Ni-based catalysts have been widely used for the COsub.2 reforming of methane (CRM) process, but deactivation is their main problem. This study created an alternative electronic Ni-NiO-CeOsub.2 ...interaction on the surface of 5 wt% Ni-5 wt% CeOsub.2/Alsub.2Osub.3-MgO (5Ni5Ce(xh)/MA) catalysts to enhance catalytic potential simultaneously with coke resistance for the CRM process. The Ni-NiO-CeOsub.2 network was developed on Alsub.2Osub.3-MgO through layered double hydroxide synthesis via our ammonia vapor diffusion impregnation method. The physical properties of the fresh catalysts were analyzed employing FESEM, Nsub.2 physisorption, and XRD. The chemical properties on the catalyst surface were analyzed employing Hsub.2-TPR, XPS, Hsub.2-TPD, COsub.2-TPD, and Osub.2-TPD. The CRM performances of reduced catalysts were evaluated at 600 °C under ambient pressure. Carbon deposits on spent catalysts were determined quantitatively and qualitatively by TPO, FESEM, and XRD. Compared to 5 wt% Ni-5 wt% CeOsub.2/Alsub.2Osub.3-MgO prepared by the traditional impregnation method, the electronic interaction of the Ni-NiO-CeOsub.2 network with the Alsub.2Osub.3-MgO support was constructed along the time of ammonia diffusion treatment. The electronic interaction in the Ni-NiO-CeOsub.2 nanostructure of the treated catalyst develops surface hydroxyl sites with an efficient pathway of OH* and O* transfer that improves catalytic activities and coke oxidation.
Atmospheric levels of ammonia (NH.sub.3) have substantially increased during the last century, posing a hazard to both human health and environmental quality. The atmospheric budget of NH.sub.3, ...however, is still highly uncertain due to an overall lack of observations. Satellite observations of atmospheric NH.sub.3 may help us in the current observational and knowledge gaps. Recent observations of the Cross-track Infrared Sounder (CrIS) provide us with daily, global distributions of NH.sub.3 . In this study, the CrIS NH.sub.3 product is assimilated into the LOTOS-EUROS chemistry transport model using two different methods aimed at improving the modeled spatiotemporal NH.sub.3 distributions. In the first method NH.sub.3 surface concentrations from CrIS are used to fit spatially varying NH.sub.3 emission time factors to redistribute model input NH.sub.3 emissions over the year. The second method uses the CrIS NH.sub.3 profile to adjust the NH.sub.3 emissions using a local ensemble transform Kalman filter (LETKF) in a top-down approach. The two methods are tested separately and combined, focusing on a region in western Europe (Germany, Belgium and the Netherlands). In this region, the mean CrIS NH.sub.3 total columns were up to a factor 2 higher than the simulated NH.sub.3 columns between 2014 and 2018, which, after assimilating the CrIS NH.sub.3 columns using the LETKF algorithm, led to an increase in the total NH.sub.3 emissions of up to approximately 30 %. Our results illustrate that CrIS NH.sub.3 observations can be used successfully to estimate spatially variable NH.sub.3 time factors and improve NH.sub.3 emission distributions temporally, especially in spring (March to May). Moreover, the use of the CrIS-based NH.sub.3 time factors resulted in an improved comparison with the onset and duration of the NH.sub.3 spring peak observed at observation sites at hourly resolution in the Netherlands. Assimilation of the CrIS NH.sub.3 columns with the LETKF algorithm is mainly advantageous for improving the spatial concentration distribution of the modeled NH.sub.3 fields. Compared to in situ observations, a combination of both methods led to the most significant improvements in modeled monthly NH.sub.3 surface concentration and NH4+ wet deposition fields, illustrating the usefulness of the CrIS NH.sub.3 products to improve the temporal representativity of the model and better constrain the budget in agricultural areas.
Gao‐Feng Chen
Angewandte Chemie International Edition,
July 18, 2022, Letnik:
61, Številka:
29
Journal Article
Recenzirano
“The most important thing I have learned from my students is that everyone can be a teacher and teach at what they are good at … I wish I could have received advice from Fritz Haber, the first ...scientist to produce ammonia from air …” Find out more about Gao‐Feng Chen in his Introducing … Profile.
Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions has been considered as a promising approach for green ammonia synthesis; however, non-precious metal-based catalysts with ...excellent NRR electrocatalytic performance have been scarce. Herein, self-supported bimetallic electrocatalysts of Ni.sub.12P.sub.5/FeP.sub.4 nanoplates grown on carbon cloth were synthesized by a combined process of hydrothermal technology and low-temperature phosphidation. The catalyst exhibits excellent electrocatalytic N.sub.2 fixation performance with a high NH.sub.3 yield rate of 3.08 x 10.sup.-10 mol s.sup.-1 cm.sup.-2 (16.40 mug h.sup.-1 mgcat-1), Faradaic efficiency (39.9%) as well good durability at - 0.1 V in 0.1 M Na.sub.2SO.sub.4 at ambient conditions, which are attributed to the distinctive nanostructure and rational composition. Our study paves the way for expanding the scope of NRR research and designing more efficient electrochemical ammonia synthesis in the future.
In the salt lake industry, large amounts of steamed ammonia liquid waste are discharged as byproducts. The conversion of the residues into high value-added vaterite-phase calcium carbonate products ...for industrial applications is highly desirable. In this research, the feasibility of preparing vaterite-phase CaCOsub.3 in different CaClsub.2-COsub.2-MOH-Hsub.2O systems using steamed ammonia liquid waste was studied in the absence of additives. The effects of initial CaClsub.2 concentration, stirring speed and COsub.2 flow rate on the composition of the CaCOsub.3 crystal phase were investigated. The contents of vaterite were researched by the use of steamed ammonia liquid waste as a calcium source and pure calcium chloride as a contrast. The influence of the concentration of Csub.NH3·H2O/Csub.Ca2+ on the carbonation ratio and crystal phase composition was studied. The reaction conditions on the content, particle size and morphology of vaterite influence were discussed. It was observed that single vaterite-phase CaCOsub.3 was favored in the CaClsub.2-COsub.2-NHsub.4OH-Hsub.2O system. Additionally, the impurity ions in steamed ammonia liquid waste play a key role in the nucleation and crystallization of vaterite, which could affect the formation of single-phase vaterite. The obtained results provided a novel method for the preparation of single vaterite particles with the utilization of COsub.2 and offered a selective method for the extensive utilization of steamed ammonia liquid waste.
In this paper, TiO.sub.2/InVO.sub.4n-n nanoheterojunctions with enhanced gas sensing performance were successfully synthesized. The TiO.sub.2/InVO.sub.4-based sensor exhibits relatively low optimum ...operating temperature of 250 °C, at which the sensitivity and response/recovery time are 30.5 and 10/10 s, respectively, to 100 ppm ammonia gas. The effective detection (R.sub.a/R.sub.g = 1.7) to 1 ppm ammonia signifies the low detection limit of the sensor. Moreover, the sensor possesses evident room temperature response (R.sub.a/R.sub.g = 3.0, 100 ppm) to ammonia gas. Based on these, the enhanced sensing mechanisms of TiO.sub.2/InVO.sub.4 have been discussed in-depth, which can be ascribed to the synergistic effects of eximious absorption kinetics, outstanding carrier dynamics, unique nanoheterojunction structure and excellent catalytic property. This provides a meaningful guidance for the subsequent nanoheterojunction construction for excellent gas sensor.
Ammonia (NHsub.3), which has a 17.7 wt% gravimetric hydrogen density, has been considered as a potential hydrogen storage material. This study looked at the thermocatalytic decomposition of NHsub.3 ...using a bulk Mosub.2N catalyst that was boosted by alkali metals (AM: 5 wt% Li, K, Cs). The K-Mosub.2N catalyst outperformed all other catalysts in this experiment in terms of catalytic performance. At 6000 hsup.−1 GHSV, 100% conversion of NHsub.3 was accomplished using the K-Mosub.2N, Cs-Mosub.2N, and Mosub.2N catalysts. However, when compared to other catalysts, K-Mosub.2N had the highest activity, or 80% NHsub.3 conversion, at a lower temperature, or 550 °C. The catalytic activity exhibited the following trend for the rate of hydrogen production per unit surface area: K-Mosub.2N > Cs-Mosub.2N > Li-Mosub.2N > Mosub.2N. Up to 20 h of testing the K-Mosub.2N catalyst at 600 °C revealed no considerable deactivation.
The development of Ni/Zr-doped Al.sub.2O.sub.3 was achieved to reduce the reaction temperatures in ammonia decomposition by doping Zr into Al.sub.2O.sub.3 framework. The Ni/Zr-doped Al.sub.2O.sub.3 ...exhibits higher H.sub.2 yield and NH.sub.3 conversion than Ni/gamma-Al.sub.2O.sub.3 in a continuous operation. Partial doping of Zr in Al.sub.2O.sub.3 framework can increase Ni dispersion, Ni surface area and basic sites of the Ni catalyst. These effects can promote in both dehydrogenation of NH.sub.3 and recombination of nitrogen adsorbates in an NH.sub.3 decomposition mechanism. The comparison between roles of Zr as a dopant and a promoter for Ni catalyst was also discussed.
