Ni2P Particles Research Articles

A study of the hydrodenitrogenation of propylamine over supported nickel phosphide catalysts using amorphous and nanostructured silica supports

Pyrolysis of animal by-products provides pyro-oil that contains about 10wt% nitrogen mainly in aliphatic compounds and virtually no sulfur. The nitrogen should be removed from the oil preferably by hydrodenitrogenation (HDN) to obtain liquid fuel and ammonia. In order to understand the catalytic HDN processes of such bio-oils the HDN of propylamine (PA) was studied as model reaction over silica-supported Ni2P and Ni catalysts. Catalysts were prepared by H2-reduction of catalyst precursor NiO/phosphated silica gel and NiO/phosphated SBA-15 silica material and NiO/silica gel. The catalyst surface was characterized by Diffuse Reflectance Infrared Fourier Transform Spectroscopic (DRIFTS) examination of adsorbed CO. It was shown that the Ni2P particles had a highly defected structure in the initial reduced state of the catalyst but were rapidly converted to ordered crystals in contact with PA under reaction conditions. The HDN reaction of PA was studied using a flow-through tube reactor and also by in situ DRIFTS experiments in the 16–60bar pressure and 200–400°C temperature range. Below about 300°C the Ni2P catalysts were active in the direct hydrogenolysis of the CN bond of PA, however, the main reaction was the PA disproportionation to dipropylamine (DPA) and ammonia. Above about 300°C the hydrogenolysis of the DPA CN bond became the main reaction. Near to full HDN of PA could be attained without hydrogenolysis of CC bond. In contrast, Ni/silica gel catalyst was hardly active in the direct C–N hydrogenolysis of PA but was active in the PA disproportionation to DPA. Above about 300°C reaction temperature ammonia, less propane, and significant amount of methane and ethane were formed.

Highly active Ni2P/SiO2 catalysts phosphorized by triphenylphosphine in liquid phase for the hydrotreating reactions

A highly loaded and dispersed 60%Ni/SiO2 catalyst was phosphorized by triphenylphosphine (PPh3) in liquid phase for the preparation of highly loaded and dispersed Ni2P/SiO2 catalysts. It was found that without pre-reduction, the Ni/SiO2 was difficult to be phosphorized by PPh3, and large Ni2P particles were resulted at the high phosphidation temperatures (543–593K). When the Ni/SiO2 was pre-reduced, the highly dispersed nano nickel particles formed were easily phosphorized by PPh3 at the lower temperatures (443–543K). The resulted Ni2P/SiO2 catalyst phosphorized by PPh3 at 443K possessed small and homogeneous Ni2P particles (∼6nm) with the high Ni2P active site density (324μmol/g) as titrated by the adsorption of CO. It was significantly more active than the Ni2P/SiO2 catalyst phosphorized by PH3 in gas phase with the Ni2P active site density of 263μmol/g for the hydrodesulphurization of dibenzothiophene and hydrogenation of tetralin to decalin in a model diesel.

Novel Ni2P/zeolite catalysts for naphthalene hydrocracking to BTX

Ni2P catalysts supported on ZSM-5, Beta, and USY zeolites were prepared by temperature-programmed reduction (TPR), applied for the hydrocracking of naphthalene, and characterized by BET, CO uptake, NH3-TPD, TEM, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS). The catalytic activity was tested at 673K and 3.0MPa in a three-phase fixed bed reactor for hydrocracking of naphthalene. The Ni2P/Beta exhibited best activity with a naphthalene conversion of 99%, and a BTX yield of 94.4%. Well-dispersed Ni2P particles combined with moderate acidity and porosity of zeolite Beta contributed to the enhanced hydrocracking activity of naphthalene into BTX.

Preparation and Characterization of Carbon Nanotubes Supported Ni2P for Hydrodesulfurization (HDS) of Naphtha

Ni2P nanoparticles supported by functionalized carbon nanotubes (CNTs) were prepared for the first time. Nickel (II) dihydrogenphosphite as a source of nickel, with different loadings on the functionalized CNTs, were used. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. Surface areas of the samples were measured by using Brunauer, Emmett and Teller (BET) method. The catalytic activity of the prepared samples was studied in hydrodesulfurization (HDS) of naphtha. The results showed that the CNTs were functionalized and Ni2P particles were dispersed on the functionalized CNTs. It was also indicated that the pores size of Ni2P particles were less than 20 nm. The catalytic study of the prepared samples confirmed that these compounds were stable and active in the process. Removal of sulfur from the desired naphtha in presence of the samples depended on the nickel loadings and increased with temperature in all cases.

Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering

The size-dependent catalytic activity of Ni2P for hydrodesulfurization (HDS) remains unstudied because the traditional temperature programmed reduction (TPR) method used in catalyst preparation results in highly polydisperse Ni2P particles. The ability to control the Ni2P particle size in the range 5–20 nm by varying the quantity of oleylamine in solution-phase arrested precipitation reactions is reported. Particles were introduced to a high surface area silica support (Cab-O-Sil, M-7D grade, 200 m2/g) via incipient wetness, and HDS activity was probed against dibenzothiophene (DBT). All samples were less active than TPR prepared materials, and the smallest particles were the least active, contrary to expectation. This is attributed in part to particle sintering under HDS conditions. Sintering occurs independently of wt% loading of catalyst, time, incipient wetness procedure, and ionic additives, at all temperatures greater than 200 °C. Sintering is minimized by encapsulation of Ni2P nanoparticles in a me...

Facile synthesis of Ni-coated Ni2P for supercapacitor applications

Ni2P particles are coated homogenously with amorphous Ni by an electroless plating process. The Ni coating exhibits a nanoflake morphology and has 20–30 nm in thickness after plating for 10 min. As electrochemical capacitor materials, the pseudocapacitor behaviors are investigated by cyclic voltammograms and galvanostatic charge–discharge tests in 2 M LiOH. The Ni-coated Ni2P delivers high specific capacitances of 581 F g−1 at 1 A g−1 and 464 F g−1 at 40 A g−1, respectively, and also exhibits superior cycling performance. The specific capacitance can achieve a maximum of 1115 F g−1 at 2 A g−1, which can still maintain 1029 F g−1 (92.3% capacity retention) after 3000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its flake-like Ni coating which can provide fast ion and electron transfer and large amounts of active sites.

Ligand and Ensemble Effects in Bimetallic NiFe Phosphide Catalysts for the Hydrodeoxygenation of 2-Methyltetrahydrofuran

A series of supported nickel–iron phosphide catalysts were used to study the hydrodeoxygenation (HDO) of 2-methyltetrahydrofuran (2-MTHF), a model compound for biomass-derived pyrolysis oil. The catalysts were prepared by incipient wetness impregnation of the active components onto potassium ion-exchanged USY zeolites followed by temperature-programmed reduction. The samples were denoted as Ni2P/KUSY, NiFeP(3:1)/KUSY, NiFeP(1:1)/KUSY, NiFeP(1:3)/KUSY, and FeP/KUSY, where the numbers in parenthesis are the Ni:Fe molar ratios. The results of the studies can be understood from ensemble and ligand effects. X-ray diffraction analysis indicated the presence of alloys in the mixed composition samples, and this was supported by CO chemisorption and infrared measurements. Uptakes of CO decreased as the iron content increased, suggesting that iron present on the surface of the catalysts blocked chemisorption sites. Fourier transform infrared (FTIR) measurements showed a single peak for linearly adsorbed CO whose intensity decreased with Fe content, in agreement with the uptake results. Moreover, the FTIR peak shifted monotonically consistent with a ligand effect in an alloy formed in the Ni2P and FeP particles. The reactivity in 2-MTHF HDO was studied at 250–325 °C and 0.5 MPa and it was found that the conversion was highest for the Ni2P/KUSY sample and decreased steadily with Fe content. However, the turnover frequency did not change significantly, indicating that the rate-determing step was activation of 2-MTHF on single Ni sites. The selectivity at low conversion (3 %) changed from mostly n-pentane and n-butane for Ni2P/KUSY to mostly 1-pentanol for the iron-containing samples, suggesting that in subsequent steps an ensemble effect was operational with the iron influencing the reaction chemistry. At high conversion (70 %) all the samples produced mostly n-pentane and n-butane.

Synthesis of Nickel Phosphide Nanorods as Catalyst for the Hydrotreating of Methyl Oleate

Arrays of nickel phosphide nanorods were successfully synthesized by nanocasting using mesostructured silica SBA-15 as a hard template (HT-Ni2P). After temperature-programmed reduction of the phosphate precursor infiltrated within the pore walls of SBA-15, the unsupported material was obtained by removing the silica matrix with diluted HF. The pore channel of the SBA-15 template stabilizes the Ni2P particles, preventing sintering after the high reduction temperature and shaping their elongated morphology. Moreover, HT-Ni2P catalyst shows an improvement in the textural properties with a significantly higher surface area than the reference sample synthesized in the absence of template. X-ray diffraction revealed that the only crystalline phase present in this material was Ni2P. On the other hand, transmission electron microscopy shows that the catalyst is mainly constituted by agglomerates of nanorods. Through EDX microanalysis the efficient removal of silicon was confirmed. Under hydrotreating conditions, nanorods of Ni2P show a fourfold enhancement in the conversion of methyl oleate with respect to conventional Ni2P synthesized in absence of hard template. Nevertheless, when these data are normalized to surface area, the specific activity of HT-Ni2P nanorods is significantly lower than that of the conventionally prepared sample. Differences in selectivity were also observed as Ni2P nanorods favored the decarboxylation reaction leading to a higher yield of n-heptadecane.

Effect of Metal Promoters on the Structure and Performance of the Ni_2P/SBA-15 Catalyst for Hydrodesulfurization

Ni2P/SBA-15 catalysts with initial P/Ni molar ratio of 0.8 were prepared by co-impregnation method with mesoporous molecular sieve SBA-15 as support,Ni(NO3)2·6H2O as a source of nickel and(NH4)2HPO4 as a source of phosphorus.Then,a series of M-Ni2P/SBA-15 catalysts were prepared by the addition of Li,Na,K,Mg,Ca,Sr,Ba metal promoters and characterized by X-ray diffraction(XRD).The catalytic performance of the catalysts for hydrodesulfurization(HDS) was evaluated in a fixed-bed microreactor with the decalin solution of 1%(mass fraction) model compound dibenzothiophene.The results indicated that Ni2P particles were the active phase for M-Ni2P/SBA-15 catalysts.Different metal promoters(M) had different effects on the HDS performance of M-Ni2P/SBA-15 catalysts,among which the alkaline earth metal Ca was the best one to improve the HDS activity of the catalysts.Over the Ca-Ni2P/SBA-15 catalyst with Ca mass fraction of 3.5% the conversion of DBT HDS reached 98.6% under the conditions of reaction pressure at 3.0 MPa and temperature at 360℃.In addition,different metal promoters also affect HDS reaction mechanism in different ways.

An approach to preparing porous and hollow metal phosphides with higher hydrodesulfurization activity

This paper describes an effective method for the synthesis of metal phosphides. Bulk and supported Ni 2P, Cu 3P, and CoP were prepared by thermal treatment of metal and the amorphous red phosphorus mixtures. Porous and hollow Ni 2P particles were also synthesized successfully using this method. The structural properties of these products are investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP–AES) and X-ray photoemission spectroscopy (XPS). A rational mechanism was proposed for the selective formation of Ni 2P particles. In experimental conditions, the Ni 2P/SiO 2 catalyst exhibits excellent hydrodesulfurization (HDS) activity for dibenzothiophene (DBT).

XAFS studies on highly dispersed Ni2P/SiO2 catalysts for hydrodesulfurization of 4,6-dimethyldibenzothiophene

The Ni2P catalysts were prepared by a new synthetic method with the use of less oxidic phosphorus precursor in order to achieve high dispersion on silica support, and their structural properties and catalytic activity in HDS of 4,6-DMDBT were studied. Comparison was made with a conventionally prepared sample which was obtained by temperature programmed reduction method. Various characterizations were conducted by BET, CO uptake, TPR, XRD and X-ray absorption spectroscopy. The amounts of CO chemisorption uptake were 64 and 20μmolg−1 for Ni2P/SiO2-LT and Ni2P/SiO2-HT, respectively, indicating that the low temperature reduction technique led to better dispersion of Ni2P particles on SiO2 support. The catalytic activity in the HDS of 4,6-DMDBT followed the order, Ni2P/SiO2-HT(54%)<Ni2P/SiO2-LT(67%). The order correlated well with the amount of CO uptake. These results thus suggest that the HDS activity of the Ni2P catalysts highly depend on the dispersion of the Ni2P phase.

Nickel Phosphide Catalysts Supported on SBA-15 for Hydrodesulfurization of 4,6-Dimethyldibenzothiophene

Ni2P catalysts supported on SiO2 and SBA-15 were successfully prepared by temperature-programmed reduction (TPR), and the effect of Ni2P dispersion on the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS) activity was studied. The surface areas of the samples varied from low (Ni2P/SiO2, 127 m2 · g−1) to high (Ni2P/SBA-15, 283 m2 · g−1), with corresponding Ni2P average crystallite sizes decreasing from 20 to 5 nm. Extended X-ray absorption fine structure (EXAFS) studies were used to confirm the formation of Ni2P phase. Transmission electron microscopy (TEM) analysis showed that the SBA-15-supported Ni2P sample consisted of nanoparticles, which were probably located in the mesoporous channels or the external surfaces. The catalytic activity for HDS was measured at 613 K and 3.1 MPa in a three-phase fixed bed reactor using a model liquid feed containing 500 ppm S as 4,6-dimethyldibenzothiophene, 1000 ppm S as dibenzothiophene, 200 ppm N as quinoline, and 1% aromatics as tetralin in tridecane solvent. The Ni2P/SBA-15 catalyst had a steady-state HDS conversion of 99% at 613 K, much higher compared to the Ni2P/SiO2 catalyst with a HDS conversion of 54%. These results are probably due to the enhanced dispersion of the Ni2P particles on the high surface area SBA-15 support, as confirmed by CO chemisorptions, TEM and EXAFS analysis.

An approach to preparing highly dispersed Ni2P/SiO2 catalyst

Ni2P/SiO2 catalyst with high dispersion was obtained by temperature-programmedly reducing the precursor that was prepared via a new approach. In this approach, nickel-containing silica was firstly synthesized via a sol–gel process, and phosphorus species were then supported on it through impregnation. In the precursor, the nickel species highly dispersed and the interaction between nickel and support was strong. This contributed to the resistance of Ni2P to sintering, and the resulting Ni2P particles were very small and uniform. The Ni2P/SiO2 catalyst proved to be very active and stable in the hydrodechlorination of chlorobenzene.

Recent developments in synthetic approaches to transition metal phosphide nanoparticles for magnetic and catalytic applications

Recent advances in synthetic methods have led to the preparation of a wide array of transition metal phosphide nanoparticles, and characterization of these materials has provided insight into nanoscale magnetic and catalytic properties. This review highlights advances in the field that have been made since the time of the last review [S.L. Brock, S.C. Perera, K.L. Stamm, Chem. Eur. J. 10(2004)3364–3371]. Synthetic methods include solvothermal, solution-phase arrested precipitation, metal nanoparticle conversion, and phosphate reduction. Magnetic properties of FeP, Fe 2P and MnP nanoparticles and nanorods (among others), and recent data on thiophene hydrodesulfurization catalyzed by discrete, unsupported Ni 2P particles, is presented. Finally, the future prospects for the field are discussed.

In situ x-ray absorption fine structure studies on the structure of Ni2P supported on SiO2

The local structure around Ni in a nickel phosphide catalyst supported on SiO2 was investigated by an in situ x-ray absorption fine structure (XAFS) method during the reduction process of the catalyst and the hydrodesulfurization (HDS) reaction of thiophene. In the passivated sample, the Ni phosphide was partially oxidized but during the reduction process Ni2P particles were regenerated. The particles had Ni-P and Ni-Ni distances of 0.220 and 0.259 nm, respectively, corresponding closely to those of bulk Ni2P. In situ XAFS clearly revealed that Ni2P structure was stable under the reaction conditions at atmospheric pressure and was an active structure for the HDS process.

In Situ X-ray Absorption Fine Structure Studies on the Structure of Nickel Phosphide Catalyst Supported on K-USY

Abstract Local structure around Ni in a nickel phosphide catalyst supported on K-USY was investigated by an in situ X-ray absorption fine structure (XAFS) method during the reduction process of the catalyst and the hydrodesulfurization (HDS) reaction of thiophene. In the passivated sample, Ni phosphide was partially oxidized but after the reduction, 1.1 nm diameter Ni2P particles were formed with Ni–P and Ni–Ni distances at 0.218 and 0.261 nm, respectively, corresponding to those of bulk Ni2P. In situ XAFS clearly revealed that the Ni2P structure was stable under reaction conditions and was an active structure for the HDS process.