Pt 改性的高结晶度 TiO2 晶须的光催化性能

 以二钛酸钾 (K₂Ti₂O₅) 为前驱体, 通过离子交换和 800^oC 焙烧制备了 TiO₂晶须 (TiO₂(800^oC)), 并采用乙二醇胶体法, 在 TiO₂(800^oC) 样品上负载 1% Pt 纳米颗粒制成了 Pt/TiO₂(800^oC 催化剂. 采用 X 射线衍射、扫描电镜、透射电镜、X 荧光光谱和低温 N2 吸附-脱附等技术对催化剂进行了表征, 并考察了该催化剂光催化降解苯酚活性及稳定性. 结果表明, TiO₂(800^oC)样品为结晶度较高的纯锐钛矿 TiO₂, 载 Pt 后催化活性提高到原来的 2.3 倍, 具有很高的单位比表面积活性. 催化剂经 10 次重复使用后, Pt 流失量仅为 6%, 活性为新鲜催化剂的 91%. 而低结晶度的纯锐钛矿或混晶的 TiO₂ 负载 Pt 催化剂的活性和稳定性均不及 Pt/TiO₂(800^oC).     

核壳结构TiO2@SiO2催化碳酸二甲酯与苯酚酯交换合成碳酸二苯酯

以反相微乳液法和沉淀法相结合制备了核壳结构TiO₂@SiO₂,首次用于碳酸二甲酯与苯酚酯交换合成碳酸二苯酯反应,显示较好的催化活性. 采用200 ℃焙烧的TiO₂@SiO₂,用量0.20 g,反应9 h,苯酚转化率达41.8%,酯交换选择性为100%. 透射电镜显示TiO₂@SiO₂核厚壳薄,TiO₂核直径220-300 nm,SiO₂壳厚度40-60 nm,具有介孔结构. TiO₂@SiO₂对碳酸二甲酯与苯酚酯交换反应有好的重复使用性,使用4次苯酚转化率仍保持在40%以上. TiO₂与SiO₂发生相互作用,Ti进入骨架形成Ti-O-Si键,骨架Ti的形成提高了TiO₂@SiO₂的催化性能.     

铋掺杂二氧化钛纳米颗粒的制备及其可见光催化性能

采用水热法,以纳米管钛酸为前驱物制备了Bi掺杂的TiO₂,并利用X射线衍射、透射电子显微镜、X射线光电子能谱、紫外-可见漫反射光谱等手段对样品进行了表征. 以甲基橙的光催化降解为模型反应评价了样品的可见光催化性能. 结果表明,Bi离子并没有进入TiO₂的晶格中,而是以BiOCl的形式存在. 所制得的BiOCl/TiO₂复合物对甲基橙降解表现出较优越的可见光催化活性;当Bi/Ti摩尔比为1%,水热温度为130℃时,所制催化剂的光催化性能最佳,并对光催化活性提高的机理进行了讨论. 同时,该催化剂对4-氯苯酚降解也表现出较高的光催化性能.     

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%.     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂, 采用“浸渍-还原法”构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料, H₂O₂为氧化剂, 研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明, 在可见光照射下, 纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强TiO₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时, 苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下, Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

载有C60的TiO2纳米粒子光催化活性

以水溶性C₆₀和TiO₂粒子为前驱体,采用水热法制备了载有C₆₀的锐钛矿型TiO₂纳米粒子。应用X射线衍射、透射电子显微镜、红外光谱、紫外-可见漫反射光谱、荧光光谱对产物进行了表征。以对-硝基苯酚为模型污染物研究了产物的光催化活性,结果表明适量负载C₆₀可以提高TiO₂纳米粒子的光催化活性,C₆₀起着传输电子、促进TiO₂光生载流子分离的作用,且经7次循环使用后对-硝基苯酚的降解效率仍能达到74%。讨论了载有C₆₀的TiO₂纳米粒子光催化降解对-硝基苯酚的机理。     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂,采用"浸渍-还原法"构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料,H₂O₂为氧化剂,研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明,在可见光照射下,纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强Ti₀₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时,苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下,Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

高活性Au/SnO2催化剂的制备及其在1,4-丁二醇氧化制γ-丁内酯反应中的催化应用

采用沉积沉淀法制备了一系列商业SnO₂负载的纳米Au催化剂, 通过电感耦合等离子体发射光谱、X射线粉末衍射、透射电镜和X射线光电子能谱等方法研究了溶液酸碱性、沉淀剂种类、Au负载量和焙烧温度等对催化剂性质的影响.结果表明, Au的负载量以及催化剂的焙烧温度对Au颗粒状态有较大影响.其中, 于573 K焙烧的3%Au/SnO₂催化剂在1,4-丁二醇氧化制备γ-丁内酯反应中的催化活性最好, TOF值是Au/TiO₂催化剂的15倍.这主要是由于SnO₂载体独特的性质对所负载的Au颗粒的影响.     

不同pH值制备的TiO2和TiO2/SiO2催化剂结构、表面性质及光催化活性

以TiOSO₄和SiO₂溶胶为原料, 采用沉淀法用氨水调节pH值制备TiO₂和TiO₂/SiO₂催化剂. 制备的催化剂用X射线衍射(XRD), 扫描电镜(SEM), N₂吸附(BET), 紫外-可见(UV-Vis)漫反射光谱, 程序升温脱附(NH₃-TPD), 傅里叶变换红外(FT-IR)光谱技术分析. XRD谱图显示纯TiO₂中锐钛型和金红石相共存, 且金红石相含量随pH值升高而增加. 但是, TiO₂/SiO₂催化剂只有锐钛型. 扫描电镜发现制备的催化剂呈类球形, 颗粒间相互交叠, 粒径在10-25 nm之间. TiO₂和TiO₂/SiO₂光催化剂的比表面积随pH值升高略有增大. SiO₂的添加会增大催化剂的比表面积. 程序升温脱附实验结果说明催化剂的表面酸量随pH值升高而增加. TiO₂/SiO₂的表面酸量比相同pH值制备的TiO₂大. 红外光谱分析说明Si掺杂和高pH值有利于催化剂表面生成更多的羟基. TiO₂和TiO₂/SiO₂光催化剂的催化活性随pH值升高而明显增强. TiO₂/SiO₂的光催化活性优于TiO₂. TiO₂/SiO₂催化剂具有较好的耐久性.     

花状TiO2分级结构的可控合成与其光催化性能

采用水热法可控合成了花状TiO₂分级结构材料,运用扫描电镜、透射电镜、X射线衍射、N₂物理吸附-脱附等手段,对其进行了表征,系统研究了NaOH用量、H₂O₂浓度、HNO₃浓度、反应温度及时间等因素对所得样品形貌的影响,并评价了它们的光催化性能.结果表明,花状TiO₂分级结构为锐钛矿相,颗粒大小均一;随制备条件的变化,构成花状TiO₂分级结构的基元结构分别为纳米线、纳米片,纳米线直径约25nm,纳米片厚度不足10nm;该样品具有较高的比表面积,表现出良好的单次光催化活性与重复使用性能.     

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.     

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.     

Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯酯交换反应的研究

ZnO、La₂O₃和Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯反应制备碳酸二甲酯和乙二醇。催化剂采用共沉淀法进行制备,并用BET、XRD、TG-DSC、CO₂-TPD和Hammett滴定等对催化剂进行表征。考察了Zn-La物质的量比、焙烧温度,反应条件（反应温度、反应时间、催化剂用量等）对催化剂活性的影响。结果表明,ZnLa复合氧化物物质的量比为2：1,焙烧温度为500℃时,催化剂表现了较好的催化效果。催化剂的活性与催化剂表面的碱性强度和碱量有关,碱量越多催化剂的活性越好。     

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.     

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     

High-power ultrasonic-assisted phenol and dye degradation on porous manganese oxide doped titanium dioxide catalysts

In this study, a high-power ultrasonicator (600 W) is employed to examine dye degradation and phenol decomposition efficiencies in the presence of catalysts such as K-OMS-2, TiO₂, K-OL-1 doped TiO₂ and K-OMS-2 doped TiO₂. Methylene blue and phenol are chosen as the model pollutants to test the catalytic activity. Effects of ultrasonic power level or ultrasonic intensity, amount of catalysts used and ultrasonic irradiation time for catalytic degradation and removal of phenol were studied. No d-spacing peak shift was observed in intense XRD peaks of K-OMS-2- and K-OL-1-doped TiO₂ materials when compared with commercial TiO₂. Scanning and transmission electron micrographs (SEM and TEM) show aggregated particle morphology with spherical and rectangular particles for 5 wt % K-OMS-2/TiO₂. Methylene blue dye degradation efficiency in the presence of catalytic ultrasonication follows the order like TiO₂ > 5 wt % K-OMS-2/TiO₂ > 5 wt % K-OL-1/TiO₂. The K-OMS-2- and 5 wt % K-OMS-2-doped TiO₂ catalyst showed the best and most promising efficiency for phenol removal in ultrasonication process. K-OMS-2 shows the best phenol removal efficiency of 58% within a short duration (30 min) of catalytic ultrasonic-assisted reaction.     

负载Ni催化剂用于乙二醇蒸汽重整制氢催化性能研究

采用等体积浸渍法和共沉淀法制备了Ni催化剂,在固定床反应器上考察了Ni负载量、焙烧温度、反应温度等因素对乙二醇低温重整制氢反应活性和选择性的影响。应用X射线衍射、氮物理吸附、H₂程序升温还原等技术对负载型Ni催化剂进行了表征。结果表明,共沉淀法制备的Ni/CeO₂催化剂具有较小的NiO颗粒与CeO₂载体颗粒粒径,催化活性较高。添加少量氧化钴到Ni/CeO₂催化剂中可使H₂收率达72.6%,EG转化率达93.1%。在CeO₂中添加Al₂O₃能提高负载Ni催化剂的活性,乙二醇转化率达94.0%,H₂收率达67.0%;但添加SiO₂则使其活性明显变差。