First-order Reaction Mechanism Research Articles

Further insights into steady three-dimensional MHD Sakiadis flows of radiating-reacting viscoelastic nanofluids via Wakif’s-Buongiorno and Maxwell’s models

AbstractKeeping in mind the stress relaxation tendency of many viscoelastic multi-phase flows (e.g., polymer solution flows and transport phenomena of red cell suspensions within blood media), the present research investigation intends principally to develop a realistic model for revealing properly the aspects of reacting-radiating Maxwell nanofluids during their laminar boundary layer flows in the steady regime over a horizontal impermeable surface under a transversal magnetic influence. For this purpose, the principal leading differential formulation is derived theoretically by linking Wakif’s-Buongiorno approach with Maxwell’s model. By invoking fundamentally the general boundary layer assumptions and the passive control strategy for the nanoparticles, the governing PDEs’ formulation is simplified accordingly and then stated properly for the case of the convective heating condition at the impermeable bi-stretching surface. By executing a feasible non-dimensionalization technique, the monitoring ODEs’ system is achieved successfully, whose solutions are presented precisely in different illustrative scenarios using Richardson’s extrapolation method. After carrying out successfully several validating tests, it is demonstrated that the weakly viscoelastic feature has generally a slight delaying effect on the nanofluid motion. This dynamical weakening can be reinforced more with the generation of thermal energy by intensifying the external magnetic field source. Additionally, these physical factors show an intensifying influence on the surface drag forces. However, a dropping impression is seen for the local heat transfer at the contact surface. Contrary to the broadening impact of the radiative heat transfer as well as the convective heating and thermophoresis mechanisms on the thermal and mass boundary layer regions, it is witnessed that the first-order chemical reaction mechanism and Brownian’s motion exhibit a shrinking impact on the mass boundary layer region.

Decolorization by Catalytic Ozonation USING Mn(II) Fe(II) and Fe(III)

The textile industry holds significant importance in Thailand. It has been estimated that 10-20% of dyes are lost during the dyeing process and subsequently released into wastewater. The high concentration of non-biodegradable substances in these wastewaters makes them challenging to treat using conventional methods. Therefore, this study aimed to assess the effectiveness of a catalytic ozonation process employing Mn(II), Fe(II), and Fe(III) for treating synthetic dye wastewater. The study also sought to optimize operational parameters such as pH and contact time. Both with and without catalytic ozonation, experiments were conducted in a batch reactor with a consistent ozone flow rate of 6 g/hr. Under the non-catalytic ozonation conditions, it was observed that more than 90% of decolorization occurred within 15 minutes at a pH of 9. The ozonation of the dye followed a first-order reaction mechanism at room temperature, with a rate constant (k) of 0.18 min-1. The catalytic ozonation used a concentration of 1.2 mM of Mn(II) was showed color removal of 90% in 8 min. For catalytic ozonation used Fe(II) and Fe(III) with concentrations of 0.6 mM showed color removal of 90% in 10 min. The highest rate constant (k) showed 0.29 min-1 for Mn(II) and 0.21 min-1 for Fe(II) and Fe(III). In conclusion, the study found that the inclusion of a catalyst substantially enhanced the degradation efficiency of the dye compared to ozonation without a catalyst.

Kinetics of free fatty acids esterification in waste frying oil using novel carbon-based acid heterogeneous catalyst derived from Amazonian Açaí seeds – Role of experimental conditions on a simpler pseudo first-order reaction mechanism

This study reports the kinetics of free fatty acids esterification in waste frying oil, based on a simpler non-conventional pseudo first-order homogeneous reaction mechanism using a highly-efficient acid heterogeneous catalyst derived from seeds of Açaí (Euterpe oleracea Mart.), subjected to changes in temperature, catalyst dosage, MeOH:Oil ratio, and stirring speed. Statistical analyses revealed significant effects all four conditions (p < .05) on the reaction's apparent rate constant (k1) over their different pre-defined levels. Reaction mechanism was inferred to be fundamentally acid ionic exchanges with the oil/water film on catalyst's surface, neglecting kinetically controlled liquid-to-liquid splitting and autocatalyzed esterification.

Metabolic profiles and fingerprints for the investigation of the influence of nitisinone on the metabolism of the yeast Saccharomyces cerevisiae

Nitisinone (2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione, NTBC) is considered a potentially effective drug for the treatment of various metabolic diseases associated with disorders of l-tyrosine metabolism however, side-effects impede its widespread use. This work aimed to broaden the knowledge of the influence of NTBC and its metabolites 2-amino-4-(trifluoromethyl)benzoic acid (ATFA), 2-nitro-4-(trifluoromethyl)benzoic acid (NTFA), and cyclohexane-1,3-dione (CHD) on the catabolism of l-tyrosine and other endogenous compounds in Saccharomyces cerevisiae. Based on a targeted analysis performed by LC–ESI–MS/MS, based on multiple reaction monitoring, it was found that the dissipation kinetics of the parent compound and its metabolites are compatible with a first-order reaction mechanism. Moreover, it has been proven that formed NTBC metabolites, such as CHD, cause a decrease in l-tyrosine, l-tryptophan, and l-phenylalanine concentrations by about 34%, 59% and 51%, respectively, compared to the untreated model organism. The overall changes in the metabolism of yeast exposed to NTBC or its derivatives were evaluated by non-targeted analysis via LC–ESI–MS/MS in the ion trap scanning mode. Based on principal components analysis, a statistically significant similarity between metabolic responses of yeast treated with ATFA or NTFA was observed. These findings facilitate further studies investigating the influence of NTBC on the human body and the mechanism of its action.

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.

Thermal properties and pyrolysis kinetics of phosphate-rock acid-insoluble residues

In the phosphorous–sulphur two-step process for the clean production of phosphoric acid, a phosphate-rock acid-insoluble residue (PAIR) is a solid filter residue obtained via the phosphoric acid acidolysis of phosphate rock (PR). PAIR combined with other raw materials can be used to prepare cement, ceramics and glasses, opening a potential avenue for large-scale PAIR utilisation. However, the preparation of such materials requires high-temperatures calcination. Understanding the high-temperature thermal properties of PAIR can enable its more targeted comprehensive utilisation or disposal. In this study, the thermal properties and pyrolysis kinetics of PAIR were systematically studied using a multiple heating rate method based on thermogravimetric analysis and a kinetic model. Results showed that from room temperature to 1200 °C, the main changes in the PAIR were the complete removal of fluorine and sulphur, partial removal of phosphorus and conversion of quartz to cristobalite. Moreover, during these processes, H2O(g), NH3, N2, CO2, SO2, P2O5(g), CO, CF3+ and organic gases were volatilised. Herein, the pyrolysis kinetics of PAIR is divided into five stages. Stage 1 (conversion rate ɑ: 0.05–0.2) conforms to the random nucleation and growth as well as the Avrami–Erofeev (n = 2/3) mechanism; the corresponding mechanism function is F(ɑ) = [−Ln(1 − ɑ)]2/3. Stage 2 (ɑ: 0.2–0.4) conforms to the first-order chemical reaction mechanism; the corresponding mechanism function is F(ɑ) = −Ln(1 − ɑ). Stage 3 (ɑ: 0.4–0.6) conforms to the phase boundary–controlled reaction and one-dimensional movement mechanism; the corresponding mechanism function is F(ɑ) = ɑ. Stage 4 (ɑ: 0.6–0.8) conforms to the three-dimensional diffusion process (Jander model); the corresponding mechanism function is F(ɑ) = [1 − (1 − ɑ)1/3]2. Stage 5 (ɑ: 0.6–0.95) conforms to the one-dimensional diffusion process; the corresponding mechanism function is F(ɑ) = ɑ2.

Modelling of gas conversion with an analytical reactor model for biomass chemical looping combustion (bio-CLC) of solid fuels

Manganese ores are promising oxygen carriers for chemical looping combustion (CLC), due to their high reactivity with combustible gases. In this work, a manganese ore called EB (Elwaleed B, originating from Egypt) is studied for its reaction rate with CH4, CO and H2 and the data are used in an analytically solved reactor model. The reactivity of fresh and three used EB samples from previous operation in a 10 kWth pilot was examined in a batch fluidized bed reactor with CH4 and syngas (50%CO + 50%H2). In comparison with other manganese ores, the EB ore has a lower rate of reaction with CH4, while showing a significantly higher reactivity with syngas. Nevertheless, this manganese ore always presents a better conversion of CH4 and syngas than the benchmark ilmenite. Mass-based reaction rate constants were obtained using a pseudo first-order reaction mechanism: 1.1·10-4 m3/(kg·s) for CH4, 6.6·10-3 m3/(kg·s) for CO and 7.5·10-3 m3/(kg·s) for H2. These rate constants were used in an analytical reactor model to further investigate results from previous operation in the 10 kWth unit. According to the analytical model, in the 10 kWth operation, 98% of the char in the biomass fuels was gasified before leaving the fuel reactor, while the char gasification products (CO and H2) have a 90% contact efficiency with the bed material. On the contrary, the volatiles have a much lower contact efficiency with the oxygen carrier bed, i.e. 20%, leading to low conversion of volatiles released. Thus, the results emphasize the importance of improving the contact between volatiles and bed material in order to promote combustion performance in the CLC process.

Comparative study of catalytic performance and degradation kinetics of biodiesels produced using heterogeneous catalysts from kaolinite

This study comparatively investigates the catalytic activities and degradation kinetics of the produced biodiesels using kaolinite-based heterogeneous catalysts to examine the stability. The performance of the catalysts was tested under the same operating parameter (methanol/oil ratio, 5:1, at 200 °C for 6 h). The obtained biodiesel was analyzed using TGA equipment to obtain the yield, as well as the degradation kinetic parameters. It was observed that the solid superacid SHY zeolite gave the highest biodiesel yield (90.76%) because of higher acid strength. The catalysts performance is in the order of HY<ALK<HLK<NaLK<SHY zeolite. The lower performance of HY (72.42% yield) is attributed to the presence of high basic sites, being that shea butter has high FFA. The degradation kinetics of each biodiesel sample was performed using the TGA data to examine the thermal and oxidative stability. The frequency factor (A), activation energy, and reaction order were determined by employing the Coats-Redfern model. It was observed that first-order reaction mechanism can satisfactorily describe all the biodiesel kinetics. Further, the biodiesel from SHY zeolite gives the highest EA (98.65 kJ/mol). This result indicates that SHY zeolite is the best catalyst in terms of biodiesel yield and stability.

Kinetic Study of the Isothermal Degradation of Pine Sawdust during Torrefaction Process.

The reaction kinetics of solid fuel is a critical aspect of energy production because its energy component is determined during the process. The overall fuel quality is also evaluated to account for a defined energy need. In this study, a two-step first-order reaction mechanism was used to model the rapid mass loss of pine sawdust (PSD) during torrefaction using a thermogravimetric analyzer (Q600 SDT). The kinetic analysis was carried in a MATLAB environment using MATLAB R2020b software. Five temperature regimes including 220, 240, 260, 280, and 300 °C and a retention time of 2 h were used to study the mechanism of the solid fuel reaction. Similarly, a combined demarcation time (i.e., estimating the time that demarcates the first stage and the second stage) and iteration technique was used to determine the actual kinetic parameters describing the fuel’s mass loss during the torrefaction process. The fuel’s kinetic parameters were estimated, while the developed kinetic model for the process was validated using the experimental data. The solid and gas distributions of the components in the reaction mechanism were also reported. The first stage of the degradation process was characterized by the rapid mass loss evident at the start of the torrefaction process. In contrast, the second stage was characterized by the slower mass loss phase, which follows the first stage. The activation energies for the first and second stages were 10.29 and 141.28 kJ/mol, respectively, to form the solids. The developed model was reliable in predicting the mass loss of the PSD. The biochar produced from the torrefaction process contained high amounts of the intermediate product that may benefit energy production. However, the final biochar formed at the end of the process increased with the increase in torrefaction severity (i.e., increase in temperature and time).

Insights into pyrolysis of torrefied-biomass, plastics/tire and blends: Thermochemical behaviors, kinetics and evolved gas analyses

The pyrolysis behaviors, the kinetics of the synergistic effects, the functional groups during the co-pyrolysis of torrefied-biomass (TBG) with a tire, and different plastics such as high-density polyethylene (HDPE), ethyl vinyl acetate (EVA), polystyrene (PS), polypropylene (PP) were analyzed by TG-FTIR. The TG-DTG curves revealed thermal stability due to torrefaction treatment and blending. The most potential reaction mechanisms associated with the first stage for both pure and blend samples were first-order reaction and one-dimensional diffusion mechanisms, while the second stage was mostly governed by second and third-order reaction mechanisms. The interactions between TBG-plastics/tire were obvious at temperatures of 290–540 °C, according to the variation of weight loss (ΔW) values. The highest degree of synergy was observed with the TBG/PS blend, while the TBG/tire mixture being the least synergistic. The FTIR spectra indicated that hydrocarbons compounds, CO2, CO, H2O, CH4, NH3, acid, aldehydes and C=O, C-O, O-H, C-H, C-C, N-H, HCN were the main gaseous products and functional groups detected by the FTIR. The HDPE, EVA, and PP generated mainly alkanes and alkenes. While the PS depolymerized into styrene monomers. The tire mainly disintegrated into olefins and alkanes. The effect of co-pyrolysis of TBG, tire, and different plastics on species produced is noticeable on pyrolysis characteristics, kinetics, gaseous products, and functional groups. Thus, H2O, acid, ketone, and aldehydes were suppressed. Generally, the co-pyrolysis of plastic/tire with TBG can reduce the oxygen-containing compounds in the gaseous species and can improve the release of hydrocarbons.

Design of Mn(II), Fe(III) and Ru(III) chalcone complexes: Structural elucidation, spectral, thermal and catalytic activity studies

New Mn(II), Fe(III) and Ru(III) coordination compounds with chalcone ligand (L) were prepared. The synthesized complexes have been established by elemental analysis, molar conductance, XRD, TGA, magnetic moment measurements, and UV–vis, electron impact mass and IR spectral studies. The spectral and analytical data revealed that the ligand behaves as tridentate with an octahedral geometry for all complexes. Molecular orbital calculations used to confirm the geometry of the isolated compounds. The kinetic and thermodynamic parameters for decomposition steps have been calculated. Furthermore, the catalytic activity of the complexes toward the degradation of Methyl Orange was examined. The synthesized complexes were applied to treatment the analytical chemistry laboratories wastewater through the degradation of methyl orange indicator as heterogeneous catalysts in the existence of H2O2 as an oxidizer. The results of the study have shown all synthesized complexes have catalytic activity toward the degradation of Methyl Orange. The catalytic activity performance evaluation shows 24, 44 and 85% with Mn(II), Fe(III) and Ru(III) complexes as catalyst respectively. The effect of catalyst mass (0.5–1.2 mg) and concentration of H2O2 (137–826 ppm) were checked using Ru(III) complex which the highest catalytic activity. The degradation % was found in the range 29–78% after 100 minute using different concentrations of H2O2 (137.7–826.2 ppm) with Ru(III) as a catalyst. Also, the data elucidate the degradation of methyl orange increase with the amount of Ru(III) complex increase. The investigations show the reactions obey the first-order reaction mechanism, and the rate constants have been determined.

Thermogravimetric Kinetics of Catalytic and Non-Catalytic Pyrolytic Conversion of Palm Kernel Shell with Acid-Treated Coal Bottom Ash

The catalytic and non-catalytic pyrolytic conversion kinetics of palm kernel shell (PKS) with untreated (as received) and H2SO4-treated coal bottom ash as catalyst were investigated in this study. Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) isoconversional kinetic models were exploited to evaluate the kinetic parameters. The study was conducted using thermogravimetric analysis at 10, 20, 30, and 50 °C/min heating rates. The activation energy (Ea) and pre-exponential factor (A) for non-catalytic PKS decomposition for DAEM ranged from 74.39 to 217.05 kJ/mol and 4.77E+01 to 1.99E+14 s−1 at different conversions while for the untreated ash, the ranges were 103.84–402.53 kJ/mol and 7.35E+03–1.04E+29 s−1. In the decomposition with treated ash, Ea and A were 81.79–191.07 kJ/mol and 1.61E+02–1.20E+12 s−1 for 7 wt% ash and 74.41–137.35 kJ/mol and 4.91E+03–4.53E+08 s−1. Values of Ea and A obtained for FWO followed the same pattern and are in close agreement with that obtained using DAEM. The use of 10 wt% acid-treated ash reduced the activation energy compared with the non-catalytic process by about 33.05% while the untreated ash increased the activation energy. The kinetic parameters were determined satisfactorily using the first-order reaction mechanism.

Hydrothermal treatment of banana leaves for solid fuel combustion

Banana residues remain untapped for substantial thermochemical energy conversion. In this study, lab-scale production of hydrochar from banana leaves (BL) by hydrothermal treatment (HT) for solid fuel combustion was investigated. The HT was conducted at 180, 200 and 220 °C for 30 min, resulting in an energy yield of up to 94.0%. The fuel properties of BL were enhanced after HT. The carbon content increased with increasing reaction temperature while oxygen and ash content decreased. The higher heating values of the hydrochars (20.4–22.7 MJ/kg) were greater than that of its biomass origin. Changes in the structural and fuel properties influenced the combustion behavior and reactivity of hydrochars according to thermogravimetric analysis. A first-order reaction mechanism by Coats–Redfern approximation was adopted to describe the kinetics of non-isothermal combustion. This study may prove useful in evaluating the potential of hydrochar from banana leaves for solid fuel applications.

Thermal degradation kinetics of ionic liquid [BMIM]BF4/TEA/PFSA composite membranes for fuel cell

20% ILs-TEA-PFSA composite membranes were prepared using the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4 (ILs) and were doped with triethylamine (TEA) to modify the perfluorosulfonic acid (PFSA). The thermal decomposition kinetics of the composite membrane was investigated using nonisothermal thermogravimetry in order to study the high-temperature durability of the ionic-liquid-doped industrial-grade perfluorosulfonic acid ion membrane for fuel cells. The results showed that the thermal degradation of the composite membranes occurs over three stages, for which the conversion rates are in the ranges of 0.01–0.1, 0.15–0.4 and 0.45–0.7. The average apparent activation energies of membrane degradation in the first, second and third stages are 151.3, 166.5 and 170.1 kJ mol−1, respectively. At a heating rate (β) of 20 °C min−1, the thermal degradation process of the composite mechanism follows an n = 4 reaction order mechanism, and the mechanism function f(α) is 1 − (1 − α)4 and g(α) is 1/4 (1 − α)−3. The heat resistance showed that if β is equal to 15 °C min−1, the lowest temperature at which the composite membrane decomposes by 1% is 363.5 °C. Similarly, when α is 0.32%, the thermal decomposition of the composite membrane occurs above 350 °C. Isothermal thermogravimetric analysis showed that the thermal lifetimes (t5% and t10%) of the composite membrane were 4.83 × 105 and 9.80 × 105 h, respectively. If α reached 5 and 10% under a nitrogen atmosphere at 180 °C, the isothermal decomposition process underwent a first-order reaction mechanism. The apparent activation energy (Ea) of the thermal degradation of the composite membrane was 166.8 kJ mol−1. In addition, using isothermal data from a 20% [BMIM] BF4/TEA/PFSA composite membrane at 688 K, based on a first-order reaction, the respective theoretical master curves were compared with the experimental master plots of dα/dθ/(dα/dθ)α=0.5, θ/θ0.5 and (dα/dθ)θ versus α.

Modeling of Ligand-Receptor Protein Interaction in Biodegradable Spherical Bounded Biological Micro-Environments

In this paper, we propose a generalized model for the Ligand-Receptor protein interaction in 3-D spherically bounded, diffusive biological microenvironments using molecular communication paradigm. Modeling a targeted cell as a receiver nano-machine, we derive analytical expressions for the Green’s function as well as for the expected number of the activated receptors. The molecular degradation in the environment due to enzymatic effects and the changes in pH levels are included via the first-order degradation reaction mechanism. A second-order reversible reaction mechanism is employed to model the reception process that involve the reaction of ligands to activate the receptor proteins lying on the receiver surface to form ligand-receptor complexes. We also present a particle-based simulator that incorporates the reversible reaction of molecules with the receptors present on the surface of a receiver that is located inside a bounded, 3-D microfluidic environment. Our simulations also include molecular degradation and boundary absorption of the ligands due to collision. The simulation results show perfect agreement with the results obtained from the analytical, bounded, and 3-D spherical model of the medium. The proposed models can be used for accurate prediction of the drug concentration profiles and number of activated receptors at any targeted cell.

Bamboo cellulose-derived cellulose acetate for electrospun nanofibers: synthesis, characterization and kinetics

Catalysts play a key role in the production of cellulose acetate (CA). In this study, CA derived from bamboo cellulose (BC) was synthesized in a solution mixture of acetic acid and acetic anhydride that contains catalysts. The catalytic activities of three catalysts (i.e., sulfuric, methyl benzene sulfonic, and dodecyl benzene sulfonic acids) were investigated in terms of kinetics of acetylation, which was established according to the first-order reaction mechanism. Based on this, cellulose-based nanofibers were further prepared from the acetylated BC solution using an electrospinning technique. Results in this study may be useful for the preparation and application of nanomaterials derived from natural polymeric materials.

Kinetics of DNA condensation with DPPC: effect of calcium and sodium cations

Kinetics of DNA condensation with zwitterionic lipid, dipalmitoylphosphatidylcholine, in the presence of calcium and sodium cations was investigated using fluorescence stopped-flow technique. The process was followed from two points of view: the changes on DNA were monitored with ethidium bromide, and fluorescently labelled phospholipid was used to follow the changes in the lipid bilayer. The measurements showed different reaction kinetics. In the case of the DNA side, a consecutive reaction mechanism was found, while two-step first-order reaction mechanism described well the processes on the lipid side. Both, sodium and calcium cations influence significantly the reaction mechanism. Calcium is necessary to condensate DNA with lipid, while sodium modulates the kinetics of the reactions considerably.

Preparation and kinetics study of biodiesel production from waste cooking oil using new functionalized ionic liquids as catalysts

In this work, 1,4-sultone and benzimidazolium-based ionic liquids (ILs) with four different anions were synthesized, and their structures were confirmed by nuclear magnetic resonance (NMR) and elemental analysis (CHNS). The acidity of the synthesized ILs was studied using Hammett acidity function and COSMO-RS. The waste cooking oil was used as a raw material for biodiesel production and their different fatty acids were determined by gas chromatography coupled with flame ionization detector (GC-FID). These four ILs, as catalysts, were screened and comparatively IL 3-methyl-1-(4-sulfo-butyl)-benzimidazolium trifluoromethanesulfonate [BSMBIM][CF3SO3] was selected for further detailed optimization study. This IL experimental efficiency results supported the Hammett acidity function and COSMO-RS study. The catalyst performance was studied and optimised the different parameters. The catalyst efficiency was studied in one and two-step reactions. [BSMBIM][CF3SO3] as a catalyst showed the esterification of waste cooking oil up to 78.13% in a single step reaction. Potassium hydroxide was used in the second step to trans-esterify the waste cooking oil up to 94.52%. The catalyst was reused for seven times with high-yield production. The obtained biodiesel was characterized by GC, NMR, FTIR, thermogravimetric (TGA) and their physicochemical properties were compared with the already established standards. The kinetic study of this transesterification reaction was evaluated and followed the first-order reaction mechanism.

Kinetic study of thermal degradation of poly(l-lactide) filled with β-zeolite

The thermal features and decomposition kinetics of poly(l-lactide) (PLA) filled with β-zeolite have been studied through differential thermal analysis measurements and thermogravimetric analysis. The experimental data were collected under nitrogen atmosphere with the heating rates of 5–30 K min−1, and the thermal degradation of PLA/β-zeolite composites is observed to mainly occur in the temperature range of 550–675 K. The incorporation of β-zeolite has been found to make the onset thermal decomposition temperature of PLA obviously decrease. With the Flynn–Wall–Ozawa method, the activation energy E a of the composites has been estimated and the β-zeolite composites have required higher E a values for thermal decomposition reaction than pure PLA. The pre-exponential factor ln A can be readily obtained so as to establish the thermal conversion curves if the first-order mechanism is taken. Simulated results reflect that the first-order reaction mechanism has led to certain large deviations at the low conversion levels. By scanning the well-known 27 mechanism functions, the D5 mechanism of Zhuravlev, Lesokhin, Tempelman equation is found to be the most suitable mechanism for the description of the thermal decomposition of PLA and its β-zeolite counterparts. Along with the Flynn–Wall–Ozawa method, the D5 mechanism has performed excellently to establish all the conversion curves over the whole range, resulting in more satisfactory simulation results than the first-order reaction mechanism.

Mechanisms and kinetics studies on the thermal decomposition of micron Poly (methyl methacrylate) and polystyrene

With the development of ultra-fine powder technology, micron polymer materials are widely used, but the thermal decomposition hazard of micron polymers have rarely been studied. In this study, the thermal decomposition of micron Poly (methyl methacrylate) (PMMA) and Polystyrene (PS) with different sizes were studied by thermogravimetry (DTG) technique under nitrogen. Various degradation models including the Friedman method, Kissinger–Akahira–Sunose method and Coats–Redfern method were employed to determine the thermal decomposition mechanisms and kinetics of these polymers. The results showed that the thermal decompositions of micron PMMA and PS under nitrogen atmosphere follow the first-order reaction mechanism. The mean activation energy values of the micron PMMA with sizes of 5 μm, 10 μm and 15 μm were 157 kJ/mol, 170 kJ/mol and 174 kJ/mol, respectively, while values of the micron PS with sizes of 5 μm, 10 μm and 20 μm were 188 kJ/mol, 196 kJ/mol and 206 kJ/mol, respectively. The results indicated that the thermal decomposition stability of the polymer increases with increasing particle size. This work can increase the knowledge of the thermal decomposition of polymers, in particular to understand the influence of particle size on the thermal decomposition characteristics of micron polymers.