Experimental and theoretical investigation of HC5N adsorption on amorphous ice surface: simulation of the interstellar chemistry

HC 5N adsorbed on amorphous water ice at 10 K presents an interaction with the ice surface and induces the restructuring of the ice amorphous bulk. Warming up the sample induces the HC 5N desorption from the H 2O ice film, between 120 and 160 K, and the associated desorption energy is 90 kJ/mol. This value is in good agreement with that calculated E d (80 kJ/mol) and gives evidence that the amorphous ice surface is essentially dynamic. From theoretical calculations, it is shown that the HC 5N moiety presents a curvature and is no more linear and stabilized by two strong N...H bonds (2.09 and 2.29 A) and one H...O bond (1.84 A).     

Bonding and molecular motions in the 1:1 molecular complexes of 1,4-diazabicyclo[2.2.2]octane with tetrahalomethane as studied by means of NQR

NQR spectra were observed in the complexes of 1,4-diazabicyclo[2.2.2]octane (DABCO) with tetrachloromethane and tetrabromomethane at various temperatures. A phase transition was found at 319 K for DABCO·CBr₄. From spin-lattice relaxation times of nitrogen-14 in DABCO·CBr₄, the activation energy of the reorientation of DABCO about the NN axis was calculated to be 18.3 kJ/mol which agrees with the value obtained from the second moment of proton NMR spectra. The bond nature is discussed using the Townes-Dailey treatment.     

H(2)O Outgassing Properties of Fumed and Precipitated Silica Particles by Temperature-Programmed Desorption

Temperature-programmed desorption was performed at temperatures up to 850 K on as-received fumed and precipitated silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 38–61 kJ/mol. However, the activation energies of desorption for chemisorbed water varied from 80 to >247 kJ/mol for fumed silica, Cab-O-Sil-M-7D, and 96 to 155 kJ/mol for precipitated silica, Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>126 kJ/mol) will not escape silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (80–109 kJ/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies <126 kJ/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1–0.4 wt% of water in silica-reinforced polysiloxane formulations containing 21% Cab-O-Sil-M-7D and 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that the adsorbed H₂O and the Si–OH bonds on the silica surfaces are the major contributors to water outgassing from these types of silica-filled polymers.     

钇与2-(4'-氯-2'-膦酰基-苯偶氮)-7-(2',6'-二溴-4'-氯-苯偶氮)-1,8-二羟基-3,6-萘二磺酸配位反应驰豫动力学研究

用跳浓驰豫法测定不同温度下的驰豫时间τ.根据拟定的机理导出了1/τ的函数表达式为1/τ＝k[H₆R]₀/[H₃⁺O]-(6k/ε[H₃⁺O]₀)A_∞,获得表观速率常数k及摩尔吸光系数ε,表观活化能为52.82KJ/mol,活化焓为50.34kJ/mol,活化熵在278K～298K范围内为负值,配合物稳定常数lgK'.为13.84。与孤立变量法、比尔法、平衡移动法获得的结果吻合.     

生物质秸秆热重分析及几种动力学模型结果比较

利用热重分析在不同升温速率和氮气气氛下对两种生物质（玉米秸秆和稻秆）的热失重行为进行了研究。根据热重实验数据，采用四种利用热分析获取动力学参数的方法（Coats-Redfern法，Doyle法，最大速率法和分布活化能模型(DAEM)），计算生物质秸秆热分解反应活化能E、反应级数n及频率因子A，并进行比较。结果表明，采用不同的处理方法，得出的热分解动力学参数不同。利用Coats-Redfern法，玉米秸秆和稻秆在热解主要阶段（失重约5 w%～80 w%时）可由一段一级反应过程描述，升温速率10 K/min时活化能值分别为68.8 kJ/mol和70.0 kJ/mol。Doyle法和DAEM模型得到的结果较为接近，可以得到生物质热解过程中的活化能随失重率的变化曲线。生物质秸秆热解包含分子键能断裂的一系列复杂、连续反应过程。     

Direct measurements of the high temperature rate constants of the reactions NCN + O, NCN + NCN, and NCN + M

The rate constant of the reaction NCN + O has been directly measured for the first time. According to the revised Fenimore mechanism, which is initiated by the NCN forming reaction CH + N(2)→ NCN + H, this reaction plays a key role for prompt NO(x) formation in flames. NCN radicals and O atoms have been quantitatively generated by the pyrolysis of NCN(3) and N(2)O, respectively. NCN concentration-time profiles have been monitored behind shock waves using narrow-bandwidth laser absorption at a wavelength of λ = 329.1302 nm. Whereas no pressure dependence was discernible at pressures between 709 mbar < p < 1861 mbar, a barely significant temperature dependence corresponding to an activation energy of 5.8 ± 6.0 kJ mol(-1) was found. Overall, at temperatures of 1826 K < T < 2783 K, the rate constant can be expressed as k(NCN + O) = 9.6 × 10(13)× exp(-5.8 kJ mol(-1)/RT) cm(3) mol(-1) s(-1) (±40%). As a requirement for accurate high temperature rate constant measurements, a consistent NCN background mechanism has been derived from pyrolysis experiments of pure NCN(3)/Ar gas mixtures, beforehand. Presumably, the bimolecular secondary reaction NCN + NCN yields CN radicals hence triggering a chain reaction cycle that efficiently removes NCN. A temperature independent value of k(NCN + NCN) = (3.7 ± 1.5) × 10(12) cm(3) mol(-1) s(-1) has been determined from measurements at pressures ranging from 143 mbar to 1884 mbar and temperatures ranging from 966 K to 1900 K. At higher temperatures, the unimolecular decomposition of NCN, NCN + M → C + N(2) + M, prevails. Measurements at temperatures of 2012 K < T < 3248 K and at total pressures of 703 mbar < p < 2204 mbar reveal a unimolecular decomposition close to its low pressure limit. The corresponding rate constants can be expressed as k(NCN + M) = 8.9 × 10(14)× exp(-260 kJ mol(-1)/RT) cm(3) mol(-1) s(-1)(±20%).     

Reaction rate of propene pyrolysis

The reaction rate of propene pyrolysis was investigated based on the elementary reactions proposed in Qu et al., J Comput Chem 2009, 31, 1421. The overall reaction rate was developed with the steady-state approximation and the rate constants of the elementary reactions were determined with the variational transition state theory. For the elementary reaction having transition state, the vibrational frequencies of the selected points along the minimum energy path were calculated with density functional theory at B3PW91/6-311G(d,p) level and the energies were improved with the accurate model chemistry method G3(MP2). For the elementary reaction without transition state, the frequencies were calculated with CASSCF/6-311G(d,p) and the energies were refined with the multireference configuration interaction method MRCISD/6-311G(d,p). The rate constants were evaluated within 200-2000 K and the fitted three-parameter expressions were obtained. The results are consistent with those in the literatures in most cases. For the overall rate, it was found that the logarithm of the rate and the reciprocal temperature have excellent linear relationship above 400 K, predicting that the rate follows a typical first-order law at high temperatures of 800-2000 K, which is also consistent with the experiments. The apparent activation energy in 800-2000 K is 317.3 kJ/mol from the potential energy surface of zero Kelvin. This value is comparable with the energy barriers, 365.4 and 403.7 kJ/mol, of the rate control steps. However, the apparent activation energy, 215.7 kJ/mol, developed with the Gibbs free energy surface at 1200 K is consistent with the most recent experimental result 201.9 ± 0.6 kJ/mol.     

Thermal Degradation Kinetics of N,N＇-Di（diethoxythiophosphoryl）-1,4-phenylenediamine

The non-isothermal degradation kinetics of N,N＇-di（diethoxythiophosphoryl）-1,4-phenylenediamine in N2 was studied by TG-DTG techniques.The kinetic parameters,including the activation energy and pre-exponential factor of the degradation process for the title compound were calculated by means of the Kissinger and Flynn-Wall-Ozawa（FWO）method and the thermal degradation mechanism of the title compound was also studied with the Satava-Sestak methods.The results indicate that the activation energy and pre-exponential factor are 152.61 kJ/mol and 9.06×101 4s -1with the Kissinger method and 154.08 kJ/mol with the Flynn-Wall-Ozawa method,respectively.It has been shown that the degradation of the title compound follows a kinetic model of one-dimensional diffusion or parabolic law,the kinetic function is G（α）=α2and the reaction order is n=2.     

Effect of time, temperature, and kinetics on the hysteretic adsorption-desorption of H2, Ar, and N2 in the metal-organic framework Zn2(bpdc)2(bpee)

The intriguing hysteretic adsorption-desorption behavior of certain microporous metal-organic frameworks (MMOFs) has received considerable attention and is often associated with a gate-opening (GO) effect. Here, the hysteretic adsorption of N(2) and Ar to Zn(2)(bpdc)(2)(bpee) (bpdc = 4,4'-biphenyldicarboxylate; bpee = 1,2-bipyridylethene) shows a pronounced effect of allowed experimental time at 77 and 87 K. When the time allowed is on the order of minutes for N(2) at 77 K, no adsorption is observed, whereas times in excess of 60 h is required to achieve appreciable adsorption up to a limiting total coverage. Given sufficient time, the total uptake for N(2) and Ar converged at similar reduced temperatures, but the adsorption of Ar was significantly more rapid than that of N(2), an observation that can be described by activated configurational diffusion. N(2) and Ar both exhibited discontinuous stepped adsorption isotherms with significant hysteresis, features that were dependent upon the allowed time. The uptake of H(2) at 77 K was greater than for both N(2) and Ar but showed no discontinuity in the isotherm, and hysteretic effects were much less pronounced. N(2) and Ar adsorption data can be described by an activated diffusion process, with characteristic times leading to activation energies of 6.7 and 12 kJ/mol. Fits of H(2) adsorption data led to activation energies in the range 2-7 kJ/mol at low coverage and nonactivated diffusion at higher coverage. An alternate concentration-dependent diffusion model is presented to describe the stepwise adsorption behavior, which is observed for N(2) and Ar but not for H(2). Equilibrium is approached very slowly for adsorption to molecularly sized pores at low temperature, and structural change (gate opening), although it may occur, is not required to explain the observations.     

Influence of temperature on the thermo-oxidative degradation of polyamide 6 films

The thermo-oxidative degradation of polyamide 6 (PA6) was studied at relative high temperatures (between 120 and 170 °C) using oxygen uptake and hydroperoxide determination methods, chemiluminescence, FT-IR and UV-VIS spectroscopy as well as solution viscosity and tensile property measurements.The relation between the results of the different analytical techniques and influence of temperature on these relations was determined. Arrhenius plots of the degradation determined with the different methods are linear; however the activation energies determined from these plots depend on the analytical method used. For oxygen uptake measurements and changes in UV absorbance (at 280 nm) and solution viscosity an activation energy of about 120 kJ/mol was calculated, for the increase in carbonyl index of about 80 kJ/mol and for the decrease in elongation at break of about 150 kJ/mol.The changes in oxygen uptake UV absorbance and solution viscosity are probably due to the same chemical process. The lower activation energy from changes in the carbonyl index is attributed to the formation of gaseous products, which play a larger role at higher temperatures. The higher activation energy from the elongation at break measurements was ascribed to the contribution of physical changes that play the largest role at the highest temperatures.     

Segregation and H2 transport rate control in body-centered cubic PdCu membranes

The H2 permeation of a supported 2 microm thick Pd48Cu52 membrane was investigated between 373 and 909 K at DeltaP=0.1 MPa. The initial H2 flux was 0.3 mol.m(-2).s(-1) at 723 K with an ideal H2/N2 selectivity better than 5000. The membrane underwent a bcc-fcc (body-centered cubic to face-centered cubic) phase transition between 723 and 873 K resulting in compositional segregation. After reannealing at 723 K the alloy layer reverted to a bcc structure although a small fcc fraction remained behind. The mixed-phase morphology was analyzed combining X-ray diffraction with scanning electron microscopy-energy-dispersive spectroscopic analysis (SEM-EDS) measurements, which revealed micrometer-scale Cu-enriched bcc and Cu-depleted fcc domains. The H2 flux JH2 of the fcc Pd48Cu52 single phase layer prevailing above 873 K could be described by an Arrhenius law with JH2=(7.6+/-4.9) mol.m(-2).s(-1) exp[(-32.9+/-4.5) kJ.mol(-1)/(RT)]. The characterization of the H2 flux in the mixed-phase region required two Arrhenius laws, i.e., JH2=(1.35+/-0.14) mol.m(-2).s(-1) exp[(-10.3+/-0.5) kJ.mol(-1)/(RT)] between 523 and ca. 700 K and JH2=(56.1+/-9.3) mol.m(-2).s(-1) exp[(-25.3+/-0.6) kJ.mol(-1)/(RT)] below 454 K. The H2 flux exhibited a square root pressure dependence above 523 K, but the pressure exponent gradually increased to 0.77 upon cooling to 373 K. The activation energy and pressure dependence in the intermediate temperature range are consistent with a diffusion-limited H2 transport, while the changes of these characteristics at lower temperatures indicate a desorption-limited H2 flux. The prevalence of desorption as the permeation rate-limiting step below 454 K is attributed to the pairing of an extraordinarily high hydrogen diffusivity with a marginal hydrogen solubility in bcc PdCu alloys. These result in an acceleration of the bulk diffusion rate and a deceleration of the desorption rate, respectively, allowing the bulk diffusion rate to surpass the desorption rate up to relatively high temperatures.     

High resolution 15N NMR of the 225 K phase transition of ammonia borane (NH3BH3): mixed order-disorder and displacive behavior

We report high resolution 15N NMR probing of the solid-solid phase transition of 15N-labeled ammonia borane (NH3BH3) at 225 K. Both the 15N isotropic chemical shift (delta iso) and the spin-lattice relaxation rate (T1-1) exhibited strong anomalies around 225 K. The analysis of T1-1 using the Bloembergen, Purcell, and Pound model showed that the motional correlation time, tau, increased from about 1 to 100 ps and the corresponding Arrhenius activation energy increased from 6 to 14.5 kJ/mol on going through the transition toward lower temperatures. The temperature dependence of delta iso was interpreted by an extension of the Bayer model. The time scale of the underlying motion was found to be in a reasonable agreement with the T1-1 data. These results imply that the NH3 rotor motion plays a pivotal role in the transition mechanism and that the transition is of both order-disorder and displacive type.     

Molecular-dynamic study of liquid ethylenediamine

Models of liquid ethylenediamine (ED) are built using the molecular dynamics approach at temperatures of 293–363 K and a size of 1000 molecules in a basic cell as a cuboid. The structural and dynamic characteristics of liquid ED versus temperature are derived. The gauche conformation of the ED molecule that is characteristic of the gas phase is shown to transition easily into the trans conformation of the molecules in the liquid. NH···N hydrogen bonds are analyzed in liquid ED. The number of H-bonds per ED molecule is found to vary from 5.02 at 293 K to 3.86 at 363 K. The lifetimes in the range of the temperatures and dissociation activation energy for several H-bonds in liquid ED are found to range from 0.574 to 4.524 ps at 293 K; the activation energies are 8.8 kJ/mol for 50% of the H-bonds and 16.3 kJ/mol for 6.25% of them. A weaker and more mobile spatial grid of H-bonds in liquid ED is observed, compared to data calculated earlier for monoethanolamine.     

2,4-二硝基氯苯碱性水解胶团催化的活化能

研究了阳离子表面活性剂氯化十六烷基吡啶(CPC)和十六烷基三甲基氯化铵(CTAC)胶团对2,4-二硝基氯苯(DNCB)碱性水解的催化作用和小分子极性有机物丁醇的加入对该反应的影响,计算了反应活化能.结果表明:(1)CPC和CTAC胶团对DNCB碱性水解都有明显的催化作用;(2)加入少量叔丁醇略有利于提高催化效果;(3)在CPC和CTAC胶团溶液中DNCB碱性水解反应的活化能约为49kJ/mol,比纯水中的91kJ/mol低得多,说明反应机制可能存在差异.     

ON THE PRIMARY PHOTOPROCESS OF 124-kdalton PHYTOCHROME

The photoreaction between P_τ and the first detectable intermediate, lumi-R, of 124-kdalton oat phytochrome has been investigated at low temperatures. The temperature dependence of the quantum yields of the photoreactions, P_τ to lumi-R and lumi-R to P_τ, has been determined. From measurements over a temperature range from 119 to 155 K, an activation barrier of 3.6 ± 0.5 kJ mol ₁ is found for the photoreaction of P_τ with 661-nm actinic light. A higher value (5.7 ± 0.7 kJ mol ^-1) is found for the photoreaction of lumi-R to P^τ. with 698-nm actinic light. Increased quantum yields are found in deuterated buffer solutions at low temperatures. The activation energies for deuterated phytochrome (3.2 ± 0.7 kJ mol^–1 for P_τ with 661-nm irradiation and 6.2 ± 1.2 kJ mol^-1 for lumi-R at 698-nm irradiation) are identical within the limits of error with those of protonated phytochrome. The lack of a deuterium effect for the activation energies favors the Z,E-isomerization rather than proton transfer or tautomerization for the chromophore photochemistry during P_τ⇄lumi-R conversion.     

Cyanoacetylene adsorption on amorphous and crystalline water ice films: investigation through matrix isolation and quantum study.

The structure and energy properties of the 1:1 complexes formed between cyanoacetylene and H2O (D2O) are investigated using FT-IR matrix isolation spectroscopy and ab initio calculations at the MP2/ 6-31G(d,p) level. Cyanoacetylene adsorption and desorption on amorphous ice film are monitored by FT-IR using the temperature-programmed desorption method. In an argon matrix, two types of 1:1 complexes are observed. The first one corresponds to the NH structure, which involves a hydrogen bond with the terminal nitrogen of cyanoacetylene. The second corresponds to the HO form, which involves a hydrogen bond from the cyanoacetylene to the oxygen of water. This last complex is the more stable (DeltaE = -8.1 kJ/mol.). As obtained in argon matrixes, two kinds of adsorption site are observed between HC3N and ice. The first one, stable between 25 and 45 K is characterized by a nu(OH) shift similar to the one observed in matrix for the NH complex. The second, stable at higher temperatures (between 45 and 110 K), corresponds to an interaction with the dangling oxygen site of ice and is similar to the HO complex observed in matrix. From theoretical calculations (DFT method combined with a plane wave basis set and ultrasoft pseudopotentials), it is shown that, for this adsorption site, the HC3N moiety is flattened on the ice surface and stabilized by a long-distance interaction ( approximately 3 A) between one dangling OH and the pi system of the C triple bond C triple bond. The HC3N desorption occurs between 110 and 140 K, and the associated desorption energy is 39 kJ/mol. This value is in good agreement with the first principle calculation based on density functional theory and ultrasoft pseudopotentials (34 kJ/mol). These calculations confirm the electrostatic nature of the interaction forces. A small amount of cyanoacetylene is incorporated into the bulk and desorbs at the onset of the ice crystallization near 145 K. In these two kinds of experiments, HC3N acts as both an electrophilic and a nucleophilic molecule.     

计时电流法测定Fe3+在离子液体BPBF4中的扩散系数

室温离子液体(简称离子液体)作为新型的反应介质和功能材料受到学术界和产业界的高度关注,正在迅速成为多学科交叉的前沿研究领域和具有良好应用前景的“绿色”高新技术,过渡金属化合物是许多重要反应的催化剂,过渡金属离子在室温离子液体中的性质是工业界关心的课题,有关过渡金属的离子液体的研究,     

CuI complexes with N,N',S,S' scorpionate ligands: evidence for dimer-monomer equilibria

The heteroscorpionate N, N', S, S' donor ligands 4-methoxy-3,5-dimethyl-2-(3-(methylthio)-1-(3-(2-(methylthio)phenyl)-1H-pyrazol-1-yl)propyl)pyridine (L(a)) and 4-methoxy-3,5-dimethyl-2-(2-(methylthio)-1-(3-(2-(methylthio)phenyl)-1H-pyrazol-1-yl)ethyl)pyridine (L(b)) were prepared. The Cu(I) complexes [Cu(L(a))]2(BF4)2 (a2(BF4)2) and [Cu(L(b))]2(BF4)2 (b2(BF4)2) were synthesized and characterized by X-ray crystallography. Both compounds exhibit a dinuclear structure, presenting each Cu(I) center in a distorted N, N', S, S' tetrahedral environment. On the basis of nuclear magnetic resonance (NMR) and ESI-mass data, the presence of a mononuclear complex in equilibrium with the dimer was hypothesized for both complexes. The dimerization constants of the processes, 2a(+) = a2(2+) and 2b(+) = b2(2+) , were obtained by (1)H NMR dilution experiments (fast-exchange regime) in CD 3CN: log K(a2(2+)) = 3.55(6) and log K(b2(2+)) = 3.23(5) at 300 K. Thermodynamic parameters were determined by a van't Hoff analysis (280-310 K temperature range): DeltaH(0)(a2(2+)) = -12(1) kJ mol (-1), DeltaH(0)(b2(2+)) = -10(1) kJ mol(-1), DeltaS(0)(a2(2+)) = +27(4) kJ mol (-1), and DeltaS(0)(b2(2+)) = +28(4) kJ mol (-1). Pulsed gradient spin-echo (PGSE) NMR experiments provided the weighted-average hydrodynamic volume (VH) of the species present in CD 3CN solution at different copper concentrations (CCu). Nonlinear interpolation of VH as a function of C Cu for a dimer-monomer equilibrium led to the hydrodynamic volumes of both monomers (VH(0)(M)) and dimers (VH(0)(D)): VH(0)(a(+)) = 620(40) A(3), VH(0)(b(+)) = 550(10) A(3), VH(0)(a2(2+)) = 950(20) A(3), and VH(0)(b2(2+)) = 900(10) A(3). Cyclic voltammetry experiments performed in CH3CN and CH2Cl2 showed a quasi-reversible to irreversible behavior of the Cu(I)/Cu(II) redox couple for both complexes.     

温度对丁腈羟聚氨酯固化反应及性能的影响

端羟基液体丁二烯-丙烯腈共聚物(简称丁腈羟,以HTBN表示)通常用甲苯二异氰酸酯作固化剂,N,N′-二羟丙基苯胺为链延伸剂经二步法固化成丁腈羟聚氨酯弹性体。本文报导丁腈羟-甲苯二异氰酸酯预聚体和N,N′-二羟丙基苯胺体系中同化温度对同化反应及固化弹性体性能的影响规律。     

Decomposition reaction rate of BCl3-C3H6(propene)-H2 in the gas phase

The decomposition reaction rate in the BCl(3)-C(3)H(6)-H(2) gas phase reaction system in preparing boron carbides was investigated based on the most favorable reaction pathways proposed by Jiang et al. [Theor. Chem. Accs. 2010, 127, 519] and Yang et al. [J. Theor. Comput. Chem. 2012, 11, 53]. The rate constants of all the elementary reactions were evaluated with the variational transition state theory. The vibrational frequencies for the stationary points as well as the selected points along the minimum energy paths (MEPs) were calculated with density functional theory at the B3PW91/6-311G(d,p) level and the energies were refined with the accurate model chemistry method G3(MP2). For the elementary reaction associated with a transition state, the MEP was obtained with the intrinsic reaction coordinates, while for the elementary reaction without transition state, the relaxed potential energy surface scan was employed to obtain the MEP. The rate constants were calculated for temperatures within 200-2000 K and fitted into three-parameter Arrhenius expressions. The reaction rates were investigated by using the COMSOL software to solve numerically the coupled differential rate equations. The results show that the reactions are, consistent with the experiments, appropriate at 1100-1500 K with the reaction time of 30 s for 1100 K, 1.5 s for 1200 K, 0.12 s for 1300 K, 0.011 s for 1400 K, or 0.001 s for 1500 K, for propene being almost completely consumed. The completely dissociated species, boron carbides C(3)B, C(2)B, and CB, have very low concentrations, and C(3)B is the main product at higher temperatures, while C(2)B is the main product at lower temperatures. For the reaction time 1 s, all these concentrations approach into a nearly constant. The maximum value (in mol/m(3)) is for the highest temperature 1500 K with the orders of -13, -17, and -23 for C(3)B, C(2)B, and CB, respectively. It was also found that the logarithm of the overall reaction rate and reciprocal temperature have an excellent linear relationship within 700-2000 K with a correlation coefficient of 0.99996. This corresponds to an apparent activation energy 337.0 kJ/mol, which is comparable with the energy barrier 362.6 kJ/mol of the rate control reaction at 0 K but is higher than either of the experiments 208.7 kJ/mol or the Gibbs free energy barrier 226.2 kJ/mol at 1200 K.