Determination of adsorption heats of individual adsorption complex by combination of microcalorimetry and FTIR spectroscopy

Adsorption of CO as a probe molecule on K-FER zeolites differing in Si/Al ratio was investigated. Successful determination of adsorption heats of individual adsorption complexes formed upon adsorption of CO molecules on K-FER zeolites at 300 K by combination of IR spectroscopy with adsorption microcalorimetry is reported. Adsorption heat of bridged carbonyl complexes, where CO molecule interacts with two nearby extraframework K⁺ cations, was experimentally determined for the first time. It was found that bridged complexes on dual cationic sites exhibit adsorption heat of 34.8 kJ mol^?1, whereas monodentate carbonyls on single isolated K⁺ cation exhibit adsorption heat of only 26.2 kJ mol^?1 and adsorption heat of isocarbonyls was 21.5 kJ mol^?1.     

Thermogravimetric analysis of lignocellulosic and microalgae biomasses and their blends during combustion

Thermogravimetric analysis was used to study and compare the combustion of different blends of corn bioresidues with sunflower, rape and algae bioresidues. Non-isothermal thermogravimetric data were used to obtain the combustion kinetics of these bioresidues. This paper reports on the application of the Vyazovkin and Ozawa–Flynn–Wall isoconversional methods for the evaluation of kinetic parameters (energy activation, pre-exponential factor and order of reaction) for the combustion of the biomasses studied. Differences were found in the TG curves in accordance with the proximate analysis results for the cellulose, hemicellulose and lignin content of biomasses. The activation energy obtained from combustion (E ~ 151.6 kJ mol^?1) was lower than that from the blends (similar values were obtained for corn–sunflower, E ~ 160.5 kJ mol^?1 and corn–rape, E ~ 156.9 kJ mol^?1) whereas the activation energy obtained from the microalgae was higher (E ~ 171.5 kJ mol^?1). Both the Vyazovkin and Ozawa–Flynn–Wall methods yielded similar results.     

Kinetic and thermodynamic parameters of volatilization of biodiesel from babassu, palm oil and mineral diesel by thermogravimetric analysis (TG)

The boiling point and volatility are important properties for fuels, as it is for quality control of the industry of petroleum diesel and biofuels. In addition, through the volatility is possible to predict properties, such as vapor pressure, density, latent heat, heat of vaporization, viscosity, and surface tension of biodiesel. From thermogravimetry analysis it is possible to find the kinetic parameters (activation energy, pre-exponential factor, and reaction order), of thermally simulated processes, like volatilization. With the kinetic parameters, it is possible to obtain the thermodynamic parameters by mathematical formula. For the kinetic parameters, the minor values of activation energy were found for mineral diesel (E = 49.38 kJ mol^?1), followed by babassu biodiesel (E = 76.37 kJ mol^?1), and palm biodiesel (E = 87.00 kJ mol^?1). Between the two biofuels studied, the babassu biodiesel has the higher minor value of activation energy. The thermodynamics parameters of babassu biodiesel are, ΔS = ?129.12 J mol^?1 K^?1, ΔH = +80.38 kJ mol^?1 and ΔG = +142.74 kJ mol^?1. For palm biodiesel ΔS = ?119.26 J mol^?1 K^?1, ΔH = + 90.53 kJ mol^?1 and ΔG = +141.21 kJ mol^?1, and for diesel ΔS = ?131.3 J mol^?1 K^?1, ΔH = +53.29 kJ mol^?1 and ΔG = +115.13 kJ mol^?1. The kinetic thermal analysis shows that all E, ΔH, and ΔG values are positive and ΔS values are negative, consequently, all thermodynamic parameters indicate non-spontaneous processes of volatilization for all the fuels studied.     

Study on thermal decomposition and oxidation kinetics of cation exchange resins using non-isothermal TG analysis

Kinetics of two successive thermal decomposition reaction steps of cationic ion exchange resins and oxidation of the first thermal decomposition residue were investigated using a non-isothermal thermogravimetric analysis. Reaction mechanisms and kinetic parameters for three different reaction steps, which were identified from a FTIR gas analysis, were established from an analysis of TG analysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO₃H⁺ from divinylbenzene copolymer was well described by an Avrami–Erofeev type reaction (n = 2, g(α) = [?ln(1 ? α)]^1/2]), and its activation energy was determined to be 46.8 ± 2.8 kJ mol^?1. Thermal decomposition of remaining polymeric materials at temperatures above 400 °C was described by one-dimensional diffusion (g(α) = α ²), and its activation energy was determined to be 49.1 ± 3.1 kJ mol^?1. The oxidation of remaining polymeric materials after thermal dissociation of SO₃H⁺ was described by a phase boundary reaction (contracting volume, g(α) = 1?(1 ? α)^1/3). The activation energy and the order of oxygen power dependency were determined to be 101.3 ± 13.4 and 1.05 ± 0.17 kJ mol^?1, respectively.     

Coordination of extraframework Li+ cation in the MCM-22 and MCM-36 zeolite: FTIR study of CO adsorbed

Nature and population of Li⁺ cationic sites in MCM-22 zeolite and its pillared form (MCM-36) were investigated by means of adsorption of CO as a probe molecule. CO stretching frequency and adsorption heat were measured by FTIR spectroscopy and adsorption microcalorimetry. Intrazeolitic carbonyl complexes on Li⁺ cations in MCM-22 and MCM-36 are characterized by two main vibrational bands at 2,195 and 2,188 cm^?1. Band at higher wavenumbers is ascribed to carbonyls on Li⁺ ions coordinated only to two oxygen atoms at the intersection of 10-ring channels and interacting with CO molecule by energy around 45 kJ mol^?1. Band at 2,188 cm^?1 was assigned to the carbonyls on Li⁺ cations located on top of 5 or 6-rings on the channel walls and coordinated to three or four oxygen atoms, interacting with CO molecule by energy 33–36 kJ mol^?1. Effect of pillaring and layered form of zeolite on nature and population of Li⁺ cationic sites is also discussed, as well as the formation of dicarbonyl complexes.     

Synthesis and thermal behaviors of 1,3-bis(4-aminophenoxy)benzene (TPER) and polyimide based on TPER and pyromellitic dianhydride

1,3-Bis(4-aminophenoxy)benzene (TPER) and poly(amic acid) based on TPER and pyromellitic dianhydride (PMDA) were synthesized. After imidization of the poly(amic acid), polyimide based on TPER and PMDA was obtained. The melting process and the specific heat capacity (C _p) of TPER were examined by DSC and microcalorimetry, respectively. The melting enthalpy, the melting entropy, and the C _p for TPER were obtained. The enthalpy change, the entropy change, and the Gibbs free energy change for TPER were obtained within 283 and 353 K. The thermal decomposition reaction mechanism of the polyimide is classified from the TG–DTG experimental data, and the thermokinetic parameters of the thermal decomposition reaction are E _a = 296.87 kJ mol^?1and log (A/s^?1) = 14.41.     

Thermogravimetric and kinetic analysis of energy crop Jerusalem artichoke using the distributed activation energy model

Jerusalem artichoke has great potential as future feedstock for bioenergy production because of its high tuber yield (up to 90 t ha^?1), appropriate biomass characteristics, low input demand, and positive environmental impact. The pyrolytic and kinetic characteristics of Jerusalem artichoke tubers were analyzed at heating rates of 5, 10, 20 and 30 °C min^?1. TG and DTG curves in an inert (nitrogen) atmosphere suggested that there were three distinct stages of mass loss and the major loss occurs between about 190–380 °C. Heating rate brought a lateral shift toward right in the temperature. And, it not only affects the temperature at which the highest mass loss rate reached, but also affect the maximum rate of mass loss. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics and provided reasonable fits to the experimental data. The activation energy (E) of tubers ranged from 146.40 to 232.45 kJ mol^?1, and the frequency factor (A) changed greatly corresponding to E values at different mass conversion.     

Preparation and Study of Thermal Decomposition Mechanism of Zn(Thr)(AcO)_2·2H_2O

Introduction -Amino acids as additive have a wide application in medicines, foodstuff and cosmetics.1-3 The synthetic methods of amino acid have been reviewed.4,5 The solu-bility property of Zn(AcO)2-Thr-H2O (Thr=Threonine) system at 298.15 K has been investigated by the semimicro-phase equilibrium method, in which the phase region of the complex did not exist.6 The prepara-tion of Zn(Thr)SO4H2O was reported in Ref. 7∶3 times volume of acetone relative to that of water was added into t…     

Thermal studies and spectral characterization of the chelate of bis-(η5-cyclopentadienyl titanium(IV) with salicylidene-4-methylaniline

A new chelate (η⁵-C₅H₅)₂Ti(SB)₂, whereSB=O, N donor Schiff base salicylidene-4-methylaniline, was synthesized. The course of thermal degradation of the chelate was studied by thermogravimetric (TG) and differential thermal analysis (DTA) under dynamic conditions of temperature. The order of the thermal decomposition reaction and energy of activation was calculated from TG curve while from DTA curve the change in enthalpy was calculated. Evaluation of the kinetic parameters was performed by Coats-Redfern as well as Piloyan-Novikova methods which gaven=1, ΔH=1.114 kJ·mol^?1, ΔE=27.01 kJ·mol^?1, ΔS=?340.12 kJ·mol^?1·K^?1 andn=1, ΔH=1.114 kJ·mol^?1, ΔE=20.01 kJ·mol^?1, ΔS=?342.60 kJ·mol^?1·K^?1, respectively. The chelate was also characterized on the basis of different spectral studies viz. conductance, molecular weight, IR, UV-visible and¹H NMR, which enabled to propose an octahedral structure to the chelate.     

Thermogravimetric analysis of walnut shell as pyrolysis feedstock

Thermal degradation behavior and kinetics of a biomass waste material, namely walnut shell, were investigated by using a thermogravimetric analyzer. The desired final temperature of 800 °C was achieved at three different heating rates (2, 10, and 15 °C min^?1) under nitrogen flow (50 mL min^?1). The TG and DTG curves exhibited three distinct zones that can mainly be attributed to removal of water, decomposition of hemicellulose + cellulose, and decomposition of lignin, respectively. The kinetic parameters (activation energy, pre-exponential factor, and reaction order) of active pyrolysis zone were determined by applying Arrhenius, Coats?CRedfern, and Horowitz?CMetzger methods to TG results. The values of activation energies were found to be between 45.6 and 78.4 kJ mol^?1. There was a great agreement between the results of Arrhenius and Coats?CRedfern methods while Horowitz?CMetzger method yielded relatively higher results. The existence of kinetic compensation effect was evident.     

Preparation, characterization and thermal dehydration kinetics of titanate nanotubes

Titanate nanotubes were synthesized utilizing the hydrothermal method using titanium dioxide nanoparticles. The experiments were carried out considering the process as a function of reaction temperature, time, NaOH concentration and the acidity of the washing solution. The formation of titanate nanotubes was shown to be affected strongly by variations in any parameter. The optimum conditions for the synthesis of titanate nanotubes were determined to be a reaction temperature of 190 °C, and a reaction time of 12 h, using 10 M NaOH concentration and the washing solution to have a pH of 5.5. In addition, thermogravimetric analysis (TG/DTG) was used to investigate the thermal behaviour and dehydration kinetics of titanate nanotubes. In order to better understand their thermal behaviour, the thermal analysis of bulk hydrogen trititanate was performed. The values of the apparent activation energies of the first and second dehydration stages for titanate nanotubes were 81.44 ± 15.85 and 82.69 ± 7.46 kJ mol^?1, respectively. The values of the apparent activation energies of the first, second and third dehydration stages for bulk hydrogen trititanate were 115.93 ± 5.40, 137.58 ± 6.47 and 138.97 ± 8.47 kJ mol^?1, respectively.     

Thermal decomposition of sodium propoxides

Sodium alkoxides, namely, sodium n-propoxide and sodium iso-propoxide were synthesized and characterized by various analytical techniques. Thermal decomposition of these compounds was studied under isothermal and non-isothermal conditions using a thermogravimetric analyzer coupled with mass spectrometer. The onset temperatures of decomposition of sodium n-propoxide and sodium iso-propoxide were found to be 590 and 545 K, respectively. These sodium alkoxides form gaseous products of saturated and unsaturated hydrocarbons and leave sodium carbonate, sodium hydroxide, and free carbon as the decomposition residue. Activation energy, E _a, and pre-exponential factor, A, for the decomposition reactions were deduced from the TG data by model-free (iso-conversion) method. The E _a for the decomposition of sodium n-propoxide and sodium iso-propoxide, derived from isothermal experiments are 162.2 ± 3.1 and 141.7 ± 5.3 kJ mol^?1, respectively. The values obtained from the non-isothermal experiments are 147.7 ± 6.8 and 133.6 ± 4.1 kJ mol^?1, respectively, for the decomposition of sodium n-propoxide and sodium iso-propoxide.     

Dibenzofuran and methyldibenzofuran derivatives: assessment of thermochemical data

Thermochemical data of dibenzofuran, a compound of considerable industrial and environmental significance, obtained from experimental calorimetric and computational techniques are reported in this work. The enthalpy of fusion, (19.4 ± 1.0) kJ mol^?1, at the temperature of fusion, (355.52 ± 0.02) K, was determined by differential scanning calorimetry measurements of dibenzofuran. From the standard (p° = 0.1 MPa) molar enthalpies of formation of crystalline dibenzofuran, (?29.2 ± 3.8) kJ mol^?1, and of sublimation, (84.5 ± 1.0) kJ mol^?1, determined at T = 298.15 K by static bomb combustion calorimetry and by vacuum drop microcalorimetry, respectively, it was possible to calculate the enthalpy of formation of the gaseous compound, (55.0 ± 3.9) kJ mol^?1, at the same temperature. The enthalpy of formation in the gaseous phase was also determined from G3(MP2)//B3LYP calculations. The same computational strategy was employed in the calculation of the standard molar enthalpies of formation, at T = 298.15 K, in the gas-phase, of single methylated derivatives of benzofuran and dibenzofuran.     

Kinetic Study on the Exothermic First-stage Decomposition Reaction of 2,4,8,10-Tetranitro-2,4,8,10-tetraaza- spiro[5,5]undecane-3,9-dione

Introduction 2,4,8,10-Tetranitro-2,4,8,10-tetraazaspiro[5,5]udecane- 3,9-dione is a typical cyclourea nitramine (Figure 1). Its crystal density is 1.91 gcm-3. The detonation velocity according to =1.90 gcm-3 is about 8670 ms-1. Its sensitivity to impact is better than that of cyclotrimethy- lenetrinitramine. So it is the potential high explosive. Its preparation,1-3 properties,1-3 hydrolytic behavior4 and electronic structure3 have been reported. In the present work, we report its kinetic pa…     

Study on thermodynamic properties of glyphosate by oxygen-bomb calorimeter and DSC

The combustion enthalpy of glyphosate was determined by XRY-1C oxygen-bomb calorimeter at a constant volume. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be ?1702.19 and ?1478.36 kJ mol^?1, respectively. For testing the reliability of instrument, glycine and naphthalene were used as reference materials by comparing the measured values with the literature values, the absolute error and relative error are 2.58 kJ mol^?1 and 0.26 % for glycine, respectively, and these of naphthalene are 4.08 kJ mol^?1 and 0.08 %, respectively. Moreover, the constant-pressure heat capacities c _p of glyphosate were measured by differential scanning calorimetry in the temperature range 303.15–365.15 K, and the relationship between c _p and temperature was established. These related studies can provide a thermodynamic basis for their further application.     

Phase Chemistry Investigation on Cr(NO3)3‐Met‐H2O System

The solubility property of the ternary of Cr(NO₃)₃‐Met‐H₂O has been investigated in the whole concentration by the phase equilibrium method, and the phase diagram has been constructed. From the phase diagram, the congruently soluble complexes Cr(Met)(NO₃)₃·2H₂O (D) and Cr(Met)₂(NO₃)₃·2H₂O (E) have been prepared and characterized by chemical analysis, elemental analysis, IR and TG‐DTG. Their combustion energies have been determined by a RBC‐type I precision rotating‐bomb calorimeter, and their standard enthalpies of formation, Δf, Hθ_m, have been calculated as (‐1842.01 ± 2.13) kJ·mol^?1 and (‐1136.16 ± 4.45) kJ·mol^?1, respectively.     

Using only the very accurately known experimental enthalpy of hydrogenation of ethylene as a reference standard in the atomization method

Theoretical Gn model chemistries yield slightly different values for the enthalpy of formation of the hydrogen molecule from the constituent protons and electrons. For example, the G3 model yields ?1.92 kJ mol^?1 at 298 K, which differs from zero by an acceptably small amount. However, using this G3 value for a stepwise series of hydrogenations of polyunsaturated molecules multiplies the error, e.g., by five times for the hydrogenation of naphthalene. For polyunsaturates, this can produce errors considerably greater than experimental uncertainties. We calculate enthalpies of hydrogenation by referring the calculated values to the accurately known experimental enthalpy of hydrogenation of ethylene. This approach is simpler than the atomization method that depends on several experimental enthalpies of formation of the constituent atoms of the target molecules. This method yields enthalpies of hydrogenation and of formation in excellent agreement with experiment for many polyunsaturated compounds and lends confidence to results obtained for others, for which no accurate experimental values exist or are disparate, for example azulene. Some new and surprising results are that the formally conjugated triple bonds of cyanoacetylene do not lead to stabilization, but to destabilization by 10.2 kJ mol^?1. The conjugated triple bonds of cyanogen cause thermodynamic destabilization by 47.5 kJ mol^?1. Stabilization by conjugation in acrylonitrile is near zero. The remarkable endothermic monohydrogenation of benzene (25 kJ mol^?1), first noted by Kistiakowsky, is also found in toluene and naphthalene, leading to stability of the reactant relative to the product of ~30 and 22 kJ mol^?1, respectively.     

Preparation and Thermal Chemical Property of Complexes of Zinc Nitrate with Trytophan

IntroductionZincisanessentialtraceelementtothelife .Manydiseasesarousedfromadeficiencyofzincelementhavere ceivedconsiderableattention .L α Aminoacidsarebasicunitsofproteins .L α Trytophanisoneoftheeightspeciesofaminoacidsindispensableforlife ,whichhastobeab sorbedfromfoodbecauseitcannotbesynthesizedinthehumanbody .InviewofthecomplexesofL α trytophanandessentialelementsasaddictiveswidelyusedinsuchfieldsasfoodstuff,medicineandcosmetic ,1 3theyhaveabroadenprospectforapplications .Briefly ,ab…     

A detailed study of isothermal crystallization of As2Se3 undercooled liquid

Isothermal crystallization of an As₂Se₃ undercooled melt was studied by differential scanning calorimetry and described using the classical theory of nucleation and crystal growth. The maximum rate of nucleation and crystal growth was observed to occur at approximately 235 and 350 °C, respectively. The activation energies of nucleation and crystal growth were determined to be ΔE _D = 311 kJ mol^?1 and ΔE* = 104 kJ mol^?1, respectively. The temperature dependencies of both the activation free energy of nucleation, ΔG*, and the critical diameter, r*, were also calculated.     

Synthesis, structure analysis and thermodynamics of [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one)

A novel complex [Ni(H₂O)₄(TO)₂](NO₃)₂·2H₂O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E _a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol^?1, 10^13.80 s^?1; 108.0 kJ mol^?1, 10^23.23 s^?1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ^≠), enthalpy of activation (ΔH ^≠) and the free energy of activation (ΔG ^≠) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being ?1464.55 ± 1.70 kJ mol^?1 by a rotating-bomb calorimeter.