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.     

介孔分子筛Al-MCM-41接枝三甲基氯化锡的合成、表征及催化性能

将三甲基氯化锡与Al-MCM-41介孔分子筛在N2气气氛中135 ℃回流4.5 h,得到表面键合有机锡的分子筛(CH3)3Sn-O-MCM-41[(CH3)3SnM]。 采用电感耦合等离子体质谱（ICP-MS）、有机元素分析、红外光谱、N2吸附-脱附、热重分析（TG）、NH3程序升温脱附（NH3-TPD）、X射线多晶衍射（XRD）和透射电子显微镜等测试技术对样品的组成、结构和表面物理化学性质进行表征。 结果表明,有机锡接枝率可达14.44%;接枝前后分子筛的NH3-TPD表面酸量(NH3)由0.652 6 mmol/g增加至1.294 4 mmol/g。 接枝后分子筛的比表面积减小,孔容变大,孔径变小,仍保持六方介孔结构;接枝分子筛(CH3)3SnM用于催化合成乙酸异戊酯,当n(异戊醇)∶n（冰乙酸）=1.0∶1.0,w（催化剂）=5%,138 ℃,回流5 h,反应转化率为96%;催化剂重复使用5次,酯化转化率仍可达到86%。     

高骨架铝含量Al-MCM-41的合成

制备了不同Al含量的Al-MCM-41试样，其中Si/Al比值最小为3，即最高含铝量x~A~l=0.303。X射线粉末衍射(XRD)分析表明样品具有MCM-41的特征结构，氮气吸附研究表明，样品呈现Ⅳ型吸附等温线，具有孔径分布均一的中孔结构。文中还利用^2^7AlMASNMR研究了试样中Al的化学环境，结果表明，即使在高铝含量的情况下，样品中的铝原子仍以四配位结合在MCM-41的硅骨架上，未能检测出骨架外六配位铝的存在。文中还就Al含量对孔结构的影响以及Al-MCM-41形成机理作了讨论。     

中孔分子筛Al-MCM-41制备及催化合成二芳基乙烷

以硅酸钠为硅源、硫酸铝为铝源、CTAB为模板剂,采用水热法合成了负载型固体酸Al-MCM-41中孔分子筛催化剂,并通过X射线衍射（XRD）、热重差热分析（TG-DTA）、扫描电镜（SEM）和红外（IR）方法对其进行了表征,同时研究了该催化剂在二芳基乙烷合成反应中的催化性能。考察了各种反应因素的影响,确定其最佳合成条件为：原料苯乙烯与二甲苯质量之比为1∶7.5,催化剂用量为1 %(总投料质量百分比),反应时间为3 h,反应温度为140 ℃,产率可达87.1 %,比传统催化剂浓硫酸提高了17 %。研究结果表明,该催化剂是替代液体酸合成二芳基乙烷的理想固体酸催化剂。     

苯酚过氧化氢羟化反应催化剂的研究进展

邻苯二酚和对苯二酚均为重要的化工原料和中间体。以过氧化氢为氧化剂,由苯酚直接羟基化合成苯二酚具有反应条件温和、环境友好的特点,近年来受到各国研究者的重视。本文综述了苯酚过氧化氢直接羟基化合成苯二酚所用催化剂的研究进展,主要介绍了复合金属氧化物、杂多酸盐和分子筛等几类催化剂的制备、性能、特点和发展的方向。     

金属酸盐催化剂对苯酚羟基化反应的活性考察

苯酚羟基化联产邻苯二酚和对苯二酚是一条典型的绿色工艺路线.通过对多种金属酸铁酸盐进行筛选,得出以Fe(NO3)3.9H2O为铁源、Cu(CH3COO)2.H2O为铜源,以氨水为沉淀剂,采用共沉淀法制备的Fe-Cu复合金属酸盐催化剂具有最好的催化活性.结果表明,在水作溶剂,催化剂与苯酚的质量比为1∶100,苯酚初始浓度25%,反应温度65℃,苯酚与双氧水的摩尔比为2的条件下,采用Fe-Cu催化剂,苯酚单程转化率可达25%,苯二酚总选择性在90%左右.通过对铁酸盐催化剂的XRD、IR表征,可以看出,Fe-Cu催化剂具有独特的CuFe2O4尖晶石结构,因而具有不同于其它铁酸盐的衍射峰和吸收峰.另外,Fe-Cu催化剂制备简便、原料廉价易得,因此具有良好的工业应用前景.     

简便方法合成含铁石墨相氮化碳材料及其催化苯直接羟基化制苯酚（英文）

苯酚是一种重要的基本有机化工原料.全球近90%的苯酚都是经"三步异丙苯法"工艺合成而得,但是该工艺存在单程苯酚收率低(5%)、酸污染严重等不足.同时由于联产丙酮,苯酚的产量也受丙酮市场所制约.由苯经氧化或羟基化一步法合成苯酚是催化化学领域中一项极具挑战的课题.由于苯分子较难活化,而苯酚易于深度氧化,因此研发和设计具有高活性和高选择性的催化剂是该课题的研究核心.因具有诸多特殊的理化性质,石墨相氮化碳(g-C_3N_4)作为一种新型碳质材料近年来在光催化、热催化、燃料电池和气体吸附等领域展示出广阔的应用前景.g-C_3N_4的类石墨层基本单元为大π共轭的三均三嗪环,对苯分子具有良好的吸附和活化能力.目前,g-C_3N_4(尤其是具有高比表面的介孔材料)在苯Friedel-Crafts烷基化和酰基化反应、苯的CO2氧化等反应中均显示了良好的催化活性.尽管如此,由于缺乏合适的氧化活性中心,纯的g-C_3N_4对苯直接羟基化几乎无催化活性.本课题组曾将乙酰丙酮氧钒和氧化钒负载至介孔g-C_3N_4,发现该类催化剂在H2O2参与的苯直接羟基化反应中,苯转化率高达18%,而苯酚选择性大于95%.然而,此类介孔g-C_3N_4均采用硬模板法合成,制备周期长且需要HF溶液蚀刻氧化硅模板.另外,钒基组分在介孔g-C_3N_4表面也存在着部分溶脱现象.本文以FeCl_3和二氰二胺为前驱体,通过一步热解法直接合成了含铁的g-C_3N_4材料(Fe-g-C_3N_4).采用N2吸附-脱附、XRD、TG、FT-IR、UV-vis、XPS光谱和TEM对材料的理化性质进行表征.结果显示,Fe的原位引入能显著提高g-C_3N_4的比表面积和孔体积,且使其依然保持石墨相结构.同时,富N的g-C_3N_4材料能有效地锚定Fe离子,使其均匀地分散在载体表面.作为多相催化剂,Fe-g-C_3N_4在H_2O_2环境下对苯羟基化合成苯酚的反应表现出较高的催化活性.当反应温度为60°C,其苯酚收率最高可达17.5%,且回收使用多次催化剂活性表现稳定.与之前报道的含铁和负载氧化钒或乙酰丙酮氧钒的g-C_3N_4催化剂材料相比,Fe-g-C_3N_4催化剂制备工艺更加简便.     

Model-free kinetics analysis of decomposition of polypropylene over Al-MCM-41

Both thermal and catalytic decomposition of PP sample is studied to understand the effect of catalyst (Al-MCM-41) on the decomposition behaviour. Mesoporous catalyst (Al-MCM-41) is synthesized by sol–gel methods and characterized by X-ray diffraction (XRD) analysis and nitrogen adsorption study. The optimum catalyst composition is found to be around 18.5 wt%, where the reduction in maximum decomposition temperature is around 103 °C. The nonlinear Vyazovkin model-free technique is applied to evaluate the quantitative information on variation of E with for PP sample under both catalytic and noncatalytic nonisothermal conditions.

The constant pattern behaviour of the TG curves and the similar trend on variation of E with for both catalytic and noncatalytic decomposition of PP indicates similar mechanism involved during decomposition. The only effect of catalyst is observed in the form of reduction of the temperature and the activation energy. The literature reported data on such variation are compared with the results of the present study. Results show that Al-MCM-41 is superior to the ZSM-5 catalyst in terms of catalyst loading due to the existence of larger external macropore and mesopore surface in it.     

Synthesis and characterization of copper(II) complexes of sulfadiazine with amino acids: catalytic activity toward oxidation of phenol and catechol

New copper complexes of DL-methioninoylsulfadiazine (MTS) and L-cystinoylsulfadiazine (CYS) were prepared and characterized using elemental analysis, IR, electronic spectroscopy, EPR spectroscopy, and thermal analysis. The mode of binding indicates that copper binds to MTS through carbonyl oxygen with the amino group nitrogen while for Cu^II–CYS the copper binds through carbonyl oxygen and SH with removal of its proton. The proposed structures were supported by conformational analysis which showed predominance of the trans form of copper(II)-L-cystinoylsulfadiazine. The two complexes enhanced oxidation of phenol and catechol in the presence of H₂O₂ under mild conditions. The catalyst shows proficiency toward oxidation of phenol and catechol compared to the auto-catalytic oxidation. Cu^II–MTS exhibited higher catalytic activity than Cu^II–CYS. The phenol and catechol oxidation is inhibited by Kojic acid.     

Characterization of high-impact polystyrene by catalytic pyrolysis over Al-MCM-41: Study of the influence of the contact between polymer and catalyst

In this work, the particular behaviour of a commercial high-impact polystyrene (HIPS) during the catalytic pyrolysis over Al-MCM-41 has been studied. The results obtained in a thermobalance showed differences in the number and/or the relative importance of the reaction steps involved in the pyrolysis, depending on the polymer particle size, which can be related to the differences in the nature of the polymeric phase being decomposed in each stage. Moreover, the relative importance of each step is very dependent on the particle size, revealing differences in the distribution of the different copolymer domains (i.e., styrene and butadiene domains) when the different particle size samples are mixed with the catalyst. The type of contact of the pure PS and PB polymers has also been studied revealing that, contrary to other results in literature, the catalyst may have an important effect both on the PS and PB pyrolysis. The results obtained showed that catalytic pyrolysis of these polymers could be a powerful tool for providing a fast and simple method for the characterization of copolymers of styrene and butadiene units.     

偏硼酸钙改性al-mcm-41催化剂的表征及催化性能

al-mcm-41分子筛;偏硼酸钙;催化性能;乙氧基化     

介孔分子筛Al-MCM-41制备及催化合成二芳基乙烷

以硅酸钠为硅源、硫酸铝为铝源、CTAB为模板剂,采用水热法合成了骨架负载型固体酸Al-MCM-41介孔分子筛催化剂,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)和红外(IR)方法对其进行了表征,同时研究了该催化剂在二芳基乙烷合成反应中的催化性能. 考察了各种反应因素的影响,确定其最佳合成条件为:原料m(苯乙烯)∶m(二甲苯)=1∶7.5,催化剂用量为1%(总投料质量分数),反应时间为3 h,反应温度为140 ℃,产率可达87.1%,比传统催化剂浓硫酸提高了17%. 研究结果表明,该催化剂是替代液体酸合成二芳基乙烷的理想固体酸催化剂.     

Pd/MCM-41催化剂的制备及其光催化苯羟基化的研究

以酸化高岭土为原料,采用水热法在碱性介质中制得MCM-41分子筛.以此分子筛为载体制备了负载型Pd催化剂并对载体和催化剂进行了氮气吸附脱附、X射线粉末衍射和透射电镜等表征.研究其在光催化苯羟基化反应中的催化性能,考察了Pd的负载量、氧化剂的用量、不同光源及光照时间等反应条件对催化剂催化性能的影响,以及催化剂的回收重复利用率.结果表明以H_2O_2为氧化剂时,在汞灯照射下,Pd/MCM-41催化剂对苯羟基化反应表现出了良好的催化性能.     

Oxidative dehydrogenation of ethylbenzene to styrene with CO2 over Al-MCM-41-supported vanadia catalysts

Catalytic performance of Al-MCM-41-supported vanadia catalysts (V/Al-MCM-41) with different V loading was investigated for oxidative dehydrogenation of ethylbenzene to styrene (ST) with CO₂ (CO₂-ODEB). For comparison, pure silica MCM-41 was also used as support for vanadia catalyst. The catalysts were characterized by N₂ adsorption, X-ray diffraction (XRD) pyridine-Fourier-transform infrared spectroscopy, H₂-temperature-programmed reduction, thermogravimetric analysis (TGA), UV-Raman, and diffuse reflectance (DR) UV–vis spectroscopy. The results indicate that the catalytic behavior and the nature of V species depend strongly on the V loading and the support properties. Compared with the MCM-41-supported catalyst, the Al-MCM-41-supported vanadia catalyst exhibits much higher catalytic activity and stability along with a high ST selectivity (>98%). The superior catalytic performance of the present V/Al-MCM-41 catalyst can be attributed to the Al-MCM-41 support being more favorable for the high dispersion of V species and the stabilization of active V⁵⁺ species. Together with the characterization results of XRD, TGA, and DR UV–Vis spectroscopy, the deep reduction of V⁵⁺ into V³⁺ during CO₂-ODEB is the main reason for the deactivation of the supported vanadia catalyst, while the coke deposition has a less important impact on the catalyst stability.     

The effect of Pt nanoparticles distribution on the removal of cyanide by TiO2 coated Al-MCM-41 in blue light exposure

With an aim to enhance the photocatalytic activity, Pt loaded TiO₂–Al-MCM-41 catalysts with high surface area were synthesized by a multistep route. The waste of the rice processing, rice husk (RH), was used as the precursor for the extraction of silica. The diffuse reflectance and photoluminescence spectroscopy revealed the extension of the absorption edge in the visible region and exciton trapping nature of the dispersed platinum. The structural analysis was carried out by XRD, whereas X-ray photoelectron spectroscopy identified the chemical states of the components of the synthesized powders. The BET surface area measurements revealed the reduction in the surface area and pore volume with the increasing platinum loading. TEM micrographs showed the uniform distribution of TiO₂ and Pt nanoparticles at the surface of Al-MCM-41. The photocatalytic efficiency of the synthesized powders as photocatalysts was obtained for the removal of 100 ppm CN⁻ from aqueous solution in fluorescent blue light exposure. Compared to unsupported TiO₂, the Pt-loaded catalysts exhibited substantially high activity for the removal of CN⁻. A plausible mechanism for the removal of cyanide ions was proposed. The catalysts showed excellent stability and reproducibility in the successive use.     

奎宁-杂多酸杂化催化剂催化H2O2为氧源的苯羟基化反应

将奎宁与Keggin结构磷钼钒杂多酸结合制备出一种新颖的多相苯羟基化杂化催化剂, 采用傅里叶变换红外光谱、紫外-可见光谱、X射线衍射、扫描电镜、热重、N₂吸附-脱附和CHN元素分析等表征手段对催化剂进行了分析. 结果表明, 该催化剂是一种具有较高比表面积和孔体积的半无定形有机杂多酸盐. 在H₂O₂为氧源的苯羟基化反应中, 杂化催化剂引导了液-固两相催化体系, 表现出较高催化活性和重复使用稳定性. 催化剂中奎宁与杂多阴离子间的氢键和电子相互作用赋予了其高熔点和难溶性, 而高比表面积和因奎宁而改善的杂多阴离子的氧化还原性是其获得优异催化性能的主要原因. 这为多相苯羟基化反应提供了一种新的且制备便捷的基于多金属氧酸盐的高效催化剂.     

A facile green synthesis of silver nanoparticles: An investigation on catalytic hydroxylation studies for efficient conversion of aryl boronic acids to phenol

Ag nanoparticles (AgNPs) catalyst material is bio-synthesized and fully examined using various spectroscopy and microscopy techniques. Further this synthesized material is used for hydroxylation reaction, for this purpose we developed a simple and versatile bio-based method from aryl boronic acids to phenol. The reaction was studied in the presence of low cost ligand in a hydrated reaction medium without any hazardous organic solvents, as a result a finite amount of yield was achieved in short time (<15 min). The hydroxylation reaction is further carried out in a series of different arenes substituted samples with good amount of yields.     

Reaction of benzaldehyde with various aliphatic glycols in the presence of hydrophobic Al-MCM-41: A convenient synthesis of cyclic acetals

The reaction of benzaldehyde with aliphatic glycols was performed over Al-MCM-41 with various Si/Al ratios. The effects of various parameters like temperature, mole ratio, reaction time and catalyst amount on the formation of acetals were optimized. The mesoporous Al-MCM-41 (Si/Al ratio 36, 57, 81 and 108) were synthesized by hydrothermal method. The synthesized catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm (BET), thermo gravimetric-differential thermal analysis (TGA-DTA) and TEM techniques. The acidity of the catalysts was measured by pyridine adsorption followed by FT-IR analysis. TEM analysis showed that the honeycomb-like regular arrangement of hexagonal pores on the molecular sieves. The highly hydrophobic Al-MCM-41 (108) showed higher activity than the other Si/Al ratios. The activity of the catalysts showed the following order Al-MCM-41 (108) > Al-MCM-41 (81) > Al-MCM-41 (57) > Al-MCM-41 (36). The hydrophobicity and nucleophilicity of the glycols highly influences the conversion of benzaldehyde, it followed the order; hexylene glycol (HG) > propylene glycol (PG) > ethylene glycol (EG). The results showed that mole ratio of 1:3 (aldehyde:glycol) gave higher yield than the other mole ratios.     

Sustainable and efficient 2,3-dihydroquinazolin-4(1H)-ones production over heterogeneous and recyclable Al-MCM-41 supported dual imidazolium ionic liquids nanocomposites

A type of Al-MCM-41 supported dual imidazolium ionic liquids nanocomposites have been synthesized and efficiently used as catalysts in the one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-ones. It was shown that the highest efficiency was achieved in the condensation of a range of aldehydes and anthranilamide in the presence of the (2)Al-MCM-41@ILCeCl₄(0.5) solid catalyst under mild conditions. Hot filtration test confirmed that the reaction follows a heterogeneous pathway. Moreover, the catalyst was stable, very active, robust, and displayed good recyclability without significant loss of catalytic activity after five consecutive cycles during the process. Green reaction conditions, operational simplicity, feasibility, high to excellent yields, sustainability of the functionalized catalyst are the main highlights of the present protocol.     

烯烃对噻吩在介孔分子筛Al-MCM-41活性位物种上吸附脱硫机制的影响

采用后嫁接法制备了不同铝负载量的Al-MCM-41分子筛。运用XRD、N₂吸附-脱附、NH₃-TPD、Py-FTIR等方法对分子筛进行物性表征,利用固定床评价其对噻吩的吸附性能。通过将分子筛吸附噻吩能力与分子筛的酸性质及织构性质进行关联,考察烯烃存在对Al-MCM-41活性位物种吸附脱硫机制的影响。结果表明,铝物种的引入即产生了B酸中心,也同时产生了两种类型的L酸中心L₁和L₂。引入低含量铝物种利于形成B酸中心和L₁型酸中心,引入高含量铝物种利于形成L₂型酸中心。其中,L₂型酸中心对噻吩的吸附效果最佳。烯烃和噻吩在B酸中心发生竞争吸附和催化转化反应,且催化转化反应占主导地位。L₂酸中心的存在促进了B酸中心上的催化转化反应,其所生成的大分子硫化物取代噻吩吸附在分子筛酸活性中心上提高了Al-MCM-41分子筛的饱和吸附硫容量。