Catalytic Reduction of Nitric Oxide on SiO2/AlO3-supported Transition Metal Catalysts

Selective reduction of nitric oxide in pressence of oxygen is one of the major challenges in the automobile exhaust after-treatment for lean-bum gasoline engines and diesel engines. Besides Cu-ZSM-5, Pt and Pd based noble metal catalysts, alumina-supported silver catalysts show high activities on NOx conversion to nitrogen^[1,2]. However, NO conversion activities over silver on binary oxides have rarely been studied in detail^[3], although copper on SiO₂-Al₂O₃ catalyst was reported to have a high activity^[4] Here, NOx reduction activities on SiO₂-Al₂O₃-supported transition metal catalysts prepared by sol-gel method was investigated.     

MCM-41 Supported Rhenium Oxides:Characterization and Selective Methanol Oxidation

Re oxides have not widely been used as catalysts for selective oxidations owing to sublimation under pretreatment and reaction conditions^[1].Nevertheless, the property of Re species capable of adopting a variety of oxidation states that are illustrated in both binary and ternary oxides^[2,3],may provide rich and interesting chemistry. One of us reported a crystalline binary oxide compound SbRe₂O₆ for the selective methylal formation in the methanol oxidation^[4]. The selectivity reached 92.5% at a conversion of 6.5% at 573 K. The performance of SbRe₂O₆ was attributed to the Re-oxide octahedra connecting with Sb-O chains^[5]. However, the crystalline oxide SbRe₂O₆ has a very low surface area (1 m² g^-1),resulting in insufficient activity for the methylal production. Recently, we found the new catalytic property of supported Re oxides for the selective oxidation of methanol to methylal^[6]. Here, we report the characterization and catalytic property of MCM-41 supported Re oxides for the selective methanol oxidation.     

Synthesis,Structure and Mechanism of a Series of Novel Nanocrystalline Rare Earth Orthovanadate Catalysts for Oxidative Dehydrogenation of Light Alkanes at Low Temperatures

The oxidative dehydrogenation of light alkanes to light alkenes is one of the potentially important catalytic processes for the effective utilization of light alkanes. However, high temperatures were required to initiate the reactions on heterogeneous catalysts reported by other authors in the literature^[1,2]. In recent years we reported a series of novel nanocrystalline rare earth orthovanadates synthesized by the peroxyl and nitrate methods for oxidative dehydrogenation of propane at low temperatures^[3,4]. In this paper the synthesis of a series of novel nanocrystalline rare earth orthovanadates (LnVO₄, Ln=Y, La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) by the citrate method is reported, together with the structural characterization and excellent performances of the catalysts for oxidative dehydrogenation of light alkanes.     

Pre-reduced Activated Carbon-Supported Molybdenum-Based Catalysts for the Production of Mixed Alcohols from Synthesis Gas

Unsupported or supported Mo-based catalysts have been widely employed in petroleum industry, for hydrotreating^[1],and for the production of hydrocarbons^[2] and alcohols_[3] by hydrogenation of CO (or CO₂). Oxides, such as alumina, silica, silica-alumina, are commonly used as the supports for these purposes. Carbon-supported materials have been claimed to have potential advantages over oxide-supported ones, such as lower tendency of carbon deposition^[4], less dehydration and thus less secondary reactions. Here we present results on mixed alcohol synthesis over H₂-prereduced C-supported Mo-based catalysts.     

Effect of SO2 on the NO Oxidation over NiO/γAl2O3 Catalyst

NO is the dominant component of NO_x. It can be easily oxidized to NO₂ over active catalysts in the oxidizing exhaust gases. And then, the high reactive NO₂ can be removed completely further through adsorption or absorption approach. However, SO₂,another main contaminant in the exhaust, is well known to poison the oxidative catalysts. A strong deactivation for metal oxides supported on Al₂O₃ was found when catalysts had been exposed to the gas containing 500ppm SO₂. It was also reported that the inhibition effect of SO₂ was enhanced at low temperatures. But recently, some studies declare that the oxidation of propane can be promoted over Pt/γ-Al₂O₃ if a small amount of SO₂ (20 ppm) is present in the feed gas^[1]. Jang et al. have also found that SO₂ has a promoting effect for the oxidation of NO to NO₂ over CO₃O₄/γ-Al₂O₃ catalyst^[2]. These observations are meaningful because the existence of SO₂ in the oxidizing exhaust is often inevitable and the problem of catalyst deactivation by SO₂ has puzzled researchers for a long time.     

Novel VPO Catalysts for n-Butane Oxidation to Maleic Anhydride:The Effects of Combined Moderators,Preparation Procedure and MCM-41 Supports

VPO catalysts are widely used in selective oxidation of n-butane into maleic anhydride (MA)^[1-2]. In the recent years, there is an obvious trend worldwide that the selectivity of a target product is more emphasized than the overall conversion, to decrease the undesired by-products. In this study, different approaches have been tried to generate more environmentally friendly VPO catalysts, with high MA selectivity and improved n-butane conversion. The moderated catalyst was prepared in aqueous phase^[3]. For comparison, the moderators were also introduced by impregnating the VPO precursor synthesized in organic medium. The supported VPO systems on the MCM-41 mesopore materials were prepared by employing the reaction of V₂O₅ with isobutanol in the presence of MCM-41 fine powder with different Si/Al ratios. The catalysts were evaluated at 385-425℃ and characterized by XRD, XPS and TPR etc.     

Photopromoted Carbonylation of Olefins with Carbon Dioxide by Transition Metal Complexes Catalysis

The carbonylation of olefins is important and essential methods to synthesize organic compounds,Which requires high temperature (150-200℃) and high pressure (10~20MPa) in addition to precious metal complex catalysts (such as Ru,Rh, Ir)^[1], In recent years photopromoted organic syntheses have received more and more attentions that were called environmentally friendly technique because of their ambient reaction conditions,high reactivities and selectivities and a little pollution^[2]. Photopromoted carbonylation can be completed in ambient conditions and by non-precious complexes catalysts, and especially photopromoted methoxycarbonylation of olefins could give better results^[3,4]. In previous papers we have established that the methoxycarbonylation of olefins with carbon dioxide could be carried out in place of carbon monoxide.     

XPS Spectra of K-Ru/MWNTs Catalysts for Ammonia Synthesis

Alkali metal and alkali oxide-promoted ruthenium has been found to be one of the most active catalysts for ammonia synthesis under atmospheric pressure^[1]. Recently, We found^[2] that the K-Ru/MWNTs catalyst showed very high activity for ammonia synthesis. It is suggested that the high activity is due to the special electronic and structural properties of the carbon nanotubes. Alkali and alkali oxide doped MWNTs have been reported to be more favorable for electronic transfer and hydrogen storage^[3]. In the ammonia synthesis,these properties may play important roles. In this study, K-Ru/MWNTs and Ru/MWNTs were prepared and characterized by XPS. We found that alkali oxide can improve the Ru dispersion similar to the classic catalysts for ammonia synthesis.     

MCM-41 Supported Nickel Catalysts for Carbon Dioxide Reforming of Methane

There has been an increasing interest in the conversion of methane and carbon dioxide into synthesis gas^[1]. High performance Ni-based catalysts have attracted much attention^[2-4]. In this study, MCM-41 supported nickel were used as catalysts for carbon dioxide reforming of methane. It is found that the obtained catalyst exhibited high activity for getting syngas with its ratio of unity.In contrast to the performance of other nickel-based catalysts; Ni/MCM-41 has higher conversion and yield at lower temperature. The effects of nickel loading, particle size, GHSV, and calcination temperature on catalytic activities were also investigated.     

Ag/La0.6Sr0.4MnO3 Catalysts for Complete Oxidation of Alcohol Fueled Car Exhausts

Alcohol fuel has been suggested as an alternative for car operation to reduce gasoline consumption^[1]. However, being different from that of gasoline car, alcohol-fueled car exhaust principally contains unburned alcohol and formaldehyde/acetaldehyde^[2]. These volatile C₁/C₂ organics may have an undesirable impact on air quality. Most of the existing catalysts for complete oxidation of alcohol are precious metal catalysts supported by γ-Al₂O₃^[2,3].     

Synthesis of binaphthols over mesoporous molecular sieves

Mesoporous aluminosilicates (Al-containing NaMCM-41) were applied as catalyst supports for oxidative coupling of β-naphthol and substituted β-naphthols due to their remarkable features such as surface area, ordered mesopores and high thermal stability. The NaMCM-41 supported copper catalysts prepared by impregnation method, and Cu-NaMCM-41 was prepared by incorporating copper during synthesis. Oxidative coupling of β-naphthol reaction was studied using molecular oxygen as oxidant. The copper supported NaMCM-41 catalysts were prepared with different Si/Al ratios and calcined from 120 to 420 °C were observed to show varied product selectivity. The NaMCM-41 supported copper catalysts and Cu-NaMCM-41 were more active than the corresponding Cu/Fe supported on NaY zeolite. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), UV–DRS, ICPMS and BET surface area techniques and the reaction products were confirmed by ¹H-NMR, FTIR and HRMS. An attempt has been made to explain the product selectivity of the catalysts discussed with the above techniques. The high dispersion of Cu⁺² species observed in the catalysts having high Si/Al ratios in NaMCM-41 support and catalysts that are calcined at low temperatures, i.e. less than 420 °C, yielded an unexpected product perylene diol. A comparatively low dispersion of Cu⁺² species, noticed in catalysts having low Si/Al ratios and calcined at high temperatures, yielded binapthol as the coupled product. The effect of the variation of catalyst and the solvent are also studied.     

CO Oxidation Activity and Characterization of Ag-Mn、Ag-Ce and Ag-Cu Mixed Oxide Catalysts

Catalytic oxidation is an efficient way to convert CO to CO₂ at low temperature. Precious metal catalysts such as Ft and Pd have been demonstrated to be very effective^[1]. However, attention has also been given to base metals due to the limited availability of precious metals. As a single component base metal catalyst cannot rival a precious metal catalyst, improvement in its activity has been attempted by combining several elements^[2,3]. In the present work, we studied redox and structure of Ag-M(M=Mn、Ce and Cu) catalysts to gain some evidence of the synergism between Ag and base metals, and investigated their catalytic activities.     

Synthesis of Mesoporous Molecular Sieves via a Novel Templating Scheme

Since Mobil researchers reported the discovery of a new family of silica-based mesoporous molecular sieves (M41S) materials in 1992^[1,2], there has been a growing interest in using these materials as heterogeneous catalysts, catalyst supports, and nanocomposite host materials for novel applications. All these applications have stimulated many researchers to synthesize mesoporous materials via different templating schemes or synthesis pathways. So far, ionic and neutral surfactant including neutral alkylamine^[3], polyethlene oxide^[4], genimi^[5], and amphiphilic triblock copolymer^[6] have been the most commonly used as templates for the directing the formation of mesoporous.     

Electrodeposition Carbon Nitride Films from Organic Solutions

Since the theoretical predictions of the hypothetical β-C₃N₄ compound may have extraordinary physical and chemical properties^[1], A variety of deposition techniques have been developed to investigate the synthesis of the novel material. The synthesis of carbon nitride has become an area of intense interest in materials science and great progress has been made^[2]. However, the methods used to this task are all vapor deposition techniques or solid state preparation methods. Synthesis of crystalline β-C₃N₄ with chemical stoichiometry content of nitrogen is very difficult. The use of appropriately designed molecular and low enough synthesis temperatures to insure kinetic control of reaction products appears to be a promising direction.     

Synthesis of Silica Hollow Spheres with Diameter Around 50 nm by Anionic Surfactant

Silica hollow spheres(SHSs) have attracted great attention because of their low toxicity,low density,large surface area,high chemical and thermal stability,and surface permeability.They can be widely applied in storage[1],catalysis[2],drug delivery[3,4],low-dielectric-constant materials[5],low-refractive materials[6-8],and so on.Up to now,there have been various methods to produce SHSs.Inorganic[9] or organic particles[10],such as polystyrene or calcium carbonate,were used as hard templates to create hollow cavities.However,the multistep synthetic process and the lack of structural robustness of the shells upon template removal process weaken their application.Soft templates,including oil-in-water emulsions[1],[2],vesicles[13],micelle[14,15] and gas bubbles[16],are applied widely.     

一类受生物启发的双膦双硒镍配合物的合成及其电催化产氢性能

自然界中,[NiFeSe]氢化酶比[NiFe]氢化酶具有更高的催化产氢活性和特殊的耐氧性。其较高的催化活性机制被认为跟[NiFeSe]氢化酶上所取代的硒(Se)原子密切相关。因此,[NiFeSe]氢化酶的特殊结构、性质及催化机制强烈激发科学家们设计并合成各种模拟[NiFeSe]氢化酶活性中心的镍铁硒或镍硒配合物(也即受生物启发的模拟物)。本论文工作首先合成及结构表征了六个基于双硒配体与含二茂铁的双膦配体的镍硒配合物(2a–2c,3a–3b,4);然后将这些镍硒配合物用作[NiFeSe]氢化酶的功能模型物,利用电化学方法,以三氟乙酸为质子给体测定了相应的电催化产氢活性。在相同实验条件下,分别研究了双硒配体上不同的取代基团,及含二茂铁的双膦配体上不同取代基等结构修饰方式对镍硒配合物催化产氢性能的影响。结果表明:这些镍硒配合物的催化产氢活性跟双硒配体及双膦配体的结构有很大关系,对应的催化转化频率(TOF)分别为12182 s^?1(2a),15385 s^?1(2b),20359 s^?1(2c),106 s^?1(3a),794 s^?1(3b),13580 s^?1(4)。其中,1,2-二硒-4,5-二甲基和1,1’-双(二苯膦)二茂铁配体与镍离子配位形成的镍硒配合物2c具有最好的电催化活性(TOF=20359 s^?1),其产氢性能已大大超过先前我们课题组所报道的由1,2-苯二硒、1,1’-双(二苯膦)二茂铁所配位形成的镍硒配合物1(TOF=7838 s^?1)。     

Asymmetric Borohydride Reduction of Acetophenone Catalyzed by Chiral Salen-Co(Ⅱ) Complex Using Sodium Borohydride

Development of efficient catalytic asymmetric reactions is the most challenging task in current synthetic chemistry; much effort has been devoted to create the chiral metal complexes of asymmetric catalysis. In the last two decades' many brand-new ligands had been synthesized and their combination with various metal ions has been applied in asymmetric catalysis. However, most ligands have only narrow applications and their use is limited to some reactions. Exceptionally, a few ligands and their metal complexes such as binaphthol, semicollin,and binap show wide applicability. Chiral salen ligand is one of such ligands and their metal complexes are now used as the catalysts for a variety of asymmetric reactions such as epoxidation^[1], aziridination^[2], cyclopropanation^[3], Diels-Alder reaction^[4], asymmetric transfer hydrogenation of aromatic ketones^[5] and kinetic resolution of racemic epoxides^[6] and so on.     

Study on the Synthesis of Poly(p-Phenylene Vinylene) Derivatives by Dehydrochlorination

The synthesis of poly(p-phenylene vinylene) (PPV) and its derivatives have aroused great interest^[1],since Burroughes^[2] discovered that PPV showed excellent electroluminescent (EL) properties. The conventional polymerization reactions, such as dehydrochlorination reaction,Wittig reaction and et al, usually afforded insoluble and/or infusible PPV and its derivatives, which shows inferior mechanical properties. Though the precursor polymer route can circumvent the insolubility of PPV, the strategy needs muti-step reaction and high temperature which affords the low yield and other disadvantageous^[3]. So the synthesis of soluble PPV derivatives with high yield are very fascinating.     

Enantioselective Hydrogenation of Acetophenone over Cinchonidine-Stabilized and Supported Rhodium Clusters

Because of the importance of the chirality in chemicals in everyday, the synthesis of enantiomerically pure chiral compounds has become an important academic and commercial advantage. In asymmetric synthesis field, enantioselective catalysis has been the most challenging subject over the past decades. Among the numerous enantioselective heterogeneous catalysts, the rhodium is always an unsuccessful example under favorable reaction conditions with only 20%-30% enantiomeric excess (e.e.)^[1].And almost all of papers about heterogeneous enantioselective catalysis have reported that rhodium is not suitable for heterogeneous enantioselective hydrogenation^[1-3].     

A STUDY OF THE STABILIZING CAPACITY OF GLYCINE TOWARD SILVER CLUSTER Ag42+ IN AQUEOUS SOLUTION

本文用溴钨灯照射含异丙醇、甘氨酸(稳定剂)和硝酸银的水溶液制得非金属银团簇Ag₄²⁺(λmax=275nm),其产率随甘氨酸量的增加而增加,并且在空气中甘氨酸可以稳定其数天。对所得结果以及Ag₄²⁺在照相潜影形成过程中的可能作用进行了讨论。本文用溴钨灯照射含异丙醇、甘氨酸(稳定剂)和硝酸银的水溶液制得非金属银团簇Ag₄²⁺(λ_max=275nm),其产率随甘氨酸量的增加而增加,并且在空气中甘氨酸可以稳定其数天。对所得结果以及Ag₄²⁺在照相潜影形成过程中的可能作用进行了讨论。