Efficient and recyclable novel Ni‐based metal–organic framework nanostructure as catalyst for the cascade reaction of alcohol oxidation–Knoevenagel condensation

A novel Ni‐based metal–organic framework (Ni‐MOF) with a Schiff base ligand as an organic linker, Ni₃(bdda)₂(OAc)₂?6H₂O (H₂bdda = 4,4′‐[benzene‐1,4‐diylbis(methylylidenenitrilo)]dibenzoic acid), was synthesized and characterized using powder X‐ray powder diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, elemental analysis and Fourier transform infrared spectroscopy. The synthesized Ni‐MOF exhibited a high catalytic activity in benzyl alcohol oxidation using tert‐butyl hydroperoxide under solvent‐free conditions. Also, the efficiency of the catalyst was investigated in the cascade reaction of oxidation–Knoevanagel condensation under mild conditions. The Ni‐MOF catalyst could be recovered and reused four times without significant reduction in its catalytic activity.     

改性SCR催化剂对Hg0催化氧化性能的研究

采用一系列金属氧化物对商用SCR催化剂进行掺杂改性,筛选出最优Ce掺杂SCR催化剂,模拟实际烟气组分,考察了Ce改性催化剂对烟气中Hg⁰氧化的影响。实验结果表明,Ce掺杂比例适当可显著提高其催化活性,Ce最佳负载量为9%时,Hg⁰的催化氧化效率比未掺杂SCR催化剂提高近40%,BET和XRD也显示,CeO₂在催化剂表面分散程度较好,未出现聚集现象。烟气工况对Hg⁰的催化氧化具有重要影响,其中,烟气组分HCl显著促进了Ce改性催化剂对Hg⁰的氧化,在一定温度范围内,Hg⁰的氧化效率随着温度升高而增加,在最佳空速、温度和烟气组分浓度时,Hg⁰的催化氧化效率可达95.11%。此外,掺杂CeO₂之后SCR催化剂的脱硝性能并未受到影响。     

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K₅[CoW₁₂O₄₀]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X‐ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N₂ adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101 catalyst was more than 20 times higher than that of the homogeneous Co‐POM catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligible leaching of Co‐POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from reaction media.     

树枝状钯纳米结构的控制合成及硝基苯加氢反应的催化活性

以氯钯酸为前驱体, 苯甲醇为还原剂和溶剂, 十六烷基吡咯烷酮(PVP)为稳定剂, 在微波辐射下制备了分散均匀、形貌均一的树枝状钯纳米结构. 产物用透射电子显微镜(TEM), X射线粉末衍射(XRD), X射线光电子能谱(XPS)进行了表征, 表明所制备的Pd纳米颗粒呈树枝状, 形貌单一, 分散均匀, 是由许多近似圆形的小颗粒自组装而成的二级结构. 对树枝状钯催化硝基苯加氢反应进行探究, 表明树枝状钯的催化活性比市售的钯碳催化剂的催化活性高.     

Ni/TPC催化剂的制备、表征及在秸秆热解燃气重整中的应用

以废弃汽车外轮胎热解后的副产物轮胎热解焦（Tyre pyrolysis char，TPC）为原料，利用均匀沉淀法制备以轮胎焦为载体的负载型Ni/TPC催化剂，采用EDX、SEM、XRD、TG、BET手段对催化剂进行了表征与分析，同时使用管式炉测试了Ni/TPC催化剂在秸秆热解燃气重整中的催化性能，并考察了热解温度、保温时间、镍负载量及催化时间对秸秆热解燃气重整效果的影响。研究结果表明，TPC富含焦和金属，Ni/TPC催化剂分散均匀，热稳定性好，比表面积为62 m²/g。催化剂活性测试显示，Ni/TPC催化剂用于作物秸秆热解燃气重整具有很强的催化活性，可显著提高燃气中可燃气体含量；热解温度在750℃、保温时间10 min、30%的Ni负载量时Ni/TPC催化剂的催化效率最高，连续使用850 min后，燃气中的H₂含量仍相对提高到50%以上，长时间使用后活性结构由Ni₃ZnC_0.7转变成FeNi₃，催化活性依然较强且趋于稳定，TPC可以作为良好的新型镍基催化剂载体。     

Preparation of Al2O3-supported nano-Cu2O catalysts for the oxidative treatment of industrial wastewater

Cuprous oxide (Cu₂O) nanoparticles supported on Al₂O₃ prepared using two different methods (hereafter referred to as catalyst I and II, respectively) were characterized by XRD and TEM. The catalytic activities of catalyst I and II during the treatment of industrial wastewater were then investigated. Specifically, the progress of the catalytic oxidation of industrial wastewater was observed by monitoring the time-dependent change in the chemical oxygen demand (COD) of industrial wastewater when the catalysts were applied. The results indicated that the catalytic activity of catalyst II was greater than that of catalyst I. Furthermore, under optimal conditions the COD removal efficiency was 94.59%. Finally, the mechanism by which the oxidative degradation of the industrial wastewater occurred could be explained based on a hydroxyl radical mechanism.     

Sensing and photocatalytic properties of nanosized Cu(I)CN organotin supramolecular coordination polymer based on pyrazine

Orange prismatic crystals of the supramolecular coordination polymer (SCP) _∞³[Cu(CN)₂(Me₃Sn)(Pyz)], SCP 1 , were synthesized using a self‐assembly method under ambient conditions. Nanosized 1 was obtained using the same molar ratio in water by ultrasonic irradiation. SCP 1 was characterized using single‐crystal X‐ray diffraction, elemental analysis, thermal analysis and Fourier transform infrared spectroscopy. SCP 1 and its nanosized 1 particles were also examined using powder X‐ay diffraction and scanning electron microscopy. The luminescence emission of SCP 1 was studied as well as its use as a sensor for the detection of common organic solvents and metal ions. Also, the catalytic activities of nanosized 1 towards various organic dyes were investigated under ambient conditions, UV irradiation and ultrasonic irradiation. Nanosized 1 as a heterogeneous nanoparticle catalyst exhibits high catalytic activity for the degradation of eosin‐Y and acid blue dyes. The mechanism of degradation investigated using various scavenger techniques is proposed and discussed. The catalytic oxidation process is mainly caused by ?OH radicals.     

A novel mimetic peroxidase catalyst by using magnetite-containing silica nanoparticles as carriers

A method for coating magnetite and mimetic enzyme (hemin) with amorphous silica to form a novel mimetic peroxidase (magnetite–hemin/SiO₂) has been developed by combining reverse microemulsion and the modified Stöber method. The magnetic silica nanoparticle supported hemin has a long-term stability toward temperature and good reusability. They can be easily separated from the reaction solution by using an external magnetic field and reused directly for next round of reaction. The peroxidase activity of the magnetite–hemin/SiO₂ was studied based on its catalytic effect on the reaction of p-hydroxyphenylacetic acid and H₂O₂. The results indicated that the catalytic activity of the new mimetic enzyme catalyst is higher than that of the free hemin. The possibility of its application was proven by the determination of H₂O₂, with the detection limits of 7.3 nmol L^?1 H₂O₂.     

Evaluation of a new porous titanium-niobium mixed oxide for photocatalytic water decontamination

A porous oxide semiconductor material made of a titanium-niobium oxide is evaluated as a heterogeneous photocatalyst for the photolysis of organic compounds in water. The photodegradation of micromolar solutions of a test compound, bromocresol green dye, was used to evaluate the material’s catalytic activity under ultraviolet light irradiation. The photolysis experiments were performed at pH 2.1, 3.6, and 7.0 and the dye concentrations were monitored over time down to 0.15 ppm using the optical absorbance of the dye in its basic form at a wavelength of 616 nm. The photolytic destruction of the dye was found to follow first order rate kinetics. The study compares the rate constants, with respect to the dye, of the new catalyst to a commercial nonporous TiO₂ catalytic powder, Degussa P25, which has excellent catalytic properties and is considered to be a benchmark for degradation efficiency. Results indicate that at pH 2.1 the photocatalytic activity of the porous material was slightly superior to the commercial TiO₂ powder, but it did not perform as well at pH 3.6 and 7.0. Possible reasons for the differences in the observed pH dependence of the new material versus the TiO₂ are discussed. The porous material had much better sedimentation characteristics than the TiO₂ powder, a quality that can be exploited to help solve catalyst retrieval and filtration problems after water decontamination of micro pollutants.     

Novel Catalysts for Gasification of Biomass with High Conversion Efficiency

We have developed catalysts for the gasification of biomass with much higher energy efficiency than the conventional methods (noncatalyst, dolomite, and commercial steam reforming Ni catalyst). In our investigation, the Rh/CeO₂ gave high yields of syngas for cellulose gasification using a fluidized-bed reactor with batch feeding of cellulose. However, the catalyst was deactivated because of sintering of CeO₂ during the reaction. To prevent the CeO₂ sintering, we have further improved the catalyst and found that Rh/CeO₂/SiO₂ was quite stable for the gasification of cellulose. It was demonstrated that Rh/CeO₂/SiO₂ gave almost complete gasification of real biomass (wood powder) at 873 K. These results indicate that the combination of this kind of catalyst and fluidized-bed reactor can realize the energy-efficient biomass gasification.     

Heterogenized peroxopolyoxotungstate catalyst on the surface of clicked magnetite‐graphene oxide nanocomposite: Magnetically recoverable epoxidation catalyst

A new heterogeneous catalyst for the epoxidation of olefins was prepared by immobilization of peroxophosphotungstate anions on the surface of clicked magnetite‐graphene oxide as magnetically recoverable support. To prepare the heterogeneous catalyst, the clicked magnetite‐graphene oxide support was prepared by thiolene click reaction of thiol functionalized graphene oxide with vinyl modified magnetite nanoparticles. The tailored support was then modified with aminopropyl groups followed by electrostatic interaction with peroxophosphotungstate anions to achieve the desired heterogeneous catalyst. Characterization of the catalyst was performed by various physicochemical methods which confirmed the successful immobilization of peroxopolyoxotungstate species on the surface of clicked magnetite‐graphene oxide. Catalytic activity of the catalyst revealed its high catalytic activity and selectivity in the epoxidation of various olefins in the presence of H₂O₂ as green oxidant. This heterogeneous catalyst can be magnetically reused several times without significant loss of activity and selectivity.     

Zinc Powder Catalysed Formylation and Urealation of Amines Using CO2 as a C1 Building Block†

Transformation of CO₂ into valuable organic compounds catalysed by cheap and biocompatible metal catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of amines with CO₂ and (EtO)₃SiH under solvent free condition. Using 2 mol% zinc powder as the catalyst, a series of secondary amines, both the aromatic ones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines were used as the substrates, the reactions produce urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic activity. The analysis on the reactants/products mixture after filtering out the zinc powder showed the zinc concentration in the mixture is low to 1 ppm. The pathways for the formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.     

基于TiO2的绿色多相催化剂催化CO2与环氧化合物偶联反应

金属离子掺杂纳米TiO2(M-TiO2,M=Zn2+,Cu2+,Co2+,Mn2+,Ni2+)在CO2与环氧化合物的偶联反应中表现出较高的催化活性.反应以四正丁基碘化铵(TBAI)为共催化剂,在无溶剂条件下进行.考察了反应温度、反应时间和CO2压力在Zn-TiO2/TBAI体系中对反应性能的影响.作为无毒的多相催化剂,Zn-TiO2可循环使用5次,其催化活性没有明显降低.     

Elaboration of nano titania-magnetic reduced graphene oxide for degradation of tartrazine dye in aqueous solution

In this paper, magnetic nanocomposites are synthesized by loading reduced graphene oxide (RG) with two components of nanoparticles consisting of titanium dioxide (TiO₂) and magnetite (Fe₃O₄) with varying amounts. The structural and magnetic features of the prepared composite photocatalysts were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis/DRS), Raman and vibrating sample magnetometer (VSM). The resulting TiO₂/magnetite reduced graphene oxide (MRGT) composite demonstrated intrinsic visible light photocatalytic activity, on degradation of tartrazine (TZ) dye from a synthetic aqueous solution. Specifically, it exhibits higher photocatalytic activity than magnetite reduced graphene oxide (MRG) and TiO₂ nanoparticles. The photocatalytic degradation of TZ dye when using MRG and TiO₂ for 3 h under visible light was 35% and 10% respectively, whereas for MRGT it was more than 95%. The higher photocatalytic efficiency of MRGT is due to the existence of reduced graphene oxide and magnetite which enhances the photocatalytic efficiency of the composite in visible light towards the degradation of harmful soluble azo dye (tartrazine).     

A study on simultaneous catalytic ozonation of Hg<Superscript>0</Superscript> and NO using Mn–TiO<Subscript>2</Subscript> catalyst at low flue gas temperatures

Mn–TiO₂ catalysts were utilized as an ozonation catalyst for the first time to study the simultaneous catalytic ozonation of Hg⁰ and NO at low flue gas temperatures. BET, SEM–EDS, XRD, XPS, H₂-TPR, NO _x -TPD and Hg⁰-TPD were used to characterize the catalysts. The Mn–TiO₂ catalyst, in which the molar content of metal Mn was 60%, exhibited the best catalytic activities of Hg⁰ and NO oxidation, compared with other Mn–TiO₂ catalysts. It was found that within the range of experiment, the catalytic ozonation efficiency of Hg⁰ and NO was higher than that of ozonation or catalytic oxidation. The results also showed that the presence of NO gas inhibited the catalytic ozonation of elemental mercury, and the inhibition was enhanced with the NO inlet concentration, while few elemental mercury molecules did promote the catalytic ozonation of NO. The addition of H₂O vapor promoted the catalytic ozonation of Hg⁰ and NO. In addition, 0.6Mn–TiO₂ catalyst demonstrated a good TOS and cyclic stability. The catalytic ozonation of NO and Hg⁰ on Mn–TiO₂ catalyst likely followed the Langmuir–Hinshelwood mechanism, where the hydroxyl radicals reacted with adjacently adsorbed NO molecules and elemental mercury on catalyst surface.     

Investigation of catalytic properties of two new orthopalladated complexes supported on montmorillonite: Synthesis,characterization and application in aerobic oxidation of alcohols

Two new complexes, [Pd(L₁)(C,N)]NO₃ ( 1 ) and [Pd(L₂)(C,N)]NO₃ ( 2 ) (L₁ = 5‐nitro‐1,10‐phenanthroline, L₂ = 4‐methyl‐1,10‐phenanthroline, C,N = benzylamine), have been synthesized and characterized using infrared and NMR spectroscopies and elemental analysis. Montmorillonite (MMT‐K10 clay) was used as a solid support for incorporating the cationic part of complexes 1 and 2 to produce catalysts 1 and 2 , respectively, as heterogeneous catalysts. Catalyst 1 was identified using powder X‐ray diffraction and scanning and transmission electron microscopies, and the content of palladium obtained from inductively coupled plasma analysis. By changing the electron‐donating group on the L₁ ligand with an electron‐withdrawing one, a minor improvement was observed in the catalytic properties. Catalyst 1 showed better efficiency for oxidation of benzyl alcohol in comparison with catalyst 2 , so catalyst 1 was used for the aerobic oxidation of alcohols to corresponding aldehydes or ketones without over‐oxidation (with and without bubbling of air). This catalytic system showed high activity towards alcohols under mild conditions. Finally, the reusability of catalyst 1 was investigated with multiple reuses of the supported catalyst in subsequent alcohol oxidation reactions.     

过渡金属氧化物掺杂对铜锰氧化物催化CO氧化性能的影响

以乙酸铜和乙酸锰为铜锰前驱体,以NH₄HCO₃为沉淀剂,相应金属硝酸盐为掺杂剂,采用共沉淀法制备了不同过渡金属氧化物掺杂的铜锰氧化物催化剂.?采用N₂物理吸附、X射线衍射,氢气-程序升温还原和原位红外漫反射光谱等方法对催化剂进行了表征,考察了系列催化剂上CO反应性能.?结果表明,掺杂过渡金属氧化物可以调变催化剂对CO的吸附能力,进而影响催化剂性能.     

Ordered mesoporous Pt/Fe3O4–CeO2 heterostructure gel particles with enhanced catalytic performance for the reduction of 4-nitrophenol

The unique physicochemical properties of ordered mesoporous transition metal oxides have attracted more and more attention. The hydrolysis process of metal oxide precursors is difficult to control, and it is difficult to synthesize an ordered mesoporous transition metal oxide material using the conventional template method. Ordered mesoporous Pt/Fe₃O₄–CeO₂ heterostructure gel materials with excellent catalytic properties were successfully prepared using aerogel technology and the chemical deposition method. The Pt/Fe₃O₄–CeO₂ material was an n–n combined heterostructured semiconductor material which consisted of a magnetic Fe₃O₄ layer, a CeO₂ core and Pt noble metal doped nanoparticles. A layer of Fe₃O₄ thin film was formed on the surface of ordered mesoporous Pt/CeO₂ gel matrix material using the chemical deposition method. The intriguing heterostructural features could facilitate reactant diffusion and exposure of active sites which could enhance synergistic catalytic effects between the Pt nanoparticles and CeO₂ nanoparticles. Compared with Pt/CeO₂, the prepared Pt/Fe₃O₄–CeO₂ showed enhanced catalytic activity in the reduction of 4-nitrophenol at room temperature. The catalytic activity of the heterostructure catalysts was systematically investigated using 4-nitrophenol reduction as a model reaction. The results showed that the Pt (0.1%)/Fe₃O₄–CeO₂ sample exhibited the optimal catalytic performance toward catalytic reduction of 4-nitrophenol to 4-aminophenol. The study provided a method for the preparation of heterostructure nanocatalysts with high efficiency, which would be effective for application in various catalytic reactions.     

超声改性的CuO/Al2O3-MgO催化剂结构 及其超低浓度甲烷催化燃烧性能

采用普通浸渍和超声改性的方法分别制备了CuO/Al₂O₃-MgO催化剂,用于超低浓度甲烷的催化燃烧,并利用SEM、XRD、XPS、H₂-TPR等技术对催化剂进行表征,研究了超声改性作用对催化剂的结构和性能的影响.结果表明,与普通浸渍法制备的催化剂相比,在超声改性的CuO/Al₂O₃-MgO催化剂上,甲烷的转化率得到提高,燃烧特征温度降低.随着超声时间的延长和超声功率的增加,催化剂的催化活性均呈现先增大后减小的趋势;催化剂制备的最佳超声工况为功率150 W、时间20 min.超声改性可使催化剂的比表面积和孔容积增大,表面催化活性较高的Cu⁺浓度增加,活性组分CuO由晶相向非晶相转变、分散度增大,晶粒粒径变小、分布更均匀;这使得甲烷催化燃烧的表观活化能下降、催化剂活性得到增强.     

HIGHLY ACTIVE CATALYTIC STEREOSPECIFIC POLYMERIZATION OF STYRENE

A novel highly active catalyst of TiCl_4/MgCl_2--Al(C_2H_5), system (called SN-1 catalyst, in whichrare earth compound NdCl_3, is included) was used for studying stereospecific polymerization of styrenein benzene solution. Highly isotactic polystyrene was prepared with far better yield and higher cataly-tic efficiency than the results ever reported in literatures. The influences of concentration of mono-mer, catalyst, triethyaluminum as well as polymerization temperature on the catalytic efficiency, yield,tacticity and molecular weight of polystytene have been investigated.