查看更多>>摘要：Methane is the main component of natural gas, and the latter is a clean natural resource with an abundant reserve and wide distribution. Elemental sulfur is both naturally available on the earth and being artificially generated as a recalcitrant solid waste in chemical processes. The co-utilization of elemental sulfur and methane is thus of economic and environmental benefits. Here, a new catalytic route for elemental sulfur-assisted methane activation is demonstrated over metal-loaded zeolite catalysts at a low temperature of 400 degrees C. Over 10% methane conversion can be achieved even after the catalyst is recycled five times, and the selectivity is well controlled, generating over 90% C-2-C-4 hydrocarbons as the main products. Control experiments are employed to demonstrate the strategy developed for catalyst design, and a series of verification experiments accompanied by various catalyst characterizations are also performed to elucidate the involved reaction mechanism. The results are further substantiated by theoretical calculations for proposing the possible reaction network. It is suggested that the Langmuir-Hinshelwood surface reaction mechanism might be followed, in which elemental sulfur and methane are both adsorbed over the catalyst surface in a competitive way. When methane activation is triggered and significantly enhanced in the presence of sulfur, both surface reaction and gas-phase reaction can proceed, generating sulfides as complete oxidation products and light hydrocarbons as partial oxidation products, respectively. As a result, the product distribution can be well modulated by the adsorption properties of the charged catalyst. This process provides a transformative cost- and energy-effective way for the co-utilization of two low value-added feedstocks with unique advantages in the natural gas and petroleum industry.
查看更多>>摘要：This study leverages piezocatalysis to accelerate redox reactions in heterogeneous peroxymonosulfate (PMS) activation. We syntheized few-layered molybdenum disulfide (MoS2) nanosheets as the piezoelectric catalyst for ultrasonic vibration (US)-coupled PMS system toward enhanced pollutant abatement. Scavenger tests, dissolved oxygen (DO) exclusion experiment and electron paramagnetic resonance (EPR) identify that sulfate radical (SO4.-) and singlet oxygen (O-1(2)) are the primary ROS in the US/MoS2/PMS system. Particularly, O-2(.-) is a vital intermediate for O-1(2) generation, and multiple formation pathways of O-1(2) were proposed in the US/MoS2/PMS system. With the assistance of DO and ultrasound, the utilization efficiency and activity of PMS will be remarkably increased because the majority of PMS evolves into more reactive SO4.- and O-1(2) for pollutant degradation. This work not only provides mechanistic insights into the interconnected regimes of piezocatalysis and heterogeneous Fenton-like reactions, but also achieves high chemical efficiency for sustainable water remediation.
查看更多>>摘要：Developments of Fe-TAML/H2O2 systems were conducted for the removal of refractory organic micropollutants in water. Herein, we investigated degradation of 68 structurally diverse sulfur-containing micropollutants (ng/L-mu g/L) in water by Fe-TAML/H2O2, and developed predictive models of the reactivity of Fe-TAML/H2O2 using micropollutant, Fe-TAML and H2O2 data. The micropollutants were usually degraded rapidly in water within 20 min, and the k(obs) values (0.0054 to > 0.47 min(-1)) drastically varied with compounds and/or solution pH. Static complexation and electron transfer between Fe-TAML and compounds were proposed for the high reactivity and selectivity of Fe-TAML/H2O2 toward micropollutant over naturally occurring dissolved organic matter (DOM). The mechanism-based reaction models of Fe-TAML/H2O2 were well extrapolated to large diversities of organic compounds and various types of water. This study indicates that Fe-TAML/H2O2 systems may provide a technical basis for the removal of micropollutants in water, despite the presence of high levels of natural water components.
Azzoni, Maria ElenaFranchi, Federico SaschaUsberti, NicolaNasello, Nicole Daniela...
9页
查看更多>>摘要：A new dual layer monolithic AdSCR system (adsorption + selective catalytic reduction) constituted by Cu/CHA (top) and BaO/Al2O3 (bottom) was prepared and studied as a potential solution to improve the low-T performances of NH3-SCR catalysts. Two washcoat formulations were considered. The samples were characterized through optical microscopy and SEM-EDX; the ammonia storage capacity and the catalytic activity in the standard NH3-SCR reaction were also studied. When using water as solvent during the deposition, migration of Ba into the Cu-zeolite layer was observed, resulting in a decay of both ammonia storage capacity and NH3-SCR activity. On the other hand, when water was replaced by n-butanol, the two layers were well segregated, and no loss of SCR performances was noted. The butanol-based formulation exhibited promising performances in the NOx abatement during cold-start transients, with a NO removal efficiency of 31%, prior to ammonia injection, and of 52% after ammonia injection.
查看更多>>摘要：By doping 1%Ru/m-ZrO2 with sodium, selectivity tuning between CO and CH4 during CO2 hydrogenation was achieved by controlling the relative rates of reverse water-gas shift and CO methanation. By increasing basicity through Na loading: (1) the formate C-H bond is weakened in DRIFTS of adsorbed CO, accelerating C-H bond formation of formate and promoting CO formation at the Ru/m-ZrO2 interface; and (2) the coverage of Na increases on ensembles of Ru atoms responsible for methanation. Increasing Na content shifts selectivity from CH4 (useful for synthetic natural gas) to CO, which can be used for Fischer-Tropsch synthesis or methanol-to-gasoline. Electronic modification of formate is likely due to enhanced basicity (strengthening bonding between catalyst and the-CO2 function of formate and weakening C-H). No electron transfer from Na to Ru was detected in XANES. DRIFTS as a function of time and XPS results showed that Na exacerbates site blocking and deactivation.
查看更多>>摘要：Designing atomically dispersed non-precious metal catalysts for 2e(-) oxygen reduction reaction (ORR) is an appealing strategy to harness O-2-to-H2O2 chemistry. Nevertheless, prevailing M-N-C single-atom catalysts (SACs) might still not satisfy the directional regulation of ORR selectivity, hence fail to uphold scalable H2O2 electrosynthesis with a high yield. Herein, we report the precise synthesis of (O,N)-coordinated Fe SAC (FeN2O2) and relating investigation of its performance in H2O2 production over a wide pH range, in comparison with the FeN4 counterpart. Density functional theory simulations reveal that the coordination chemistry engineering has a profound influence on the strength of the oxygen intermediate adsorption. The electron delocalization of M-O configuration readily lowers the d-band center of the Fe metal, which is beneficial to weakening the intermediate adsorption capability and promoting the 2e(-) ORR process. The thus-derived FeN2O2 exhibits impressive selectivity in a wide pH range, particularly reaching 95% in alkaline conditions. Furthermore, our designed gas-diffusion electrode enables a favorable H2O2 yield (300 mmol L-1) at a current density of 60 mA cm(-2) for 50 h. This work is anticipated to inspire the rational design of definitive SAC architecture for practically feasible electrochemical production of H2O2 toward environmental remediation.
查看更多>>摘要：Here, we present a new preparation strategy for hollow SAPO-34 with hierarchical porous structures using rice husk as a sole silicon source and porous template (viz., bio-SAPO-34). The hollow feature and acidity amount of the bio-SAPO-34 were highly dependent on the amount of rice husk in the synthetic solutions. The bio-SAPO-34 exhibited very high olefin selectivity (94.5 %) in the methanol-to-olefins reaction. Bifunctional catalysts con-sisting of ZnZrOx and bio-SAPO-34 were fabricated for the direct conversion of CO2 to light olefins. The C-2(=)-C-4(=) selectivity of 83 % and C-2(=)-C-4(=) space-time yield of 6.14 mmol g(cat)(-1) h(-1) was achieved with only 1 % undesired CH4 at 13.8 % CO2 conversion. Particularly, the CO selectivity from the reverse water-gas shift reaction was sup-pressed to a low value (40 %). Furthermore, the in-situ DRIFTS result indicates that CH3O* is the key interme-diate forming on the ZnZrOx surface and transferring to the Bronsted acid site of bio-SAPO-34 for selective C-C coupling.
查看更多>>摘要：Hydrogen evolution reaction (HER) in alkali involves higher energy barriers and slow reaction kinetics due to involving water dissociation process. Catalysts with proper surface properties are highly needed to optimize the surface binding energy with reaction intermediates and enhance intrinsic catalytic activity. Herein, we present an effective strategy to construct a self-standing catalyst with core-shell structure, which is composited of metallic Co nanoparticles coated by RuCo alloy layer with optimized surface properties. The Ru attracts electrons from Co and optimizes the surface electronic structure. Theoretical calculations demonstrate that the water dissociation barrier on the Co surface is decreased from 0.65 eV to 0.58 eV after alloying with Ru. Experimental results reveal that the synthesized Co@RuCo-3 features highly efficient catalytic activity together with good stability at large current densities for HER in alkali, as well as in alkaline seawater and pure seawater.
查看更多>>摘要：Developing sulfur resistant and stable hydrogenation catalysts with a high activity is of great economic and environmental interest for the production of value-added fine chemicals, as it allows the use of crude industrial level raw materials as reactant, prevents environmental unfriendly stoichiometric reduction and cuts down energy-intensive separation/purification procedures. Here we show the metallic Ni nanoparticle well-enclosed in multilayer N doped graphene shells for the catalytic hydrogenation of nitrobenzene derivatives. The nickel core promoted multilayer N doped graphene shell not only maintains the hydrogenation ability but also create a differentiate surface electronic state preventing the poisoning of vulnerable metal by S impurities. The catalytic performance has met the product requirement of hydrogenation of industrial raw materials including 4.00 wt% inorganic/organic sulfur poisoning substances, excessive acid residue and concentrated salts.
查看更多>>摘要：Catalytic methanol production from CO2 hydrogenation at a lower temperature is limited, predominantly constricted by sluggish reaction kinetics. In this work, a ceria-modified Cu/ZnO/Al2O3 catalyst (CuZnCe-Al) is fabricated which delivers efficient low-temperature methanol production (yield= 822 g/kg(Cu)/h and selectivity = 94% at 225 C and 20 bar) under light illumination. The influence of ceria loading on the morphology/microstructure, interfacial features, and surface chemistry of a Cu/ZnO-based catalyst is systematically assessed. Incorporating ceria (<= 10 at%) into ZnO initially forms ZnO/CeOx interface which promotes both CO2 chemisorption and the formate-pathway which favours methanol production over CO. Increasing the ceria loading beyond 10 at% invoked a Cu/CeOx-dominated structure, leading to over-stabilisation of the surface reaction species and a decreased preference for methanol. The photo-enhancement factor observed for each CuZnxCey catalysts is largely independent of the ceria loading, implying that ceria inclusion imposed little influence on the Cu-ZnO interfacial characteristics.
NSTL
Elsevier