Search

The three way catalyst NOx trap catalyst (TWC-NT) is consisted of a conventional three way catalyst (TWC) compositions and NOx storage material (NSM) to mitigate NOx breakthrough occurred during the fuel cut event to improve fuel economy of stoichiometric (A/F = 14.6) gasoline powered vehicles. Typical fuel cut operation generates very lean exhaust mixture that oxidizes the catalyst surface in TWC system, and NOx is slipped on the oxygen rich catalyst surface when the engine is switched back to the stoichiometric air to fuel ratio. The fully batch formulated TWC and TWC-NT catalyst were prepared and aged on engine dynamometer equivalent to 150,000 miles at underfloor location. The aged catalysts was evaluated at LEV-3 SULEV30 passenger car to check their effects on NOx efficiency, fuel saving and N2O suppression ability. The results revealed TWC-NT showed higher NOx removal performance by 71 % with multiple the fuel cuts and O2 purge period through the thermally enhanced NOx storage and reduction function, and 2 % higher fuel economy on FTP-75 cycle than the conventional TWC. Also the catalyst had good N2O suppression ability by the removal of NOx as the main reactant of N2O formation in the exhaust gas reactions over catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous silica KIT-6-, SBA-15-, and MCM-41-supported Ni catalysts (Ni/KIT-6, Ni/SBA-15, and Ni/MCM-41) were prepared via impregnation method and studied for CO2 reforming of CH4. The catalysts were characterized by X-ray diffraction analysis, N2 physisorption measurements, scanning electron microscopy, transmission electron microscopy, and temperature-programmed oxidation (O2-TPO). The Ni/KIT-6 catalyst exhibited higher catalytic activity and long-term stability compared with Ni/SBA-15 or Ni/MCM-41. The conversion of CH4 and CO2 over Ni/KIT-6 was 99 and 99 %, respectively. The superior catalytic behavior of Ni/KIT-6 is closely related to the large-pore cubic Ia3d structure of KIT-6, which enhanced dispersion of Ni nanoparticles, reduced carbon deposition, and increased diffusion of reactant and products.Graphical Abstract: [ABSTRACT FROM AUTHOR]

We report on a facile synthesis of the ordered mesoporous carbon (OMC) materials with systematically controlled microporosity and mesoporosity simultaneously through the nano-replication route using phosphoric acid as the acid catalyst and activation agent. The use of phosphoric acid affects the pore structures of OMC materials, such as the formation of numerous micropores by activation of the carbon framework and the enlargement of mesopores by spontaneous phase separation during the carbonization. The mesopore sizes, surface areas, total pore volumes, and micropore volumes of the OMC materials are highly dependent on the phosphoric acid content and can be systematically controlled in the range 3.7-7.5 nm, 1027-2782 m2 g-1, 1.12-3.53 cm3 g-1 and 0.34-0.95 cm3 g-1, respectively. OMC materials with systematically controlled pore structures were successfully synthesized using phosphoric acid as the carbonization catalyst and mesoporous silica materials with cubic Ia3 d and 2-D hexagonal mesostructures as the templates. The phosphoric acid in the synthesis of ordered mesoporous carbon materials acts as the chemical activating agent for micropore generation of the carbon framework and pore-expanding agent for controlling of mesopore size, in addition to functioning as the acid catalyst. The present synthesis pathway is very useful for preparing OMC materials with tunable mesopore sizes and well-developed microporosities at the same time. [ABSTRACT FROM AUTHOR]

Platinum catalysts loaded on a hybrid support, composed of HZSM-48 and pseudoboehmite, were applied to the synthesis of benzene through methylcyclopentane (MCP) reforming in order to investigate the effect of the addition of pseudoboehmite to Pt/HZSM-48 for ring-enlargement reaction. A total of 0.5 wt% of platinum was impregnated on the hybrid support by using the incipient wetness method. Catalyst characterization was performed with nitrogen sorption, X-ray diffraction, temperature-programmed desorption of NH3, and infrared spectroscopy of adsorbed pyridine. It was found that mesoporous structures were well-developed in Pt/(HZSM-48 + pseudoboehmite) catalyst as a result of the pseudoboehmite addition, of which the average pore size was in the range of 7–8 nm. The presence of pseudoboehmite in the catalyst increases the total amount of acid sites and weakens the acid strength, compared with those of the Pt/HZSM-48 catalyst. Lewis acid sites were more abundant than Brönsted acid sites over the Pt/(HZSM-48+pseudoboehmite) catalysts. It was found that selectivity to the ring-enlargement reaction is dominant over selectivity to the ring-opening reaction over the Pt/(HZSM-48 + pseudoboehmite) catalysts. The benzene yield over Pt/(HZSM-48 + pseudoboehmite, 1:1) catalyst reached 65.1% at 450 °C and 0.3 h−1. As well as being influenced by the mesoporous structure, the higher activity and selectivity in MCP reforming was also determined by appropriate acidity of the Pt/(HZSM-48 + pseudoboehmite) catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Manganese oxide catalysts prepared by a precipitation method with various precipitants were investigated for the low temperature selective catalytic reduction (SCR) of NOx with NH3 in the presence of excess O2. Various characterization methods such as N2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and X-ray absorption near edge structure (XANES) were conducted to probe the physical and chemical properties of MnOx catalysts. The active MnOx catalysts, precipitated with sodium carbonate and calcined in air at moderate temperatures such as 523K and 623K, have the high surface area, the abundant Mn4+ species, and the high concentration of surface oxygen on the surface. The amorphous Mn3O4 and Mn2O3 were mainly present in this active catalyst. The carbonate species appeared to help adsorb NH3 on the catalyst surface, which resulted in the high catalytic activity at low temperatures. [Copyright &y& Elsevier]

Emissions from diesel engines, including hydrocarbons (HCs), carbon monoxide (CO), and nitric oxide (NO), cause serious environmental and human health problems. Diesel oxidation catalysts (DOCs) are drawing attention for their ability to eliminate such harmful exhausts effectively. Here, we report significantly improved activities of Pt-based catalysts, which are widely used as DOCs, in the oxidation of HC, CO, and NO x after Mn addition. Mn-doped Pt/Al 2 O 3 showed significantly lower light-off temperatures in the oxidation of HC, CO, and NO x than those of the unmodified Pt/Al 2 O 3 catalysts, by as much as 30 °C. The size of Pt particles was reduced from 71 nm to 33 nm after Mn addition, as evidenced by X-ray diffraction analysis and transmittance electron microscopy. Additionally, the interaction between CO and Pt on Mn-doped catalysts was weakened, and the CO adsorbed on Pt was readily oxidized even at room temperature, as confirmed by diffuse reflectance infrared Fourier-transform spectroscopy and CO temperature-programmed desorption experiments. The results of this study provide insights towards the improvement of the activity of Pt-based DOCs used for HC, CO, and NO x oxidation, by enhancing the fundamental understanding of the Pt nature promoted with Mn. [Display omitted] • Manganese improved activities of Pt-based catalysts in HC, CO, and NO x oxidation. • The size of Pt particles is significantly reduced after Mn addition. • Mn addition weakened the CO adsorption strength of Pt-based catalysts. [ABSTRACT FROM AUTHOR]

The catalytic oxidation of toluene with ozone at room temperature was carried out over hierarchically ordered mesoporous catalysts (CeO 2 (meso), Mn 2 O 3 (meso), ZrO 2 (meso), and γ-Al 2 O 3 (meso)) and Al 2 O 3 with various textural properties and phases (γ-Al 2 O 3 (meso), γ-Al 2 O 3 (13 nm), and α-Al 2 O 3) to examine the effects of the nature of the catalyst on the catalytic activity. The catalysts were characterized by N 2 -physisorption measurements, powder X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy. Among the ordered mesoporous catalysts, γ-Al 2 O 3 (meso) had the highest toluene removal efficiency because of its highest surface area and pore volume, which in turn was selected for further investigation. Manganese (Mn) was introduced to various Al 2 O 3 to improve the toluene removal efficiency. Comparing the Mn-loaded catalysts supported on various Al 2 O 3 with different crystalline phases or pore structures, Mn/γ-Al 2 O 3 (meso), had the highest catalytic activity as well as the highest CO 2 /CO ratio. The higher activity was attributed to the larger surface area, weaker interaction between Mn and Al 2 O 3 , and larger portion of Mn 2 O 3 phase. The increase in ozone concentration led to an improvement in the carbon balance but this enhancement was insufficient due to the deposition of by-products on the catalyst. After long term tests at room temperature, the reaction intermediates and carbonaceous deposits of the used catalysts were identified. • Ordered mesoporous materials, γ-Al 2 O 3 , CeO 2 , Mn 2 O 3 , ZrO 2 , were used. • Effect of the crystalline phase and pore structure of Mn/Al 2 O 3 was investigated. • The catalytic activity of toluene O 3 oxidation over Mn/γ-Al 2 O 3 (meso) was highest. • The reaction intermediates and carbon deposits on the used catalysts were identified. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous silica KIT-6-, SBA-15-, and MCM-41-supported Ni catalysts (Ni/KIT-6, Ni/SBA-15, and Ni/MCM-41) were prepared via impregnation method and studied for CO2 reforming of CH4. The catalysts were characterized by X-ray diffraction analysis, N2 physisorption measurements, scanning electron microscopy, transmission electron microscopy, and temperature-programmed oxidation (O2-TPO). The Ni/KIT-6 catalyst exhibited higher catalytic activity and long-term stability compared with Ni/SBA-15 or Ni/MCM-41. The conversion of CH4 and CO2 over Ni/KIT-6 was 99 and 99 %, respectively. The superior catalytic behavior of Ni/KIT-6 is closely related to the large-pore cubic Ia3d structure of KIT-6, which enhanced dispersion of Ni nanoparticles, reduced carbon deposition, and increased diffusion of reactant and products.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Pt/CeO 2 has gained much attention for their high activity in low-temperature (LT) water-gas shift (WGS) reaction. However, the inclusion of H 2 in the feed as in the practical reaction condition significantly degrades the LT-WGS activity of the Pt/CeO 2 catalysts. In this contribution, the activity of Pt/CeO 2 catalyst under the feed gas containing excess H 2 (20 vol% of H 2) was enhanced more than three times by forming CeO 2 nano-patches on Pt nano-particles. Both in-situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculation results indicate that dissociated H 2 on the Pt nano-particle inhibits the activity of the Pt/CeO 2 catalysts by occupying the active sites (Pt nano-particle-CeO 2 interface). On the other hand, thin CeO 2 nano-patches on Pt nano-particle suppressed the H 2 dissociation. As a result, the WGS reactivity of the active Pt nano-particle-CeO 2 interface was less affected by H 2 , granting the catalysts the high activity under the practical reaction conditions. [Display omitted] • CO-FTIR band on Pt NP-CeO 2 interface is assigned, which appears at ~2090 cm−1. • CeO 2 nano-patches are formed on Pt NPs by controlled reductive treatment. • The LT-WGS activity of Pt NP/CeO 2 is significantly inhibited by H 2 in the feed. • CeO 2 nano-patches inhibit the H 2 activation on Pt NP as confirmed by CO-FTIR. • CeO 2 nano-patches greatly enhance the LT-WGS activity under practical condition. [ABSTRACT FROM AUTHOR]

• Highly ordered mesoporous WOx/SnO2 catalysts have been applied to the glycerol acetalization reaction. • Mesoporous WOx/SnO2 catalysts exhibited excellent catalytic performance in batch-type and continuous flow-type processes for catalytic synthesis of solketal from glycerol. • In a batch type process, 100% glycerol conversion and a solketal yield of 97.4% were achieved. Highly ordered WO x /mesoporous SnO 2 (WO x /meso‑SnO 2) catalysts with varying WO x loadings of (5 ∼ 20) wt% displaying excellent catalytic performance were demonstrated in the acetalization of glycerol with acetone. The synthesized catalysts were analyzed using various techniques including X-ray diffraction, N 2 -isotherm, electron microscopy, H 2 temperature programmed reduction, raman spectroscopy, and thermogravimetric analysis. For the acetalization of glycerol with acetone, the most active catalyst was found to be WO x /meso‑SnO 2 with 20 wt% WO x , and the maximum conversion of glycerol (100%) was obtained after 2 h at 20 °C, providing 97.4% selectivity (97.4% yield) for the five-membered product (solketal), due to the presence of a large number of acidic sites on the surface of the catalyst. The catalytic activity of 20 wt% WO x /meso‑SnO 2 was also studied in a flow reactor. Tests were carried out at 30 °C, acetone/glycerol=30, WHSV=(4 or 8) h −1, and atmospheric pressure for 24 h. The catalytic results showed that, when the WHSV was 4 h −1, after 24 h of time-on-stream, both the glycerol conversion of (100 to 97.9)% and solketal yield of (97.5 to 93.6)% slightly decreased. This result suggests the potential of the 20 wt% WO x /meso‑SnO 2 catalyst for the industrial acetalization of glycerol. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this work, catalytic cracking of biomass waste oil fractions separated from food waste leachate was performed using microporous catalysts, such as HY, HZSM-5 and mesoporous Al-MCM-48. The experiments were carried out using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) to allow the direct analysis of the pyrolytic products. Most acidic components, especially oleic acid, contained in the food waste oil fractions were converted to valuable products, such as oxygenates, hydrocarbons and aromatics. High yields of hydrocarbons within the gasoline-range were obtained when microporous catalysts were used; whereas, the use of Al-MCM-48, which exhibits relatively weak acidity, resulted in high yields of oxygenated and diesel-range hydrocarbons. The HZSM-5 catalyst produced a higher amount of valuable mono aromatics due to its strong acidity and shape selectivity. Especially, the addition of gallium (Ga) to HZSM-5 significantly increased the aromatics content. [ABSTRACT FROM AUTHOR]

Abstract: The ordered mesoporous carbons (OMCs) with various primary particle sizes were synthesized and the effect of the particle size of the OMC supports on their performance for the oxygen reduction reaction (ORR) in direct methanol fuel cells was investigated. The ordered mesoporous silica (OMS) templates with particle sizes of 100, 300, and 700nm (OMS-100, -300, and -700) were synthesized by changing the synthesis pH and Na content in the silica source, sodium silicate. The OMCs with similar particle sizes and morphologies (OMC-100, -300, and -700) were faithfully replicated by using the corresponding OMSs as templates and phenanthrene as a carbon source. Structural characterizations revealed that three OMCs exhibit uniform mesopores of 4–5nm and BET surface areas of 600–800m2 g−1. The Pt nanoparticles of ca. 3nm were supported onto these OMCs and the resulting Pt/OMC catalysts were tested for the ORR. The three OMC supported catalysts exhibited the catalyst utilization efficiencies and ORR activities of similar range, with the values of Pt/OMC-300 catalyst being slightly higher than the other two catalysts. [Copyright &y& Elsevier]

• 0.6 nm thick continuous TiO 2 coating on carbon is achieved by sonochemistry. • Investigation the effects of TiO 2 undercoating to the electrocatalysis for ORR. • The Pt and TiO 2 contact exert the SMSI effect to result in higher activity. • The durability is enhanced due to the protection of carbon by inert TiO 2 coating. The lack of highly efficient and stable electrocatalysts for oxygen reduction reaction (ORR) has been hindering the advances in proton exchange membrane fuel cells (PEMFCs). Harnessing the strong metal–support interactions (SMSI) effects at the interface between a metal oxide and a noble metal is one approach investigated to address these issues. In this work, TiO 2 coating with 0.6 nm in thickness, uniformly formed on the entire surface of a carbon material is synthesized by a sonochemical reaction method. Deposition of Pt nanoparticles (NPs) on TiO 2 coated carbon (TiO 2 /C) produces Pt/TiO 2 /C catalysts with enhanced activity and durability for ORR. Pt/TiO 2 /C(U) whose Pt NPs are formed by sonochemical reaction shows mass activity (MA) and specific activity (SA) 2.9 and 2.6 times, respectively, higher than Pt/C catalyst. More importantly, Pt/TiO 2 /C(U) catalyst exhibits a superior long-term durability. After 50,000 cycles of durability test, it retains 51.4 %/61.3% of initial MA/SA. Pt/TiO 2 /C(R) whose Pt NPs are formed by chemical reduction also shows enhanced activity and durability than Pt/C, but with less extents than Pt/TiO 2 /C(U). The significantly enhanced ORR performance of Pt/TiO 2 /C catalysts is attributed to the SMSI effect between TiO 2 coating and Pt NPs plus bifunctional mechanism from the TiO 2 surface around Pt NPs. The enhance durability can be explained as the protection of carbon by chemically inert TiO 2 coating. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Pt/C catalyst was prepared by the formic acid reduction method (FARM) using mesoporous carbon supports with submicron-scale particle size, which was synthesized by the nano-replication technique using mesoporous silica (MSU-H) as templates. The average size of the Pt particles, calculated from the Pt(111) peak by Scherrer equation, was found to be 3.3nm. The chemical stabilities of Pt/C catalysts and polymer-coated Pt/C catalysts were examined in distilled water and in strong acidic solutions such as H2SO4 and HClO4. The release amount of Pt in distilled water was found to be at trace levels (<3ppb), which is close to the detection limits of ICP-AES. However, the Pt release greatly increased with time in both H2SO4 and HClO4 solutions and reached a few percent levels in a week. On the other hand, a PVP/PEI-coated Pt/C catalyst showed much better stability that the Pt release was about 0.5% in 3M HClO4 for a week, compared with that of a pristine Pt/C catalyst. [Copyright &y& Elsevier]

Abstract: This paper presents the effect of graphitic character of ordered mesoporous carbons (OMCs) on the performances of OMC supported catalysts for direct methanol fuel cells (DMFC). Two OMC samples with hexagonal mesostructure were prepared from phenanthrene and sucrose by nano-replication method using mesoporous silica as a template. Structural characterizations revealed that both OMCs exhibited large BET surface area and uniform mesopores, while the OMC synthesized from phenanthrene exhibited lower sheet resistance than the OMC derived from sucrose. The Pt nanoparticles were supported on both OMCs with very high dispersion, as the particle size was estimated under 3nm despite high metal loading of 60wt.%. In DMFC single cell test, the OMC supported Pt catalysts exhibited much higher performance than the commercial catalyst, which may be attributed to the high surface area and uniform mesopore networks of OMC. In particular, it was found that the performance of OMC supported catalysts can be significantly enhanced by lowering the resistance of OMC. [Copyright &y& Elsevier]

Abstract: Three catalysts, 1wt.% Pt/Al2O3, 20wt.% Cu/Al2O3, and 1wt.% Pt–20wt.% Cu/Al2O3 were evaluated for the oxidation of NO by O2 and the selective catalytic reduction (SCR) of NO x by NH3 in the absence and presence of H2O. The Pt/Al2O3 catalyst exhibited the largest values in NO oxidation efficiency and NO x removal efficiency among the three catalysts. The presence of H2O caused a drop in the NO oxidation and the SCR activities. The SCR performance was significantly improved when Pt/Al2O3 and Cu/Al2O3 catalysts were employed sequentially in a reactor. The highest SCR performance was achieved using two separate stages: oxidation of NO by O2 over the Pt/Al2O3 catalyst followed by reduction of NO2 by NH3 over the Cu/Al2O3 catalyst. Under the condition with H2O, the two-stage catalyst system showed NO x removal efficiency over 80% at low temperatures below 200°C, which was the highest value among the catalyst systems used in this study. The physical and chemical properties of the catalysts were determined using nitrogen adsorption, XRD, TPR, and pulse CO chemisorption experiments. [Copyright &y& Elsevier]