Low-temperature CO oxidation over CuO-CeO_2/SiO_2 catalysts:Effect of CeO_2 content and carrier porosity

The effects of CeO2 contents and silica carrier porosity with their pore diameters ranging from 5.2 nm to 12.5 nm of CuO-CeO2/SiO2 cata-lysts in CO oxidation were investigated.The catalysts were characterized by N2 adsorption/desorption at low temperature,X-ray diffraction （XRD）,temperature-programmed reduction by H2 （H2-TPR）,oxygen temperature programmed desorption （O2-TPD） and X-ray photoelectron spectroscopy （XPS）.The results suggested that,the ceria content and the porosity of SiO2 carrier possessed great impacts on the structures and catalytic performances of CuO-CeO2/SiO2 catalysts.When appropriate content of CeO2 （Ce content 8 wt%） was added,the catalytic activity was greatly enhanced.In the catalyst supported on silica carrier with larger pore diameter,higher dispersion of CuO was observed,better agglomeration-resistant capacity was displayed and more lattice oxygen could be found,thus the CuO-CeO2 supported on Si-1 showed higher catalytic activity for low-temperature CO oxidation.

Ni/MgO catalyst prepared using atmospheric high-frequency discharge plasma for CO_2 reforming of methane

A new type of Ni/MgO catalyst was prepared using atmospheric high-frequency discharge cold plasma. The influences of conventional method, plasma method, and plasma plus calcination method on the catalytic activity were studied and the CO2 reforming of methane was chosen as the probe reaction. The catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, X-ray photoelectron spectroscopy, and CO2 temperature-programmed surface reaction techniques. The results suggested that the nickel-based catalyst prepared by plasma plus calcination method possessed a smaller particle size and a higher dispersion of active component, better low-temperature activity and enhanced anti-coking ability. The conversion of CO2 and CH4 was 90.70% and 89.37%, respectively, and the reaction lasted for 36 h without obvious deactivation under 101.325 kPa and 750°C with CO2/CH4 = 1/1.

Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.

Promoter effect of La2O3 on gold catalyst with different textural structures

Silica supported gold nanoparticles were synthesized and promoted by lanthanum oxide as dopant. The influences of LaOand silica textural structure on the gold dispersion, formation of active species, crystalline composition and the reacting role of dopants were studied in detail. The characterization results suggested that the dispersion of gold nanoparticles depended on the textural structure of silica without lanthanum oxide doping where small mesopores are more preferable to disperse gold nanoparticles. The addition of lanthanum oxide largely increased the dispersion of gold nanoparticles and oxygen active sites independent of the textural structure of silica support. The interaction between lanthanum oxide and silica enhanced by the synergy facilitated the release of oxygen vacancies and transition of active oxygen species. In addition, the chemical properties were greatly changed after lanthanum oxide addition which was only inconspicuously impacted by the initial textural structure of silica supports, shedding light on the further design of economic gold catalyst based on simple synthesis method.

Tuning redox activity through delithiation induced protective layer and Fe-O coordination for Li-rich cathode with improved voltage and cycle performance

Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycling,which are associated with the surface oxygen release and accompanied by cation densification and structural collapse.Herein,an integrative approach of simultaneous constructing uniform 3d Fe-ion doping in the transition metal layer and Li-rich Li_(5)FeO_(4) shell to grab the oxygen and prevent interfacial side reactions is proposed.The introduction of Fe induces higher redox potential and stronger 3 d Fe-O_(2)p covalent bond,triggering reversible anionic redox via a reductive coupling mechanism.And the delithiated product of Li-rich Li_(5)FeO_(4) not only acts as a protective layer alleviating the side reactions but also enhances the surface kinetic property.With the benefit of promoted reversibility of oxygen redox and enhanced surface stability,the cathode exhibits high reversible capacity and superior cycle performance.Density function theory calculation indicates that the O_(2)p non-bonding state in the cathode incorporated with Fe sits at a lower energy band,resulting in higher energy storage voltage and improved oxygen stability.Consequently,the modified cathode exhibits a discharge specific capacity of 307 m A h g^(-1)(1 C=250 m A g^(-1)),coulombic efficiency of 82.09%in the initial cycle at 0.1 C and 88.34%capacity retention after 100 cycles at 1 C.The work illustrates a strategy that could simultaneously enhance oxygen redox reversibility and interface stability by constructing lattice bond coordination and delithiation induced protective layer to develop Li-rich materials with high reversible capacity and long lifespan.

地球多层圈有机—无机相互作用的资源效应

地球内部不同层圈相互作用过程中的物质循环和能量传递对浅层盆地内部多种类型资源的形成及富集具有显著影响。深部地质作用过程与浅部资源效应这一核心科学问题备受关注,其中在深部流体/熔体物质传输影响下的有机—无机相互作用及资源效应是关键所在。梳理了地球多层圈有机—无机相互作用对盆内多种资源的影响机理。在深部流体/熔体活动背景下,有机—无机相互作用主要通过形成利于富有机质烃源岩发育的沉积环境、提供促进生烃的物质能量、产生改造储层性质的流体环境和影响油气组分的聚集效果的方式控制油气资源的形成和聚集;深部流体携带地球深部的气体组分(CH_(4)、H_(2)、CO_(2)等)和热能进入盆地促使了天然氢气和地热资源潜力的形成;深部物质为铀矿提供铀源,富铀流体在生物作用和含烃流体作用下形成砂岩型铀矿;深部流体活动对煤矿资源的形成和变质也产生了较大影响。未来针对地球多层圈有机—无机相互作用的研究应当突破盆地限制,在地球系统的背景下围绕层圈物质和能量传输、盆内与盆外一体化展开。重点对非生物烷烃气成因、工业聚集和天然富(含)氢气藏的成因、富集、潜在勘探区评价、地质储存开展深入研究,助力推进中国能源转型和绿色发展。

地质超临界二氧化碳热液挥发分对碳氢化合物向杂环化合物的转化作用

In order to assess the dynamics of molecular conversion,scientists simulated the low-temperature synthesis of polycyclic aromatic hydrocarbons(PAHs)in Titan’s atmosphere[1],and noticed the transformation(hydrogenation,oxygenation,and hydroxylation to complex molecules)of PAHs under interstellar medium conditions.Geological hydrothermal systems have also drawn attention as potential key sites for various organic synthesis and transformation reactions[2,3].Thus the formation of abiotic CH4[4],which has proven to be an important component of deep hydrothermal fluids that are generated outside the temperature regime envisaged for thermogenic gases,have long been reported in a range of global hydrothermal sites,including mid-ocean ridges,continental rifts,pre-orogenic and subduction zones,back-arcs,hot springs,and volcanically-active areas.These transformation processes have been suggested to occur at the water–mineral interface.There is compelling evidence for the generation of C-H chain molecules from inorganic chemicals via abiotic reactions(e.g.,Fischer-Tropsch synthesis of CH4)in laboratory and field studies[5,6].However,a huge gap remains in the understanding of carbon and hydrogen evolution and heterocyclization from C-H chain molecules to complex heterocyclic materials and then possible hydrophobic or hydrophilic macromolecules,and the corresponding reaction mechanism(s).The occurrence of abundant and complex heterocyclic molecules formed through abiotic processes is rare in natural regions associated with deep fluid movement and activity。

Effect of Fe content on FeMn catalysts for light alkenes synthesis

The effect of Fe content on FeMn/MgO catalysts for light alkenes synthesis through CO hydrogenation was investigated.Catalysts were prepared by a conventional co-impregnation method,characterized using BET,X-ray powder diffraction(XRD)and Temperature-programmed reduction(H_(2)-TPR)techniques.High activity was obtained over the catalyst with 9 wt-%Fe content,over which CO conversion and the selectivity of C2^(=)-C4^(=)reached 91.36%and 58.48%,respectively.With the increase of Fe content,both the conversion and the selectivity were improved within a certain range and then decreased.The results show that the surface area of the catalyst played an important role in the catalytic reaction.With the increase of Fe loading,the interaction action between Fe and Mn was enhanced and FeMn solid solution was formed.