Apparent Activation Energy Research Articles

Insights into the selectivity to glyceric acid and lactic acid from biomass: Reaction mechanism and temperature effect

The disclosure of the underlying reaction mechanism on biomass valorization is of significant importance but remains challenging. We here unveil the complicated reaction mechanism on the coproduction of glyceric and lactic acids from biomass (glucose as representative) in the presence of cheap but robust CaO. Interestingly, it was discovered that the selectivity to glyceric acid and lactic acid from glucose was temperature-tunable. Glyceric acid was preferentially produced at ≤70 °C, while lactic acid generation was favorable at >90 °C. Glyceric and lactic acids could be coproduced with almost 1:1 ratio at moderate reaction temperature (∼80 °C). Isotopic tracing experiment verified that at moderate temperature, glyceric acid and equivalent lactic acid were predominantly originated from glyceraldehyde and dihydroxyacetone intermediates (generated after C3-C4 cleavage), respectively. However, both glyceraldehyde and dihydroxyacetone intermediates were transformed mainly towards glyceric acid at temperature ≤70 °C, but predominantly afforded lactic acid at high temperature. Kinetic studies in combination with DFT calculation verified that glyceric acid production from both glyceraldehyde and dihydroxyacetone intermediates showed lower apparent activation energy than that for lactic acid production. This well explained the selectivity to glyceric and lactic acids via temperature control. The generated alkali in CaO aqueous solution was the major active species for glyceric acid production, while both dissolved Ca(OH)2 and solid CaO contributed to lactic acid formation. The insights into the complicated reaction mechanism will provide useful clues in biomass valorization with efficient carbon utilization.

Constructing the combination bridge of aluminum hydride (AlH3) and polyvinylidene fluoride (PVDF) through the self-assembly of dopamine: Improving the stability and ignition properties of AlH3

Surface coating is an important method to solve the poor stability of aluminum hydride (AlH3). To overcome the difficulty of uneven coating of fluorine-containing polymers on the surface of AlH3, this study utilizes the adhesion properties of polydopamine (PDA) to establish a bridge between the oxide layer of AlH3 (Al2O3) and polyvinylidene fluoride (PVDF), so that Polyvinylidene fluoride (PVDF) was uniformly coated on the AlH3 surface, and a dual-core shell structure AlH3@PDA@PVDF composite was successfully prepared. Molecular dynamics simulations reveal significantly higher binding energy per unit area for γ-Al2O3@PDA/PVDF (1.2270 Kcal·mol−1·Å−2) compared to γ-Al2O3/PVDF (0.6644 Kcal·mol−1·Å−2), affirming that PDA can effectively enhance the interfacial interaction between AlH3 and PVDF. The morphology characterization and performance testing of raw AlH3 and AlH3@PDA@PVDF composite were carried out through SEM, XPS, FT-IR, DSC, VST, etc. The results indicate that through the interface modification of AlH3 by PDA, PVDF with a hydrophobic surface can be evenly coated on the surface of AlH3, causing the water contact angle (WCA) of the AlH3@PDA@PVDF composite to increase from 41° for the raw AlH3 to 124°. Furthermore, the total decomposition time of the AlH3@PDA@PVDF composite (2326 min) is improved by 1.8 times than that of the raw sample (1277 min), and its apparent activation energy (117.75 kJ·mol−1) was also higher than that of the raw sample (99.88 kJ·mol−1), indicating that coating with PDA and PVDF can improve the stability of AlH3. Ignition experiments demonstrate that the AlH3@PDA@PVDF composite has superior ignition reaction performance compared with the raw AlH3. Especially, adding a small amount of AlH3@PDA@PVDF composite can also significantly catalyze the thermal decomposition process of ammonium perchlorate (AP), reducing its high-temperature decomposition temperature from 405.37 °C to 352.20 °C.

Effect of copper content on the pyrolysis process of organic components in waste printed circuit boards: Based on experimental and quantum chemical DFT simulations

In recent years, scientists have become increasingly concerned in recycling electronic trash, particularly waste printed circuit boards (WPCBs). Previous research has indicated that the presence of Cu impacts the pyrolysis of WPCBs. However, there may be errors in the experimental results, as printed circuit boards (PCBs) with copper and those without copper are produced differently. For this experiment, we blended copper powder with PCB nonmetallic resin powder in various ratios to create the samples. The apparent kinetics and pyrolysis properties of four resin powders with varying copper concentrations were compared using nonisothermal thermogravimetric analysis (TG) and thermal pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). From the perspective of kinetics, the apparent activation energy of the resin powder in the pyrolysis reaction shows a rise (0.1＜α＜0.2)-stable (0.2＜α＜0.4)-accelerated increase (0.4＜α＜0.8)- decrease (0.8＜α＜0.9) process. After adding copper powder, the apparent activation energy changes more obviously when (0.2＜α＜0.4). In the early stage of the pyrolysis reaction (0.1＜α＜0.6), the apparent activation energy is reduced, but when α=0.8, it is much higher than that of the resin sample without copper. Additionally, it is discovered using thermogravimetric analysis and Py-GC/MS that copper shortens the temperature range of the primary pyrolysis reaction and prevents the creation of compounds containing bromine. This inhibition will raise the temperature at which compounds containing bromine first form, and it will keep rising as the copper level rises. The majority of the circuit board molecules have lower bond energies when copper is present, according to calculations performed using the gaussian09 software, which promotes the pyrolysis reaction.

Effect of sulfur-containing groups on the susceptibility to spontaneous combustion of corrosion products in oil tanks

Sulfur-containing groups (SCG) may be an essential factor influencing the spontaneous combustion of oil tank corrosion products and triggering fire and explosion accidents. The effect of three SCG on the spontaneous combustion susceptibility of model compounds of tank corrosion products (MCTCP) were investigated. The results show that SCG causes the surface of MCTCP to produce cracks and become rough, which adsorbs more oxygen and SCG, enhancing its spontaneous combustion susceptibility. After the SCG addition, the MCTCP thermal susceptibility partial indicator values decreased. The apparent activation energy and the flammable volatile compound release temperature decreased significantly, which increased the spontaneous combustion susceptibility of MCTCP. In addition, SCG also increased the number of exothermic peaks in the self-ignition process of MCTCP. The exothermic peaks partly came from the oxidation of SCG, and the heat generated by the oxidation of SCG increased the spontaneous combustion susceptibility. Therefore, SCG may affect the spontaneous combustion susceptibility through three pathways: changing the microform and structure of MCTCP, thermal susceptibility parameters, and oxidative exothermic properties. The work assists in deepening the theory of the mechanism and influence factors of spontaneous combustion of corrosion products in oil tanks, and provide guidance for the prevention of such accidents.

Multistep kinetics of the thermal dehydration/decomposition of metakaolin-based geopolymer paste

This study investigated the kinetics of the multistep thermal dehydration/decomposition of the metakaolin-based geopolymer paste. The component two reaction steps were characterized by the evolution of water vapor and the simultaneous evolution of water vapor and CO2, respectively. In a stream of dry N2, the kinetics of the first and second reaction steps were characterized by the apparent activation energy (Ea) values of 92 and 166 kJ mol−1, respectively. Both reaction steps exhibited a diffusion-controlled rate behavior. In a stream of wet N2, the mass loss curves systematically shifted to higher temperatures with an increase in the water vapor pressure (p(H2O)). The first reaction step was significantly influenced by p(H2O), and the apparent Ea increased to 175 kJ mol−1 at p(H2O) = 11.4 kPa. The second reaction step was less sensitive to the atmospheric water vapor, as characterized by its Ea of ∼165 kJ mol−1, irrespective of the p(H2O).

Study on the curing characteristics and properties of phthalonitrile resin cured with organic guanidine

Bisphenol A-based phthalonitrile resin was synthesized by nucleophilic substitution reaction from bisphenol A and 4-nitrophthalonitrile, and then the obtained resin was cured with sulfaguanidine as a novel curing agent. The curing characteristics, kinetics, thermal stability and dynamic mechanical property were studied by standard thermal analysis techniques including DSC, TGA, and DMA. The peak temperature of exothermic peak ( Tp) and apparent activation energy ( Ea) of sulfaguanidine cured phthalonitrile resin were 263.20°C and 76.6 kJ·mol−1 respectively, much lower than those of traditional aromatic diamine cured resin. Moreover, the resin cured by sulfaguanidine showed excellent thermomechanical properties and thermal stability. The glass transition temperature ( Tg) was 284.8°C, the initial thermal decomposition temperature ( Td,5%) was 439.6°C, and the char yield at 800°C was 62.1% in nitrogen atmosphere. To sum up, organic guanidine cured phthalonitrile resin exhibits excellent curing characteristics (low Tp and Ea) and high thermal properties, which provides a promising approach to preparing phthalonitrile resin with high comprehensive performance.

Thermo-osmotic coefficients in membrane distillation: Experiments and theory for three types of membranes

The thermo-osmotic coefficient of a porous medium is the ratio of the mass flow rate and the temperature difference that drives the flow. Thermo-osmotic coefficients of the Millipore DuraPore HVHP, GVHP and VVHP membranes have been measured using a new apparatus designed to provide accurate mass flux measurements with tightly controlled temperatures, pressures, and compositions on the feed and distillate side. To properly analyze the experimental data, recommendations on data reduction procedures anchored in non-equilibrium thermodynamics are discussed. An expression is presented for the apparent energy of activation of the transport process in terms of the derivative of the thermo-osmotic coefficient with respect to the inverse mean temperature. The expression is shown to accurately predict the temperature dependence of the thermo-osmotic coefficients from experiments. The expression is next used to explain observations in similar porous systems from the literature. Based on this, an optimization scheme to find the optimal mean pore radius to maximize the power density of a pressure-retarded membrane distillation (PRMD) process is presented. For membranes with properties similar to the Durapore XXHP series membranes, the optimal pore radius is found to be between 1 and 10 nm. It is shown that the power density can benefit greatly from a narrow pore size distribution and from membrane surface treatments that increase the liquid-solid contact angle, potentially exceeding a benchmark minimum power density of 5 W/m2 (set for the feasibility of pressure-retarded osmosis). An assessment of the second law efficiency of the PRMD process is also presented. A critical part of the process is due to the inevitably smaller water flux through smaller pores, required to maintain a high pressure difference and a feasible power density. This can only be alleviated by increasing the temperature difference across the membrane. We conclude that membranes designed for the PRMD process need increased overall thermal resistance to enhance performance.

Efficient Hydrogen Evolution from Dimethylamine Borane, Ammonia Borane and Sodium Borohydride Catalyzed by Ruthenium and Platinum Nanoparticles Stabilized by an Amine Modified Polymer Immobilized Ionic Liquid: a Comparative Study

Platinum and ruthenium nanoparticles stabilised by an amine modified polymer immobilised ionic liquid (MNP@NH2-PEGPIILS, M = Pt, Ru) catalyse the hydrolytic liberation of hydrogen from dimethylamine borane (DMAB), ammonia borane (AB) and NaBH4 under mild conditions. While RuNP@NH2-PEGPIILS and PtNP@NH2-PEGPIILS catalyse the hydrolytic evolution of hydrogen from NaBH4 with comparable initial TOFs of 6,250 molesH2.molcat−1.h−1 and 5,900 molesH2.molcat−1.h−1, respectively, based on the total metal content, RuNP@NH2-PEGPIILS is a markedly more efficient catalyst for the dehydrogenation of DMAB and AB than its platinum counterpart, as RuNP@NH2-PEGPIILS gave initial TOFs of 8,300 molesH2.molcat−1.h−1 and 21,200 molesH2.molcat−1.h−1, respectively, compared with 3,050 molesH2.molcat−1.h−1 and 8,500 molesH2.molcat−1.h−1, respectively, for PtNP@NH2-PEGPIILS. Gratifyingly, for each substrate tested RuNP@NH2-PEGPIILS and PtNP@NH2-PEGPIILS were markedly more active than commercial 5wt % Ru/C and 5wt% Pt/C, respectively. The apparent activation energies of 55.7 kJ mol−1 and 27.9 kJ mol−1 for the catalytic hydrolysis of DMAB and AB, respectively, with RuNP@NH2-PEGPIILS are significantly lower than the respective activation energies of 74.6 kJ mol−1 and 35.7 kJ mol−1 for its platinum counterpart, commensurate with the markedly higher initial rates obtained with the RuNPs. In comparison, the apparent activation energies of 44.1 kJ mol−1 and 46.5 kJ mol−1, for the hydrolysis NaBH4 reflect the similar initial TOFs obtained for both catalysts. The difference in apparent activation energies for the hydrolysis of DMAB compared with AB also reflect the higher rates of hydrolysis for the latter. Stability and reuse studies revealed that RuNP@NH2-PEGPIILS recycled efficiently as high conversions for the hydrolysis of DMAB were maintained across five runs with the catalyst retaining 97% of its activity.Graphical

Hydration kinetics and apparent activation energy of cement pastes containing high silica fume content at lower curing temperature

To promote the application of silica fume (SF) in civil engineering in cold regions, relative influences from SF content and low temperature environment on the early hydration kinetics of composite cement pastes were evaluated based on the isothermal calorimetric method. The effect of high SF content on the apparent activation energy (Ea) of Portland cement and the filler effect (via the index of area multiplier) of SF on the hydration parameters was also analyzed. The results showed that the intensity of the shoulder peak (Al peak) of the hydration kinetic curve (heat flow curve) gradually grew as the SF content increased, and the double-peak phenomenon was gradually clear. The heat flow peak is delayed and lowered with the decreasing curing temperature, while the final time of the induction stage and the duration of the acceleration stage are delayed. Moreover, the duration of the acceleration stage was slightly extended with the increase of SF content. The full-width at half-maximum (FWHM) value of the heat flow curves dropped as the SF content and curing temperature increased. The low temperature environment and the inclusion of SF inhibited the growth in early hydration degree. The higher SF content mitigated the impact of low temperature on the hydration time parameter τ. The apparent Ea results also indicated that the SF reduced the temperature sensitivity of the hydration process of the composite cement pastes, which might contribute to the development of the hydration reaction at low temperatures. The AM (Area Multiplier) factor increased approximately linearly with increasing SF replacement levels. Apparent Ea decreased linearly with increasing AM, which may be attributed to a further reduction in the diffusion-controlled hydration rate of composite cement pastes with larger AM.

Densification mechanism, microstructure, and thermionic emission property at the low temperature of spark plasma sintered (LaBa)B6–ZrB2 composite

The development of a high-power and long-life thermionic ceramic cathode poses significant challenges, namely the need for high electron emission capacity at low temperature and excellent machinability. In this paper, the first-principles method was used to obtain the (La0.5Ba0.5)B6 with the lowest work function, and (La0.5Ba0.5)B6–ZrB2 composite with high relative density of 98.08 % was prepared by spark plasma sintering (SPS) at T = 1800 °C, under which the densification mechanism transformed from the particle rearrangement into the grain boundary diffusion, and the corresponding apparent activation energies were 282.75 kJ/mol and 466.54 kJ/mol, respectively. The maximum current density of 12.93 A/cm2 at T = 1500 °C of the composite was higher than that of 11.71A/cm2 at T = 1600 °C of LaB6, which can be attributed to the high Fermi level and weak electronic constraints of (La0.5Ba0.5)B6. The practical work function distribution (PWFD) of 0.36 eV indicated the composite had excellent emission uniformity.

Concentrated solar CO2 reduction in H2O vapour with >1% energy conversion efficiency

H2O dissociation plays a crucial role in solar-driven catalytic CO2 methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (Vo) rich CeO2 catalyst with single-atom Ni anchored around its surface Vo sites by replacing Ce atoms to promote H2O dissociation and achieve effective photothermal CO2 reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH4 production and prevents Vo from depletion. The defects coordinated with single-atom Ni, significantly promote the capture of charges and local phonons at the Ni d-impurity orbitals, thereby inducing more effective H2O activation. The catalyst presents a CH4 yield of 192.75 µmol/cm2/h, with a solar-to-chemical efficiency of 1.14% and a selectivity ~100%. The mechanistic insights uncovered in this study should help further the development of H2O-activating catalysts for CO2 reduction and thereby expedite the practical utilization of solar-to-chemical technologies.

The effects of the contents of modified‐diatomite on the properties of modified‐diatomite/epoxy resin composites

AbstractExternal plasticization is one of the effective ways to toughen epoxy resins. In this study, an inorganic filler (EMD) was prepared by chemical modification of diatomite and was used to fill epoxy resin matrix. The effects of different amounts (5%, 10%, 15%, and 20%) of raw diatomite (RD) and modified‐diatomite (EMD) on the mechanical and thermal properties of epoxy resin composites were studied. The mechanical results showed that the impact strength, tensile strength, and bending strength of EMD/EP were higher than those of RD/EP. The impact strength of EMD‐15/EP reached 5.39 KJ/m2, which was 36.8% higher than that of RD‐15/EP. Thermogravimetric analysis showed that the thermal stability of EMD/EP was better than that of RD/EP. The results of DMA show that the glass transition temperature of EMD/EP was lower than that of RD/EP. Non‐isothermal differential scanning calorimetry study showed that the apparent activation energy of EMD‐15/EP was much lower than that of RD‐15/EP, which proved that EMD could promote the curing of epoxy resin. The Malek method was used to determine that both the RD‐15/EP and EMD‐15/EP curing systems were autocatalytic (Šesták–Berggren) models.

Coupling geometric and electronic engineering over RuNi ultrafine alloys for fast boosting hydrolytic dehydrogenation of NH3BH3

Developing a suitable catalyst for ammonia borane (AB, NH3BH3) hydrolysis and clarifying the catalytic mechanism are essential and challenging at present. In this work, RuNi nanoalloys are supported on an N/O co-coped glucose-derived carbon (g-C) with the adsorption-NaBH4 reduction method. Attributed to the particular geometric and anchoring effects, as well as the improved hydrophilicity of the multi-level porous support, the RuNi alloys are highly and firmly confined in the framework of g-C. Specifically, the optimal Ru0.25Ni0.75@g-C with an average alloy particle size of 1.4 nm exhibits pleasurable specific hydrogen evolution rate (437,990 mL min−1 gRu−1) and turnover frequency (1612.37 min−1) in NaOH aqueous solution (1.5 M) at 303 K, superior to the corresponding monometallic counterparts (i.e., Ni@g-C and Ru@g-C) and many previous results. In addition, apart from satisfactory durability, the optimal alloy catalyst delivers an encouraging apparent activation energy (28.1 kJ mol−1). Our work not only explains the geometric and electronic effects on the catalytic performance but also offers a promising catalyst for hydrogen release from liquid-phase AB.

Well-designed flame retardants for epoxy resin composites that simultaneously improve heat resistance, mechanical properties and fire safety

Epoxy resin (EP) flammability severely limits its application in some industrial fields, while flame retardant epoxy resin (FREP) often suffers from the problem of not being able to balance flame retardant properties with mechanical properties. To solve the problem, in this work, HDP, a reactive flame retardant was succeeded in synthesizing by the one-pot method using protocatechuic aldehyde (PH), 2,4-diamino-6-phenyl-1,3,5-triazine (DPT), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as reactive monomers, was used to improve the flame retardancy of EP. And evaluated the effect of HDP on the curing reaction, heat resistance and mechanical property of EP. The introduced of four phenolic hydroxyl groups and two secondary amine groups enhanced the compatibility of the flame retardant HDP in EP and improved process performance. The apparent activation energy (Ec) was reduced by 8.1 %, facilitating the curing of EP/DDM. When 5 wt% of HDP (with only 0.36 wt% phosphorus content) was added to EP, the flexural strength and modulus of FREP increased by 21.0 % and 14.9 %, respectively, and the Tg increased by 9.0 % compared to EP. Cone calorimeter test (CCT) data showed that compared to EP, samples of EP/HDP-5 showed a 14.5 % and 21.6 % reduction in total heat release (THR) and total smoke production (TSP), respectively, and a 13.7 % increase in coke yield (CY). EP/HDP-5 has a high limited oxygen index (32.5 %) and passes the UL-94 V-0 classification. The excellent char formation and flame retardancy was owed to the dual role of the condensed and gas phases of FREP in the combustion process.

Microwave-assisted atmospheric alkaline leaching process and leaching kinetics of rare earth melt electrolysis slag

This study focuses on the difficulty of converting fluorinated rare earth elements into hydroxylated rare earth elements in rare earth melt electrolysis slag (RMES) and proposes the use of a microwave-assisted atmospheric alkaline leaching method for the treatment of RMES. The leaching behavior of RMES under microwave-assisted atmospheric alkaline leaching was studied, and the optimal reaction conditions were determined. Under the conditions of a reaction temperature of 150 °C, initial NaOH concentration of 60 %, NaOH-to-slag mass ratio of 4:1, microwave power of 700 W, reaction time of 120 min, and stirring speed of 300 r/min, the conversion rate of fluorinated rare earths reached 99.17 %. The apparent rate equation of the microwave-assisted atmospheric alkaline leaching process was obtained by leaching kinetic analysis, and the apparent activation energy under this process was calculated to be 54.872 kJ/mol, which was 12.458 kJ/mol lower than that achieved when conventional heating was used for leaching (67.33 kJ/mol).

Carbon dots decorated cadmium sulfide nanomaterials for boosting photocatalytic activity for ciprofloxacin degradation

This study investigates the utilization of carbon dots (CDs) from neem leaves (Azadirachta indica) decorated onto cadmium sulfide (CdS) for the photocatalytic degradation of ciprofloxacin. A comparative study of ciprofloxacin degradation with pristine CdS and CD decorated CdS demonstrated high degradation of ∼ 75 % with CD/CdS when compared to bare CdS (∼68 %). Process optimization studies were further carried out with CD/CdS catalysts at different solution pH (4–10), feed concentrations (10–50 mg/L), catalyst loadings (25–125 mg/L), temperatures (10 – 30 °C), and lamp power (25, 50, 250 W and sunlight). Higher temperatures, combined with a solution pH of 7 and catalyst loading of 100 mg/L favored the enhanced degradation of 20 mg/L of ciprofloxacin. The ciprofloxacin degradation rate increased linearly with temperature with an apparent activation energy of 27 kJ mol−1. The CD/CdS photocatalyst demonstrated maximum degradation rates with higher lamp powers while it also showed remarkable performance under natural sunlight achieving the same degradation within 3 h.

Sustainable strategies for recovering metallic copper from waste printed circuit boards: Clean leaching and micro-nano copper powder preparation

Recovery and utilization of valuable metals from waste printed circuit boards (WPCBs) have the dual significance of alleviating resource shortages and protecting the ecological environment. This study focuses on the feasibility analysis of copper in WPCBs for preparing micro-nano copper powders by clean leaching and chemical reduction processes. Firstly, the effect of temperature and other parameters on copper leaching rate in glycine-hydrogen peroxide (Gly-H2O2), ammonia-ammonium chloride (NH3·H2O-NH4Cl) leaching systems with sulfuric acid-hydrogen peroxide (H2SO4-H2O2) system as control group were emphasized. Subsequently, the leaching characteristics of copper concentrate particles were analyzed by leaching kinetics to elucidate the leaching mechanism and apparent activation energy of copper. Finally, the micro-nano copper powders were prepared using ascorbic acid and sodium borohydride reduction system with different copper leach solutions as precursors. The micro-nano copper morphology and phase compositions were analyzed by SEM and XRD. The results show that both the Gly-H2O2 and NH3·H2O-NH4Cl system can replace the H2SO4-H2O2 system to achieve efficient leaching of copper. Increasing temperature can significantly enhance the copper leaching rate. When the temperature was increased from 15 °C to 45 °C, the maximum copper leaching rate in the three systems increased from 58.13 %,71.26 %,78.26 % to 90.36 %,91.21 %,92.87 %, at − 0.074 mm for 40 min. The Avrami model accurately describes the leaching behavior of copper concentrate particles, and the copper leaching process is dominated by chemical reaction control. SEM and XRD results show that micro-nano copper particles of hundreds of nanometers are successfully prepared by both reduction systems.

Influence of composite chloride salt retardant on the characteristics of coal spontaneous combustion and comprehensive evaluation methodology

ABSTRACT In this study, we aimed to improve the efficacy and longevity of single inhibitors. NaCl, CaCl2, MgCl2, and layered double hydroxides (LDHs) were selected as the inhibitory components for experimental study. The impact of the composite inhibitors on the spontaneous combustion characteristics of the coal was studied through temperature programmed experiment, thermal analysis experiments, thermogravimetric mass spectrometry and entropy weight method, and the optimal inhibitor was determined. The findings indicate that the apparent activation energy (E a ) of the coal sample, with the addition of inhibitors during the oxidation stage, was improved. E a of MgCl2 +1.0 LDHs + Coal was the highest (127.28 kJ/mol), i.e. 35.99 kJ/mol higher than that of the original coal. The inclusion of the inhibitor increased the characteristic ignition temperatures of the coal samples compared with the original coal. The highest ignition temperature was observed for MgCl2 +0.5 LDHs + Coal, reaching (323.98°C), i.e. 11.42°C higher than that of the original coal. The addition of inhibitors significantly inhibited the production of CO. Among the three chloride salts, MgCl2 exhibited the strongest inhibitory effect on CO production. According to the entropy weight method, MgCl2 +0.5 LDHs showed the best inhibitory effect. The results show that the composite halogen inhibitor can effectively inhibit the spontaneous combustion of coal.

Thermal Decomposition Mechanism of P(DAC-AM) with Serial Cationicity and Intrinsic Viscosity.

The thermal decomposition of the thermodynamic, kinetic and mechanisms of copolymer P(DAC-AM) samples with serial cationicity and intrinsic viscosity ([η]), and the control samples of homopolymer PAM and PDAC, were studied and analyzed using TG, DSC, FTIR. The results of the thermal decomposition thermodynamics confirmed that the thermal decomposition processes of the serial P(DAC-AM) samples and the two control samples could be divided into two stages. It was found that the processes of the copolymer P(DAC-AM) samples were not a simple superposition of those of homopolymers, whose monomers had composed the unit structures of the copolymer, but there were interactions between the two suspension groups. The results of thermal decomposition kinetics showed that the apparent activation energy (E) of the thermal decomposition process of all polymer samples had different varying trends in the terms of weight-loss rate (α). The reaction order (n) of the thermal decomposition of P(DAC-AM) in Stage I and II was close to 1, but in the former and the latter it tended to be 2 and 0.5, respectively. Finally, the thermal decomposition mechanism of copolymer P(DAC-AM) samples was discussed. The above research could not only fill in the knowledge vacancy of the thermal decomposition of the thermodynamic, kinetic and mechanisms of P(DAC-AM), but could also lay a foundation for the study of thermal decomposition mechanisms of the other types of polymers, including cationic polymers.

Efficient calcium sulfite oxidation treatment by a highly active iron-manganese bimetallic metal-organic frameworks (MOFs)

Calcium sulfite (CaSO3) oxidation is the key step in the resource utilization of flue gas desulfurization (FGD) ash waste. However, under natural conditions the oxidation rate of CaSO3 is very low, limiting its conversion into calcium sulfate, an acceptable product for construction material. This study was devoted to the investigation of the synthesis and performance of a bimetallic MOFs with potential catalytic activity, namely, Fe/Mn(BDC)(DMF,F) catalysts. A combination of techniques including SEM, EDS, XRD, FT-IR, etc. were used to characterize the catalysts. The excellent catalytic performance examined in a gas-liquid-solid three-phase oxidation system are due to the special flexible respiratory architecture and homogeneous distribution of active sites, which allows the reactants to fully contact with the catalyst. Mn incorporated in the backbone of the metal-organic framework significantly enriches the catalytic active species that participate in a radical chain reaction with activated SO32- as ·SO3-, which in turn generates the key radical ·SO5- that reacts with SO32- to form SO42-. In the presence of Fe/Mn(BDC)(DMF, F)-13, the oxidation ratio of CaSO3 could reach 90.71%, which is more than 30-fold compared to non-catalytic oxidation and almost 5 times the effects of the single metal Fe(BDC)(DMF, F) catalyst. In addition, the study of kinetics shows that the oxidation rate of Fe/Mn(BDC)(DMF,F)-13 can reach 0.042 mmol·L-1·s-1 with an apparent activation energy of 10.86 kJ/mol. The oxidation rate is mainly affected by reaction temperature, pH value, catalyst concentration, and air flow rate. This study provides a potentially sustainable way for utilization of CaSO3-containing desulfurization ash.