreases slowly, but the charge capacity increases slightly in the following cycles. After a few cycles, the specific capacity remains almost constant values and the sample exhibits the excellent retention of capacity on cycling.     

Determination of the activities in the (Ni + Al) alloys in the temperature range 870 K to 920 K by a solid-state galvanic cell using a CaF2 electrolyte

The activities of aluminium and nickel are constituents in the (Ni + Al) superalloys in the concentration range 50 mol% to 70 mol% of Al at the temperatures (870, 900, and 920) K were determined with the help of solid-state galvanic cells involving calcium fluoride as an electrolyte. The partial molar Gibbs free energies of aluminium and nickel in the alloys, and the Gibbs free energy of mixing were calculated from the e.m.f. data. The values of the standard Gibbs free energies of formation of the intermetallic compounds NiAl, Ni₂Al₃, and NiAl₃ are also given.     

Solid/liquid- and vapor-phase interactions between cellulose- and lignin-derived pyrolysis products

Solid/liquid- and vapor-phase interactions between cellulose- and lignin (Japanese cedar milled wood lignin)-derived pyrolysis products were studied under the conditions of N₂/600 °C/40–80 s. A dual-space closed ampoule reactor was used to eliminate the solid/liquid-phase interactions, and careful comparison of the resulting data with those of the pyrolysis of the mixed samples gave some insights into the solid/liquid- and vapor-phase interactions separately. With the solid/liquid-phase interactions, the tar yields from both cellulose and lignin increased with the decreasing yields of the char fractions in a short pyrolysis time of 40 s (primary pyrolysis stage). Most of the identified tar components from cellulose and lignin increased in their yields. The vapor-phase interactions were significant at a longer pyrolysis time of 80 s (secondary reaction stage) when the methoxyl groups of the lignin-derived volatiles were cleaved homolytically. The vapor-phase interactions accelerated the gas formation from the cellulose-derived volatiles with suppressing the vapor-phase char formation of the lignin-derived volatiles. The yields of methane and catechols from lignin also increased greatly instead of the formation of o-cresols. Most of these influences are explained with a proposed interaction mechanism, in which the cellulose-derived volatiles act as H-donors while the lignin-derived volatiles (radicals) act as H-acceptors.     

Photolysis of glyoxal in air

The photolysis of glyoxal in synthetic air was investigated in a quartz cell at 298 K using three types of UV sources (TL/12 lamps (275–380 nm), TL/03 lamps (390–470 nm) and mercury lamps (254 nm)) and products were identified and quantitatively analyzed using long-path FTIR spectroscopy. For all light sources, the observed products were CO, HCHO and HCOOH. Absolute quantum yields were determined using Cl₂ and Br₂ as actinometers. Photolysis in the first absorption band of glyoxal, using TL/12 lamps, provided an overall quantum yield of Φ_T = 0.97 ± 0.05, independent of total pressure ranging from 100 to 700 Torr air. The absolute quantum yields obtained with the TL/03 lamps, covering the second absorption band of glyoxal, showed dependency on total pressure, ranging from Φ_T = 0.12 at 100 Torr to Φ_T = 0.042 at 700 Torr, which can be expressed as a Stern–Volmer-type equation 1/Φ_T = (6.80 + 251.8) × 10⁻⁴ × P (Torr).By combining the product yields with literature data, we deduced the detailed picture of glyoxal photolysis, including the dependency of the quantum yield of each particular channel: CHOCHO + hν → 2HCO (Φ₁); CHOCHO + hν → H₂ + 2CO (Φ₂); CHOCHO + hν → H₂CO + CO (Φ₃) on the applied wavelength. The product quantum yields indicate that dissociation into two HCO radicals is the most important pathway under atmospheric conditions. The mean photolysis rate was measured under solar radiation in the EUPHORE outdoor chamber to be J_obs = 1.04 ± 0.10 × 10⁻⁴ s⁻¹, corresponding to a mean effective quantum yield ϕ_eff = 0.035 ± 0.007. Although glyoxal has a very low effective quantum yield, photolysis remains an important removal path in the atmosphere.