查看更多>>摘要：Glycerol dry reforming (GDR) was studied on Ru/La2O3, Ru/ZrO2, and Ru/La2O3-ZrO2 catalysts. Impacts of the support on morphological, electronic and surface chemical properties of the catalysts were comprehensively characterized by TEM, in-situ DRIFTS, XPS, ATR-IR and XRD. Initial (5 h) CO2 conversion at 750 C and CO2-to-glycerol ratio of 1-4 was ordered as Ru/La2O3 < Ru/ZrO2 < Ru/La2O3-ZrO2. During 72 h stability tests, Ru/ZrO2 deactivated by ~33% due to Ru sintering, structural deformation of the monoclinic zirconia support, and strong metal-support interaction. Under identical conditions, CO2 conversion on Ru/La2O3 decreased by 27% mainly due to dehydroxylation/carbonation of lanthana and severe coking. Lanthana-stabilized tetragonal zirconia phase of Ru/La2O3-ZrO(2 & nbsp;)led to finely dispersed small oxidic Ru clusters which deactivated by 15% after 72 h and demonstrated unusually high catalytic performance that was on par with the significantly more expensive Rh-based catalysts, which are known with their exceptional activity and stability in GDR.
查看更多>>摘要：One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60-70 degrees C under 10-29 bar hydrogen pressure. A rela-tively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71-76% and 72-74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 degrees C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accu-mulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N-2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
查看更多>>摘要：Supported single atom and cluster catalysts have received an extensive attention in all kind of heterogeneous catalytic reactions due to their unique physical and chemical properties. In this work, we prepared silica-supported copper-bismuth oxide catalysts via incipient-wetness impregnation method. This Bi-doped catalyst exhibits an excellent performance in carbon monoxide oxidation with a reaction rate at 0.6 mu mol(CO).(-1)(gcat).s(-1) at 170 degrees C, which is about ten times of that for pure copper-silica catalyst. Furthermore, we found a unique active site structure: Bi single atom anchored on the surface of CuOx cluster via Bi-O-Cu structure with the help of comprehensive characterization method, especially aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and extend X-ray absorption fine structure (EXAFS) fitting result. On one hand, the Bi-O-Cu structure can significantly enhance the anti-sintering ability of copper species and provide more available Cu active site with similar apparent activation energy (similar to 40 kJ.mol(-1)). On another hand, this structure not only increases surface active oxygen species confirmed by CO-temperature programmed reduction (CO-TPR), but also significantly strengthens the adsorption of CO molecule by CO-temperature programmed desorption (CO-TPD) and in-situ Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) to promote the activity of CO oxidation. This work may provide a new guideline to synthesize high active atomic-scale catalysts for different redox reactions.
Park, HyojeongOh, JinhoThanh-Binh NguyenLee, Jung Kyoo...
9页
查看更多>>摘要：The potential uses other than fuels for heavy oil by-products, such as light cycle oil (LCO) from fluid catalytic cracking, has to be developed owing to environmental issues. Herein, we report the hydrogen storage and release characteristics of simulated light cycle oil (Sim-LCO) studied by hydrogenation and dehydrogenation, respectively, over a platinum catalyst. The H2 storage/release behaviors of Sim-LCO were compared to those of the toluene/methylcyclohexane pair and equilibrium conversions. The aromatics in Sim-LCO showed lower turnover-frequencies and higher activation energies than toluene for hydrogenation. However, the 2-ring aromatics showed a higher H2 storage capacity than toluene. Sim-LCO could store H2 at its theoretical capacity (5.27 wt%), and release H2 at > 5 wt% during dehydrogenation. Therefore, LCO is a potential low-cost H2-lean liquid organic hydrogen carrier. However, the dehydrogenation activity of the platinum catalyst should be improved when the equilibrium conversion is considered.
查看更多>>摘要：To develop efficient Pd/SnO2 catalysts with ultra-low Pd loadings for toluene combustion, nano-rod (SnO2-R) and nano-particle (SnO2-P) supports have been intentionally prepared. SnO2-P has a much larger surface area and lower crystallinity than SnO2-R, hence possessing richer surface-active O22- and O2- sites. HRTEM and XPS demonstrate that only Pd2+ is formed on Pd/SnO2-P. In contrast, a considerable amount of Pd0 is formed besides Pd2+ over Pd/SnO2-R, which is highly effective to adsorb/activate both toluene and O2 molecules. It was discovered that surface Pd0 plays a more critical role than the active oxygen sites. Therefore, Pd/SnO2-R demonstrates much higher activity than Pd/SnO2-P at the same Pd loading. With SnO2-R support, 9 times less Pd could be used to get a catalyst with rival activity than with SnO2-P. The reported results might shed some new lights for people to design highly efficient catalysts with ultra-low noble metal contents.
查看更多>>摘要：Electrocatalytic nitrate reduction to ammonia (NH3) has been received increasing attention due to the potential of both decontaminating nitrogen oxide (NOx) from industrial exhaust gas and providing an option for NH3 synthesis. However, their related catalytic process and mechanism dominated by the active phase structure and active sites of nitrate to ammonia electrocatalyst still remain unclear. To this end, in this study TiO2 nano materials with constructed hetero-phase junctions and oxygen defects were used to study the catalytic mechanism and make a clear of the function of hetero-phase junctions and defects. Combined with EPR and FT-IR methods, oxygen defects acted as the adsorption sites of NO3- are experimentally confirmed. Systematic characterizations further demonstrate that enhanced performance with the highest NH3 Faradaic efficiency (78.0%) and selectivity (81.9%) for NITRR can be attributed to the Ti3+- Odef pairs and hetero-phase junctions induced strong interface interactions between anatase and rutile phases. The online differential electrochemical mass spectrometry (DEMS) and density functional theory (DFT) calculations demonstrate that both Ti3+ Odef pairs and hetero-phase junctions lead to the decrease of adsorption energy of NO3-& nbsp;and promote the formation of *NOH intermediates, revealing the reaction mechanism for NH3 synthesis from NO3-.
查看更多>>摘要：In view of the highly demanding in heterogeneous catalysts with intensive activity and stability in AOPs based water pollution treatment, a magnetically separable Cu-0-Fe3O4@Biochar composite was prepared by citric acid combustion method and utilized to remove bisphenol A (BPA) in aqueous solution at a broad pH range via activation of peroxymonosulfate (PMS). A remarkable synergetic effect was observed between Cu-0-Fe(3)O(4 & nbsp;)and Biochar. 5 mM NaHCO3 could increase the stability of Cu-0-Fe3O4@Biochar(65%) and catalytic activity as well. Indicating by EPR and quenching experiment results, singlet oxygen which may come from the lattice oxygen of the composite based on XPS analysis was the main active species in the degradation system other than hydroxyl radicals and sulfate radicals. In accordance with the degradation efficiency results, electrochemical analysis verified that the capability of electron transfer was enhanced markedly once coupling Cu-0-Fe(3)O(4 & nbsp;)and Biochar. The acute and chronic toxicities of intermediates produced were evaluated indicating dramatic reduction in toxic.
Kharlampidi, Kharlampii E.Tuntseva, Svetlana N.Stoyanov, Oleg, VTereshchenko, Konstantin A....
13页
查看更多>>摘要：The effect of Zn(EH)(2), Cd(EH)(2) and Hg(EH)(2) (EH is 2-ethylhexanoate) on cumene oxidation has been established. The use of these catalysts will make it possible to solve a number of tasks that are relevant for cumene oxidation running under industrial conditions, namely: 1) the task of reducing the oxidation time to achieve the required cumene conversion; 2) the task of increasing cumene conversion regardless of the stage of oxidation compared to non-catalytic oxidation (this will reduce the consumption of the recycle stream in the industrial process); 3) the task of accelerating cumene oxidation even in the absence of an initiator at the initial moment of time; 4) the task of maintaining the selectivity of the process even in the late stages of oxidation at a relatively low concentration of the catalyst. The most appropriate catalyst for industrial use is Cd(EH)(2) because ROOH.Cd(EH)(2) intermediate adduct decomposes most rapidly into free radicals.
查看更多>>摘要：The effective dissociation of biomass-derived formic acid, as a sustainable hydrogen source, in water is explored for the hydrogenation of levulinic acid (LA) and quinoline. Ru decorated carbon nanoflakes prepared by car-boreduction (in Ar/H-2 atmosphere) of Ru containing N-doped carbon were used as catalysts. The successful formation of Ru-decorated N-doped carbons was confirmed by numerous spectroscopic tools. The catalyst exhibited outstanding activity and selectivity for the hydrogenation of LA and quinoline using formic acid as a hydrogen donor in water under mild conditions. The catalyst afforded 99.8% LA conversion and 100% selectivity for gamma-valerolactone (GVL), whereas 99.8% quinoline conversion and 93% selectivity for 1,2,3,4-tetrahydroquino-line (THQ) were obtained. Recycling experiments suggested that the catalyst was stable even after the 5 cycles. Various controlled experiments and characterizations were conducted to demonstrate the structure-activity relations and suggest plausible reaction mechanisms for the hydrogenation of LA and quinoline. The exploration of formic acid as a sustainable H-2 source and the development of metal decorated N-doped carbons for hydrogenation of LA and quinoline will be fascinating to catalysis researchers and industrialists.
查看更多>>摘要：A series of Nb-based catalysts with different acid types of carriers (TiO2, Beta molecular sieve, and CeO2) were synthesized. In the catalytic oxidation of dichloromethane (DCM), Nb/CeO2 exhibited the best catalytic activity, resistance to chlorine poisoning/carbon deposits, and stability, due to the abundant acid sites and appropriate ratio of Lewis to Bronsted acid sites on the surface. Both Lewis and Bronsted acid sites could participate in the breakdown of C-Cl bonds, whereas the former exerted a greater influence. The Bronsted acid sites participated in the desorption of Cl species, and were prone to the generation of carbon deposits. The chlorine species easily accumulated at the Lewis acid sites of Nb/TiO2(containing predominantly Lewis acid sites), formed metal chlorides, and caused chlorine poisoning. Carbon deposits made it difficult for Nb/Beta (containing predomi-nantly Bronsted acid sites) to maintain long-term activity. Additionally, the acid sites generated by the active component were more important for DCM degradation than those generated by the carrier.
NSTL
Elsevier