微乳法制备纳米TiO2 /SiO2的结构及光催化研究

Nanosized TiO₂ and TiO₂/SiO₂ particles were prepared by hydrolysis of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS) in the TX-100 reverse microemulsion. These particles were characterized by TG-DSC, XRD, FTIR, TEM，N₂ adsorption-desorption. Their photocatalytic activity was tested by degradation of methyl orange. The result shows that TiO₂/SiO₂ nanoparticles are with a monodispersed spherical phase and a uniform size distribution，and TiO₂ particles are dispersed on the surface of SiO₂. The band for Ti-O-Si vibration in FTIR was observed, the Ti-O-Si bond increased the stability of anatase TiO₂, suppressed the phase transformation of titania from anatase to rutile. And due to the addition of SiO₂, the average size of titania decreased from 38 nm in pure TiO₂ to 5 nm in TiO₂/SiO₂. It was found, under UV light irradiation, TiO₂/SiO₂ particles showed higher activity than pure TiO₂, and TiO₂/SiO₂(1/1) particles showed the highest photocatalytic activity on the photocatalytic decomposition of methyl orange, which was influenced by crystal structure, particle size, crystallinity and Surface area Characteristics.     

Fe3O4@SiO2@mTiO2介孔多功能纳米复合颗粒的制备及载药能力

以溶剂热法制备氨基功能化的Fe₃O₄纳米颗粒为磁核,结合溶胶-凝胶法和模板法在其表面先后包覆上致密的SiO₂层和介孔TiO₂层,制备了磁性-发光-微波热转换性-介孔结构为一体的多功能核-壳结构纳米复合颗粒,并对其结构、性能及载药能力进行了研究。XRD分析表明:Fe₃O₄表面包覆上了无定形结构的SiO₂和TiO₂。TEM照片表明:所得的纳米复合颗粒具有明显的核壳结构和完美的球形,构成核的Fe₃O₄颗粒的尺寸在40~50 nm之间,Fe₃O₄@SiO₂@mTiO₂核壳结构纳米复合颗粒的尺寸为60~70 nm,壳层厚度约10 nm,并可观察到壳层中清晰的孔状结构。磁性、荧光光谱和微波热转换特性分析表明:该复合颗粒同时具有良好的发光性、磁性和微波热转换特性。N₂气吸附及药物负载率分析表明,该复合颗粒具有较高的比表面积(640 m²·g^-1)和介孔结构(孔径约2.8 nm)并且具有较高的药物负载率。     

CO2在纳米SiO2/TiO2悬浮体系中的光催化还原

用水热法合成了氧化硅改性的具有高比表面积、高催化活性的锐钛型二氧化钛, 并在其悬浮体系中将CO₂光催化还原合成甲醇. 采用XRD, TEM, 物理吸附, UV-Vis吸收光谱和FTIR等表征手段对催化剂结构特征进行了研究. 结果表明: 添加氧化硅后, 氧化硅和二氧化钛之间形成Si—O—Ti键, 抑制了TiO₂晶粒生长, 提高了锐钛型TiO₂的比表面积, 且随着含硅量的增加, SiO₂/TiO₂的UV吸收逐步蓝移, 禁带宽度增加. 还原反应结果表明: SiO₂/TiO₂具有光催化还原活性, 且随着含硅量的增加先增加后减小, 当SiO₂质量分数为3.5%时, SiO₂/TiO₂复合催化剂反应活性最强, 5 h内甲醇产量可达到21.0 mg/L, 并有少量甲醛生成.     

CO2在纳米SiO2/TiO2悬浮体系中的光催化还原

用水热法合成了氧化硅改性的具有高比表面积、高催化活性的锐钛型二氧化钛, 并在其悬浮体系中将CO₂光催化还原合成甲醇. 采用XRD, TEM, 物理吸附, UV-Vis吸收光谱和FTIR等表征手段对催化剂结构特征进行了研究. 结果表明: 添加氧化硅后, 氧化硅和二氧化钛之间形成Si—O—Ti键, 抑制了TiO₂晶粒生长, 提高了锐钛型TiO₂的比表面积, 且随着含硅量的增加, SiO₂/TiO₂的UV吸收逐步蓝移, 禁带宽度增加. 还原反应结果表明: SiO₂/TiO₂具有光催化还原活性, 且随着含硅量的增加先增加后减小, 当SiO₂质量分数为3.5%时, SiO₂/TiO₂复合催化剂反应活性最强, 5 h内甲醇产量可达到21.0 mg/L, 并有少量甲醛生成.     

热扩散法制备MoO3/SiO2催化草酸二甲酯和苯酚酯交换反应

采用热扩散法（TS）和等体积浸渍法制备了MoO₃/SiO₂催化剂用于草酸二甲酯和苯酚酯交换反应.结果表明,热扩散法制备的10%MoO₃/SiO₂-TS催化剂较等体积浸渍法制备的10%MoO₃/SiO₂-C催化剂具有更好的催化性能.运用X射线衍射、Raman光谱、X射线光电子能谱分析、吡啶吸附红外光谱、NH₃程序升温脱附等手段对催化剂进行了表征,发现虽然两种方法制备的催化剂都只有弱Lewis酸中心,钼均以氧化钼单体形式存在,未形成解离和聚合,但是10%MoO₃/SiO₂-TS催化剂较10%MoO₃/SiO₂-C催化剂表面钼含量更高且MoO₃分散得更好.在苯酚用量为0.2mol,10%MoO₃/SiO₂-TS催化剂用量为1.2g,反应温度为180℃,草酸二甲酯与苯酚的摩尔比为2,反应时间为4h的优化条件下,苯酚转化率可达70.9%,甲基苯基草酸酯和草酸二苯酯的收率分别达63.1%和7.7%.     

TiO2 / SiO2核 / 壳结构复合粒子的组装及其电化学性能

TiO₂ coated SiO₂ materials as anode for lithium-ion batteries were synthesized via an in situ hydrolysis of tetraethyl orthosilicate under ultrasonic irradiation using nanometer-sized TiO₂ colloids as precursors. The XRD patterns indicate that the as-prepared core/shell particles remain anatase after calcining below 800 ℃. TEM observation shows that the particle size of TiO₂ / SiO₂ composites is ca. 200 nm, and a homogeneous SiO₂ layer is coated on the surfaces of TiO₂ particles. FTIR spectra demonstrate that SiO₂ could have been coated on the surfaces of TiO₂ particles via a chemical bonding. In addition, the first specific charge and discharge capacities of the coated particle electrode were 66.4 mAh·g^-1 and 90.7 mAh·g^-1, respectively, which indicates that the TiO₂ / SiO₂ particles are more stable than the monodispersed TiO₂. Meanwhile, the new material has good lithium intercalation-deintercalation performances.     

Ag@SiO2纳米颗粒的制备及其在H2O2检测上的应用

利用柠檬酸三钠还原硝酸银制备了银纳米颗粒(AgNPs), 然后通过氨水水解正硅酸乙酯(TEOS)的方法, 在AgNPs上沉积SiO₂, 制备出以Ag为核, SiO₂为壳的复合纳米颗粒(Ag@SiO₂). 调节TEOS用量, 可以控制SiO₂层的厚度. 根据AgNPs的局域表面等离激元共振(LSPR)效应, 将制得的Ag@SiO₂颗粒用于H₂O₂的检测, 检测下限为1 μmol/L, 并可以通过控制SiO₂层的厚度方便地调节Ag@SiO₂颗粒与H₂O₂反应的速率. 与传统方法相比, 具有简单、快速、成本低的优点. 分别运用TEM、紫外-可见分光光度计对反应前后Ag@SiO₂颗粒形貌及反应过程中其LSPR吸收的变化进行了表征.     

气相燃烧合成纳米复合粒子的形态与结构

在气相燃烧反应器中成功地合成了TiO₂-SiO₂、TiO₂-SnO₂复合粒子。TiO₂-SiO₂复合粒子中TiO₂以金红石型和锐钛型存在，SiO₂以无定型的形式存在。复合结构为SiO₂附着于TiO₂的外部，在Ti∶Si的进料比较大时SiO₂附着于TiO₂的表面，Ti∶Si比值减小到1∶4时，SiO₂包覆全部TiO₂表面。包覆层的厚度大约为6～7nm。TiO₂-SnO₂的复合粒子中同时存在着三种晶体结构SnO₂、金红石型和锐钛型的TiO₂。在复合粒子的表面，TiO₂和SnO₂两种组分分布均匀。通过改变进料方式可以调整复合粒子的结构。     

Bi2S3/CdSe共修饰TiO2纳米管膜的构建及其光电化学阴极保护效应

为获得良好光电化学性能的TiO₂半导体复合膜,采用Bi₂S₃和CdSe对TiO₂纳米管膜进行共修饰。以阳极氧化法在Ti表面先制备TiO₂纳米管膜,再通过恒电流电沉积和连续离子层吸附反应在纳米管表面依次沉积CdSe和Bi₂S₃,构建了具有级联能带结构的Bi₂S₃/CdSe共修饰的TiO₂纳米管复合膜。结果表明,Bi₂S₃/CdSe/TiO₂纳米管复合膜对可见光吸收显著增强,光电化学性能大幅度提高。白光照射下,复合膜的光电流密度为670 μA·cm^-2,达到了纯TiO₂纳米管膜的17.6倍。Bi₂S₃/CdSe/TiO₂复合膜作为光阳极可使0.5 mol·L^-1 NaCl溶液中的403不锈钢的电位相对于腐蚀电位下降690 mV,显示出良好的光电化学阴极保护效应。     

SiO2/Co3O4核壳催化剂对AP热分解的催化性能研究

采用改良的Stöber法制备粒径约为200 nm的单分散球形SiO₂颗粒,以此为内核,分别通过液相沉淀法和尿素均匀沉淀法制备包覆形式不同的新型SiO₂/Co₃O₄核壳式纳米催化剂。采用X-射线衍射分析(XRD)、透射电子显微镜(TEM)、红外光谱分析(IR)、拉曼光谱分析(Raman)、BET比表面积测试等手段对产物进行表征,利用差式扫描量热仪(DSC)考察SiO₂/Co₃O₄复合物对高氯酸铵(AP)热分解反应的催化作用,探讨不同包覆形式对其催化活性的影响。结果表明,两种方法制备得到的SiO₂/Co₃O₄复合物分别为层包覆和粒子包覆,比表面积大,具有明显的核壳结构,且粒子包覆形式的SiO₂/Co₃O₄对AP热分解反应的催化效果最好,使AP的高温分解温度降低了110 ℃,放热量增加了662 J·g^-1。     

表面修饰多壁碳纳米管负载二氧化钛的制备及催化碳酸二甲酯与苯酚酯交换反应的性能

制备了表面修饰多壁碳纳米管负载TiO₂的催化剂,并将其应用于碳酸二甲酯与苯酚的酯交换反应. 采用X射线电子能谱、透射电子显微镜、低温N₂吸附-脱附和X射线衍射等对催化剂进行了表征. 结果表明,以低浓度的氨水（0.4%）代替去离子水作为沉淀剂时,制备的催化剂显示出更好的催化活性、分离性与重复使用性. 考察了TiO₂负载量、催化剂用量及反应时间对反应性能的影响. 在最佳反应条件下,苯酚转化率为42.5%,碳酸甲苯酯与碳酸二苯酯的总选择性达到99.9%以上. 经过4次重复使用后,催化剂的活性略有下降.     

The role of RGO in TiO<Subscript>2</Subscript>–RGO composites for the transesterification of dimethyl carbonate with phenol to diphenyl carbonate

TiO₂–RGO composites were prepared and used as efficient heterogeneous catalysts for the transesterification of dimethyl carbonate with phenol. Transmission electron microscopy images demonstrated that the RGO could remarkablely improve the dispersion of TiO₂. X‐ray photoelectron spectroscopy showed that RGO could change the chemical states of Ti species. Py-IR and Py-TPD results indicated the addition of RGO led to the increase of medium Lewis acid sites of TiO₂, which are positive for the transesterification reaction. The TiO₂–RGO composite with 50 wt% RGO exhibited a remarkable catalytic performance for the transesterification of dimethyl carbonate with phenol to diphenyl carbonate. Under the optimized conditions, the 53.5% phenol conversion and 99.9% transesterification selectivity were achieved. This phonel conversion of 53.5% could be compared with the result of homogeneous catalysts. RGO has been an excellent structural and electronic promoter in TiO₂–RGO composites.     

Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts

The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO₄ (Al/P=1), Al₂O₃ and AlPO₄-Al₂O₃ (5–25 wt.% Al₂O₃) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.     

超临界流体干燥法制备纳米TiO2-SnO2-SiO2复合光催化剂及其光催化性能研究

半导体多相光催化法作为一种污染治理新技术越来越受到人们的重视,在所使用的半导体光催化剂中,TiO2以无毒,催化活性高,价廉,无污染等特点,成为最具有前途的绿色环保型催化剂之一[1],但其自身具有局限性,如禁带宽度大,需在近紫外光下才能激发产生电子空穴对,对太阳光的利用率仅     

Effect of Mo content in MoO3/g-Al2O3 on the catalytic activity for transesterification of dimethyl oxalate with phenol

The influence of molybdenum content on the catalytic performance in the transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was investigated. The results indicated that the MoO₃/Al₂O₃ catalyst with 14 wt% Mo content gave maximal DPO yield with 6.1% and 75.1% DMO conversion. The component, structure and phase of MoO₃/Al₂O₃ catalysts were characterized by means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH₃-TPD), and FTIR analysis of adsorbed pyridine. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dimethyl carbonate synthesis catalyzed by DABCO-derived basic ionic liquids via transesterification of ethylene carbonate with methanol

Easily prepared DABCO-derived (1,4-diazobicyclo[2.2.2]octane) basic ionic liquids were developed for an efficient synthesis of dimethyl carbonate (DMC) via the transesterification of ethylene carbonate (EC) with methanol. 1-Butyl-4-azo-1-azoniabicyclo[2.2.2]octane hydroxide ([C₄DABCO]OH) exhibited high catalytic activity and 81% DMC yield together with 90% EC conversion was obtained under mild reaction conditions. Notably, the catalyst could be recycled for four times without loss of catalytic activity. Moreover, a possible mechanism was also discussed.     

Heterogeneous synthesis of glycerol carbonate from glycerol and dimethyl carbonate catalyzed by LiCl/CaO

In this article, a CaO-based catalyst was prepared by impregnating chloride salts on CaO to develop a highly efficient heterogeneous catalyst for the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate. LiCl/CaO exhibited a high catalytic activity under moderate reaction conditions. The effects of the LiCl loadings, the amount of catalyst and the calcination temperature on the catalytic activity were investigated. The highest yield of 94.19% glycerol carbonate was obtained at 65 °C on CaO loaded with 10% LiCl after 1 h, and the catalyst had high stability in reusing work. Scanning electron microscopy (SEM), X-ray diffraction (XRD), BET, CO₂-TPD, XPS and thermalgravity (TG) were used to characterize the prepared catalyst. It was found that the high catalytic activity of CaO after modification with LiCl is associated with the structural aspects and the amount of basicity of the catalyst. The Li₂O₂ species, which is a strong basic site that is formed by the substitution of the Ca²⁺ in CaO lattice by Li⁺, has great activity for transesterification.     

乙酰丙酮氧钛催化苯酚和碳酸二甲酯的酯交换反应

首次将乙酰丙酮氧钛用于苯酚和碳酸二甲酯的酯交换反应合成碳酸二苯酯,显示出较好的催化活性和很高的酯交换选择性,催化剂经180℃热处理后,苯酚转化率可达45.8%,转化数(n(苯酚)/n(Ti))为96,高于有机钛类均相催化剂.结果表明,当乙酰丙酮氧钛用量为0.2g以上,开始有副产物苯甲醚生成,酯交换选择性随催化剂用量的增加而降低.该催化剂重复使用5次后,苯酚转化率仍可达40%以上,酯交换选择性为99.9%,表现出较高的重复使用性能.     

SiO2负载氮掺杂TiO2可见光响应光催化剂的制备及性能

以四氯化钛为钛源,尿素为氮源,采用液相水解-沉淀法制得SiO2负载N掺杂TiO2可见光响应TiO2-xNy/SiO2光催化剂(TSN)。以苯酚为模型物,考察了TSN在可见光区、紫外光区及太阳光下的光催化活性,以及催化剂的使用寿命、分离性能。采用XPS、FTIR、UV-Vis DRS、XRD、TEM和低温氮物理吸附等对催化剂的结构进行表征。结果表明,N以阴离子形式进入TiO2体相并置换晶格中的O,适量N掺杂的TSN在紫外光区、可见光区及太阳光下均表现出较高的活性。SiO2与TiO2界面间有Ti-O-Si键形成,结合牢固。N掺杂在TiO2表面生成Ti-O-N键,形成新的能级结构,使催化剂的吸收红移至450~500 nm,诱发TiO2可见光催化活性。SiO2负载可减小TiO2颗粒平均尺寸,增加催化剂比表面积;同时SiO2负载还可改善催化剂的分离性能,提高催化剂使用寿命。