Nano-sized Catalysts Research Articles

Highly active, stable, and recyclable magnetic nano-size solid acid catalysts: efficient esterification of free fatty acid in grease to produce biodiesel

Magnetic nano-size solid acid catalysts were prepared, characterized, and examined, for the first time, for the esterification of free fatty acid (FFA) to develop a green and efficient pretreatment step for producing biodiesel (fatty acid methyl ester, FAME) from waste grease containing FFA. PGMA-cat 4, consisting of a core of iron oxide magnetic nanoparticles (MNPs), a poly(glycidyl methacrylate) (PGMA) shell, and sulfonic acid groups on the surface, was synthesized in 98% yield from the corresponding core–shell structured PGMA–MNPs containing epoxy surface groups by gentle sulfonation with Na2SO3, possessing a mean size of 90 nm, high acid capacity of 2.3 mmol H+ g−1, and excellent superparamagnetic properties. Esterification of FFA (16 wt%) in grease with methanol using this catalyst (4 wt%) gave 96% conversion of FFA to FAME within 2 h. PGMA-cat 4 was easily separated under a magnetic field and showed no loss of productivity during 10 cycles. In comparison, PS-cat 12, consisting of a core of iron oxide MNPs, a polystyrene shell, and benzenesulfonic acids on the surface, was active but possessed no recyclability; Si-cat 14, consisting of a core of iron oxide MNPs, a silica shell, and sulfonic acids as surface groups, showed lower activity and poor recycling performance. The catalytic performance of PGMA-cat 4 was also better than those of the micro-size counterpart such as PGMA-cat (m) 15 and large-size solid acid catalysts such as Amberlyst 15. Thus, a novel, active, stable, and recyclable magnetic nano-size solid acid catalyst was successfully developed for the green and efficient esterification of FFA in grease as a pretreatment step to produce biodiesel from waste grease.

고압반응 하에서 요소와 메탄올을 사용한 메틸카바메이트와 디메틸카보네이트 제조에 관한 금속산화물 촉매 및 이온성액체의 영향

고압 반응시스템에서 요소와 메탄올로부터 메틸카바메이트(MC) 및 디메틸카보네이트(DMC)의 제조에 관한 금속산화물촉매와 이온성액체의 영향을 고찰하였다. 고립계에서 요소와 메탄올로부터 MC 수율은 촉매를 사용하지 않고도 <TEX>$150^{\circ}C$</TEX> 이상의 반응온도에서 거의 100%를 나타내었으나, DMC 수율은 반응온도와 무관하게 1.5% 이하로 매우 낮은값을 나타내었다. 또한 MC와 메탄올로부터 DMC 수율은 <TEX>$ZnCl_{2}$</TEX> 촉매를 사용한 경우에 가장 우수하였으며, 최적조건에서 16.3% 정도를 나타내었다. DMC 수율은 반연속식 실험에서 나노 크기의 촉매와 이온성액체를 함께 적용한 경우에 좀 더 향상되었다. Effect of metal oxide catalysts and ionic liquids on the synthesis of methyl carbamate(MC) and dimethyl carbonate (DMC) from urea and methanol was investigated in a high pressure reaction system. In closed system, MC yield from urea and methanol reached almost 100% at reaction temperature over <TEX>$150^{\circ}C$</TEX> without catalyst, whereas DMC yield of 1.5% under was obtained irrespective of catalysts used. In DMC synthesis from MC and methanol, <TEX>$ZnCl_{2}$</TEX> showed the highest catalytic activity and led to the DMC yield of 16.3% under optimal conditions. Furthermore, DMC yield can be enhanced by the simultaneous application of ionic liquids with nano-sized catalysts in semi-continuous reaction system.

Structural, Textural and Acid–Base Properties of Nano-Sized NiFe2O4 Spinel Catalysts

The effect of preparation methods on the textural, structural and acid–base properties of nano-sized nickel ferrite oxides was investigated. Several physicochemical methods are used for their characterization. Isopropanol, as a probe molecule, is used to determine acid–base properties. A correlation between textural, structural and acid–base properties of nanomaterials is established.

Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), O 2 temperature-programmed desorption (O 2-TPD), and inductively coupled with plasma atomic emission spectroscopy (ICP-AES) techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO (Mg/SiO 2 weight ratio) shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.

Non-destructive and controllable catalyst deposition of in situ growing carbon nanotubes onto the carbon fibre fabric

To in situ grow carbon nanotubes (CNTs) on the surface of carbon fibre fabric (CFF) with suitable diameter and uniform distribution, controllable catalyst deposition is the key process. A controllable and non-destructive pre-treatment, that is, electrochemical oxidation pre-treatment, was explored to facilitate uniform ‘seeding’ nano-sized catalyst particles on the surface of CFF without causing damage to carbon fibres. Main factors, such as voltage, concentration of electrolyte, electrolytic time, catalyst type and concentration of the catalyst precursor, were investigated. X-ray photoelectron spectroscopy tests indicated that voltage, concentration of electrolyte and duration of electrochemical treatment determined the distribution density of catalyst nanoparticles by controlling the concentration of the functional groups, while the diameter of catalyst particles was decided by the concentration of Fe(NO3)3 and CO(NH2)2. Besides, the diameter of catalyst particles could be modulated by adding Al(NO3)3 in the solution of the catalyst precursor. At the same time, to avoid cementite produced during the calcination and reduction process, the temperature should be controlled below 773 K. Scanning electron microscopy observations indicated that well-dispersed in situ grown CNTs could be obtained after CFF had been chemical oxidised at the voltage of 10 V for 10 s with 0.02 M NH4HCO3 as electrolyte and followed by catalyst deposition.

Pr0.6Sr0.4CoO3−δ electrocatalyst for solid oxide fuel cell cathode introduced via infiltration

Effects of infiltrated Pr0.6Sr0.4CoO3−δ (PSCo) electrocatalyst on SOFC cathode performance have been studied. Nano-sized particulate catalysts, deposited on surfaces of a composite cathode of Sm2O3 doped CeO2 (SDC) and La1−xSrxCo1−yFeyO3−δ (LSCF), are assumed to effectively widen active sites, or triple phase boundaries, for the oxygen reduction reaction. Area specific resistance of commercially available cells has been decreased by 36–40% with the addition of 23wt% PSCo electrocatalyst on cathode. Analysis of the impedance spectra demonstrates that PSCo electrocatalyst plays a significant role in dissociation of oxygen molecules and adsorption of oxygen atoms into the cathode. A total of 200h operation of the cells demonstrated that catalytic activity of PSCo has not been significantly degraded. Simultaneous operations of multiple cells using a parallel-cell testing system have made it possible to compare the performance of several cells with high reliability.

Nano-sized silica supported Me2Si(Ind)2ZrCl2/MAO catalyst for ethylene polymerization

Nano-sized and micro-sized silica particles were used to support a zirconocene catalyst [racemic-dimethylsilbis(1-indenyl)zirconium dichloride], with methylaluminoxane as a cocatalyst. The resulting catalyst was used to catalyze the polymerization of ethylene in the temperature range of 40–70°C. Polyethylene samples produced were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Nano-sized catalyst exhibited better ethylene polymerization activity than micro-sized catalyst. At the optimum temperature of 60°C, nano-sized catalyst's activity was two times the micro-sized catalyst's activity. Polymers obtained with nano-sized catalyst had higher molecular weight (based on GPC measurements) and higher crystallinity (based on XRD and DSC measurements) than those obtained with micro-sized catalyst. The better performances of nano-sized catalyst were attributed to its large external surface area and its absence of internal diffusion resistance. SEM indicated that polymer morphology contained discrete tiny particles with thin long fiberous interlamellar links. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

3-93-1 バイオディーゼル燃料合成用固体塩基触媒の微粒子化(Session3 バイオマス等,ポスター発表)

3-93-1 バイオディーゼル燃料合成用固体塩基触媒の微粒子化(Session3 バイオマス等,ポスター発表)

Steam Reforming of Glycerol into Hydrogen Over Nano-Size Ni-Based Hydrotalcite-Like Catalysts

Steam reforming (SR) of glycerol for the production of hydrogen was investigated over the nano-sized Ni-based catalysts. The Ni-based catalysts were prepared by solid phase crystallization and impregnation methods, and characterized by N2 physisorption, CO chemisorption, XRD, SEM, and TEM techniques. The Ni/gamma-Al2O3 catalyst showed higher conversion and H2 selectivity. However, it was slowly deactivated due to the carbon formation on the surface of catalyst and the sintering. It was found that the Ni based hydrotalcite-like catalyst (spc-Ni/MgAl) showed higher catalytic activity to prevent carbon formation than Ni/gamma-Al2O3 catalyst in the SR of glycerol.

Effect of stress on dissolution/precipitation of platinum: Implications concerning core–shell catalysts and cathode degradation in proton exchange membrane fuel cells

Effect of applied stress on dissolution/precipitation of platinum was investigated. Two platinum wires/foils were partially immersed in a PtCl 4 solution in DMSO. A tensile load was applied to one wire/foil and the other one was left load free. The wire/foil subjected to a tensile load developed a positive potential (became cathodic) with respect to the unstressed wire/foil. This observation suggests that under a tensile stress, the chemical potential of Pt decreases. This result suggests design strategies for core–shell catalysts used in proton exchange membrane fuel cells (PEMFCs). Nanosize catalyst particles are under compression due to the Gibbs–Thompson effect. Core–shell catalysts have additional stresses in the shell depending upon lattice parameters of the core and the shell. The present results suggest that stable core–shell catalysts for PEMFC with Pt shell should be designed such that the shell is under a tensile stress (or reduced compression compared to monolithic catalyst particles). The present results also suggest that from the standpoint of stability, the lattice parameter of the core should be larger than that of the shell.

Study on Unsupported Nano-MoS&lt;sub&gt;2&lt;/sub&gt; Catalyst for Clean Fuel

In the work, nano-sized MoO3 and unsupported MoS2 hydro desulfurization catalysts were synthesized using a novel hydrothermal reduction method. The influences of the temperature and the synthetic methods on the growth morphology of molybdenum disulfide were systematically investigated. It was found that the MoS2 fibers were easy to be bended and had lots of defects, which increased the number of active sites on the catalyst and easily met the requirements of deep hydrotreating desulfurization of diesel oil.

Lanthanum cobaltite perovskite supported onto mesoporous zirconium dioxide: Nature of active sites of VOC oxidation

Novel catalytic nano-sized materials based on LaCoO x perovskite nanoparticles incapsulated in the mesoporous matrix of zirconia were prepared, characterized by physicochemical methods and tested in complete methanol oxidation. LaCoO x nanoparticles were prepared inside the mesopores of ZrO 2 by decomposition of bimetallic La–Co glycine precursor complexes. The catalysts have been studied by diffuse-reflectance FTIR-spectroscopy using such probe molecules as CO, CD 3CN and CDCl 3 to test low-coordinated metal ions. At low temperatures of decomposition of complexes (up to 400 °C), low-coordinated Co 3+ ions predominate in the LaCoO x nanoparticles, whereas basically Co 2+ ions are found upon increasing the decomposition temperature to 600 °C. The novel nano-sized perovskite catalysts exhibit a very high catalytic activity in the abatement of volatile organic compounds present in air, like methanol and light hydrocarbons.

Pt/Cr and Pt/Ni Catalysts for Oxygen Reduction Reaction: To Alloy or Not to Alloy?

Bimetallic systems such as Pt-based alloys or non-alloys have exhibited interesting catalytic properties but pose a major challenge of not knowing a priori how the electronic and chemical properties will be modified relative to the parent metals. In this work, we present the origin of the changes in the reactivity of Pt/Cr and Pt/Ni catalysts, which have been of wide interest in fuel cell research. Using spin-polarized density functional theory calculations, we have shown that the modification of Pt surface reactivity in Pt/Ni is purely of geometric origin (strain). We have also found that the Pt-Ni bonding is very weak, which explains the observed instability of Pt-Ni catalysts under electrochemical measurements. On the other hand, Pt/Cr systems are governed by strong ligand effect (metal-metal interaction), which explains the experimentally observed reactivity dependence on the relative composition of the alloying components. The general characteristics of the potential energy curves for O2 dissociative adsorption on the bimetallic systems and the pure Pt clarify why the d-band center still works for Pt/Cr despite the strong Pt-Cr bonding and high spin polarization of Pt d-states. On the basis of the above clarifications, viable Pt-Cr and Pt-Ni structures, which involve nano-sized alloys and non-alloy bulk catalyst, which may strike higher than the currently observed oxidation reduction reaction activity are proposed.

The nanosize catalysts role in the modern hydroprocesses

Introduction of the modern technological procedures operating the catalytic systems with different nanosized characteristics is the only way to fabricate components of commercial oils that meet the current requirements. Specifications to the individual catalysts, which form a catalytic system, differ both in nanostructural features of the support porosity and in distribution of nanosized active site. These specifications are related to the purpose of the process and the role of the catalyst in the process.

Study of Methanol‐tolerant Oxygen Reduction Reaction at Pt–Bi/C Bimetallic Nanostructured Catalysts

AbstractThe nanostructured platinum–bismuth catalysts supported on carbon (Pt3Bi/C, PtBi/C and PtBi3/C) were synthesised by reducing the aqueous metal ions using sodium borohydride (NaBH4) in presence of a microemulsion. The amount of metal loading on carbon support was found to be 10 wt.‐%. The catalyst materials were characterised by X‐ray diffraction (XRD), X‐ray fluorescence (XRF), transmission electron microscope (TEM) and electroanalytical techniques. The Pt3Bi/C, PtBi/C and PtBi3/C catalysts showed higher methanol tolerance, catalytic activity for oxygen reduction reaction (ORR) than Pt/C of same metal loading. The electrochemical stability of these nano‐sized catalyst materials for methanol tolerance was investigated by repetitive cycling in the potential range of –250 to 150 mVMSE. Bi presents an interesting system to have a control over the activity of the surface for MOR and ORR. All Pt–Bi/C catalysts exhibited higher mass activities for oxygen reduction (1–1.5 times) than Pt/C. It was found that PtBi/C catalyst exhibits better methanol‐tolerance than the other catalysts.

Nano-sized Fe-metal catalyst on ZnO–SiO 2: (photo-assisted deposition and impregnation) Synthesis routes and nanostructure characterization

A nano-sized Fe metal on ZnO–SiO 2 was synthesized using the photo-assisted deposition (PAD) and impregnation routes. The obtained samples were characterized by a series of techniques including X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, N 2 adsorption, extended X-ray absorption fine structure (EXAFS), and transmission electron microscopy (TEM). Photocatalytic reactivity using Fe–ZnO–SiO 2 catalysts under visible-light condition on the degradation of methylene blue dye was evaluated. The results of characterization reveal, a notable photocatalytic activity of PAD:Fe–ZnO–SiO 2 which was about 9 and 12 times higher than that of Img:Fe–ZnO–SiO 2 and ZnO–SiO 2, respectively.

Characteristics of Pt, Pt-Ru and Pt-CeO_2 Catalysts Supported on Carbon Nanotubes for Methanol Fuel Cell

Nanosized Pt, Pt-Ru and Pt-<TEX>$CeO_2$</TEX> electrocatalysts supported on acid-treated carbon nanotube (CNT) were synthesized by microwave-assisted heating of polyol process using <TEX>$H_2Cl_6Pt{\cdot}6H_2O$</TEX>, <TEX>$RuCl_3$</TEX>, <TEX>$CeCl_3$</TEX> precursors, respectively, and were characterized by XRD and TEM. And then the electrochemical activity of methanol oxidation for catalyst/CNT nanocomposite electrodes was investigated. The microwave assisted polyol process produced the nano-sized crystalline catalysts particles on CNT. The size of Pt supported on CNT was 7~12 nm but it decreased to 3~5 nm in which 10wt% sodium acetate was added as a stabilizer during the polyol process. This fine Pt catalyst particles resulted in a higher current density for Pt/CNT electrode. It was also found that 10 nm size of PtRu alloys were formed by polyol process and the onset potential decreased with Ru addition. Cyclic voltammetry analysis revealed that the <TEX>$Pt_{75}Ru_{25}/CNT$</TEX> electrode had the highest electrochemical activity owing to a higher ratio of the forward to reverse anodic peak current. And the chronoamperemetry test showed that <TEX>$Pt_{75}Ru_{25}$</TEX> catalyst had a good catalyst stability. The activity of Pt was also found to be improved with the addition of <TEX>$CeO_2$</TEX>.

Microwave-Assisted Rapid and efficient Reduction of Aromatic Nitro Compounds to Amines with Propan-2-ol over Nanosized Perovskite-type SmFeO3 powder as a New Recyclable Heterogeneous Catalyst

Nanosized perovskite-type SmFeO3 powder, prepared through the thermal decomposition of Sm[Fe(CN)6].4H2O with an average particle diameter of 28 nm and a specific surface area of 42 m2 g−1, was used as a recyclable heterogeneous catalyst for the efficient and selective reduction of aromatic nitro compounds into the corresponding amines by using propan-2-ol as a hydrogen donor (reducing agent) and KOH as a promoter under microwave irradiation. This highly regio- and chemoselective catalytic method is fast, clean, inexpensive, high yielding and also compatible with the substrates containing easily reducible functional groups. In addition, the nanosized SmFeO3 catalyst can be reused without loss of activity.

Photocatalytic Mechanism of Action of Apatite-Coated Ag/Agbr/Tio2 on Phenol and Escherichia Coli and Bacillus Subtilis Bacteria Under Various Conditions

Multi-component photocatalysts based on apatite-coated Ag/AgBr/TiO2 were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-stal ic. The median ism for deactivation of bacteria in the dark can be related to the linkage between the phosphate group of the composite and the outer membrane of the cell. The photocatalytic destruction of bacteria under visible I ight indicates that attachment of the catalysts to the outer wall of the cell causes them to destroy effectively the cell wall and inner membrane by various reactive species such as OH, O2 - and 1O2. Thus this effect increases the photoactivity more than two-fold. Oxidation of phenol was also achieved under visible light- and UVA- irradiation using apatite-coated Ag/AgBr/TiO2 powders. Under UVA illumination, the ‘OH produced from the hole of the TiO2 valence band is responsible for the photodegradation of phenol, while under visible light, AgBr acts as the photoactive component of the catalyst, that can not produce’ OH and oxidize the phenol.

Alumina Over-coating on Pd Nanoparticle Catalysts by Atomic Layer Deposition: Enhanced Stability and Reactivity

ALD Alumina was utilized as a protective layer to inhibit the sintering of supported nano-sized ALD Pd catalysts in the methanol decomposition reaction carried out at elevated temperatures. The protective ALD alumina layers were synthesized on Pd nanoparticles (1-2 nm) supported on high surface area alumina substrates. Up to a certain over-coat thickness, the alumina protective layers preserved or even slightly enhanced the catalytic activity and prevented sintering of the Pd nanoparticles up to 500 C.