TG-MS Analysis Research Articles

Torrefaction of Straw from Oats and Maize for Use as a Fuel and Additive to Organic Fertilizers—TGA Analysis, Kinetics as Products for Agricultural Purposes

This publication presents research work which contains the optimum parameters of the agri-biomass: maize and oat straws torrefaction process. Parameters which are the most important for the torrefaction process and its products are temperature and residence time. Thermogravimetric analysis was performed as well as the torrefaction process using an electrical furnace on a laboratory scale at a temperature between 250–525 °C. These biomass torrefaction process parameters—residence time and temperature—were necessary to perform the design and construction of semi-pilot scale biomass torrefaction installations with a regimental dryer and a woody and agri-biomass regimental torrefaction reactor to perform a continuous torrefaction process using superheated steam. In the design installation the authors also focused on biochar, a bi-product of biofuel which will be used as an additive for natural bio-fertilizers. Kinetic analysis of torrefaction process using maize and oat straws was performed using NETZSCH Neo Kinetics software. It was found that kinetic analysis methods conducted with multiple heating rate experiments were much more efficient than the use of a single heating rate. The best representations of the experimental data for the straw from maize straw were found for the n-order reaction model. A thermogravimetric analysis, TG-MS analysis and VOC analysis combined with electrical furnace installation were performed on the maize and oat straw torrefaction process. The new approach in the work presented is different from that of current scientific achievements due to the fact that until now researchers have worked on performing processes on oat and maize straws by means of the torrefaction process for the production of a biochar as an additive for natural bio-fertilizers. None of them looked for economically reasonable mass loss ratios. In this work the authors made the assumption that a mass loss in the area of 45–50% is the most reasonable loss for the two mentioned agri-biomass processes. On this basis, a semi-pilot installation could be produced in a further BIOCARBON project step. The kinetic parameters which were calculated will be used to estimate the size of the apparatuses, the biomass dryer, and biomass torrefaction reactor.

Coal gasification using chemical looping with varied metal oxides as oxygen carriers

Coal gasification using chemical looping (CGCL) has been suggested as an innovative coal gasification technology for producing high quality synthesis gas with lattice oxygen from oxygen carrier instead of molecular oxygen. In this work, highly active nanoparticles (NPs) based on the transition metals Mn, Co Fe and Ni were prepared and used as oxygen carriers (OCs) to promote carbon conversion. Furthermore, the reaction mechanism between OCs and coal was investigated to guide the design of OCs and the fuel reactor. It was found that the presences of OCs evidently facilitated to coal gasification and enhanced total carbon conversion. Of the four investigated OCs, Mn@meso-SiO2 presented high reactivity with coal and high selectivity for synthesis gas during coal-OC steam gasification, which made it attractive for the CGCL process. TG-MS analysis indicated that direct solid-solid contact reaction between coal and OCs could not be negligible in the CGCL process. Furthermore, no significant changes in material phases were found by comparing with the main phases of the OCs after cycling and the raw samples before test. Combined with the SEM images of the OCs samples, it can be conclude that the used OCs showed a good heat-resistant property.

The Physico-Chemical Characterization of Mesoporous Sulfated Zirconia Nanoparticles Prepared under Structure-Directing-Free for <i>n</i>-Hexane Isomerization

This article describes the physico-chemical characterization of the sulfated zirconia catalysts prepared from zirconyl chloride, acetic acid and ammonium persulfate system under structure-directing-free and calcined at 650°C. The catalysts were characterized via an array of characterization techniques such as surface acidity and texture measurements, X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), thermogravimetric measurement (TG) coupled with a quadrupole mass spectrometer (MS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and/or mass spectrometry (ICP-MS). It is clear from TG-MS, ICP-AES, and IR analyses that the precursor of the catalyst is a sulphur species-doped zirconium oxy-hydroxyl acetate complex. The presence of zirconium-bound sulfate groups results in the superacidity of the catalyst and hence high activity in n-hexane isomerization. It is shown from nitrogen adsorption and desorption, FESEM, and HRTEM measurements that the materials exhibit mesoporous and nanocrystalline structure.

The pyrolysis of vitrinite and inertinite by a combination of quantum chemistry calculation and thermogravimetry-mass spectrometry

In this study, pyrolysis behaviour of vitrinite and inertinite from Heidaigou long-flame coal was studied via quantum chemical calculation and TG-MS. Quantum chemical calculation showed that vitrinite contains bonds with long bond length and small bond order, whereas inertinite revealed the opposite. And vitrinite and inertinite presented the same order of breaking bonds, but the numbers of breaking bonds showed differences. Before CO2 release, bond breakages and initial breakdown of macromolecular structure were observed. TG-MS analysis showed that the emissions with the same number of carbon, whether from vitrinite pyrolysis or inertinite pyrolysis, showed the same variation trend. Emissions from both vitrinite and inertinite can be divided into following four types. The first includes CO2, which was detected at 300 °C. The second consists of C1, C2, C3 and C4 compounds, which were observed at 420 °C and showed a fast release rate. The third comprises C6 and C7 compounds and CO, which were also detected at 420 °C with a slow release rate, and the fourth includes H2, which was identified at 500 °C. The escapes of the same substances during pyrolysis of vitrinite and inertinite were compared. Almost all emissions from vitrinite were higher than those from inertinite, but the temperature of maximum CO2 release from vitrinite was lower than that of inertinite.

Sulfur fixation and reduction roasting of stibnite for clean extraction of antimony by a combined metallurgy and beneficiation process

The direct sulfur fixation and reduction roasting of antimony sulfide (Sb2S3) were investigated for antimony extraction, based on the combination of metallurgy and beneficiation. Zinc oxide (ZnO) and carbon, used as the sulfur-fixing agent and reductant, respectively, were roasted with Sb2S3 to form Sb metal and zinc sulfide (ZnS). The products were separated by gravity separation and flotation. The predominance-area diagrams of Sb-Zn-S-O indicated that Sb2S3 could be transformed into Sb directly. The equilibrium composition simulation indicated that sulfur was completely fixed in the form of ZnS. The in-situ X-ray diffraction and TG–MS analysis of the Sb2S3-ZnO-C system indicated that the roasting process was initially conducted as a sulfur-fixing reaction to generate antimony oxide (Sb2O3) and ZnS; thereafter, the Sb2O3 was reduced to metallic antimony. The optimum conditions for Sb2S3 conversion were determined as follows: temperature of 800 °C, carbon particles of 150–200 mesh, WZnO/Wtheory = 1.0 (where W represents weight), and a time period of 2 h, where the Sb generation and sulfur-fixing rate reached 90.44% and 94.86%, respectively. The gravity and flotation separation method generated the recovery rates of 87.32% and 92.04% for Sb and ZnS, respectively. Compared with the current process, this new method will significantly facilitate the reduction of energy cost and SO2 emissions.

Towards a surface functionalisation and grafting of a polycarbosilane onto zirconium carbide particles for the development of hybrid core-shell structures

In order to achieve future ZrC/SiC core-shell structures, hybrid ZrC-polycarbosilane materials were synthesised. To fabricate these organic coated non-oxide ceramics, the surface was first functionalised with allylchlorodimethylsilane (ACDMS) in a simple procedure. The organic covalent grafting of the carbosilane onto zirconium carbide particles was confirmed by XPS, TEM and TG-MS analyses. The effect of the temperature and of the organosilicon molecule concentration has also been investigated to check their role on the functionalisation efficiency of zirconium carbide surfaces. The modified surfaces with allyl groups were then subjected to a hydrosilylation reaction to graft a polycarbosilane. XPS, together with TG-MS and TEM images confirmed the presence of an organic coating with a thickness up to 30 nm, indicating the presence of core (ZrC)/shell (polycarbosilane) structures.

Synthesis and Properties of Branched Hydrogenated Nonasilanes and Decasilanes.

Branched higher silicon hydrides Si nH2 n+2 with n > 6 were recently found to be excellent precursors for the liquid phase deposition of silicon films. Herein we report the gram-scale synthesis of the novel nona- and decasilanes (H3Si)3Si(SiH2) nSi(SiH3)3 (2: n = 1, 5: n = 2) from (H3Si)3SiLi and Cl(SiPh2) nCl by a combined salt elimination/dephenylation/hydrogenation approach. Structure elucidation of the target molecules was performed by NMR spectroscopy and X-ray crystallography. 2 and 5 are nonpyrophoric and exhibit a bathochromically shifted UV absorption compared to neopentasilane and the structurally related octasilane (H3Si)3SiSi(SiH3)3. TG-MS analysis elucidated increased decomposition temperatures and decreased ceramic yields for branched hydrosilanes relative to cyclopentasilane. Otherwise, very similar thermal properties were observed for hydrosilane oligomers with linear and branched structures.

Sintering densification behaviors of Ti-1Al-8V-5Fe alloy based on TiH2 and TiH1.5 powders

ABSTRACTThe sintering densification behaviors of Ti-1Al-8V-5Fe alloys by saturated titanium hydride (TiH2) and unsaturated titanium hydride (TiH1.5) powders are investigated. The results show that the TiH2-185 specimens present better sintering densification ability compared with TiH1.5–185 specimens, which displays that the titanium hydride with more hydrogen has a stronger densification ability. The TG-MS analysis suggests that the decompositions of TiH2 and TiH1.5 powders are accompanied by the H2O releasing, and the TiH2 releases more H2O than that of TiH1.5. The twice phase transformations can be observed in the TiH2-185 specimens by DSC, which contribute to the H2O releasing and dislocations and vacancies. Thus, TiH2 powder is helpful to obtain higher sintering densification and better mechanical properties for Ti-1Al-8V-5Fe alloy.

Facile preparation of Cr2O3 nanoparticles and their use as an active catalyst on the thermal decomposition of ammonium perchlorate

ABSTRACTCr2O3 nanoparticles were prepared by repeated wet mechanical milling technique. Three drying methods, oven drying, vacuum drying, and vacuum freeze-drying were comparatively used to dry Cr2O3 nanoparticles. These processes can be easily scaled up to 10-kg quantities. It took only 2–3 h to cut bulk size to nanometer by milling. The obtained Cr2O3 nanoparticles are semi-spherical and homogeneous with an average size of 30 nm measured by SEM and TEM and show similar diffraction peak positions to bulk one investigated by XRD. The TG/DSC study indicated that, compared with bulk Cr2O3, Cr2O3 nanoparticles obtained by oven drying and vacuum drying, the catalytic performance of Cr2O3 nanoparticles obtained by vacuum freeze-drying is the best in lowering the peak temperature of high temperature decomposition and the activation energy, while increasing the apparent decomposition heat and the reaction rate constant of ammonium perchlorate (AP) due to their good dispersion and large specific surface area. The possible catalytic mechanism of Cr2O3 on the thermal decomposition of AP was proposed by TG-MS analysis. These findings showed that wet mechanical milling technique combined with vacuum freeze-drying technology is suitable for efficient preparation of Cr2O3 nanoparticles, which could be a promising additive for accelerating the thermal decomposition of AP.

Effect of the oxygen content and the functionality of spinnable pitches derived from ethylene tar by distillation on the mechanical properties of carbon fibers

Three basic pitches were prepared by the distillation of ethylene tar at 200, 250, or 300 °C for 3 h. Spinnable pitches were produced from them using air-blowing followed by heat treatment at 330°C for 4 h and are designated P200AT, P250AT and P300AT, respectively. These three pitches, and stabilized fibers and carbon fibers produced from them were characterized by TG-MS, FT-IR, 13C-NMR, XRD, SEM, solubility tests and elemental analysis. The components and oxidation reactivity of the basic pitches, and its influence on the oxygen functionality and microstructures of the spinnable pitches and mechanical properties of the resulting carbon fibers were investigated. Results showed that with increasing distillation temperature the aliphatic carbon content and n-hexane and toluene solubility of the basic pitches decreased, while their aromaticity and planarity increased, and the oxidation reactivity reached a maximum at 250 °C. Of the three spinnable pitches P250AT had the highest softening point, highest carbon yield, oxygen content, and C=O content and the highest toluene insoluble fraction. However, the oxygen uptake of P250AT pitch fibers during stabilization was the lowest among the three. This led to a reduction of gas release during carbonization, and therefore the highest carbon yield, the smallest number of defects, the highest tensile strength and the lowest Young's modulus of all the carbon fibers.

Experimental Study on Gas Evolution Process of Binders in Foundry Industry based on TG-MS

The gas evolution performance of the mold is a very important index, which is directly related to the quality of casting. As the gas generation of sand is much smaller than that of binder, the gas evolution process of binders plays a decisive role in the formation of defects such as pores during casting. Therefore, it is of great significance to study the gas evolution process of binders in foundry. In this study, TG-MS analysis will be introduced into the study of the gas evolution process of binders in foundry. Three kinds of resins in foundry and one kind of sodium silicate will be selected, and the binders will be tested by TG-MS after being hardened to find and analyze the types and temperatures of gassing in the heating process. This study helps to find out the regular pattern of gas evolution process of binders in foundry and to provide theoretical and practical guidance for the study of casting defects such as pores.

High-performance LiVPO4F/C cathode constructed by using polyvinylidene fluoride as carbon source and the influencing mechanism for lithium ion batteries

New cathode LiVPO4F/C with high-performance was synthesized by using polyvinylidene fluoride (PVDF) as carbon source although there is no benzene ring in it. Compared with other carbon sources, the plateau, rate and cyclic performance of LiVPO4F/C are greatly enhanced when PVDF is used. The specific capacity of LiVPO4F/C containing 8 wt% carbon at 0.1 C, 1 C and 5 C are 148.1 mAh·g−1, 144.9 mAh·g−1 and 135.8 mAh·g−1, which is nearly the best reported results. Moreover, the TG-MS analysis is used to detect the gases released by different carbon sources in the sintering process. It shows that the Li3V2(PO4)3/C impurity is greatly inhibited. This is because that HF gas released by PVDF can prevent the volatilization of fluorine and compensate the losses of fluorine. By contrast, the hydrogen free radicals released by other carbon sources can combine with fluorine and accelerate the volatilization of fluorine, resulting in the increasing of Li3V2(PO4)3/C impurity. Then, the performance of LiVPO4F/C cathode containing more Li3V2(PO4)3/C is greatly deteriorated.

A comparative study on pyrolysis reactivity and gas release characteristics of biomass and coal using TG-MS analysis

ABSTRACTPyrolysis reactivity and gas release characteristics of biomass and coals were comparatively investigated using TG-MS. In addition, chemical compositions and structures of tested samples were determined to correlate pyrolysis gas release characteristic. It was found that pyrolysis reactivity and gaseous product release were hardly varied with pyrolysis heating rate. Furthermore, pyrolysis rates of two biomass samples were greater than those of coals, which were mainly attributed to the chemical compositions and the gaseous product evolution process. The result also showed that gaseous product release during pyrolysis process was related to the presence of different functional groups in samples.

Functionalization of hexagonal boron nitride nanosheets and their copolymerized solid glasses

Hexagonal boron nitride nanosheets (h-BNNSs) with unique properties, including wide band gap, excellent thermal conductivity and thermal stability, are among the most promising 2D inorganic nanomaterials in recent years. Functionalization of h-BNNSs is necessary to prevent them from strong tendency to agglomeration and to improve their dispersity and interfacial properties in solvents and polymer composites. In this work, amino and silane functionalized h-BNNSs were obtained, respectively. The chemical-bonding amino and silane functionalization of h-BNNSs were verified by FTIR, XPS and TG-MS analyses. The functionalized h-BNNSs show higher concentration, improved compatibility and dispersity in solvents and gel matrices after doping them into organically-modified silicate gel glasses using a sol-gel method. The functionalized h-BNNSs have broadband absorption and their doped glasses show high transmittances in the visible and near-infrared regions. The nonlinear optical properties of the functionalized h-BNNSs and their doped glasses were measured using Nd:YAG laser system and the doped glasses show broadband optical limiting responses at 532–1570 nm with the lowest onset threshold of 9 mJ cm−2. The optical limiting mechanisms investigated through Z-scan technique were nonlinear absorption. This work indicates that the functionalized h-BNNSs and their doped glasses are promising candidates for nonlinear optical, optical limiting and other optoelectronic materials and devices.

Oxygen surface groups analysis of carbonaceous samples pyrolysed at low temperature

The basis of recently developed quantitative TG-MS analysis was used for the evaluation of TPD-MS measurements in order to characterize the changes in the surface chemistry of carbon cryogels after the oxidation/activation treatment. This methodology was applied to the analysis of partially pyrolysed carbon cryogels (400 °C), which were oxidized/activated in four different ways (phosphoric acid, Fenton like reaction, ammonium persulfate with sulfuric acid and nitric acid with hydrogen peroxide). The quantitative TPD-MS evaluation enables analysis of all the evolved gases during the sample heating (without the calibration of all gases) and distinguishes the carbonization process from the decomposition of the more thermally stable oxygen surface groups (analysis of the effect of oxidation/activation reagents). The activation by H3PO4 results in the hydrolysis and esterification of anhydrides, lactones and phenols and creation of phosphoric acid esters (C-O-P), which decompose into C3-P=O linkages with the CO evolution. All the oxidation treatments had a similar effect on the surface chemistry. The amounts of carboxylic acids and anhydrides increased significantly, while the amount of lactones and phenol groups decreased (oxidized into carbonyls). Application of TG-MS fundamentals to the evaluation of TPD-MS profiles from a wide range of samples allows determining all the gaseous products.

TG-MS Analysis on Residual Solvents in a Pharmaceutical Substance

TG-MS Analysis on Residual Solvents in a Pharmaceutical Substance

Combustion characteristics of biodried sewage sludge

In this study, effects of biodrying on the characteristics of sewage sludge and the subsequent combustion behavior were investigated. 7-Day of biodrying removed 49.78% of water and 23.17% of VS initially contained in the sewage sludge and increased lower heating value (LHV) by 37.87%. Meanwhile, mass contents of C and N decreased from 36.25% and 6.12% to 32.06% and 4.82%, respectively. Surface of the biodried sewage sludge (BDSS) appeared granulated and multi-porous, which was thought to facilitate air transfer during combustion. According to thermogravimetric (TG) analysis coupled with mass spectrometer (MS) with a heating rate of 10 °C/min from 35 °C to 1000 °C, thermally-dried sewage sludge (TDSS) and BDSS lost 74.39% and 67.04% of the initial mass, respectively. In addition, combustibility index (S) of BDSS (8.67 × 10−8 min−2 K−3) was higher than TDSS. TG-MS analyses also showed that less nitrogenous gases were generated from BDSS than TDSS. It was again showed that the average CO and NO concentrations in exit gas from isothermal combustion of BDSS were lower than those from TDSS, especially at low temperatures (≤800 °C). Based on these results, it was concluded that biodrying of sewage sludge was an energy-efficient water-removal method with less emission of air pollutants when BDSS was combusted.

Inherently flame retardant vinyl bearing hyperbranched polysiloxanes having improved thermal stability-Ceramization and analysis of associated thermal properties

This study describes the synthesis and characterization of novel hyperbranched silicone polymers having high thermal stability and inherent flame retardancy achieved purely by molecular architecture, without the incorporation of any specific additive or filler. A series of hyper-branched terpolymers (MeDPhDViT) containing vinyl, phenyl and methyl moieties were synthesized by the acid catalysed copolymerization of vinyltriethoxysilane (VTES), diphenyldimethoxysilane (DPDMS) and dimethyldiethoxysilane (DMDES). Curing of these polymers is effected through condensation of the hydroxyl groups triggered by dibutyltindiluarate (DBTDL) catalyst. Glass to rubber transition temperature (Tg)of the cured polymers vary systematically from −110 °C to +50 °C with the increase in the content of vinyl T (ViT) units in the polymer backbone. The terpolymer with maximum ViT-unit content shows an onset of thermal decomposition above 540 °C and leaves 86% char residue at 900 °C, attributed to the retardation of depolymerisation by ViT unit. The limiting oxygen index (LOI) of the terpolymers increases from 26 to 37% with increase in ViT unit content alone, from 13.4 to 53.3 mol% and the terpolymer with 53.3 mol % ViT unit rates as V-0, the best in the UL-94 flame test. The ceramic residue from the cured elastomer comprises of free carbon and silica/Si-O-C ceramics. A probable mechanism has been proposed for the rearrangement of vinyl groups to carbonaceous ceramics under high temperature environment. The vinyl groups promote the formation of a carbonized, in particular graphitized, layer and SiOC phases during pyrolysis, as evidenced by TG-MS, pyrolysis GC-MS, Raman spectroscopy and FESEM analysis. Comparative study with a non-phenylated silicone elastomer confirms the mechanism of formation of carbon rich residue by the thermal rearrangement of vinyl groups.

Facile preparation of Ni/Al2O3 catalytic formulations with the aid of cyclodextrin complexes: Towards highly active and robust catalysts for the direct amination of alcohols

A series of Ni/Al2O3 catalysts with variable Ni loading (2–20 wt%) were prepared by aqueous wet impregnation of a nitrate precursor using native cyclodextrins as metal complex hosts. The impact of β-CD was carefully characterized at different stages of the preparation by a set of complementary techniques including TG-MS analysis, mass spectrometry, X-ray diffraction, temperature-programmed reduction, CO pulse chemisorption, X-ray photoelectron spectroscopy and electron microscopy. It was found that the use of cyclodextrins afforded a much higher Ni dispersion and narrower distribution of Ni particle sizes, as well as a much higher availability of reduced surface Ni species. As a result, the cyclodextrin-assisted catalysts exhibited enhanced catalytic properties in the direct amination of benzyl alcohol with aniline and 1-octanol with ammonia, both operated via the hydrogen borrowing mechanism. Furthermore, the use of cyclodextrins allowed a significant improvement of the robustness of the catalysts by mitigating the nickel leaching during reaction.

Thermal conversion of polyolefins/polystyrene ternary mixtures: Kinetics and pyrolysis on a laboratory and commercial scales

The thermal treatment of the three-component mixtures of polyethylene, polypropylene and polystyrene has been investigated. Thermal reactions have been described and the kinetics of thermal decomposition using the Friedmańs differential isoconversional method have been evaluated; slow pyrolysis on a laboratory scale and the pyrolysis of a contaminated waste mixture on a commercial scale have been carried out. The obtained results show that polystyrene radicals promote the decomposition of polyolefins, as a result of which the thermal decomposition of polyethylene and polypropylene proceeds faster and the yields of the gas and oil obtained during pyrolysis are quite high: 4–6wt.% of gas and 88–90wt.% of oil in the case of laboratory-scale pyrolysis and 15wt.% of gas and losses and 80wt.% of oil in the case of commercial-scale pyrolysis. TG-FTIR and TG-MS analyses have proved that the composition of volatile pyrolysis products varies. In the case of the ternary mixture with prevailing polyethylene (and polypropylene and polystyrene being in minority), the volatiles contained mainly aliphatic hydrocarbons and substituted benzenes; in the case of the ternary mixture with prevailing polypropylene, a significantly higher amount of substituted alicyclic compounds was found. This was confirmed by the GC–MS analysis of the oils obtained. Considering the quite high HHV and LHV of oils (46–48MJ/kg and 43–45MJ/kg, resp., in the case of laboratory-scale pyrolysis and 43 and 41MJ/kg, resp., in the case of commercial-scale pyrolysis) as well as the very low content of sulfur and nitrogen, the oils can be used as a clean liquid fuel; because of their composition, they can also serve as a source of chemicals and solvents.