Thermogravimetric Analysis Coupled With Mass Spectrometry Research Articles

Intrinsic reactivity analysis of soot removal in LNT-catalysts

The soot removal process in presence of a series of LNT-catalysts, and different reaction atmospheres, has been studied, using thermogravimetric analysis coupled to mass spectrometry (TG-MS) time-resolved experiments. Kinetic parameters have been estimated, using a distribution function of activation energy: where the frequency factor was correlated approximately with the activation energies which enable the decoupling of the processes involved in the regeneration by soot removal over those synthesized catalysts. It was found that soot removal is a sequential process that is strongly dependent on the formulation and surface structure of the catalyst and atmosphere of reaction. K-containing LNT catalysts showed a high activity in the soot removal process by gasification (Ea≈70–90kJmol−1), promoted by surface hydroxylated centers, decreasing the ignition temperature in oxygen atmosphere. NO+O2 atmosphere, more oxidizing than O2, provokes in addition a reduction in the soot removal temperature due to a direct reaction between soot and NO2 (gas) and/or the adsorbed NOx onto the catalyst surface.

Thermal Stability and Reactivity of Cathode Materials for Li-Ion Batteries.

The thermal stability of electrochemically delithiated Li0.1Ni0.8Co0.15Al0.05O2 (NCA), FePO4 (FP), Mn0.8Fe0.2PO4 (MFP), hydrothermally synthesized VOPO4, LiVOPO4, and electrochemically lithiated Li2VOPO4 is investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis, coupled with mass spectrometry (TGA-MS). The thermal stability of the delithiated materials is found to be in the order of NCA < VOPO4 < MFP < FP. Unlike the layered oxides and MFP, VOPO4 does not evolve O2 on heating. Thus, VOPO4 is less likely to cause a thermal run-away phenomenon in batteries at elevated temperature and so is inherently safer. The lithiated materials LiVOPO4, Li2VOPO4, and LiNi0.8Co0.15Al0.05O2 are found to be stable in the presence of electrolyte, but sealed-capsule high-pressure experiments show a phase transformation of VOPO4 → HVOPO4 → H2VOPO4 when VOPO4 reacts with electrolyte (1 M LiPF6 in EC/DMC = 1:1) between 200 and 300 °C. Using first-principles calculations, we confirm that the charged VOPO4 cathode is indeed predicted to be marginally less stable than FP but significantly more stable than NCA in the absence of electrolyte. An analysis of the reaction equilibria between VOPO4 and EC using a multicomponent phase diagram approach yields products and reaction enthalpies that are highly consistent with the experiment results.

Basic Insights into Tunable Graphene Hydrogenation.

The hydrogenation and deuteration of graphite with potassium intercalation compounds as starting materials were investigated in depth. Characterization of the reaction products (hydrogenated and deuterated graphene) was carried out by thermogravimetric analysis coupled with mass spectrometry (TG-MS) and statistical Raman spectroscopy (SRS) and microscopy (SRM). The results reveal that the choice of the hydrogen/deuterium source, the nature of the graphite (used as starting material), the potassium concentration in the intercalation compound, and the choice of the solvent have a great impact on the reaction outcome. Furthermore, it was possible to prove that both mono- and few-layer hydrogenated/deuterated graphene can be produced.

Surface activation of Pt nanoparticles synthesised by "hot injection" in the presence of oleylamine.

Oleylamine (OA) based “hot injection” colloidal synthesis offers a versatile approach to the synthesis of highly monodisperse metallic and multi-metallic alloyed nanostructures in the absence of potentially toxic and unstable phosphine compounds. For application in heterogeneous catalysis and electrocatalysis, the adsorbed OA species at the metal surfaces should be effectively removed without compromising the structure and composition of the nanostructures. Herein, we investigate the removal of OA from colloidal Pt nanoparticles through 1) “chemical methods” such as washing in acetic acid or ethanol, and ligand exchange with pyridine; and 2) thermal pre-treatment between 185 and 400 °C in air, H2 or Ar atmospheres. The electrochemical reactivity of Pt nanoparticles is acutely affected by the presence of surface organic impurities, making this material ideal for monitoring the effectiveness of OA removal. The results showed that thermal treatment in Ar at temperatures above 400 °C provides highly active particles, with reactivity comparable to the benchmark commercial catalyst, Pt/ETEK. The mechanism involved in thermal desorption of OA was also investigated by thermogravimetric analysis coupled to mass spectrometry (TGA-MS). Oxidation of HCOOH and adsorbed CO in acidic solution were used as test reactions to assess the Pt electrocatalytic activity.

Excellent Thermal Stability of VOPO4 As Cathode for Lithium-Ion Battery

Lithium ion batteries are widely used in portable electronic devices and electric vehicles. However, safety is one of the most important issues for the Li-ion batteries’ use. Some cathode materials, such as LiCoO2, are thermally unstable in the charged state. Upon decomposition these cathode materials release O2, which could react with organic electrolyte, leading to a thermal runaway. Thus, the safety of the Li-ion battery depends on the interaction between the cathode materials and the organic electrolyte. In this work, we have investigated three types of cathode materials: layered oxide LiNi0.8Co0.15Al0.05O2 (NCA); olivine phosphates LiFePO4, Mn-rich LiFe1-yMnyPO4 (LMFP); and multielectron vanadyl phosphates VOPO4, LiVOPO4 and Li2VOPO4. The thermal behavior of the materials with and without electrolyte (1M LiPF6 in EC: DMC=1:1) was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis coupled with mass spectroscopy (TGA-MS). The solid products of the thermal reactions were further studied by x-ray diffraction. The results indicate that electrolyte decomposes between 250 ºC and 300 ºC, releasing 391 J/g heat (Fig.1 a). NCA (charged to 4.6 V) starts to decompose at 220 ºC, generating large amounts of O2 and 674 J/g heat without the electrolyte. When NCA is heated with the electrolyte, the heat released is close to 800 J/g (Fig.1 b), which could result in a thermal runaway of the battery. LMFP charged to 4.4 V (MFP) partially decomposes below 350 ºC and gives off 476 J/g heat in the presence of the electrolyte (Fig.1 c). On the other hand, VOPO4 and its lithiated compounds (LiVOPO4, Li2VOPO4) have the best thermal stability: the heat generated by any of them without electrolyte is less than 100 J/g when heated up to 350 ºC. In the presence of the electrolyte, the heat released is also significantly less than that of NCA and MFP (Fig.1 d). We will also present evidence from the first principles phase diagrams that support the experimental conclusions, including predicted O2 evolution temperatures and resulting phase equilibria. This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583. Figure 1

Thermal Release of 3He from Tritium Aged LaNi4.25Al0.75 Hydride

Recently, the demand for He-3 has increased dramatically due to widespread use in nuclear nonproliferation, cryogenic, and medical applications. Essentially all of the world’s supply of He-3 is created by the radiolytic decay of tritium. The Savannah River Site Tritium Facilities (SRS-TF) utilizes LANA.75 in the tritium process to store hydrogen isotopes. The vast majority of He-3 “born” from tritium stored in LANA.75 is trapped in the hydride metal matrix. The SRS-TF has multiple LANA.75 tritium storage beds that have been retired from service with significant quantities of He-3 trapped in the metal. To support He-3 recovery, the Savannah River National Laboratory (SRNL) conducted thermogravimetric analysis coupled with mass spectrometry (TGA-MS) on a tritium aged LANA.75 sample. TGA-MS testing was performed in an argon environment. Prior to testing, the sample was isotopically exchanged with deuterium to reduce residual tritium and passivated with air to alleviate pyrophoric concerns associated with handling the material outside of an inert glovebox. Analyses indicated that gas release from this sample was bimodal, with peaks near 220 and 490°C. The first peak consisted of both He-3 and residual hydrogen isotopes, the second was primarily He-3. The bulk of the gas was released by 600 °C.

Value-added performance of processed cardboard and farm breeding compost by pyrolysis

This study aims to underline the huge potential in Canada of adding value to cardboard and compost as a renewable fuel with a low ecological footprint. The slow pyrolysis process of lined cardboard and compost blend was investigated. Thermal behavior was investigated by thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The thermal profiles are presented in the form of TGA/DTG curves. With a constant heating rate of 10°C/min, two parameters, temperature and time were varied. Cardboard decomposition occurred mostly between 203°C and 436°C, where 77% of the sample weight was decomposed. Compost blend decomposition occurred mostly between 209°C and 373°C, with 23% of weight. The principal gaseous products that evolved during the pyrolysis were H2O, CO and CO2. As a result, slow pyrolysis led to the formation of biochar. High yield of biochar from cardboard was found at 250°C for a duration of 60min (87.5%) while the biochar yield from the compost blend was maintained constant at about 31%. Finally, kinetic parameters and a statistical analysis for the pyrolysis process of the cardboard and compost samples have been investigated. Both materials showed a favorable thermochemical behavior. However, unlike cardboard, compost pyrolysis does not seem a promising process because of the low superior calorific and biochar values.

Reductive arylation of graphene: Insights into a reversible carbon allotrope functionalization reaction

The covalent functionalization of graphene represents a main topic in the growing field of nano materials. The reductive exfoliation of graphite with concomitant functionalization of the respective graphenide intermediates provides a promising approach towards functional graphene derivatives. In this article, we present new insights into the reductive arylation of graphene. Graphite intercalation compounds (GICs) with varying stoichiometries have been used as starting materials. Based on the spectroscopic data obtained by scanning Raman microscopy and thermogravimetric analysis coupled to mass spectrometry (TG/MS), a clear correlation between the amount of negative charges – present in the GIC – and the degree of functionalization in the final product could be found. Furthermore, the detailed analysis of the thermal defunctionalization process provided deeper insights into the covalent addend binding.

Characterization of lignocellulosic biomass thermal degradation and physiochemical structure: Effects of demineralization by diverse acid solutions

To eliminate the negative impacts of inorganic constituents during biomass thermochemical processes, leaching method by different diluted acid solutions was chosen. The different palm oil biomass samples (palm kernel shell (PKS), empty fruit bunches (EFB) and palm mesocarp fiber (PMF)) were pretreated by various diluted acid solutions (H2SO4, HClO4, HF, HNO3, HCl). Acids with the highest degrees of demineralization were selected to investigate the dematerialization impacts on the biomass thermal characteristics and physiochemical structure. Thermogravimetric analysis coupled with mass spectroscopy (TGA-MS) and Fourier transform infrared spectroscopy (TGA-FTIR) were employed to examine the biomass thermal degradation. TGA and DTG (Derivative thermogravimetry) indicated that the maximum degradation temperatures increased after acid pretreatment due to the minerals catalytic effects. 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 condensable vapors cracking and probably some secondary reactions. The physiochemical structure change of the acid-treated biomass samples was examined by using Brunauer Emmett Teller (BET) method, Scanning Electron Microscope (SEM) and FTIR. The pyrolysis kinetics of the different palm oil biomasses were investigated using first order reaction model.

Study of thermal pre-treatment on anaerobic digestion of slaughterhouse waste by TGA-MS and FTIR spectroscopy

Thermogravimetric analysis coupled to mass spectrometry (TGA-MS) and Fourier-transform infrared spectroscopy (FTIR) were used to describe the effect of pasteurization as a hygienic pre-treatment of animal by-products over biogas production. Piggery and poultry meat wastes were used as substrates for assessing the anaerobic digestion under batch conditions at mesophilic range. Poultry waste was characterized by high protein and carbohydrate content, while piggery waste presented a major fraction of fat and lower carbohydrate content. Results from anaerobic digestion tests showed a lower methane yield for the pre-treated poultry sample. TGA-MS and FTIR spectroscopy allowed the qualitative identification of recalcitrant nitrogen-containing compounds in the pre-treated poultry sample, produced by Maillard reactions. In the case of piggery waste, the recalcitrant compounds were not detected and its biodegradability test reported higher methane yield and production rates. TGA-MS and FTIR spectroscopy were demonstrated to be useful tools for explaining results obtained by anaerobic biodegradability test and in describing the presence of inhibitory problems.

Imidazolium Hydrogen Carbonates versus Imidazolium Carboxylates as Organic Precatalysts for N-Heterocyclic Carbene Catalyzed Reactions

Imidazolium-2-carboxylates (NHC-CO(2) adducts, 3) and (benz)imidazolium hydrogen carbonates ([NHC(H)][HCO(3)], 4) were independently employed as organic precatalysts for various molecular N-heterocyclic carbene (NHC) catalyzed reactions. NHC-CO(2) adducts were obtained by carboxylation in THF of related free NHCs (2), while the synthesis of [NHC(H)][HCO(3)] precursors was directly achieved by anion metathesis of imidazolium halides (1) using potassium hydrogen carbonate (KHCO(3)) in methanolic solution, without the need for the prior preparation of free carbenes. Thermogravimetric analysis (TGA) and TGA coupled with mass spectrometry (TGA-MS) of most [NHC(H)][HCO(3)] precursors 4 showed a degradation profile in stages, with either a concomitant or a stepwise release of H(2)O and CO(2), between 108 and 280 °C, depending on the nature of the azolium and substituents. In solution, NHC generation from both [NHC(H)][HCO(3)] salts and NHC-CO(2) adducts could be achieved at room temperature, most likely by a simple solvation effect. Both types of precursors proved efficient for organocatalyzed molecular reactions, including cyanosilylation, benzoin condensation, and transesterification reactions. The catalytic efficiencies of NHC-CO(2) adducts 3 were found to be approximately 3 times higher than those of their [NHC(H)][HCO(3)] counterparts 4.

Highly Luminescent and Temperature Stable Quantum Dot Thin Films Based on a ZnS Composite

A solution processable Zn(EtXn)2(octylamine) precursor has been used to deposit nanocrystalline ZnS thin films which can effectively host CdSe–CdS–ZnS quantum dots (QDs) with their native surface chemistry intact. The formation of such hybrid QD:ZnS composites proceeds through the initial decomposition of the octylamine stabilized zinc xanthate precursor to form nanocrystalline ZnS. To gain insight into this decomposition process we have utilized headspace gas chromatography–mass spectrometry (HS GC-MS), thermogravimetric analysis coupled with mass spectrometry (TGA-MS), grazing angle attenuated total reflectance Fourier transform infrared spectroscopy (GAATR FTIR), and grazing angle X-ray diffraction (GAXRD). Through these characterizations we identify that the major decomposition route of Zn(EtXn)2(octylamine) to form ZnS begins at 100 °C, generating predominantly CO2, COS, CS2, and ethanol as gaseous products. The octylamine used to solubilize the metal complex is found to remain adsorbed within the Zn...

Evaluation of N719 amount in TiO2 films for DSSC by thermogravimetric analysis

The aim of this work is to evaluate the amount of N719 dye in TiO2 films for DSSCs by thermogravimetric analysis coupled with mass spectrometry (TG-MS) in comparison with the traditional method based on the dye extraction in NaOH solutions. The characterization was carried out on TiO2 films applied on FTO glasses by automatic screen printing method. For all the samples, TG-MS showed three well defined steps. The first, below 100 °C and coupled to an endothermic signal was due to water release. From 200 to about 300 °C, there was the release of CO2 coming from decarboxylation reaction of N719. The last exothermic step was due to the combustion of organic residues. As the decarboxylation reaction occurs with release of 4 moles of CO2 per mole of N719, it was used to determine the dye loading of the samples that resulted in the range 7−15 wt% well agreeing the relevant content of dye obtained by desorption with NaOH.

Natural zeolite reactivity towards ozone: The role of compensating cations

Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1molL−1). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH3-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal.

Using TGA/FTIR TGA/MS and cone calorimetry to understand thermal degradation and flame retardancy mechanism of polycarbonate filled with solid bisphenol A bis(diphenyl phosphate) and montmorillonite

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.

Estimation of the storage life of dimethylol urea using non-isothermal accelerated testing

Abstract The mechanism and stability of dimethylol urea (DMU) to polycondensation were investigated using thermogravimetric analysis coupled with mass spectroscopy (TG-MS) for evolved gas analysis and a non-isothermal model-free induction period kinetic analysis using three temperature functions; the Arrhenius function and two non-Arrhenian functions. The polycondensation was observed to occur through a two-step process of condensation followed by elimination of formaldehyde during structural rearrangement as has been reported in the literature. The rate equations for each temperature function were evaluated and extrapolated to room (23 °C) and refrigerator (4 °C) temperature to estimate the length of the induction period for the onset of polycondensation for storage life prediction. Based on experience, estimates of the length of the induction periods and, hence, storage life, were most realistically predicted by the non-Arrhenian temperature functions.

A thermogravimetric analysis/mass spectroscopy study of the thermal and chemical stability of carbon in the Pt/C catalytic system

Vulcan XC72 carbon powder and Pt/Vulcan XC72 catalytic powder were characterized by transmission electron microscopy (TEM) and their reactivity under controlled atmospheres was studied as a function of the temperature. Under air atmosphere, production of water was detected by thermogravimetric analysis coupled with mass spectroscopy (TGA-MS) measurement at m/z 18, which evidenced that hydrogenated surface functions were present on the carbon substrate. Under argon atmosphere, the comparison of TGA-MS measurements performed at m/z 18 and m/z 44 with TEM and XRD results, together with XPS measurements, indicated that platinum surface oxides are rather Pt(OH)2 than PtO or PtO2 species. Such reactive surface species is involved in the degradation mechanism of carbon support under air and inert atmospheres. Under H2(3%)/Ar atmosphere, hydrocarbon production coming from “reforming” reactions of the carbon support started at very low temperatures (below 373K). TEM images of the same catalytic powder region before and after thermal treatment at 423K under reducing atmosphere clearly displayed consumption of the carbon substrate. The reaction products may not only affect the intrinsic properties of the support but also the catalytic properties of platinum particles: reaction products could poison the anodic catalyst.

Polyacrylonitrile‐Derived 1D Carbon Structures via Template Wetting and Electrospinning

AbstractIn‐situ polymerisation of acrylonitrile as well as a DMF solution‐phase impregnation of polyacrylonitrile, PAN, in porous aluminium oxide templates (PAOX) to synthesise 2D arranged carbon nanotubes with diameters in the range of 40–200 nm were studied. The preparation of graphitised carbon tubes from polyacrylonitrile consists of two steps, first a low‐temperature crosslinking of aromatic ring units at 250 °C, which is followed by a stepwise high‐temperature pyrolysis (carbonisation) in an inert atmosphere in the temperature range between 600–1100 °C. Finally, a graphitisation step was carried out at high temperature above 1500 °C, which however leads to a complete collapse of the structure due to a solid‐state reaction between the template and the PAN infiltrated in the template pores. X‐ray diffraction of the carbonised PAN tubes in PAOX indicates no graphitisation up to curing temperatures of 750 °C. The process of PAN loading and subsequent polymerisation by thermal curing within PAOX was followed by IR and UV/Vis spectroscopy, thermogravimetric analysis coupled with mass spectrometry (TGA/MS), XPS spectroscopy as well as combustion analysis. The presence of nitrogen in the final carbonised product was determined.

Ligand effects on the size and purity of Pd nanoparticles

Abstract Palladium nanoparticles (Pd-NPs) were prepared by a single-phase reduction of palladium acetate in the presence of different organic thiol ligands. Sizes, size distributions and crystallinity of the Pd-NPs were determined by high resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (XRD) while thermogravimetric analysis coupled with mass spectroscopy (TGA-MS) was employed to measure their organic ligand to palladium ratios and to quantify contaminants. No systematic effect of the different ligands on the size and purity of the Pd-NPs was observed but 1st-generation Frechet dendron thiols had an about 4 times larger foot-print at the surface of the NPs than the other thiol ligands.

High-temperature thermal destruction of poultry derived wastes for energy recovery in Australia

The high-temperature thermal destruction of poultry derived wastes (e.g., manure and bedding) for energy recovery is viable in Australia when considering resource availability and equivalent commercial-scale experience in the UK. In this work, we identified and examined the opportunities and risks associated with common thermal destruction techniques, including: volume of waste, costs, technological risks and environmental impacts. Typical poultry waste streams were characterised based on compositional analysis, thermodynamic equilibrium modelling and non-isothermal thermogravimetric analysis coupled with mass spectrometry (TG-MS). Poultry waste is highly variable but otherwise comparable with other biomass fuels. The major technical and operating challenges are associated with this variability in terms of: moisture content, presence of inorganic species and type of litter. This variability is subject to a range of parameters including: type and age of bird, and geographical and seasonal inconsistencies. There are environmental and health considerations associated with combustion and gasification due to the formation of: NO(X), SO(X), H(2)S and HCl gas. Mitigation of these emissions is achievable through correct plant design and operation, however, with significant economic penalty. Based on our analysis and literature data, we present cost estimates for generic poultry-waste-fired power plants with throughputs of 2 and 8 tonnes/h.