Synthesis of Ga-incorporated SAPO-34s (GaAPSO-34) and their catalytic performance on methanol conversion

This study has been focused on the synthesis of GaAPSO-34s substituted gallium for aluminum in order to improve the acidic property in SAPO-34 crystal. As the result, GaAPSO-34s with various Al/Ga ratios (Al/Ga=∞, 40, 20, 10, 5, and 0) were successfully synthesized. These were characterized by XRD, SEM, ICP, TG-DTA, MAS-NMR, and BET surface areas. The crystallinity identified from the intensity of XRD peak (for angles of 22.5° and 9.7°) and the particle size observed from SEM photographs decreased with an increase in the Ga content incorporated into the SAPO-34 framework. On the other hand, decrease in the acid sites in crystal as a target in this study was confirmed in the Ga-incorporated samples. In particular, a surprising result was that the selectivity to ethylene on methanol conversion increased in catalyst with Al/Ga=20 compared with pure SAPO-34 catalyst. However, in spite of the decreases in acid sites and particle size in catalyst with much more Ga content, the selectivity to ethylene was not enhanced, rather the methane which related to catalytic deactivation increased in GaAPSO-34 catalysts. This is ascribed to collapses of framework of SAPO-34 with an increase in Ga content.     

电感耦合等离子体质谱(ICP-MS)法测定离子吸附型稀土矿中的浸出稀土元素

对浙江某地大量的离子吸附型稀土样品进行了稀土元素(Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu)的浸提和测定实验,实验对比了氯化铵和硫酸铵溶液对矿石中稀土元素的浸出性能,选择了杂质浸出较少的硫酸铵溶液作为浸出剂,对不同稀土含量的吸附型稀土矿进行了实验,浸出方法稳定,符合工业开采要求。实验了电感耦合等离子体质谱法测定浸出液中稀土元素分量的方法,浸出液经大比例稀释并酸化后测定,精密度较好,能满足离子吸附型稀土矿评价的质量要求,方法检出限(6σ)0.005~0.26μg/g,单元素测定精密度(n=6,RSD≤6.0%),浸出稀土元素总量测定RSD≤4.0%。实际样品的实验及测定结果满意。     

Synthesis of a chlorophyll-a derivative fused with an additional exo-five-membered ring and its optical properties

A C20-free chlorophyll-a derivative with an additional exo-five-membered ring was successfully prepared using an ethylene linkage at the C3- and C5-positions. A bromination at the C20-position was requisite for the cyclization of a 1-hydroxyethyl or vinyl group at the C3-position of methyl bacteriopheophorbide-d or methyl pyropheophorbide-a, respectively. By comparing optical properties of the cyclized product with those of its 3-ethyl uncyclized analog in a diluted dichloromethane solution, it was shown that the cyclization shifted the Q_x and B_x absorption maxima to longer wavelengths and reduced the Stokes shift.     

基于酸性离子液体填充注射器的泡腾辅助微萃取法测定果汁样品中三嗪类除草剂

开发了一种高效、 环保的基于酸性离子液体填充注射器的泡腾辅助微萃取法, 用于测定果汁样品中三嗪类除草剂. 萃取分散采用酸性离子液体[C₄mim][HSO₄], 它对三嗪类除草剂具有较高的溶解度, 其酸性可与碳酸盐反应产生二氧化碳, 从而加速萃取过程. 该实验的提取和分离步骤在注射器中完成, 整个预处理过程完全不需要任何设备辅助. 对碳酸氢钠用量、 酸性离子液体用量、 盐添加量及洗脱溶剂体积等影响萃取效率的实验条件进行了优化. 在最佳条件下, 三嗪类除草剂浓度在1~200 ng/mL范围内获得了良好的线性关系, 相关系数大于0.9984; 检出限(LOD)和定量限(LOQ)分别为0.06~0.18和0.21~0.61 ng/mL, 日间及日内精密度低于8.3%. 实验结果表明, 该方法可用于果汁样品中三嗪类除草剂的测定.     

某些酸性磷(膦)酸酯VO(Ⅱ)配合物在四氢呋喃中的氧化过程的ESR研究

本文用电子顺磁共振法对某些酸性磷(膦)酸酯VO(Ⅱ)配合物在四氢呋中的氧化过程进行了动力学研究,研究了温度、浓度和配合物性质对反应速度及反应可逆性的影响,并计算得到动力学参数-氧化反应级数,反应速度常数和反应的表观活化能。     

堆浸工艺中流动-反应-变形-传质耦合过程数值模拟及应用

基于堆浸过程中的孔隙变形,发展了一孔隙发育模型,并建立了堆浸工艺中流动-反应-变形-传质全耦合模型控制方程组,在喷淋强度不变和常水头的的情况下,给出了方程的数值解.数值结果描述了浸出过程矿堆中溶浸液饱和度的分布、溶浸剂浓度和浸出矿石浓度的分布,拟合结果表明:有用矿物浸出百分比与浸出时间之间呈3次关系,这一关系可用来预测堆浸中的有用金属的浸出回收率.     

Re‐evaluation of distillation and comparison with HNO3 leaching/solvent extraction for isolation of methylmercury compounds from sediment/soil samples

Distillation was re‐evaluated for the formation of artifacts arising from increasing naturally occurring mercury(II) concentrations, as opposed to previous identification of artifacts by spiking standard mercury(II) into samples. Naturally occurring mercury(II) concentrations lower than 2 µg g^?1 were found not to affect methylmercury (MeHg) results. However, when the natural concentrations of mercury(II) were greater than 2 µg g^?1, in contrast to standard mercury(II) spiked in samples, the MeHg concentrations measured were found to decrease (not increase) with increasing naturally occurring mercury(II) concentrations. This indicated that standard mercury(II) spiked in samples behaved differently from naturally occurring mercury(II) in the formation of MeHg artifacts during distillation. As a result, spiking standard mercury(II) into samples to identify the formation of MeHg artifacts is not adequate. It is difficult to explain why high naturally occurring mercury(II) suppresses MeHg measurements during distillation. In comparison with HNO₃ leaching/solvent extraction (and other existing techniques), distillation was found to generate results comparable for samples containing less than 2 µg g^?1 mercury(II). The HNO₃ leaching/solvent extraction showed significant advantages over other procedures, as this technique generated the highest recoveries with good precision for all samples analyzed, and the results were found to be independent of mercury(II) concentrations for both naturally occurring and spiked standard mercury(II). Thus, except for samples from high mercury‐contaminated fields, distillation is still a good choice. Both the positive bias (possibly caused by artifact formation of MeHg) and the negative bias (due to incomplete leaching, back‐adsorption, and/or decomposition of MeHg) were investigated. Geologically, physically, and chemically different samples were used for the investigation. Copyright © 2004 John Wiley & Sons, Ltd.     

Surface analysis of inhibitor films formed by imidazolines and amides on mild steel in an acidic environment

Imidazolines and amidic precursors were synthesized with good yields through an optimized process. These compounds were evaluated as corrosion inhibitors in an aqueous solution of 1.0 M HCl by gravimetric and polarization techniques. AISI 1018 carbon steel displayed a corrosion rate dependent on the molecular structure and concentration of inhibitor in the testing environment. Adsorption of inhibitors was found to follow the Langmuir's isotherm, this concept together with Gibbs’ free energy provided the basis to arrange corrosion inhibitors according to efficiency and stability. The surface analysis by AFM displayed that the damage on the metallic surface was considerably reduced in the presence of certain inhibitors. XPS determined the presence of a layer of inhibitor on the metal surface with protective properties.     

Inhibition of copper corrosion by self-assembled films of new Schiff bases and their modification with alkanethiols in aqueous medium

The inhibitive action of self-assembled films derived from two ligands Schiff bases, including N,N′-ethylen-bis (salicylidenimine) and N,N′-ortho-phenylen-bis (salicylidenimine) on copper surface has been studied by electrochemical techniques in chloride and acidic solutions. It was found that when the concentration of the inhibitors was increased the inhibition efficiency was increased, too. The results of the electrochemical studies have illustrated that the inhibition efficiency of S-o-ph-S is higher than S-E-S. Both the Schiff bases obeyed the Langmuir isotherm and thermodynamics calculations revealed that S-o-ph-S had larger adsorption constant and more negative free energy of adsorption with respect to S-E-S. When the films were modified by propanethiol and 1-dodecanethiol, the corrosion resistance of mixed films was significantly increased.