Phenol-formaldehyde resin route to the synthesis of several iron group transition metal phosphides

Abstract

A series of iron, cobalt and nickel metal phosphides of chemical formula Fe_xP, Co₂P and Ni₂P with high specific surface areas of 331.1, 294.2 and 228.0 m² g^?1, respectively, was firstly synthesized by phenol-formaldehyde resin route. It was found that the as-prepared Co₂P and Ni₂P samples synthesized using phenol-formaldehyde resin as a carbon source showed much higher BET surface areas than those prepared using other carbon sources reported before, including cinnamic strong alkali anion exchange resin, p-phenylenediamine and hexamethylenetetramine. This phenol-formaldehyde resin route was proved to be as universal as traditional H₂ reduction method.     

TiO2柱撑海泡石负载Ni2P的噻吩加氢脱硫性能

以氢氧化镍为镍源, 亚磷酸为磷源, TiO₂柱撑海泡石(Ti-Sep)为载体, 采用浸渍法制备了含磷化镍前驱体的样品, 然后采用程序升温还原法制备了Ni质量分数(w)为5%-25%的Ni₂P/Ti-Sep催化剂, 并考察了其噻吩加氢脱硫性能. 采用X射线衍射(XRD)、N₂吸附-脱附、热重分析(TGA)、透射电子显微镜(TEM)和傅里叶变换红外(FTIR)光谱对催化剂样品进行了表征. 结果表明, 海泡石经TiO₂柱撑之后层间距增大, 比表面积和孔容都明显变大, 热稳定性增强, 活性组分Ni₂P能很好地分散在海泡石层间及表面, 并且没有破坏海泡石的层状结构. 上述原因导致Ni₂P/Ti-Sep催化剂的噻吩加氢脱硫活性明显优于Ni₂P/Na-Sep(NaCl改性海泡石)和Ni₂P/HCl-Sep(HCl改性海泡石)催化剂. 当Ni负载量为15% (w)时, Ni₂P/Ti-Sep催化剂具有最好的噻吩加氢脱硫性能; 在反应温度为400℃时, 噻吩转化率达100%.     

Alumina-supported cobalt phosphide as a new catalyst for preferential CO oxidation at high temperatures

Abstract

Novel alumina-supported cobalt phosphide catalysts (designated as CoP-3, CoP-10, CoP-20 and CoP-40) prepared from the precursors with Co loadings of 3, 10, 20 and 40?wt% by H₂-temperature-programmed reaction were investigated as potential catalysts for preferential CO oxidation (PROX) in excess H₂ at high temperatures. It was found that the catalytic activities of these Co₂P/γ-Al₂O₃ catalysts were related to their Co loadings. The CoP-10 catalyst showed the best PROX performance in temperature range of 220–240?°C, which was attributed to its optimal microstructures (high surface area, small particle size and big amount of active site).     

Effect of the preparation conditions on the physicochemical and catalytic properties of Ni<Subscript>2</Subscript>P/SiO<Subscript>2</Subscript> catalysts

The effect of the reduction conditions on the physicochemical and catalytic properties of Ni₂P/SiO₂ catalysts was studied. The catalysts were prepared by impregnating silica with a solution of nickel acetate and diammonium hydrogen phosphate followed by drying, calcination, and temperature-programmed reduction. The Ni₂P/SiO₂ catalysts were reduced prior to hydrodeoxygenation (HDO) of methyl palmitate in the catalytic reactor (in situ) at temperatures of 550, 600, and 650 °С for 3 h and at 600 °С for 1 and 6 h. The reduction temperature and reduction time were shown to affect the conversion of methyl palmitate, and the optimal reduction conditions of the Ni₂P/SiO₂ catalysts were found. The Ni₂P/SiO₂ catalyst synthesized according to a widely used preparation method, including steps of passivation and rereduction at 450 °С in addition to the reduction step, is inferior in activity to the samples prepared in situ.     

Methane conversion with carbon dioxide on nickel aluminides

The catalytic activity of several samples based on nickel aluminides in methane conversion with carbon dioxide was studied. Nickel aluminides were prepared by the method of self-propagating high-temperature synthesis. The Ni₃Al system containing the nickel metal phase exhibited high activity at temperatures above 1073 K. The systems based on Ni₂Al₃ and NiAl only containing intermetallic compound phases were inactive.     

Preparation and Characterization of Room-temperature Ferromagnetic Ni-doped TiO2 Nanobelts

Ni-doped anatase TiO₂ nanobelts (NBs) with different Ni²⁺ contents were simply prepared by combining ion-exchange with hydrothermal treatment. They were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and magnetic measurement techniques. The results showed that Ni²⁺ cations doped into the TiO₂ lattice and no metallic nickel clusters or nanoparticles could be found. The magnetic results demonstrated that the prepared Ni-doped TiO₂ samples had complex magnetic mechanism including room-temperature ferromagnetic and paramagnetic behaviors, and with the increase of Ni²⁺ content, the magnetization also increased under the same applied field owing to uniform distribution of Ni²⁺ ions in TiO₂ nanobelts.     

Boosting Visible‐Light‐Driven Photocatalytic Hydrogen Evolution with an Integrated Nickel Phosphide–Carbon Nitride System

Solar light harvesting by photocatalytic H₂ evolution from water could solve the problem of greenhouse gas emission from fossil fuels with alternative clean energy. However, the development of more efficient and robust catalytic systems remains a great challenge for the technological use on a large scale. Here we report the synthesis of a sol–gel prepared mesoporous graphitic carbon nitride (sg‐CN) combined with nickel phosphide (Ni₂P) which acts as a superior co‐catalyst for efficient photocatalytic H₂ evolution by visible light. This integrated system shows a much higher catalytic activity than the physical mixture of Ni₂P and sg‐CN or metallic nickel on sg‐CN under similar conditions. Time‐resolved photoluminescence and electron paramagnetic resonance (EPR) spectroscopic studies revealed that the enhanced carrier transfer at the Ni₂P–sg‐CN heterojunction is the prime source for improved activity.     

Effects of the preparation methods on the properties of Ni-La2O3-SiO2 catalysts for m -dinitrobenzene hydrogenation

Ni-La₂O₃-SiO₂ catalysts were prepared by wetness impregnation and sol-gel method followed by conventional drying and supercritical drying, respectively. Their physico-chemical properties and activity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine were investigated by BET, XRD, TPR, H₂-TPD and activity tests. The results showed that the structural and catalytic properties of the Ni-La₂O₃-SiO₂ catalysts obviously depended on the preparation method and the drying mode. The catalyst prepared by the sol-gel method in combination with conventional drying exhibited the highest catalytic activity among the catalysts tested, attributable to its well-dispersed nickel particles and larger active nickel surface area.     

固相浸渍法制备NiO/CeO2催化剂及其在CO氧化反应中的应用

采用固相浸渍法制备了一系列NiO/CeO2催化剂,并通过与常规湿浸渍法比较,考察了制备方法对催化剂和CO氧化反应性能的影响.同时结合X射线衍射(XRD),N2吸附-脱附(BET),透射电镜(TEM),氢气-程序升温还原(H2-TPR),拉曼(Raman)光谱,X射线光电子能谱(XPS)等手段对催化剂的结构和表面物种分散状态进行了表征.CO氧化活性测试结果表明,当镍负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能.TEM、XPS、H2-TPR结果表明,固相浸渍法更有利于加强镍铈间的相互作用和得到高分散的镍物种,从而促进镍物种的还原.Raman结果表明固相浸渍法相比于湿浸渍法能产生更多氧空位,这有利于氧气在催化剂表面的活化,使得CO氧化反应更容易进行.     

非共价修饰碳纳米管/二氧化钛复合材料的合成及性能

采用溶胶-凝胶法在聚乙烯吡咯烷酮(PVP)非共价修饰的碳纳米管表面均匀沉积二氧化钛粒子制得纳米复合材料。用TEM、XRD、FTIR、N2吸脱附等对复合材料进行了表征。结果表明:纳米二氧化钛纳米粒子均匀沉积在被修饰碳纳米管表面,且二氧化钛为纯锐钛矿晶体结构,没有金红石和板钛矿相。非共价修饰碳纳米管/二氧化钛复合材料具有良好的介孔结构,其孔径分布主要集中在6～10 nm,且比表面积与纯的二氧化钛相比明显增大,在紫外光照射下降解亚甲基蓝,相比纯的二氧化钛和碳纳米管/二氧化钛,具有较高的催化活性。     

Catalytic Performance of Spherical MCM-41 Modified with Copper and Iron as Catalysts of NH3-SCR Process

Spherical MCM-41 with various copper and iron loadings was prepared by surfactant directed co-condensation method. The obtained samples were characterized with respect to their structure (X-ray diffraction, XRD), texture (N₂ sorption), morphology (scanning electron microscopy, SEM), chemical composition (inductively coupled plasma optical emission spectrometry, ICP-OES), surface acidity (temperature programmed desorption of ammonia, NH₃-TPD), form, and aggregation of iron and copper species (diffuse reflectance UV-Vis spectroscopy, UV-Vis DRS) as well as their reducibility (temperature programmed reduction with hydrogen, H₂-TPR). The spherical MCM-41 samples modified with transition metals were tested as catalysts of selective catalytic reduction of NO with ammonia (NH₃-SCR). Copper containing catalysts presented high catalytic activity at low-temperature NH₃-SCR with a very high selectivity to nitrogen, which is desired reaction products. Similar results were obtained for iron containing catalysts, however in this case the loadings and forms of iron incorporated into silica samples very strongly influenced catalytic performance of the studied samples. The efficiency of the NH₃-SCR process at higher temperatures was significantly limited by the side reaction of direct ammonia oxidation. The reactivity of ammonia molecules chemisorbed on the catalysts surface in NO reduction (NH₃-SCR) and their selective oxidation (NH₃-SCO) was verified by temperature-programmed surface reactions.     

New Route of Microwave-Assisted Synthesis of Carbon-Supported Nickel Phosphide (C/Ni2P) Nanocomposite

Abstract

A novel, fast, and easy method for synthesizing a carbon-supported Ni₂P nanocomposite (C/Ni₂P) is described. The process involves a reaction between a nickel salt, phosphoric acid, and a carbon source by utilizing microwave irradiation. The carbon source for the nanocomposite is from renewable supplies, namely, tannin and lignin. The method has successfully synthesized Ni₂P nanoparticles dispersed in a carbon matrix with a particle size ranging from 20 to 50 nm in diameter. During the microwave process, tannin and lignin provided a reducing environment in the microwave irradiation process. The synthesized products are characterized by several characterization methods. The method showed that phosphoric acid, which is a nontoxic compound, could be used as an alternative P source for synthesizing Ni₂P. The method is fast, easy, and an economical process to synthesize the carbon-coated Ni₂P nanocomposite.     

Furfural Hydrogenation on Nickel‐promoted Cu‐containing Catalysts Prepared from Hydrotalcite‐Like Precursors

The nickel‐promoted Cu‐containing catalysts (Cu_xNi_y‐MgAlO) for furfural (FFR) hydrogenation were prepared from the hydrotalcite‐like precursors, and characterized by X‐ray powder diffraction, inductively‐coupled plasma atomic emission spectroscopy, N₂ adsorption‐desorption, UV‐Vis diffuse reflectance spectra and temperature‐programmed reduction with H₂ in the present work. The obtained catalysts were observed to exhibit a better catalytic property than the corresponding Cu‐MgAlO or Ni‐MgAlO samples in FFR hydrogenation, and the CuNi‐MgAlO catalyst with the actual Cu and Ni loadings of 12.5 wt% and 4.5 wt%, respectively, could give the highest FFR conversion (93.2%) and furfuryl alcohol selectivity (89.2%). At the same time, Cu⁰ species from the reduction of Cu²⁺ ions in spinel phases were deduced to be more active for FFR hydrogenation.     

超微镍粉的微乳液法制备研究

采用水（溶液）／二甲苯／SDS／正戊醇反相微乳液体系,用水合肼还原硫酸镍制备了纳米级（15－100nm)镍微粒,采用XRD、TEM等法对产物进行了鉴定与表征,考察了微乳液体系诸构成因素对纳米级镍制备的影响规律。     

Nickel-based ethylene oligomerization catalysts supported by PNSiP ligands

A series of nickel (II) complexes bearing silicon bridged diphosphines ligands (PNSiP) have been synthesized and characterized. All nickel precatalysts, activated with ethylaluminum dichloride (EtAlCl₂), exhibited moderate to high activities for ethylene dimerization to butylene. The in situ nickel precatalysts formed by mixing N-cyclopentyl-N-((diphenylphosphanyl)dimethylsilyl)-1,1-diphenylphosphanamine (L2) with NiBr₂(DME) showed high catalytic activity (2.40 × 10⁸ g/(mol_Ni·h)) and high product selectivity (88.6%) towards butene using methylcyclohexane as solvent at 1.0 MPa ethylene pressure and 45°C temperature, no polyethylene(PE) was observed. Ligand backbone tuning of PNSiP-based catalytic systems help in precise understanding of steric bulk variation effects on catalytic performance.     

In Situ and Theoretical Studies for the Dissociation of Water on an Active Ni/CeO2 Catalyst: Importance of Strong Metal–Support Interactions for the Cleavage of O–H Bonds

Water dissociation is crucial in many catalytic reactions on oxide‐supported transition‐metal catalysts. Supported by experimental and density‐functional theory results, the effect of the support on O? H bond cleavage activity is elucidated for nickel/ceria systems. Ambient‐pressure O 1s photoemission spectra at low Ni loadings on CeO₂(111) reveal a substantially larger amount of OH groups as compared to the bare support. Computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO₂(111) compared with pyramidal Ni₄ particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni²⁺ species by accommodating electrons in localized f‐states. The fast dissociation of water on Ni/CeO₂ has a dramatic effect on the activity and stability of this system as a catalyst for the water‐gas shift and ethanol steam reforming reactions.     

Nano-Fe3O4–Supported,Hydrogensulfate Ionic Liquid–Catalyzed,One-Pot Synthesis of Polysubstituted Pyridines

Abstract

Anchoring 1-methyl-3-(triethoxysilylpropyl) imidazolium chloride onto silica-coated magnetic Fe₃O₄ particles afforded the corresponding supported ionic liquid. Exchanging the Cl^? anion by treating with H₂SO₄ gave Brønsted ionic liquid 1-methyl-3-(triethoxysilylpropyl) imidazolium hydrogensulfate. The synthesized catalyst was characterized by various techniques such as infrared, x-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and elemental analyses. The results indicated that the prepared catalyst had a nanostructure. The catalytic activity of the supported ionic liquid was examined in the synthesis of the polysubstituted pyridines by reaction of aromatic aldehydes with acetophenones and ammonium acetate in moderate to good yields under solvent-free conditions. The catalyst can be easily recovered by applying an external magnetic field and reused for at least seven runs without deterioration in catalytic activity.     

Flexible Molecular Precursors for Selective Decomposition to Nickel Sulfide or Nickel Phosphide for Water Splitting and Supercapacitance

Herein, the synthesis of three nickel(II) dithiophosphonate complexes of the type [Ni{S₂P(OR)(4-C₆H₄OMe)}₂] [R=H ( 1 ), C₃H₇ ( 2 )] and [Ni{S₂P(OR)(4-C₆H₄OEt}₂] [R=(C₆H₅)₂CH ( 3 )] is described; their structures were confirmed by single-crystal X-ray studies. These complexes were subjected to surfactant/solvent reactions at 300 °C for one hour as flexible molecular precursors to prepare either nickel sulfide or nickel phosphide particles. The decomposition of complex 2 in tri-octylphosphine oxide/1-octadecene (TOPO/ODE), TOPO/tri-n-octylphosphine (TOP), hexadecylamine (HDA)/TOP, and HDA/ODE yielded hexagonal NiS, Ni₂P, Ni₅P₄, and rhombohedral NiS, respectively. Similarly, the decomposition of complex 1 in TOPO/TOP and HDA/TOP yielded hexagonal Ni₂P and Ni₅P₄, respectively, and that of complex 3 in similar solvents led to hexagonal Ni₅P₄, with TOP as the likely phosphorus provider. Hexagonal NiS was prepared from the solvent-less decomposition of complexes 1 and 2 at 400 °C. NiS (rhom) had the best specific supercapacitance of 2304 F g⁻¹ at a scan rate of 2 mV s⁻¹ followed by 1672 F g⁻¹ of Ni₂P (hex). Similarly, NiS (rhom) and Ni₂P (hex) showed the highest power and energy densities of 7.4 kW kg⁻¹ and 54.16 W kg⁻¹ as well as 6.3 kW kg⁻¹ and 44.7 W kg⁻¹, respectively. Ni₅P₄ (hex) had the lowest recorded overpotential of 350 mV at a current density of 50 mA cm⁻² among the samples tested for the oxygen evolution reaction (OER). NiS (hex) and Ni₅P₄ (hex) had the lowest overpotentials of 231 and 235 mV to achieve a current density of 50 mA cm⁻², respectively, in hydrogen evolution reaction (HER) examinations.     

Facile Preparation of Ni2P with a Sulfur‐Containing Surface Layer by Low‐Temperature Reduction of Ni2P2S6

Preparation of Ni₂P by temperature‐programmed reduction (TPR) of a phosphate precursor is challenging because the P?O bond is strong. An alternative approach to synthesizing Ni₂P, by reduction of nickel hexathiodiphosphate (Ni₂P₂S₆), is presented. Conversion of Ni₂P₂S₆ into Ni₂P occurs at 200–220 °C, a temperature much lower than that required by the conventional TPR method (typically 500 °C). A sulfur‐containing layer with a thickness of about 4.7 nm, composed of tiny crystallites, was observed at the surface of the obtained Ni₂P catalyst (Ni₂P?S). This is a direct observation of the sulfur‐containing layer of Ni₂P, or the so‐called nickel phosphosulfide phase. Both the hydrodesulfurization activity and the selective hydrogenation performance of Ni₂P‐S were superior to that of the catalyst prepared by the TPR method, suggesting a positive role of sulfur on the surface of Ni₂P‐S. These features render Ni₂P‐S a legitimate alternative non‐precious metal catalyst for hydrogenation reactions.     

Ni_2P/TiO_2-Al_2O_3催化剂的制备及其加氢脱硫、脱氮性能

采用溶胶-凝胶法制备了TiO2-Al2O3复合载体,采用浸渍法制备了Ni2P/TiO2-Al2O3催化剂,并用X射线衍射(XRD)、N2吸附比表面积(BET)测定、热重-差热分析(TG-DTA)、X射线光电子能谱(XPS)等技术对催化剂的结构和性质进行了表征.催化剂加氢脱硫(HDS)和脱氮(HDN)活性评价在实验室固定床连续反应装置上,以噻吩和吡啶为模型反应物进行.考察了不同载体、Ni2P负载量、标称Ni/P摩尔比、催化剂焙烧温度对Ni2P/TiO2-Al2O3催化剂上同时进行的噻吩加氢脱硫和吡啶加氢脱氮性能的影响.结果表明,TiO2含量为80%(w)的TiO2-Al2O3复合氧化物为载体,Ni2P负载量为30.0%(w),标称Ni/P摩尔比为1/2,催化剂焙烧温度为500℃时,Ni2P/TiO2-Al2O3催化剂加氢脱硫脱氮活性最高.在360℃,3.0MPa,氢油比800(V/V),液时体积空速1.5h-1的条件下,噻吩HDS和吡啶HDN转化率分别为61.32%和64.43%.