Selective catalytic oxidation of NO over iron and manganese oxides supported on mesoporous silica

The selective catalytic oxidation （SCO） of NO was studied on a catalyst consisting of iron-manganese oxide supported on mesoporous silica （MPS） with different Mn/Fe ratios. Effects of the amount of manganese and iron, oxygen, and calcination temperature on NO conversion were also investigated. It was found that the Mn-Fe/MPS catalyst with a Mn/Fe molar ratio of 1 showed the highest activity at the calcination temperature of 400 °C. The results showed that over this catalyst, NO conversion reached 70% under the condition of 280 °C and a space velocity of 5000 h-1. SO2 and H2O had no adverse impact on the reaction activity when the SCO reaction temperature was above 240 °C. In addition, the SCO activity was suppressed gradually in the presence of SO2 and H2O below 240 °C, and such an effect was reversible after heating treatment.     

Adsorption characteristics of organosilica based mesoporous materials

Hybrid organosilica mesoporous materials with pores of ordered three-dimensional hexagonal structure were prepared by the hydrolysis and co-condensation of 1,2-bis(triethoxysilyl)ethane with various concentrations of a surfactant as structure directing agents. The materials had high pore volume of 1-1.5 mL/g and high surface area from 1057 to 1445 m(2)/g. Adsorption measurement and adsorption calorimetry revealed that the prepared materials exhibited high hydrophobicity and high affinity toward nonpolar organic vapor such as n-hexane. The dynamic adsorption properties of the materials for n-hexane in the presence of water vapor showed that these hybrid organosilica materials preferentially adsorbed n-hexane vapor and were stable in the presence of water compared to the siliceous MCM48.     

Adsorption of reactive dyes on titania-silica mesoporous materials

This paper presents a study on the adsorption of two basic dyes, methylene blue (MB) and rhodamine B (RhB), from aqueous solution onto mesoporous silica-titania materials. The effect of dye structure, adsorbent particle size, TiO(2) presence, and temperature on adsorption was investigated. Adsorption data obtained at different solution temperatures (25, 35, and 45 degrees C) revealed an irreversible adsorption that decreased with the increment of T. The presence of TiO(2) augmented the adsorption capacity (q(e)). This would be due to possible degradation of the dye molecule in contact with the TiO(2) particles in the adsorbent interior. The adsorption enthalpy was relatively high, indicating that interaction between the sorbent and the adsorbate molecules was not only physical but chemical. Both Langmuir and Freundlich isotherm equations were applied to the experimental data. The obtained parameters and correlation coefficients showed that the adsorption of the two reactive dyes (MB and RhB) on the adsorbent systems at the three work temperatures was best predicted by the Langmuir isotherm, but not in all cases. The kinetic adsorption data were processed by the application of two simplified kinetic models, first and second order, to investigate the adsorption mechanism. It was found that the adsorption kinetics of methylene blue and rhodamine B onto the mesoporous silica-titania materials surface under different operating conditions was best described by the first-order model.     

Adsorption of hydrocarbons on mesoporous SBA-15 and PHTS materials

Plugged hexagonal templated silica (PHTS) materials are synthesized using a high TEOS/EO(20)PO(70)EO(20) ratio in the SBA-15 synthesis. This generates internal microporous nanocapsules or plugs in part of the channels, which could be inferred from the two-step desorption branch. These materials exhibit a tunable amount of open and plugged pores and a very high micropore volume (up to 0.24 mL/g) and are more stable than the conventional micellar templated structures known so far. In this study the adsorption properties of PHTS are investigated and compared to those of its plug-free analogue SBA-15. For this purpose nitrogen, n-hexane, n-heptane, c-hexane, 3-methylpentane, 1-hexene, and water were adsorbed on SBA-15 and PHTSs with a different ratio of open and plugged mesopores. The adsorption of n-hexane, c-hexane, n-heptane, and 3-methylpentane on SBA-15 and PHTS-A demonstrated that the presence of the plugs had an effect on the uptake of adsorbate in the low relative pressure region, the position of the capillary condensation step, and the total adsorbed amount of adsorbate. The results showed that n-heptane and 3-methylpentane cannot access part of the micropore system of SBA-15 and PHTS-A. Adsorption of c-hexane and n-hexane on PHTS-A indicated that not only the kinetic diameter but also the shape of the molecule is an important factor for being able to be adsorbed into the micropores or past the plugs. Moreover, these two adsorbates were the most efficient in filling up the available pore volume. From the adsorption of n-hexane on PHTSs with a different ratio of open and plugged pores, it was concluded that the size of the plugs differed, which depends on the synthesis conditions. Water adsorption isotherms proved SBA-15 and PHTS-B to be more hydrophobic than PHTS-A. n-Hexane, 1-hexene, and toluene were adsorbed on SBA-15 and the PHTSs to investigate the influence of the polarity of the adsorbate. The isotherms showed higher uptakes for polar adsorbates on more hydrophobic materials and vice versa.     

介孔硅铝材料上合成水杨酸甲酯的研究

与传统合成水杨酸甲酯的工艺不同,采用碳酸二甲酯(DMC)作为酯化试剂与水杨酸反应制备了水杨酸甲酯.反应所使用的催化剂是一系列不同硅铝比的介孔L硅铝化合物.结果表明,碳酸二甲酯是一种很好的酯化试剂,所合成的介孔硅铝化合物对此酯化反应是高效的催化剂.SA转化率可以达到98.6%,MS选择性可以达到77.0%,并且还发现水杨...     

Adsorption of molecular hydrogen on ultrafine microporous/mesoporous materials

The comparative processing of H₂ adsorption isotherms obtained at 77 K is demonstrated to be applicable to the investigation of the microtexture of the ultrafine oxide materials MCM-41 and ZSM-5 and their mechanical mixtures. The H₂ sorption method allows the micropore volume to be determined correctly for mixed ultrafine microporous/mesoporous materials.     

Low-temperature catalytic adsorption of NO on activated carbon materials

The catalytic adsorption of NO on activated carbon materials provides an appropriated alternative for the control of low-concentration emissions of this air pollutant. The surface complexes formed upon NO adsorption at 30 degrees C were studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The effects of the addition of O2 and the presence of copper as a catalyst were studied. Copper assisted the oxygen transfer to the carbon matrix. For the Cu-impregnated carbon sample, the presence of O2 favored NO adsorption by increasing the breakthrough time, the adsorption capacity, and the formation of nitrogen and oxygen complexes of higher thermal stabilities, which mainly desorbed as NO and CO2.     

Formation of acetone cyclic triperoxide over titania-incorporated mesoporous materials

Acetone cyclic triperoxide (ACTP) was formed over titania-incorporated mesoporous material catalysts from a mixture of acetone and hydrogen peroxide under a mild and acid-free condition. Formation of ACTP was confirmed by single-crystal X-ray crystallography. The formation of ACTP could be observed in this study because of using the catalyst with a large amount of titania-incorporation at 23 wt.% and its large pore size. This revised version was published online in June 2006 with corrections to the Cover Date.     

Adsorption Energetics of NO and CO on Pt(111)

The adsorption energetics of NO and CO on Pt(111) are studied using an ab initio embedding theory. The Pt(111) surface is modeled as a three-layer, 28-atom cluster with the Pt atoms fixed at bulk lattice sites. Molecular NO is adsorbed at high symmetry sites on Pt(111), with the fcc threefold site energetically more favorable than the hcp threefold and bridge sites. The calculated adsorption energy at the fcc threefold site is 1.90 eV, with an N-surface distance of 1.23 Å. The NO molecular axis is perpendicular to the Pt(111) surface. Tilting the O atom away from the surface normal destablizes adsorbed NO at all adsorption sites considered. On-top Pt adsorption has been ruled out. The Pt(111) potential surface is very flat for CO adsorption, and the diffusion barriers from hcp to fcc sites are 0.03 eV and less than 0.06 eV across the bridge and the atop sites, respectively. Calculated adsorption energies are 1.67, 1.54, 1.51, and 1.60 eV at the fcc threefold, hcp threefold, bridge, and atop sites, respectively. Calculated C-surface distances are 1.24 Å at the fcc threefold site and 1.83 Å at the atop site. It is concluded that NO and CO adsorption energetics and geometries are different on Pt(111).     

含Cu复合氧化物对NO和CO吸附和活化的TPSR研究

利用MS－TPD法并结合XRD、化学分析等对催化剂进行了表征，探讨了K2NiF4结构La2-x(Sr，Th)xCuO4±λ系催化剂中三个典型样品LaSrCuO4、La2CuO4和La1.7Th0．3CuO4对NO、CO及CO＋NO等小分子的吸附性能和活化规律。结果表明：NO吸附量的大小与催化剂中氧空位含量有关，吸附强度和脱附峰种类与金属离子氧化态有关。CO在氧缺陷复合氧化物催化剂上的吸附是首先变为碳酸根，并在高温以CO2物种脱出．在NO和CO的共吸附过程中，有关NO的吸、脱性能与单独NO－TPD中NO的吸脱附规律相似，表明NO在NO＋CO共吸附的竞争吸附过程中，优先吸附起决定作用，而受CO的影响较小．NO的吸附是NO活化分解的必要条件．     

Hybrid organic-inorganic catalytic mesoporous materials with proton sponges as building blocks

Non-ordered organic-inorganic mesoporous hybrid materials with basic sites have been synthesized following a fluoride-catalysed sol-gel process at neutral pH and low temperatures that avoids the use of structural directing agents (SDAs). Proton sponges have been used as the organic builder of the hybrids, while the inorganic part corresponds to silica tetrahedra. The proton sponges are diamines that exhibit very high basicity and, after functionalization, have been introduced as part of the walls of the mesoporous silica by one-pot synthesis. Several hybrids with different organic loadings have been synthesized and characterized by gas adsorption, thermogravimetric and elemental analysis, solid state MAS-NMR and FTIR spectroscopy. These hybrids show high activity as base catalysts and can be recycled.     

负载Ru催化剂的CO吸附态的研究

本文运用原位FT-IR光谱系统研究了各种活化处理因素对负载Ru催化剂的CO吸附态的影响.发现2135±15(HF)和2075±5(MF)cm~(-1)IR谱峰产生于金属与载体接触的周边部位,反映了以多重态吸附的CO对称和反对称振动.金属载体间的相互作用的增强,HF和MF强度大幅度衰减.经纯O_2处理的催化剂,HF和MF峰位置没有发生变化,而峰强度随吸附时间的相对增长速率有很大的差异.对HF和MF作了归属,提出了6配位18电子紧壳层稳定结构的表面锚合的羟基氧桥或卤桥的多聚羰基化合物种CO吸附模式.     

Selective catalytic reduction of NO over metal oxides incorporated zeolites

Selective catalytic reduction (SCR) of nitric oxide in an oxygen-rich atmosphere with propylene as a reductant has been investigated over supported La-Co-oxide (mixed metal oxide) catalysts prepared by the modified citrate method. Loading on ZSM-5 support gave greatly enhanced activity in the reduction of NO at relatively low temperatures. This SCR activity could be ascribed to incorporation of the mixed metal oxide into ZSM-5 as an amorphous perovskite phase via preparation.     

负载Cu氧化铝纳米管合成及在NO+CH4反应中催化性能研究

采用过氧化氢调节反应条件,在水热体系中合成了新型的勃姆石纳米管,经520℃焙烧2h后,晶型由AlOOH转化为γ-Al2O3;采用XRD、氮吸附、TEM等对合成的纳米管进行表征.结果表明,合成的γ-Al2O3纳米管长约300nm,外径20nm,比表面积达到230m2/g以上.以此为载体,采用等体积浸渍法用Cu(NO3)2...     

Co—MgO催化剂上NO—程序升温表面反应和NO—CH4反应

ＮＯ，程序升温表面反应（ＴＰＳＲ），ＮＯ－ＣＨ４反应，Ｃｏ－ＭｇＯ     

Cu-incorporated mesoporous materials: Synthesis, characterization and catalytic activity in phenol hydroxylation

A series of novel Cu-incorporated mesoporous materials (CMMs) with molar ratios of Cu/Si ranging from 1/200 to 1/20 were synthesized by sol–gel method using glutaric acid as template. The materials were characterized by powder X-ray diffraction (XRD), N₂ adsorption, diffuse reflectance UV–vis spectroscopy and transmission electron microscopy (TEM). The results indicate that the CMMs have a three-dimensional (3D) worm-like mesoporous structure with a surface area between 600 and 800 m² g⁻¹ and the copper ions are incorporated into the matrix with octahedral environment. The catalytic activity of these CMMs in the phenol hydroxylation using H₂O₂ as oxidant is comparable to that of TS-1. Effects of Cu/Si molar ratio in the catalyst and the influence of various reaction parameters on the catalytic activity were investigated in detail and the optimized reaction condition was acquired.     

Adsorption of xylene isomers on ordered hexagonal mesoporous FDU-15 polymer and carbon materials

The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers. The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the feasibility of using the three isomers as adsorbates to extract pore information. This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec.     

Selective catalytic reduction of NO over supported silver catalysts--practical and mechanistic aspects

Selective catalytic reduction of NO by hydrocarbons (HC-SCR) is one of the promising technologies for removal of NO in exhausts containing excess oxygen, such as diesel and lean burn gasoline engines. Supported Ag catalysts, especially Ag/Al2O3, are thought to be the promising candidates for use in diesel exhausts, as confirmed by several reports on engine bench tests. The HC-SCR performance of supported Ag catalysts is very sensitive to the reaction conditions, especially the type of hydrocarbons and the addition of H2. The control of reaction conditions would be key for practical use. The current research of supported Ag catalysts is reviewed from the viewpoints of practical use and the reaction mechanism, i.e., the reaction scheme, the role of surface adsorbed species, and the structure of active Ag species.     

Direct synthesis and catalytic applications of ordered large pore aminopropyl-functionalized SBA-15 mesoporous materials

SBA-15 mesoporous silica has been functionalized with aminopropyl groups through a simple co-condensation approach of tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES) using amphiphilic block copolymers under acidic conditions. The organic-modified SBA-15 materials have hexagonal crystallographic order, pore diameter up to 60 A, and the content of aminopropyl groups up to 2.3 mmol g(-1). The influences of TEOS prehydrolysis period and APTES concentration on the crystallographic order, pore size, surface area, and pore volume were examined. TEOS prehydrolysis prior to the addition of APTES was found essential to obtain well-ordered mesoporous materials with amino functionality. The amount of APTES incorporated in the silica framework increased with the APTES concentration in the synthesis gel, while the ordering of the mesoporous structure gradually decreased. Analysis with TG, IR, and solid state NMR spectra demonstrated that the aminopropyl groups incorporated in SBA-15 were not decomposed during the preparation procedure and the surfactant P123 was fully removed through ethanol extraction. The modified SBA-15 was an excellent base catalyst in Knoevenagel and Michael addition reactions.