Ni-B Amorphous Catalysts Research Articles

Synthesis of Nano-Porous Ti/TiO2/Ni-W-B Electrode for Electrocatalytic Reduction of Coal

1 Introduction Electrochemical hydrogenation of coal is a novel method for coal liquefaction, which applies electrical energy instead of high temperature and pressure to liquefy coal in direct coal liquefaction. However, the electrochemical coal reduction is limited by the sluggish cathode reaction kinetics.Nano-porous TiO2 has been received increasing attention due to its unique properties, such as large surface-to-volume ratio, uniform pore diameter and quantum size effect. Therefore, nano-porous TiO2 exhibited special performance in optics, chemistry and other fields with huge advantage compared with normal nano-TiO2 [1].Amorphous alloy catalyst with a unique short-range ordering but long-range disordering structure, and a high concentration of coordinately unsaturated sites, has been widely applied in hydrogenations [2]. In comparison with other binary Ni-based catalysts, the Ni-B amorphous catalysts exhibited high activity and selectivity, showing the promoting effect from alloying B on the hydrogenating reactions. Addition of a second metal such as W to Ni-B amorphous alloy catalyst could greatly enhance the activity in hydrogenation [3].In this report, we mainly focused the catalytic effects of nano-porous Ti/TiO2/ Ni-W-B electrode as a cathode for coal electroreduction. 2 Experimental 2.1 Preparation of nano-porous Ti/TiO2/Ni-W-B electrode Anodization coupled with electrodeposition was employed to prepare the nano-porous Ti/TiO2/Ni-W-B electrode, which used as the cathode for coal electroreduction. 2.2 Characterization of prepared electrodes The prepared electrodes were characterized by scanning electron microscopy (Hitachi SEM 6700F), X-ray diffraction analysis (XRD-2700, Dandong). Electrochemical measurements were carried out with a CHI660B electrochemistry workstation (CHI, China). 2.3 Electrolysis and Extraction of product The electrolysis cell was divided into two parts including anode and cathode by a microporous membrane. The cathode electrolyte volume was 40 mL, which consisted of 0.5 mol/L TBAB, 2.5 mol/L H2O, 20 g/L coal and DMF-EtOH (vol) = 2:3. The composition and volume of anode electrolyte were the same as the cathode solution but without coal. Extraction yield was calculated from the quality of THF soluble components dividing the quality of coal particles (0.8 g). 3 Results and discussion Figure 1 shows the SEM micrograph of the nano-porous TiO2film, which is prepared by anodization experiment, is a multiple porous network structure. The average size of the pore diameter is about 200 nm. After electrodeposition of Ni-W-B alloy catalyst, the surface of nano-porous TiO2 film was mostly covered by smaller size Ni-W-B particles which were shown in Fig. 1B.Figure 2 shows the LSV behavior of the electrodes in above organic system with coal at a sweep rate of 50 mV/s. The electrodeposition of catalyst increased the performance of electrodes significantly, demonstrating the positive effect of Ni-W-B amorphous alloy catalyst for coal reduction. It is also noticed that the improved performance of the nano-porous electrodes is obvious, illustrating the favorable nano-porous structure to the improvement of the coal electroreduction.Table 1 shows the liquid extraction yields of the coal electroreduction with different electrodes. The extraction yields increased with the different electrodes and obtained the maximum yield (34.5%) with the nano-porous Ti/TiO2/Ni-W-B electrode. 4 Conclusions The prepared nano-porous Ti/TiO2/Ni-W-B electrode with multiply nano-porous structure improved the coal electroreduction current obviously and increased the extraction yield of THF soluble components effectively, promising to be a great application prospect for electrocatalytic reduction of coal and other probable electroreductions. Acknowledgements We gratefully acknowledge the National Science Foundation of China (No. 20673071, 20873083 and 21173144), and the State Key Laboratory of Chemical Engineering (No. SKL-ChE-08A01).

Investigation on the Aqueous-phase Hydrogenation of Bio-oil for Saturated Alcohols Production over Ni-B Amorphous Catalysts

Ni-B amorphous catalysts were prepared by chemical reduction of nickel chloride with potassium borohydride aqueous solution and characterized by X-ray diffraction(XRD), Brunauer-Emmett-Tetter(BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) techniques. The catalytic performances of model compounds and bio-oil to produce saturated alcohols were evaluated in a semi-batch reactor. The results showed that the conversion of model compounds(acetone, furfural and phenol) and the selectivity of saturated alcohols reached 99.99% and 90.00% at 110 degrees C, 4.0 MPa(initial pressure). Under the conditions of 150 degrees C and 4.0 MPa, the yield of saturated alcohols reached 47.54%. High temperature of above 150 degrees C resulted in the transformation of amorphous phase to form crystal, which was attributed to the low catalytic activity. This work provides a new alternative for the production of saturated alcohols from bio-oil.

Preparation, Characterization and Catalytic Performance of Carbon Nanotubes Promoted Ni‐B Amorphous Alloy

AbstractNi‐B and Ni‐B/CNTs amorphous alloy catalysts were prepared by chemical reduction and impregnation‐chemical reduction methods, respectively, and characterized by TEM, ICP, XPS, XRD, BET and CO chemisorption techniques. Their catalytic activities were evaluated in acetylene selective hydrogenation reaction. Based on characterizations, the effects of carbon nanotubes on Ni‐B amorphous alloy were attributed to both its structure effect, dispersing Ni‐B particles, leading to bigger surface area of active nickel and enhancing the thermal stability, and the electronic effect, resulting in electron‐rich nickel centers. Therefore, the superior thermal stability and acetylene selective hydrogenation activities of Ni‐B/CNTs to Ni‐B amorphous catalyst were obtained in the present study.

Preparation and Catalytic Performance of Ni-B Amorphous Alloy Supported by Chitosan/SiO 2

Ni-B amorphous catalyst supported by chitosan (CS)-modified silica (Ni-B/CS/SiO 2) was prepared using impregnation-reduction method. The as-prepared catalysts were characterized using X-ray powder diffraction (XRD), fourier transform infrared (FTIR) spetra, inductively coupled plasma (ICP) spectrometer, Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The results showed that the particle sizes, the surface content of Ni active species, and catalytic activity were improved by introducing chitosan to the surface of silica. In the hydrogenation of furfuryl alcohol (FA) to tetrahydrofurfuryl alcohol (THFA), the amorphous Ni-B/CS/SiO 2 catalyst exhibited superior catalytic activity to the corresponding traditional Ni-B/SiO 2 amorphous catalyst and Raney Ni.

A study concerning the pretreatment of CNTs and its influence on the performance of NIB/CNTs amorphous catalyst

As prepared carbon nanotubes were pretreated with nitric acid (CNTs-HNO3) or ammonia (CNTs-NH3). Fourier transform infrared spectroscopy (FTIR) measurements showed that the surface of the nanotubes was functionalized with carboxylic and hydroxyl functional groups after the acid treatment and that basic groups containing nitrogen, such as N-H and C-N, were introduced to the surface of the nanotubes after the ammonia treatment. X-Ray diffraction analysis implied that the nickel residue in the CNTs was effectively removed by acid treatment. However, the nickel residue was only partially eliminated by ammonia pretreatment. NiB amorphous catalysts supported on CNTs-HNO3 and CNTs-NH3 were prepared by the impregnation-chemical reduction method and characterized by transmission electron microscopy (TEM), as well as inductively coupled plasma (ICP) spectroscopy and studied in the selective hydrogenation of acetylene. TEM measurements showed that a high density NiB particles of about 9 nm were homogeneously dispersed on the CNTs-NH3. However, NiB particles (13-23 nm)with amean size of 16 nm were scattered on the CNTs-HNO3.As a result, the activity and selectivity of NiB/CNTs-NH3 were higher than those of NiB/CNTs-HNO3 in the selective hydrogenation of acetylene.

Liquid phase hydrogenation of furfural to furfuryl alcohol over the Fe-promoted Ni-B amorphous alloy catalysts

Abstract The ultrafine Fe-doped Ni-B amorphous catalyst (Ni-Fe-B) was prepared by reducing mixed FeCl3 and NiCl2 with KBH4 in aqueous solution. At suitable Fe-content (χFe), the Ni-Fe-B amorphous catalyst exhibited much higher activity than the corresponding undoped Ni-B in the liquid phase hydrogenation of furfural (FFR) to furfuryl alcohol (FFA). With the increase of χFe, the activity first increased and then decreased while the selectivity to FFA changed in a contrast way. The Fe-B amorphous alloy itself was inactive for the FFR hydrogenation. The optimum χFe was determined as 0.51, at which the FFA yield reached 100% after reaction for 4 h. Based on various characterizations, the promoting effect of the Fe-dopant was discussed by considering (1) the increase in the surface area, more highly unsaturated Ni active sites, and the more homogeneous distribution of the Ni active sites owing to the presence of Fe2O3 as a dopant; (2) the affinity of the Fe3+ for the oxygen in the carbonyl group which strengthened the adsorption of the CO bond by the catalyst and thus facilitated its hydrogenation; (3) the electron donation of the metallic Fe to the metallic Ni, making Fe electron-deficient while Ni electron-enriched which activated the CO bond towards the hydrogenation.

Liquid phase glucose hydrogenation to d-glucitol over an ultrafine Ru-B amorphous alloy catalyst

Abstract A Ru-B amorphous alloy catalyst in the form of ultrafine particles was prepared by chemical reduction of RuCl 3 with borohydride in aqueous solution, whose amorphous structure was confirmed by XRD, DSC, and SAED. Heating pretreatment resulted in the rapid crystallization and the deep decomposition of the Ru-B amorphous alloy as well as the abrupt decrease in the surface area due to the gathering of small particles at high temperature. XPS spectra revealed that partial electrons transferred from the alloying B to the metallic Ru in the as-prepared Ru-B sample. In comparison with other catalysts, the as-prepared Ru-B amorphous catalyst exhibited excellent activity and perfect selectivity to d -glucitol as well as superior lifetime during the liquid phase glucose hydrogenation, showing its potential application in industrial process. The higher activity of the Ru-based catalysts than that of other metal catalysts, such as Co-B and Ni-B amorphous catalysts as well as Raney Ni catalysts, demonstrated that the metallic Ru was more active than both metallic Ni and Co for the glucose hydrogenation. Meanwhile, the Ru-B amorphous catalyst exhibited higher activity than its corresponding crystallized Ru-B and pure Ru powder catalysts, showing the promoting effects of both the amorphous structure and the electronic interaction between the metallic Ru and the alloying B, which was briefly discussed based on the kinetic studies and various characterizations.

Gas-phase hydrogenation of adiponitrile with high selectivity to primary amine over supported Ni-B amorphous catalysts

Gas-phase hydrogenation of adiponitrile (ADN) was performed at 1 atm pressure over the Ni-B/SiO 2 amorphous catalyst, which exhibited high selectivity to 1,6-hexanediamine (HDA) at 100% ADN conversion. The selectivity to HDA could be further enhanced by MgO dopant. The product analysis revealed that the selectivity to HDA was mainly dependent on the contents of 6-aminohexanenitrile and azacycloheptane formed during the ADN hydrogenation. The 6-aminohexanenitrile was an intermediate in the reaction; it resulted from the half-hydrogenation of ADN; and its content was strongly affected by the activity of the catalyst. The azacycloheptane was a side-product (secondary amine) formed via the nucleophilic addition of the primary amine on one side of ADN chain to the aldimino carbon atom on the other side which was adsorbed by the Ni active sites. The electronic density of the Ni active sites played a key role in determining the content of azacycloheptane. The presence of the alloying B resulted in the electron-enriched Ni active sites which effectively inhibited the formation of azacycloheptane and in turn, resulted in the high selectivity to HDA.

Study on the deactivation of amorphous NiB/SiO 2 catalyst during the selective hydrogenation of cyclopentadiene to cyclopentene

The deactivation of the silica supported NiB amorphous catalyst during the selective hydrogenation of cyclopentadiene (CPD) to cyclopentene (CPE) in a fixed-bed reactor was studied. According to the characterizations of the initial and used catalysts by ICP, BET, SEM, XRD and XPS, no significant sintering of the active component or crystallization of the amorphous structure was observed, while severe surface oxidation occurred after the deactivation of the catalyst. Those results demonstrated that such a deactivation should mainly be attributed to the oxidation of the active component. Water promoted the deactivation because the surface oxidation of elemental Ni was accelerated by forming Ni(OH) 2 in the presence of water. The deactivation resulted from sulfication and carboneous species deposition was not observed in the present conditions, although it really occurred at high sulfur concentration and low CPD conversion.