Investigation on Three-Dimensional Solubility Parameters for Explanation and Prediction of Swelling Degree of Polydimethylsiloxane Pervaporation Membranes

Using polydimethylsiloxane (PDMS) as a basic matrix to prepare ethanol and butanol permselective pervaporation membranes is a vibrant field. Many studies have verified that the three-dimensional Hansen solubility parameters (HSP) theory offers a valid explanation for the swelling performance of ethanol and butanol in PDMS. Five parameters (δ_D, δ_P, δ_H, δ_t, and R_a) are defined in HSP theory which can be individually used to explain the interaction strength between a solvent and a polymer. However, for the above five parameters, which one is the most effective parameter for deciding the swelling degree still needs to be determined. In this study, a commonly used hydroxy-terminated PDMS precursor was adopted to prepare the PDMS network. The HSP of the chosen PDMS precursor was measured by an advanced “solubility-rating” method. The special software package HSPiP (4.1.03), purchased from the HSPiP team, was used to process the “solubility-rating” results. The equilibrium swelling degree (Q value) of the PDMS network in water, ethanol, butanol, and toluene was measured and the relationships between the five HSP parameters of the solvents and the logarithmic equilibrium swelling degree, log(Q), were discussed. It was found that the measured polar parameter, δ_P, of PDMS was 0.12 MPa^0.5. The measured hydrogen bonding parameter, δ_H, was larger than δ_P, attaining a value of 8.6 MPa^0.5, because the hydroxy groups directly contributed to the hydrogen bonding solubility parameter, δ_H. With respect to the relationships between log(Q) and δ_D, δ_P, δ_H, δ_t, and R_a, linear relationships existed after plotting log(Q) vs. δ_P and log(Q) vs. δ_H. The linear relation degree of the fitted lines was 0.995 and 0.989, respectively. Their standard deviations were 0.149 and 0.232, respectively. Therefore, a better linear relationship existed between log(Q) and δ_P than the other solubility parameters. This indicated that the polar interaction was the main effect for deciding the swelling degree of the PDMS network in water and alcohol systems.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.     

高活性铜催化剂无受体乙醇催化脱氢制乙醛研究

相较于Wacker工艺进行乙醛工业化生产,发展多相催化体系实现乙醇直接无氧催化脱氢制乙醛和副产氢气,从生产工艺和经济价值方面无疑是一条更加安全高效的路线.在此,我们发展了一种高效、稳固的Cu/SiO₂催化剂,用于乙醇的无受体催化脱氢.通过氨蒸发法制备得到高度分散的Cu颗粒,在没有任何平衡气体的纯乙醇进料条件下,显示出超强的热稳定性.活性组分Cu和载体SiO₂之间的强相互作用,使其具有优异的催化性能.通过反应条件优化,在250℃下实现了较高的乙醇转化率(>40%)和乙醛选择性(>95%),且催化剂在固定床连续反应过程中可稳定运行超过400 h.     

通过"双离子键"固载于季鏻盐聚合物的[Rh(CO)I3]2–物种在多相乙醇羰基化中的应用

贵金属物种(Rh或Ir络合物)在均相羰基化和氢甲酰化催化过程得到了广泛的应用,但始终存在分离繁琐等问题,其均相多相化可很大程度上简化分离操作,故一直广受重视.单位点催化剂因其具有可与均相相比拟的较高金属利用率和选择性而成为均相多相化的重要研究方向之一.研究发现,在碘物种存在的情况下用于固载金属物种的配位键容易断裂,进而导致金属物种的流失,而通过离子键固载的[Rh(CO)₂I₂]^–物种更加稳定,比如著名的甲醇羰基化“Acetica^TM”工艺中,[Rh(CO)₂I₂]^–负一价阴离子物种是以离子键的方式固定在带有阳离子骨架的甲基化聚乙烯吡啶树脂上.与甲醇羰基化过程类似的乙醇羰基化过程是生产重要化工中间体丙酸的主要途径之一,但该过程的均相多相化始终存在着稳定性差这一关键问题.为了解决这一问题,基于之前将固载于季鏻盐聚合物的[Rh(CO)I₃]^2–应用于甲醇羰基化的工作,我们将类似的季鏻盐聚合物固载Rh基催化剂Rh-TPISP用于多相乙醇羰基化过程,通过多种表征进一步证明了Rh物种和P物种结构,并提出了“双离子键”模型.P的K边XANES证明了聚合物TPISP的季鏻化阳离子骨架特征.HAADF-STEM测试表明Rh-TPISP中的Rh呈现单位点分散的状态.Rh的XPS和XANES结果证明了Rh-TPISP中Rh物种的价态介于0~+1.通过EXAFS的拟合解析给出了[Rh(CO)I₃]^2–活性中心结构.由于[Rh(CO)₂I₂]^–为经典的羰基化活性中心,为了进一步证明该结构的正确性,我们将Rh-TPISP的EXAFS和IR谱图与标样[PPh3Et]⁺[Rh(CO)₂I₂]^–对比发现:在EXAFS谱图中,Rh-TPISP中的Rh-C峰高低于[PPh3Et]+[Rh(CO)₂I₂]^–的Rh-C峰高,而Rh-TPISP中的Rh-I峰高高于[PPh3Et]+[Rh(CO)₂I₂]^–的Rh-I峰高,这就说明Rh-TPISP中Rh物种的Rh-C配位数小于2,而Rh-I配位数大于2;在IR谱图中,标样[PPh3Et]+[Rh(CO)₂I₂]^–中有两个羰基振动峰,与该物种的两个Rh-C配位键相符,而Rh-TPISP中的只有一个羰基振动峰,说明Rh-C配位数为1.因此,Rh-TPISP催化剂的季鏻盐骨架中的每个P物种带有一个正电荷,每个带有两个负电荷的[Rh(CO)I₃]^2–通过与两个[P]⁺的静电作用进行固载,形成“双离子键”结构.该催化剂在固定床乙醇羰基化过程中表现出优异的羰基化活性、选择性和稳定性.在3.5 MPa、195 oC反应近1000 h后,Rh-TPISP催化剂TOF保持在约350 h–1,丙酰基选择性为95%以上,高出所有文献报道的均相和多相乙醇羰基化活性.其较高的活性主要是因为[Rh(CO)I₃]^2–比传统Rh活性相[Rh(CO)₂I₂]^–具有更强的富电子性,而较高的稳定性主要是由于“双离子键”这种强静电作用比“AceticaTM”工艺中“单离子键”更有利于Rh物种的固载.故Rh-TPISP催化剂中的“双离子键”对其优异的催化性能具有极其重要的作用,对后续多相乙醇羰基化的发展具有重要意义.     

Efficient Synthesis of p-Hydroxyphenyl Ethanol from Hydrogenation of Methyl p-Hydroxyphenylacetate with CNTs-promoted Cu-Zr Catalyst

Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol. The reaction was catalyzed by Cu_iZr_j-x%(mass fraction) carbon nanotubes(CNTs) catalysts. Incorporation of a minor amount of CNTs into Cu_iZr_j oxide can visibly increase the catalytic activity for the synthesis of p-hydroxyphenyl ethanol. The yield of p-hydroxyphenyl ethanol reaches 94.2% over a co-precipitated catalyst of Cu₃Zr₁ oxide with 11.0%CNTs. Its catalytic activity shows no obvious decrease after three cycles. This is much better than the CNT-free co-precipitated catalyst with a good yield of 81.1%, Cu₃Zr₁-0%CNTs.     

Enhanced ethanol sensing properties of WO3 modified TiO2 nanorods

Pristine and WO₃ decorated TiO₂ nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO₂ NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO₂ NRs and thermally oxidised to obtain WO₃ nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO₂ NRs with WO₃.     

Design and Synthesis of New Withaferin A Inspired Hedgehog Pathway Inhibitors

Withanolides constitute a well-known family of plant-based alkaloids characterised by widespread biological properties, including the ability of interfering with Hedgehog (Hh) signalling pathway. Following our interest in natural products and in anticancer compounds, we report here the synthesis of a new class of Hh signalling pathway inhibitors, inspired by withaferin A, the first isolated member of withanolides. The decoration of our scaffolds was rationally supported by in silico studies, while functional evaluation revealed promising candidates, confirming once again the importance of natural products as inspiration source for the discovery of novel bioactive compounds. A stereoselective approach, based on Brown chemistry, allowed the obtainment and the functional evaluation of the enantiopure hit compounds.     

辛弗林衍生物的合成

以苯甲醚为起始原料,与乙酰氯发生付-克酰基化后脱甲基得到4-羟基苯乙酮,然后与液溴进行α-溴代得到2-溴-1-(4-羟苯基)乙酮,再与叔丁胺进行胺化得到1-(4-羟基苯基)-2-(叔丁基氨基)乙酮,最后用氢硼化钠还原合成目标产物1-(4-羟基苯基)-2-(叔丁基氨基)乙醇,总收率约为42.3%。     

NaBF4催化合成二吲哚甲烷类化合物

在乙醇水溶液中,以Na BF4为催化剂,通过吲哚与芳香醛间的串联反应合成了二吲哚甲烷衍生物。考察了催化剂种类、反应介质、温度、反应时间等因素对反应的影响,在优化条件下以较高产率得到了一系列目标产物。     

炭黑负载Pt-Sn双金属催化剂对乙醇的电催化氧化性能

采用一步还原法(乙二醇为还原剂)与两步还原法(在聚乙烯吡咯烷酮PVP保护下,先用硼氢化钠还原制备Sn溶胶,沉积Pt后用乙二醇还原)制备了炭黑负载Pt-Sn双金属催化剂,利用循环伏安法和计时电流法考察了催化剂制备方法、Pt/Sn原子比、溶液p H值、PVP/Sn质量比、反应介质等对乙醇室温电催化氧化活性和稳定性的影响.以X光衍射、透射电镜及电化学活性面积测定对所得催化剂进行了表征.发现引入Sn明显提高了Pt催化剂对乙醇的电催化活性与稳定性,两步还原法得到的Pt3Sn/C催化剂具有更小的颗粒尺寸,更大的电化学活性面积及更高的乙醇氧化活性与稳定性.与酸性介质相比,该催化剂在碱性介质中的电化学活性更好.