Simultaneous reduction of particulate matter and NOx emissions using 4-way catalyzed filtration systems

The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NOx and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NOx and DPM control performance of miniature 4WCFS made from acicular mullite, an advanced ceramic material (ACM), that were challenged with diesel exhaust. The impact of catalyst loading and substrate porosity on catalytic performance of the NOx trap was evaluated. Simultaneously with NOx measurements, the real-time solid particle filtration performance of catalyst-coated standard and high porosity filters was determined for steady-state and regenerative conditions. The use of high porosity ACM 4-way catalyzed filtration systems reduced NOx by 99% and solid and total particulate matter by 95% when averaged over 10 regeneration cycles. A "regeneration cycle" refers to an oxidizing ("lean") exhaust condition followed by a reducing ("rich") exhaust condition resulting in NOx storage and NOx reduction (i.e., trap "regeneration"), respectively. Standard porosity ACM 4-way catalyzed filtration systems reduced NOx by 60-75% and exhibited 99.9% filtration efficiency. The rich/lean cycling used to regenerate the filter had almost no impact on solid particle filtration efficiency but impacted NOx control. Cycling resulted in the formation of very low concentrations of semivolatile nucleation mode particles for some 4WCFS formulations. Overall, 4WCFS show promise for significantly reducing diesel emissions into the atmosphere in a single control device. © 2013 American Chemical Society.

Selective formation of aromatic amines by selenium-catalyzed reduction of aromatic nitro compounds with CO/H2O under atmospheric pressure

An efficient method for the catalytic reduction of aromatic nitro compounds to the corresponding aromatic amines is reported. In the presence of selenium as a catalyst, the aromatic nitro compounds are quantitively reduced by CO/H2O to form the corresponding amines under atmospheric pressure. The reduction occurs in high selectivity regardless of other reducible functionalities present on the aromatic ring. There exists a phase transfer process of the catalyst selenium in the reaction. (C) 2004 Elsevier B.V. All rights reserved.

Promotional effect of colloidal alumina on the activity of the In/HZSM-5 catalyst for the selective reduction of NO with methane

Colloidal alumina was used to improve the activity of an In/HZSM-5 catalyst for the selective reduction of NO with CH4 in the excess of oxygen. Compared with In/HZSM-5, the In/HZSM-5/Al2O3 catalyst showed higher activity in a wide range of reaction temperatures. It is visualized that a synergetic effect between In/HZSM-5 and Al2O3 enhances the conversion of NOx. The addition of Al2O3 improved the conversion of NO to NO2 and facilitated the activation of methane. An In/HZSM-5/Al2O3 pre-treated with steam for 15 h at 700 degreesC still showed a high activity for the removal of NOx with methane, while an In/HZSM-5 similarly pre-treated with steam showed a lower activity than the fresh sample. The activity of the In/HZSM-5/Al2O3 catalyst could be restored completely after water vapor was removed from the feed gas. Furthermore, it was found that the In/HZSM-5/Al2O3 remained fairly active under high GHSV and O-2 concentration conditions. It was also interesting to find that an increase in NO content could enhance the conversion of methane, and this illustrates that the existence of NO is beneficial for the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

Reduction of NO by CH4 with microwave heating

The reduction of NO by CH4 in the presence of excess O-2 over Co/HZSM-5, Ni/HZSM-5 and Mn/HZSM-5 catalysts with microwave heating was studied. By comparing the activities of the catalysts in the microwave heating mode with that in the conventional reaction mode, it was demonstrated that microwave heating could greatly reduce the reaction temperature, and could clearly expand the temperature window of the catalysts. Especially for the Co/HZSM-5 catalyst, the maximum conversion of NO to N-2 in the conventional reaction mode was consistent with that in the microwave heating mode. However, the temperature window for the maximum conversion in the microwave heating mode was from 260 to 360degreesC instead of a temperature of 420degreesC in the conventional reaction mode. The results suggest that microwave heating has a novel effect in the reduction of NO.

Green synthesis of 1-2 nm gold nanoparticles stabilized by amine-terminated ionic liquid and their electrocatalytic activity in oxygen reduction

Stable gold nanoparticles with average size 1.7 nm synthesized by an amine-terminated ionic liquid showed enhanced electrocatalytic activity and high stability.

Structure characterization and physical properties of a complex with supramolecular architectures Co-2(2,6-DPC2Co(H2O)5 center dot 2H(2)O (DPC=2,6-pyridinedicarboxylate)

Reaction of 2,6-pyridinedicarboxylic with CoCl2 . 6H(2)O in aqueous solution give rise to a three-dimensional Complex CO2(2,6-DPC)(2)Co(H2O)(5).2H(2)O (DPC = 2,6-pyridinedicarboxylate) 1. It has been characterized by elemental analyses, infrared spectra (IR) spectrum, thermogravimetric (TG) analysis, EPR spectrum, and single crystal X-ray diffraction. The complex crystallizes in the P2(1)/c space group with a = 8.3906(3) Angstrom, b = 27.4005(8) Angstrom, c = 9.6192(4) A, alpha = 90.00degrees, beta = 98.327(2)degrees, gamma = 90.00degrees, V = 2188.20(14) Angstrom(3), Z = 4. There are two types of cobalt environments: Co(1) is coordinated by four oxygen atoms from four carboxyl groups and two nitrogen 2 atoms which are all from pdc(2). Co(2) is coordinated by six oxygen atoms, five from coordinated water molecules and one from a carboxyl of pdc(2) - of which the other oxygen atom is linked to the Co(1). The extensive intermolecular hydrogen bonds are formed in the crystal by means of the five coordinated water molecules.

Electrocatalytic reduction of oxygen at multi-walled carbon nanotubes and cobalt porphyrin modified glassy carbon electrode

The multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode exhibited electrocatalytic activity to the reduction of oxygen in 0.1 M HAc-NaAc (pH 3.8) buffer solution. Further modification with cobalt porphyrin film on the MWNTs by adsorption, the resulted modified electrode showed more efficient catalytic activity to O-2 reduction. The reduction peak potential of O-2 is shifted much more positively to 0.12 V (vs. Ag/AgCl), and the peak current is increased greatly. Cyclic voltammetry (CV), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), were used to characterize the material and the modified film on electrode surface. Electrochemical experiments gave the total number of electron transfer for oxygen reduction as about 3, which indicated a co-exist process of 2 electrons and 4 electrons for reduction of oxygen at this modified electrode. Meanwhile, the catalytic activities of the multilayer film (MVVNTs/CoTMPyP)(n) prepared by layer-by-layer method were investigated, and the results showed that the peak current of O-2 reduction increased and the peak potential shifted to a positive direction with the increase of layer numbers.

The reduction of Eu3+ to Eu2+ in BaMgSiO4 : Eu prepared in air and the luminescence of BaMgSiO4 : Eu2+ phosphor

The reduction of Eu3+ to Eu2+ in air has been observed in a silicate matrix for the first time in BaMgSiO4:Eu prepared by high-temperature solid-state reaction. Emission and excitation spectra were employed to detect the presence of Eu2+ ions in the compound and this reduction was explained by a charge compensation model proposed previously. In BaMgSiO4 : Eu2+, Eu2+ ions occupy three different lattice sites by substitution for Ba2+ ions. Eu2+ ions on Ba(1) and Ba(2) sites gave emissions at about 500 nm while that on Ba(3) site showed an emission band at 398 nm. All the emissions of Eu2+ ions in BaMgSiO4 : Eu2+ were not quenched at room temperature.

The photo-induced decarbonylation of Cp ' M(NO)(CO)(2) (M = Cr, Mo, W) with diorgano dichalcogenides (R2E2; E = S, Se; R = Me, Ph)

The photo-induced decarbonylation of Cp'Cr(NO)(CO)(2) (1a) in MeCN solution in the presence of R2E2 (E = S, Se; R = Me, Ph) leads to the formation of chalcogenolato-bridged binuclear complexes Cp-2'Cr-2(NO)(2)(mu -ER)(2) [E = S; R = Me (2a), Ph (3a); E = Se, R = Me (4a), Ph (5a)] while reactions between Cp'M(NO)(CO)(2) [M = Mo (1b), W (1c)] and Ph2E2 (E = S, Se) result in mononuclear complexes Cp'M(NO)(EPh)(2) [M = Mo; E = S (9b), Se (10b); M = W, E = S (11c), Se (12c)]. The corresponding reactions of (1b) with Me2E2 (E = S, Se) yielded both mono and binuclear complexes: Cp'Mo(NO)(SeMe)(2) (8b), Cp-2'Mo-2(NO)(2)(mu -EMe)(2) [E = S (6b), Se (7b)]. The new complexes have been characterized by i.r., H-1-, C-13-n.m.r. spectra and by electron-impact mass spectrometry.

Co-Cu-Al mixed oxides derived from hydrotalcite-like compound for NO reduction by CO

Various hydrotalcite based catalysts were prepared for catalytic removal of NO (NO reduction by CO). The general formula of hydrotalcite compounds (HTLc) was Co-Cu-Al-HTLc. Precalcination of these materials at 450 degrees C for NO reduction by CO, was necessary for catalytic activity. All catalysts except Co-A1 and Cu-Al have very good activity at lower temperature for NO reduction by CO. All samples were characterized by XRD and BET. The tentative reaction mechanism was also proposed.