Preparation of Photodegradable Oligomers Containing Metal–Metal Bonds Using ADMET

ADMET was evaluated as a method for preparing organometallic polymers with metal–metal bonds in the main chain. The Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized, and the X-ray crystal structure is reported. The molecule did not undergo ADMET polymerization with Grubbs’ or Schrock’s catalysts. In a control experiment to test if the Ph₂P(CH₂)₆CH=CH₂ ligand was interfering with the ADMET reaction, the phosphine was reacted with Grubbs’ 2nd generation catalyst. The dimerized metathesis product Ph₂P(CH₂)₆CH=CH(CH₂)₆PPh₂ was obtained with no observed degradation or deactivation of the catalyst. To test the inherent ADMET reactivity of the Ph₂P(CH₂)₆CH=CH₂ ligand when it is bonded to a metal center, the mononuclear cis-Mo(CO)₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized and polymerized using Grubbs’ 2nd generation catalyst. These control experiments suggest that the inability of Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize is not due to electronic effects pertaining to the C=C unit of the Ph₂P(CH₂)₆CH=CH₂ ligand. Accordingly, steric effects are implicated in the inability of the Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize by ADMET.     

One-step purification of ethylene from acetylene and carbon dioxide by ultramicroporous carbons

The one-step adsorptive separation of high-purity ethylene (C₂H₄) from a ternary gas mixture (C₂H₂/C₂H₄/CO₂) is challenging and has not been reported on porous carbons. Herein, we report camphor seeds husk-derived ultramicroporous carbons (CSHs) show high affinities toward acetylene (C₂H₂) and carbon dioxide (CO₂) over C₂H₄. The optimized CSH-2-700 with high heteroatom contents and centered pore size distributions shows high C₂H₂ adsorption capacity (2.24 mmol g⁻¹) and record ideal adsorbed solution theory (IAST) C₂H₂/C₂H₄ selectivity (10.2) among one-step C₂H₄ purification adsorbents. Meanwhile, CSH carbons are the only carbon adsorbents that preferentially adsorb CO₂ over C₂H₄, with a CO₂/C₂H₄ selectivity of 1.9 under ambient conditions. Furthermore, dynamic breakthrough experiments verified its feasibility for one-step C₂H₄ purification from a three-component C₂H₂/C₂H₄/CO₂ gas-mixture.     

Thermal decomposition of ammonium sulphate

The thermal decomposition and vaporisation of ammonium sulphate, (NH₄)₂SO₄, is shown to take place via two distinct sets of reactions. In the first, ammonium pyrosulphate, (NH₄)₂S₂O₇, is the primary condensed phase product: 2(NH₄)₂SO₄ ← (NH₄)₂S₂O₇+2NH₃+H₂O The second stage concerns the decomposition of the pyrosulphate. Ammonia, sulphur dioxide, nitrogen and water are the major products, the dominant reaction being 3(NH₄)₂S₂O₇ ← 2NH₃+6SO₂+2N₂+9H₂O     

Comparison of hot corrosion resistance of Sm2Zr2O7 and (Sm0.5Sc0.5)2Zr2O7 ceramics in Na2SO4+V2O5 molten salt

Sm₂Zr₂O₇ and (Sm_0.5Sc_0.5)₂Zr₂O₇ ceramics were fabricated by a chemical co-precipitation and calcination method, and their hot corrosion behaviors in Na₂SO₄+V₂O₅ molten salt were investigated. Hot corrosion tests were carried at 700 °C, 800 °C and 900 °C for 4 h, and corroded surfaces were investigated using X-ray diffractometer and scanning electron microscopy. The corrosion products of Sm₂Zr₂O₇ ceramics were composed of SmVO₄ and monoclinic-ZrO₂, while those of (Sm_0.5Sc_0.5)₂Zr₂O₇ ceramic consisted of SmVO₄ and Zr₅Sc₂O₁₃. Considering the fact that Zr₅Sc₂O₁₃ is more desirable than monoclinic-ZrO₂ for thermal barrier coating applications, (Sm_0.5Sc_0.5)₂Zr₂O₇ showed better corrosion resistance to Na₂SO₄+V₂O₅ salt than Sm₂Zr₂O₇. The hot corrosion mechanisms of Sm₂Zr₂O₇ and (Sm_0.5Sc_0.5)₂Zr₂O₇ in Na₂SO₄+ V₂O₅ salt were discussed in detail.     

Convenient Modular Syntheses of Fluorous Secondary Phosphines and Selected Derivatives

Reactions of the fluorous primary phosphines R_fn(CH₂)₂PH₂ [R_fn=(CF₂)_n−1CF₃; n=6, 8, 10] and R_fn′CHCH₂ [(n′=6, 8, 10) (1 : 1; THF, reflux) in the presence of AIBN give the title compounds [R_fn(CH₂)₂][R_fn′(CH₂)₂]PH [n/n′=6/6 ( 4 , 55%), 8/8 ( 5 , 58%), 10/10 ( 6 , 53%), 8/6 ( 7 , 52%), 10/8 ( 8 , 51%)] as low-melting white solids on up to 10-g scales. The chiral tertiary phosphine [R_f6(CH₂)₂][R_f8(CH₂)₂][R_f10(CH₂)₂]P ( 9 ) is similarly prepared from 7 and R_f10CHCH₂ in the presence of VAZO (neat, 100 °C; 67%). The reaction of 5 and THF⋅BH₃ yields the phosphine borane 5 ⋅BH₃ (95%). Additions of triphosgene [(CCl₃O)₂CO] to 5 or R_f8(CH₂)₂PH₂ give [R_f8(CH₂)₂]₂PCl or R_f8(CH₂)₂PCl₂, which are characterized in situ. The CF₃C₆F₁₁/toluene partition coefficients of 4 – 9 increase with the number and lengths of the R_fn segments.     

The coloring of geopolymers by the addition of copper compounds

The development of a new coloring technique is desirable to increase the commercial value of geopolymers. Selected copper compounds, i.e. Cu(OH)₂, CuO, Cu₂O, CuCO₃?Cu(OH)₂?H₂O, CuCl₂?2H₂O and CuSO₄?5H₂O, were added to the initial reactants in order to color the geopolymers in the same manner as naturally occurring minerals. When Cu(OH)₂, CuO and Cu₂O were used, these compounds remained in the geopolymer matrix following hardening of the material. On the contrary, CuCO₃?Cu(OH)₂?H₂O, CuCl₂?2H₂O and CuSO₄?5H₂O were not detected in the final products. XAFS analyses were performed to investigate the local structure of copper in the geopolymers produced. The results showed that the copper spectra of geopolymers incorporating Cu(OH)₂, CuO and Cu₂O correspond to those of pure Cu(OH)₂, CuO and Cu₂O, respectively. However, when CuCO₃?Cu(OH)₂?H₂O, CuCl₂?2H₂O and CuSO₄?5H₂O were added, the copper generated spectra similar to that of the mineral chrysocolla ((Cu, Al)₂H₂Si₂O₅(OH)₄?nH₂O) than the respective copper compounds.     

Effect of support material on the catalytic performance of V2O5/P2O5 catalysts for the selective oxidation of but-1-ene and furan to maleic anhydride and its consecutive nonselective oxidation : I. Results of Catalytic Testing

The performance of Al₂O₃- and TiO₂-supported V₂O₅/P2O5 catalysts was studied with respect to activity and selectivity for the oxidation of but-1-ene and furan to maleic anhydride (MA) and its consecutive nonselective oxidation. TiO₂-supported catalysts result in better selectivities for MA both for but-1-ene and furan oxidation. For both the supports MA selectivity was affected by the amount of V₂O₅ and P₂O₅ loading: An increase of the V₂O₅/P₂O₅ loading resulted in improved MA selectivity for the Al₂O₃ support while the effect was opposite in the case of the TiO₂ support. For the oxidation of but-1-ene and furan the activity of the TiO₂-supported catalyst (V₂O₅/P₂O₅/TiO₂, = 5/ 5/90 mass-%) was higher than the Al₂O₃-supported catalyst (V₂O₅/P₂O₅/Al₂O₃ = 5/ 5/90 mass-%) while for the non-selective oxidation of MA to carbon dioxide the Al₂O₃,-supported catalyst was more active than the TiO₂-supported catalyst.     

Synthesis and characterization of calcium aluminate compounds from gehlenite by high-temperature solid-state reaction

The mineral transition mechanism and self-pulverization property of the sintered products in the Ca₂Al₂SiO₇-CaO system were systematically studied using pre-synthesized gehlenite determined by XRD, SEM, FTIR and particle size analyses. The minerals of Ca₁₂Al₁₄O₃₃, CaAl₂O₄, Ca₃SiO₅ and Ca₂SiO₄ are formed by the direct reactions of Ca₂Al₂SiO₇ with CaO. CaAl₂O₄ reacts with CaO to form Ca₁₂Al₁₄O₃₃ or Ca₃Al₂O₆, while Ca₃SiO₅ reacts with Ca₂Al₂SiO₇ to form Ca₂SiO₄ and calcium aluminate compounds. The sintered products mainly contain CaAl₂O₄, Ca₁₂Al₁₄O₃₃ and Ca₂SiO₄ at 1350?°C or above 1500?°C when the molar ratio of CaO to Al₂O₃ is 1.0. Increasing the sintering duration or the CaO consumption promotes the transition of Ca₂Al₂SiO₇ to Ca₂SiO₄ and calcium aluminate compounds when sintered at 1350?°C, which accordingly improves the self-pulverization property of the sintered products. The formed minerals of Ca₁₂Al₁₄O₃₃, CaAl₂O₄ and Ca₂SiO₄ transform into Ca₂Al₂SiO₇ again when the sintering temperature is between 1400?°C and 1450?°C, and the corresponding self-pulverization property of the sintered products deteriorates sharply.     

The effect of relative humidity on CO<Subscript>2</Subscript> capture capacity of potassium-based sorbents

Potassium-based sorbent was prepared by impregnation with potassium carbonate on activated carbon. The role of water and its effects on pretreatment and CO₂ absorption was investigated in a fixed bed reactor. K₂CO₃ could be easily converted into K₂CO₃·1.5H₂O working as an active species by the absorption of water vapor as the following reaction: K₂CO₃+3/2 H₂O→K₂CO₃·1.5H₂O. One mole of K₂CO₃·1.5H₂O absorbed one mole of CO₂ as the following reaction: K₂CO₃·1.5H₂O+CO₂ai2KHCO₃+0.5 H₂O. The K₂CO₃·1.5H₂O phase, however, was easily transformed to the K₂CO₃ phase by thermal desorption even at low temperature under low relative humidity. To enhance CO₂ capture capacity and CO₂ absorption rate, it is very important to maintain the K₂CO₃·1.5H₂O phase worked as an active species, as well as to convert the entire K₂CO₃ to the K₂CO₃·1.5H₂O phase during CO₂ absorption at a temperature range between 50 °C and 70 °C. As a result, the relative humidity plays a very important role in preventing the transformation from K₂CO₃·1.5H₂O to the original phase (K₂CO₃) as well as in producing the K₂CO₃·1.5H₂O from K₂CO₃, during CO₂ absorption between 50 °C and 70 °C.     

Effects of rare-earth oxide doping on the thermal radiation performance of HfO2 coating

In this study, the REO-HfO₂ (REO = Tb₄O₇, Gd₂O₃ and Sm₂O₃) coatings and pure HfO₂ coatings were prepared by atmospheric plasma spraying. The chemical compositions, morphologies, infrared radiation performance and thermal resistances of the coatings were systematically investigated. The experimental results showed that the Tb₄O₇-HfO₂, Gd₂O₃-HfO₂, Sm₂O₃-HfO₂ and pure HfO₂ coatings had infrared emissivity values of 0.863, 0.852, 0.854 and 0.621, respectively, at room temperature. Based on the phase analysis, the higher infrared emissivity of the REO-HfO₂ coatings could be attributed to the fact that the newly formed RE₂Hf₂O₇ (RE = Tb, Gd and Sm) phase, which had a defective fluorite-type structure, and the RE³⁺ ions enhanced the lattice absorption and electron absorption. Additionally, the Tb₄O₇-HfO₂ coating exhibited a relatively higher infrared emissivity than those of the Gd₂O₃-HfO₂ and Sm₂O₃-HfO₂ coating over the wavelength range of 1–15 μm, which was due to the relatively higher vibrational frequency of the TbO bond in RE₂Hf₂O₇ (RE = Tb, Gd and Sm) and the transformation of Tb³⁺ into Tb⁴⁺ in the Tb₄O₇-HfO₂ system. In addition, the REO-HfO₂ ceramic coatings exhibited excellent thermal resistance, which could withstand high-temperature treatment at 1600 °C for at least 50 h without undergoing a phase change and exfoliation, and the infrared emissivity at different temperatures hardly changed after thermal treatment.     

Competitive growth of Al2O3/YAG/ZrO2 eutectic ceramics during directional solidification: Effect of interfacial energy

The microstructure evolution and growth behavior of the Al₂O₃/Y₃Al₅O₁₂(YAG)/ZrO₂ ternary eutectic ceramics during directional solidification were well investigated. During directional solidification of the Al₂O₃/YAG/ZrO₂ ternary eutectic ceramics, {} Al₂O₃ paralleled with {001}ZrO₂ while they did not parallel with {001}YAG at the same time in the competitive growth stage. All of the interfaces parallel to each other finally. The area percentage of the Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are 40.4 ± 0.2% and 30.8 ± 0.1%, respectively, higher than that of the Al₂O₃/YAG (28.8 ± 0.2%). The content of Al₂O₃ and YAG phases are 39.9% and 41.1%, respectively, almost double of that of ZrO₂. The interfaces of Al₂O₃/ZrO₂ and YAG/ZrO₂ are shorter and more dispersed than that of the Al₂O₃/YAG. It was found that the interfacial energy of Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are lower than that of Al₂O₃/YAG. It can be concluded that interfacial energy plays a decisive role in affecting the crystallographic orientation and interfaces distribution in the Al₂O₃/YAG/ZrO₂ eutectic since the interfaces of Al₂O₃/ZrO₂ and YAG/ZrO₂ with lower interfacial energy can be formed more easily during directional solidification. Therefore, the contents of Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are higher. This study can provide theoretical guidance for interface design of multi-phase materials.     

Role of water vapor in oxidative decomposition of calcium sulfide

CaS formed from the CaO sorbent during desulfurization in coal gasifiers has to be converted to CaSO₄ before disposal. CaS is mainly decomposed to CaO and SO₂ by O₂ and then CaO is converted to CaSO₄ by SO₂ and O₂. The role of H₂O in the oxidative decomposition of CaS with O₂ was studied using reagent grade CaS and H₂¹⁸O. The following results were obtained: (1) there is a synergistic effect of H₂O and O₂ on the oxidative decomposition of CaS to CaO and SO₂; (2) H₂O reacts with CaS to form CaO, SO₂ and H₂ in the absence of O₂; (3) the oxidative decomposition of CaS to CaO and SO₂ occurs stepwise; (4) H₂O directly reacts with CaS in the presence of O₂; (5) H₂O plays an important role in the oxidative decomposition of CaS even if the O₂ concentration is high.     

Voltammetric study of the cyanide complexes of osmium—I. The reduction of the cyanide complex of Os(VI) on a platinum rde

Two forms of cyanide complexes of hexavalent osmium were found in alkaline KCN solutions. The initially formed complex, OsO₂(OH)₂(CN)^2?₂, is stable only in solutions with at least a ten-fold excess of OH^? ions over CN^? ions. At higher cyanide concentrations it is converted into the OsO₂(CN)^2?₄ complex. Both these complexes are reduced to tervalent osmium. A more detailed study of complex OsO₂(OH)₂(CN)^2?₂ has shown that it is reduced electrochemically according to the scheme of a consecutive electrochemical reaction.OsO₂(OH)₂(CN)^2?₂ + 2e(k₁,α₁) → Os(IV) + e(k₂,α₂) → Os(OH)₄(CN)^3?₂The values α₁ = 0.65 and α₂ = 0.40 and the potential dependences of constants k₁ and k₂ were determined.     

Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH,Clay Concentration and Mono- and Multivalent Electrolytes

Abstract

In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH₄Cl, NaNO₃, NaClO₄, Na₂SO₄, Na₂CO₃, Na₃PO₄·12H₂O, MgCl₂·6H₂O, CaCl₂·2H₂O, BaCl₂, SrCl₂·6H₂O, CuCl₂·2H₂O, CoCl₂·6H₂O, NiCl₂, AlCl₃, and CrCl₃·6H₂O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺), heavy metal ions (Cu²⁺, Ni²⁺, and Co²⁺) and trivalent cations (Al³⁺ and Cr³⁺) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na⁺, K⁺ and NH₄ ⁺), monovalent anions (Cl^?, NO₃ ^?, and ClO₄ ^?) and multivalent anions (SO₄ ^2?, CO₃ ^2?, and PO₄ ^3?) acted as indifferent ions for these clay particles.     

Behavior of impurity metals in the fusion of magmatic rocks with a mixture of sodium carbonate and calcium oxide

The method of physicochemical simulation is used to calculate the equilibrium compositions of SiO₂-Al₂O₃-(TiO₂)-CaO-MgO-Fe₂O₃-(MnO)-Na₂O-(Cr₂O₃)-(V₂O₅) systems in the temperature range of 1273–1473 K at various ratios of (Na₂CO₃ + CaO): rock. It is shown that the impurity metals are present in fusion products in the form of calcium polytitanate (Ca₃Ti₂O₇), manganese(II, III) oxide (Mn₃O₄), chromium(III) oxide (Cr₂O₃), and calcium orthovanadate (Ca₃V₂O₈).     

Hydrogenation of nitriles with iridium-triphenylphosphine complexes

Reactions of cationic iridium(I)-COD (COD = 1,5-cyclooctadiene) complexes, [Ir(COD)(PhCN)(PPh₃)]ClO₄ (1), [Ir(COD)(PPh₃)₂]ClO₄ (2) and [Ir(COD)(PhCN)₂]ClO₄ (3) with nitriles under H₂ catalytically produce primary, secondary and tertiary amines. Hydrogenation of nitriles (RCN) gives HCl salts of amines (RCH₂NH₂HCl, (RCH₂)₂NH HCl) in CH₂Cl₂. Secondary and tertiary amines seem to be produced by the reactions of RCN with primary and secondary amines, respectively under H₂ in the presence of catalysts. The hydrogenation in the presence of1 and2 is homogeneously catalyzed by soluble iridium-PPh₃ complexes formed in the reactions of1 and2 with H₂ and RCN whereas the hydrogenation in the presence of3 is heterogeneous by metallic iridium powders produced in the reduction of3 by H₂.     

Influence of B-site substituent Ce on thermophysical,oxygen diffusion,and mechanical properties of La2Zr2O7

Pyrochlore-type La₂Zr₂O₇ (LZ) is a promising candidate for high-temperature thermal barrier coatings (TBCs). However, its thermal expansion coefficient and low fracture toughness are not optimal for such application and thus, need to be improved. In this study, we systematically report the effect of CeO₂ addition on phase formation, oxygen-ion diffusion, and thermophysical and mechanical properties of full compositions La₂(Zr₁?_xCe_x)₂O₇ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1). La₂(Zr₁?_xCe_x)₂O₇ exhibits a pyrochlore structure at x ≤ 0.3, while a fluorite structure is observed outside this range. With the increase in CeO₂ content, thermal expansion coefficient and oxygen-ion diffusivity in La₂(Zr₁?_xCe_x)₂O₇ are increased. Oxygen-ion diffusivity of La₂(Zr₁?_xCe_x)₂O₇ is two orders of magnitude less than that of classical 8YSZ. Among La₂(Zr₁?_xCe_x)₂O₇ compounds, La₂(Zr_0.7Ce_0.3)₂O₇ and La₂(Zr_0.5Ce_0.5)₂O₇ exhibit relatively low oxygen diffusivities. The composition La₂(Zr_0.5Ce_0.5)₂O₇ presents the lowest thermal conductivity due to the strongest phonon scattering and also the highest fracture toughness due to the solid-solution toughening. The highest sintering resistance is achieved by the composition La₂(Zr_0.7Ce_0.3)₂O₇ because of its ordered pyrochlore structure and high atomic mass of Ce. Based on these results, the compositions La₂(Zr_0.5Ce_0.5)₂O₇ and La₂(Zr_0.7Ce_0.3)₂O₇ are alternatives for classical 8YSZ for TBC materials operating at ultrahigh temperatures.     

Thermophysical and electrical properties of rare-earth-cerate high-entropy ceramics

A new series of rare-earth-cerate high-entropy ceramics with compositions of (La_0.2Nd_0.2Sm_0.2Gd_0.2Dy_0.2)₂Ce₂O₇ (HEC1), (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Ce₂O₇ (HEC2), (La_0.2Nd_0.2Sm_0.2Yb_0.2Dy_0.2)₂Ce₂O₇ (HEC3), (La_0.2Nd_0.2Yb_0.2Gd_0.2Dy_0.2)₂Ce₂O₇ (HEC4), (La_0.2Yb_0.2Sm_0.2Gd_0.2Dy_0.2)₂Ce₂O₇ (HEC5) as well as a single component of Nd₂Ce₂O₇ are fabricated via sintering the corresponding sol–gel-derived powders at 1600°C for 10 h. HEC1–5 samples exhibit a single-cerate phase with fluorite structure and high configurational entropy. Compared with Nd₂Ce₂O₇, HEC1–5 samples have a lower grain growth rate owing to the sluggish diffusion effect. The chemical compositional uniformity of HEC1–5 as well as Nd₂Ce₂O₇ does not apparently change after annealing at 1500°C for different time intervals (1, 6, 12, and 18 h). Compared with 8YSZ, HEC1–5 samples display the decreased thermal conductivity and increased thermal expansion coefficient. The lattice size disorder parameter of HEC1–5 is negatively related to the thermal conductivity in 26–450°C. Furthermore, HEC1–5 and Nd₂Ce₂O₇ exhibit lower oxygen-ion conductivity, meaning an increased resistance to oxygen diffusion.     

Kinetic study of the pyrolysis of tetrachloroethylene in a hydrogen rich environment

Experiments on pyrolysis of C₂Cl₄ with hydrogen in argon bath gas (C₂Cl₄: H₂: AR=0.5:7:92.5) were performed in a laboratory scale flow reactor, to determine reaction paths and kinetic parameters, plus to observe hydrogen as a source to convert chlorocarbons into hydrocarbons and HCl. The reaction was carried out at 1 atmosphere total pressure in the tubular flow reactor, over temperature ranges from 575 to 850 °C, with average residence times in the range of 0.3 to 1.2 s. The major reaction products were C₂HCl₃, CH₂CCl₂, C₂H₆, C₂H₄ and HCl. Trace intermediates including CH₄, C₂H₂, C₃H₆, C₃H₄, C₄H₈, C₄H₆, C₄H₄, C₂H₃Cl, C₂HCl, trans-CHClCHCl, cis-CHClCHCl C₂Cl₂ and aromatic compounds were found. The equation for overall loss of C₂Cl₄ (k (s⁻¹)) was 1.35×10⁶exp(−27055/RT). This study shows that C₂H₄ became the major product for reaction temperatures higher than 700 °C, and became one of the final products together with HCl.A detailed kinetic mechanism consisting of 202 elementary reactions with 59 species was developed to model the results obtained from the experiments. Sensitivity analyses were performed to rank the significance of each reaction in the mechanism. Modeling and sensitivity analysis revealed that C₂Cl₄+H→C₂HCl₃+Cl, C₂Cl₄+H→C₂Cl₃+Cl, and C₂Cl₄→C₂Cl₃+Cl are the primary reactions for the decomposition of C₂Cl₄.     

Properties of char particles obtained under O2/N2 and O2/CO2 combustion environments

Pulverized coal combustion in O₂/N₂ and O₂/CO₂ environments was investigated with a drop tube furnace. Results present that the reaction rate and burn-out degree of O₂/CO₂ chars (obtained in O₂/CO₂ environments) are lower than that of O₂/N₂ chars (obtained in O₂/N₂ environments) under the same experimental condition. It indicates that a higher O₂ concentration in O₂/CO₂ environment is needed to achieve the similar combustion characteristic to that in O₂/N₂ environment. The main differences between O₂/N₂ and O₂/CO₂ chars rely on the pore structure determined by N₂ adsorption and chemical structure measured by FT-IR. For O₂/CO₂ char, the surface is thick and the pores are compact which contribute to the fragmentation reduction of particles burning in O₂/CO₂ environment. The organic functional group elimination rate from the surface of O₂/CO₂ chars is slower or delayed. The present research results might have important implications for further understanding the intrinsic kinetics of pulverized coal combustion in O₂/CO₂ environment.