不同活化方法对天然硅铝矿物活化及分子筛合成效果的影响

选取了高岭土、累托土、蒙脱土和伊利石四种天然硅铝矿物,采用热活化、碱熔活化、亚熔盐活化及拟固相活化四种方法对上述四种矿物分别进行活化,对比了不同活化方法对天然硅铝矿物活化效果的影响。结果表明,亚熔盐活化及拟固相活化都具有良好的活化效果,而且能耗较低,明显优于热活化和碱熔活化。其中,拟固相活化由于能耗更低且更有利于实现工业操作,因此,是最具发展前景的天然硅铝矿物活化方法。对比四种天然硅铝矿物,高岭土、累托土及蒙脱土的晶相结构更容易被解聚,而伊利石稳定性更高,经亚熔盐活化及拟固相活化后,活化产物中也只有极少量的高反应活性的硅、铝物种,因此,伊利石不是理想的分子筛合成原料。     

浓碱高苛性比铝酸钠溶液中水合铝硅酸钠形成的动力学研究

研究了浓碱高苛性比铝酸钠溶液中水合铝硅酸钠形成的动力学行为,反应对Al(OH)₄^-、SiO₂(OH)₂^2-均为一级反应.结合溶液的结构和沸石形成机理,提出了五配位中间体形成机理;提高反应温度、降低碱浓度、加强搅拌或加入晶种(或杂质)均有利于水合铝硅酸钠的形成.     

蓝紫色ZnO-Al2O3-SiO2长余辉陶瓷

通过高温固相法首次合成并报道了兰紫色ZnO-Al2O3-SiO2长余辉陶瓷，系统地研究了其发光和缺陷性质，在强度0.6mW.cm^-2，主峰254nm的UVP紫外灯下激发15min，然后关闭激发源，样品发射兰紫色长余辉，撤去激发源以后5s，余辉初始强度为230mcd.m^-1，色坐标为（0．1292，0．0984），暗视场中，8h以后余辉仍然肉眼可辨，样品的紫外可见发射和不同时间的余辉发射光谱显示，荧光发射位于390nm，来源于基质的自致发光，而余辉有两个发射峰，主峰位于390nm，肩峰位于520nm，这表明样品中存在两种余辉发射中心，由余辉衰减曲线可以看出，这两种余辉发光都由一个快过程和一个慢过程组成，其中，慢过程决定了材料的长余辉时间，从时间依赖的余辉强度倒数曲线可以看出，余辉强度与时间成反比，这表明余辉发光的机理为电子空穴复合过程，热释光谱显示，样品分别在92和250℃附近出现两个宽的热释峰，说明材料中至少存在两种具有不同陷阱深度的电子或空穴缺陷中心。     

MFI沸石前驱体和硅酸钠共组装制备水热稳定的管状介孔分子筛

在CTAB模板剂的作用下 ,硅酸钠、铝酸钠和含有MFI纳米簇的沸石前躯体溶液通过S+ I-路线共组装得到了高水热稳定的管状形貌介孔分子筛 .XRD结果显示样品具有类似MCM 41的规则排列六方孔道结构 .在沸水中处理 15 0h后 ,介孔特征仍然保留 ,显示出很好的水热稳定性 .综合SEM和TEM的观察结果 ,此介孔分子筛具有中空的管状形貌 ,平均管长2 .0 μm ,平均直径为 0 .3 0 μm .含有MFI纳米簇的沸石前躯体作为硅源的一部分加入体系中 ,MFI纳米簇伴随来自于硅酸钠的可溶性硅物种共同进入分子筛骨架 ,在提高水热稳定性的同时 ,没有降低六方纳米孔道的规整度 ,也没有对分子筛形貌调变带来不利影响 .MFI纳米簇中 ,硅氧四面体和铝氧四面体的紧密联结方式在进入分子筛骨架时得以保留是水热稳定性提高的主要原因 .作为硅源的另一部分加入的硅酸钠 ,使合成体系pH值足够高 (pH >13 ) ,加入H2 SO4调节体系pH值到10 ,管状形貌的介孔分子筛在逐步中和过程中形成 .通过这种特殊的共组装方法合成介孔分子筛 ,在获得中空的管状形貌的同时显著提高水热稳定性 ,为这种管状形貌介孔分子筛的应用奠定了基础 .     

硅酸铝短纤维增强ZL109复合材料的磨损机制

采用挤压铸造法制备了硅酸铝（Ａｌ２Ｏ３·ＳｉＯ２）短纤维增强ＺＬ１０９复合材料，并研究了该材料在干摩擦条件下的磨损行为．结果表明：Ａｌ２Ｏ３·ＳｉＯ２短纤维／ＺＬ１０９复合材料的耐磨机制为纤维断裂并在亚表层重新分布和排列形成高硬度的硬化层．这种硬化层的形成使复合材料具有比基体合金更优越的耐磨性．     

Aluminium‐27 NMR investigation of the influence of cation type on aluminosilicate solutions

The effects of tetraalkylammonium (TAA) and alkali metal cations on the equilibrium distribution of aluminosilicate oligomers in aqueous alkaline aluminosilicate solutions were investigated using ²⁷Al NMR spectra and their evolution with time. The results indicate that there are no differences in the initial equilibria involving solutions containing both TAA and alkali metal cations on the one hand and those containing alkali metal cations only. However, re‐equilibration of the aluminosilicate species for TAA/Na aluminosilicates is slow (usually not detectable on the time‐scale of the experiments), whereas when purely alkali metal cations are used, the spectra alter over a period of ～1 h, such that resolution is degraded substantially. In the latter case, it is suggested that the anions aggregate into larger systems, although the solutions are still clear. ²⁹Si NMR evidence for slow equilibration of silicate and aluminosilicate solutions at higher concentrations is also discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Green chemical conversion of large-scale aluminosilicates into zeolites for environmental remediation under carbon-neutral pressure

This minireview summarized the recent progress of converting the typical classes of large-scale aluminosilicates into zeolite materials for environmental remediation. The representative zeolite structures that can be directly converted from large-scale aluminosilicates via green chemistry approaches are addressed. The environmental remediation mechanisms on employing these zeolites for environmental remediation have been recapped. The present research gap and future research perspectives under carbon-neutral pressure via green chemistry principle on this topic are also discussed.     

高温下煤中矿物质对气化反应的影响

利用XRD对1100℃~1500℃高温下矿物质在弱还原气氛中的变化进行考察,并利用RIR对矿物质进行半定量分析,发现随着温度的升高莫来石含量增大,而SiO₂含量下降,符合SiO₂-Al₂O₃二元相图的变化。高温下部分无定形矿物质发生熔融,主要为硅铝酸盐。在煤焦二氧化碳气化过程中,熔融的硅铝酸盐与煤焦表面接触阻碍气化反应进行。利用FT-IR测定了硅铝酸盐结构的变化,说明高温下矿物质对气化反应的影响与硅铝酸盐的聚合程度存在一定的关系。     

Behavior of surface-active substances in aqueous solution and on solid surfaces

The interactions of cationic (CSA), anionic (ASA), and nonionic surfactants (NSA) with each other in aqueous solution and on solid surfaces are studied. To establish the mechanism of the adsorption of ASA and NSA from aqueous solutions onto layered silicates, modified with CSA, data on the interaction of corresponding surfactants in aqueous solutions of binary mixtures were used. It was shown that interactions between CSA and ASA led to the formation of cationic surfactants both in solution and on the surfaces of modified aluminosilicates. It was concluded that by analogy with solutions of binary mixtures of NSA on modified silicate surfaces, interaction occurs only with physically adsorbed CSA. With cations of modifier, chemically bonded to the active centers of the silicates, NSA reacts via a hydrophobic mechanism. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 3, pp. 180–184, May–June, 2009.     

Use of isoelectric point and pH to evaluate the synthesis of a nanotubular aluminosilicate

To follow the synthesis of imogolite, transmission electron microscopy is needed. In this paper, the isoelectric point (IEP) and the aging pH are proposed as alternative methods. Two synthetic procedures were used (S-I and S-II), both involving a co-precipitation followed by an aging treatment where the aluminosilicate evolves from proto-imogolite (detected after the co-precipitation step), to imogolite; its formation is reached after 120 h (S-I) or 168 h (S-II) of aging, depending on the co-precipitation method used. In S-I the isoelectric point increases from 7.1 to 10.5, while in S-II it increases from 6.6 to 9.2 during the aging treatment. Additionally, a linear relationship between the IEP and the pH at different aging steps was found. That relationship may be used to follow the process of synthesis by simply measuring the pH, becoming an alternative to more complex methods.