Thermogravimetric Derivative Thermogravimetry Research Articles

Hierarchical ZSM-5 zeolite using amino acid as template: Avoiding phase separation and fabricating an ultra-small mesoporous structure

Hierarchical ZSM-5 was successfully prepared using l-carnitine and l-lysine as mesoporous templates, and the influence of the dosage of “secondary template” represented by l-carnitine on the formation of hierarchical zeolite was investigated in detail. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption, nuclear magnetic resonance (NMR), thermogravimetric-derivative thermogravimetry (TG-DTG), pyridine infrared and temperature programmed desorption of ammonia (NH3-TPD) were used to characterize the structural and textural properties of the as-prepared samples. The results showed that the hydrophilic property of the amino acid template overcame the phase separation and constructed a mesoporous system with an ultra-small size of 2–10 nm in the as-synthesized zeolite crystals. Not only the morphology and grain size, but also the Si/Al ratio and then the acidity of zeolite were affected by the “secondary template”. Catalytic cracking of triisopropylbenzene was chosen as a probe reaction so as to investigate the effect of the fabricated hierarchical porous system on the catalytic performances of the catalysts. The results showed that the introduction of hierarchical pores elevated the external surfaces of the catalyst and therefore significantly improved the catalytic cracking performance of the catalyst for the heavy molecules triisopropylbenzene. At the same time, the introduced mesopore structure also gave the macromolecule reactant a hierarchically cracking process because of the acid active sites located in the different spaces.

Investigation and prediction of co-pyrolysis between oily sludge and high-density polyethylene via in-situ DRIFTS, TGA, and artificial neural network

Oily sludge (OS), a hazardous waste produced in a large amount in petroleum industries, has raised great interest in research, and thermal treatment method such as pyrolysis is promising to achieve the goal. This research studied the pyrolysis behavior during co-pyrolysis of OS and high-density polyethylene (HDPE, plastic waste model component) with different blend ratios. The changes of functional groups against pyrolysis temperature were detected via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interactive effect between the two feedstocks during co-pyrolysis was analyzed via thermogravimetric analysis (TGA). The DRIFTS showed that the pyrolysis of HDPE can provide abundant •CH3 free radicals which may accelerate the pyrolysis of OS. The disparities between theoretical and experimental thermogravimetric/derivative thermogravimetry (TG/DTG) curves of mixtures indicated a synergistic interaction during co-pyrolysis. Besides, the activation energy of co-pyrolysis was obtained based on kinetic analysis, which showed that the average activation energy followed the trend of O3H1 < OS < O1H1 < HDPE < O1H3. In addition, two artificial neural network (ANN) models, namely ANN model Ⅰ with training and testing R2 of 0.99 (for prediction of interactive effect) and ANN model Ⅱ with training and testing R2 of 0.92 (for prediction of activation energy), were established and validated by comparing with the experimental data, which showed satisfied credibility. Ultimately, the two ANN models were used to reversely guide and optimize experiment design for the highest synergistic effect and the minimum activation energy. This study offers a new insight and strategy to aid pyrolysis experimental studies.

Synthesis of triarylpyridines with sulfonate and sulfonamide moieties via a cooperative vinylogous anomeric-based oxidation

Herein, novel magnetic nanoparticles with pyridinium bridges namely Fe3O4@SiO2@PCLH-TFA through a multi-step pathway were designed and synthesized. The desired catalyst and its corresponding precursors were characterized with different techniques such as Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 13C NMR, Mass spectroscopy, energy dispersive X-ray (EDX) analysis, thermogravimetric/derivative thermogravimetry (TG/DTG) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). In addition, the catalytic application of the prepared catalyst in the synthesis of new series of triarylpyridines bearing sulfonate and sulfonamide moieties via a cooperative vinylogous anomeric-based oxidation was highlighted. The current trend revealed that the mentioned catalyst shows high recoverability in the reported synthesis.

Improvement of the oxidation resistance of silicon‐containing arylacetylene resins upon the introduction of carbazoles

AbstractSilicon‐containing arylacetylene resins (PSAs) can be used in high temperature environment due to their excellent thermal stability. However, their high temperature oxidation is still bottle‐neck for further application. Herein, Materials Genome Initiative (MGI) was utilized to identify a target monomer, 3,6‐diethynylcarbazole (DEC), to design new PSAs with enhanced antioxidant properties and heat resistance. After incorporation of DEC, the thermal curing behavior observed using differential scanning calorimetry (DSC), fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) revealed that obtained silicon‐containing carbazolylacetylene resins (PSA‐VBC) can exhibit hydroamination reaction to decrease the initial curing temperature. And the temperature at 5% weight loss (Td5) occurred in cured copolymers ranged from 665°C to 691°C, which showed excellent heat resistance. Moreover, the oxidation behavior of cured resins was investigated by thermogravimetric/derivative thermogravimetry (TG/DTG), X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). Upon the incorporation of DEC, the thermal oxidation decomposition temperature of PSA‐VBC were 100°C higher than those observed for PSAs, which also proved by XPS analysis results that the oxygen content of PSA‐VBC solidified oxide was lower than that of PSAs. In addition, the surface morphology of cured PSA‐VBC resins still maintained integrity after oxidation at 400°C for 2 hr, which showed excellent oxidation resistance.

Characterization of lactobionic acid evidencing its potential for food industry application

AbstractThe chemical configuration of the lactobionic acid (LBA) evidences its potential properties, among which the antioxidant, antimicrobial, and chelating activities stand out in the literature. However, few studies aim at testing and confirming them. The purpose of this study was to determine some selected LBA properties, whose characteristics are of interest for its use as an ingredient in foodstuffs. The discussion followed the results of Fourier‐Transform Infrared Spectroscopy (FTIR), X‐ray diffractometry (XRD), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) radical, thermogravimetric/derivative thermogravimetry (TGA/DTG), minimal inhibitory concentration (MIC) by the diffusion disk test, scanning electron microscopy (SEM), and iron/calcium chelating methodologies. The XRD analysis revealed the presence of an amorphous halo and the absence of defined peaks, a fact possibly related to its high hygroscopicity. The FTIR showed characteristic bands of the LBA structure. Results from TGA/DG verified the LBA thermal degradation, which evidenced that LBA could participate in most food industry unit processes within the first mass loss event. Antioxidant capacity reached a maximum inhibition of 56% for LBA and the chelating capacity of the iron ion achieved 54% of chelated ions, while the calcium ions reached 15%. The results revealed high potential of LBA application for microbial inhibition, moisture retention, and texture maintenance throughout storage of food products.Practical ApplicationsDespite the potential of application of the LBA, few quantitative results demonstrate its ability of action in food. Even without permission in most countries around the world, more research with LBA will encourage the investigation of its toxicology, expanding the areas of application. Its thermal degradation profile and elevated solubility demonstrated the potential of LBA as food ingredient, performing moreover as antioxidant, chelating agent, antimicrobial, and texturizer. The results open the possibilities for many applications in the field of food chemistry and food industry.

Thermal decomposition kinetics of sodium carboxymethyl cellulose: Model-free methods

Thermal analysis techniques such as thermogravimetric analysis (TGA) have been widely used because they provide rapid quantitative determination of various processes under isothermal or non-isothermal conditions. It allows the estimation of effective kinetic and thermodynamic parameters for various decomposition and thermal reactions. In this article, thermal degradation of sodium carboxymethyl cellulose (SMC) is investigated by means of dynamic thermogravimetric/derivative thermogravimetry (TG/DTG) in helium atmosphere with the flow rate 100 mL/min at the heating rate of 10-30 °C/min until the furnace wall temperature reached 700 °C. The non-isothermal degradation of SMC found to be taking place occurred major one step and minor two steps. Using a non-isothermal kinetic method based on a TGA data, kinetic parameters ( E and ln A ) are calculated by Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Friedman methods. The results of studied polymer demonstrated that E and ln A is varied with function of conversion (α), which is in good agreement with literature data.

The green adsorption of chitosan tripolyphosphate nanoparticles on cotton fiber surfaces

Chitosan nanoparticles (chitosan NP) were effectively incorporated onto cotton fiber surfaces during a green adsorption without any cross-linking agents in this work. The interactions between cotton fibers and chitosan NP during the green adsorption were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric-derivative thermogravimetry (TG-DTG) and scanning electron microscopy (SEM) in detail. The results indicated that the intermolecular hydrogen bond interactions exited between the hydroxyl groups of cotton fibers and the amino groups of chitosan NP, and progressively enhanced with the increase in chitosan NP mass concentrations. After chitosan NP adsorption, the acidity of fibers augmented and the crystallinity index of fibers declined owing to the increasing interactions. In addition, the hydrophobic interactions occurred between chitosan NP and crystalline cotton fibers, thereby resulting in the preferential adsorption onto the hydrophobic (200) crystallographic plane.