Acetone hydrogenation in exothermic reactor of an isopropanol–acetone–hydrogen chemical heat pump: effect of intra-particle mass and heat transfer

Intra-particle mass and heat transfer plays an important role in performance of the exothermic fixed-bed reactor for an isopropanol-acetone-hydrogen chemical heat pump. In this work, an exothermic fixed-bed reactor model, taking into account the actual packing structure, is established in the commercial software Fluent. A 120° segment of a tube with tube-to-particle diameter ratio （n） of 4, where realistic particles are packed and set to porous media, is used to simulate the 3D external flow, concen- tration and temperature fields in the exothermic packed-bed reactor. The influence of catalyst particle diameter （dp） and micropore diameter （do） on the intra-particle temperature, species distribution, reaction rate and selectivity is dis- cussed. The appropriate dp and do are obtained. Simulation results showed that intra-particle temperature gradient is not obvious. Large dp and small do lead to remarkable gradient of reaction rate inside the catalyst particle and the decrease in the catalyst efficiency and reduce the acetone conversion and the selectivity in isopropanol. The optimal results reveal that the spherical catalyst with dp of 1 mm and dpore of 10 nm is appropriate for high-temperature acetone hydrogenation.     

热处理温度对溶胶-凝胶法制备的Ce_(0.97)Co_(0.03)O_2薄膜结构和光学性能的影响

采用溶胶-凝胶法,在Si(100)衬底上制备了3%Co掺杂CeO2薄膜,研究了不同热处理温度对Ce0.97Co0.03O2薄膜结构和光学性质的影响。X射线衍射(XRD)表明,3%Co掺杂CeO2薄膜为多晶薄膜,且未破坏CeO2原有的结构,随着退火温度的升高,晶粒尺寸逐渐增大。椭偏光谱法研究表明,Ce0.97Co0.03O2薄膜的光学常数(折射率n、消光系数k)随着退火温度增加而增大,光学带隙Eg随退火温度增加而减小,这是薄膜结构随退火温度增加发生变化所致。     

Microstructure and mechanical properties of TiAl/TiAl joints brazed with a newly developed Ti–Ni–Nb–Zr quaternary filler alloy

A novel Ti-Ni-Nb-Zr quaternary filler alloy with the composition of Ti-(19～25)Ni-(15～25)(Nb+Zr)(wt.%) was designed.The filler alloy was composed of(Ti,Nb)ss,(Ti,Zr,Nb)ss+(Ti,Zr)₂Ni,α-Ti and Ti₂Ni phases.It was fabricated into filler foil with a thickness of about 45 μm by a rapid solidification technique.The results indicate that the liquidus temperature of the Ti-Ni-Nb-Zr brazing alloy was about 978℃,and the brazing alloy presented excellent wettability on TiAl substrate.T...     

Hydrogen production by reforming methane in a corona inducing dielectric barrier discharge and catalyst hybrid reactor

A novel corona inducing dielectric barrier discharge(CIDBD) and catalyst hybrid reactor was developed for reforming methane. This corona inducing technique allows dielectric barrier discharge(DBD) to occur uniformly in a large gap at relatively low applied voltage.Hydrogen production by reforming methane with steam and air was investigated with the hybrid reactor under atmospheric pressure and temperatures below 600°C.The effects of input power,O2/C molar ratio and preheat temperature on methane conversion and hydrogen selectivity were investigated experimentally.It was found that higher methane conversions were obtained at higher discharge power,and methane conversion increased significantly with input power less than 50 W;the optimized molar ratio of O2/C was 0.6 to obtain the highest hydrogen selectivity(112%);under the synergy of dielectric barrier discharge and catalyst,methane conversion was close to the thermodynamic equilibrium conversion rate.     

CeO2 thin films grown on biaxially textured nickel (001)

CeO\-2 films have been grown on biaxially textured Ni substrates at various temperatures. The results show that CeO\-2 films without IBAD are dominated by (111) orientation from room temperature to 800℃ while the preferential orientation of CeO\-2 films with IBAD is (001) at lower deposition temperature and (111) at deposition temperature higher than 450℃. CeO\-2 films with better in_plane texture and out_of_plane orientation can be grown at 360℃ with 240 eV ion energy and 200 μA/cm\+2 ion current density.     

CeO2包覆TiO2的XPS研究

Redox capacity of CeO₂ coating TiO₂ is discussed.It is showed that CeO₂ is easy to be reduced and can be re-oxidized while expoursing O@fs(50)2@fs(100).Due to Ti⁴⁺ mixed in the CeO₂ lattice,the activation energy decrease,which attributed to oxygen vacancy migration.     

条形高Ni/γ-Al2O3在甲苯气相加氢中的催化性

研究浸渍法制备的条形负载型高Ni含量的Ni／Al2O3催化剂及其与压片法制备催化剂在甲苯气相加氢中的催化活性的对比，并研究了氢压、反应温度、氢油比和空速对甲苯转化率的影响。在微反评装置上进行了1200h的稳定性试验。结果表明：浸渍法制备的条形高Ni／Al2O3催化剂对甲苯加氢反应具有很高的催化活性和良好的寿命。     

Au/CexZr1-xO2催化剂在高浓度CO室温催化氧化中的活性

 以柠檬酸溶胶凝胶法制备的铈锆氧化物为载体,采用沉积-沉淀法制备了Au/Ce_xZr_1-xO₂催化剂.探讨了载体组成、焙烧温度、金担载量对该催化剂催化氧化一氧化碳性能的影响,并对催化剂进行XRD表征,优化了制备条件.结果表明:当载体为Ce_0.75Zr_0.25O₂,焙烧温度为550℃,金担载量为4.7%的催化剂在室温下催化氧化CO的效果最好.该催化剂的优点是具有较强的耐水性;在用量少,一氧化碳浓度高的条件下仍能氧化CO₃0%~40%左右.     

Microstructure evolution and mechanical properties of Ti_2AlNb/TiAl brazed joint using newly-developed Ti–Ni–Nb–Zr filler alloy

Joining of Ti_2AlNb alloy to TiAl intermetallics was conducted by the newly-developed Ti–Ni–Nb–Zr brazing filler alloy.The microstructure evolution of the joints was investigated by scanning electron microscope (SEM),energy dispersive spectrometer (EDS) and electron backscatter diffraction (EBSD).The macro-micro mechanical properties were studied by shear test and nano-indentation test.Typical interfacial microstructures across the brazing seam were Ti_2AlNb substrate,α_2-Ti_3Al+β-Ti,γ-TiAl+Ti_2Ni+TiNi+α_2-Ti_3Al,α_2-Ti_3Al+β-Ti,TiAl substrate.The Ti_2Ni phase were firstly dissolved in the joints brazed at 1000°C for 10 min and then precipitated after a prolonged holding time of 15 min.The nano-indentation test revealed that Ti_2Ni phase exhibited the highest hardness of 12.60 GPa.The joints brazed at 1000°C/15 min presented the maximum shear strength of271 MPa.The dissolution and precipitation behavior of Ti_2Ni phase was also discussed.     

Surface chemical structure of titania-silica nanocomposite powder

Titania-silica （TS） nanocomposite powder with three different composite structures, containing 10-30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray photo-emission spectroscopy （XPS） and high resolution transmission electron microscopy （HRTEM）. The study for all TS oxides annealed at 773 and 1173 K showed： an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti^3＋, Ti^2＋, Si^3＋ and Si^2＋ oxides coexisted with Ti^4＋ and Si^4＋ oxides, and the contents of these Ti/Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chem-adsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indicated that the surface of TS oxide powder derived by sol-gel process was a double layer with enriched O first and then SiOx/TiOy（x, y〈2）. Ti/Si suboxides could result from the thermal diffusion of Ti^4＋ and Si^4＋, which might be induced by the strong interaction between Ti^4＋ and Si^4＋.     

非晶态Ni-B/SiO_2催化硝基苯加氢及其晶化失活

采用化学还原法制备了负载型Ni－B/SiO2非晶态合金催化剂,采用高压液相硝基苯的加氢反应,测定了上述催化剂的加氢活性和选择性,并与其他Ni系催化剂（Ni／SiO2和RaneyNi催化剂）进行了比较,发现所有催化剂均具有很高的催化活性和选择性,而Ni－B／SiO2非晶态合金的催化活性和选择性最高．通过高温处理获得对应的晶态Ni－B／SiO2催化剂,Ni－B／SiO2非晶态合金的加氢活性明显高于对应的晶态催化剂,表明催化剂存在晶化失活现象,结合催化剂的表征,讨论了非晶态合金催化剂的晶化失活机理,主要归因于高温团聚导致催化剂活性比表面积下降．     

氧化铈纳米粒子的制备及其生物应用进展

由于铈离子可以在Ce~(3+)和Ce~(4+)之间可逆转换,以及氧空位的存在,氧化铈(CeO_(2-x),x=0～0.5)纳米粒子具有优异的催化特性,作为一种用途广泛的稀土氧化物得到了广泛的关注.Ce原子能够快速而大幅度地调整其电子结构(如产生氧空位或缺陷),以最佳的结构适应其周围环境,具有多种酶类活性(包括超氧化物氧化酶、过氧化氢酶和氧化酶等),可以清除体内产生的各种毒性活性氧.氧化铈在生物分析、生物医学、药物传递和生物支架等生物领域展现出了良好的应用前景.综述了氧化铈的制备方法及其在生物领域的应用进展.     

Present status and future prospect of design of Pt–cerium oxide electrodes for fuel cell applications

In the research field of proton exchange membrane fuel cells, the design of electrocatalytic activities on Pt-oxide promoter in the anode side has attracted attention for improvement of CO tolerance of Pt in anode side and a lowering of large over-potential loss of the oxygen reduction reaction on the cathode in the fuel cells. In the Pt-oxide promoter series, Pt–CeOx/C is one of the unique systems. It is because the unique behavior of CeOx such as electrochemical redox reaction between Ce3t and Ce4t in the anodic and cathodic reactions of fuel cell is observed. The present short review gives an overview of the recent works for improvement of the CO tolerance of Pt in the Pt–CeOx/C anodes and enhancement of the oxygen reduction reaction activity on Pt in the Pt–CeOx/C cathodes for fuel cell application. To show the design paradigm for fabrication of high quality Pt–CeOx/C electrodes, the authors re-introduced parts of our research results to highlight the important role of interface structure of Pt–CeOx based on the ultimate analysis results. The usefulness of the combined approach of microanalysis and the processing route design is presented.     

一种负载型镍基催化剂上糠醇液相加氢制四氢糠醇的实验研究

针对自制的负载型镍基催化剂,详细研究了糠醇选择催化加氢制备四氢糠醇的反应行为,考察了反应温度、压力、催化剂载量和搅拌速率等诸因素对催化性能的影响规律,进而得到糠醇加氢制备四氢糠醇的适宜操作条件(反应温度170℃、氢气压力4.0MPa、搅拌速率1200r/min、催化剂载量20g/L),此外还浅析了催化剂重复使用情况,为催化剂的工业化应用提供了依据。     

衣康酸加氢制备甲基丁二酸

间歇式应釜中,采用骨架Ni催化剂,对衣康酸加氢制备甲基丁二酸的工艺条件进行了研究,探讨了溶剂、反应时间、反应温度、催化剂用量及循环次数对加氢反应的影响。结果表明,最佳反应条件为：甲醇为溶剂,反应时间为60min,反应温度为50℃,催化剂质量分数为10％,此时,衣康酸转化率为99．14％。催化剂循环使用5次后,衣康酸转化率仍在95％以上。采用傅里叶红外光谱、核磁共振对产物的结构进行了分析。     

CuO/CeO2催化剂在温度变动过程中的CO-PROX催化性能

采用浸渍方法制备不同Cu/Ce原子比的CuO/CeO₂催化剂,用于富氢气体中CO优先氧化反应(CO-PROX),考察其在温度变动情况下的催化性能. 利用X射线衍射(XRD)、程序升温还原(TPR)方法对反应前后催化剂样品进行了表征. XRD测试表明,催化反应后的催化剂中有金属Cu0生成. 这与文献结果一致. 与不含CO₂的情况比较,当模拟富氢气体中含有CO₂时,低温段催化活性明显下降. Cu/Ce原子比为10%的催化剂在温度变动过程中具有较稳定的催化性能.      

Annealing crystallization and catalytic activity of ultrafine NiB amorphous alloy

Annealing crystallization of ultrafine NiB amorphous alloy prepared by the chemical reduction method was studied by DTA, XRD and XAFS techniques. The XRD and XAFS results have revealed that the crystallization process of ultrafine NiB amorphous alloy proceeds in two steps. First, ultrafine NiB amorphous alloy is crystallized to form metastable nanocrystalline Ni₃B at an annealing temperature of 325℃. Second, the nanocrystalline Ni₃B is further decomposed into crystalline Ni at 380℃ or higher tempera ture, the local structure around Ni atoms in resultant product is similar to that in Ni foil. It was found that the catalytic activity of nanocrystalline Ni₃B for benzene hydrogenation is much higher than that of ultrafine NiB amorphous alloy or crystalline Ni. The result indicates that the active sites of nanocrystalline Ni₃B for benzene hydrogenation are composed of both Ni and B with proper geometry configuration.     

Formation mechanism of interfacial microstructures and mechanical properties of Ti2AlNb/Ni-based superalloy joints brazed with NiCrFeSiB filler metal

Dissimilar brazing of Ti₂AlNb-based alloy and Ni-based wrought superalloy (GH536) was studied using NiCrFeSiB filler metal. The Ti₂AlNb/GH536 joints were analyzed by scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The formation mechanism of interfacial microstructure and mechanical properties of Ti₂AlNb/GH536 joints were studied. The results indicated that Ti₂Ni(Al,Nb), AlNi₂Ti and TiB₂ reaction layers were formed in the joint adjacent to Ti₂AlNb base metal. These layers resulted in high micro-hardness and the weak link of the joint. γ solid solution was formed through isothermal solidification and β₁-Ni₃Si phase precipitated in the γ solid solution during cooling process. Ni₃B, β₁-Ni₃Si and CrB phases appeared in the centre of the joint. Blocky and needle-like borides formed within the diffusion affected zone of GH536 base alloy. The maximum tensile strength of Ti₂AlNb/GH536 joints reached 425 ?MPa ?at room temperature and the strength value of 373 ?MPa was maintained at 923 ?K.     

Influence of heat exchanger structure on hydrogen absorption-desorption performance of hydrogen storage vessel

The influence of heat exchanger structure on hydrogen absorption-desorption performance of hydrogen storage vessel was studied, in which the AB₅ (La_0.25Ce_0.75Ni_4.4Al_0.1Mn_0.1Co_0.4) hydrogen storage alloy was used as a typical representative. In order to obtain the data on reaction enthalpy, the PCT curve of the alloy was measured with three different temperatures, and the linear fitting was carried out according to the Van't Hoff relation curve. The SMCR (Spiral-mini-channel Reactor) reactor structure was adopted. The heat transfer method and its simplified model were studied by finite element method to explore the effect of size of heat transfer structure, particularly for heat pipe diameter, on the hydrogen absorption-desorption performance of hydrogen storage alloy in the vessel.     

装填不同催化剂甲醇合成器的性能模拟

以CO加氢、CO_2加氢合成甲醇(CH_3OH)反应为关键反应,选取CO、CO_2和CH_3OH为关键组分,建立了某厂年产20万t CH_3OH合成反应器的一维拟均相数学模型,在相同的操作条件下,模拟了分别装填C301、C302、C306、NC309和SC309催化剂时反应器的性能。使用龙格-库塔法求得反应器中温度分布和物料的浓度分布,比较了不同型号催化剂的性能,并讨论了沸腾水温度的影响。