TGA-MS Analysis Research Articles

Pyrolysis Valorization of Vegetable Wastes: Thermal, Kinetic, Thermodynamics, and Pyrogas Analyses

In comparison to other methods, valorising food waste through pyrolysis appears to be the most promising because it is environmentally friendly, fast, and has a low infrastructure footprint. On the other hand, understanding the pyrolytic kinetic behaviour of feedstocks is critical to the design of pyrolysers. As a result, the pyrolytic degradation of some common kitchen vegetable waste, such as tomato, cucumber, carrot, and their blend, has been investigated in this study using a thermogravimetric analyser. The most prevalent model fitting method, Coats–Redfern, was used for the kinetic analysis, and the various mechanisms have been investigated. Some high-quality fitting mechanisms were identified and used to estimate the thermodynamic properties. As the generation of pyrolysis gases for chemical/energy production is important to the overall process applicability, TGA-coupled mass spectrometry was used to analyse the pyrogas for individual and blend samples. By comparing the devolatilization properties of the blend with single feedstocks, the presence of chemical interactions/synergistic effects between the vegetable samples in the blend was validated. The model, based on a first-order reaction mechanism, was found to be the best-fitting model for predicting the pyrolysis kinetics. The calculated thermodynamic properties (ΔH (enthalpy change ≈ E (activation energy))) demonstrated that pyrolysis of the chosen feedstocks is technically feasible. According to the TGA–MS analysis, blending had a considerable impact on the pyrogas, resulting in CO2 composition reductions of 17.10%, 9.11%, and 16.79%, respectively, in the cases of tomato, cucumber, and carrot. Overall, this study demonstrates the viability of the pyrolysis of kitchen vegetable waste as a waste management alternative, as well as an effective and sustainable source of pyrogas.

Pyrolysis of Rapeseed Oil Press Cake and Steam Gasification of Solid Residues

A deoiled rapeseed press cake (RPC) was pyrolyzed by heating at a slow heating rate to 1000 °C in a fixed bed reactor, and the produced char was then gasified to obtain data for the kinetic modeling of the process. The gasification experiments were performed in a thermogravimetric analyzer (TGA) under steam/argon mixtures at different temperatures (750, 800 and 850 °C) and steam mole fractions (0.17 and 0.45). The three most commonly used gas-solid kinetic models, the random pore model, the volumetric model and the shrinking core model were used to describe the conversion of char during steam gasification. The objective of the kinetic study was to determine the kinetic parameters and to assess the ability of the models to predict the RPC conversion during steam gasification. A TGA-MS analysis was applied to assess the composition of the product gas. The main steam gasification product of the RPC was hydrogen (approximately 60 mol % of the total product). The volumetric model was able to accurately predict the behavior of the RPC char gasification with steam at temperatures of 750–850 °C and steam concentrations less than 0.45 mole fraction. The activation energy and the reaction order with respect to steam were equal to 166 kJ/mol and 0.5, respectively, and were typical values for the gasification of biomass chars with steam

Photosensitive Organic-Inorganic Hybrid Materials for Room Temperature Gas Sensor Applications.

In this work, the hybrids based on nanocrystalline SnO2 or In2O3 semiconductor matrixes and heterocyclic Ru(II) complex are studied as materials for gas sensors operating at room temperature under photoactivation with visible light. Nanocrystalline semiconductor oxides are obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heterocyclic Ru(II) complex is synthesized for the first time and investigated by 1H NMR, 13C NMR APT, MALDI-MS analysis, and UV-Vis spectroscopy. The HOMO and LUMO energies of the Ru(II) complex are calculated from cyclic voltammetry data. The hybrid materials are characterized by TGA-MS analysis and EDX mapping. The optical properties of hybrids are studied by UV-Vis spectroscopy in the diffuse reflection mode. The investigation of spectral dependencies of photoconductivity of hybrid samples demonstrates that the role of organic dye consists in shifting the photosensitivity range towards longer wavelengths. Sensor measurements demonstrate that hybrid materials are able to detect NO2 in the concentration range of 0.25–2 ppm without the use of thermal heating under periodic illumination with even low-energy long-wavelength (red) light.

Development of Highly Conductive and Highly Durable All-Aromatic Anion Exchange Membranes By Using Thermally Convertible Precursor Polymer

Solid Alkaline Fuel Cells (SAFCs) using Anion Exchange Membranes (AEMs) attracts increasing attention for next-generation fuel cell technology. SAFCs have many advantages over proton exchange membrane fuel cell such as variable choice of metal electrode catalyst and fuels. However, the commercialization of SAFCs is limited due to the lack of high-performance AEMs. Commonly, AEMs have low ionic conductivity and poor durability in alkaline medium. In this study, we developed a novel AEM comprises of wholly aromatic, anthracene-based, backbone as a chemically durable membrane. Commonly, such kind of polymers exhibits very low solubility in common organic solvent due toπ-πstacking. Thus the processability into a membrane is very difficult. Our unique molecular design is employing bulky Thermal Leaving Group (TLG) on the precursor polymer allowing this polymer to be cast as a film due to high solubility (>300 mg/ml). Then, TLG on the membrane film was removed by performing retro Diels-Alder reaction1,2 in the solid state to obtain a wholly aromatic membrane (figure 1 (a)). The precursor polymer was obtained by Suzuki-Miyaura coupling of the monomers. The methyl group of the resulting polymer was converted to benzyl bromide and finally to quaternary trimethylammonium bromide to afford the target precursor polymer (TPP). The polymer structure and molecular weight were analyzed by 1H-NMR and GPC. Ion exchange capacity (IEC) was determined by titration. The in-plane ionic conductivity of the membrane is evaluated by AC impedance method. Stability test in hot alkaline solution and Fenton solution was performed to check the chemical durability of the membrane. Molecular weight and IEC of synthesized TPP are 13,000 g/mol and IEC 2.49, respectively. Target polymer (TP) membrane was then obtained by just heating TPP membrane and removing TLG. The best heating temperature was determined to be 180 oC by TGA-MS analysis. IEC of the membrane has increased to 3.16 after thermal conversion. Despite higher IEC value, water uptake of TP membrane was lower than TPP membrane probably due to the strong intermolecular interaction of TP membrane. Therefore, TP membrane keeps higher IEC even after water uptake and this may result in high anion conductivity. Figure 1 (b) shows the ionic conductivity of TP membrane before and after the durability test. The membrane kept initial HCO3 - conductivity even after exposed to a very harsh alkaline solution (8M NaOH for 21 days at 80 oC) and Fenton solution (H2O2 3 wt%, FeSO4 3 ppm at 60 oC for 8 hours). This is a solid proof that the TP membrane has both high durability and high conductivity, meeting for SAFC application. These findings suggest that the use of TLG on polymer backbone allow development of new design concepts for highly-durable and highly conductive AEMs.

Dolomite effect on steam co-gasification of olive pomace, coal and petcoke: TGA-MS analysis, reactivity and synergistic effect

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.

Effects of using two transition metals in the synthesis of non-noble electrocatalysts for oxygen reduction reaction in direct methanol fuel cell

Five different bimetallic non-precius metal catalysts for oxygen reduction reaction (ORR) are synthesized by different combinations of two transition metal (Fe, Co, Cu, Zn) phthalocyanine precusrsors. The aim of this study is to investigate the effects of the different combinations of two transition metals on the physico-chemical and ORR electrocatalytic activity of the catalysts. The precursors were mixed, impregnated on a mesoporous silica used as a hard template, and pyrolyzed under inert atmosphere at 800 °C. After the template removal, the catalysts were characterized via BET, FESEM, and XPS. TGA-MS analysis was also performed on the catalysts precursors to simulate their behaviour during the pyrolysis, detecting the evolved gases. The results show that both the physico-chemical features and the ORR activity and selectivity in acidic medium (measured by RDE-RRDE technique) are strongly influenced by the transition metals pair used. In particular, the most effective transition metals pair to get a more performing ORR catalyst is Co-Zn. The catalysts are also tested in direct methanol fuel cell, including a short-term durability test. The durability of the best perfroming Co-Zn catalyst is improved compared to a similar catalyst synthesized using Fe. The possibility of tuning the catalysts features by combining different transition metals enables to increase the catalyst durability, the production yield during the synthesis (enabling to recover more material after the pyrolysis), and the surface N fixation.

Quinone-formaldehyde polymer as an active material in Li-ion batteries

A benzoquinone polymer is synthesized by the polymerisation of hydrobenzoquinone and formaldehyde, followed by oxidation process using a hydrogen peroxide to convert hydroquinone to quinone. As prepared materials are characterized with FTIR, 1H-13C CPMAS NMR, pyrolysis coupled with gas chromatography (GC) and mass spectrometer (MS), TGA-MS analysis, EDX, elemental analysis, XRD, SEM and TEM microscopies and BET nitrogen adsorption. The benzoquinone polymer shows an excellent electrochemical performance when used as a positive electrode material in Li-ion secondary batteries. Using an electrolyte consisting 1 M bis(trifluoromethane)-sulfonimide lithium salt dissolved in 1,3-dioxolane and dimethoxyethane in a vol. ratio 1:1 (1 M LiTFSI/DOL + DME = 1:1) a stable capacity close to 150 mAh/g can be obtained. Compared to other electroactive materials based on benzoquinones it has a supreme capacity stability and is prepared by a simple synthesis using easily accessible starting materials. Further improvements in the capacity value (up to the theoretical value of 406 mAh/g) can be foreseen by achieving a higher degree of oxidation and by modification of polymerization process to enhance the electronic and ionic conductivity.

A Case Study: Li/S Battery Characterization in Argonne National Laboratories Post-Test Facility and Center for Nanoscale Materials

Lithium ion batteries are an important energy source with wide scale applications due to their high energy and power densities. As the application of Li-ion batteries has advanced to their use in electric vehicles and grid energy storage, the demand for increased performance has led to research into higher capacity anodes and cathodes. Recent effort has focused on the development of Li2S cathodes because of the low cost and high theoretical capacity (1675 mAh/g) of sulfur. One of the advantages of a Li2S cathode is the ability to pair with safer anode materials rather than Li metal, however, a major limitation to practical application is the formation of soluble lithium polysulfides which leads to rapid capacity fade and high self-discharge. In order to circumvent these problems, attempts at encapsulating Li2S particles with conductive carbon have been made with some success. In this study, to understand the effect of the carbon shell, a Li/S battery consisting of a Li2S cathode with particles encapsulated with nitrogen-doped carbon, and a Li-metal anode was characterized at Argonne’s battery Post-Test Facility and the Center for Nanoscale Materials. The coated particles were prepared by ball milling carbon black with Li2S particles followed by stirring with pyrrole and subsequent carbonization in an autoclave. Cells made with the coated Li2S particles exhibited higher capacity with prolonged cycling than uncoated cells. The improved performance is attributed to the presence of the N-doped carbon coating on the Li2S particles. The cycled cells were subsequently opened in the Post-Test Facility glovebox. The anode and cathode were analyzed using HPLC, optical microscopy, and SEM/EDS. TEM and EFTEM of the Li2S particles was performed at the Center for Nanoscale Materials using a special air-tight sample holder. The sample was placed in the holder that was in an Ar-filled glovebox and then transferred into the TEM. Argonne’s unique Post-test Facility has two large connected argon-filled glove boxes with water and oxygen concentrations held below 1 ppm. One glove box is used for the dismantling of cells, both large and small, and the subsequent sample preparation for analysis. Samples are transferred to the second customized glove box (via an air-lock) for XPS, Raman, FTIR and TGA-MS analysis. Samples for HPLC-MS, GCMS, SEM and optical microscopy are removed from the glove box in containment and analyzed in appropriately modified instrumentation. Argonne’s Center for Nanoscale Materials user facility was used for EFTEM imaging, using an air-tight sample holder and Raman with multiple laser sources. Through these facilities we were able to systematically characterize cells at a multi-scale level. This work was performed under the auspices of the DOE Office of Vehicle Technologies, Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. * Argonne National Laboratory, Argonne, IL ** Illinois Institute of Technology, Chicago, IL

Formation and Decomposition of CO2 Intercalated Graphene Oxide

The formation, stability, and decomposition of CO2 intercalated graphene oxide was analyzed by FTIR, TGA-MS, TGA-IR, AFM, and SEM for the first time. We found that the formation starts at 50 °C and develops up to 120 °C. The formation process can be best observed by FTIR spectroscopy, and the product is stable at ambient conditions. At higher temperatures, the decomposition of CO2 intercalated graphene oxide occurs due to the release of water, CO2, and CO that can be monitored by TGA-MS and TGA-IR analysis. AFM and SEM images can visualize the formation of blisters in GO films that become instable at 210 °C. We further prepared graphene oxide with a low water-content and found that the formation of CO2 was significantly suppressed and CO became the major species responsible for the weight loss. In addition we prepared 18OH2 treated graphene oxide to elucidate the formation process of CO2 and found C16O18O by TGA-MS analysis that proves the crucial role of water during CO2 formation. From these experiments we propose that hydrate species are key-intermediates for the formation of CO2. Hence, it seems likely that rearrangement reactions that can proceed via hydrate intermediates, known from organic chemistry, are probably responsible for the formation of carboxylic acids at the edges of graphene oxide sheets after sonication of graphite oxide. Further, our investigations prove that graphene oxide is less stable than shown by TGA measurements. This has a high impact on the electronic properties of reduced graphene oxide, especially for all those using it for electronic applications.

New Organic–Inorganic Hybrids with Azo-dye Content

Five new organic–inorganic hybrids were generated from their corresponding co-polymer structures using thermal cross-linking process. The hybrid structures contain covalently-linked azobenzene units provided by the previous co-polymerization step between 3-methacryloxypropyl trimethoxy-silane and five novel azo-monomers. All structures have been characterized by FT-IR spectroscopy and TGA-MS analysis. The soluble co-polymers have also been characterized by SEC, elemental analysis and 1H-NMR spectroscopy. It has been found that the thermal stability of the hybrid structures was enhanced, as compared to the soluble co-polymers, due to the newly generated Si–O–Si bonds. The newly prepared structures show a high content in chromophore units, as indicated by 1H-NMR spectra and elemental analyses.

Covalent sidewall functionalization of single wall carbon nanotubes.

Alkyllithium reagents may be used to attach alkyl groups to the sidewalls of fluoro nanotubes. Thermal gravimetric analysis combined with UV-vis-Nir spectroscopy has been used to provide a quantitative measure of the degree of functionalization. SWNTs prepared using the HiPco process exhibit a higher degree of alkylation than SWNTs from the laser-oven method, indicating that the smaller diameter fluoro tubes are alkylated more readily. The spectral signature of the pristine SWNTs can be regenerated when the alkylated SWNTs are heated in Ar at 500 degrees C, demonstrating that dealkylation occurs at this temperature. TGA-MS analysis using a sample of n-butylated h-SWNTs showed that 1-butene and n-butane are formed during thermolysis.