Research on the pyrolysis characteristics and mechanisms of waste printed circuit boards at fast and slow heating rates.

The pyrolysis treatment of waste printed circuit boards (WPCBs) shows great potential for sustainable treatment and hazard reduction. In this work, based on thermogravimetry (TG), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and density functional theory (DFT), the thermal weight loss, product distribution, and kinetics of WPCBs pyrolysis were studied by single-step and multi-step pyrolysis at fast (600 °C/min) and slow (10 °C/min) heating rates. The heating rates of TG and Py-GC/MS were the same for each group of experiments.

High-temperature thermal decomposition of iso-octane based on reactive molecular dynamics simulations.

Branched alkanes are the major components of endothermic fuels used for advanced aircrafts. Reactive molecular dynamics (RMD) simulations are carried out to explore the detailed kinetic mechanism for the thermal decomposition of iso-octane widely used as the primary reference fuel of branched alkanes. The RMD calculations indicate that the initial decomposition mechanism of iso-octane is mainly through two pathways: (1) the C - C bond cleavage to produce smaller hydrocarbon radicals and (2) the hydrogen-abstraction reactions by small radicals including •H and •CH.

Initial Thermal Decomposition Mechanism of (NH)C=C(NO)(ONO) Revealed by Double-Hybrid Density Functional Calculations.

This work employs double-hybrid density functionals to re-examine the CO-NO bond dissociation mechanism of nitrite isomer of 1,1-diamino-2,2-dinitro-ethylene (DADNE) into (NH)C=C(NO)O and nitric monoxide (NO). The calculated results confirm that an activated barrier is present in the CO-NO bond dissociation process of (NH)C=C(NO)(ONO). Furthermore, it is proposed that a radical-radical adduct is involved in the exit dissociation path with subsequent dissociation to separate (NH)C=C(NO)O and NO radicals.

Theoretical mechanistic study on the reaction of the methoxymethyl radical with nitrogen dioxide.

Mechanism of the reaction of CHOCH with NO is explored theoretically at the M062X/MG3S and G4 levels. The calculated results indicate two stable association intermediates, CHOCHNO (IM1) and CHOCHONO (IM2), which can be produced by the attack of the nitrogen or oxygen atom of NO to terminal carbon atom of CHOCH without barrier involved. IM2 is found to take trans (IM2a)-cis (IM2b) conversion and isomerization to IM1, with the following stability order IM2a > IM2b > IM1.

Investigation on the Thermal Dissociation of Vinyl Nitrite with a Saddle Point Involved.

Hybrid and double-hybrid density functionals are employed to explore the O-NO bond dissociation mechanism of vinyl nitrite (CH=CHONO) into vinoxy (CH=CHO) and nitric monoxide (NO). In contrast to previous investigations, which point out that the O-NO bond dissociation of vinyl nitrite is barrierless, our computational results clearly reveal that a kinetic barrier (first-order saddle point) in the O-NO bond dissociation is involved. Furthermore, a radical-radical adduct is recommended to be present on the dissociation path.

Computational Study of the Reaction of Dimethyl Ether with Nitric Oxide. Mechanism and Kinetic Modeling.

To probe into the autoignition effect of nitric oxide (NO) on the combustion of dimethyl ether (DME), a detailed mechanism study and kinetic modeling for the reaction of DME with NO, which was considered to be very sensitive to the ignition delay time of DME, have been conducted using computational chemical methods. The CCSD(T)/6-311+G(2df,2p)//B2PLYP/TZVP compound method was employed to obtain the potential energy surface along the reaction coordinate, with the geometries, gradients, and force constants of nonstationary points calculated at the B2PLYP/TZVP theoretical level. The temperature-dependent rate coefficients from 200 to 3000 K were calculated using multistructural canonical variational transition-state theory (MS-CVT) with torsional motions and multidimensional tunneling effects included.

Variational Effect and Anharmonic Torsion on Kinetic Modeling for Initiation Reaction of Dimethyl Ether Combustion.

The reaction of dimethyl ether (DME) with molecular oxygen has been considered to be the dominant initiation pathway for DME combustion compared to the C-O bond fission. This work presents a detailed mechanism and kinetics investigation for the O + DME reaction with theoretical approaches. Using the CCSD(T)/6-311+G(2df,2pd) potential energy surface with the M06-2X/MG3S gradient, Hessian, and geometries, rate constants are evaluated by multistructural canonical variational transition-state theory (MS-CVT) including contributions from hindered rotation and multidimensional tunneling over the temperature range 200-2800 K.

Kinetics for the hydrogen-abstraction of CH4 with NO2.

The detailed mechanism of the NO(2)+CH(4) reaction has been computationally investigated at the M06-2X/MG3S, B3LYP/6-311G(2d,d,p), and MP2/6-311+G(2df,p) levels. The direct dynamics calculations were preformed using canonical transition state theory with tunneling correction and scaled generalized normal-mode frequencies including anharmonic torsion. The calculated results indicate that the NO(2)+CH(4) reaction proceeds by three distinct channels simultaneously, leading to the formation of trans-HONO (1a), cis-HONO (1b), and HNO(2) (1c), and each channel involves the formation of intermediate having lower energy than the final product.

3,3-Dinitro-azetidinium 2-hy-droxy-benzoate.

In the title gem-dinitro-azetidinium 2-hy-droxy-benzoate salt, C(3)H(6)N(3)O(4) (+)·C(7)H(5)O(3) (-), the azetidine ring is virtually planar, with a mean deviation from the plane of 0.0242 Å. The dihedral angle between the two nitro groups is 87.

Preparation, non-isothermal decomposition kinetics, heat capacity and adiabatic time-to-explosion of NTOxDNAZ.

NTOxDNAZ was prepared by mixing 3,3-dinitroazetidine (DNAZ) and 3-nitro-1,2,4-triazol-5-one (NTO) in ethanol solution. The thermal behavior of the title compound was studied under a non-isothermal condition by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by Kissinger method, Ozawa method, the differential method and the integral method.

1-Benzoyl-3,3-dinitro-azetidine.

In the title gem-dinitro-azetidine derivative, C(10)H(9)N(3)O(5), the azetidine ring is almost planar, the maximum value of the endocyclic torsion angle being 0.92 (14)°. The gem-dinitro groups are mutually perpendicular and the dihedral angle between the azetidine and benzene rings is 46.

1-(2,4-Dinitro-phen-yl)-3,3-dinitro-azetidine.

In the title compound, C(9)H(7)N(5)O(8), the dihedral angle between the mean plane of the azetidine ring and that of the benzene ring is 26.1 (1)°; the planes of the two nitro groups of the azetidine ring are aligned at 88.7 (1)°.