The activity of transition metal nitrides for hydrotreating quinoline and thiophene

An investigation has been conducted of the activity of AlN, BN, TiN, VN, Mo₂N, and W₂N as catalysts for quinoline hydrodenitrogenation (HDN). The activity of Mo₂N and VN for thiophene hydrodesulfurization (HDS) and the concurrent hydrotreatment of quinoline and thiophene have also been examined. Bulk AlN, BN, and TiN were obtained with low surface areas and found to be inactive for the HDN of quinoline. Bulk Mo₂N, W₂N, and VN could be obtained with high surface area. Each of these nitrides exhibited high activity for quinoline HDN, the turnover frequency for this reaction decreasing in the order Mo₂N>W₂N>VN. Highly dispersed VN supported on SiO₂ was found to have a specific activity for quinoline HDN identical to that of bulk VN. Both bulk Mo₂N and 27% VN/SiO₂ exhibit high activity for the HDS of thiophene. The behavior of these two catalysts for the concurrent hydrotreatment of quinoline and thiophene is also discussed.     

金属氮化物/碳化物催化剂加氢性能研究进展

介绍了过渡金属氮化物/碳化物独特的晶体结构和电子性能及其与催化性能的内在联系。综述了过渡金属氮化物/碳化物在涉氢反应中催化加氢机理的研究进展,以及过渡金属氮化物/碳化物在加氢脱硫(HDS)、加氢脱氮(HDN)和其他涉氢反应中的应用。与传统的过渡金属硫化物催化剂相比,过渡金属氮化物/碳化物具有更加优异的氢吸附、活化和转移能力。     

过渡金属氮化物催化性能研究进展

过渡金属氮化物具有类似于Pt族贵金属的催化性能得到了广泛的研究.综述了过渡金属氮化钼及助剂促进的氮化钼在加氢脱硫与脱氮、氨合成与分解、芳烃加氢和其他涉氢反应(如炔烃、烯烃加氢、丙酮缩合、肼的分解)中的应用,并介绍了其他金属氮化物(如氮化钒、氮化钴)在催化反应中的应用.     

On the possibility of obtaining refractory metal nitrides in a calciothermic process

The possibility of obtaining refractory titanium nitride TiN in a calciothermic process is shown. The dependence of the combustion rate and temperature on the nitrogen pressure is studied. The phenomenon of super-adiabatic heating during combustion of the Ca-TiO₂-N₂ system is found.     

Oxygen plasma modification of polyimide webs: effect of ion bombardment on metal adhesion

Webs of Kapton 200-H and Upilex-S polyimide films were treated using oxygen plasma prior to sequential sputter deposition of chromium and copper in a roll metallization system. Two plasma system configurations were employed for treatment. In one configuration, the sample traveled downstream from a microwave plasma; in the other, the web moved through a DC-generated glow discharge. For the DC-glow treatment, the potential difference between the plasma and the web, Φ_f, and relative ion densities, n+, were measured at various values of chamber pressure and DC power using a Langmuir probe. Although samples treated downstream from the microwave plasma were not subjected to bombardment by energetic ions, Φ_f for the DC-glow operating conditions was between 5 and 13 eV. For both films, advancing DI water contact angles of less than 20° were achieved using both modes of treatment. Contact angles for untreated films were greater than 60°. However, 90° peel tests yielded values of 15 to 20 g/mm for microwave plasma treatments and 40 to 60 g/mm for DC-glow treatment. Peel values for untreated Kapton and Upilex films were about 25 g/mm. High-resolution X-ray photoelectron spectroscopy in the C1s region for Kapton film surfaces treated downstream from the microwave plasma showed increases in carbonyl groups, with concentrations inversely proportional to web speed. In contrast, DC-glow modification was due mainly to formation of carboxylates with a small increase in carbonyl component. It is proposed that treatment downstream from the microwave plasma results in formation of a weak boundary layer at the polyimide surface. Ion bombardment occurring in the DC-plasma configuration results in relatively more crosslinking at the polymer surface. Furthermore, adhesion between the sputter-deposited chromium and the DC-glow modified polyimide improved with increasing values of Φ_fn+.     

Characterization of early transition metal carbides and nitrides by NEXAFS

Powder materials of a series of early transition metal (groups 4–6B) carbides and nitrides, including TiC, VC, NbC, Mo₂C, WC, TiN, VN and Mo₂N, have been characterized by nearedge X-ray absorption fine structure (NEXAFS). A comparison of the carbon and nitrogen K-edge features reveals systematic trends in the electronic properties of these materials. These results are compared to an earlier NEXAFS characterization of thin VC films produced on a single crystal V(110) surface. In addition, the NEXAFS data are also compared to existing band-structure calculations for carbides and nitrides of early transition metals.     

The highly selective catalytic hydrogenation of CO2 to CO over transition metal nitrides

Three transition metal-like facet centered cubic structured transition metal nitrides, γ-Mo₂N, β-W₂N and δ-NbN, are synthesized and applied in the reaction of CO₂ hydrogenation to CO. Among the three nitride catalysts, the γ-Mo₂N exhibits superior activity to target product CO, which is 4.6 and 76 times higher than the other two counterparts of β-W₂N and δ-NbN at 600 ℃, respectively. Additionally, γ-Mo₂N exhibits excellent stability on both cyclic heating–cooling and high space velocity steady state operation. The deactivation degree of cyclic heating–cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%. In-situ XRD and kinetic studies suggest that the γ-Mo₂N itself is able to activate both of the reactants CO₂ and H₂. Below 400 ℃, the reaction mainly occurs at the surface of γ-Mo₂N catalyst. CO₂ and H₂ competitively adsorbe on the surface of catalyst and CO₂ is the relatively stronger surface adsorbate. At a higher temperature, the interstitial vacancies of the γ-Mo₂N can be reversibly filled with the oxygen from CO₂ dissociation. Both of the surface and bulk phase sites of γ-Mo₂N participate in the high temperature CO₂ hydrogenation pathway.     

钼助剂对二硝基苯加氢催化剂的改性研究

采用猝冷法制备了Mo修饰的骨架镍催化剂,通过BET、XRD和SEM等手段对催化剂进行表征,研究助剂Mo对骨架镍催化剂组成和结构的影响,确定催化剂制备条件为:催化剂与氢氧化钠质量分数为20%的碱溶液质量比为0.6,80℃投加合金粉,催化剂在二硝基苯加氢反应中选择性和转化率近100%。     

Synthesis of molybdenum nitrides nanosheets by nitriding 2H‐MoS2 with ammonia

Metal nitrides nanosheets possess remarkable physical and chemical properties such as high electrical conductivities, catalytic properties, energy storage, and conversion efficiency. In this paper, molybdenum nitride (Mo₅N₆, MoN, and Mo₂N) nanosheets were synthesized by nitriding and exfoliating the bulk 2H‐MoS₂ via dropping N from ammonia at high temperature. Molybdenum nitride nanosheets with the thickness of dozens of nanometers were prepared successfully under different conditions. It was found that the reaction between MoS₂ and NH₃ began from about 696°C, and reduction products and reaction mechanisms were strongly dependent on the temperature. When there was MoS₂, the generated Mo₅N₆, MoN, and Mo₂N can exist stably at even 820, 1020, and 1120°C, respectively. However, they will decompose progressively after MoS₂ was consumed completely: at 820°C, Mo₅N₆ started to decompose to δ‐MoN; at 1020°C, the phase evolution process of MoN can be described as follows: δ‐MoN→ γ‐Mo₂N→ β‐Mo₂N→ Mo, while at 1120°C, the β‐Mo₂N will transform to Mo.     

载体对负载型过渡金属氮化物催化氨分解性能的影响

采用等体积浸渍法结合NH3程序升温氮化制备出一系列负载型金属Co、Mo氮化物催化剂。并利用XRD、TPD-MS和H2-TPR及氨分解活性测试等手段,考察了载体［Mg(Al)O、MgO和γ-Al₂O₃］对负载型金属氮化物的表面形态及组成的影响。结果表明,（1） 负载催化剂的氨分解速率远远高于非负载的催化剂;（2） 氮的脱附峰可以归为以下三类：a.吸附态的NHx分解;b.氮化物结构转变;c. β-Mo₂N_0.78和Co₂Mo₃Nx 还原成Co和Mo金属;（3） 载体表面的酸碱性和孔结构对其负载的金属氮化物的催化活性和表面形态及化学组成有重要的影响,镁铝复合氧化物MgAlO［n(Al)∶n(Mg)=1∶3］为载体的钴钼双金属氮化物对于氨分解反应具有最好的催化活性。     

介孔炭氧化改性及金属改性研究进展

介孔炭材料由于它本身的优越结构及性能,自合成以来就受到人们的广泛关注.本文综述了国内外对介孔炭材料进行氧化改性处理包括含氧酸氧化改性、过氧化化合物改性、金属盐氧化改性以及金属改性处理的最新研究成果,经过改性的介孔炭具有更高效的吸附、导电、催化等性能,但目前进行氧化改性条件的研究并不成熟,金属改性的应用同样需要进一步探究.     

Hydrotreating of heavy vacuum gas oil (HVGO) on molybdenum and tungsten nitrides catalytic phases

A series of supported and unsupported Mo₂N and W₂N phases were synthesized by means of the treatment under ammonia atmosphere at 700°C of Mo and W oxides. The X-ray diffraction and electron microscopy techniques verified the formation of the Mo₂N and W₂N ceramic phases, while the N₂ adsorption (BET) was used to determine the surface areas, between 46–133 m²/g for Mo₂N (unsupported) and 81–101 m²/g for W₂N (unsupported). The supported phases had surface areas between 109–113 and 109–122 m²/g, for Mo₂N/Al₂O₃ and W₂N/Al₂O₃, respectively. The catalytic hydrotreating of a heavy vacuum gas oil (HVGO) derived from Maya crude (i.e. 2.21 wt.% S, 0.184 wt.% N₂) was performed on both, supported and unsupported Mo nitrides and W nitrides, which promoted the HDN reaction preferentially, up to 26.6% on Mo₂N/Al₂O₃ and up to 22.3% on W₂N/Al₂O₃, against 3.26% on the reference catalyst, i.e. CoMo/Al₂O₃ at 350°C and 80 kg/cm². Also, the rates for HDN increased with the crystallite size in the unsupported W₂N series. Also, the pore volume and mean pore diameters of the Mo₂N/Al₂O₃ and W₂N/Al₂O₃ series improve substantially with respect to the pure ceramic phases.     

Two-dimensional metal carbides and nitrides from head to toe with energy applications: A topical review

An increase in population and demand for energy are the major challenges in today's world. As the Internet of Things (IoTs) grows, there is a pressing need for new kinds of novel materials. These issues greatly attract the scientific community. Therefore, the hottest topic now is energy conversion and energy storage by using two-dimensional (2D) materials beyond that of graphene. In the year 2011, Gogosti et al., and his research team discovered 2D transition metal carbides, nitrides and carbonitrides called MXenes Ti₃C₂T_x etching from Ti₃AlC₂ with the help of toxic hydrofluoric acid. Now, so many novel routes have been developed with mild reducing agents, etchants, and intercalants. Many new members of 2D materials have been added to the constellation. MXene based composites have drawn extensive attention from the scientific community owing to their high conductivity and other unique properties such as hydrophilic surfaces, large interlayer spacing, environmental flexibility, large surface area, safety, thermal conductivity, improved electrochemical activity, enhancing faradic capacitance (pseudocapacitance) and reducing the shortcomings in the normal capacitance etc. In this review, we systematically summarize the recent developments and various synthesis mechanisms of different multi-layered material, intercalations, and its different applications as electrocatalysts, Li-ion batteries (LIBs), supercapacitors, biosensors, and other electrochemical storage systems.     

The influence of a second metal component (Cu,Sn, Fe) on Pd/SiO2 activity in the hydrogenation of 2,4-dinitrotoluene

The catalytic activity of palladium in the hydrogenation of 2,4-dinitrotoluene is reduced by the addition of Cu or Sn. Upon addition of Fe, the activity increases. The formation of highly dispersed Pd-Fe bimetallic aggregates is suggested, where the Fe atoms, contiguous to Pd, act as promoters activating of the N=O bond.     

膨润土的改性及其在重金属吸附中的研究进展

改性膨润土是近年来广受关注的重金属吸附剂。综述了焙烧、酸活化、无机、有机改性等途径对膨润土结构、吸附性能的改善效果,介绍了改性膨润土在重金属吸附处理中的应用情况。结合重金属废水处理的要求,指出了改性膨润土研究和应用中可能取得突破的几个方向。     

Ⅰ效蒸发器液位控制改造

叙述了Ⅰ效蒸发器液位测量所存在的问题并提出了解决方案，新改进的液位测量控制合理、简单、便于维护，投运效果良好。     

第二代丙烯酸酯结构胶的改性研究进展

介绍了第二代丙烯酸酯结构胶(SGA)的研究现状、组成和特点,重点综述了针对其不足之处(如臭味、毒性、储存期、耐水性、耐热性、固化物韧性和耐冲击性等)的改性研究。最后对SGA行业发展的重点(建立完整、合理和经济的工艺流程,拓展应用领域,减少能源消耗和对环境的影响)进行了展望。     

Surface modification of charcoal by glow-discharge: The effect on blood cells

Glow discharge polymerization of hexamethyldisiloxane was carried out on activated charcoal granules through the application of capacitively coupled RF plasma. The coats were examined with Auger and IR spectroscopies, and with SEM. The surface topography and the tenacity of samples coated with plasma were compared with that of the solution-coated ones. Mercury porosimetry was used to study the effect of the coat on pore size distribution. The effect of contact with blood on the number of blood cells were studied.     

Chemical modification of preceramic polymers: Their reactions with transition metal complexes and transition metal powders

Conclusions This research has demonstrated that a variety of chemistries can be carried out with preceramic polymers that in general are characterized by the presence of an abundance of reactive functional groups. Such chemistries can serve to upgrade a given preceramic polymer by catalytic or stoichiometric processes; they can be used to from new and useful hybrid polymers from the original preceramic polymer, as shown in the present work and also in some of our previously published work; they can, by their pyrolysis in the presence of metal powders, act as chemical reagents that deliver the elements of interest for reaction with the metal to give useful ceramics. Thus the preparation of a preceramic polymer is not the end of the chemistry in the monomer-to-polymer-to-ceramic conversion, but rather it presents many possibilities for further chemistry.     

Sintered reaction-bonded silicon nitrides with high thermal conductivity: The effect of the starting Si powder and Si3N4 diluents

Silicon nitride ceramics with high thermal conductivity were fabricated by employing the reaction bonding method. It was revealed that the addition of Si₃N₄ diluents affected both the nitriding reaction and the post-sintering behavior by changing the size of the silicon particle during the milling process. The reduced size of silicon particle led to an increased degree of nitridation. Further, narrower pore channels in the nitrided bodies caused by the reduced size of silicon particle enhanced the final density, by promoting the easier elimination of finer pores during post-sintering. The positive effect of the finer silicon particle was confirmed by a back-up experiment employing a variety of silicon particle sizes, produced by milling the raw silicon powder for different milling times. Thermal conductivity was dominated by material density rather than variation of the microstructure or oxygen content in the current research.