Palladium nanoparticles supported on a poly(N-vinyl-2-pyrrolidone)-modified mesoporous carbon nanocage as a novel heterogeneous catalyst for the Heck reaction in water

Palladium nanoparticles supported on poly(N-vinyl-2-pyrrolidone)/CKT-3 (a mesoporous carbon nanocage) were employed effectively as novel heterogeneous catalyst for the Heck coupling reaction. The results showed that aryl halides (-Cl, -Br, -I) underwent coupling with a variety of alkenes at 60 °C in water under aerobic conditions. The very stable nanocomposite catalyst was easily recovered, showed negligible Pd leaching, and retained good activity for at least ten successive runs without any additional activation.     

介孔炭的孔结构对其负载的Ru基氨合成催化剂性能的影响

采用模板法合成了介孔炭(MC),研究了其孔结构对其负载的Ru基氨合成催化剂Ba-Ru-K/MC性能的影响,采用N₂吸附脱附、扫描电镜和透射电镜等手段对介孔炭的孔结构进行了表征.研究发现,介孔炭载体的孔结构取决于模板剂的用量,当SiO₂/C质量比为1.0时,所制介孔炭比表面积最大.介孔炭负载的Ba-Ru-K催化剂活性与其介孔比表面积相关.在425℃,10MPa和10000h^-1条件下,合成氨的反应速率为139mmol/(g_cat·h).     

Highly enantioselective aldol reaction of acetaldehyde and isatins only with 4-hydroxydiarylprolinol as catalyst: concise stereoselective synthesis of (R)-convolutamydines B and E, (−)-donaxaridine and (R)-chimonamidine

A highly enantioselective aldol reaction of acetaldehyde and a wide scope of isatins has been presented only using readily available 4-hydroxydiarylprolinol as catalyst, affording various desired 3-substituted 3-hydroxyindolin-2-one adducts with moderate to high yield (up to 95%) and good enantioselectivities (up to 98% ee). This method not only represents an example of concise stereoselective synthesis of enantiopure (R)-convolutamydines B and E, but also firstly exhibits expedient asymmetric synthesis optically active (−)-donaxaridine and (R)-chimonamidine.     

Effects of support pore size on new Cs_(2.5)H_(0.5)PW_(12)O_(40)/SiO_2 catalysts for the ring-opening polymerization of tetrahydrofuran

Mesoporous silica supported Cs_(2.5)H_(0.5)PW_(12)O_(40) catalysts were prepared by impregnation method,and several silica supports with different pore size were utilized.N_2 adsorption,XRD and ICP-AES techniques were utilized to characterize the silica supports and catalysts.XRD results showed that the dispersion of Cs_(2.5)H_(0.5)PW_(12) was better for the silica support with larger pore size.The catalytic activity results showed that the pore size played important role on the catalyst activity and the...     

镍负载量对Ni/MgO(111)催化甲烷二氧化碳重整反应性能影响

研究了MgO(111)负载镍基催化剂催化甲烷二氧化碳重整反应性能,针对镍负载量对反应活性和稳定性的影响进行了探讨。结果表明,随着镍负载量从2%增加到10%,催化剂的活性和稳定性均有所提高,但是当镍负载量进一步增加到20%时,催化剂的活性和稳定性略有下降。利用透射电子显微镜、X射线衍射和H₂吸附脱附等手段对催化剂结构进行了表征,利用热重分析、拉曼光谱和透射电镜等手段对反应后回收的催化剂进行了表征。研究发现,随着镍负载量的增大,活性金属镍的颗粒粒径呈现增长趋势,并且在反应过程中显示出不同的失活方式。2%Ni/MgO(111)催化剂的失活原因主要以Ni粒子的氧化为主,而负载量大于2%的Ni/MgO(111)催化剂的失活原因则是以积炭为主。     

Improved kinetics of ethanol oxidation on Pd catalysts supported on tungsten carbides/carbon nanotubes

Pd nanoparticles on tungsten carbides modified multiwalled carbon nanotubes (Pd-WC/MWCNT) catalysts have been prepared by an intermittent microwave heating (IMH) technique for the first time. The Pd-WC/MWCNT catalysts are evaluated and show an improved kinetics for the ethanol oxidation. It is recognized that the significant increase in the catalytic activity for ethanol oxidation on Pd-WC/MWCNT is attributed to both the synergistic effect between Pd nanoparticles and the WC support and the structure effect of the MWCNT. This type catalyst can be universally used as the oxygen reduction catalyst in fuel cells and sensors both in alkaline and acidic solutions.     

Periodic mesoporous silica-immobilized palladium(II) complex as an effective and reusable catalyst for water-medium carbon-carbon coupling reactions

Ethyl-bridged periodic mesoporous organosilicas (PMOs) functionalized with diphenylphosphino (PPh₂) ligands were synthesized by one-step evaporation-induced self-assembly (EISA), which were used as a support to immobilize Pd(II) organometallic catalyst by coordination reaction. The as-prepared Pd(II)-PPh₂-PMO(Et) exhibited high activity in water-medium C-C coupling reactions and could be used repetitively. The high activity could be attributed to the high dispersion of Pd(II) active sites and ordered mesopore channels which effectively diminished the steric hindrance and thus, diffusion limit. Meanwhile, the ethyl-fragments and the PPh₂-ligands in the support wall could synergic enhance surface hydrophobicity, which promoted the adsorption for organic reactant molecules.     

Effect of calcination conditions on the properties of a catalyst for ethylbenzene dehydrogenation

Summary The effects of calcination conditions on the properties of the catalyst for dehydrogenation of ethylbenzene were studied by using TG, DTA, and XRD. The formation temperature of polyferrite was higher than 600°C. The strength of the catalyst changed during calcination. Higher temperature enhanced the strength and improved the activity of catalyst. The calcination model has great influences on the catalyst performance. Multi-stage calcination improved the catalyst activity.     

A facile template approach for the synthesis of mesoporous Fe3C/Fe-Ndoped carbon catalysts for efficient and durable oxygen reduction reaction

Layer-structured FeOCl was used as a novel inorganic template and the Fe doping source for the facile synthesis of three-dimensional polypyrrole structures which can be converted into mesoporous Fe₃C/Fe-N-doped carbon catalysts for efficient and robust oxygen reduction reaction.     

Effect of thermal treatment on phase composition and ethanol oxidation activity of a carbon supported Pt50Sn50 alloy catalyst

A carbon supported Pt–Sn electrocatalyst in the Pt/Sn atomic ratio 50:50 was prepared by the reduction of Pt and Sn precursors with formic acid and thermally treated at 200 °C (i.e., in the presence of solid tin) and 500 °C (in the presence of molten tin) in flowing hydrogen. In the absence of thermal treatment, X-ray diffraction (XRD) analysis showed a solid solution of Sn in the face centered cubic (fcc) Pt and SnO₂. After thermal treatment, the formation of a main phase of hexagonal PtSn (niggliite) and a secondary phase of cubic Pt₃Sn was observed in the Pt50Sn50 catalyst. The relative amount of the PtSn phase increased with increasing thermal treatment temperature. The presence of molten tin gave rise to the formation of some big particles during annealing at 500 °C. The activity for the ethanol oxidation reaction (EOR) of the as-prepared catalyst was higher than that of both thermally treated catalysts and Pt75Sn25/C and Pt50Ru50/C by E-TEK. The higher activity for the EOR of the as-prepared Pt–Sn catalysts was ascribed to the presence of a large amount of SnO₂. Dedicated to Teresa Iwasita’s 65th birthday.     

Effect of catalyst confinement and pore size on Fischer-Tropsch synthesis over cobalt supported on carbon nanotubes

This paper studies the impact of structure of cobalt catalysts supported on carbon nanotubes(CNT) on the activity and product selectivity of Fischer-Tropsch synthesis(FTS) reaction.Three types of CNT with average pore sizes of 5,11,and 17 nm were used as the supports.The catalysts were prepared by selectively impregnating cobalt nanoparticles either inside or outside CNT.The TPR results indicated that the catalyst with Co particles inside CNT was easier to be reduced than those outside CNT,and the reducibility of cobalt oxide particles inside the CNT decreased with the cobalt oxide particle size increasing.The activity of the catalyst with Co inside CNT was higher than that of catalysts with Co particles outside CNT.Smaller CNT pore size also appears to enhance the catalyst reduction and FTS activity due to the little interaction between cobalt oxide with carbon and the enhanced electron shift on the non-planar carbon tube surface.     

新型碳纤维负载直接乙醇燃料电池Pt-SnO_2阳极催化剂的性能研究

采用静电纺丝技术制备了碳纤维基纳米Pt-SnO2阳极催化剂(Pt/Sn原子比为3)。通过X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)等技术对该催化剂进行了表征,并采用循环伏安法对其在乙醇燃料电池中的阳极催化活性进行了评价。结果表明,纳米Pt-SnO2催化剂均匀地分散在碳纤维骨架上;随着烧结温度的升高,碳纤维载体的致密度越高、导电性能越好。电催化性能测试表明,烧结温度为800℃时催化剂的峰电流密度最大,达到0.11 A/cm2,抗中毒能力也最强。单电池的发电性能表明,在一定的乙醇浓度下,1.0 mL/min进样流速具有最优的发电效率。     

In-Cu/SiO2催化剂用于醋酸甲酯加氢反应制乙醇

工业上常用玉米生产乙醇,从而造成粮食和燃料的选择两难局面.随着页岩气研究的不断深入以及全球可观的煤炭存量,用醋酸甲酯加氢制乙醇已引起广泛关注.铜基催化剂对酯加氢生成醇有高的转化率和选择性,其中铜铬催化剂性能较高,但铬对人体和环境的潜在危害限制了其广泛应用.Cu/SiO2催化剂价格低廉,环境友好,但其稳定性较差,容易失活不利于工业上应用.因此人们对Cu/SiO2催化剂进行改性.本文采用氨蒸法制备了一系列掺杂不同量氧化铟(In2O3)的Cu催化剂(In-Cu/SiO2).采用X射线衍射(XRD)、氮气吸脱附、氢气程序升温脱附(H2-TPD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)以及电感耦合等离子体发射光谱(ICP-OES)等手段对催化剂进行了表征,同时评价了催化剂的活性和稳定性.结果发现,In2O3的改性提高了Cu/SiO2催化剂在醋酸甲酯加氢制乙醇反应中的活性和稳定性; 其中当添加1%In2O3时,醋酸甲酯转化率从83.7%提高至97.8% (反应温度523 K,反应压力3 MPa,氢酯摩尔比15,液时空速2 h?1),且对液时空速的变化耐受性比较强.当液时空速大于3 h?1时,随着液时空速的增加,Cu/SiO2催化剂的活性和选择性急剧下降,而1In-Cu/SiO2催化剂变化相对较小.TEM和XRD结果表明,适量In2O3的掺入改善了Cu/SiO2催化剂活性组分的分散性,铜粒径变小;FT-IR和N2O化学吸附结果显示,In2O3的加入使得页硅酸铜含量增加,从而有效地抑制了催化剂还原过程中铜的聚合,因此催化剂性能提高.XPS结果表明,表面Cu0和Cu+活性位点之间的协同作用有助于改善催化剂性能.Cu/SiO2和1In-Cu/SiO2催化剂100 h的稳定性测试发现,Cu/SiO2催化剂的失活主要是由于活性组分颗粒尺寸聚集变大和表面Cu0和Cu+分布的破坏所致; 而1In-Cu/SiO2催化剂物化性质几乎保持不变,表明适量的In2O3可稳定Cu/SiO2催化剂,延长其使用寿命.由此推断,In2O3可能作为一种隔离剂以抑制铜纳米粒子的热迁移和聚集,从而有效地提高Cu/SiO2催化剂活性和稳定性.     

Cobalt nanoparticles supported on ionic liquid‐functionalized multiwall carbon nanotubes as an efficient and recyclable catalyst for Heck reaction

A novel and environmentally friendly cobalt nanoparticle catalyst supported on ionic liquid‐functionalized multiwall carbon nanotubes was successfully prepared and evaluated as a heterogeneous catalyst for the Mizoroki–Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of EtOH/MgCl(2) molar ratios on the catalytic properties of MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalyst for ethylene polymerization

MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl(2) on SiO(2) in heptane and further treatment with TiCl(4). MgCl(2)·nEtOH adduct solutions were prepared with various EtOH/MgCl(2) molar ratios for preparation of the MgCl(2)-supported and MgCl(2)-SiO(2)-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl(2)] for the MgCl(2)-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl(2)-SiO(2)-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl(2)] ratio. The lower [EtOH]/[MgCl(2)] in MgCl(2)-supported catalyst exhibited better catalytic activity. However, for the MgCl(2)-SiO(2)-supported catalyst, MgCl(2) can agglomerate on the SiO(2) surface at low [EtOH]/[MgCl(2)] thus not being not suitable for TiCl(4) loading. It was found that the optimized [EtOH]/[MgCl(2)] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl(2) was 7. Morphological studies indicated that MgCl(2)-SiO(2)-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO(2). The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region.     

Effect of crystallite size on the catalysis of alumina-supported cobalt catalyst for steam reforming of ethanol

The selectivity for steam reforming of ethanol on alumina-supported cobalt catalysts is closely related to the crystallite size of cobalt, which varies the strength of ethanol adsorption.     

碳纤维基PtSn催化剂直接乙醇燃料电池制备及性能研究

采用自制的碳纤维基PtSn催化剂薄膜作为阳极催化剂,商用Pt/C作为阴极催化剂,Nafion 115膜作为质子交换膜,通过热压制成膜电极,组装平板型直接乙醇燃料单电池,搭建测试系统并进行性能的测试,研究了温度、乙醇浓度、溶液流量、进气流量等参数对DEFC的影响。结果表明,当乙醇溶液浓度为1.0 mol/L、溶液进样流量为1.0 mL/min、溶液温度为80 ℃、氧气进样流量为100 mL/min时结果较优,单电池的最高功率密度达18.2 mW/cm²。     

Effect of an activating agent on the physicochemical properties and supercapacitor performance of naturally nitrogen-enriched carbon derived from Albizia procera leaves

The present study reports the preparation of naturally nitrogen-doped carbon nanostructured materials from Albizia procera leaves with enhanced electrochemical supercapacitance properties. The doped carbon materials were prepared by the pyrolysis of Albizia procera leaves at 850 °C. The effect of using various activating agents such as NaHCO₃ and ZnCl₂ was checked and compared on the structural and textural properties, specific capacitance, surface functional groups, and surface area. The Brunauer–Emmett–Teller (BET) analysis shows that NaHCO₃-activated nitrogen-doped carbon (NaNC) has a higher specific surface area compare to ZnCl₂-activated nitrogen-doped carbon (ZnNC) and nitrogen-doped carbon prepared without an activating agent (WANC). Overall, the BET and microscopic analyses confirmed that NaNC is composed of carbon nanosheets with macropores and mesopores, as well as a large number of micropores, which is completely different from the composition of ZnNC and WANC. In addition, the XPS analysis confirmed the existence of higher amount of nitrogen in NaNC compared to that of ZnNC, and WANC. NaNC exhibits a specific capacitance of 231 F g⁻¹ at 1 A g⁻¹ current with good energy and power densities, and an outstanding charging-discharging stability thanks to its unique features such as the existence of high amounts of nitrogen, high SSA, and the nanosheet-type morphology.     

One step NaBH4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

The ternary catalyst Pt₇₅Ru₅Ni₂₀ was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt₇₅Ru₅Ni₂₀/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.