Thermal Gravimetric Differential Scanning Calorimetry Research Articles

Highly efficient scallop seashell-derived catalyst for biodiesel production from sunflower and waste cooking oils: Reaction kinetics and effect of calcination temperature studies

The sustainable production of biodiesel from waste materials has become of utmost importance in recent years. In this study, cheap CaO catalysts were prepared by calcination of waste scallop seashells (Noble Pectin). The seashells were thermally treated at different temperatures (600–1000 °C) and then used in the transesterification of sunflower oil for biodiesel production. The catalysts were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and simultaneous Thermal Gravimetric-Differential Scanning Calorimetry (TG-DSC) techniques. The highest Fatty Acid Methyl Esters (FAME) yield (97%) was obtained in the presence of the catalyst calcined at 700 °C under the following conditions: a methanol-to-oil molar ratio (MOMR) of 12:1, a catalyst-to-oil ratio (CTOR) of 10 wt%, a stirring rate of 700 rpm, a reaction temperature of 65 °C and a reaction time of 4 h. The seashell-derived catalyst was practically stable for at least 4 consecutive runs in the reusability study, maintaining a high FAME yield (>92%). The reaction followed pseudo-first order kinetics, with an activation energy (Ea) of 133.57 kJ/mol and a pre-exponential factor (A) of 4.025 × 1018 min−1. This catalyst additionally exhibited a very high activity in the transesterification of waste cooking oil, with a similar FAME yield of 97%. This shows that this catalyst is promising for potential biodiesel production scale-up schemes and industrial applications.

Optimized Ni/Al2O3–SiO2 Catalyst for Steam Reforming of Phenol with Enhanced Hydrogen Production and Stability

Abstract Well-designed Ni/Al2O3–SiO2 catalysts synthesized with nickel as the active metal and alumina–silica as the catalyst mixture support were investigated for steam reforming of phenol with enhanced hydrogen production and stability. The prepared catalysts were characterized using x-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller (BET), Fourier transform infrared, hydrogen temperature-programmed reduction, pyridine diffuse reflectance infrared Fourier transform spectroscopy (Py-IR), and thermal gravimetric-differential scanning calorimetry (TG-DSC) techniques in detail. The BET results show that their specific surface areas ranged from 29.832 to 220.330 m2·g–1. The Py-IR results indicate the existence of large Lewis acid regions in the pure C-Ni (“C-Nix-Siy” means the Ni/Al2O3-to-SiO2 catalyst prepared with Ni(CH3COO)2 · 4H2O with SiO2 support mass ratios of y/(x + y).) and C-Ni4-Si1. The effects of the Ni/Al2O3-to-SiO2 mass ratio, reaction temperature, and active metal salt anion species on catalytic activity were studied. The results show that the C-Ni4-Si1 catalyst using nickel acetate tetrahydrate as the active metal salt with an SiO2 mass ratio of 20 wt% achieves a maximum phenol conversion of 97.3 % and hydrogen production of 92.7 % at 550°C. The stability of C-Ni4-Si1 was further investigated, and it was shown to react continuously and stably for more than 800 min at 550°C with excellent catalytic reaction stability. A final weight loss of only 9.31 % shown in the TG-DSC result of the spent C-Ni4-Si1 catalyst confirmed the excellent thermal stability and low coking rate of C-Ni4-Si1.

Effect of CeO2 and Pt introduction on the structure and performance of Fe2O3 for Hg0 removal

In this work, the thermal stability and catalytic activity of Fe2O3 catalyst for Hg0 oxidation were improved by the introduction of CeO2 and Pt. During high-temperature calcination at 400 °C, the mesoporous structure of Pt/CeO2/Fe2O3 remained stable, and it also retained higher specific surface area and lower average pore size than Fe2O3. The X-ray diffraction, transmission electron microscopy, and thermal gravimetric-differential scanning calorimetry results revealed that the modification of CeO2 and Pt retarded the crystallization and growth of Fe2O3 grains during high-temperature calcination, limiting Fe2O3 particles to a smaller size. Temperature-programmed desorption experiments showed that Hg0 adsorption of Pt/CeO2/Fe2O3 was promoted. In addition, X-ray photoelectron spectroscopy spectra suggested that adding CeO2 and Pt also increased the content of chemisorbed oxygen and transformed Fe2O3 into an electron-rich state, which consequently improved its catalytic performance for Hg0 oxidation.

Study on alkylsilane-incorporated cement composites: Hydration mechanism and mechanical properties effects

Three silanes with different alkyl chain lengths were incorporated into PII 52.5 ordinary Portland cement to investigate their effects on cement hydration and mechanical development. The micro-mechanism of hydration process and hydrated products were well studied using Calorimeter, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Thermal gravimetric-Differential scanning calorimetry (TG-DSC). Results demonstrated that different alkylsilanes had diverse effects on cement hydration. In general, the shorter the alkyl chain length, the stronger the retardation. Furthermore, the porosity change due to the silane incorporated could be another reason for the decrease of the mechanical properties. Additionally, SEM images show that there are some fiber-like needle products formed on the surface of hydrated cement substrate. According to EDS analysis, they are likely composed of 2,4,4-trimethyl pentyl triethoxysilane (S1) and n-dodecyl triethoxysilane (S3), which might be produced from the reaction between calcium hydroxide and silane. In terms of water absorption reduction, S1 shows the lowest water uptake, which benefits from the branched structure in alkyl group of S1.

Enhanced oxidation and graphitization resistance of polycrystalline diamond sintered with Ti-coated diamond powders

To improve the oxidation and graphitization resistances of the polycrystalline diamond (PCD), Ti coating was deposited on the diamond powders via magnetic sputtering method, which achieved a uniform TiC protection barrier in PCD during the sintering process. The phase compositions, microstructures and thermal stability of Ti-PCD were characterized by X-ray diffraction (XRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and thermal gravimetric-differential scanning calorimetry (TG-DSC). The results demonstrate that the oxidation and graphitization resistances of PCD are strengthened due to the existence of TiC phase, which acts as an effective inhibitor. The as-received inhibitor delays the oxidation and graphitization of PCD, elevating their initial temperature by ∼50 °C and ∼100 °C, respectively. During the annealing treatment of Ti-PCD, the priory oxidation of TiC, which produces TiO2 as an oxygen barrier, postpones the diamond oxide. Moreover, the TiC barrier also protects diamond grains from direct contact with cobalt, thus a lower cobalt-catalytic graphitization, and yields to an improved graphitization resistance of PCD. The enhanced oxidation and graphitization resistances of PCD are of significant importance for practical applications to elevated temperatures.

Effect of high temperature annealing on ultrahard polycrystalline diamond in air and vacuum conditions

The effect of high temperature annealing on ultrahard polycrystalline diamond (UHPCD) has been investigated in air and vacuum conditions up to 1500 °C. The thermal stability, carbon bonds, morphologies and wear resistance of UHPCD were evaluated by thermal gravimetric-differential scanning calorimetry (TG-DSC), Raman spectroscopy, scanning electron microscopy (SEM) and wear tester. The thermal analysis results indicated that the thermal stability of chemical vapor deposited (CVD) diamond was better than that of polycrystalline diamond (PCD) even though it was weakened by high pressure high temperature treatment, while no graphitization was observed on UHPCD in flowing argon up to 1500 °C. When the UHPCD annealed in air, the oxidation damage with the extension of cracks and spalling holes was observed on CVD diamond as the evolution of temperature. The result confirmed by the changes of diamond peak position and full width at half maximum (FWHM) in Raman spectra curves. The PCD had shown the damage with cracks induced exfoliation of binder regions and cracks ruined diamond grains. However, the diamond peak position and FWHM of CVD diamond and PCD showed slight reduction as a function of vacuum annealing temperature with no detectable change of morphologies. The high temperature annealing has strong impact on the wear resistance of UHPCD in air while slightly in vacuum.

Thermal damage mechanisms of Si-coated diamond powder based polycrystalline diamond

The polycrystalline diamond (PCD) composites were synthesized from Si-coated diamond or diamond powder mixtures with Si. The characterizations of phase structures, morphologies and thermal stability of PCD were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal gravimetric-differential scanning calorimetry (TG-DSC). The thermal damage mechanisms of PCD were studied under air condition up to 750 ℃ by thermal weight loss, XRD, SEM and wear tester. The results showed that the PCD was successfully synthesized by the Si-coated diamond with a homogeneous structure. The thermal stability and wear resistance of PCD with Si-coated diamond were better than those of PCD with uncoated diamond. It was determined that the chemical thermal damage mechanism with oxidation reaction dominated the damage of the PCD after high temperature annealing and the physical thermal damage mechanism also took effect on the exfoliation of binder and fine diamond grains from PCD.

Facile in-situ synthesis of NbB2 nanoparticles at low temperature

Niobium diboride (NbB2) nanoparticles have been successfully synthesized at 800 °C in a single step from niobium penta-oxide (Nb2O5), magnesium (Mg) and borax (Na2B4O7·10H2O) in an autoclave. The synthesis temperature and holding time have been optimized to obtain single phase NbB2. The phase determination, thermal stability and morphological features of synthesized samples have been analyzed by X-ray diffraction (XRD), thermal gravimetric-differential scanning calorimetry (TG-DSC) and electron microscopic technique respectively. Williamson-Hall (W-H) analysis has also been done to observe the effects of synthesis parameters (temperature and holding time) on crystal distortion. With the help of XRD, microstructural features and thermodynamic calculations, formation mechanism for the synthesized samples has been predicted.

Characterization and synthesis of nanometer magnetite black pigment from titanium slag by microwave-assisted reduction method

The comprehensive utilization of titanium slag can not only reduce pollution, but also bring considerable social and environmental benefits. Nanometer magnetite black pigment has been synthesized by microwave-assisted reduction method under nitrogen. The properties of nanometer magnetite black pigment were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, thermal gravimetric-differential scanning calorimetry, zeta potential, Brunauer–Emmett–Teller method and colorimetric analysis. The formation of nanometer magnetite black pigment was confirmed by XRD, FTIR, RM and XPS. FESEM and TEM indicated that nanometer magnetite pigment with the average diameter of ∼52 nm was virtually spherical, having a porous structure. The BET surface area and the pore volume of nanometer magnetite black pigment were found to be about 18.48 m2 g−1 and 0.081 cm3 g−1 respectively. The TG-DSC analysis shows that nanometer magnetite black pigment has good thermal stability in low temperature. Nanometer magnetite has good dispersion by zeta potential analysis in water. Besides, nanometer magnetite black pigment exhibits a promising prospect of application in water-based pigment.

Crystalline-selected synthesis of ferrous oxalate dihydrate from spent pickle liquor

Ferrous oxalate dihydrate with different crystalline structures, polymorphs and sizes have been synthesized through a facile precipitation reaction from spent pickling liquors (SPL) by controlling synthesis conditions. The β-FeC2 O4 · 2H2 O in orthorhombic phase can be formed at room temperature, whereas α-FeC2 O4 · 2H2 O with a monoclinic unit cell can be obtained after aging at 80 °C. With the increasing aging temperature, the morphology of samples can be tailored from flower-like to prismatic-like and the particle-sizes are decreased. Innovatively, thermal decomposition behaviors of products have been investigated in details by X-ray diffraction pattern (XRD) and thermal gravimetric-differential scanning calorimetry (TG-DSC). The results show that both FeC2 O4 · 2H2 O samples can be transformed to α-Fe2 O3 in air atmosphere and Fe3 O4 in argon atmosphere at T ≧ 400 °C. In air atmosphere, there are two sharp exothermic peaks for β-FeC2 O4 · 2H2 O (250 °C) and α-FeC2 O4 · 2H2 O (239.5 °C) correspond to the decomposition reactions. In argon atmosphere, the decomposition end temperatures are 500 °C and 430 °C for β-FeC2O4 · 2H2O and α-FeC2O4 · 2H2O, respectively. This indicates that β-FeC2O4 · 2H2O has higher thermal stability in comparison with α-FeC2O4 · 2H2O.