Selective catalytic reduction of NO by NH3 on titanium pillared montmorillonite

The acidity of a titanium pillared montmorillonite (Ti-PILC) has been modified by two methods of sulfation. The acidic properties of these pillared clays have been studied by temperature-programmed ammonia desorption and FTIR analysis of pyridine adsorption. The catalytic activity of these titanium pillared clays in the selective catalytic reduction (SCR) of NO by NH₃ with or without SO₂ has been investigated. For the three titanium pillared clays, a high resistance to SO₂ presence has been observed.     

Adsorption and catalytic reduction of NO with methanol over carbon and carbon-supported catalysts

The effect of various metal additives on the catalytic performance of carbon during the selective reduction of NO with methanol has been studied in the absence and in the presence of gas-phase oxygen. The mechanism of this reaction in the use of carbon-supported catalysts was studied by means of in situ FTIR combined with the measurements of catalytic activity. In the absence of oxygen, NO is adsorbed in a very small amount on the surface of carbon. The reaction of NO with the products of the methanol decomposition, results in the formation of adsorbed isocyanate (NCO) species at 2229 cm⁻¹. Formation of gaseous NH₃ as a product of the reaction between NO and methanol was observed. Oxygen-containing surface functional groups of carbon effectively promotes the reduction of NO with methanol. IR spectroscopic results of this study show that in the presence of O₂ nitric oxide is catalytically oxidized to nitrogen dioxide, which is chemisorbed on the surface of carbon. The surface nitrogen species were identified by FTIR spectroscopy.     

Selective catalytic reduction of NO with NH3 over CuOX-carbonaceous materials

CuO_X-carbon nanotubes (CNTs), CuO_X-activated carbon (AC) and CuO_X-graphite catalysts were prepared by wet impregnation method and their De-NO_X property were studied. SEM, EDX, TPD, TPR, AAS and XPS were employed to probe the effect of carbonaceous material supports and the nature of CuO_X species appeared on catalyst surface. The existence of Cu⁺, good dispersion and strong acid sites were found to contribute to the low temperature catalytic activity of CuO_X-CNTs with a NO removal efficiency of 67% at 250 °C. Moreover, the regeneration of deactivated CuO_X-CNTs catalyst caused by SO₂ could be achieved by 300 °C heating the catalyst in N₂.     

Ce-P-O催化剂用于氨选择催化还原消除氮氧化物

制备了可用于氨选择催化还原消除氮氧化物的Ce-P-O催化剂,通过X射线衍射、扫描电镜、N₂吸附、H₂程序升温还原和氨程序升温脱附等手段对催化剂进行了表征,并考察了催化剂的性能。结果表明,催化剂在空速20 000 h^-1表现出较高的氮氧化物消除活性,NO转化率>90%,在水蒸汽和SO₂存在条件下,催化剂具有较好的催化活性和稳定性。     

Adsorption and reaction of NO on activated carbon in the presence of oxygen and water vapour

A study of the adsorption and reaction of NO in the presence of oxygen and water vapour on an activated carbon obtained from oil palm shells is presented. The study is based on the measurement of breakthrough curves, at temperatures between 100 and 150 °C, and on the subsequent thermal desorption in a fix bed reactor. The concentration of the gas components, NO, O₂ and H₂O, corresponds to a simulation of a flue gas in a coal fired power plant. The experimental results show that the reactions on this system include the simultaneously adsorption, reduction and catalytic oxidation of NO together with the adsorption of created NO₂. During desorption NO₂ reacts to NO through a reductive desorption process. An acceleration of the NO oxidation occurs when the saturation level of the adsorbed NO is reached, resulting in a maximum on the breakthrough curve. Different adsorbed NO species are formed during the process: one thermal unstable NO, and three thermal stable NO species, NO₂, NO and (NO)₂ dimers, respectively.     

Wire-mesh honeycomb catalysts for selective catalytic reduction of NO with NH3

Both flat and corrugated wire mesh sheets were coated with aluminum powder by using electrophoretic deposition (EPD) method. Controlled thermal sintering of coated samples yielded uniform porous aluminum layer with a thickness of 100 μm that was attached firmly on the wire meshes. Subsequent controlled calcination formed a finite thickness of Al₂O₃ layer on the outer surface of each deposited aluminum particles, which resulted in the formation of Al₂O₃/Al double-layered composite particles that were attached firmly on the wire surface to form a certain thickness of porous layer. A rectangular-shaped wire-mesh honeycomb (WMH) module with triangular-shaped channels was manufactured by packing alternately the flat sheet and corrugated sheet of the Al₂O₃/Al-coated wire meshes. This WMH was further coated with V₂O₅-MoO₃-WO₃ catalyst by wash-coating method to be applied for the selective catalytic reduction (SCR) of NO with NH₃. With an optimized catalyst loading of 16 wt%, WMH catalyst module shows more than 90% NO conversion at 240 °C and almost complete NO conversion at temperatures higher than 300 °C at GHSV 5,000 h⁻¹. When compared with conventional ceramic honeycomb catalyst, WMH catalyst gives NO conversion higher by 20% due to reduced mass transfer resistance by the existence of three dimensional opening holes in WMH.     

NH3 selective catalytic reduction (SCR) of nitrogen oxides (NO x ) over activated sewage sludge char

The de-NO _x performance of sewage sludge chars activated physically using water vapor or chemically using KOH was evaluated. Characteristics of chars activated under different activation temperatures, water vapor concentrations, and KOH/char ratios were analyzed by N₂ adsorption-desorption and FT-IR. Chemically activated chars were more efficient in removing NO _x due to their higher surface area, oxygen functional group and NH₃ adsorption than physically activated chars. The de-NO _x performance of the activated chars is influenced more by chemical properties such as oxygen functional groups and NH₃ adsorption sites than by physical properties like specific surface area and pore volume.     

Low-temperature selective catalytic reduction of NO with NH3 based on MnOx-CeOx/ACFN

MnO _x -CeO _x /ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH3 at 80°C-150°C. The catalyst was characterized by N₂-BET, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The fraction of the mesopore and the oxygen functional groups on the surface of activated carbon fiber (ACF) increased after the treatment with nitric acid, which was favorable to improve the catalytic activities of MnO _x -CeO _x /ACFN. The experimental results show that the conversion of NO is nearly 100% in the range 100°C-150°C under the optimal preparation conditions of MnO _x -CeO _x /ACFN. In addition, the effects of a series of performance parameters, including initial NH₃ concentration, NO concentration and O₂ concentration, on the conversion of NO were studied. __________ Translated from Chemical Industry and Engineering Progress, 2007, 27(1): 87–91 [译自: 化工进展]     

Adsorption of gold-thiourea complex on activated carbon

The adsorption kinetics of the gold-thiourea complex on activated charcoal was studied. Experimental runs were made in a batch reactor at constant temperatures and stirred by a magnetic system. Samples were taken at different periods of time and were analyzed for gold in a Perkin-Elmer Model 360 atomic absorption spectrophotometer. The samples were prepared with synthetic solution of gold with thiourea, sulfuric acid, and iron sulfate with concentrations similar to the ones in the leaching process. The gold adsorbed on activated charcoal was 99% at 20°C. The adsorption behavior was characterized by the Freundlich model at different temperatures (20°C, 35°C and 50°C).     

Adsorption of benzoyl peroxide on activated carbon

The kinetics of adsorption of benzoyl peroxide from solutions in ethanol and n-hexane on coconut shell activated carbon was studied. It was found that the kinetics of adsorption of benzoyl peroxide is described by a pseudo-first-order rate equation. The adsorption isotherm of benzoyl peroxide at its equilibrium concentrations from 0.07 to 1.25 g/L in solution is adequately described by the Langmuir equation. It was established that, in a solution in ethyl alcohol, the degradation of benzoyl peroxide with the formation of ethyl benzoate occurred along with adsorption.     

Adsorption of ethyl benzoate on activated carbon

The kinetics of adsorption of ethyl benzoate from solutions in ethanol on coconut shell activated carbon was studied. It was found that the kinetics of adsorption of ethyl benzoate can be described by pseudofirst-order and pseudo-second-order rate equations with the same accuracy. It was established that the adsorption isotherm at a concentration to 2 g/L in the initial solution is adequately described by the Langmuir equation.     

Adsorption of gas mixture on activated carbon

Equilibrium adsorptions of H₂ and CH₄ from their mixture on three commercial activated carbons are measured by analyzing the breakthrough curves of the more strongly adsorbed CH₄ at 25 and 204°C and pressures up to 1000 psia. Three methods of predicting adsorption of mixture based on single-gas isotherms are used and compared with experimental data: ideal adsorbed solution theory, modified Polanyi-Dubinin potential theory and loading ratio correlation. None of the methods seems to have a distinct advantage over the others. However the loading ratio correlation is the only non-iterative method.     

MnOx-SnO2/TiO2型催化剂低温NH3选择性催化还原NO

采用分段负载的方式制备了MnOx-SnO2/TiO2型催化剂,并将其用于NH3选择性催化还原NO中,在280～600℃温度区间对该催化剂的脱硝活性进行了测试,同时也考察了催化剂的抗硫耐水性能。实验结果表明,该催化剂在130～250℃温度范围内NO的转化率接近100%,并且表现出较好的抗硫耐水性能。氮吸附-脱附、XRD和NH3-TPD等表征结果表明,较大的比表面积、无定形态的Mn、较强的酸性位以及Mn、Sn、Ti之间的强相互作用是该催化剂活性较高的主要原因。     

Adsorption characteristics of bamboo activated carbon

Dye is difficult to remove from aqueous solution with common adsorbents due to its large molecular size. Mesoporous bamboo activated carbon is utilized in the adsorption of Black 5, Red E and phenol. The adsorption performance of the carbon is experimentally examined along with the characterization of the adsorbent. The comparison of adsorption capacity of the bamboo activated carbon with that of coconut activated carbon and carbon cryogel indicates that the large volume of mesopore in the carbon helps the expansion of adsorption capacity. Microscopic observation, the measurement of pore characteristics and fitting to the adsorption isotherms are conducted in the characterization of the bamboo activated carbon.     

Adsorption and decomposition of NO on carbon and carbon-supported catalysts

The interactions of NO with carbon and carbon-supported catalysts have been investigated by means Fourier transform infrared spectroscopy. Nitric oxide direct decomposition over carbon-supported catalysts (Cu, Pt) was studied in a temperature ranging from 473 to 623 K. NO conversion increased with increasing reaction temperature in the whole temperature range. The carbon-supported Pt catalyst has a very high activity for the decomposition of NO in the absence of oxygen. As a result of NO chemisorption isocyanate (-NCO) species on the surface of carbon containing Cu were observed. When the reaction temperature was increased, the -NCO band at 2229 cm⁻¹ became more intense.     

Adsorption of cationic-anionic surfactant mixtures on activated carbon

This paper reported the adsorption of cationic-anionic surfactant mixtures, such as octyltriethylammonium bromide/sodium dodecylbenzenesulfonate (OTEAB/SDBS) and dodecylpyridinium chloride/sodium octanesulfonate (DPC/SOS), on activated carbon (AC) in deionized water and in mineralized water systems. The AC surface chemistry was characterized by X-ray photoelectron spectroscopy and ζ-potential determinations. It was observed that in deionized water solution, the addition of SOS obviously promoted the adsorption of DPC, while the existence of OTEAB increased the adsorption of SDBS first and then decreased that slightly with increasing SDBS concentration. In mineralized water solution, the addition of cationic (anionic) surfactants reduced the adsorption of anionic (cationic) surfactants. It was shown that the adsorption of the surfactants on the AC was predominated mainly by the hydrophobic interaction between AC surface and surfactants because of the low oxygen content and very low ζ-potential on the AC surface. There might exist synergism between cationic and anionic surfactants when adsorbing on AC in deionized water due to the electrostatic interaction between oppositely charged surface active ions. Such synergism might be greatly weakened when a large number of inorganic salts exist owing to the “screen” effect of the counter ions of the salt on the electrostatic attraction of oppositely charged surface active ions.     

Adsorption of VOC on modified activated carbon fiber

The surface chemistry of activated carbon fiber (ACF) was modified by CuSO₄. The static adsorption capacities of modified ACF for different volatile organic compounds (VOCs) were determined. The result indicates that ACF modified by CuSO₄ could get higher adsorption capacities for the vapors of benzene, toluene, methanol and ethanol than the untreated ACF. The increasing extent of the adsorption capacity of modified VACFs is different for various VOCs. The dynamic adsorption behavior of acetone vapor on modified ACF was also studied. The result confirms that the surface modification of ACF with CuSO₄ can enhance the affinity between ACF and acetone, which makes it possible to extract acetone of very low concentration from polluted air.     

Adsorption of 2,4-dichlorophenoxyacetic acid on activated carbon

The kinetics of adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) as a typical herbicide from aqueous solutions on coconut shell activated carbon was studied without preliminary treatment. The surface structure of the activated carbon, which is responsible for its properties, was characterized. The order of reaction in the process of adsorption was determined. The high adsorption capacity of the coconut shell activated carbon was shown.