Main Decomposition Products Research Articles

Effects of Frying and Microwave Heating on Decomposition of Benzoyl Peroxide in Flour

ABSTRACTEffects of frying and microwave heating on the decomposition of benzoyl peroxides (BPO) in flour were studied. First, BPO and its main decomposition product, benzoic acid (BA), were extracted from different flour products by ultrasonication in ethanol. Next, three samples of commercial flour, two fried foods, and two microwave foods were analyzed by high performance liquid chromatography (HPLC) and mass spectrum (MS). Results revealed that the BPO content decreased after frying and microwave heating treatments. Furthermore, the existence of biphenyl in fried food was successfully verified by HPLC‐MS. Biphenyl that decomposed from BPO may be one source of toxicity in fried foods. In contrast to fried food, new components made through the special heating module were not found in microwave food.

Modelling the flame synthesis of silica nanoparticles from tetraethoxysilane

This work proposes a kinetic model and an inception pathway for the flame synthesis of silica nanoparticles from tetraethoxysilane (TEOS). The kinetic model for the decomposition of TEOS is developed by generating reactions involving species that were reported in high concentrations at equilibrium. Flux and sensitivity analyses are then performed to identify the main reaction pathways. The parameters for these reactions are systematically fitted to experimental data using low discrepancy (LD) sequences and response surfaces. The main product of TEOS decomposition is deduced to be silicic acid (Si(OH) 4). To increase computational efficiency, the kinetic model has been reduced by determining the level of importance (LOI) of each species and retaining only the important ones. This reduced kinetic model is then coupled to a detailed population balance model using an operator splitting technique. New particle inception and surface growth steps have been incorporated into the particle model in which particles form and grow by the interaction of Si(OH) 4 monomers. Coagulation and sintering of particles are also included in the model and the material dependent sintering parameters have been determined by fitting the model to experimental values of collision and primary particle diameters using LD sequences. The particle size distributions and computer-generated TEM-style images have been generated and good agreement with experiments is observed. The gas-phase reactor composition and the temporal evolution of particle size at different temperatures are also presented.

Catalytic Performance of Zeolites on Urea Thermolysis and Isocyanic Acid Hydrolysis

Urea thermolysis and isocyanic acid hydrolysis over three kinds of zeolites are investigated experimentally and the main decomposition products, NH3 and HNCO, are focused on. The results gained usi...

Thermal decomposition of poly(propylene sebacate) and poly(propylene azelate) biodegradable polyesters: Evaluation of mechanisms using TGA, FTIR and GC/MS

The synthesis, characterization and thermal behavior of two biodegradable aliphatic polyesters poly(propylene azelate) (PPAz) and poly(propylene sebacate) (PPSeb) are described in the present work. The thermal degradation of both polyesters was studied using thermogravimetric analysis (TG) by the determination of their mass losses during heating. From the thermogravimetric curves it can be seen that both polyesters are thermally stable materials since PPAz has its highest decomposition rate at 411.3 while PPSeb at 413.6 °C. From the variation of activation energy ( E) with increasing degree of conversion it is found that the polyester's decomposition proceeds with a complex reaction mechanism with the participation of at least two different mechanisms. To evaluate these mechanisms the TG, FTIR and a combination of TG-gas chromatography–mass spectrometry (TG/GC–MS) methods were used. From mass ions detection of formed decomposition compounds, it was found that the decomposition of both polymers takes place, mainly, through β-hydrogen bond scission and secondarily through α-hydrogen bond scission. The main decomposition products are aldehydes, alcohols, allyl, diallyl, and carboxylic acids.

NaSc3[HPO3]2[HPO2(OH)]6: Synthesis, Crystal Structure, and Thermal Decomposition

AbstractNaSc3[HPO3]2[HPO2(OH)]6 was prepared by use of a phosphorus acid flux route. The crystal structure was determined from single‐crystal X‐ray diffraction data: triclinic, space group P$\bar{1}$ (No. 2), a = 7.4507(11) Å, b = 9.6253(17) Å, c = 9.6141(16) Å, α = 115.798(4)°, β = 101.395(4)°, γ = 101.136(3)°, V = 577.29(16) Å3 and Z = 1. The crystal structure of NaSc3[HPO3]2[HPO2(OH)]6 contains two kinds of phosphate(III) groups: HPO32– and HPO2(OH)–. Phosphate(III)‐tetrahedra, NaO6 and ScO6 octahedra together form a (3,6)‐connected net. During heating hydrogen and water are released and Sc[PO3]3 is formed as the main crystalline decomposition product.

α-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of α-tocopherol. Additionally, the mixtures of α-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. α-Tocopherol inhibited oxidation of the main decomposition product of DMSO, •CH 3 to •OCH 3 but did not prevent the transformation process of N-t-butyl- α-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.

Thermal decomposition of 2-methylpyridine N-oxide: Effect of temperature and influence of phosphotungstic acid as the catalyst

The thermal decomposition of 2-methylpyridine N-oxide was studied at temperatures between 190 °C and 220 °C using an Automatic Pressure Tracking Adiabatic Calorimeter. The effect of the catalyst on the decomposition was evaluated using different amounts of phosphotungstic acid. It was determined that 2-methylpyridine N-oxide decomposes faster with low amounts of catalyst and temperatures above 200 °C. Below 200 °C, the decomposition is very slow. For the cases presented here, the decomposition reaction was accompanied by substantial production of non-condensable gasses, and 2-methylpyridine and pyridine were identified as the main decomposition products.

Photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid in the presence of lanthanide modified TiO 2

Pure and Ln 3+ modified TiO 2 photocatalysts (Ln 3+ = Eu 3+ or Sm 3+ ions) synthesized by a sol–gel method as well as commercially available P25 were applied for photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid. Structure and surface properties of the photocatalysts were characterized by XRD, UV–vis/DR, FT-IR and N 2 adsorption–desorption measurements. The main gaseous products of CH 3COOH decomposition were CH 4 and CO 2. Trace amounts of C 2H 6 and H 2 were also detected in the reaction mixture. Moreover, it was observed that the quantities of all identified gases increased with elongation of irradiation time. The most active photocatalysts towards CH 4 and H 2 generation were Ln 3+/TiO 2 containing 0.05 mol % of Sm and Eu, respectively. The results revealed that the Ln 3+ modification can improve the effectiveness of the photocatalysts compared to pure and commercially available TiO 2 provided that a proper amount of modifying ions is used.

The influence of physico-chemical properties of TiO2 on photocatalytic generation of C1–C3 hydrocarbons and hydrogen from aqueous solution of acetic acid

The present study was focused on the influence of physico-chemical properties of TiO2 on a photocatalytic generation of useful C1–C3 hydrocarbons (mainly methane) and hydrogen from aqueous solution of acetic acid under N2 atmosphere. The photocatalysts applied in the study were prepared from a crude TiO2 obtained by the sulphate technology. The crude TiO2 was calcined at the temperatures of 600, 700 or 800°C in air atmosphere. Moreover, two commercially available photocatalysts, Aeroxide® P25 and VP TiO2 P90 (Evonik, Germany) were also used in the experiments. The photocatalysts were characterized by UV–vis/DR and FTIR spectroscopy, N2 adsorption–desorption at 77K and XRD measurements. The main gaseous products of CH3COOH decomposition were CH4 and CO2. Moreover, small amounts of ethane, propane and hydrogen were detected in the gaseous phase. The main by-products identified in the liquid phase were methanol, ethanol, acetone, acetaldehyde and methyl acetate. The most active photocatalyst towards hydrocarbons and H2 generation was TiO2 calcined at 700°C. The catalyst was composed mainly of anatase (94%) with crystallite size of 32nm and exhibited BET surface area of 30m2/g. After 27h of the process conducted with this catalyst the concentrations of CH4, CO2, C2H6, C3H8 and H2 amounted to 2.92, 2.68, 0.25, 0.08 and 0.22mmol/g of photocatalyst, respectively. It was found that the main parameters responsible for the photoactivity of the photocatalysts were crystallite size of anatase, phase composition and activity towards hydroxyl radicals formation.

The Effect of Doping with the Polymer Metallic Complex Poly Zinc Acrylate on Superconducting Bulk MgB2

In this work, the effect of doping with 5% to 20% poly zinc acrylate (PZA) complexes on MgB2 phase formation was studied. The changes of the lattice parameter and the amount of substituted carbon in the microstructure as well as the critical temperature and the critical current density (J c) of bulk MgB2 have been studied systematically. Both differential thermal analysis–thermogravimetric (DTA–TG) analysis and infrared (IR) spectrometry results show that the PZA was decomposed between 400°C and 600°C, and the main decomposition products were carbonized polymers and ZnO. The lattice parameter a in all PZA-doped MgB2 samples was decreased by different degrees, which indicates gradual substitution of carbon on the boron sites in the MgB2 crystal structure. Compared with the undoped sample, the J c values of all the doped samples were enhanced by about an order of magnitude under high magnetic fields. The J c value of the MgB2 sample with 20% PZA doping sintered at 800°C for 1 h reached 8 kA/cm2 at 5 K and 8 T. Transmission electron microscopy (TEM) images revealed a considerable amount of second-phase particles of ~5 nm size, and a high density of dislocations was observed in the MgB2 grains.

Thermal Decomposition of Decabromodipheny1 Ether During the TempPS Resin in Fire

It is very important for the safety and risk assessment in the course of fire and disposition of flame-retarded polymer to understand the thermal decomposition behavior of decabromodiphenyl ether containing in the polymer at moderate-high temperature. In this paper, the stability and weight loss of flame-retarded high-impact polystyrene resin were studied by thermogravimetric analyzer, the decomposition products of decabromodiphenyl ether at moderate-high temperature range from 250°C to 300°C were investigated by means of a bench-scale pyrolysis reactor and GC/MS, and the decomposition mechanism of decabromodiphenyl ether was discussed. The experimental results showed that polymer could reduce the intial decompostion temperature of decabromodiphenyl ether via acting as hydrogen donor for debrominating reaction, which may cause debrominating partly of decabromodiphenyl ether even at below 300°Cwheras the weight loss speed was accelerated duo to forming antimonous bromide with low boiling point by the reaction of hydrogen bromide and antimony trioxide. The main decomposition products of decabromodiphenyl ether in the high-impact polystyrene resin at about 300°Care various polybrominated diphenyl ethers and its isomers which the number of bromine atoms substituted are not less five.

Ab initio study of the potential energy surface and product branching ratios for the reaction of O(1 D) with CH3 CH2 Br

The potential energy surface of O(1D) + CH3CH2Br reaction has been studied using QCISD(T)/6-311++G(d,p)//MP2/6-311G(d,p) method. The calculations reveal an insertion-elimination reaction mechanism of the title reaction. The insertion process has two possibilities: one is the O(1D) inserting into CBr bond of CH3CH2Br producing one energy-rich intermediate CH3CH2OBr and another is the O(1D) inserting into one of the CH bonds of CH3CH2Br producing two energy-rich intermediates, IM1 and IM2. The three intermediates subsequently decompose to various products. The calculations of the branching ratios of various products formed though the three intermediates have been carried out using RRKM theory at the collision energies of 0, 5, 10, 15, 20, 25, and 30 kcal/mol. CH3CH2O + Br are the main decomposition products of CH3CH2OBr. CH3COH + HBr and CH2CHOH + HBr are the main decomposition products for IM1; CH2CHOH + HBr are the main decomposition products for IM2. As IM1 is more stable and more likely to form than CH3CH2OBr and IM2, CH3COH + HBr and CH2CHOH + HBr are probably the main products of the O(1D) + CH3CH2Br reaction. Our computational results can give insight into reaction mechanism and provide probable explanations for future experiments. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Photocatalytic acetic acid decomposition leading to the production of hydrocarbons and hydrogen on Fe-modified TiO 2

A photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid under N 2 atmosphere is presented. The photocatalysts were prepared from a crude TiO 2 modified with Fe(NO 3) 3 and calcinated at the temperatures of 400–600 °C in argon atmosphere. The main gaseous products of CH 3COOH decomposition were CH 4 and CO 2. Moreover, ethane, propane and hydrogen were also detected. The most active photocatalyst towards CH 4 generation was TiO 2 containing 20 wt.% of Fe calcinated at 500 °C. The optimum loading of this photocatalyst was 1 g/dm 3. After 5 h of the process the amount of CH 4, CO 2, C 2H 6, C 3H 8 and H 2 evolved was 0.458, 0.450, 0.025, 0.003 and 0.013 mmol, respectively. An increase of CH 3COOH concentration from 0.01 to 1 mol/dm 3 resulted in an increase of methane production. A further increase of CH 3COOH concentration up to 10 mol/dm 3 led to a decrease of the process efficiency. The stability of the prepared photocatalysts against photocorrosion was very high. The amount of dissolved Fe did not exceed 0.17 wt.% of the total Fe present in a catalyst sample.

Adsorption and reaction of glycine on the rutile TiO 2(011) single crystal surface

The adsorption and reaction of glycine on the surface of a rutile TiO 2(011) single crystal has been studied by X-ray Photoelectron Spectroscopy (XPS) and Temperature Programmed Desorption (TPD) techniques. Special attention was given to the formation and stability of the zwitterion structure ( +NH 3–CH 2–COO −) in comparison to that of the dissociated structure (NH 2–CH 2–COO −). Both species have been observed on the surface at 300 K. The zwitterion structure was found less stable than the dissociated structure. This is in line with other experimental results related to proline on rutile TiO 2(110) single crystal [13, 14], glycine on rutile TiO 2(110) single crystal [17, 24] and computational results related to glycine on rutile TiO 2(110) single crystal [25]. By 500 K most of the zwitterion structure has been converted to the dissociated one. TPD results indicated that glycine reacts in a similar way to carboxylic acids on this surface with the main decomposition products being ketene (CH 2=C=O). Other masses left unassigned for were also observed during TPD. The most intense being m/ e 55 that might be due to =CH–C(O)N=or C(O)N=CH fragments.

Preparation of Fe-modified photocatalysts and their application for generation of useful hydrocarbons during photocatalytic decomposition of acetic acid

The present study was focused on the photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid under N 2 atmosphere. The photocatalysts applied in the study were prepared from a crude TiO 2 modified with Fe(CH 3COO) 2 and calcinated at the temperatures of 400, 500 or 600 °C in argon atmosphere. In order to compare the results, the commercially available photocatalyst AEROXIDE ® P25 (Evonik, former Degussa, Germany) was also used in the experiments. The photocatalysts were characterized by UV–vis/DR and FTIR spectroscopy, N 2 adsorption–desorption at 77 K and XRD measurements. The crystallite size of anatase was in the range of 7–28 nm and the anatase over rutile ratio was from 82:18 to 95:5. The main gaseous products of CH 3COOH decomposition were CH 4 and CO 2. Moreover, ethane, propane and hydrogen were detected in the gaseous reaction mixtures. The most active photocatalyst towards CH 4 generation was TiO 2 containing 20 wt.% of Fe calcinated at 500 °C. After 27 h of the process conducted with this catalyst the amount of CH 4, CO 2, C 2H 6, C 3H 8 and H 2 evolved was 3.36, 2.97, 0.13, 0.01 and 0.14 mmol/mol CH 3COOH, respectively. It was concluded that photocatalytic decomposition of organic compounds, such as acetic acid, under N 2 atmosphere could be regarded as a method of production of environmentally friendly “photo-biogas”; however, since the yield of hydrocarbons formation was very low, deep and extensive investigations are still necessary in order to improve the efficiency of the process.

Template removal from SAPO-34 crystals and membranes

SAPO-34 membranes had 95–100% higher CO 2 permeances and 9–17% lower CO 2/CH 4 separation selectivities when their structure-directing templates were removed at 673 K in flowing N 2 or under vacuum instead of in flowing air. The average CO 2 permeance was 8.2 ± 2 × 10 −7 mol/(m 2 s Pa) during CO 2/CH 4 separations at 4.6 MPa feed pressure for five membranes whose templates were removed under vacuum. The average CO 2/CH 4 separation selectivity was 55 ± 6. Membranes heated in N 2 or under vacuum were white in color, whereas those heated in air were darker. Membrane preparation was reproducible. Temperature-programmed desorption (TPD) and oxidation (TPO) of SAPO-34 crystals showed that more of the templates decomposed and were removed at lower temperature in inert gas than in air or oxygen. Over 90% of the templates were removed by 773 K during TPD in helium, and ethylene was the main decomposition product. In contrast, only 70% of the templates were removed by 773 K during TPO in air or oxygen, and CO 2 and water were the major products When the SAPO-34 crystals were heated in air or oxygen, some of the template, before it decomposed to form ethylene, was oxidized to more stable compounds that were only removed at higher temperatures.

Study on the Effect of Doping With Poly Zinc Acrylate Complex (PZA) on the Superconducting Properties of Bulk ${\rm MgB}_{2}$

In this work, the effect of doping with 5% to 20% Poly Zinc Acrylate complexes (PZA) on the MgB2 phase formation was studied. The changes of the lattice parameter and the amount of substituted Carbon, of the microstructure as well as the critical current temperature (Tc) and the critical current density (Jc) of bulk MgB2 have been studied systematically. The DTA-TG and IR results show that the PZA was decomposed between 400°C and 600°C and the main decomposition products were carbonized polymers and ZnO. The lattice parameters ? in all PZA doped MgB2 samples were decreased by different degrees, which indicates a gradual substitution of Carbon for the Boron sites in the MgB2 lattice structure. Comparing with the undoped sample, the Jc values of all the doped samples were enhanced for about an order of magnitude under high magnetic fields. The Jc value of MgB2 sample with 20% PZA doping and sintered at 800°C for 1 h reached 0.8 × 104 A/cm2 at 5 k and 8 T. TEM images reveled a considerable amount of second phase particles of ~5 nm size and high density dislocations were observed in MgB2 grains.

Thermal degradation kinetics and decomposition mechanism of two new aliphatic biodegradable polyesters poly(propylene glutarate) and poly(propylene suberate)

The synthesis, characterization and thermal behavior of two biodegradable aliphatic polyesters poly(propylene glutarate) (PPGlu) and poly(propylene suberate) (PPSub) derived from 1,3-propanediol and glutaric and suberic diacid, respectively, have been studied. These polyesters were characterized using several techniques. Thermal degradation of both polyesters was studied by determining theirs mass loss during heating. From the thermogravimetric curves it can be seen that PPSub present a relatively better thermostability than PPGlu since the maximum mass loss occurred at temperatures 411.2 and 409.1 °C, respectively. The activation energy ( E) of degradation was calculated using the isoconversional methods proposed by Ozawa–Flynn–Wall (OFW) and Friedman. From the variation of E with increasing degree of conversion it was found that the polyester decomposition is taking place with a complex reaction mechanism with the participation of at least two different mechanisms. Two combinations of models, nth order and nth order with autocatalysis (Fn–Cn) as well as nth order with autocatalysis in both mechanisms (Cn–Cn) give the better results. Using pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) it is found from mass ions detection that the decomposition of both polymers takes place, mainly, through β-hydrogen bond scission and secondarily by α-hydrogen bond scission. At 410 °C CO 2 is the main gas product of decomposition while allyl, diallyl, carboxylic acids, aldehydes and hydrocarbons are the main liquid products.

Influence of Mg deficiency on crystal structure and superconducting properties inMgB2single crystals

The effects of high-temperature vacuum-annealing induced Mg deficiency in MgB2 single crystals grown under high pressure were investigated. As the annealing temperature was increased from 800 to 975 C, the average Mg content in the MgB2 crystals systematically decreased, while Tc remains essentially unchanged and the superconducting transition slightly broadens from 0.55 K to 1.3 K. The reduction of the superconducting volume fraction was noticeable already after annealing at 875 C. Samples annealed at 975 C are partially decomposed and the Mg site occupancy is decreased to 0.92 from 0.98 in as-grown crystals. Annealing at 1000 C completely destroys superconductivity. X-ray diffraction analysis revealed that the main final product of decomposition is polycrystalline MgB4 and thus the decomposition reaction of MgB2 can be described as 2MgB2(s) = MgB4(s) + Mg(g). First-principles calculations of the Mg1-x(VMg)xB2 electronic structure, within the supercell approach, show a small downshift of the Fermi level. Holes induced by the vacancies go to both sigma and pi bands. These small modifications are not expected to influence Tc, in agreement with observations. The significant reduction of the superconducting volume fraction without noticeable Tc reduction indicates the coexistence, within the same crystal, of superconductive and non-superconductive electronic phases, associated with regions rich and poor in Mg vacancies.

Gamma radiation-induced degradation of p-nitrophenol (PNP) in the presence of hydrogen peroxide (H 2O 2) in aqueous solution

The synergistic effect of gamma radiation with hydrogen peroxide (H 2O 2) for p-nitrophenol (PNP) decomposition in aqueous solution was evaluated. The PNP solution with initial concentration of 50 mg/L was irradiated in the presence of extra H 2O 2 at initial concentration of 0, 20, 40, and 80 mg/L. The experimental results showed that the decomposition of PNP conformed to the pseudo-first-order reaction kinetics under the applied conditions. When initial H 2O 2 concentration was in the range of 0–80 mg/L, higher concentration of H 2O 2 was more effective for the decomposition, mineralization and nitrogen release of PNP. However, the removal of total organic carbon (TOC) and total nitrogen (TN) was not as effective as that of PNP. Ammonia and nitrate were detected as the main inorganic nitrogen products of PNP decomposition without extra H 2O 2, whereas nitrate was considered as a final inorganic nitrogen product with extra H 2O 2 in the initial concentration range of 0–80 mg/L. Major decomposition products, including organic acids were identified by LC/MS and IC. Possible pathways for PNP decomposition by gamma radiation in aqueous solution were proposed.