Temperature dependence of photocatalytic CO2reduction by trans(Cl)–Ru(bpy)(CO)2Cl2: activation energy difference between CO and formate production

2017 ◽  
Vol 198 ◽  
pp. 263-277 ◽  
Author(s):  
Hitoshi Ishida ◽  
Akihiko Sakaba
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Temperature Dependence ◽  
Catalytic System ◽  
Energy Difference ◽  
Catalytic Cycle ◽  
The Difference ◽  
A Minor ◽  
Increasing Temperature ◽  
Formate Production

The temperature dependence of photocatalytic CO2reduction bytrans(Cl)–Ru(bpy)(CO)2Cl2(bpy: 2,2′-bipyridine) has been researched in ethanol (EtOH)/N,N-dimethylacetamide (DMA) solutions containing [Ru(bpy)3]2+(a photosensitizer) and 1-benzyl-1,4-dihydronicotinamide (BNAH, an electron donor). The catalytic system efficiently reduces CO2to carbon monoxide (CO) with formate (HCOO−) as a minor product. The mechanism of the catalysis consists of the electron-relay cycle and the catalytic cycle: in the former cycle the photochemically generated reduced species of the photosensitizer injects an electron to the catalyst, and in the latter the catalyst reduces CO2. At a low concentration of the catalyst (5.0 μM), where the catalytic cycle is rate-determining, the temperature dependence of CO/HCOO−is also dependent on the EtOH contents: the selectivity of CO/HCOO−decreases in 20% and 40%-EtOH/DMA with increasing temperature, while it increases in 60%-EtOH/DMA. The temperature dependence of the CO/HCOO−selectivity indicates that the difference in activation energy (ΔΔG‡) between CO and HCOO−production is estimated asca.3.06 kJ mol−1in 40%-EtOH/DMA at 298 K.

scholarly journals On the influence of temperature and chemical properties on viscosity of Moravian wines

2007 ◽  
Vol 55 (1) ◽  
pp. 59-64 ◽  
Author(s):  
Miroslav Havlíček ◽  
Libor Severa ◽  
Ivo Křivánek
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Viscous Flow ◽  
Chemical Properties ◽  
Theoretical Models ◽  
Temperature Influence ◽  
Increasing Temperature ◽  
South Moravia ◽  
And Chemical Properties

Standard chemical analysis was performed to characterise six samples of bottled wines from South Moravia. Temperature influence (range from 20 °C to 50 °C). Density data processing led to determination of the expansibility coefficients at 25 °C and their temperature dependence. It was found that, viscosity of wine decreases non-linearly with increasing temperature. Fitting of the experimental data in some theoretical models was performed in order to describe the temperature dependence of the viscosity of wine. A modified Andrade equation was found to best describe this dependence. The activation energy for viscous flow of wine, calculated by Arhenius relation, varied from 18.50 kJ.mol–1 to 20.15 kJ. mol–1. Correlations between the activation energy for viscous flow and the concentrations of solutes other than ethanol were estimated.

scholarly journals Транспортные процессы с участием атомов углерода между поверхностью и объемом родия при образовании и разрушении графена

2020 ◽  
Vol 54 (6) ◽  
pp. 552
Author(s):  
Е.В. Рутьков ◽  
Е.Ю. Афанасьева ◽  
Н.Р. Галль
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Temperature Dependence ◽  
Atomic Carbon ◽  
Graphene Growth ◽  
Carbon Dissolution ◽  
The Difference ◽  
Kinetics Of

Equilibrium transport of atomic carbon between Rh surface and bulk has been studied. This transport controls the kinetics of the phase transition resulting in graphene growth or destruction. The difference ΔE=0.7 eV has been measured between the activation energy of atomic carbon dissolution E1s and that of its segregation from the bulk to the surface E1s. The temperature dependence of chemisorbed carbon critical cover Neq = Neq(T) has been measured, that is the cover when 2D phase transition takes place and graphene islands start to grow. E.g., Neq = 7.7•1014 cm-2 at T = 1800 K, and Neq = 3.1•1014 cm-2 at T = 1000 K.

The Temperature Dependence of the Electrical Conductivity Activation Energy of the of Aqueous Electrolyte Solutions

2021 ◽  
Vol 1031 ◽  
pp. 228-233
Author(s):  
Yuliya M. Artemkina ◽  
Vladimir V. Shcherbakov ◽  
Irina A. Akimova
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Temperature Dependence ◽  
Aqueous Electrolyte ◽  
Electrolyte Solutions ◽  
Temperature Step ◽  
Conductivity Activation Energy ◽  
Intermolecular Hydrogen Bonds ◽  
Optimal Value ◽  
Increasing Temperature

The procedure for determining the activation energy of conductivity Еκ is analyzed depending on the temperature step ΔT. It is shown that with increasing ΔT, the error in the calculation of Eκ decreases, but the calculated value of Eκ decreases. In order not to lose the temperature dependence of the activation energy, it is necessary to choose the optimal value of Δt. In our opinion, this value should not exceed 5 – 10 °C. Taking into account the decrease in concentration with increasing temperature due to a decrease in density has virtually no effect on the accuracy of determining Eκ, provided that ΔT is 5 – 10 °C. It has been shown that in the temperature range 20 – 80 °C, the activation energy of conductivity decreases with increasing temperature. This decrease is due to the rupture of intermolecular hydrogen bonds of the solvent with increasing temperature. It was suggested that the movement of ions in an aqueous solution may be accompanied by the breaking of hydrogen bond of the solvent.

REACTIONS OF ALKOXY RADICALS: V. PHOTOLYSIS OF DI-t-BUTYL PEROXIDE

1958 ◽  
Vol 36 (9) ◽  
pp. 1227-1232 ◽  
Author(s):  
Garnett McMillan ◽  
M. H. J. Wijnen
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Energy Difference ◽  
Butyl Alcohol ◽  
Reaction Products ◽  
Butyl Ether ◽  
Alkoxy Radicals ◽  
Temperature Range ◽  
Butyl Peroxide ◽  
Butoxy Radical

The photolysis of di-t-butyl peroxide has been investigated over the temperature range 25 ° to 79 °C. As reaction products were observed: acetone, t-butyl alcohol, methyl t-butyl ether, i-butylene oxide, ethane, methane, and carbon monoxide. The following reactions, involving the t-butoxy radical, have been studied:[Formula: see text]An activation energy difference of E2 − E6 = 3 kcal has been obtained.

TEMPERATURE DEPENDENCE OF RELAXATION IN AlGaN/GaN HETEROSTRUCTURES

2007 ◽  
Vol 14 (04) ◽  
pp. 837-840
Author(s):  
Z. S. JIANG ◽  
W. ZHANG ◽  
Q. JI ◽  
J. XU ◽  
D. J. CHEN ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Tensile Strain ◽  
Lattice Strain ◽  
Passive Layer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Higher Temperature ◽  
The Difference ◽  
Increasing Temperature

Effects of Si 3 N 4 passivation layer on the lattice strain of Al 0.22 Ga 0.78 N layer with the thickness of 100 nm has been studied by in situ X-ray diffraction by the temperature range of 25°C–550°C. Results show that the temperature dependence of the strain relaxations can be separated into three linear regions. After passivation, an additional in-plane tensile strain is observed. The residual tensile strain increases with increasing temperature at low temperature, while at higher temperature the residual tensile strain decreases slightly. There is clear influence when a passive layer is deposited on the surface of the heterostructures. The linear regions in the temperature dependence of strain vary after the passive layer deposited on the heterostructure. These results indicate that the variation of the lattice strain relates to the difference in thermal stability between the epitaxy layer and the substrate.

scholarly journals Reduction kinetics of lead-rich slag with carbon in the temperature range of 1073 to 1473K

2013 ◽  
Vol 49 (2) ◽  
pp. 201-206 ◽  
Author(s):  
X. Hou ◽  
K.C. Chou ◽  
B. Zhao
Keyword(s):  
Activation Energy ◽  
Reaction Rate ◽  
Graphite Crucible ◽  
Reduction Reaction ◽  
Synthetic Slag ◽  
Reduction Kinetics ◽  
Temperature Range ◽  
Diffusion Controlled ◽  
The Difference ◽  
Increasing Temperature

Extensive experiments have been carried out on the reduction of lead-rich slag in graphite crucible at temperature range of 1073 to 1473K. The reduction kinetics was also compared between industrial sinters and synthetic slags. The extent of reduction was measured by the volume of CO-CO2 gas produced at a given temperature and time. It was found that, at a given temperature, the reaction rate between the slag and carbon was initially fast and then slow as the extent of the reaction increases. Only limited reaction between slag and carbon occurred at temperatures below 1173K. At temperatures above 1173K, the reaction rate increased significantly with increasing temperature. The reduction reaction was found to be mainly liquid-solid reaction, which was chemically controlled at initial stage and diffusion controlled at later stage. The apparent activation energy was calculated to be 83.8 kJ/mol at chemically controlled stage and 224.9 kJ/mol at diffusion controlled stage for reduction of industrial sinter. For the synthetic slag, the reaction activation energy was 102.9 kJ/mol at chemically controlled stage and 259.4 kJ/mol at diffusion controlled stage. The difference of the activation energy between industrial sinter and synthetic slag can be explained by the difference in their CaO/SiO2 ratios.

Lattice Imperfections and Relaxation of Cl NQR in Chloral Iso-Butylhemiacetal

1990 ◽  
Vol 45 (3-4) ◽  
pp. 481-484 ◽  
Author(s):  
Haruo Niki ◽  
Ryokan Igei ◽  
Takuya Higa ◽  
Masao Hashimoto ◽  
Takahiro Isono
Keyword(s):  
Activation Energy ◽  
Electric Field ◽  
Electric Field Gradient ◽  
Temperature Dependence ◽  
Field Gradient ◽  
Lattice Defects ◽  
Gradual Decrease ◽  
Line Broadening ◽  
Group A ◽  
The Difference

Abstract The temperature dependence of the S/N ratios of three 35Cl NQR lines (v1, v2 , v3) in chloral iso-butylhemiacetal shows interesting features in the range 77-300 K. 35Cl T1 indicates that above 220 K reorientation of CCl 3 is excited, and this results in a gradual decrease in S/N. The activation energy calculated from 35Cl NQR T1 results is 30 kJ mol-1 for v1 and v2 but 25 kJ mol -1 for v 3 . The difference seems to be attributable to the motion of H in the OH group. A minimum of 35Cl NQR T2 is found around 180 K but 35Cl T1 shows no anomaly. 35Cl T2 determines the S/N ratios in the range between 130-220 K. The line broadening below 130 K is attributable to an inhomogeneity of the electric field gradient at resonant nuclei produced by lattice defects.

Microscopic Interpretation of Arrhenius Parameters

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Transition State Theory ◽  
Average Energy ◽  
Zero Point ◽  
State Theory ◽  
Exponential Factor ◽  
Quantum Tunnelling ◽  
Microscopic Interpretation ◽  
The Difference

This chapter reviews the microscopic interpretation of the pre-exponential factor and the activation energy in rate constant expressions of the Arrhenius form. The pre-exponential factor of apparent unimolecular reactions is, roughly, expected to be of the order of a vibrational frequency, whereas the pre-exponential factor of bimolecular reactions, roughly, is related to the number of collisions per unit time and per unit volume. The activation energy of an elementary reaction can be interpreted as the average energy of the molecules that react minus the average energy of the reactants. Specializing to conventional transition-state theory, the activation energy is related to the classical barrier height of the potential energy surface plus the difference in zero-point energies and average internal energies between the activated complex and the reactants. When quantum tunnelling is included in transition-state theory, the activation energy is reduced, compared to the interpretation given in conventional transition-state theory.

scholarly journals Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alberto Palma ◽  
Javier Mauricio Loaiza ◽  
Manuel J. Díaz ◽  
Juan Carlos García ◽  
Inmaculada Giráldez ◽  
...  
Keyword(s):  
Activation Energy ◽  
Acid Hydrolysis ◽  
Energy Production ◽  
Combustion Process ◽  
Operating Conditions ◽  
Raw Material ◽  
Energy Of Combustion ◽  
Increasing Temperature ◽  
Hydrolysis Of ◽  
Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

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