Cobalt(II) schiff base functionalized mesoporous silica as an efficient and recyclable chemoselective acetalization catalyst

Cobalt(II) Schiff base functionalized mesoporous silica was synthesized from covalent attachment via the introduction of Co(OAc)₂ to salicylaldimine functionalized mesoporous silica. The catalyst proved to be chemoselective one for the acetalization of aldehydes to the corresponding acetals in alcohol. The immobilized catalyst can be easily recovered and reused for at least ten reaction cycles without significant loss of its catalytic activity.     

Highly ordered Zn-doped mesoporous silica: An efficient catalyst for transesterification reaction

Designing highly ordered material with nanoscale periodicity is of great significance in the field of solid state chemistry. Herein, we report the synthesis of highly ordered 2D-hexagonal mesoporous zinc-doped silica using a mixture of anionic and cationic surfactants under hydrothermal conditions. Powder XRD, N₂ sorption, TEM analysis revealed highly ordered 2D-hexagonal arrangements of the pores with very good surface area (762 m² g⁻¹) in this Zn-rich mesoporous material. Chemical analysis shows very high loading of zinc (ca. 12.0 wt%) in the material together with retention of hexagonal pore structure. Interestingly, high temperature calcination resulted into zinc silicate phase, unlike any ZnO phase, which otherwise is expected under heat treatments. High surface area together with Zn loading in this mesoporous material has been found useful for the catalytic activity of the materials in the acid-catalyzed transesterification reactions of various esters under mild liquid phase conditions.     

Dialkylaminopyridine-functionalized mesoporous silica nanosphere as an efficient and highly stable heterogeneous nucleophilic catalyst

A new nucleophilic catalytic system comprised of dialkylaminopyridine-functionalized mesoporous silica nanosphere (DMAP-MSN) has been synthesized and characterized. We have demonstrated that this material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability. We envision that this DMAP-functionalized mesoporous silica material can also serve as an effective heterogeneous catalyst for many other catalytic nucleophilic reactions.     

消化污泥负载稳定高效非均相光Fenton催化材料的制备及性能优化(英文)

近年来,随着我国经济飞速发展和城市人口快速增长,城市污水排放量不断增加,市政污泥产生量也随之增大.市政污泥含有大量有毒有害物质,如寄生虫卵、致病菌、有机污染物和重金属等,若不进行妥善处理处置将会对环境造成严重的二次污染.传统的污泥处理处置方法如卫生填埋、露天堆放和土地利用等已经无法满足日趋严格的污泥处理处置标准,研发新的污泥资源化利用方法具有重要的环境意义和经济价值.本课题组前期以铁盐为前驱体通过简单步骤制备了以市政污泥为载体,污泥中的重金属为可见光光敏剂,铁氧化物为活性中心的稳定高效非均相光Fenton催化剂.此催化剂在制备过程中虽然已经充分利用了市政污泥中的所有成分,但是其中部分可生化的有机大分子物质在制备过程中被直接燃烧或碳化,从而造成能源流失和浪费.为了更加充分利用市政污泥中的有机物,在制备稳定高效催化剂的同时尽可能多地回收能源和资源,本文在前期研究基础上进行了如下改进和优化:(1)采用市政污泥厌氧消化后的消化污泥为载体,通过厌氧消化手段将其中可生化的有机物转化为沼气,相对于直接用市政污泥制备催化剂,减少了能量流失,更具有经济效益和环境意义;(2)通过改变焙烧温度(250,350,450,550,650和750°C)、铁盐类型((NH4)_2Fe(SO_4)_2,FeSO_4,FeCl_3和Fe(NO_3)_3)和铁盐添加量(0,0.5,1.0,1.5,2.0和3.0 mol/L)对所制得催化材料的性能进行优化.利用红外光谱、X射线衍射、扫描电子显微镜和电感耦合等离子体质谱法等手段对所制备光Fenton反应催化剂结构进行了表征.结果表明,以消化污泥为原料制备的催化材料具有多孔和较高的比表面积,保证了在反应过程中催化剂与H2O2和被降解物质充分接触.样品中Fe含量较高,主要是以α-Fe2O3或无定形铁化合物形式存在,并通过Si–O–Fe键结合在污泥载体上,从而保证了催化剂较多的活性位点和较高的稳定性,因此所制材料可用作稳定高效的光Fenton反应催化剂.以偶氮染料罗丹明B为模式污染物评价了所制催化剂对污染物的降解效果.结果表明,在焙烧温度和铁盐添加量一定时,以亚铁盐(即(NH4)_2Fe(SO_4)_2和FeSO_4)为前驱体所制催化剂性能明显优于以铁盐(FeCl_3和Fe(NO_3)_3)为前驱体的催化剂;以(NH4)_2Fe(SO_4)_2为前驱体且其添加量为1 mol/L,焙烧温度为350 oC时所制FAS-1-350催化剂具有较高的降解速率(0.308±0.016 min.1)和较低的Fe~(2+)溶出率(0.94±0.24 mg/L).在紫外光照射下FAS-1-350重复使用6次,其催化性能没有明显降低,证实该样品结构稳定,可重复利用,具有良好的应用前景.     

Polymer‐supported macrocyclic Schiff base palladium complex as an efficient catalyst for the Heck reaction

A polymer‐supported macrocyclic Schiff base palladium complex has been synthesized. In the Heck reaction of aryl iodides and bromides with ethyl acrylate or styrene, the complex has been proved to give the corresponding products in good to excellent yields. The reaction proceeded smoothly in the presence of 0.5 mol% of catalyst in DMF within 1–4 h. Recycling studies have shown that the catalyst can be readily recovered and reused for four cycles with only a slightly decrease in its activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Ultrafast enzyme immobilization over large-pore nanoscale mesoporous silica particles

By finely tuning the TEOS/P123 molar ratio of the octane/water/P123/TEOS quadruple emulsion system and by controlling the synthesis conditions, an ultrafine emulsion system was isolated, under the confinement of which, nanoscale silica particles with ordered large mesopores (approximately 13 nm) have been successfully constructed; the obtained mesoporous silica particles have an unusual ultrafast enzyme adsorption speed and the amount of enzyme that can be immobilized is larger than that of conventional mesoporous silica, which has potential applications in the fast separation of biomolecules.     

Preparation and characterisation of amorphous mesoporous aluminophosphate and metal aluminophosphate as an efficient heterogeneous catalyst for transesterification reaction

Preparation, characterisation of pure aluminophosphate and aluminophosphate modified with different transition metals (V, Fe, Co Ni & Cu) and their catalytic activity in mono/dibenzyl substituted malonates synthesis are explained. The materials were prepared by the coprecipitation method in the absence of any structure-directing species and characterized for their composition, crystalline nature, total surface acidity, specific surface area pore diameter and pore volume by different techniques. Catalytic activity of the materials was investigated in transesterification of diethylmalonate with benzyl alcohol in liquid phase. Pure aluminophosphate resulted only in benzyl ethylmalonate whereas the incorporation of transition metals favored the formation of both benzyl ethylmalonate and dibenzylmalonate. Catalytic activity parallels the surface acidity and mesoporosity of the catalysts. The effect of the molar ratio of reactants, amount of catalyst, and reaction time on the conversion of diethyl malonate and transester yield has been studied. The highest activity of iron aluminophosphate is attributed to its mesoporous nature with uniform pore size distribution, higher surface acidity and surface area. Further, the scope and generality of iron aluminophosphate as a catalyst in the transesterification was studied using various aliphatic, alicyclic and aromatic alcohols. The catalysts could be recycled by retaining most of its initial activity.     

Encapsulated ultrafine and highly dispersed molybdenum dioxide nanoparticles in hollow mesoporous silica spheres as an efficient epoxidation catalyst for alkenes

A facile post-synthetic strategy was developed to functionalize the preformed hollow mesoporous silica spheres by encapsulating the molybdenum dioxide (MoO₂) nanoparticles inside the interior cavity. Hollow mesoporous silica spheres were prepared and employed as carriers, and the encapsulation of MoO₂ nanoparticles was achieved through a one-pot hydrothermal protocol. After characterization, the encapsulated MoO₂ nanoparticles were certified to be ultrafine and highly dispersed, which greatly promoted the catalytic activity. The as-prepared catalysts were utilized in epoxidation of alkenes and exhibited as a promising catalyst in this reaction. After reacting for 10 h, the optimal catalyst MoO₂@SiO₂-1 achieved a conversion above 95% and selectivity above 95%, respectively. Moreover, the catalysts also exhibited good reusability, conversion of 78% and selectivity of 89% (reaction time 4 h) were still obtained after recycling for 5 times. Meanwhile, the employed facial and efficient hydrothermal approach could be expanded to other molybdenum modified heterogeneous catalysts in various applications.     

Highly ordered aluminium-planted mesoporous silica as active catalyst for Biginelli reaction and formyl C-H insertion reaction with diazoester

Al-planted MCM-41s (Al-M41s) with regular mesoporous structure and Si/Al ratio of 23-32 were successfully prepared by the template-ion exchange method in which the template/Si molar ratio and Si/Al ratio were adjusted at 1.44 and 5-15, and showed much higher catalytic activity for the titled reactions than the other types of Al-M41s prepared by post-synthesis or sol-gel methods.     

An iron Schiff base complex loaded mesoporous silica nanoreactor as a catalyst for the synthesis of pyrazine-based heterocycles

An iron Schiff base complex was encapsulated in SBA-15 mesoporous silica to afford a Fe(III)-Schiff base/SBA-15 heterogeneous nanocatalyst for the synthesis of pyridopyrazine and quinoxaline heterocycles. These reactions proceeded in water with excellent yields. The catalyst was characterized by physico-chemical and spectroscopic methods and found to retain the characteristic channel structures of the SBA-15, allowing good accessibility of the encapsulated metal complex.     

Synthesis and characterization of large-pore vinyl-functionalized mesoporous silica SBA-15

Ordered mesoporous silicas SBA-15 with high loadings of pendant vinyl groups have been synthesized via co-condensation of tetraethoxysilane (TEOS) and triethoxyvinylsilane (TEVS) templated with a triblock copolymer.     

Zeolite an efficient catalyst for the Biginelli condensation reaction

A zeolite catalyzed, single step and environmentally friendly process for synthesis of classical Biginelli reaction was investigated. For this reaction Transition metal/Y zeolites were prepared by microwave solid-state and aqueous solution ion-exchange methods. The yield of reactions was increased in order of CuY > CoY > NiY > MnY ≈ FeY > VY > CrY > ZnY for the solid-state zeolite ion-exchange and CuY > CoY > NiY > MnY > CrY > VY > ZnY > FeY for the aqueous solution ion-exchange. The solid-state ion-exchange zeolite by microwave irradiation showed higher activity compared to the aqueous solution exchange. The yield of the product in the present of CuY zeolite was in order of 22–50%.     

Investigation of DNA as a catalyst for Henry reaction in water

Double-stranded DNA of natural origin can be used to facilitate nitro-aldol (or Henry) reaction in aqueous solution.     

Ordered mesoporous carbon as an efficient heterogeneous catalyst to activate peroxydisulfate for degradation of sulfadiazine

Catalytic potential of carbon nanomaterials in peroxydisulfate（PDS） advanced oxidation systems for degradation of antibiotics remains poorly understood. This study revealed ordered mesoporous carbon（type CMK） acted as a superior catalyst for heterogeneous degradation of sulfadiazine（SDZ） in PDS system, with a first-order reaction kinetic constant（k） and total organic carbon（TOC） mineralization efficiency of 0.06 min^–1 and 59.67% ± 3.4% within 60 min, respectively. CMK catalyzed PDS sy...     

Ordered mesoporous carbon as an efficient heterogeneous catalyst to activate peroxydisulfate for degradation of sulfadiazine

Catalytic potential of carbon nanomaterials in peroxydisulfate（PDS） advanced oxidation systems for degradation of antibiotics remains poorly understood. This study revealed ordered mesoporous carbon（type CMK） acted as a superior catalyst for heterogeneous degradation of sulfadiazine（SDZ） in PDS system, with a first-order reaction kinetic constant（k） and total organic carbon（TOC） mineralization efficiency of 0.06 min^–1 and 59.67% ± 3.4% within 60 min, respectively. CMK catalyzed PDS sy...     

Selenonium ionic liquid as efficient catalyst for the Baylis-Hillman reaction

The new acidic ionic liquid phenyl butyl ethyl selenonium tetrafluoroborate, [pbeSe]BF₄, was successful used as a co-catalyst in the Baylis-Hillman reaction of aldehydes and electron-deficient alkenes. The Baylis-Hillman adducts were obtained in moderated to good yields and in relatively short reaction times under mild conditions.     

中孔分子筛负载的钴基催化剂F-T合成反应研究

以中孔分子筛HMS-2为载体,浸渍法制香钴质量分数为15.00%的钴基催化剂,F-T合成反应研究表明：载体焙烧时间对F-T合成反应性能影响不大;Co/HMS-2催化剂的F-T合成反应在运行141.00h达到483.00K后,在H2/CO摩尔比为2.00,压力2.00MPa,空速500.00h^-1反应条件下,CO转化率达到88.00%,烃选择性保持在98.00%左右,烃分布中C5^+含量可达85.00%左右,进一步运转了384.00h,CO转化率仅下降了9.00%,而烃选择性和烃分布几乎不变,说明Co/HMS-2催化剂F-T合成反应性能和稳定性优异。载体中孔结构在473.00K催化剂开始F-T合成反应24.00h后已经塌陷,随后催化剂结构趋于稳定。     

Sevelamer as an efficient and reusable heterogeneous catalyst for the Knoevenagel reaction in water

A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained in excellent yields. Several novel, related catalytic systems showed promising catalytic properties for aromatic and heterocyclic aldehydes. The Sevelamer catalyst can be recovered using simple filtration and reused numerous times（up to 15 times） in the aqueous Knoevenagel reaction without any significant lowering of activity.