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Ethanol and palm oil biodiesel blended with diesel fuel have the potential to reduce greenhouse gas emissions, such as carbon dioxide (CO2), and can gradually decrease dependence on fossil fuels. However, the combustion products from these fuels, such as oxides of nitrogen (NOx), total hydrocarbons (THC) and particulate matter (PM), require to be examined and any beneficial or detrimental effect to the environment needs to be assessed. This study investigates the hydrocarbon selective catalyst reduction (HC-SCR) activities by the effect of combustion using renewable fuels (biodiesel-ethanol-diesel) blends and the effect of hydrogen addition to the catalyst, with the various diesel engine operating conditions. Lower values rate of heat released were recorded as the ethanol fraction increases, resulting in trade-off where, lower NOx was produced while greater concentration of carbon monoxide (CO) and THC was measured in the exhaust. Consequently, increasing the THC/NOx promoting the NOx reduction activity (up to 43%). Additionally, the HC-SCR performance was greatly heightened when hydrogen was added into the catalyst and able to improve the NOx reduction activity up to 73%. The experiment demonstrated plausible alternatives to improve the HC-SCR performance through the aids from fuel blends and hydrogen addition.

Biomass-derived syngas is prone to leakage during transportation. To safely use biomass-derived syngas, we need to study the combustion characteristics of material syngas the purpose of this paper is: at T = 303 K, P = 0.1 MPa, under the condition of the spherical expansion flame method, calculate the laminar burning velocity, and used the Chemkin module of ANSYS to simulate four mechanisms (GRI-3.0, FFCM-1, Li-2015, SanDiego +NOx-2018) to compare, select more appropriate reaction mechanism through experimental data for related research. It was found that the chemical reaction mechanism of GRI-3.0 is more in line with the experimental results. It is found that the experimental results are in good agreement with the linear extrapolation method. When the H2 concentration increases from 22-42%, the peak laminar burning velocity moves in the direction of the lean fuel side. When the H2 concentration increases to 42%, the laminar burning velocity is the fastest, reaching 0.78 m/s. The effect of H2 on thermal diffusivity is high. When H2 concentration reaches 42%, its thermal diffusivity is much higher than other gas components. The adiabatic flame temperature of F1 (22% H2, 45% CO, 9.6% CH4, 23.4% CO2)-air mixtures is the highest, approaching 2196 K. The peak adiabatic flame temperature of F5 (42% H2, 25% CO, 9.6% CH4, 23.4% CO2)-air mixtures is 2082 K, which is comparatively low. Nonetheless, the H2 concentration in F5-air mixtures is higher than that in F1-air mixtures, indicating that H2 has less influence on adiabatic flame temperature than CO. The positive reactions to accelerate laminar burning velocity mainly include R99, R38, and R46. The R52 and R35 can inhibit laminar burning velocity. There are many factors affecting laminar burning velocity, among which high reactive free radicals are the main factors, and the competition between chain branching reaction and chain termination reaction for high reactive free radicals also affects laminar burning velocity. With the increase of concentration of H2, participate in the reaction of the molar mass fraction of highly reactive free radicals and the laminar burning velocity. [ABSTRACT FROM AUTHOR]

[Display omitted] Ethanol and palm oil biodiesel blended with diesel fuel have the potential to reduce greenhouse gas emissions, such as carbon dioxide (CO 2), and can gradually decrease dependence on fossil fuels. However, the combustion products from these fuels, such as oxides of nitrogen (NO x), total hydrocarbons (THC) and particulate matter (PM), require to be examined and any beneficial or detrimental effect to the environment needs to be assessed. This study investigates the hydrocarbon selective catalyst reduction (HC-SCR) activities by the effect of combustion using renewable fuels (biodiesel-ethanol-diesel) blends and the effect of hydrogen addition to the catalyst, with the various diesel engine operating conditions. Lower values rate of heat released were recorded as the ethanol fraction increases, resulting in trade-off where, lower NO x was produced while greater concentration of carbon monoxide (CO) and THC was measured in the exhaust. Consequently, increasing the THC/NO x promoting the NO x reduction activity (up to 43%). Additionally, the HC-SCR performance was greatly heightened when hydrogen was added into the catalyst and able to improve the NO x reduction activity up to 73%. The experiment demonstrated plausible alternatives to improve the HC-SCR performance through the aids from fuel blends and hydrogen addition. [ABSTRACT FROM AUTHOR]

To study the dissolution of UOX spent nuclear fuel in a deep geological environment and the fast release of a selection of relevant radionuclides for long-term safety of this high level waste, leaching experiments were performed with spent nuclear fuel samples originating from the pressurized water reactors (PWRs) Tihange 1 and Gösgen with a similar burnup (50 – 55 MWd.kg HM −1) but different irradiation histories. Six experiments were conducted to investigate the effect of two critical parameters: (1) the highly alkaline environment caused by the presence of cementitious materials in the "Supercontainer design", which is currently the reference design for the long-term management of the high-level nuclear waste forms in Belgium, and (2) the reducing conditions imposed by the presence of hydrogen from the corrosion of iron-based materials present in the engineered barriers. The experiments were performed using autoclaves under pressure from 1 to 40 bar with a pure Ar atmosphere or a mixture of H 2 /Ar. Divided into two consecutive phases, the total experimental duration was about 1400 days. The Phase I provided mainly information about the fast release of the fission products while the perspective of the Phase II was to study the long-term evolution of the spent fuel matrix. During the leaching experiment, concentrations of a selection of radionuclides (238U, 129I, 137Cs, 90Sr and 99Tc) were monitored in solution and the amounts of Kr and Xe were measured in the gas phase. Based on results of the experiments conducted for up to 40 months (i.e. during Phase I of the experimental program), we observe that there is a continuous release of 137Cs, 90Sr and of the fission gases and a clear impact of the irradiation history on the release of certain fission products. [ABSTRACT FROM AUTHOR]

Abstract: Effect of H2 amount on the activity and selectivity of Chevron-Phillips trimerization system, i.e., chromium(III) tris(2-ethylhexanoate)/2,5-dimethylpyrrole/triethylaluminum (TEA)/tetrachloroethane (TCE), was examined. In this regard, in addition to catalytic ingredients and ethylene monomer, 2.5 and 5 bar H2 were utilized in the oligomerization reactor and the reaction results were compared with those without H2. Results showed that addition of hydrogen has a remarkable effect on polymer formation and catalyst activity so that 147% decrease in polymer formation and 38% increase in activity were observed upon addition of 5 bar H2. However, its effect on 1-hexene selectivity was not pronounced. Then, molecular modeling with DFT method was employed to simulate oligomerization process in molecular level. Energy results revealed that formation of 1-hexene has less energy barrier than the formation of 1-butene and 1-octene which confirms higher selectivity of Chevron-Phillips system toward 1-hexene formation. Furthermore, interaction of hydrogen with catalytic active center was studied via hydrogenolysis of metalacycles. Energy results revealed that it is energetically a facile process so that the bigger the circle, the easier hydrogenolysis.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: This article reports on the promotional effect of adding H2 to the reaction feed for the selective catalytic reduction of NOx with propene (H2–C3H6-SCR) over Au/Al2O3 catalysts. For this purpose, the influence of the Au loading in H2–C3H6-SCR was investigated. The H2 promoting effect in C3H6-SCR, well-established for Ag/Al2O3, was also demonstrated for Au/Al2O3. Although less pronounced than for Ag-based systems, the H2 effect allowed for a substantial increase in NOx conversion at temperatures higher than 250 °C on Au/Al2O3 samples. The highest NOx to N2 conversion in H2–C3H6-SCR was obtained for lowly-loaded gold samples (~ 1 wt% Au) with the smallest gold particle sizes. An increase in H2 concentration in the reaction feed also led to an increase in NOx conversion. The experiments performed in the present study as a function of the reaction temperature underlined the fact that concomitant activation of H2 and C3H6 is critical to achieve a high H2 promoting effect in H2–C3H6-SCR. Whereas this requirement is fulfilled for Ag/Al2O3, a temperature gap between the oxidation profiles of H2 and C3H6 remains for Au/Al2O3 due to the early oxidation of H2 on gold nanoparticles, which therefore limits the NOx conversion at low temperature.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Highlights: [•] NO x reduction to N2 in H2-C3H6-SCR increases with decreasing Ag loadings. [•] Changes in the kinetic parameters remarkably correlate to the changes in NO x uptakes. [•] C3H6 and H2 are activated on Ag species, while NO x are activated on Al2O3. [•] The number of active sites on Al2O3 accounts for the observed catalytic activities. [Copyright &y& Elsevier]

Abstract: Out-of-pile tritium release experiments under different water uptake contents and purge gas chemistry were performed on Li4SiO4. Water measurement was performed on samples under different experimental procedures. It was found that water was adsorbed on the sample during its transferring and storage process. A strong dependence of tritium release behavior on water uptake was determined. By doping H2 in the sweep gas, the formation of water in orthosilicate was observed in addition to the isotope exchange reaction with H2 gas. Thermal desorption peaks of the water formation reaction and H2 isotope exchange reaction appeared at 668°C and 463°C, respectively, at ramping rate of 5°C/min. [Copyright &y& Elsevier]

Abstract: The role of hydrogen in promoting the reduction by ammonia of NO x on silver catalysts has been investigated using a Short Time on Stream (STOS) technique to allow differentiation between potentially reactive intermediates and relatively inactive spectator species. Under these conditions, we have used DRIFTS to identify surface nitrate species that are formed and removed on a timescale of seconds. This is in contrast to nitrate species observed under normal steady-state conditions which can continue to form over many tens of minutes. Since this timescale of seconds is very similar to the response rate at which the NH3/NO x to N2 reaction is accelerated when H2 is added, or decelerated when H2 is removed, we conclude that this fast-forming and fast disappearing nitrate species is most probably adsorbed on or close to the active Ag sites. The removal of such a blocking nitrate species from the active sites can explain the effect of H2 in greatly increasing the rate of the overall de-NO x reaction. [Copyright &y& Elsevier]

Abstract: The problem of differentiating between active and spectator species that have similar infrared spectra has been addressed by developing short time-on-stream in situ spectroscopic transient isotope experimental techniques (STOS-SSITKA). The techniques have been used to investigate the reaction mechanism for the reduction of nitrogen oxides (NO x ) by hydrocarbons under lean-burn (excess oxygen) conditions on a silver catalyst. Although a nitrate-type species tracks the formation of isotopically labeled dinitrogen, the results show that this is misleading because a nitrate-type species has the same response to an isotopic switch even under conditions where no dinitrogen is produced. In the case of cyanide and isocyanate species, the results show that it is possible to differentiate between slowly reacting spectator isocyanate species, probably adsorbed on the oxide support, and reactive isocyanate species, possibly on or close to the active silver phase. The reactive isocyanate species responds to an isotope switch at a rate that matches that of the rate of formation of the main product, dinitrogen. It is concluded that these reactive isocyanates could potentially be involved in the reduction of NO x whereas there is no evidence to support the involvement of nitrate-type species that are observable by infrared spectroscopy. [Copyright &y& Elsevier]

Abstract: In recent years, the impact of H2 on α-radiation induced dissolution of UO2-based spent nuclear fuel has been studied and debated extensively. Experimental results on the effect of H2 on the concentration of H2O2 during α-radiolysis have been shown to disagree with numerical simulations. For this reason, the reaction scheme used in simulations of aqueous radiation chemistry has sometimes been questioned. In this work, we have studied the impact of H2 on the H2O2 concentration in α-irradiated aqueous solution using numerical simulations. The effects of H2 pressure, α-dose rate and concentration were investigated by performing systematic variations in these parameters. The simulations show that the discrepancy between the previously published experimental result and numerical simulations is due to the use of a homogeneous dose rate (the energy is assumed to be equally distributed in the whole volume). Taking the actual dose rate of the α-irradiated volume into account, the simulation is in perfect agreement with the experimental results. This shows that the H2 effect is strongly α-dose rate dependent, and proves the reliability of the reaction scheme used in the simulations. The simulations also show that H2 influences the H2O2 concentration under α-radiolysis. The magnitude of the effect depends on the dose rate and the H2 pressure as well as on the concentration of . The impact of the radiolytic H2 effect on the rate of α-radiation induced dissolution of spent nuclear fuel is discussed along with other (α- and γ-) radiation induced processes capable of reducing the concentration of uranium in solution. The radiolytic H2 effect is quantitatively compared to the previously presented noble metal catalyzed H2 effect. This comparison shows that the noble metal catalyzed H2 effect is far more efficient than the radiolytic H2 effect. Reduction of U(VI) in solution due to low dose rate γ-radiolysis in the presence of H2 is proposed to be the cause of the H2 effect observed in leaching experiments on α-doped UO2. [Copyright &y& Elsevier]

The NO x reduction with n-C6H14 was studied over a 3% Ag/Al2O3 catalyst in the presence of hydrogen. The catalyst performance was evaluated by varying the H2 concentration from 0 to 1600 ppm and by comparing the results with blank runs in which an empty reactor with no catalyst was used. Two distinct reaction pathways were revealed: one at low-temperature (Treact < 370 °C) and another one at high-temperature (Treact > 370–390 °C). Co-feeding of H2 promotes the reaction within the 150–360 °C interval. The high-temperature pathway (Treact > 370–390 °C) seems to be almost independent of hydrogen co-feeding. The homogeneous gas-phase NO x oxidation initiated by NO presumably plays an important role in this high-temperature pathway. [ABSTRACT FROM AUTHOR]

Abstract: The effect of temperature and transient addition of H2 on the NOx–SCR reaction was investigated over a 2-wt.% Ag/Al2O3 catalyst using isotopically labelled 15NO. The addition and removal of hydrogen had a marked effect on the nitrogen balance at temperatures ranging from 245 to 400°C. At a low temperature (245°C), the addition of hydrogen resulted in the storage of NOx, whereas, the reverse was true at 400°C, where NOx was stored upon removal of hydrogen from the feed. The transient NOx storage effect could be harnessed to allow continuous high NOx conversion with intermittent hydrogen addition. In particular, an average NOx conversion of 79% could be achieved during transient experiments in which H2 was switched in and out of the feed in 6-s intervals at 300°C. [Copyright &y& Elsevier]

Abstract: The H2-assisted hydrocarbon selective catalytic reduction (HC-SCR) of NO x was investigated using fast transient kinetic analysis coupled with isotopically labelled 15NO. This allowed monitoring of the evolution of products and reactants during switches of H2 in and out of the SCR reaction mix. The results obtained with a time resolution of less than 1 s showed that the effect on the reaction of the removal or addition of H2 was essentially instantaneous. This is consistent with the view that H2 has a direct chemical effect on the reaction mechanism rather than a secondary one through the formation of “active” Ag clusters. The effect of H2 partial pressure was investigated at 245 °C, it was found that increasing partial pressure of H2 resulted in increasing conversion of NO and octane. It was also found that the addition of H2 at 245 °C had different effects on the product distribution depending on its partial pressure. The change of the nitrogen balance over time during switches in and out of hydrogen showed that significant quantities of N-containing species were stored when hydrogen was introduced to the system. The positive nitrogen balance on removal of H2 from the gas phase showed that these stored species continued to react after removal of hydrogen to form N2. [Copyright &y& Elsevier]

Abstract: In this work we present the results obtained with 3 catalysts (Pt, Rh and Ag on alumina) tested in ranges of temperatures and gas hourly space velocities typical of diesel engines in real trucks. NO concentration was 500ppm, C3H6 ranged between 500 and 2000ppm, while oxygen was always 5%. All the catalysts were active and showed high conversions. Both Pt and Rh were active at low temperature (T 50 =200–250°C) but had quite high selectivity towards NO2. Silver was active at higher temperature, but showed very high selectivity towards N2. A strong boosting effect on NO conversion was recorded if H2 was added to the gas mixture. [Copyright &y& Elsevier]