A new plastic scintillation resin for single-step separation,concentration and measurement of technetium-99

Technetium is a synthetic element with no stable isotopes, produced as waste in nuclear power plants and in cyclotrons used for nuclear medicine. The element has high mobility, in the form of TcO₄⁻; its determination is therefore important for environmental protection. Technetium is found in low concentrations and therefore common methods for its analysis include long treatments in several steps and require large amounts of reagents for its purification and preconcentration. Plastic scintillation resins (PSresin) are novel materials used to separate, preconcentrate and measure radionuclides in a single step. The objective of this study is to prepare and characterise a PSresin for the preconcentration and measurement of ⁹⁹Tc. The study first evaluates the reproducibility of the production of PSresins between batches and over time; showing good reproducibility and storage stability. Next, we studied the effect of some common non-radioactive interferences, showing small influences on measurement, and radioactive interferences (³⁶Cl and ²³⁸U/²³⁴U). ³⁶Cl can be removed by a simple treatment with 0.5 M HCl and ²³⁸U/²³⁴U can be removed from the column by cleaning with a mixture of 0.1 M HNO₃ and 0.1 M HF. In the latter case, a slight change in the morphology of the PSresin caused an increase in detection efficiency. Finally, the PSresin was applied to the measurement of real spiked samples (sea water and urine) with deviations lower than 10% in all cases.     

Mn-Al和Cu-Mn-Al复合氧化物催化苯甲醇选择氧化反应

用溶胶-凝胶法制备了不同组成的Mn-Al和Cu-Mn-Al复合氧化物两组催化剂,用于苯甲醇选择氧化反应.用X射线衍射(XRD)、N2物理吸附(BET)、扫描电镜(SEM)、H_2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-TPD)和X射线光电子能谱(XPS)技术对催化剂进行了结构表征,考察了催化剂组成对催化活性的影响.结果表明:以甲苯为溶剂,O_2为氧化剂,353 K反应5 h,Mn_2Al和Cu_(0.3)Mn_(0.7)Al_2催化剂上的苯甲醇转化率分别为36.6%和40.9%,苯甲醛选择性均为100%.进一步研究表明:催化剂活性与其H2还原性和O_2吸附性有关,高活性的催化剂吸附氧多,生成的活性氧易参与反应.     

Inclusion properties of 3-fluoromesotetraphenylporphyrin with C60 and C70

To improve the selectivity ratio of C70 over C60, a new designer molecule, viz., 3-fluoromesotetraphenylporphyrin (1) has been reported in the present investigations. Fluorescence studies reveal that the Q-absorption band of 1 gets sufficient quenching effect upon addition of both C60 and C70. Binding constants (K) of the C60/1 and C70/1 complexes are estimated to be 580 and 10,800 dm3 mol(-1), respectively. Thus, K(C70)/K(C60) is approximately 19 which is very large and even comparable with other macrocyclic host molecules like calix[5]arene, azacalix[m]arene[n]pyridine, cyclotriveratrylenophane and calixarene bisporphyrin. 1H NMR chemical shift measurements show that the -NH- proton of 1 suffers more shifts in presence of C70 compared to C60. This finding also offers a good support in favor of high K value for C70/1 complex as well as large selectivity ratio of C70 over C60.     

Potentiometric evaluation of calix[4]arene anion receptors in membrane electrodes: phosphate detection

Ion-selective membrane electrodes doped with the urea- or thiourea-functionalised calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-N′-(phenylureido)butyl]oxy]-26,28-dipropoxy calix[4]arene (I) and 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-(N′-phenylthioureido)-butyl]oxy]-26,28-dipropoxy calix[4]arene (II), were evaluated for anion sensing. Potentiometric results show that these calixarene ionophore-based membrane electrodes exhibit a good sensitivity to aqueous solutions of the monohydrogen orthophosphate species HPO₄²⁻ in the concentration range 5.0 × 10⁻⁵ to 1.0 × 10⁻¹ M, with near-Nernstian response slopes of −33.0 and −28.0 mV dec⁻¹ for ionophores I and II, respectively. Selectivity coefficient values for monohydrogen orthophosphate over a range of common anions were determined by the fixed interference and matched potential methods and indicated that these membrane electrodes exhibit a good selectivity for HPO₄²⁻ with respect to the other anions, including sulfate and nitrate.     

Rhodium-catalyzed intermolecular hydroacylation of 1-alkynes: Effect of phosphines and MK-10 on the reaction selectivity

The use of bulky ligands in the rhodium-catalyzed reaction of aldehydes 7 (R¹ = Ph) and 18 with 1-octyne increased the selectivity for ketones 13 and 20, to the detriment of ketones 12 and 19. Bulky phosphines reduced the hydroacylation reaction rate, leading to competition from the addition of the benzoic acid co-catalyst to the alkynes. This competing reaction can be suppressed by using the clay Montmorillonite K 10 (MK-10) as the co-catalyst instead of benzoic acid.     

多级孔HZSM-5分子筛催化剂的制备及低碳烃芳构化应用

采用0.2 mol/L的NaOH溶液对HZSM-5分子筛进行了不同时间的碱改性处理, 并对分子筛的结构和酸性进行表征, 考察了碱改性对HZSM-5催化剂的低碳烃芳构化活性的影响. 结果表明, HZSM-5分子筛经碱改性后会产生少量介孔, 且随改性时间延长, 介孔数量增加, 平均孔径增大, 总酸量降低, B酸/L酸比值降低. 120 min碱改性HZSM-5催化剂的活性、 稳定性以及目标产物苯、 甲苯、 乙苯和二甲苯(统称BTEX)的选择性最高.     

硅胶键合膦的制备及其对铑络合物催化1-辛烯氢甲酰化反应的影响

以硅胶为载体, 采用键合接枝法将2-(二苯膦基)乙基三乙氧基硅烷(DPPES)共价键合于硅胶表面, 制备了性能优良的硅胶键合型膦配体(以SiO₂(PPh₂)表示). 以SiO₂(PPh₂)为配体, Rh(acac)(CO)₂ (acac:乙酰丙酮)为催化前体, 负载铑膦络合物催化剂(SiO₂(PPh₂)/Rh)在1-辛烯氢甲酰化反应中原位生成. 对生成的负载型催化剂和硅胶键合型膦配体进行了傅里叶变换红外(FTIR)光谱表征, 考察了膦/铑摩尔浓度比([P]/[Rh])、温度等因素对铑催化的长链1-辛烯氢甲酰化反应的影响. 结果表明, 膦/铑摩尔浓度比的增加能显著提高反应的成醛选择性, 降低铑的流失. 在[P]/[Rh]=12、363 K、2.0 MPa、1.5 h 的温和反应条件下, 1-辛烯转化率和成醛选择性分别可达98.4%和95.3%, 其催化活性与DPPES或三苯基膦(TPP)作配体时的均相铑催化相近. 催化剂循环4 次后, 反应活性无明显下降, 1-辛烯转化率均在97.0%左右, 经电感耦合等离子体原子发射光谱(ICP-AES)检测,有机相中铑流失低于0.1%.     

芳香噻嗪类衍生物作为选择性醛糖还原酶抑制剂的分子对接和基于受体的三维定量构效关系研究

芳香噻嗪类衍生物被证明是一类选择性较好的高活性醛糖还原酶抑制剂(ARIs).本文对44个芳香噻嗪类化合物进行了分子对接(docking)和三维定量构效关系(3D-QSAR)研究,并探索了此类化合物与醛糖还原酶(ALr²)的作用机理.醛糖还原酶与醛还原酶(ALR1)活性位点的叠加结果显示, ALr²中残基Leu 300和Cys298的存在是化合物1m具有高选择性的原因.分别建立了比较分子场分析方法(CoMFA, q² = 0.649, r² =0.934; q²:交叉验证相关系数, r²:非交叉验证相关系数)和比较分子相似性指数分析方法(CoMSIA, q² = 0.746, r² = 0.971)模型,并对影响此类化合物生物活性的结构进行了鉴定.结果显示,两个模型均具有较高预测能力,并通过测试集中的7个化合物进行了验证,其中CoMFA模型和CoMSIA模型的预测相关系数(r_Pred²)分别为0.748和0.828. 3D-QSAR模型中的三维等值线图表明,在化合物1m的苄基环上C3和C4位置以及苯并噻嗪母核上C5和C7位置进行改进可能对生物活性的提高有利,此预测与我们前期报道的苯并噻嗪母核C7位改进结果一致.本文所建3D-QSAR模型能够在理性设计具有更高生物活性的新型ARIs中发挥重要作用.     

Selective surface chemistry of allyl alcohol and allyl aldehyde on Si(1 0 0)2×1: Competition of [2 + 2] CC cycloaddition with O-H dissociation and with [2 + 2] CO cycloaddition in bifunctional molecules

Competition between the CC functional group with the OH group in allyl alcohol and with the CO group in allyl aldehyde in the adsorption and thermal chemistry on Si(1 0 0)2×1 has been studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD), as well as density-functional theory (DFT) calculations. The similarities found in the C 1s and O 1s spectra for both molecules indicate that the O-H dissociation product for allyl alcohol and [2 + 2] CO cycloaddition product for allyl aldehyde are preferred over the corresponding [2 + 2] CC cycloaddition products. Temperature-dependent XPS and TPD studies further show that thermal evolution of these molecules gives rise to the formation of ethylene, acetylene, and propene on Si(1 0 0)2×1, with additional CO evolution only from allyl alcohol. The formation of these desorption products also supports that the [2 + 2] CC cycloaddition reaction does not occur. In addition, the formation of SiC at 1090 K is observed for both allyl alcohol and allyl aldehyde. We propose plausible surface-mediated reaction pathways for the formation of these thermal evolution products. The present work illustrates the crucial role of the Si(1 0 0)2×1 surface in selective reactions of the Si dimers with the O−H group in allyl alcohol and with the CO group in allyl aldehyde over the CC functional group common to both molecules.     

Production of valuable hydrocarbons by catalytic degradation of a mixture of post-consumer plastic waste in a fluidized-bed reactor

A mixture of post-consumer plastic waste (PE/PP/PS/PVC) was pyrolyzed over various catalysts using a fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic and mechanistic schemes for the observed products associated with chemical reactions and catalyst deactivation has been developed. The model gives a good representation of experimental results. It is also an improvement on the currently available empirical “lumping” techniques which are usually severely restricted in terms of product definitions. Additionally, this model represents the benefits of product selectivity for the chemical composition in relation to the effect of structurally different catalyst types, and the performance of the reaction temperature used as well as the particle size of the catalyst selected.