均匀沉淀和碳吸附耦合法制备CeO2纳米粒子及表征

均匀沉淀和碳吸附耦合法制备CeO2纳米粒子及表征;均匀沉淀;碳吸附;纳米;CeO2     

MFI分子筛前驱体对Y型沸石分子筛表面的修饰及其催化性质

间、对-甲基异丙苯是生产间、对-苯酚的反应中间体,因此其制备受到国内外广泛关注．ZSM-5,Y型,betn等沸石分子筛和掺杂zn的Al-MCM-41介孔分子筛在此反应中表现出不同的择形性．近年来利用沸石分子筛前驱体自组装技术合成的新型介孔材料已显示出优异的催化性能,     

具有纳米结构的铂电极表面的电化学制备及其性能

采用控电位方波氧化还原法和控电流方波氧化还原法分别成功地制备了控电位粗糙铂(CPRPt)和控电流粗糙铂(CCRPt)纳米级铂电极表面.通过考察两类电极表面对甲醇电催化氧化的性能,发现CPRPt和CCRPt纳米级铂电极表面催化氧化甲醇峰值电流密度分别是光滑铂电极的约1.35倍和2.50倍.采用现场拉曼光谱技术考察了两电极表面的表面增强拉曼(SERS)效应,发现两电极表面对吡啶吸附均有较高SERS活性,CPRPt电极表面还对有机小分子的解离吸附的拉曼光谱具有特殊的增强效应.本文初步探讨了两电极表面的SERS机理.     

在H型分子筛上萘与正己醇的烷基化反应

制备了H型分子筛HY,Hβ和HM,通过XRD,NH₃-TPD和Py-IR对其进行了表征,考察了其对萘与正己醇的烷基化反应的催化性质.结果表明,HY可作为己基化反应的催化剂,较高的反应温度和较长的反应时间对β-己基萘的生成有利.     

以偏钛酸为原料常压水热法合成纳米钛酸锶

以廉价的工业级偏钛酸和氯化锶为原料,用常压水热法于100℃反应6 h一步合成了纳米钛酸锶。当n(SrC l2)∶n(H3TiO3)=1.0∶1.1,pH=12时,所得钛酸锶的n(Ti)∶n(Sr)=1.02∶1.00。纳米钛酸锶经IR,XRD和TEM表征。结果显示,钛酸锶为球形粒子,属立方晶系(a=3.9200);一次粒径平均值为22 nm,粒径分布为20 nm~40 nm,无明显团聚。     

正交实验设计法研究ZSM-5催化剂的积炭量

用NaOH溶液吸收法研究了ZnNiZSM-5芳构化催化剂的积炭量,用色谱纯二氧化碳考察了此方法的准确度.用热失重法确定了烧炭的最佳温度为570℃,根据实验确定了烧炭时间为7h,空气流量为120mL/min.采用正交实验设计法对影响芳构化催化剂积炭量的温度、空速、高径比进行了研究.通过实验结果可知,积炭量最少的最佳工艺条件是温度为560℃,空速为1. 5h-1,高径比为6.1.     

XRD粉末衍射法研究微波场作用下4A分子筛的合成

在微波场作用下合成了粒度均匀、白度和钙离子交换容量高、性能优异的4A分子筛。用XRD粉末衍射法研究了硅铝比、水钠比、微波功率和微波加热时间对微波合成4A分子筛的影响,找出了在微波场作用下合成4A分子筛的最佳条件,并用IR, SEM和DSC等方法对合成的产物进行了表征。     

Ultrasound-assisted regeneration of zeolite/water adsorption pair

The use of ultrasound to enhance the regeneration of zeolite 13X for efficient utilization of thermal energy was investigated as a substitute to conventional heating methods. The effects of ultrasonic power and frequency on the desorption of water from zeolite 13X were analyzed to optimize the desorption efficiency. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant overall input power of 20 or 25 W was adopted. To measure the extent of the effectiveness of using ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no-ultrasound (heat only) at the same total power. To analyze the effect of ultrasonic frequency, identical experiments were performed at three nominal ultrasonic frequencies of ~28, 40 and 80 kHz. The experimental results showed that using ultrasound enhances the regeneration of zeolite 13X at all the aforementioned power ratios and frequencies without increasing the total input power. With regard to energy consumption, the highest energy-savings power ratio (0.25) resulted in a 24% reduction in required input energy and with an increase in ultrasonic power, i.e. an increase in acoustic-to-total power ratio, the effectiveness of applying ultrasound decreased drastically. At a power ratio of 0.2, the time required for regeneration was reduced by 23.8% compared to the heat-only process under the same experimental conditions. In terms of ultrasonic frequency, lower frequencies resulted in higher efficiency and energy savings, and it was concluded that the effect of ultrasonic radiation becomes more significant at lower ultrasonic frequencies. The observed inverse proportionality between the frequency and ultrasound-assisted desorption enhancement suggests that acoustic dissipation is not a significant mechanism to enhance mass transfer, but rather other mechanisms must be considered.     

用XRD法研究MCM-22分子筛的逐级放大合成

在100,250和1 000 mL高压釜静态成功合成MCM-22分子筛的基础上,在2,5和200 L高压釜中进行了MCM-22分子筛的动态合成试验,对合成的样品用XRD等技术进行了表征。结果表明,在静态和动态条件下合成的样品,全部为纯相MCM-22分子筛,且结晶度较高,从100 mL到200 L的放大试验是成功的。     

Revisiting the Structure of Calcined and Hydrated AlPO-11 with DFT-Based Molecular Dynamics Simulations**

Published crystal structures of the AEL-type aluminophosphate AlPO-11 in its calcined form (space group ) show some peculiar features, such as unusually short Al−O and P−O bonds and near-linear Al−O−P angles. Although experimental evidence for the presence of dynamic disorder was presented, the nature of the associated distortions remained unresolved. In this study, ab initio molecular dynamics (AIMD) calculations in the framework of density functional theory (DFT) were employed to study the dynamic behaviour of this zeotype. At 100 K, static local distortions that break the symmetry are present in the time-averaged structures computed from the AIMD trajectories. At 300 and 500 K, the time-averaged structures approach symmetry. Although shortened Al−O and P−O bonds and near-linear Al−O−P angles were found in the average structures, an analysis of radial and angular distribution functions confirmed their absence in the instantaneous structures. This deviation is due to a precession-like motion of some oxygen atoms around the Al−P connection line, which moves their time-averaged positions closer to this line. In hydrated AlPO-11, some of the water molecules are coordinated to framework Al atoms, leading to an octahedral coordination of 1/5 of the Al sites. DFT optimisations and AIMD simulations on partially hydrated models delivered evidence for a preferential adsorption at the Al1 site. No dynamic disorder was observed for the hydrated form.