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•The duration of rehydration and drying steps influences the physico-chemical properties of reconstructed hydrotalcites and their performance in aldol condensation of furfural and ...acetone.•Liquid-phase rehydration of Mg-Al mixed oxide results in the recovery of HTC structure in several seconds and the replacement of >90% carbonate groups by hydroxyls as evidenced by TGA-MS.•Rehydration time has only little effect on the performance of reconstructed hydrotalcite in aldol condensation while its excessive dehydration substantially decreases the catalyst activity.
Aldol condensation in presence of reconstructed hydrotalcites as basic catalysts is well documented and attracts an increased attention because it allows producing complex molecules starting from relatively simpler ones. Nevertheless, more studies are necessary for the better understanding of preparation factors that affect the physico-chemical properties of these materials and their catalytic performance. This work considers the effect of the duration of the liquid-phase rehydration of Mg-Al mixed oxide as well as the drying duration of prepared samples on their physico-chemical properties and performance in aldol condensation of furfural and acetone. The properties of all materials were investigated by XRD, TGA, TGA-MS, SEM and DRIFT. Experiments on aldol condensation of furfural and acetone were performed by using a stirred batch reactor at T=25°C with Ac:F=5 molar ratio. The characterization of the prepared materials showed that the recovery of HTC structure occurred within a few seconds of the contact between Mg-Al mixed oxide with liquid water. The content of functional species in all reconstituted HTCs was nearly constant and independent on preparation conditions while the amount of physisorbed water in the prepared samples decreased with increasing drying time. The calcination of as-prepared HTC followed by the subsequent rehydration of Mg-Al mixed oxide resulted in the replacement of >90% carbonate groups on hydroxyls which are Brønsted basic sites. Consequently, the activity of the reconstructed HTCs in aldol condensation of furfural and acetone was significantly higher compared to Mg-Al mixed oxide. The catalytic performance of rehydrated materials was almost independent on rehydration time while furfural conversion decreased if carrying out the reaction in an aqueous medium with increased water content. On the other hand, properly dried reconstructed HTC with the absence of physisorbed water also exhibited a very low activity in the reaction. The effect of Cannizzaro reaction as a simultaneous process with aldol condensation on the composition of reaction products was also considered. The obtained results may be useful for optimizing the preparation conditions of reconstructed HTC as a basic catalyst as well as for evaluating their performance during long-term catalytic tests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The present paper deals with the flame retardancy study of model compound Poly(vinyl acetate) (PVAc) blended with ammonium poly(phosphate) (APP) as flame retardant. APP shows good activity within ...PVAc in fire tests at low mixing ratios in terms of reduction of rate of heat release (RHR). Creating difference thermograms by means of thermogravimetric analysis (TGA) learned that the classic deacetylation step of the polymer is accelerated by the presence of APP in the composite, followed by stabilisation of the formed char.
A systematic model to investigate chemical decomposition reactions of blends of polymers with flame retardants is introduced to build a complete mechanistic reaction model. To perform this, both evolved gas and solid state analysis of intermediate products are coupled. For the combination of PVAc and APP, APP breaks into monophosphate during the deacetylation step of PVAc and fully cross-links with the polymer by P–O–C cross-link bonds. The formed cross-linked material further aromatises in an oxidative environment and is highly stabilised as was shown using difference thermograms: blends of PVAc and APP appear to be more than 20% stable at 600 °C in comparison with the decomposition of the pure materials. At elevated temperatures, the phosphate structure degrades, leading to the full evaporation of the carbonaceous residue within the char.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Carbon blacks with lower specific surface area had basic character (electron donor) due to CO and CO groups.•Carbon blacks with higher specific surface area had acidic character (acceptor electron) ...due to OH groups.•Total surface energy and its dispersive component of carbon blacks increased by increasing their specific surface area.
Carbon blackBET surface area (m2/g)KA/KDKA+KDC32320.8170.169C71710.6810.190C1591591.1270.151C1781781.6040.138
Four carbon blacks with different specific surface areas and surface chemistries (C32, C71, C159 and C178) were analyzed by transmission electron microscopy (TEM) and nitrogen adsorption isotherms at 77K. Their surface chemistries were analyzed by X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis coupled with mass spectrometry (TGA-MS) and inverse gas chromatography (IGC). The carbon blacks contained 2.7–5.8wt% volatiles corresponding to OH, CO, CO and COO groups. The surface chemistry parameters obtained with the different experimental techniques were inter-related by using chemometric statistical analysis tools. The application of this methodology showed that the carbon blacks with lower specific surface area (C32 and C71) had basic character (electron donor) mainly due to CO and CO groups, whereas the carbon black with the highest specific surface area (C178) showed acidic character (acceptor electron) due to its high content of OH groups. Moreover, the total surface energy and the dispersive component of the surface energy of the carbon blacks increased with the increase of their specific surface area. In general the specific interactions of the carbon blacks also increased with the increase of their specific surface area although C71 is exceptional due to higher oxygen content corresponding to CO groups.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•Effect of harvesting time on thermal decomposition of a green microalga was studied.•Maximum biomass productivity was recorded at the late exponential phase (LEP).•Biomass harvested ...at LEP showed the highest relative contents of aliphatic hydrocarbons.•Biomass harvested at LEP showed the lowest nitrogenous compounds.•LEP was suggested as the best growth phase for high biomass and upgraded bio-oil production.
Nowadays, microalgae are widely discussed as a promising feedstock for biofuel production. For higher crude bio-oil yield with good quality, microalgal biomass productivity and bio-oil characteristics are essential parameters. However, the same microalgal species has different chemical compositions at different growth phases. Therefore, the present study aimed to identify the best growth phase for high biomass productivity and optimal bio-oil production from the green microalga Micractinium conductrix via Py-GC/MS and TGA/MS analysis. M. conductrix was grown in a tubular photobioreactor and harvested at early exponential phase (EEP), middle exponential phase (MEP), late exponential phase (LEP) and stationary phase (STP). LEP showed the maximum significant (P ≤ 0.05) biomass productivity of 0.058 ± 0.004 g L−1 d-1, with maximum significant lipid and carbohydrate contents (28.7 ± 1.1 and 42.9 ± 1.2%dw, respectively). TGA/MS results confirmed that biomass harvested at MEP and LEP showed higher extent of conversion or mass loss reaction via thermal degradation with the lowest residual solid products. In addition, the hydrocarbon fragments in gaseous products (H2, C2H6, CH4, C2H4) from TGA/MS analysis were found to be released more abundantly at LEP. Moreover, Py-GC/MS results revealed that thermal decomposition of biomass harvested at LEP resulted in the highest significant relative contents of aliphatic hydrocarbons (41.2%) with lowest nitrogen-containing compounds (6.3%). The present study showed the significant impact of harvest time of microalgae on products characteristics of thermal decomposition and nominated LEP as the optimum growth phase to harvest M. conductrix for upgraded bio-oil production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Catalytic and non-catalytic co-gasification process using dolomite were carried out.•The catalytic and non-catalytic binary and ternary blend reactivities were examined.•Gaseous products released ...during the process were evaluated by TGA-MS.•Synergistic/antagonistic effects of catalytic and non-catalytic blends were studied.•Morphology of remaining residues on the gasification process were analysed by SEM.
The dolomite effect on the co-gasification process for binary and ternary blends of coal, petcoke and olive pomace was studied by thermogravimetric analysis (TGA) coupled with mass spectrometry (MS). Additionally, gas emissions, the synergistic effect and the residue morphology obtained were also evaluated. Ternary blends showed lower weight loss and higher reactivity than binary ones during gasification. Weight loss in the binary and ternary blends containing dolomite was lower than in the parent ones. Regarding gas emissions, the highest H2/CO ratio and the lowest sulphur and nitrogen compound emissions were obtained for the binary blend of petcoke and olive pomace containing dolomite. On the other hand, the highest synergistic effect was observed in the binary blend containing dolomite. To sum up, the best results were obtained when dolomite was in the blend in which the higher H2/CO ratio, synergistic effect and reactivity and lower pollutant emissions were observed. Finally, the residue obtained from the co-gasification process could be used as an adsorbent for removing pollutant gases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•The thermochemical properties of the different palm oil biomasses were investigated.•Palm oil biomasses are advantageous to pyrolysis processes for clean energy generation.•Empty fruit bunches (EFB) ...pyrolysis indicated the highest yield of the bio-oil.•Palm kernel shell (PKS) bio-oil showed high quantity of phenolic compounds.
The accurate determination of the biomass thermal properties is particularly important while studying biomass pyrolysis processes. The aim of this study is to investigate the different palm oil biomass samples (palm kernel shell (PKS), empty fruit bunches (EFB) and palm mesocarp fiber (PMF)) thermochemical behavior during pyrolysis. Thermogravimetric analysis coupled with spectroscopy (mass spectroscopy (TGA-MS) and Fourier transform infrared spectroscopy (TGA-FTIR)) and also differential scanning calorimetry (DSC) were employed to investigate the biomass thermal degradation. TGA and DSC results were obtained at temperature ranging from 25°C to 850°C and 500°C, respectively, using pure nitrogen as inert gas and at the heating rate of 15°C/min. TGA curves showed different stages for the biomasses thermochemical behavior associated with dehydration (stage 1), slow depolymerization (stage 2) and pyrolytic degradation (stage 3), while DSC indicated the caloric requirement in these stages. The main permanent evolved gases comprising H2, CO2, CO were detected online during analysis. The major permanent gases produced at the temperature range of 250–750°C were attributed to the biomasses pyrolysis, oxygenated functional groups cleavage and probably some secondary reactions. Furthermore, the bio-oils produced from the different biomasses pyrolysis, in a fixed-bed reactor, were analyzed by GC–MS and FTIR. The pyrolysis kinetics of different palm oil biomasses were investigated using the Coats-Redfern model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Thermal degradation of PMMA nanocomposites with functionalized nanoparticles as filler material is studied. Nanocomposites of PMMA with oleic acid (OA) functionalized LaF3: Nd3+ nanoparticles ...(OA-NPs, 2–3 nm) were prepared by solvent mixing and casting method. Minimal loss of optical transparency observed in nanocomposites was attributed to good dispersion of OA-NPs in PMMA matrix. Further thermogravimetric analysis (TGA) of PMMA, OA-PMMA and OA-NP/PMMA nanocomposites were carried out in nitrogen atmosphere and three degradation steps were observed. Evolved products during the thermal degradation of PMMA, OA-PMMA and NC-25 (nanocomposites with 25 wt% of OA-NPs) were analyzed by mass spectroscopy. Delayed evolution of radicals and MMA (methyl methacrylate) at third degradation step was observed in OA-PMMA film and NC-25. Differing to PMMA and OA-PMMA, evolved gas mass spectrum of NC-25 did not show presence of methoxy radicals and monomer at first and second step of degradation. The glass transition studies revealed the increase in glass transition temperature with nanoparticle concentration. This was attributed to the physical interaction of PMMA chains with OA-NPs and formation of interface region of low mobile PMMA chains around OA-NPs. Hence the improvement in the stability of OA-NP/PMMA was attributed to the formation of low mobile PMMA chains around nanoparticles.
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•Thermal degradation of PMMA nanocomposites having oleic acid functionalized LaF3: Nd3+ nanoparticles as filler is studied.•Nanocomposites were transparent and NIR luminescent.•The improvement in the thermal stability was attributed to the low mobile polymer interface region around nanoparticles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The presented derivative thermogravimetric and mass spectral data, obtained simultaneously for the pyrolysis of three different tyre rubbers, corroborate the assumption that the devolatilisation of a ...tyre rubber proceeds via two consecutive zones of weight loss and that these zones are characterised by different products and thus different reactions. The spectral data of the depolymerisation products moreover confirm that depolymerisation occurs exclusively (in case of polyisoprene rubber) or predominantly (in case of the polybutadiene rubbers) during primary devolatilisation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
"The pyrolysis of olive stones was investigated by thermogravimetric analysis-mass spectrometry in nitrogen atmosphere under non-isothermal conditions, at heating rates of 5, 10, 20, and 30 °C/min. ...According to gas evolution analysis, the thermal degradation of olive stones under inert atmosphere can be divided into four stages. There was only dehydration in the first stage (<200 °C). Most of gas products (CO2, CO, CH4, C2H6 and H2O) were evolved in the second stage in the temperature range 210-407 °C, simultaneously with main mass degradation. Only H2 was produced in the fourth stage at high temperatures (>550 °C). Thermogravimetric analysis results have been utilized to determine kinetic parameters by using a composite procedure involving the iso-conversional method (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose) and the master-plots method. The activation energy values estimated by the Ozawa-Flynn- Wall and the Kissinger-Akahira-Sunose methods are very close, with values of 229.20 kJ/mol and 232.55 kJ/mol, respectively. The master-plots method shows that the most probable reaction mechanism was described by an order n (On) model. The frequency factor was estimated to be A = 5.6x1021 min-1, the kinetic exponent was n = 6.2, and the reaction model function was f( ) = (1- )6.2."
Investigation of thermal degradation is essential for understanding flame retardancy mechanism and further tailoring of materials. In this work, polycarbonate was compounded with solid bisphenol A ...bis(diphenyl phosphate) (S-BDP) and organo-montmorillonite (OMMT) to form a nanocomposite with mainly intercalated and partially exfoliated morphology, and the main flame retardancy activity of the nanocomposite was shown to be in the condensed phase as revealed by cone calorimetry, thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TGA/FTIR) and thermogravimetric analysis coupled with mass spectrometry (TGA/MS). Although the main gaseous pyrolysis products of polycarbonate can't be greatly altered by S-BDP and OMMT, carbonate linkage would be stabilized and vigorous decomposition at higher temperature would be delayed, thereby char residue formation could be promoted. S-BDP also shows slight gaseous phase effect as proved by the detection of phosphorus–oxygen species in TGA/MS. Moreover, the relatively enhanced evolution of PO radicals in the sample filled with only S-BDP suggests that S-BDP alone exhibits a slightly stronger gaseous phase effect than the combination of S-BDP and OMMT. This enhanced condensed phase effect of S-BDP in the presence of OMMT could be associated with the delayed vigorous decomposition at higher temperature due to the barrier effect of OMMT. The peak heat release rate of polycarbonate could not be significantly reduced by substituting S-BDP with OMMT, yet it would prolong the time to peak heat release rate and reduce the smoke toxicity with a smaller release of carbon monoxide. The reduced carbon monoxide release was probably caused by further oxidation of carbon monoxide in the hotter char surface due to the barrier effect of OMMT.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
