Hydrothermal Reaction Mechanism and Pathway for the Formation of K2Ti6O13 Nanowires

Calculations and detailed first principle and thermodynamic analyses have been performed to understand the formation mechanism of K₂Ti₆O₁₃ nanowires (NWs) by a hydrothermal reaction between bulk Na₂Ti₃O₇ crystals and a KOH solution. It is found that direct ion exchange between K⁺ and Na⁺ plus H⁺ interactions with [TiO₆] octahedra in Na₂Ti₃O₇ promote the formation of an intermediate H₂K₂Ti₆O₁₄ phase. The large lattice mismatch between this intermediate phase and the bulk Na₂Ti₃O₇ structure, and the large energy reduction associated with the formation of this intermediate phase, drive the splitting of the bulk crystal into H₂K₂Ti₆O₁₄ NWs. However, these NWs are not stable because of large [TiO₆] octahedra distortion and are subject to a dehydration process, which results in uniform K₂Ti₆O₁₃ NWs with narrowly distributed diameters of around 10 nm.     

Geochemical characteristics of the Yufuin outflow plume, Beppu hydrothermal system, Japan

Thermal water at Yufuin (Kyushu Island, Japan) is tapped through about 820 shallow wells and used mainly for hot-spring bathing purposes. Chemical and isotopic data for fluids from wells and fumaroles in Yufuin and Beppu indicate that the thermal activity at Yufuin represents a dilute, westward-flowing hydrothermal outflow plume from the Beppu hydrothermal system. Two other (eastward-flowing) outflow plumes have long been recognized at Beppu, but the Yufuin outflow plume is first recognized here. The Yufuin outflow plume is apparently a mixture of two end-member fluids: (1) deep high-temperature (250–300°C) fluid from the Beppu system having high chloride concentration (1400–1600 mg/L) and a δ¹⁸O value near −6.0%, and (2) meteoric water having low chloride concentration (≤7 mg/L) and a δ¹⁸O value near −9.2%.A permeable conduit for the vertical and lateral transport of deep fluid from the Beppu system is provided by the Yufuin Fault zone, which extends westward from the southern flank of Mt. Tsurumi volcano to the town of Yufuin. Stable isotope ratios and chloride concentrations for shallow groundwaters near the eastern end of the fault, at an elevation near 700 m, are consistent with those required for the low-chloride meteoric end-member of the Yufuin thermal waters. Recharge of this meteoric water, as well as mixing with the Beppu deep fluid, may occur along the Yufuin Fault. Enthalpy-chloride relations indicate additional conductive heating of the Yufuin waters, in the amount of 350–500 kJ/kg beyond that which can be accounted for by mixing between Beppu deep fluid and meteoric water. This could be a result of conductive heating with convection to a depth of 1–2 km. Estimates of the magnitude of the heat source for the Beppu hydrothermal system should take into account the heat being discharged at Yufuin.     

Bi3+对纳米MnO2水热合成的影响研究

在中性和酸性条件下，以MnO2作为锰源，通过水热合成了纳米MnO2，通过XRD和TEM对产物进行的观察表明，在酸性条件下，向溶液中添加一定量的Bi^3 ，产物的晶型由α型向γ型转化，产物形貌由针状、丝状向颗粒状转变。     

Hydrothermal Synthesis of Acicular Lead Titanate Fine Powders

A pure, acicular lead titanate (PbTiO₃) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO₃ with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm⁻³. The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO₃ under hydrothermal conditions have been investigated. The acicular PbTiO₃ with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO₃ at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO₃ are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH₂)₃CH₃]₄) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length.     

静态水热脱铝处理对HZSM-5分子筛的结构、酸性和催化性能的影响

开发了一种静态水热脱铝的方法。HZSM-5经此法处理后,正戊烷的裂解活性增加,脱氢和芳构化性能加强。可用改变处理温度的方法来控制脱铝的程度。用XRD和吡啶吸附红外技术进行了研究。HZSM-5分子筛催化剂性能的变化用非骨架铝产生的强L酸中心来解释。     

3961连续重整催化剂性能考察

新一代高活性，高水热稳定性3961（PS－Ⅳ）型连续重整催化剂于1996年在上海石化芳烃厂400kt/a连续重整装置上首次进行工业应用试验。开工5a，催化剂跟踪分析结果表明，该剂保持了良好的物化性质和反应性能，表现为良好的比表面积稳定性和持氯能力，经过200个以上再生周期的催化剂未发现有明显的相变和金属分散度的变化。     

Direct synthesis and catalytic performance of ultralarge pore GaSBA-15 mesoporous molecular sieves with high gallium content

Mesoporous GaSBA-15 molecular sieves with different n_Si/n_Ga ratios have been directly synthesized using Pluronic 123 triblock polymer as a structure-directing agent by pH-adjusting method. The mesoporous materials have been characterized using ICP-AES, XRD, N₂ adsorption, ⁷¹Ga-MAS NMR, SEM and TEM. ICP-AES studies show a high amount of gallium incorporation on the silica pore walls. The structural and textural properties of calcined GaSBA-15 are characterized by XRD and N₂ adsorption. ⁷¹Ga MAS NMR results demonstrate that a high amount of tetrahedral-gallium could be substituted for Si in the framework of SBA-15. TEM and FE-SEM images show the uniform pore diameter and rope-like hexagonal mesoporous structure of GaSBA-15. These GaSBA-15 materials have been used as catalysts for vapour-phase t-butylation of 1,2-dihydroxybenzene (DHB) for selective synthesis of 4-t-butylcatechol (4-TBC) under different reaction conditions. GaSBA-15(10) gave the highest 93.2% conversion of DHB and 95.7% selectivity of 4-TBC as compared with other GaSBA-15 catalysts.     

Preparation and electrochemical performance of nanosized Co3O4 via hydrothermal method

The hydrotalcite-type cobalt compounds were prepared through oxidation of Co（OH）2 gel using NH4OH as precipitating agent and H2O2 as oxidant. These hydrotalcite-type cobalt compounds were transformed into Co3O4 through hydrothermal decomposition with nanostructural deformation. The precursor and product were characterized by Fourier-transform infrared（FT-IR） spectrum, X-ray diffractometry（XRD） and transmission electron microscopy（TEM）. The electrochemical performances of as-prepared nanosized Co3O4 as anode materials in lithium-ion batteries were tested by charge-discharge test in the voltage range of 0-3.0 V. The influence of morphology of Co3O4 particle on the capacity and cycling performance was studied. The results show that the shape and size of the final product can be controlled by altering cobalt sources. The irregular cubic Co3O4 with the average particle size of about 10 nm shows the best electrochemical performance. After 10 charge-discharge cycles, the specific charge capacity retains 555 mA.h/g.     

水热法制备氧化锆微粉的进展

二氧化锆纳米粉是制造高科技陶瓷的重要原料，水热法是目前生产纳米粉体最具发展潜力的工艺方法之一。综述了水热法（包括水热沉淀、水热氧化、水热电埋弧、微波水热等）在生产纳米二氧化锆系粉体中的应用，以及水热法的发展情况。     

焙烧法水热合成5A沸石分子筛

焙烧活化化工原料氢氧化钙、氢氧化钠、硅酸钠和二氧化硅，探索焙烧法水热合成5A沸石分子筛的条件。并通过X射线粉末衍射(XPS)和扫描电镜(SEM)对产品进行表征。焙烧原料合成5A沸石分子筛的优化条件为焙烧温度550 ℃, 焙烧时间4 h, 晶化时间4 h。